Not your average misfire

[e1_griego]

I haven't done any diag yet on this, mostly just soliciting feedback from people who have been around the block.

Motor is:
SR with w/ 3k miles on rebuild
9:1 CP pistons and Manley rods
New JWT s3 cams with stock valvetrain
New oil pump, gaskets, bearings, etc
GTX2867
PowerFC tuned by Martin @ Enthalpy
740cc injectors (cleaned/tested 3 months ago by RC Engineering)
Z32 maf


Alright, so the car rips. Not hiccups, no boost leaks, no nothing. 20psi is feeling great.

However, if I tag the limiter in 2nd (it's an autocross car, it happens -- might do it in 1st but I haven't noticed it) the car loses one cylinder it sounds like. The 4th will clear up after 5-7sec.

The coilpacks are stock which means they're old. I'm guessing that's the problem, but mostly just seeing what other people think. I feel like if it was a mechanical issue I would have trashed the head by now since a sticking lifter at 7500rpm would cause bigger issues.

I'll swap out all my coilpacks before the next autox but just wanted to see what other people thought.

[jr_ss]

I'd definitely start with the tired ignition system. Swap an ignitor first and see if that changes anything. If not proceed with your plan.

[e1_griego]

Yeah I just bought a new new set of coil packs. I'll throw in an ignitor too and go from there.

[fatduece]

Hey Alex what coil packs did u buy?

[e1_griego]

A new set of OEM.

Not really looking to do splitfire stuffs.

[cotbu]

It sounds to me like your just hitting the hard Rev limit, might be wrong but that's my guess. Check the bin or contact your tuner, the soft Rev limit is 7500rpm the hard limit is 7600rpm. The tuner might not have changed this. You could easily over Rev an extra 100rpm. :cool:

Sent from a Highly Tuned Note 4.5!!!

[Kingtal0n]

I set my limiter in my daily to 6300rpm for ultra safety.

His car is not a daily though :D

[e1_griego]

This is an autox car. I don't see the point of funneling money and time with "racecar" parts into a car and then just driving it solely on the street.

I have a pfc and a datalogit. The limiter isn't set up any differently than it has been for 5 years now. Losing a cylinder for 5-7 seconds isn't normal.

Maybe the new coilpacks will fix it and I'll dig up a spare ignitor and try that too.

[cotbu]

I set my limiter in my daily to 6300rpm for ultra safety.

His car is not a daily though :D

I always raise mine, for safety! XD!

Losing a cylinder for 5-7 seconds isn't normal.
It is if you hit the hard cut on a powerfc, hard cut is ignition, soft cut is fuel!

If you have a powerfc log that shyyyyt!
You will definitely see ignition drop off, you might even see when and why.


Sent from a Highly Tuned Note 4.5!!!

[e1_griego]

I've been autocrossing and hitting limiter for years, never had that problem.

Weird that it manifests itself now. That's why I figured something was wrong. And losing just one cylinder instead of all?

[Kingtal0n]

I've been autocrossing and hitting limiter for years, never had that problem.

Weird that it manifests itself now. That's why I figured something was wrong. And losing just one cylinder instead of all?

a single cylinder drops when
it fills with fuel, or fuel cuts completely
the spark dies, or is too weak
it loses compression

Other exotic issues include golf-balls that only block the intake port for a few seconds

[e1_griego]

Yeah I understand what's happening.

The why is what I'm after, since this isn't a common thing.

[e1_griego]

Just in the interest of future searches, after replacing the coilpacks with new OEM and replacing the ignitor with a known good one that issues persists (though I went almost a whole weekend of hitting limiter and never had an issue except for one or two instances, so it's not *every* time.

Anyhow, I reached out to Martin @ RS Enthalpy who said he'd run across the issue before and that it's either the CAS or the PowerFC having a bad injector or coil driver.

I have another CAS on the way, though I'm guessing that it's going to end up being the PowerFC.

[TougeSR20Kid]

I had this same issue on my RB, cleaned the interior contact points of the coil packs and now it runs fine. I'd find it hard to believe its an issue with the injector circuitry. Does it sound like the vehicle hits an early limiter? Cus that's exactly what mine was doing

[e1_griego]

a) Car has a brand new set of OEM coilpacks
b) If you'll read, it's after I hit the limiter that I lose a cylinder

[bmxer882x]

possibly spark knock? Checked your plug gaps?

[daryl337]

No, any knock retardation from the ecu will affect all cylinders.

Do you have any sort of fuel trim on the cylinder individually?

Enthalpy knows their stuff - but I'd figure a bad injector driver would should it's face more often than just after hitting a rev limiter.

Let us know what you find!

[e1_griego]

No, fuel trim is set evenly across the board. PFC does allow fuel trim per cylinder but it's even for my setup currently.

PFC doesn't have any knock control.

Injectors were cleaned and tested by RC Engineering at the beginning of the year and received a clean bill of health.

I still can't imagine it's mechanical since the car hasn't shredded the valvetrain, but when I do the CAS I'll have the valve cover off so I can at least inspect everything.