Installed Turbotech Mbc, Missfiring Under 13-14psi Boost.

[Hakai]

Hey all,

First off, I have search for this particular problem and can't find a proper answer, so I apologise if I'm asking old questions, I just couldn't find a good clear answer.

I installed the TurboTech boost controller and fiddled with it and got ~14psi set and took it for a good hard drive. It was missfiring at wide open throttle. My first thought was my plugs, which were NGK Iridiums, heat range 5 1.1mm gapped factory (I'd set them to 0.8mm though). Today I bought new NGK Coppers of 7 heat range and 0.8mm factory gap. Installed them and went for a drive. Missfire is for the most part gone, but still there under high load + wide open throttle. (Example: Wide open throttle + going uphill, straight line doesn't happen generally that I could tell)

Basically I've put this down to the fact that while the stocker setup is good for 200rwkw (Or so most people on these forums say), perhaps my coils/igniter are just a bit old and aren't handling the boost even on the new plugs, or my fuel pump might not be doing so well. I can't afford to replace them with an 040 Bosche and a regulator or a set of splitfires just yet, so rather than drive with possible missfire when I give it a bit, I've turned the boost back down to ~12psi, if it keeps doing it, I'll drop it back to ~11psi where it was running fine.

I was just looking for some educated input as to what/why I might be getting this problem. It's obviously not -just- plugs, since they are new now, and are the right heat range/gap for my application (again, according to the threads I've dug up on here). Am I right to assume my coils/igniter are just showing their age, or possibly the fuel pump, are there tests I can do to the components to find out which it is? Am I barking up the complete wrong tree and is it a common problem that is easily and cheaply fixed?

Thanks in advance. Sorry again if I've asked something that's been covered, but I couldn't find any good clear answers.

Regards,

Ben.

Edited June 2, 2006 by Hakai

[Cubes]

Get it on a dyno and ensure its not leaning out.

Especially if your running the stock pump. If you can't afford a new pump its simple.. either drop it on the dyno and setup boost safely or don't push your limits as you WILL be up for a new motor if it is leaning out, chances are it will be if the pump hasn't been replaced.

So its $100-$200 to setup the bleeder on the dyno or $200 odd for a small bosch pump and install it yourself. I know what I would do but that really depends how much research you are willing to do. Anything can be Accomplished with research.

My stock pump died a few years back when trying to push more than 12psi, went mega lean, couldn't really tell. Which is why old fuel pumps are so dangerous.

There is a thing called a lean miss-fire, all though you generally notice det. well before that.

Failing all that.. Coils, which are expensive.

[Hakai]

Get it on a dyno and ensure its not leaning out.

Especially if your running the stock pump. If you can't afford a new pump its simple.. either drop it on the dyno and setup boost safely or don't push your limits as you WILL be up for a new motor if it is leaning out, chances are it will be if the pump hasn't been replaced.

So its $100-$200 to setup the bleeder on the dyno or $200 odd for a small bosch pump and install it yourself. I know what I would do but that really depends how much research you are willing to do. Anything can be Accomplished with research.

My stock pump died a few years back when trying to push more than 12psi, went mega lean, couldn't really tell. Which is why old fuel pumps are so dangerous.

There is a thing called a lean miss-fire, all though you generally notice det. well before that.

Failing all that.. Coils, which are expensive.

Thanks for the fast and direct reply

A lean missfire? Does it -feel- any different to a normal missfire. The missfire I'm currently getting feels exactly the same as the one I had last week that was caused by an almost dead coil pack and consequently damaged plug in #5. It was fixed with a new coilpack and a regap from 1.1mm to 0.8mm on all the plugs.

As for hearing detonation, I have alot of cabin noise, due to a few old rubber seals and most of all my short shifter, which is all alloy, even the housing the ball joint thing sits in is alloy, and makes a hell of a lot of noise, so hearing it would be almost impossible compounded by the fact I don't know -exactly- what to listen for. I'm not experienced when it comes to listening for detonation, when it's happening will there be a performance decrease, is the noise loud?

