I was browsing Tech tips, and ran across this little tip, and Im wondering if it could damage my stock system? the pressure is increasing for a reason...WHY?


tried this modification and my fuel pressure went from 30# to 40# with only this fifteen second mod. The modification is that I removed the vacuum line from the factory fuel pressure regulator. Also, I capped the fuel pressure regulator connection, so no dirt would get in, and plugged the vacuum line, to maintain vacuum on the engine. I tested the car and noticed a serious change in acceleration. I then took it on the highway, set the cruise for 70 with this mod I was getting an instantaneous reading of fuel mileage of 28-29 miles per gallon. I pulled off of the highway and switched back to having the vacuum line connected. I immediately noticed the power had reduced. I again took the car over the same stretch of highway and the mileage went down to 26-27. I thought the second mileage test would be higher than the first. I checked with my mechanic on this and he said the car is just running more efficiently with the mod than without. One other thing that got better for these test runs with the mod was the temperature of the engine went down. Normally, when the car is warmed up and going down the highway, it'll usually run about 208-211 degrees. With the mod it went to 184-187. My mechanic said that that may be caused due to the cooling effect of more fuel entering the cylinder. I don't know if the temperature differential is going to be a constant, because as you can tell, the tests I did were not scientific in any way. But, I feel there is an improvement, if only in my car. I was told about this mod. via someone who works on, restores and sells parts for nothing but Corvettes. So I thought I'd give it a try. Just make sure that the pressure you attain, if you do this mod, is not too high for your system. Of course you can always put a small needle valve in the vacuum line to reduce the press., if necessary. If this works as well on all, none or slightly modified, Corvettes as if did on mine, then there are going to be a lot more wolves in wolf's clothing out there:-{

 

Hmm, this sounds interesting...Anyone else chime in on this? I am interested in giving this a try. My 87 is stock, but I would like some cheap HP. Just dont wanna damage anything....

 

Sounds like it could work...but that hose was on there for a reason...why was it on there...?

30 to 40 PSI isnt a big increase, I think 35PSI is stock, and an adjustable regulator allows for increase...so...?

Im going to wait for opinions, before I go trying it.

 

What that "test" tells me is that you need to install an AFPR and bump fuel pressure by maybe 5psi.

It is well known that fuel atomizes better at higher pressure...to a point. I believe this may be what you experienced. Install the AFPR and set fuel pressure to where it is now, with vacuum line disconnected. Then bump it say 4psi and check performance; keep bumping it till performance drops off. Then back off 2psi and you are "tuned".

If your car ran cooler it sounds like your O2 or clooant temp sensor may be malfunctioning. Either would prevent your ECM from going closed loop. Otherwise, the ECM will maintain the correct A/F ratio in closed loop mode.

 

oh, this is not me, i copy/pasted from tech tips section.

Im wanting to know if it is safe to do...

 

Understood.

I think that would be a good test and safe enough but I would not leave it as permanent. I just don't think it's the best way to increase fuel pressure. And when you go to WOT, you will lose that pressure increase "edge".

 

where is the Regulator, and what hose is he talking about...im doing it tomorrow!!!

 

the regulator is located in front of the distributor on the right side of the engine. Its under the rear access panel on the upper intake. There is a simple hose that runs from the top of the regulator (the regulator is black) and to the side of the intake plenum. If you have a speed density car you will need to look behind the map sensor to really see the regulator. You can get to it really easy without removing anything on the mass air cars....

 

I'd read that it was a really bad idea, can't remember why exactly but it had something to do with the idea that your FPR should change pressure related to vacuum.

 

Wouldn't it be similar to calling for full fuel (WOT) at all times?

 

Do not do it.

Removing the vacuum line eliminates the ECM's control at Idle and non WOT.

This will cause a very Rich condition. At WOT the vacuum has no effect on pressure. That is why an adjustable fuel pressure regulator can be effective.

 

check out my reply in the general section, where you seem to be duplicating all your posts :leaving: