Rb25det Problem

[isijappanisi]

Hi

When i was at the dyno pack a couple of days ago, we encountered (is that how i should write it..? -norwegian member) a problem with the engine.

The engine mods are:

-new exhaust manifold with ext. wastegate

-tial 38mm wastegate

-Garret GT3076R A/R 82

-Greddy 1.5mm headgasket

-HKS timing belt

-FMIC

-GTSlink ecu

-3" exhaust incl. elbow

-Nismo 555cc injectors

-walbro 250 fuel pump

This is a gen. 1 engine (1994)

The engine works fine at lower revs (got 1bar of boost at 3000rpm), but when we hit about 6700rpm the engine just looses all power. and the highest rpm we got was 6800rpm.

We checked the spark plugs, coils, a/f, boost and ignition timing. The only thing we could see was the a/f going richer from about 5000rpm, and when we got to 6700rpm it goes way to rich. tried to lean it out, change the ignition timing without any luck.

The rpm limit was set to 7500rpm, but the engine rpm was neve near that.

when driving, the engine cut feels like the car suddenly braking, there is no shooting from the exhaust or misfiring.. the engine power just disappears..

The engine has only been driven 70000km since new from nissan, and was pretty much standard before i started tuning it.

So i'm wondering if anyone has had the same problem, or if you got an idea of what the problem might be?

Hopefully i can get this sorted out.

Thanks

Stian

Edited July 2, 2007 by isijappanisi

[mambastu]

Hi

When i was at the dyno pack a couple of days ago, we encountered (is that how i should write it..? -norwegian member) a problem with the engine.

The engine mods are:

-new exhaust manifold with ext. wastegate

-tial 38mm wastegate

-Garret GT3076R A/R 82

-Greddy 1.5mm headgasket

-HKS timing belt

-FMIC

-GTSlink ecu

-3" exhaust incl. elbow

-Nismo 555cc injectors

-walbro 250 fuel pump

This is a gen. 1 engine (1994)

The engine works fine at lower revs (got 1bar of boost at 3000rpm), but when we hit about 6700rpm the engine just looses all power. and the highest rpm we got was 6800rpm.

We checked the spark plugs, coils, a/f, boost and ignition timing. The only thing we could see was the a/f going richer from about 5000rpm, and when we got to 6700rpm it goes way to rich. tried to lean it out, change the ignition timing without any luck.

The rpm limit was set to 7500rpm, but the engine rpm was neve near that.

when driving, the engine cut feels like the car suddenly braking, there is no shooting from the exhaust or misfiring.. the engine power just disappears..

The engine has only been driven 70000km since new from nissan, and was pretty much standard before i started tuning it.

So i'm wondering if anyone has had the same problem, or if you got an idea of what the problem might be?

Hopefully i can get this sorted out.

Thanks

Stian

The standard ECU rev limit is 6800 on the 25, are you sure that you have raised it ok ?

[Links]

What ECU are you running, as said above the stock ECU redline is 6800rpm..

[isijappanisi]

as mentioned above in the mod list, i'm running GTSlink ecu. and the rev limiter set to 7500rpm. even tried to set at 8000rpm, but the engine still wouldn't rev over 6800rpm. can't figure out what's causing this. might be a faulty GTSlink.. but the again, if the ecu was going on rev limiter, it doesn't feel like a rev limiter, the rpm just goes slowly down and up.. not like a rev limiter..

Edited July 2, 2007 by isijappanisi

[TTT]

what AFM are you using?

with that sort of turbo, the stock AFM will be no use to you as it does not hae the resolution at much power over 200rwkw.

[Devils_Advocate21]

i was going to say afm, how you explain it hits rich then mega rich, also means possible max out of AFM, that could be one down side as you should have a relative easy 300+rwkw combo there (boost dependant) more info? have you got a dyno graph of current state afr's to power at least they should have given you that with it make sure afr to power is logged

Cheers

A

[isijappanisi]

hi, and thank you so much for the replies. the GTSlink doesn't use afm, it's replaced with a 3bar map sensor. so that can't be the problem either.. i might get my hands on the dyno graf, try to get it scanned and posted here.

and the turbo is a Garrett GT3076R with a/r .82, ext. wastegate.

[MBS206]

How much boost are you running?

Does the GTSlink only run one rev limiter? There's no soft limiter? No boost cut? No flat shift limiter?

When it hits the "rev limit" (What you're currently experiencing) is it like a miss fire?

If it's getting richer and richer, why don't you try leaning it out? ( by rich I'm assuming you're talking 10:1 or 11:1)

[GloriaShield]

check your ignition-coils.

[isijappanisi]

We were running only 1bar of boost, i was supposed to bring up the boost when mapping on the dyna pack, but never got that far due to the rev limit problem. as far as i know the link is only using one rev limiter. when the rev limit occurs it doesn't misfire, it only looses power, feels like braking when driving.. rev goes slowly down to about 6700rpm and up to 6800rpm again and so on.

we tried to lean it out, but the total power loss at 6800rpm was still present.

and i have checked the ignition coils, even tried coils from another skyline wich works as it should, but still the same problem with mine.

[Adriano]

Are you still running standard cams and valve springs? Maybe the lifters are pumping up. As said, why dont you lean it out if its going rich, thats what tuning is.

[RB30-POWER]

im going to say its the link, had similar problems before.

no i didn't solve them, just sold the ecu's...

[isijappanisi]

Are you still running standard cams and valve springs? Maybe the lifters are pumping up. As said, why dont you lean it out if its going rich, thats what tuning is.

Yes, i'm still running standard cams/valve springs. and as i have mentioned a couple of times before, we leaned it out, but the problem didn't disappear. the power curves on the dyno graph goes straight down when hitting the rev limit thing..

also thinking of the link is the problem, i have tried to contact link support to get some information.

[isijappanisi]

here's the dyno sheet from the first run.. couldn't get the one with the a/f curve, but you can see the power and torque. still haven't fixed the problem..

Edited July 4, 2007 by isijappanisi

[zebra]

Valves bouncing?

or the ECU doesnt know what the hell is going on

[isijappanisi]

Valves bouncing?

or the ECU doesnt know what the hell is going on

is valves bouncing a common problem on these engines? and how does the car behave on the road when this occurs?

[discopotato03]

Another one to look out for is running the air filter beyond its capacity . If you can temporarily tap into the inlet system just down stream of the filter with a compound gauge it would tell you for sure . Once a filter imposes a flow limit nothing you can do to the ECU rev limit wise will help . It just means that atmospheric pressure can't push enough air through the filter and you get a pressure drop in the system .

When power falls off does manifold pressure take a dive ?

Cheers A .

[isijappanisi]

Another one to look out for is running the air filter beyond its capacity . If you can temporarily tap into the inlet system just down stream of the filter with a compound gauge it would tell you for sure . Once a filter imposes a flow limit nothing you can do to the ECU rev limit wise will help . It just means that atmospheric pressure can't push enough air through the filter and you get a pressure drop in the system .

When power falls off does manifold pressure take a dive ?

Cheers A .

got a brand new HKS "mushroomfilter", the biggest one, so airflow should not be a problem, running it straight to the turbo with 4" straight pipe.. and the MAP is steady all the way.

[isijappanisi]

problem solved, must have been the exhaust cam causing the whole problem. Last year when working on the engine, the exhaust cam broke in two pieces, got a used one from a friend of mine. Anyways, recently ordered and installed a new set of tomei poncams, and suddenly problem solved! I can't really figure out what the problem was with the used cam I got from my friend, can't see anything wrong with it. have you guys got any ideas?

Going to the dyno at the end of this month, with my new tomei poncams, greddy plenum and GT3582R turbo, hoping to get a better result than last year, hehe..