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Missfire under load and no boost

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attached pc log file and map

Rb20de link extreme g4 ecu, standard everything 25det turbo.

Misfire underload, running very flat elsewhere and will not boost above 5psi if it can get there.

Have looked over everything and can not find a fault.

Plug standard ecu back in and shes perfect.

Has 10psi spring btw.

Any ideas?

map and logging

Attached Files

Mixture overly rich and / or ignition components not up to the task.

Calibrated your timing propperly with a sparkplug wire between your coil and plug for timinglight pickup?

Are you sure you are missfiring? I cant really see it in your log.

What i do notice is that you are very carefull. At least in this logfile.

At the max RPM you have (4850`ish) you are at only 30% throttle.

At your max throttle (70) you are only reving to 3554 rpm

Not sure when you expect your boost to come on. Do you have a boostcontroller on it?

Yea even when I turn master fuel down its still same if not worse. And is running perfect on stand ecu with rich ratio under load down to 12afr on gauge.

Yup checked base timing multiple times with ht lead. Yea it takes forever to Rev, running very flat and slow. During that run there was 100% throttle. I expect boost nearly straight away as thus is what happens on standard ecu.

No boost controller.

And is defiently a misfire reving it up. Driving feels like a ecu cutting, as splutters and spit's and real slow.

There is a plug by factory harness that connects to last 3 injectors and a cold start valve. Unplugging last 3 injectors and reving engine there is no miss what so ever but flat of course because no fuel. I find that very strange?

Well then you must have posted the wrong logfile.

There is no portion of this one where you are over 70% throttle.

Neither is there any missfires. Not showing up on the RPM trace and no lean spikes on your AFR line. A missfire will show up as a lean condition.

Your timing numbers seem low though so that could contribute to your "slow" engine.

Also are you sure your ecu are hooked up correctly regarding the cylinders firing order. They are configured ok as far as i can see, but are they wired up to the right places? You can check it with your injector and coil test function in the ecu.

I attached a screenshot of your file

Attached Files

ok so found a setting while engine running was injector setup, peak and hold table or something, injector 5 and 6 were different to rest, so made same, and holy shit what a improvement half throttle pulls right to redline without a issue, full throttle still same issue! have attached a pc log to help.

Yes injector and ignition is wired correctly

And I'm not meaning slow as in not enough advance slow, I'm meaning slow as like I'm towing a truck and we going nowhere slow! Along with backfires and splutters.

Thanks Matt

pc log

Attached Files

If everything is stock as you state your injctorsettings will need to be "saturated". Thats for high ohm injectors. Peak and hold is for low ohm injectors.

I still canf find any definite proof of missfires so im gonna put a dime on the thing i CAN find. Timingscatter. Try applying a filtering to the triggers. Its set at default now. It is confusing that this should be your problem as everything is stock (?) and it should work fine. But just humor me and see it it changes anything. There are triggerdisks you can swap out your stock triggerwheel (inside the CAS) with. I recomend you do that regardless.

Can try bumping coil dwell up a notch also. Try 2.5 and see if that leeds anywhere. Also strange if it does as you are almost not boosting at all


Not sure what your setup is, have you fitted an RB25DET engine into an R32 that was running an RB20DE?

The RB20 and RB25 have injector wires 4 and 6 switched around.

When fitting an RB25DET into an RB20 wiring loom you have to switch the injector wires 4 and 6 around, as you say the misfire disappears when you unplug the extra loom that feeds cylinders 4, 5 and 6 I wondered if this was a part of your issue?


Might be a bit off the current train off thought but could be a blocked catalytic convertor.

Will make the car asthmatic.

If you haven't got the option to pull it off and test, if you pull the exhaust off after the turbo, pour water down your exhaust and it should not fill.

If you have the tools and the port you can do an exhaust back pressure test between the turbo and cat.

Running excessively rich whilst setting fuel up early on can melt a cat pretty quickly.

Exept op says its ok with the stock ecu. Im inclined to think Mobile over here might be on to something though...

OK I will have another look at injector setup and trigger filters. I think I have played around with filtering and the car died. But will have another look.

And yea I have herd of that, but on standard ecu it's perfect?

My engine is a standard rb20de in r32 with standard wiring loom. I have attached the a and b link loom into standard harness to be able to run extreme stand alone and factory ecu.

Have plus t the engine using 25det turbo. Still on 20de injectors, jut for interest to see when they max, I know it's getting close looking at duty cycle.

Have no cat. And engine performs fine on standard ecu.

Will get back later after amother test today.

Thanks everyone!!!


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