# CIS fueling, frequency valve, terminal 11, etc.



## Stephen Webb (Apr 12, 2001)

There is a rather long thread on CIS fueling, but I figured it was time to start a new one.
I had a few recent posts on that thread speculating which pin to ground in order to get a higher duty cycle for the frequency valve. 
I don't have the part numbers handy now (maybe a good reason to not start a new thread, eh?), but the CIS box I am using is from an 89 Cabriolet. I believe the box is fairly common, but I don't know what it came on, etc. So, before you go trying anything with your box, confirm that it's the same as an '89 cabriolet. 
Anyway, here's the goods...
I said I would throw caution to the wind, and test my hypothesis. So, I went out and grounded pin 11 on the computer, and observed the duty cycle...Sure enough it went to 90%.
So, if you have a CIS box like mine, and you want 90% duty cycle, ground terminal 11.
Be warned, though, it's probably too much extra fuel.
-Steve


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## Peter Tong (Jun 17, 1999)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

Steve, 
Thats a nice mod...thanks for trying it. So you can set your duty cycle way low like 30% at idle, let the OXS box take care of the mixture, then plumb in a pressure switch for ultimate fuel at high boost. Sounds like a winner to me. I have switch mounted on the manifold (part of the ERL MF2 kit), and when it triggered the standard pin it was too much (stumbling, etc). 60% on the VW is not 60% on the Volvo 240t unit as fuel flow is greater. I wonder if pin 11 would make the flow equal the euro (non lambda) fuel distributors...
with best regards,
Peter T.


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Peter Tong)*

quote:[HR][/HR] I wonder if pin 11 would make the flow equal the euro (non lambda) fuel distributors...
[HR][/HR]​I remember a discussion about this a while back -- what happens when you bypass the frequency valve alltogether? I don't know if any conclusions were made, but It seems like bypassing the frequency valve would cause the system to run too rich. Maybe 90% would be a better approximation of the euro CIS setup. (Does anyone know if the euro CIS setup has the same cone shape, etc?)
FWIW: I have talked to some Volvo guys who say that the "terminal 11" trick was too much for them running moderate boost. I'm not sure when it really comes into play, but I think it's only once they exceed 12 psi, perhaps. 
Once I get a chance, I'm going to run three different fuel flow tests, all with the flap fully lifted. One with the frequency valve disconnected, one with it set to 50% (or whatever the "default" is with no O2 input), and one at 90%. I think it will be interesting to know the range of adjustment that the frequency valve provides. (I personally think it's 25% or more)
-Steve


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## gearhead455 (Oct 30, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

What if someone made a frequency valve driver box? Can't be hard (I made an injector driver in high school)... Just make inline connector to the F valve electrical connector. Have a relay that switches the frequency valve from being driven from the ECU to being driven by a homemade driver. 
In the driver, use a variable potentiometer to adjust a R/C time constant, which will in turn change the duty cycle to anything you want.


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## Butcher (Jan 31, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

The frequency valve regulates the counter pressure on top of the control piston of the fuel dist. If you hold the air flap all the way up and the control piston is all the way up, more or less pressure at the top of the control piston will not change the fuel delivery [since the piston did not change height]. I hope this makes sense.


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## Peter Tong (Jun 17, 1999)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Butcher)*

Butcher thats correct for CIS basic, but for CIS lambda lowering the lower chamber pressure will also get more fuel...over on top of what you get with the plunger fully up...
regards,
Peter T.


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (gearhead455)*

quote:[HR][/HR]What if someone made a frequency valve driver box? Can't be hard (I made an injector driver in high school)... Just make inline connector to the F valve electrical connector. Have a relay that switches the frequency valve from being driven from the ECU to being driven by a homemade driver. 
In the driver, use a variable potentiometer to adjust a R/C time constant, which will in turn change the duty cycle to anything you want.
[HR][/HR]​I made one, and it works as far as I can tell. If you want more info, I'll give it to you.
-Steve


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Butcher)*

quote:[HR][/HR]The frequency valve regulates the counter pressure on top of the control piston of the fuel dist. If you hold the air flap all the way up and the control piston is all the way up, more or less pressure at the top of the control piston will not change the fuel delivery [since the piston did not change height]. I hope this makes sense.[HR][/HR]​I think the frequency valve alters the differential pressure or something like that, not the air flap counter pressure. I'm not positive, but I'm pretty sure. One reason I say this is because I did a fuel flow test a while back with the frequency valve at 0%, and the flap all of the way lifted, and I only got enough fuel for about 100 HP or so. It's a sure thing that people are running more than 100 HP on these fuel distributors. I did the same test for the volvo unit, and only got ~150 HP worth of fuel. Maybe I screwed up in some other way, but I think it's the duty cycle that was killing the fuel flow. I'll do the test and see what I get.
-Steve



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## J. Daniel (Dec 3, 1999)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

Stephen is correct that the frequency valve controls the pressure in the lower chamber and therefore the differential pressure.
The warm up regulator adjusts the control pressure.
Both change the amount of fuel flow for a given mass air flow.


