Thread: 3 bar VS 4 bar fuel and power

If this has been covered I'm sorry, I'm on my phone and can't search. I went to the track tonight in hopes to break 12's. 3 years ago I ran a 13.7 with a crappy 2.3 60' @ 103mph. I was piss rich with 10.0 on the wideband. Now with a mild street tune and low 11's AFR WOT, I'd have atleast expected 13's again, best time was a 14.4 @ 102. I think there's a boost leak issue, maybe.....

But I'm currently running at 3 bar. I cannot recall if I was at 4 bar 3 years ago when I ran the 13.7. I'm running a T25 with 555's. Would 3 bar vs 4 bar make an .8 sec difference in the 1/4 mile like that? Again, I don't recall of I was at 3 or 4 bar 3 years ago.

I have a Dyno tune appt on the 31st, I suppose I'll find out then for sure.

Thanks guys

Nobody?

The only diff from 3 bar to 4 bar is going to increase the flow rate of your injectors so like in my case it makes the sti 520 cc injectors closer to 600cc. That is all so if your tune is fine at 3 bar there isnt much benefit from 4 bar pressure.

At 4 bar 3 years ago my tune was piss rich but better also flowing more fuel. My fuel/tune is now set for 3 bar....will that have been a factor in my 1/4 mile time? Running the same, if not a little more psi boost.

Fuel pressure isn't your problem here. Sounds like your afr's are decent, so you know the injectors are flowing fine at 3 bar. Do you have an afpr and fuel pressure gauge? You could always bump it up some and see how the car reacts if you want to eliminate this as an issue, however I don't think it is one.

You should definitely check for boost leaks and that your bov is functioning properly and doesn't have a leaking diaphragm as well. Also check that there is no exhaust leak where the downpipe bolts to the j pipe. This has happened to me before and there was a considerable loss in power.

you're def. losing boost somewhere...

How is that possible? I thought the logic of turbo exhaust system is that considering after turbo, the more open exhaust the better.

I do have an afpr and fuel gauge. That night at the track I ran outta time to make any adjustments and test them. I got there late and it wasn't Till the 3rd pull I realized there was something wrong. any adjustments now are meaningless to me, SOP hp gain is difficult to determine.

Funny you mention the BOV, some peeps keep telling me to test it. They say to block the vac lines and take a pull to see what happens. It'll either tell me or not after that pull. I will say the BOV releases even after just as minimal of 1 or 2 psi regardless where the adjustment screw is set. I don't recall it being that "light."

Also for what it's worth, she's only holding boost in 5th gear. Every other gear she falls off. Each lower gear is less and less. 5th will spike 16 and hold 14psi. 4th also spikes 16 but falls to 12psi. 3rd just barely reaches 14 maybe 15psi and drops to around 8. I pick up speed and go faster but as my speed increases I can feel the loss of power. down low she feels so damn strong though roasting 2nd and chirping 3rd all throttle, which she's never done 3rd until recently squaring away some boost leaks.

No. It would make no difference assuming the same AFR.