Power Issue

[scheffler]

Ok I am haveing a issue with my motor. I feels as if it should be makeing more power.

What hapens is I will be driveing and the turbo will start to spool and I can feel the power and then its as if it reaches a point and wont make any more power like something is restricting it. It will pull hard from like 2800 to 3800 rpms or it will start to pull hard then it kinda just stops. I hear what i think is the WG open. I cant hear that nice high rpm sound of the turbo i hear what sounds like a big release of pressure and it is at that point when it wont make any more power but it will hold boost fine wont drop or spike. It will rev fine, idle fine.

The timeing is set to stock with a enthalpy tune. I am running 10 psi on the turbo and it will hold 10 psi no drop or spike even when it feels like it is not makeing power. NGK spark plugs gaped to .036 right now have varied the gap from .030-.038 with no changes I have a msd blaster coil and 6a ignition system. I have a z32 MAF on the cold pipe blow through setup. T3/T04E turbine .63ar compressor 57 trim. 3" dp with 3" exahust all the way back. Oil press is about 65-70 psi while under load. EGT about 1300 deg WOT. AFR is 14.6 idle. about 11.8 to 12.3 WOT. I have my BOV to the atmosphere and my WG dose not go to the DP is is atmosphere aswell.The motor is fully built botom end 8.5 comp, forged pistons rods ect............. it is all done. Not really any head work, ported and polised on the exahust side thats it, the rest is stock. 550 cc injectos top feed. AMS fpr set at 45psi. walboro fuel pump. I still am running a 240sx fuel filter plan on upgrading very soon( dont konw if that is the problem), but i have had this car running good at one point with this filter before i serged my turbo, Oh the turbo and Mani is new less than 500 miles on it

I am at the point where I dont no what to try next to fix this problem. It is not just me my brother and my frien have rode in the car and both said the a same thing.

If you guys have had this problem or have a idea please let me know this is driving me crazy If you need more of a explanation let me know.Thanks

[WDRacing]

Intercooler coupling disconnected?

[neverlift]

first off that was a good description, and I know cause all mine suck...

anyways what bov are you running? is it adjustable, maybe the pressure release is from a weak spring.

is this a dohc motor? I assume knock sensor is enabled on that tune? hows it pull above 6k ish? kinda sounds like something is chiming in to say whoa!

[scheffler]

IC pipeing is good checked that a couple times.

yes DOHC dont know much about the pull over 6K cause i dont take it that high when it runs good i will shift at 6K but right now i will shift at about 4500. Yes knock enabled but it is just the factory sensor. Bov is a generic one plan on upgrading but funds are low right now. I have checked the spring and it dosent seem to have been weakend. I all so added some washers just to make sure that it seals. I am not sure if it is adjustable but like i said i can add washers if i need to.The WG is a generic / tial knock off with a tial spring set at 6 psi and I have a MBC to take over that. It holds a steady 10psi I mean it is rock solid.

You are right about something say whoa but i dont know what.

[scheffler]

I wouldn't think the BOV would be releasing the pressure but maybe the WG. That is my best guess right now, but i have also cheecked the WG and the spring and they seem to be good. I dont have a gauge to test the functionality of the spring to see if it is weakend but like I said it holds a steady 10psi.

[480sx]

I mean if your holding boost well, and it sounds like you are, you might not have any issues.

From the description of your EGT's, and AFR's your engine is running great.

It sounds like your just experiancing the peak levels of TQ and expecting that to follow all the way to redline. With stock cams, you will feel a loss of Tq after 3.5-4.

I bet getting cams would fix your problem heh.

[scheffler]

well shi t thats good i guess but i dont understand why it ran great with my other turbo t3/t4 .48 ar 50 trim only problem i had was the stupid Boost designs manifold breaking and causeing my turbo to surge, but i didn't have this problem.

is that maybe do to the size diffrence of the turbo? The one I have now is bigger but it is not like going from t25 to t3/t4.