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## need_a_VR6 (May 19, 1999)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

What about building a secondary frequency valve controller that ups the duty cycle with respect to a certain boost pressure. Just use a MAP sensor an an amplifier and toss it into the injector driver for the input. Have it default to 60% at WOT and then do the boost tuning from there. It can't be *that* hard to build. 
Stephen, mind sharing your injector driver design with us?


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## Butcher (Jan 31, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (need_a_VR6)*

I stand corrected.


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (need_a_VR6)*

quote:[HR][/HR]What about building a secondary frequency valve controller that ups the duty cycle with respect to a certain boost pressure. Just use a MAP sensor an an amplifier and toss it into the injector driver for the input.[HR][/HR]​Yes, you could come up with something to do that, for sure. A straightforward approach would be to increase the duty cycle more or less linearly with boost. You could get more complicated and use a microcontroller to vary the PWM with boost (and RPM, etc, etc.) and get arbitrarily complicated, but I think it's probably overkill.
My guess is that for a homebrewed thing like we are talking about, one adjustable boost level - maybe two, is enough. Trying to really tune for any boost level, etc, gets into stand-alone engine management territory. 
Just my $0.02.
-Steve


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (need_a_VR6)*

quote:[HR][/HR]
Stephen, mind sharing your injector driver design with us?[HR][/HR]​Here you go..
http://web.qx.net/lizjones/steve/PWM_timer.gif
This is the main part of the whole deal. It's based directly on the "Intervalometer" (poor name, if you ask me) circuit on page 15 of the Radio Shack "Engineers mini-notebook" series covering the 555 timer. The two adjustable potentiometers let you set up the duty cycle. One is a "15 turn precision potentiometer" which is used to "fine tune" the circuit. The other one is for normal adjustment. I tune it by cranking the adjustment pot to max, and then tweak with the 15 turn pot until I get 90% or so. Once set, the precision pot is left alone. The whole idea behind this is so you can use the full range of the adjustment pot but not overshoot the 90% mark (or whatever you are comfortable with). Too high of a PWM duty cycle is hard on the frequency valve. 
http://web.qx.net/lizjones/steve/pwm_ps.gif
This is the power supply circuit. It's pretty simple, but I don't claim to have a full understanding of it. The diode is just to protect the circuit in case you apply the power / ground to the wrong terminals. The three capacitors act as "low pass" filters to clean up the input signal (the alternator can produce a good deal of ripple). The capacitor values, as I understand it, are not entirely critical. Throw a few in there of a few different sizes, and you're done. Maybe someone on Vortex can explain this part better... (My guess is that we could get away withotu them alltogether...)
http://web.qx.net/lizjones/steve/driver.gif 
Once again, I can't really claim credit for this circuit either. I stole this one from the CIS box. For continuous operation, the 10 watt resistor maybe should be increased to 15 watt for an extra margin of safety. In all likelihood, though, 10 watts is enough. It acts as a current limiting resistor for the frequency valve, and protects the transistor from inductive kick from the freq. valve during turnoff. The 1/2 watt 1k resistor is a current limiting resistor for the PWM output. I actually used a 500 ohm resistor because I was worried about having a high enough base current for the transistor. Upon inspecting the Bosch circuit, I learned that they used a 1k resistor. The transistor is a run of the mill NPN transistor, with the collector tied to the big 10 watt resistor, and the emitter tied to ground. There is a "protection diode" of some sort from the base to the collector. I don't understand what it does.

http://web.qx.net/lizjones/steve/PWMcircuit.jpg
And that's the prototype that I built. 
http://web.qx.net/lizjones/kate/kate_lampshade.jpg
And that's my "lampshade dog" that just got back from the vet. Just in case you wanted to know.









-Steve


[Modified by Stephen Webb, 4:19 PM 8-16-2002]


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## EuroVeeDub (Nov 16, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

Man, I feel stupid reading this post... I just realized how little I really do know








You guys seem to know *exactly* what you are talking about with all this stuff







I wish I could understand half the stuff you guys are talking about








If you get a chance can you break this stuff down "Barney style" for me? I'm still learning, and I am *very* interested in what you guys have to say (I am just clueless though). Especially since I am planning a turbo project for my Bunny








Thanks guys http://****************.com/smile/emthup.gif 
-Drew


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (EuroVeeDub)*

quote:[HR][/HR]Man, I feel stupid reading this post... 
[HR][/HR]​No sense feeling stupid about anything. Life would be boring if we all knew everything about everything.
quote:[HR][/HR]
I just realized how little I really do know 
[HR][/HR]​For me, that realization (time and again) has been very helpful.

quote:[HR][/HR]
If you get a chance can you break this stuff down "Barney style" for me? I'm still learning, and I am *very* interested in what you guys have to say[HR][/HR]​I'm willing to take some time to explain or answer questions -- shoot.
-Steve


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## maddassbus (Sep 30, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (EuroVeeDub)*

I'm riding in the passenger seat with EuroVeeDub!







These CIS posts are great... This would be a great trick if I had a frequency valve







I've been thinking about raping my trashed 84GTI for it's fueling...Is this a good idea??


