# Changing or bypassing CIS/CIS-E Fuel cutoff rev limiter



## wclark (Mar 28, 2001)

I have been experimenting for awhile now with simple ways to get around the RPM sensitive cutoff on my CIS-E GTI. What I have learned applies to other cars in the A1/A2 family as well.
As many of you know the engine control electronics of the CIS-E engines will limit engine RPM by cutting off fuel, via the fuel pump relay in the 6200-6500 RPM range depending on the electronics you have. Later CIS engines also have a fuel cutoff RPM limiter but they build everything right into the relay. Early CIS cars tend to not have a fuel cutoff RPM limiter.
The simple way to get around the RPM limit in a CIS-E while maintaining the automatic fuel cutoff should the engine stall is to switch to a fuel pump relay from an earlier model that had the RPM limit cutoffs built in or withnot limit. A little re-routing of wires in the CIS-E relay panel is needed to make this work because the pinouts are a little different and we need to remove the ECU control wire and instead use a signal from the coil. The good news is the coil wire signal is already in the CIS-E relay panel and for most of us, unused relay panel locations can supply any needed spade connectors.
Later CIS cars can just switch relay types to raise the limit. 
The hard part has been locating and testing the proper relays.
There are 2 basic relays which will work. Part number 321 906 059 C is a relay from the early A1 CIS series up to about '82 (and later on some A1) which should have no RPM limiter but does provide a 0RPM shutoff. Its dominate visual feature is a blade fuse in the top of the package. Part number 321 906 059 F is a relay that was used for CIS cars from around '83-88 (and later on some like the Rabbit Convertible). It has an RPM limiter of about 82500 RPM with the 0 RPM cutoff. There is also an H variant which is just like the F except for a cutoff of around 6200 RPM.
In my testing I have gathered new C and F relays from Kracker and KAE. I found the Kracker relays have moved from using an analog (NE555) type timer to control the relay to PIC chips which are one-time programmed at the factory and cannot be altered in the field. The KAE continue to use the 555 timers which can be altered to increase or decrease the RPM cutoff from that delivered with the relay. I understand Seimens also used a similar 555 design but do not think they are currently producing these - you may find them used.
If people are interested, in future installments I will put up what panel mods are needed for the alternate relays (the C and F pinouts are different from each other as well as from the stock CIS-E FP relay), how to modify the KAE F variant for an alternate cutoff (if I can find a source), and where to find a new C or F for cheap.

_Modified by wclark at 9:35 AM 11-9-2005_

_Modified by wclark at 2:04 PM 11-11-2005_

_Modified by wclark at 2:18 PM 11-17-2005_


_Modified by wclark at 6:19 PM 11-17-2005_


----------



## wclark (Mar 28, 2001)

*Credit*

My first installment I want to credit the work of another. I found this site a while ago, found it a useful starting point and want to thank the author for publishing it. http://www.dolphinsci.com/relay.html
I found the current C variant KAE uses a circuit almost identical to the Siemens of the authors article.


----------



## wclark (Mar 28, 2001)

*Wiring Diagram and notes*

I have a diagram in .wmf format (viewable by among other things the windows picture and fax viewer) That gives the pinouts for the C and F relays as well as the present relay socket configuration for 85-87 Golf and GTI 8V. While the relays will also work for Jettas, Bentley shows their relay panels as different and I have done no added investigation as to these panels suitability for these relays.
If you want a copy of this diagram email me at wclark(at)world(dot)std(dot)com.
Notes not on the diagram: (most of this will make little sense without the diagram and a Bentley would be useful)
1) The pinout for the F variant relay is the same as the original socket layouts for the 85-87 Golf, but not the GTI. The Golf it seems continued to use a smart relay like the F. In fact it was the H variant. The GTI on the other hand uses a dumb relay that controlled the ground side of the relays coil thru the KS control unit. So on non-GT/GTI Golfs (GX engines) the F or a modified F can be swapped directly in for the H. The GTI/GT (RD engines) requires the wirefrom the KSU into location 20 (in the Bentley diagram of relay boxes for the Golfs) be replaced with Ground at location 30 and a coil - wire added to 32. The source for this is already in the relay box in the form of a Green w/Blue stripe wire that feed among otherthings the Upshift relay in location 2. In fact since I have no use for the Upshift relay, I simply pulled the spade socket with the coil signal at relay 2 (pin location 11) and moved it since it is the same spade as needed for the F variant relay. 
2) The C variant relay requires re-wiring of all but the Battery + in and power output to the fuel pump if onereuses the location 6 on the panel. The Ignition power from 31 needs to be moved to location 30, the ground connected to 28 (from 30 on the non-GTI), and the coil to 31 (from 32 on the non-GTI). Some of the spades have to be swapped from those wires to be the right size too so it isnt always just a matter of moving the wire with spade attached.
For instance the ground for the C is on the smallest type spade, the coil is on a medium spade as are the battery and fuel pump output power (they are on large spades in the original configuration). In fact I have used location 5 (Rear Wiper) on mine since the socket is a closer match to the C type relay and I had removed the rear wiper anyway. This may not be a good option for others, and of course the whole socket needs re-wiring. It does let me put either in or out quickly for playing around purposes rather than reconfiguring the location 6 sockets over and over.