[WDRacing]

If anything a bigger turbo will pull harder up in the rpm band. Do me a favor and look closely at the plug wires. If one is chaffed through or damaged it will wreak havoc. I had that issue on my 240, took a week to figure it out cause it was a very small abrasion, but it was enough to ground out the wire.

[scheffler]

Ok I will check them out and let you know. I am at work so i will have to check them after.

[scheffler]

Ok WD so I checked spark wires and they looked good then i sawped them out with a second set that I have and no bueno. It didn't change anything.

Any more Ideas?

[scheffler]

OK so this weekend i took off my WG and BOV took them both apart cleaned them and I extended my WG dump tube. but they both looked good and I checked my IC pipeing again. could find anything wrong with those parts so i dont know.Any one got any more ideas?

[WDRacing]

Maybe you're getting to much timing retard on boost? Knock sensor could be faulty.

[Florida240sx]

Hey WD anyway to bypass the knock sensor say if it's faulty? Fake a signal to it or leave unplugged? Knock snesor will mess up your car at idle correct? Only time it doesn't affect is WOT correct?

[scheffler]

well I guess that is posible i will have to check it out. It is a reletively new knock sensor like maybe 5000 miles it is the stock sensor but newish. Can they go bad that quickly?

Also ^^^^^ if that is possible I would love to know to try to trouble shoot.

Thanks guys.

[s13rb25det]

what size walbro fuel pump do you have? is it the 190 or 255? you might be loosing fuel pressure at higher rpms.

[s13rb25det]

also did you say you changed from a smaller turbo to a bigger one? is the tune you have for the smaller turbo?

[WDRacing]

Just disonnect it, it will throw a code but WGAF...

[scheffler]

255 lph fuel pump.tune is for the new biger turbo.

WGAF? sorry not to good with acranims.

[redhb240SXS13]

WGAF= Who Gives A F***Of course I'm just assuming that's what it means, I could be wrong.

[scheffler]

well it makes sence and it fits so I can go with that.I will try it and let you know.

[scheffler]

Ok working on the car tonight so i will let you guys know what happens.A quick ? is it possible that i am just not geting enough air? That when i hit that certain point my air flow cant keep up. I know that it seems not likely cause i am not running that big of a turbo but I know that if you dont have air you dont have power.What do you guys think.

[WDRacing]

No

[scheffler]

HaHa. Yeah I thought not but thanks for clearin that up WD.

So last night I pulled the knock sensor and nothin. I checked my IC pipieing for leaks again nothing. Checked timming and it was at like 18* btdc ( I guess that it looked like 20* when I set it last) so I put it on 20* the car still has this issue but it seems to run a tad better. I mean that it feels a little closer to how it should.

I still get this pressure release that i can not explain. I will try to get a sound clip and post it up, what would be the best way to do that?

[WDRacing]

record it, post in on youtube

[scheffler]

Ok I am having some trouble geting a clip on youtube (no device to record with)but any way I think that the noise is comeing from a leak in my WG return into my down pipe block off plate. It is the one where I had my WG dump back into my DP (previuos setup, I really hate boost designs). Could this be causeing my problem? If my AFR on based on exauhst gas and it is not reading all of due to a leak then my AFR are incorrect most likely running rich? That could be why It feels like it is missing power right? I will fixing my leak this wekend just wondered what you guys think.

[drape123]

Hey man, first off, are you running stock fuel pump? I assume fuel is good since you say you're in the 11's on the wideband when it happends.

heres something to try 3500-4000 is the powerband where max torque is made and where spark blowout is more prone to happen. try gapping your plugs down to 0.25 and see if that helps.

if that doesn't do it, maybe we can get together since you live in san deigo. I can hookup consult and find out whats goin on in the ecu.

also have you tried resetting the codes on the ecu? if you have a maf error stored on ecu, it will create all kinds of funky problems.

[scheffler]

No I am running a walbor 255lph fuel pump.

I will try gaping the plugs t0 .25 and let you know what happens. I will reset my ecu as well.

Thanks I will keep you posted.