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## need_a_VR6 (May 19, 1999)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

Stephen, thanks for the info, pretty straightforward stuff. 
I just remembered I have three 8051 Microcontrollers in a box in my closet. Just need to get the analog i/o stuff for them and I can build some wacky stuff. 
Interesting ideas. I'm probably going to build my own injector controller.. and run it in parallel with the stock freq valve. Best for safety as you never know when your home made device could tank.


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (need_a_VR6)*

quote:[HR][/HR]I just remembered I have three 8051 Microcontrollers in a box in my closet. Just need to get the analog i/o stuff for them and I can build some wacky stuff. 
[HR][/HR]​I don't know much about the 8051, but they seem to be fairly popular for these types of projects. I have another project that's on hold right now -- it's an electronic boost controller based around a PIC micro. I've also thought about building an ignition retard box (based on boost), but haven't started. I'd be interested to hear what projects you might be woring on.


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## need_a_VR6 (May 19, 1999)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

quote:[HR][/HR]I'd be interested to hear what projects you might be woring on.[HR][/HR]​Well, other than waiting for my VR6 crank to get back from Matrix and keeping my Rabbit running for $1/day .. not alot








I do have a background in electronics and have worked with the 8051/2 quite a bit back when I was in school. Cheap and easy as heck to program, even in straight assembly.
The boost controller and retard box sound neat as well. Never done anything with a PIC though.. all microcontrollers or PLCs for me


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## imaradiostar (May 4, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (need_a_VR6)*

How would you accomplish timing retard with a microcontroller? Just curious...
I've been toying with the whole CIS concept as well recently. From what I understand grounding pin 7 creates 70% duty cycle and pin 11 creates 90% duty cycle. Perhaps other pins or combinations of pins could serve to more carefully select varying levels of enrichment.
I like the idea if a tiny, simple PIC based engine management system. Electronicly controlled parts from more recent vehicles (motronic and cis-e) could be modded to aid in the fueling of a home-built CIS system. The other day I saw a bosch/bentley engine management book for 20 bucks and I'm mad at myself for not buying it...
Shannon- if you and your wife move back to town I'd be happy to teach you what little I know about electronics. I'm a guitar and music electronics tech and I build a lot of guitar amps and pedals. I'm excited to try my hand at engine management as well!!
jamie


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (imaradiostar)*

quote:[HR][/HR]How would you accomplish timing retard with a microcontroller? Just curious...
[HR][/HR]​There are three main pieces, in my mind.
1. Intercept timing signal (probably at the distributor), from this you can compute RPM (need a fairly
reliable clock for the microcontroller -- RC won't hack it, probably need crystal or ceramic resonator)
2. Compute (or use lookup table) length of time to delay based on RPM and external conditions (such
as boost, knock, etc). 
3. After appropriate delay, signal for spark.
There are a few gotchas. First you have to have a reliable way of detecting the signal from the distributor (or wherever). National Semiconductor makes a chip for this; I forget the numbers. 
Also you need a way to compute the delay interval in seconds (microseconds), but your timing retard is not in time, it's in crankshaft degrees. (3 deg retard at 6000 RPM is different than 3 degrees at 3000 RPM), not a big deal, but it has to be done right. 
Finally you need some way to pass the signal on, which is probably not too hard, but you will need to be sure you are correctly triggering the computer / igniton module. (it is used to seeing a signal from the hall sender in the distributor, -- it may be sensitive to certain aspects of this signal, so your micro may need to trigger some external circuitry that can reproduce this signal. It may be as simple as a quick high/low transition, though. Not sure)

quote:[HR][/HR]
I've been toying with the whole CIS concept as well recently. From what I understand grounding pin 7 creates 70% duty cycle and pin 11 creates 90% duty cycle. Perhaps other pins or combinations of pins could serve to more carefully select varying levels of enrichment.
[HR][/HR]​In this post or another post somewhere, I list several pinst that I traced back to the duty cycle controller in the computer. If I recall, there was another *possible* pin to try, but I don't think I tried it. I don't think combinations of pins will do it, but I could be wrong. If you want that kind of control, I had a post a while ago on making an adjustable duty cycle driver circuit. You can get a very fine adjustment if you like. Worked for me.

quote:[HR][/HR]
I like the idea if a tiny, simple PIC based engine management system. Electronicly controlled parts from more recent vehicles (motronic and cis-e) could be modded to aid in the fueling of a home-built CIS system. The other day I saw a bosch/bentley engine management book for 20 bucks and I'm mad at myself for not buying it...
[HR][/HR]​Good book, for sure. As for the PIC engine management deal, the devil is in the details. I think a whole lot could be done with it, but it would take too much time and effort for me right now.

-Steve


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## purplerabbit (Jun 28, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

You guys seem pretty smart about this stuff so I have a question.
I have a turbo diesel I'm putting on my jh engine and I also have a cartech rising rate fuel pressure reg. I plan to put this in the return line after the freq. valve and everything. I am concerned about whether this will work at all and also whether the freq. valve and o2 sensor will somehow disrupt the cartech when on boost. 
thanks


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (purplerabbit)*

quote:[HR][/HR]rising rate fuel pressure reg. I plan to put this in the return line after the freq. valve and everything. I am concerned about whether this will work at all and also whether the freq. valve and o2 sensor will somehow disrupt 
thanks[HR][/HR]​I don't know if it will work or not, but you definitely don't want to restrict the flow of the frequency valve, in my opinion. I would leave the system pressure alone. You will probably get all the fueling you need by hooking a boost sensitive switch (or perhaps FT switch) to terminal 11. (IF your computer is the same as mine...otherwise there is probably some different pin you would need to ground)
Either a boost sensitive CPR or a boost switch hooked to terminal 11 -- either one will most likely do you just fine.
-Steve


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## purplerabbit (Jun 28, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

Just for my knowledge, if at normal running temperature the fuel pressure is at 45psi then a higher fuel pressure would push more fuel through the injectors. I am confused because I read something about more fueling at warm up due to 25 psi fuel pressure. So what is the deal? more pressure = more fuel right?


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (purplerabbit)*

Well, in most fuel systems there is one pressure you talk about -- system pressure. This is the pressure that the injectors see, so increasing this fuel pressure does increase the fuel flow. CIS is a different beast. There is the system pressure, which is related to the fuel flow, but it's not exactly the same as the system pressure in an EFI system...Then there is the control pressure,which is probably the main reason people are scared of CIS. The control pressure acts agains the fuel plunger, and higher pressure makes it harder for the air flap to lift, lower pressure is easier. So, with "cold control pressure (25 psi or so, perhaps) the flap is easier to lift, so you get more fuel enrichment (cold engines need more fuel)...The hot control pressure is higher, so the air flap sees more resistance in movement, and therefore doesnt lift as high for a given amount of airflow... 
Not sure if I'm answering your question or not, but increasing the control pressure does not increase fuel flow. 
-Steve


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## purplerabbit (Jun 28, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

Ok, thanks for explaining that. But ok then, from reading that it seems that my adj. fpr is usless(cause it increases pressure).
However then the frequency valve comes to mind. How does this work? It would appear that this controls the amount of fuel going back to the tank, hence controling the fuel pressure. If this is the case then my cartech inline fuel pressure regulator would work because it does exactly that. Please let me know what you think.


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## purplerabbit (Jun 28, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (purplerabbit)*

woops I meant to ask if the frequency valve increases the fuel pressure for inrichment or lowers it?


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## arvcube (Aug 11, 1999)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

doesnt the warm up regulator control control pressure at both cold engine temp and hot engine temp only? thats basically its main purpose...sensing a cold engine block will restrict fuel flow to the top of the plunger in the fuel dist, thus allowing the plunger to rise more freely, giving a richer fuel mixture when engine is cold and ...when the block is warm-hot, the wur allows fuel pressure from one line to flow thru the other line of the two that it has and that pressure acts on the plunger, adding resistance to plunger movement, leaning out the mixture..therefore, doesnt the frequency valve control system pressure, since control pressure is needed to act against the plunger so as to return the plunger to rest position, or at least have it follow the flapper when the flapper goes down? otherwise, when the flapper drops, without the control pressure on top of the plunger, the plunger would stay up in the fuel dist bore..? so wouldnt it be possible to retain the wur in the system, as well as the frequency valve (so the lambda system will still work), remove the valve/springs/shims that positive regulate the system pressure, and plumb in a boost sensitive pressure regulator in its place? just one of those days..sorry for the rambling


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## imaradiostar (May 4, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (purplerabbit)*

OK....I'm going to try to sum this up the best I can. Anyone who knows better please correct me by all means...
The fuel pump creates about 65-75 PSI of pressure. Any amount above this pressure is relieved by the pressure release valve in the fuel distributor. The frequency valve is connected in parallel with the pressure release valve so that it also causes a decrease in system pressure. When the duty cycle is higher the system pressure is higher because less fuel is allow to escape to the return lines. If your frequency valve were disconnected it would essentially create 100% duty cycle, completely removing the frequency valve from the pressure equation.
The WUR or control pressure regulator (or whatever other name you can come up with) serves to vary the amount of pressure on the top of the fuel distributor. When this pressure is high there will be less deflection of the air flapper at a given amount of air intake, thus leaner running. When the car is cold the control pressure is lower, allowing greater deflection of the sensor plate and more fuel is delivered to the engine.
The lambda system becomes active once the engine is warmed up. It defaults to a moderate duty cycle during warmup to allow the engine to run half decently until the o2 sensor is hot. Once the o2 sensor is operational and the coolant temp has risen a bit the lambda computer will vary the duty cycle of the square wave that's going to the frequency valve. This allows dynamicly controllable adjustment of fuel pressure to compensate for variations in altitude, air density, temperature, and engine load.
The full throttle or WOT switch simply lies to the computer and tells it that the car is cold, forcing the computer to use a fixed 60% duty cycle without regard to the o2 sensor. This allows the engine to make more power at higher RPM where the stochiometric ratio isn't always the ideal fuel/air ratio.
Like I said, that's how I understand it....feel free to correct me!!
jamie


