# Adjustable WUR with rheostat?



## bunnyhopin (Dec 19, 2007)

I have read the diy on the screw type adjustable WUR, but I would like to try using the electrical method.

Two questions for people who have done so successfully.

1) You mounted the WUR elsewhere than the block correct?

2) What rheostat specifically did you use? 

I have been searching online for one that will work (0-15 ohms) but they are all listed at 500V or greater, I am no electrical engineer so I don't know what I should be looking for? 

Pictures for run 


















Engine prior to install









Any advice would be appreciated.


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## nbvwfan (Aug 15, 2007)

What is your end goal?
I ask because if its performance fuel enrichment, there are easier ways to do it than with the said approach.


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## bunnyhopin (Dec 19, 2007)

nbvwfan said:


> What is your end goal?
> I ask because if its performance fuel enrichment, there are easier ways to do it than with the said approach.



Adjustable air to fuel, I don't think it gets much easier than cutting and splicing 2 wires.


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## nbvwfan (Aug 15, 2007)

bunnyhopin said:


> Adjustable air to fuel, I don't think it gets much easier than cutting and splicing 2 wires.


Fair enough, but you can invest in a couple things and have much better control than resistive flat rate upper/lower chamber pressure regulation that impacts all of the mixture range. Unless you don't care about economy or rough idle and throttle response.

Check out Splitsec.com and look at their AIC-1. They have a Vacuum to atmospheric and atmospheric to 1 Bar auxiliary fueler. 
I am running it on my F/I CIS-E GTI. 
It handle the boost and my worked meter handles N/A. They also have a digital modulator that can work to effect the DPR if you have CIS-E. Planning on playing with one of those on a later build.

A wideband, an AIC-1, a laptop cable, an ABA White/Green top injector, and a ~$95 order to summit to buy/build a fifth injector and some fiddling with a MAP and you can have plenty of additional fuel while also leaving the majority of the CIS intact.

:thumbup:


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## bunnyhopin (Dec 19, 2007)

Well I'm running CIS basic at the moment, I have an AEM wide band to monitor air to fuel. 

Engine is a 1.6 block, JH head, 83mm bore, 90.5mm welded stroker crank, 272 cam, ported head, neuspeed TB. 

At WOT im getting 13.3:1 air to fuel 

I adjusted the WUR manually to 48 psi hot, my cold pressure is roughly 23 psi. 

I don't wanna spend a bunch of money if I don't need to, with research I have done, a rheostat/pot at the WUR should do the trick.

Basically, I intend on manipulating the function of the bimetallic strip in the WUR, by applying less amperage to it using a rheostat/pot to increase resistance, thus less heat, thus less pressure when warm (before the WUR), which equals more flow after the WUR, therein giving me more fuel.

Since I will be mounting the WUR off the block there should be no interference from the heat produced by the engine. 

Best part is, I can make adjustments real time on the dash without fiddling with any hardware in the engine bay.


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## nbvwfan (Aug 15, 2007)

:thumbup:
You've done your homework.
Sounds like a solid approach.


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## JimW337 (Jun 18, 2002)

I'll through my 2 cents in, about what it's worth...

I'm building a Cabby prod racer and have gotten to the point where I have the ATL fuel cell/pump running with all the -6 stainless fuel lines attached to the "Euro" fuel distributor (no frequency valve). I was at the point about to modify the CPR to be manually adjustable and thought I would try the rheostat/potentiometer method first.

I thought I would try a little "Proof of Concept" to see if I could get some real life numbers. I picked up a rheostat from Radio Shack, it's described as a 25 Ohm 3 watt. 

Here's my base numbers without the rheostat...
System Pressure - 75 to 77 psi (stock - 68 to 78)​Cold CPR Pressure - 19 psi (stock - 18 to 25)​Warm CPR Pressure - 51 to 52 (stock - 49 to 55)​I got the Warm pressure by running 12v direct to the CPR

Now here's some numbers with the rheostat, I was trying for CPR pressures in the 42 to 46 range because this has been reported what you want when running wide open throttle in "race mode".
CPR - 42 psi, Volts - 6.5, Amps - .30 (calculated Ohms - 21.6 and Watts - 1.95)​CPR - 43 psi, Volts - 7.0, Amps - .32 (calculated Ohms - 21.8 and Watts - 2.24)​CPR - 44 psi, Volts - 7.5, Amps - .34 (calculated Ohms - 22.0 and Watts - 2.55)​CPR - 45 psi, Volts - 8.0, Amps - .36 (calculated Ohms - 22.2 and Watts - 2.88)​CPR - 46 psi, Volts - 8.5. Amps - .38 (calculated Ohms - 22.4 and Watts - 3.23)​
The little 4 dollar Radio Shack rheostat was overheating, so hot it would burn your fingers and was starting to make funny smells. So, I shut things down. I still want to get some stock readings from my street Rabbit. But I think the concept will work given a rheostat that will handle the Ohms and Watts needed. Next step, go shopping on Amazon.

I don't mean to hi-jack this thread but thought these numbers might help the discussion to move along.


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## raabbiitt (Oct 9, 2008)

I've done this on 2 cars and it works great and is super easy. put the wur up on the fender away from the engine. can't for the life of me find the site that I ordered the rheostat from, but i'll look a little harder. just use the wideband to dial in what you want


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## bunnyhopin (Dec 19, 2007)

JimW337 said:


> I'll through my 2 cents in, about what it's worth...
> 
> I'm building a Cabby prod racer and have gotten to the point where I have the ATL fuel cell/pump running with all the -6 stainless fuel lines attached to the "Euro" fuel distributor (no frequency valve). I was at the point about to modify the CPR to be manually adjustable and thought I would try the rheostat/potentiometer method first.
> 
> ...



Sound like you have some good numbers here.

I have been really busy with work/moving so I have yet to had time to tinker, plus after some timing adjustments the Mk1 has been plenty fast. I ran from a dig against my buddies 91 gt fox, he only has an intake and cat back, he never left my sight up until 80mph, my front door stayed at his rear bumper, coulda been different but he got the jump on me rwd and all. :laugh:

Last month I was running a bit low on oil and spun a rod bearing, because Im an idiot :banghead:

So i will be pulling the engine apart, which is ok, now I can port the head and intake manifold along with adding a tubular header, I will be getting a proper pot and trying this setup.

The physics behind the concept is sound, so there was little/no doubt in my mind that it would work, now that we have some data we are good to go! Thanks for beating me too it Jim! 

Keep posting Jim, I can't always keep up with my projects, lets keep the CIS knowledge base current here on vortex. :beer::beer::beer::beer:


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