Ok I got a little problem, or at least I think I do.

I went out the last couple days running the car for about 20-40 mins at a time to get the car broken in and make sure I have everything worked out ok. Well I set the base fuel pressure with the line off to about 48psi so it reads about 42 with it on....after a while of driving it drops to almost 34-36psi under cruising condition and only sees maybe 40-42psi under a load (no boost). So I came back and pulled the line off and sure enough it had dropped to around 40psi. So this time I cranked it up to 50 with the line off. And after a few minutes of driving it had dropped to around 42-44psi. Everytime it seems to loose about 8psi from its 'cold' fuel pressure setting. Now I haven't had the car running this good for a while now, and its been close to a year since I have really driven the car since the motor broke last year. Am I just being paranoid or is something wrong someplace, or is it normal for this kinda of car to run like this? It doesn't have the FMU from the ATI kit on it...so thats the true reading of it.


Fuel system consists of
RaceTronix 255 high pressure intank setup
Aeromotive AFPR
MSD 50# injectors
stock everything else

It is getting pretty hot under the hood from the blower and headers, and the exhaust does come pretty close to the fuel tank (mufflex 4") could it just be getting hot and going into a sort of vapor lock? The first time it did it I just thought it was low on gas and my level gage wasn't reading right, but it only took about 4 gallons. The other problem is once it does drop, and the car is still hot, when you go to restart it, it will not start unless the throttle is wide open.


Only thing I can think of is that it is going into some sort of Vapor lock, because it still has good pressure at start up and key on. The main problem is it varies with temp.

Thoughts? Ideas?

 

The having to floor the throttle to start up the car after it has been running has got me stumped. I am building about the same motor build up as you have, except I am running a vortech at 12 lbs. The motor sounds like it has fuel left in like its flooded or its vapor locked. How are your 02 readings when you are runnin? what kind of fuel regulator are you runnin? what kind of computer programming?

 

Well as was stated above, the car still being broken in..so it just has a base tune to it. O2s are fine and plugs are just slightly brownish in color so it isnt' running to rich. BLMs are in the 130-150 range so its still adding fuel at idle. So its not flooding anything.

Regulator is also listed above.

 

Well I talked to a buddy of mine that does custom tunings. He said he would get the computer programmed especially with all the power adders you have. At least a basic tune if anything. Then after the motor gets broken in, you could get a dyno tune. 50 lbs injectors really dont work well with the stock tune. The computer still thinks you are only running 24 lbs if it still has the stock programming. I switched my one cars injectors to 30 lbs and had to switch the settings on the computer as the car would never idle out good or run to well. After I switched it, It was like night and day. What cam are you runnin?

 

Don't worry about the tune of the car right now, it already knows whats in the car, just the final numbers are not done yet as far as WOT, all around town and drivablity issues are 90% worked out. The tune of the car is the least of my worries right now if it can't substain fuel pressure there will be no way to tune it at all.

Cam's a solid roller....big one

 

My fuel pressure was dropping from 36# to 29# at WOT. The problem ended up to be a restricted fuel filter. Have you replaced yours?

Frank

 

well it must have been temp related because it cooled off around here about 15 degrees today and it is not near as bad as what it was in 98 degree hot traffic in the afternoon.

EvilZ28, if you want to know more about the car and the setup, email me.