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (purplerabbit)*

quote:[HR][/HR]woops I meant to ask if the frequency valve increases the fuel pressure for inrichment or lowers it?[HR][/HR]​I think it decreases the "upper chamber pressure" or something like that. I think the whole idea is to increase the differential pressure, (by lowering the upper chamber pressure) which results in more fuel flow for a given air flap height. I'm not certain on the details -- Anyone else care to comment? Peter?
So if you are going to use the FPR, you would want to use it to increase the system presure, but I'm not sure how CIS responds to system pressure changes. Some have suggested that you can increase your fueling this way, others have said that it has little or no effect. Indeed by looing at the fuel pressure specs there is a fair amount of "slop" in the range of acceptable pressure...so maybe the system isn't too sensitive to system pressure. Again, I don't really know.
-Steve


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (arvcube)*

quote:[HR][/HR]doesnt the warm up regulator control control pressure at both cold engine temp and hot engine temp only? thats ... doesnt the frequency valve control system pressure, since control pressure is needed to act against the plunger so as to return the plunger to rest position, or at least have it follow the flapper when the flapper goes down? otherwise, when the flapper drops, without the control pressure on top of the plunger, the plunger would stay up in the f[HR][/HR]​I think you are mostly on target, and I think regulating the system pressure is the most viable approach to using a FPR in this case. Not sure. 
-Steve


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (imaradiostar)*

quote:[HR][/HR]The fuel pump creates about 65-75 PSI of pressure. Any amount above this pressure is relieved by the pressure release valve in the fuel distributor. The frequency valve is connected in parallel with the pressure release valve so that it also causes a decrease in system pressure. 
[HR][/HR]​I don't think the frequency valve affects system pressure, but differential pressure (upper chamber pressure) or something like that. Also, to be picky, the pump doesn't create pressure, just flow -- the restriction in the system (fuel pressure regulator) is what creates the pressure.








quote:[HR][/HR]
When the duty cycle is higher the system pressure is higher because less fuel is allow to escape to the return lines. If your frequency valve were disconnected it would essentially create 100% duty cycle, completely removing the frequency valve from the pressure equation.
[HR][/HR]​Again, I think the frequency valve affects a different pressure, and I think disconnecting it would be 0% duty cycle, it being closed all the time. Higher duty cycle decreases some pressure, but causes more fuel to flow. That's my understanding.

quote:[HR][/HR]
The lambda system becomes active once the engine is warmed up. It defaults to a moderate duty cycle during warmup to allow the engine to run half decently until the o2 sensor is hot. Once the o2 sensor is operational and the coolant temp has risen a bit the lambda computer will vary the duty cycle of the square wave that's going to the frequency valve. This allows dynamicly controllable adjustment of fuel pressure to compensate for variations in altitude, air density, temperature, and engine load.
[HR][/HR]​precisely!
-Steve


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## gearhead455 (Oct 30, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

Control pressure does not change air flow sensor plate deflection.
Inside the fuel distributor there is a diaphragm, the upper side is control pressure and the lower is feed pressure to the injectors. More pressure on the top side fighting against system feed pressure the less fuel to the injectors.
The frequency valve dumps pressure (lowers control pressure) to enrich the overall mixture. The more ON time, the lower the control pressure.
K-lambda will compensate to any system pressure changes by altering control pressure. The best way to manipulate the system is with the frequency valve (on lambda systems).
100% duty cycle is capable of flooding out the engine at WOT if you desire.


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## imaradiostar (May 4, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

quote:[HR][/HR] Again, I think the frequency valve affects a different pressure, and I think disconnecting it would be 0% duty cycle, it being closed all the time. Higher duty cycle decreases some pressure, but causes more fuel to flow. That's my understanding. [HR][/HR]​I'm not sure on this one...the reason I suggest that is through my disassembly of my fuel distributor the other night. I think it does effect differential pressure but only indirectly. When the frequency relay on my car quit, the fuel pressure went up dramaticly as a result of the frequency valve remaining closed all the time. The frequency valve relieves not the system pressure but the pressure after the fuel has already been metered to go to the injectors. You can see the frequency valve (16 below) is connected to allow the already metered fuel to be released directly to the fuel return without being sent to the injectors.








I'm not sure what all the different pressures are called but I'll know soon when my Bentley fuel injection book arrives...
jt


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## Stephen Webb (Apr 12, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (gearhead455)*

quote:[HR][/HR]Control pressure does not change air flow sensor plate deflection.
[HR][/HR]​I guess I may be mistaken, then. I thought I had read this more than once, though.
-Steve


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## imaradiostar (May 4, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