And which would you do, dyno and setup the bleeder properly (My guess), or take a chance that it's the fuel pump and go with that before a dyno? If I go the dyno route, how many hours am I looking at for the guys to run it up, give me a few power runs with a/f readings at the current boost level then eaither raise or lower the boost to a good compromise point between power/safety for the engine?

Sorry for all teh questions. Just my nature I guess. I'm a firm believer that knowledge without understanding can be dangerous, so I like to understand why something is, not just that "it is". Can get annoying when people try to explain things to me heh

Regards,

Ben.

[Cubes]

I doubt a lean missfire. I should not have mentioned it.

Almost always a missfire is caused by incorrectly gapped plugs or buggered coils and occasionally a stuffed ignitor.

If you have a lot of cabin noise its even easier to hear detonation, detonation is what you hear from little old lady cars when they labour the motor pulling out of a corner.

Chances are its a coil... get them sorted then I personally would simply drop a fuel pump in it and wind 14-15psi in to it.

It will be plenty rich everywhere, probably a little too rich and will kill power slightly.

The reason I wouldn't throw it on the dyno and push the std fuel pump to the limit is it is old, as it gets older its gets lazier so will eventually lean out.

On the dyno... 30mins should do it all though they will most likely charge you an hour. Really depends on the workshop and how they treat their customers.

[Hakai]

I doubt a lean missfire. I should not have mentioned it.

Almost always a missfire is caused by incorrectly gapped plugs or buggered coils and occasionally a stuffed ignitor.

If you have a lot of cabin noise its even easier to hear detonation, detonation is what you hear from little old lady cars when they labour the motor pulling out of a corner.

Chances are its a coil... get them sorted then I personally would simply drop a fuel pump in it and wind 14-15psi in to it.

It will be plenty rich everywhere, probably a little too rich and will kill power slightly.

The reason I wouldn't throw it on the dyno and push the std fuel pump to the limit is it is old, as it gets older its gets lazier so will eventually lean out.

On the dyno... 30mins should do it all though they will most likely charge you an hour. Really depends on the workshop and how they treat their customers.

Thanks once again for the quick reply

I won't worry about the lean missfire anymore, I promise :S

Plugs are brand new as I stated in the original post so is there any way for me to easily determine if it's a coil or a stuffed igniter? When I eventually get a set of splitfires, do I get the coils/leads/igniter or just coils?

Regards,

Ben.

[MKDR33]

check ur coil packs, its a common problem..

this might help ---> http://www.skylinesaustralia.com/forums/in...howtopic=119403

[sinistaGTR]

i had similar it was spark plugs.....

[Cubes]

You said you gapped your plugs down.

Didn't do what I did once... Accidently put a hairline crank in the ceramic?

I had the plugs in and out 3 times before the crack was big enough that I noticed it.

So check the plugs next time they are out.

[Hakai]

You said you gapped your plugs down.

Didn't do what I did once... Accidently put a hairline crank in the ceramic?

I had the plugs in and out 3 times before the crack was big enough that I noticed it.

So check the plugs next time they are out.

Nono!! The plugs are brand new. My -old- plugs were Iridiums that came 1.1mm gapped, I regapped -those- plugs to fix the other missfire I had, before the boost controller. They started to miss again when I installed the controller and upped the boost, so today I replaced them with BCPR7ES NGK plugs, 0.8mm gapped from the factory.

Sorry if I didn't explain it too well.

Ben.

[Hakai]

check ur coil packs, its a common problem..

this might help ---> http://www.skylinesaustralia.com/forums/in...howtopic=119403

Great thread!! I'll give that a shot tomorrow, thanks

Ben.

[QRI05E]

ITS NOT THE COILS or SPARK PLUGS!!!! Thats your fuel cut defender!!! stock ECU wont let you boost past 13 - 14 psi... anything above 10psi is risking blowing ur turbo...

Cheers

[Hakai]

ITS NOT THE COILS or SPARK PLUGS!!!! Thats your fuel cut defender!!! stock ECU wont let you boost past 13 - 14 psi... anything above 10psi is risking blowing ur turbo...

Cheers

The general consensus from everything I have read and everyone I have spoken to is that the RB20DET with standard internals and standard ceramic turbo is safe to run daily at 14psi, obviously providing all items involved are in good condition to begin with. I -have- heard that the safe limit for an RB25DET setup is around the 10psi mark due to them having higher compression, and something about the boost pressure reading being plumbed into the wastegate actuator from the inlet manifold just before the throttle body, as opposed to the RB20DET taking it directly from the compressor housing on the turbo. Much better for the life of the turbo I believe.

Regards,

Ben.

Edited June 2, 2006 by Hakai

[QRI05E]

Yes you are right however the RB25DET takes its boost line from the intercooler piping... Moving on, your symptoms sound like a fuel cut defender 100%... if it were your coils, you would get misfire at even 10psi... besides why would you want to push your turbo to the limit? run it a t a safe 12psi...

Cheers

[mad082]

i think he has an r32 not r33. so 14psi is fine, and i don't think the r32 have boost cut, but not 100% about that.

Edited June 2, 2006 by mad082

[QRI05E]

My Bad...

[Hakai]

Yes you are right however the RB25DET takes its boost line from the intercooler piping... Moving on, your symptoms sound like a fuel cut defender 100%... if it were your coils, you would get misfire at even 10psi... besides why would you want to push your turbo to the limit? run it a t a safe 12psi...

Cheers

Intercooler piping is a more simple way of saying what I said The section of piping I was referring to is the one that the factory BOV bolts on to, it's still a section of intercooler piping, it's just the one right before the throttle body Part of the inlet setup, so we're talking about the same thing.

From what I have been able to find out, missfire issues related to spark plugs/coils and the like are not as clean cut as "works or doesn't". The general rule with electricity is that it will always follow the path with least resistance, so I can think of two situations that come to mind immediately that could cause it to missfire at say 14psi but not at 10psi.

1) At 10psi with my given turbo, you have a CFM of airflow. Obviously with the same given turbo at 14psi that airflow will be higher. The coilpacks/plugs may be able to adequately spark under the CFM or airflow forced into the chamber at 10psi but as the airflow increases it may reach a point where the plugs/coils can no longer provide adequate spark and as a result, the increased airflow "blows out" the spark before it jumps from the electrode to the earthed tip of the plug. The plugs/coils aren't necessarily faulty, just not up to the task, in my case if this were the problem I'd put it down to age, as brand new stock items should handle 14psi fine by all accounts.

2) This is the one that relates to electricity following the path of least resistance. If you have a damaged coil pack, say with splits in the side of the body, like some have posted pics of here, then you have a secondary outlet from which the spark can jump to an earthed point. Obviously this won't occur unless the path through the cracked housing to the block (earth) is less resistance (work) than travelling to the point of the plug through the electrode. At lower RPM (And possibly lower boost, higher boost increases pressure in the chamber obviously, I'm not sure if higher chamber pressure creates higher resistance between the electrode and the earth on the spark plug? Anyone?) the route through the electrode to the earth is less resistance (work) for the spark, but as the RPM (And possibly boost?) increases the resistance from electrode to earth on the spark plug increases, so the spark starts to jump to the alternate earth, because it's less resistance than going through the plug. (Please correct me if I'm wrong someone)

And as a last thing about the fuel cut defender, I have heard about it, but I've also never read/heard anything about it cutting in before 16psi. I could easily be wrong, but that's about all the info I can find.

Not trying to be a smartarse and say you're wrong or try to make you look bad, I just like to asses all my options before I make a decision. Right now my decision is to boost back to 12psi and leave it there until I can afford to replace my coils with splitfires, get a Bosche 040 pump, fuel pressure regulator and a full injector clean (the kind where they take them out of the car, duh).

