# mk1 cis basic fuel pressure regulator question



## hogg (Oct 2, 2007)

i asked this in the amateur racing forum but thought i'd put it here so that to get more traffic. it is for a racecar so doesn't have to function as a daily driver
I have read about making the fuel pressure regulator adjustable and i think i can do this. i wondered if there was an aftermarket regulator that could be plumbed in place of this regulator that i could put in instead. reason being that it would be nice for tuning not to have to unhook everything to put in a guage to see where you are at and the adjustment process with the homemade system is a bit crude. my idea is to have a regulator and guage under the hood and adjust according to O2 levels, plug reads, performance, etc. i have found fuel pressure regulators in race catalogues but none that work in the 40-60 psi range.
also it needs to be cheap as this is for a low budget racer. 
thanks for any info


_Modified by hogg at 8:11 PM 2-17-2008_


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## antichristonwheels (Jun 14, 2001)

*Re: mk1 cis basic fuel pressure regulator question (hogg)*

you don't do adjustable pressure with CIS.


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## hogg (Oct 2, 2007)

*Re: mk1 cis basic fuel pressure regulator question (antichristonwheels)*


_Quote, originally posted by *antichristonwheels* »_you don't do adjustable pressure with CIS.

well not normally... but i want to


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## epjetta (Sep 19, 2006)

*Re: mk1 cis basic fuel pressure regulator question (hogg)*

if you want to make your car better save some $ and get a stand alone.


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## hogg (Oct 2, 2007)

*Re: mk1 cis basic fuel pressure regulator question (epjetta)*

there are certain racing rules that i have to follow which don't allow for a stand-alone which means that i have to keep the cis system.


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## WackyWabbitRacer (Apr 24, 2001)

*Re: mk1 cis basic fuel pressure regulator question (hogg)*


_Quote, originally posted by *hogg* »_ I have read about making the fuel pressure regulator adjustable and i think i can do this. 

The Control Pressure Regulator (CPR) can be reworked to be adjustable. 








Although the above picture is not exactly like the internal workings of a CPR, it is close enough for explanation. There are two ways of making the CPR adjustable, however the CPR must be disassembled for the modifications.
1. Drill the pressed-in stud and tap it for a long but small diameter metric bolt. Install the metric bolt upward through the bimetallic strip and tighten a nylock metric nut onto the bolt. Tighten the nut just enough to allow the bolt to turn in the hole of the bimetallic strip. 
Then thread the bolt into the tapped hole of the pressed-in stud and re-assemble the CPR. Turn the metric bolt up or down to change the amount of control pressure. Use another nylock nut to keep the bolt from turning.
2. Remove the bimetallic strip, the spring and retaining cup from the CPR. Locate and drill a hole in the rear cover of the CPR so the hole is aligned with the center of the diaphragm. Next get a 3/8 inch thick section of aluminum 1 inch by 1 inch. Drill and tap a hole for a long but small diameter metric bolt. 
Align the aluminum section to the previously drilled hole in the rear cover and TIG weld the section to the rear cover. This is necessary as the rear cover is not thick enough to be threaded.
The end of the metric bolt must be tapered and rounded so the end fits into the center of the diaphragm. Place a nylock nut onto the bolt and thread it to the top of the bolt. Next thread the bolt into the threaded hole until the tapered end touches the diaphragm. Turn the bolt in or out for the desired control pressure. Then tighten the nylock nut to keep the bolt from turning.
Cheers, WWR.


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## hogg (Oct 2, 2007)

*Re: mk1 cis basic fuel pressure regulator question (WackyWabbitRacer)*

yes that looks like a variation on the method i had seen.
thanks so much
look here for some pictures
http://forums.pelicanparts.com...18814
Mark also sent me this idea for those interested

The following reply was posted by Scirocco14gp:
I was successful in using an adjustable rheostat (0-15 ohms) on the 12V power source to the warm-up regulator on my SCCA racecars. The trick is to take the warm up regulator off the engine block so it won't be warmed up by the engine heat. I mounted mine over behind the LF headlight.
Then you can adjust the control pressure anywhere from its starting (cold) pressure which is usually around 18-25 psi to the operating (hot) pressure which is 49-55 psi, depending on your warm up regulator. I used to run mine around 44-45 psi to get the A/F mixture where it needed to be. At the 0 ohm setting, the warm up regulator will function like normal and the bi-metallic spring inside the warm up regulator will be heated up by the electrical heating strip inside of it and the control pressure will rise to its maximum value. At the 15 ohm setting, the resistance will reduce the voltage to the heating strip inside of the warm-up regulator to less than 1 volt and the heating strip won't heat up, leaving the control pressure near the starting (cold) pressure. You just have to find the resistance that will get you the control pressure you want, and that can be found on the dyno or if you have a wide band O2 sensor on your car you can drive around adjusting it until you ge!
t the A/F ratio you want.
Go to any electronics catalog and find a 0-15 ohm variable resistor, splice it into the 12V positive wire going to the warm up regulator and you're good to go!
Mark C


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## WackyWabbitRacer (Apr 24, 2001)

*Re: mk1 cis basic fuel pressure regulator question (hogg)*


_Quote, originally posted by *hogg* »_The following reply was posted by Scirocco14gp:

Mark is a racing friend, and I have seen his adjustable rheostat. It works well when he was using CIS injection. He is now using dual sidedrafts on his Scirocco.
Cheers, WWR.


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