Some more thoughts from the dark recesses of my mind...once again, not an expert, just sharing how I understand things.
In my mind the problem with the control pressure thing is how it effects the overall maximum fueling of the car. If the control pressure is too low the airflow sensor will be allowed to "max out" reaching maximum available fueling. Once this happens there will be no room for additional fueling at high engine speeds/loads. If you lean out at high RPM you have the potential for increased EGT/combustion chamber heat which can be destructive to the engine. This can be compounded on a forced-induction engine where intake air temps may by higher as a result of compression.
An ideal way to increase maximum fueling is to increase system pressure, assuming by system pressure we're referring to the pressure created by the fuel pump working against the pressure relief valve. My (yuck) haynes manual says every 20 thousands of shim you add to the relief valve will increase system pressure by 4 PSI. A 1/16th inch washer of the correct size would increase system pressure about 12 PSI- a rather sizable increase! 
That being said, I'm sure there are limits to how the system works. Like any mechanical or electronic system there are tradeoffs. There are many things that effect the physics of how a fuel distributor works- from the shape of the walls of the sensor housing to the diameter/valving of the plunger in the fuel distrib to many other things like air density or injector back-pressure. If you were to graph all of the factors envolved you would find areas where each component operated most efficiently at a given fuel pressure, air pressure, control pressure or engine requirement. The fuel distributor is most likely operating close to its most effecient range in stock form, knowing that bosch designed these things to work on a wide variety of vehicles.
The fuel distributors in our us made 81-84 rabbits are built to "overfuel" the engine and release the excess fuel via the frequency valve. The euro 16v fuel distributor is designed to operate without aid of an oxygen sensor. This means that the fuel requirements are dictated purely by the physics of the air sensor and a vacuum sensitive WUR. Fuel pressure (system pressure) on both systems is more or less a constant that is set by the pressure relief valve in the fuel distributor.
Another note- I was totally wrong when I said that the frequency valve is wired in parallel with the pressure relief valve. That isn't correct because it would reduce the effectiveness of a control pressure reg/WUR. 
The system pressure is more or less a constant set by the force of the spring in the pressure relief valve. The control pressure is set by the WUR/CPR. The frequency valve relieves the metered pressure going to the injectors...in this manner excess fuel pressure is more immediately relieved (to solve an overly rich condition) without the need for movement of the sensor plate. The inertia of the sensor plate wouldn't allow for the immediate pressure change that the frequency valve allows.
Think of it like a dual stage regulator for welding...the first stage (pressure relief valve) serves to set system pressure. The flow plate meters fuel based on the engine's vacuum. The frequency valve serves as a realtime fine adjustment after the fuel has already been metered, like the second regulator on a welder or even the fine adjustment on the handle of a gas torch.
Man I think this stuff is rad...sorry to nerd out on you guys.
jamie


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## arvcube (Aug 11, 1999)

*Re: CIS fueling, frequency valve, terminal 11, etc. (imaradiostar)*

i think we may be confusing ourselves when we're talkin about differential pressure regulators and control pressure regulators (wur)..im not sure about cis-e and if the dpr is variably changed by sensors or what not, but i think the dpr in the cis-e systems would be associated with the pressure relief valve in cis systems. in that diagram...it looks like the frequency valve works in conjuction with the dpr in controlling lower chamber pressure and overall fuel pressure to the fuel injectors..therefore im thinking, in cis, if it worked the same way, then that the frequency valve ultimately "varies" system pressure in lambda systems..and the pressure relieve valve is present to set a preset system pressure...why i say this is because when i ground out the 02 sensor wire that goes to the oxs control box, the frequency valve stops buzzing (closed position), a/f gauge reads full rich and the engine stumbles, as it would in an overly rich condition....now with the frequency valve closed, fuel returned to the tank via the frequency valve is reduced, making the fuel exit the system thru the injectors... does this sound right? btw, that diagram must not be of a vw engine/fuel system because none of the 16v motors came with warm up regulators plumbed into the fuel system because of the differential pressure regulators....right?


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## imaradiostar (May 4, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (arvcube)*

You're right- a warm up regulator and a control pressure regulator are different. When I said control pressure reglator I guess I should also say differential pressure regulator. For all intent and purpose to me they are the same thing....of course I probably have the terminology wrong and I'm making a big fool of myself.
The later systems (CIS-E and Motronic) use a DPR in place of a WUR. The CPR is controlled by electronics and vacuum- some WUR's also had a vacuum fitting, like an audi 5k turbo WUR. The WUR mounts to the block while a CPR/DPR is mounted near the fuel distributor in most cases. They accomplish the same thing through slightly different means.
Assuming the fuel pump is in good shape it'll try it's best to always pressurize the fuel distributor with a set pressure of fuel. That preset lower chamber or system pressure is set by the pressure relief valve. The WUR/CPR (depending on the fuel system) meters a specific amount of pressure to establish the amount of effort needed to pass a given amount of fuel...when the car is cold, the sensor plate "weighs" less allowing the engine to breath easier while running a little richer.
If you ground your o2 sensor and the frequency valve stops altogether then I think something may be wrong- should the computer go into "limp" mode (45% duty cycle IIRC) if the o2 sensor is disconnected or grounded. Not sure on this one, just going on what I remember reading.
The frequency valve doesn't effect the system (meaing lower chamber) pressure so much as it effects the pressure after it's been metered to the injectors and is in the "middle" chamber of the fuel distributor. Control pressure and system pressure are pushing on the top and bottom of the plunger respectively. As the plunger rises it allows fuel from the bottom chamber to be gradually metered into the middle chamber which distributes the fuel individualy to four more small metering valves- one for each injector. The pressure in this middle chamber is relieved split seconds at a time by the frequency valve. 
If you accelerate hard then let of the throttle with the car still in gear, there will be an excess of fuel metered and ready to go to the injectors. The o2 sensor will detect the overly rich condition and instantly lower the duty cycle on the frequency valve to allow more fuel to be sent back to the tank rather than to the injectors...a fuel blow off valve of sorts.
You're right about the 16v thing, I think. There may have been 16v cis-lambda cars overseas but here in the good old USA they were CIS-E or motronic. Plenty of people have run 16v VW engines on CIS-Lambda and there's really no reason why it won't work great if properly set up. Somewhere there was a thread on the euro 16v engines....it'd be good to know for sure.
I'm pretty sure saab and maybe volvo made some 16v engines using CIS-lambda. In fact, wasn't one of the Audi turbo quattros CIS into the late 80's?
jt