_Modified by wclark at 2:07 PM 11-11-2005_


----------



## ABA Scirocco (May 30, 2001)

*Re: Changing or bypassing CIS/CIS-E Fuel cutoff rev limiter (wclark)*

Interesting stuff, one comment though, in our first post you say the F variant has a rev limiter of 7000rpm, I haven't found this to be the case, I've been able to rev to at least 8000 with both the F and E variants. BTW, the E variant is NLA, as I found out when I tried to replace the one that was in my 86 Scirocco.


----------



## wclark (Mar 28, 2001)

*Re: Changing or bypassing CIS/CIS-E Fuel cutoff rev limiter (ABA Scirocco)*

When I bench tested the Kraker F variant I get a cutoff of 275Hz which is around 8250 RPM. However when I install this relay in my car ('86 GTI/RD) I get engine cutoff at around 7000. Up to this point I have been assuming the more complex coil signal of the car and the the Kracker PIC implementation of the coil signal input filtering are the reason even though I cant imagine a signal that would scale like that (detecting an additional a pulse about every 6-7 pulses) thru analog filters. I cannot replicate the coil signal exactly on the bench and use a variable duty cycle variable frequency pulse generator instead.
You have me thinking. I have not yet installed the C variant because of its pinout, but plan to do that at location 5 today or tomorrow. I know it has no RPM limit. So if my "drive" test turns up an engine cutoff again around 7000 I will have to look elsewhere for that cause, like the KSCU cutting off its feed to the Ignition Module at that point.

11/11 Update: Rather than a new reply. I ran the C variant today and the engine still cuts off at 7000. Explains the disparity between the F and my car. After confirming the cutoff while driving, I reved the engine in neutral and the cut seems ignition related but I am not sure how yet. I was able to notice the tach didnt immediately drop back and without a load, the engine sounded more like an ignition rev limiter - holding but missing at 7000. Under load it is obvious the power goes away. It will be interesting to locate this (design or malfunction). Oh, I will go back and edit my earlier F info, since it is wrong and the 8250 is probably right.
11/14 Update: I spent a few minutes starting to analyze and isolate the source of the RPM limit yesterday. Using a puse generator set to its 10V p-p limit, I unplugged the distributor hall sender output and with the ignition ON (but engine not started) fed the car a simulated distributor signal. The hall effect module in the distributor operates at around 0V Lo - 12V Hi output and the pulse generator maxed at 0V-10V, but the igniton system seemed to respond the same either way. I was able to increase the pulse frequency to 420 PPS before anything odd happened. I monitored the coil - signal (driven from the ignition module) on a scope. At the 420 point the signal went very asymetric and dropped in frequency, recovering when lowered to about 410. 420 PPS is equal to about 12600 RPM, which initially suggests the igniton system is not a problem. However I was also observing the cars tach as I increased the generator frequency and its readings seemed well below what PPSX30 = RPM would suggest. For instance just before the ignition went asymetric, at around 410 PPS, the tach was indicating 6500-6800 RPM. I know the tach is fairly close under normal conditions since it tracks pretty well to the timing light and the dyno values for RPM. I want to resolve this descrepancy before proceeding or I try to conclude anything even though this tack reading is quite close to where the engine starts to "miss" under operating conditions. By the way, the C variant FP relay, which was in the car at the time did not shut down except at 0RPM. I have since installed the F variant and will watch its actions while retesting things today.
11/14 Update 2. I altered my test and measurement method slightly today. I first recorded some readings from the scope, freq counter and tach using the engine running between idle and 3500 RPM. I then inserted the pulse generator with the engine not running. I had excellent correlation of everything. I then slowly moved the generator up above 3500 (118 pps), stopping at points to record the scope, counter and tach until I heard the F relay shut down. The relay shut off at 275 PPS just like on the bench - or about 8250 RPM. The ignition system and tach tracked smoothly up to that point although the tach was optimistic above 4000. At 6500 it was reading 7000, but it did continue up past the marked scale, pointing almost straight down by the time the FP relay shut off at 8250. Somewhere above that, the coil - input signal stopped tracking the pulse generator and the scope and tach indicated lower RPM than the pulse generator was creating. As this was well above where I can run the engine and the tach being pegged probably isnt good for it in the long run I didnt try to narrow down just where things degenerate electrically. It is sufficient to conclude my engine miss/cut around 7000 on the tach is not from some design limit or malfunction internal to the KSCU. The fuel pump relays perform as advertised. My problem is elsewhere.
11/16 Update. I began looking for the culprit today. The first thing I noticed is that at this "limit" I have no sudden degeneration of signals to the coil, or from the distributor. I do get the sense that I am seeing some sort of low frequency oscillation thru the "loop" that includes fuel metering (the AF meter oscillates lean-rich-lean-rich and as best I can tell, timing, along with the RPM hunting. To eliminate some bizzare fuel management thing from the OXS module causing this I first unplugged the O2 sensor, then switched in the WOT switch (which goes from closed loop operation to a predefined value - that I have set at 24ma). No change. I also replaced the distributor in case I was seeing some sort of jitter from the distributor head (the bearings arent loose by the way). No change. I have a few other spares coming including fresh plugs, a KSCU and OXSCU from a 16V.
11/17 Update. I installed replacement KSCU, OXYCU and igniton modules as well as new plugs today. No change. One thing though. I also swapped in a KSCU from a 16V (that I think works) and the car ran like poop. I was able to get to the 6500 RPM point in neutral and found the limiting still happens. I was under the impression that the KSCU for the '87-'88 16VL was swappable into the RD. However when looking at ETKA I saw the notes for the RD KSCU is labeled KE-Jetronic and the 16VL labeled K-Jetronic. Hmmm.
_Modified by wclark at 8:27 AM 11-11-2005_

