i build boost just fine but my power lags BIG TIME!!??

[4BangerV8Killer]

I have a 92gsx with a 50trim and supporting mods i build full boost at like 4500rpms but i dont feel my power until i hit the full 21psi anything under that and it pulls alittle but not hard and it seems as soon as i hit 21psi it pulls crazy hard....iv done a boost leak test and sealed up the big leaks....what else could be making my car act like this.....when i do a run ill hit power at full boost then shift at 6k or so and my power will drop again until i hit 21psi then the car will pick up again.....is this normal for a 50trim? or what could be the problem?

 

[elfroggo]

What kind of tuning are you using? I would check a log if possible. Without more information it's really hard to tell.. It's possible that you could be drowning the engine with fuel until you hit around 21 psi at which point the airflow matches the fuel being injected.

I wouldn't want to run that high psi just yet though if it's not running right. Turn down the boost and figure out what is wrong.

 

[pooker]

Sounds like you could possibly be pulling timing from a bad tune.

 

[4BangerV8Killer]

im tuning 720cc injectors with an safc....i know its bad but i do have a good tune on it...not really pulling timing and im not really running rich. ill get my last log on here but besides a bad tune what could it be.....and when i post my tune what info do you guys want?

 

[pooker]

Well its definately strange, Its kind of hard, but are you saying that you feel absolutely no power until 21 psi? I dyno'd 320 with 15 psi with a 50 trim thats probably smaller than yours and using a mitsubishi flange which is pretty restrictive for these turbos. Not unless you just have a bad boost source for your mbc you could have bad rings or low compression and getting major blowby.

 

[tom04841]

im tuning 720cc injectors with an safc

Plain and simple, you are pig rich until you hit 21psi. It has been discussed over and over, the biggest injector you can compensate for is 650's with an safc. Do a search. You need some other form of fuel management.

On top of that, your timing is probably thru the roof

 

[4BangerV8Killer]

here is my last log....(from tonight) 21PSI

Rpm ~~~ INJD ~~~ KNCK ~~~ 02 ~~~ Timing

3062 ~~~ 18.7 ~~~ 0 ~~~ .87 ~~~ 28
3281 ~~~ 24.2 ~~~ 0 ~~~ .87 ~~~ 26
3593 ~~~ 40.6 ~~~ 0 ~~~ .89 ~~~ 19
3937 ~~~ 59.3 ~~~ 0 ~~~ .89 ~~~ 12
4281 ~~~ 67.1 ~~~ 0 ~~~ .87 ~~~ 11
4562 ~~~ 71.8 ~~~ 0 ~~~ .87 ~~~ 14
4875 ~~~ 71.8 ~~~ 0 ~~~ .87 ~~~ 15
5212 ~~~ 75.7 ~~~ 7 ~~~ .85 ~~~ 14
5843 ~~~ 79.6 ~~~ 17 ~~~ .85 ~~~ 16
6000 ~~~ 82.8 ~~~29 ~~~ .83 ~~~ 10
6406 ~~~ 85.9 ~~~ 28 ~~~ .83 ~~~ 11
6656 ~~~ 87.5 ~~~ 28 ~~~ .83 ~~~ 10
5968 ~~~ 27.3 ~~~17 ~~~ .19 ~~~ 31

 

[DJYoshaBYD]