As for pushing it to the limit, I've owned my car 7 months now, the only mods I've done in that time are the FMIC, BOV and Pod filter. Just fitting the FMIC gave me a boost pressure increase to ~11psi once I got all the pipes tightened up correctly with no leaks, it was running about 9-9.5psi when completely stock. It had a 2.5" catback when I bought it. I've been doing -alot- of reading, talking to anyone I know who knows anything about RB20's and the conclusion I've come to is that 14psi is safe. My plan was to run ~13psi to be absolutely sure.

Regards,

Ben.

*EDIT*

I'm not trying to sound like I know it all, or alot, or anything for that matter. Just putting the thoughts I have on the missfiring under boost issue out there. It's all based on what I have access to read and the limited access I have to talk to people in the know, so I might very well be wrong. Writing it out like that also helps -ME- to better understand how -I- think on the topic and gives me a chance to have people who -do- know, critique and correct the way I think, so please don't take it the wrong way.

Edited June 2, 2006 by Hakai

[MKDR33]

i cant run more then 16psi neither, i get a boost cut.. anything under 16psi should be ok(with the stock or similar size turbo)..

Edited June 2, 2006 by MKDR33

[Cubes]

Your definitely on the mark with the theory.

The reason I mentioned hairline cracked spark plugs is when I did it the car idled perfectly and even boosted perfectly up until 5000rpm where it developed what felt like a slight flutter/miss, it held that flutter/slight miss until around 6500rpm where it all of a sudden cleared up and pulled strong again.

I cracked the spark plugs by using a swivel trying to work around not removing the cross over pipe.

So in some respects it can feel like what I have experienced with stuffed coils when running too much boost. The BIG give away the coils are stuffed is it usually appears fine when cold then as the engine bay warms up the miss on boost becomes much much worse.

[Hakai]

Your definitely on the mark with the theory.

The reason I mentioned hairline cracked spark plugs is when I did it the car idled perfectly and even boosted perfectly up until 5000rpm where it developed what felt like a slight flutter/miss, it held that flutter/slight miss until around 6500rpm where it all of a sudden cleared up and pulled strong again.

I cracked the spark plugs by using a swivel trying to work around not removing the cross over pipe.

So in some respects it can feel like what I have experienced with stuffed coils when running too much boost. The BIG give away the coils are stuffed is it usually appears fine when cold then as the engine bay warms up the miss on boost becomes much much worse.

Hahah! Awsome, I did the exact same thing when I overtightened #1 when I first bought the 32 and put the Iridiums in. It did exactly what you described, except my miss kicked in really low in the RPMs, around 2500, the crack was far from hairline though

I got it replaced from where I bought it, which I was both stoked and surprised at and all was well.

Anyway back to present day. I Dropped my boost to ~12.5psi, only a -tiny- missfire evident very rarely, I'm gonna give the valve another 1/4 turn and then leave it at that, should be somewhere between 11.5-12psi I'm guessing. I need a reason to not drive it hard anyway, can't save money when my right foot keeps spending it now can I

Thanks again to everyone for the advice and patients

Regards,

Ben.

*EDIT*

Cubes, thanks for confirming my understanding of the coil/plug theory. It's good to know that the time spent researching isn't in vain. A bit of confirmation that I'm heading in the right direction makes me wanna keep going heh. Cheers.

Edited June 2, 2006 by Hakai

[Hakai]

Just an update guys.

Removed all coil packs and plugs this morning, taped up the bottom and top exposed areas of the coil pack housing. All but 1 of them had what looked like blue/yellow electrical burn marks on various parts of the housing, the one that didn't was the new one from the wreckers. So they all got a good solid taping.

Another thing I noticed is that these plugs have a different washer on them to other plugs I've used. It kind of looks like the washer is 2 parts in one, and the outer part crushes down onto the inner part to create a kind of anti vibration lock. I hadn't tightened them nearly enough, so they all got a good tightening after I checked them for hairline cracks

All in all, boost back at 14psi seems to be running perfectly. It's not cold atm, so in cold in might do it I don't know, but I'm not gonna find out, time to drive her nice and easy and save some money

Thanks again everyone.

Regards,

Ben.