_Modified by wclark at 2:02 PM 11-11-2005_

_Modified by wclark at 5:11 AM 11-14-2005_

_Modified by wclark at 9:30 AM 11-14-2005_

_Modified by wclark at 4:26 AM 11-17-2005_


_Modified by wclark at 5:20 PM 11-17-2005_


----------



## ABA Scirocco (May 30, 2001)

*Re: Changing or bypassing CIS/CIS-E Fuel cutoff rev limiter (wclark)*

Interesting, perhaps your electical system is generating some noise that mine is not. Mine's an 86 Scirocco with a CIS-Lambda fuel system and it's been retrofitted with the knock sensing ignition system from an 86 Jetta Carat (RD?). 
You're right about the C variant, I've seen studied it's circuit diagrams and it definitely does NOT have a rev limit, it'll be interesting to see the results of your experiment especially since I think you're running the same KSCU as me and as I said earlier I can rev to at least 8000 rpm.
Perhaps your 7000 rpm "rev limit" with the F variant isn't a fuel pump relay issue at all but rather a sympton of an ignition problem. Here's one more thing, you might want to try as a diagnostic measure; use a horn relay in place of the C or F relay. That will make the fuel pump run whenever the ignition is switched on and will completely eliminate any interaction between the KSCU and the fuel system.


----------



## Fox-N-It (Jul 23, 2003)

I too run the F relay and have seen ~8000 RPM on CIS-E and now MS. I dont make it a habbit.....yet.


----------



## wclark (Mar 28, 2001)

*Re: Changing or bypassing CIS/CIS-E Fuel cutoff rev limiter (wclark)*

For a source of the relays I have been using http://www.busdepot.com/. Their current source are Kracker and KAE. It looks like the C variants are all KAE and all the F/H are Kracker. The web site says the current sourceforthe F is KAE and a call on the phone to them confirmed KAE, but the product I got was Kracker. 
What does that mean? Modifying the F relays for higher cutoff wont happen until a KAE source appears. However, the 8250 cutoff of the F is probably adequate for most and is not the C can be used as it has no cutoff.
Anyway these OEM quality relays from Busdepot are between $16 and $17 each depending on model. WAY less than thru a VW dealer or most other sources that draw parts thru the VW OEM channel. 
By the way, I dont really NEED the pair of "C" variant relays I got for this (I have 3 of the "F" which is plenty). So if anyone needs a new C send me email. I will let them go for $15 each including mailing cost in the US (paypal).

_Modified by wclark at 5:09 PM 11-17-2005_


_Modified by wclark at 4:57 AM 11-18-2005_


----------