here is my last log....(from tonight) 21PSI

Rpm ~~~ INJD ~~~ KNCK ~~~ 02 ~~~ Timing

3062 ~~~ 18.7 ~~~ 0 ~~~ .87 ~~~ 28
3281 ~~~ 24.2 ~~~ 0 ~~~ .87 ~~~ 26
3593 ~~~ 40.6 ~~~ 0 ~~~ .89 ~~~ 19
3937 ~~~ 59.3 ~~~ 0 ~~~ .89 ~~~ 12
4281 ~~~ 67.1 ~~~ 0 ~~~ .87 ~~~ 11
4562 ~~~ 71.8 ~~~ 0 ~~~ .87 ~~~ 14
4875 ~~~ 71.8 ~~~ 0 ~~~ .87 ~~~ 15
5212 ~~~ 75.7 ~~~ 7 ~~~ .85 ~~~ 14
5843 ~~~ 79.6 ~~~ 17 ~~~ .85 ~~~ 16
6000 ~~~ 82.8 ~~~29 ~~~ .83 ~~~ 10
6406 ~~~ 85.9 ~~~ 28 ~~~ .83 ~~~ 11
6656 ~~~ 87.5 ~~~ 28 ~~~ .83 ~~~ 10
5968 ~~~ 27.3 ~~~17 ~~~ .19 ~~~ 31

Isnt all that knock in the high RPMs bad? that seems like a WHOLE lot....

 

[4BangerV8Killer]

Its very bad im having some trouble getting rid of that knock and i dont know why.....seems like the more fuel i dumb into that rpm range the more i knock.

any help guys on why my power is lagging or why im knocking like that?

 

[fwdeclipse]

Im not sure if you just dont want to come to conclusions you cant tune 720s with a safc. It just does not work. You are probably getting knock from all the fuel. My buddy had 650s with an safc and he was at like -35 so with 720s you would have to be around-45 to -50 and your timing would be crazy. Start saving for dsmlink or get a keydiver chip to compensate for your injectors.

I just looked at your profile and it shows no fuel pump and that your on the stock exhaust.A stock fuel pump will not keep up with 720s or anything over 450s. Also if your on the stock exhaust that would explain alot of lag and then you get all the power once your full boost hits. Its a combination of 720s and safc along with no fuel pump or exhaust.

 

[4BangerV8Killer]

ya i understand the safc not being able to tune the 720s. I have an emanage with a timing harness and everything but I dont know how to install it/gotten around to doing it. But Im asking this question because i had a good tune with 20psi and no knock and it was cool. Then it started lagging like this for no reason so I redid my tune with alittle more boost.

And as far as my mods...my list isnt up to date ill update it now. but i have all supporting mods for my injectors and turbo. (fmic, walbro255, fpr, full 3'' exhaust, evoIII exhaust manifold)

....so for now i should just play it safe and downtune or what?

 

[DJYoshaBYD]

definitely until you kill that knock

 

[4BangerV8Killer]

.....killed

 

[PieEyedPiper]

Please post another log including TPS, otherwise that was great info.
Also, make your log a WOT pull in 3rd from 2500rpm to redline (if you feel safe and are confident your tune won't grenade your engine, I won't make that call for you, 6600 will also suffice for just some trouble shooting).

Looks like you're getting timing pulled for one reason or another (*cough* knock) at 5grand and up.
Your timing would make more sense if we could see your TPS, cause I'm not 100% sure when you mashed the gas.

Let us know!

 

[4BangerV8Killer]

alright ill post it later tonight

 

[4BangerV8Killer]

im using mmcd to log and i cant find a reading for tps but yea i got rid of the knock and got some more timing up top but cant seem to figure out why my power is lagging so much im gonna try and turn up the boost alittle and see if i can keep from knocking then ill repost a new log.

i have another question too. on my WOT runs should my fuel trim be at 135%? or 100% if so on the 100 how do i fix that i read the faq on it and it was a little confusing so if someone could explain that.

 

[4BangerV8Killer]

i did a compression test and i have 170 across......so i now have no idea what would make my power lag!!!

and i have really bad blowby and idk why cause it seems that my rings are fine....good compression and no oil on my plugs

 

[exile]

Dude the knock is making your power lag and you're going in the wrong direction. It should be obvious to you if the more fuel you add the worst the knock gets. Soooo... try taking it out?

I have a feeling if a wise man posted right now he'd probably say set your boost lower and start your tune all over.

 

[4BangerV8Killer]

i re-tuned and get no knock....and have no account for my blowby