fuel pressure at boost

[THEDUKE]

Just wandering what differant fuel pressure differant people are running.
At idle with vac & at boosted levels. Mine is 35vac & 78 @ 24 psi of boost.

 

[kpt4321]

When comparing fuel pressures, all you have to do is state your base pressure with the vacuum hose off the FPR. This is the place your FPR will regulate boost from, at atmospheric pressure. From here, it will raise fuel pressure 1 psi for every psi of boost, and likewise for vac.

If you are getting 78 psi at 24 psi of boost, something is weird. That means you have a base pressure of 54 psi......that's rather high.

What does your fuel system consist of?

....Kyle T.

 

[THEDUKE]

Originally posted by kpt4321
When comparing fuel pressures, all you have to do is state your base pressure with the vacuum hose off the FPR. This is the place your FPR will regulate boost from, at atmospheric pressure. From here, it will raise fuel pressure 1 psi for every psi of boost, and likewise for vac.

If you are getting 78 psi at 24 psi of boost, something is weird. That means you have a base pressure of 54 psi......that's rather high.

What does your fuel system consist of?

....Kyle T.

B&M reg. Base is 42 & it will reach 78 evan @ 20 psi boost. If I get up to 26 or 28 it can get 80 plus.This was my concern.It seems that I am getting more out of the size injectors that I run than others do. No matter what size I run its more than I should be getting away with.My pump is not a walburn.I pulled it out of the books by specs. It puts out 125psi @ some crazy flow.Put it this way ,with the line loose & cycle the pump it can shoot a stream for about 20 feet. I have a 60-1 stageIII turbo & am getting away with 450cc injectors.My motor is stock & I could have better intercooler,pipes & so on.But a set of 680 just drowned the motor & 450 still had room to ajust with. Runs real good with the 450,No knock & pleanty of timing & real smooth & I have run up to 28psi with the 450cc & with NO2. Was just wandering if any body else was running this much fuel.I coudnt get the 680cc toned down enough to run them.

 

[kpt4321]

Even with a base pressure of 42 psi, 450's should not be enough fuel for a 60-1 at 28 psi.

How are you measuring that base? Is that with the vacuum hose off the fpr?


....Kyle T.

 

[ellsjer001]

Just wondering.... what is a recommened fuel press. with the stock turbo and SAFC 2. running 10lbs. low setting and 20 on high..... profec-b. if you could let me know, just got a FPR. I was about to make a new post but came in and saw this one...... Thanks for any info!

 

[THEDUKE]

yes the base is with the vac hose removed & when boost hit it goes up to around 80 depending on how much boost.

 

[jdmawd]

Originally posted by ellsjer001
Just wondering.... what is a recommened fuel press. with the stock turbo and SAFC 2. running 10lbs. low setting and 20 on high..... profec-b. if you could let me know, just got a FPR. I was about to make a new post but came in and saw this one...... Thanks for any info!

43 psi base no vacuum at the reg.

 

[THEDUKE]

yes that is correct. Sorry I didnt no you had replied I am working in the shop right now. But fuel pressure is about 35 with vac on reg. 43 with vac removed from reg. & with vac hooked up & under boost it is about 80. I have a hood mounted gauge.

 

[kpt4321]

See, that just is not right.

80 psi - 43 psi = 37 psi

Apparently, you are runing 37 psi of boost. Sweet.

In all seriousness, something is wrong here, because your fuel pressure is not rising at the proper 1:1 ratio.

...Kyle T.

 

[THEDUKE]

Yes I dont know why it does this . And I know my boost gauge is right I have 4 & have compared them to each other. Also there is two fuel pressure gauges hooked up & I have a shop gauge I throw in somtimes. When I was running the big 16 & the 450cc injectors I had no problem getting tuned & the fuel pressure was the same as now. Well it when 12.10 & the tranny wouldnt come close to shifting.Now with the 60-1 & the 680cc I havnt made a good pass yet,11.50 @ best & thats with a 50 shot. One of the injectors seem to be giving trouble you can see it leaking fuel when you pull the fuel rail up.

 

[97MeclipseGSX]

Unplug on einjector at a time at idle. If performance changes then it is fine. If it doesn't, or you know which one is leaking fuel with rail removed, then have it tested. I had a 680cc do the same thing. It was irrepairable. It was simply dripping non-atomized fuel into the intake...I even had residual fuel coming out the egt probe jacket, scary stuff...

I have 740cc now and having a hell of a time tuning the beasts. I was able to pull 18PSI on a 20g with stock injectors, 255lph, rewire and Fp @ 42 with vac removed. Good luck

Chris

 

[Golden Wind]

I just noticed that you said you had a B&M reg. Is it the Command Flo, because I hear that those don't work correctly since they don't flow any more fuel than stock.

 

[Ronin17]

You have a mystery fuel pump correct? Do you know if it is close to the 255 or supra pump? Golden Wind had a good point, the B&M Command Flo just replaces the top half of the stock regulator, so it doesn't really help unless you are wanting to raise your fuel pressure. It might be the reason you are not getting the correct 1:1 fuel pressure to boost ratio.

28psi on a 60-1 with 450cc injectors is crazy, I wouldn't think that would even be possible. Something is definitely weird about your setup.

 

[Mike 99GSX]

If you had the money to get a 60-1 setup, why don't you just fork over the $250 to get a $125 fuel pump and $125 FPR that is proven to work for our cars. 2 less weird variables on your already fast car to worry about.