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## purplerabbit (Jun 28, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (Stephen Webb)*

Ok, So how does the system get more fuel when people shim the fuel distributor to increase fuel? It would seem to me that the control pressure regulator or the frequency valve would just fix the rise in pressure.


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## imaradiostar (May 4, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (purplerabbit)*

Shimming the fuel distributor means adding shims to the pressure relief valve. More pressure on the spring (which I assume isn't a fixed rate spring) means more pressure for the fuel to push the valve out of the way. This means system pressure goes up. The shims basicly just push the pressure relief valve closed tighter than it normally would....at a rate of 4 psi for every twenty thousands of an inch of shims.
This increases system pressure...which increases all pressures a relative amount, allowing greater pressure at the injectors.
There's a really clear picture that shows the pressure relief valve in my Haynes manual. I don't know if it is in the Bentley or not because I only have a diesel Bentley and an A2 bentley on the way...


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## purplerabbit (Jun 28, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (imaradiostar)*

OK, I think I understand the system, mostly. The control pressure controls how much the plunger lifts and the system pressure is the lower chamber pressure. But if I increase Via shims the system pressure will the control pressure rise. If this is the case then the pressure or amount of fuel into the engine wouldn't change. Because the plunger would be harder to lift up but when lifted more fuel would go to the injectors.

Anyway, I'm not sure if thats right but what I really want to know is where to put my cartech rising rate fuel pressure regulator. It would seem that just after or before the frequency valve would be the best due to it controling the metering to the injectors. I'm not sure if it would be better before or after because the cartech fpr only restrics the pressure at boost conditions. But will the frequency valve try to adjust the metering when the cartech is on and if so where will the cartech be unaffected before or after the frequency valve. I would think that just before or between the frequency valve and the metering it controls in the chamber. Because the cartech doesn't affect the normal operation of the freq. during normal conditions but on boost the fuel pressure regulator kicks in and restricts the flow therefore increasing the pressure at the injectors. And the frequency valve would probably not affect the cartechs adjustment.
And by the way all of this is given that the metered pressure needs to go up for the injectors to get more fuel. Assuming the freq. valve increases pressure going to the injectors.
JT and anyone else intrested and knowledgable let me know Where I should put it.


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## gearhead455 (Oct 30, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (imaradiostar)*

I don't mean to be an ass, but about half of what has been written is incorrect.
Read the Robert Bentley Bosh injection book.
If you ground the O2, it will drop the .5V ECU reference voltage and read lean and command full rich (up to 100% duty). If you open the sensor the ECU will command "open loop" 60% duty cycle.
If you reset the base mixture adjustment to 50% duty cycle, any change in system pressure will be detected by the O2 sensor will be automatically compensated by the frequency valve. Raising the system pressure has little effect on K-lambda injection. 
The only reason shims are sold for the fuel pressure regulator in the fuel distributor is to restore intended factory settings. They where never made available to improve "performance". 
The amount of enrichment at WOT (if equipped with wot enrichment) can be adjusted for FREE. Just set the idle duty cycle for 40% instead of 50%. WOT enrichment will be 10% higher at the commanded 60% duty.
If turbo charging is what you are after, a boost sensitive FPR can be placed in line to the output of the WUR/control pressure regulator. The system will still function to change control pressure with engine temperature. The more boost, the more control pressure you can dump to the return with inline FPR.


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## imaradiostar (May 4, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (gearhead455)*

Thanks for bringing the facts...like I said, I don't know for sure waht I'm talking about, especially when it comes to the function of the o2 computer.
I ordered the bosch book and should have it shortly.
thanks gearhead.
jamie


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## purplerabbit (Jun 28, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (imaradiostar)*

Ok I'm absolutly confused. I need to go get that book. I took it out of the library before but I should have bought it. Anyway It sounds like you want me to put the rising rate fuel pressure regulator with one line in the fuel going to the WUR and the other line going to the line coming out of the WUR. So then when it feels boost it can dump the fuel to the return. However the cartech rising rate fuel pressure regulator is made to restrict flow when it feels boost. Because its suppose to go in the return line, cause then it would raise the fuel pressure on a normal system. So is there no place to put this thing or am I wrong somewhere here.


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## gearhead455 (Oct 30, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (purplerabbit)*

I got my poop backwards, the only kind of FPR that drops pressure under boost is a audi 5000 WUR.
Increase the duty and use a 5000 WUR and that will deliver lots of fuel.


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## matt92vr4 (Jul 1, 2002)

*Re: CIS fueling, frequency valve, terminal 11, etc. (gearhead455)*

gearhead, how would I go about setting my idle duty cycle to 40%? 
what year 5000's can I get a wur from?
thank you


[Modified by matt92vr4, 5:38 AM 10-13-2002]


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## gearhead455 (Oct 30, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (matt92vr4)*

You can use a dwell meter from Sears to check the duty cycle, adjust the 3mm allen head mixture adjustment screw on the fuel distributor clockwise until the dwell meter reads 40%.
Any Audi 5000 with a turbo and CIS has a boost sensitive WUR. (dumps control pressure under boost)


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## need_a_VR6 (May 19, 1999)

*Re: CIS fueling, frequency valve, terminal 11, etc. (gearhead455)*

Porsche 924turbos and Volvo 240turbos also have the boost sensitive control pressure regulator. Audis' are the most common from what I've seen though. 
Just FYI, setting the duty to 40% is waay too much fuel for a stock/lightly modded motor at WOT. About 42deg dwell runs to 12.5:1 at WOT on my 2L setup.


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## gearhead455 (Oct 30, 2001)

*Re: CIS fueling, frequency valve, terminal 11, etc. (need_a_VR6)*

You guys want more fuel!








I don't distinguish weather you need it or not.


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## J. Daniel (Dec 3, 1999)

*Re: CIS fueling, frequency valve, terminal 11, etc. (gearhead455)*

quote:[HR][/HR]Control pressure does not change air flow sensor plate deflection.
Inside the fuel distributor there is a diaphragm, the upper side is control pressure and the lower is feed pressure to the injectors. More pressure on the top side fighting against system feed pressure the less fuel to the injectors.
The frequency valve dumps pressure (lowers control pressure) to enrich the overall mixture. The more ON time, the lower the control pressure.
K-lambda will compensate to any system pressure changes by altering control pressure. The best way to manipulate the system is with the frequency valve (on lambda systems).
100% duty cycle is capable of flooding out the engine at WOT if you desire.








[HR][/HR]​Maybe it's a terminology issue.
Control pressure is the pressure applied to the top of the metering piston. This pressure is determined by the warm up regulator and it does indeed effect sensor plate deflection. Reduce the control pressure and the balancing force on the sensor plate is reduced causing it to move higher for a given air flow which increases fuel flow.
Lower chamber pressure is controlled by the frequency valve and its operation is as you describe.


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## alloutofdonuts (Nov 3, 2005)

I know this thread is older than me(7 years since any activity, lol this doesn't look good!), and I'm a lil' bit off topic but what turbos are typically being used with the CIS 10-12 psi?? The MK1 Turbo diesels? I imagine they are mostly different/unique but I'm wondering about the basic size.
I did search and I'm getting conflicting info. 
Reason I ask is I'm going to be turbo-ing the engine in my cabby (to go in my other Rabbt), ghetto style this winter until I can go 16vt w/stand alone down the road.
Something else I'm curious about, when I was younger(19-20) I had an 84 GTI for a few years with an Arkay turbo system on it, it was set at about 15 psi and ran up to 19psi by the PO but had traction issues(both tire/trans & clutch related). Even though I was working on cars then I don't remember knowing a whole lot about it(or maybe it's because I'm old now & have Alzheimer's) but one thing I do remember is the supplemental injector that was mounted in the pipe right before the throttle body WAS NOT hooked up. From what I've read about cis, 15psi shouldn't work very well let alone 19lbs. But maybe the trbo was extra small, I can't remember perfectly but it doesn't seem like it was compared to the tiny stock 1.8T trbos. And as far as I can remember it didn't have ANY kind of aftermarket fuel system or supplement but could have had volvo or other factory parts in it, I really don't know. Anyone who knows/knew me when I had it tells me I should have kept it lol wish I had.....
Thoughts? Or does everone just go to EFI now that it's so cheap?












_Modified by alloutofdonuts at 11:30 AM 10-23-2009_


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## EL DRIFTO (Jul 11, 2004)

*Re: (alloutofdonuts)*

man that is old








here is the easiest way i've seen
http://forums.vwvortex.com/zerothread?id=4196731


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## alloutofdonuts (Nov 3, 2005)

*Re: (EL DRIFTO)*

LMfriggenAO!!!!!! @ http://www.shutupwomangetonmyhorse.com/
I happen to be drinking ice tea when I turned the volume up... was coming out my nose from that. I'm just glad it wasn't lemonade... sweet lemonade..... mmm sweeeet lemonade... sweet lemonade.... yeah sweeeet lemonade! LOL!! I don't know why but I've been listing to that for like an hour now, it doesn't get old hehe.


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## vdubbinmk21980 (Oct 6, 2015)

*what about fueling NA to turbo*

I have an 89 jetta Gl 1.8 8v N/A im putting a 1.6 TD set up on. As far as the manifold, turbo, oil lines, oil pan and intercooler im missing how to adjust the fueling. Do I need a stand alone or do I just do the grounding of the number 11 fuse? I do not really understand the fuel side of this build except I know there will be a larger demand for the fuel. Anyone have any suggestions. I can do it the cheap way too if there is a way to cheat.


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