Unfixable Miss

[SimonR32]

Ok so i have a RB20 and wanting to run over 300rwhp with 20psi

I was stuffing around with coilpacks for ages trying to fix a miss but eventually gave up and have upgraded to a falcon coil pack.

But the miss is still there, even with a 0.55mm gap it still misses a fair bit under boost. When the boost is turned up to 18/20psi it misses of virtually all cylnders.

I have a Power FC and my tuner played around with the coils settings with datalogit but to no avail. I have changed coils/plugs/ignitors etc etc many times and none make a difference

I got my hands on a hand controller a few weeks ago and as the revs got towards the top end (when it starts to miss) the volts dropped on the hand controller read out (14.4 down to 13.2). My friend has a very similar setup to mine so i did the same on his and it stayed a constant 14.4v through the rev range.

So i changed the alternator to see if it was the problem, once again with no luck. Now im going to change the alternator belt as i have been advised that it may be slipping with revs but if this does not work im as a loss of what to do.

does anyone have any ideas about what could be my problem?!?

any help would be appriciated

thanks simon

Edited January 30, 2006 by Cerbera

[Cubes]

14.4 is a little high for a warmed up motor.

Generally 14+ is acceptable for a cold motor however once the motor has warmed it will drop to approx 13.8v.

Mine under full load at high rpm will drop to ~13.3v.

I don't have any issues with coils breaking down.

But.. I'm not running any where near as much boost as you.

What plugs are you running?

[rob82]

What kind of timing numbers are you running and is your base timing correct? Try adding a couple of degrees and see what happens. Check for little white track marks around the boot also.

[teejay]

Missing rings allowing pressure through Simon

[Cubes]

Only missing under high boost ppls...

I assume your running the correct heat range copper plug?

[rob82]

Like I said what timing numbers, if the ignition is overly retarded then you will generate a miss as the combustion event will be under more load since the piston is closer to the top of it stroke hence more combustion pressure. And also what plugs?

[pnblight]

for you to be drawing some nuch current in the electrical system to drop the voltage like this you must a serious issue in the electrical system(it may not even be related directly to the ignition system but is related to rpm).

It might be worth checking the supply wiring to the ignition system poor conducts can brake down under load but still supply an electrical path when not stressed, plus the voltage you reading on pfc make be quiet different to the volt the ignition system is recieving

CHECK THE WIRING LOOM(as it could be a simple as bad supply wire)

[Sydneykid]

My suggestion is to do a leak dow test to eliminate rings, pistons and valves as the cause. In the old RB20DET we were running 225rwkw (302 rwhp) at 19 psi on standard coils and copper NGK's at 0.8mm. So you are not looking at anything extraordinary.

cheers

[Butters]

Put a Garret turbo on it, I hear the Apexi's have an in-built miss. :lol:

I think PNB is right with check the loom too.

Remember it was coming up with ignition circuit fault on the consult.

Which generally is not the cas.

[grim32]

I had something similar happen, my problem was the dwell time on the coils. Increased charge time helped but reducing discharge time worked better. We set charge at 2.4ms and discharge at .6ms.

[SimonR32]

ok to answer some questions...

i run bcp6es and bcp6e and they both are the same, might get my hand on a set of bcp7es and try them?!?

base timing is around 15 deg and the timing is a few degrees off pinging top end like a good proper tuner should do (around 13-15)

we did put more timing in on dyno but it just caused pinging and knock count was getting on the high side of just under 60

the power running to the ignitor was checked at idle but not under load... may have a check of this again under load

the rings/pistons and valves are assumed to be fine as there is virtually 0 blowbye from the engine plus the fact that the miss goes away if the plugs are gapped low enough...

plugs come out with all normal markings of a good working engine, maybe a tad rich but thats for saftey

grim32, i may give this a try. i shall talk to my tuner, datalogit is used to adjust correct?!?

[Amaru]

While it may not directly help your issue, make sure you check the real simple things.

I had a similar miss, only showed up under high boost. We replaced ignitors, coil packs, spark plugs so many times it wasnt funny. 4 months later we had it on the dyno (because I had been too lazy to get it properly checked) to try and solve the problem when my mechanic noticed under large boost, an injector o-ring was being pushed up slightly... enough to cause a leak and cause the miss.

An $0.80 part caused 4 months of pulling things on and off of heartache.

[Cubes]

Interesting Amaru... Definitely worth kicking your self.

I've just replaced all of mine..

---

Recently did a comp test also... 153psi exactly across ALL cylinders, 30,000k old motor.

[proengines]

While it may not directly help your issue, make sure you check the real simple things.

I had a similar miss, only showed up under high boost. We replaced ignitors, coil packs, spark plugs so many times it wasnt funny. 4 months later we had it on the dyno (because I had been too lazy to get it properly checked) to try and solve the problem when my mechanic noticed under large boost, an injector o-ring was being pushed up slightly... enough to cause a leak and cause the miss.

An $0.80 part caused 4 months of pulling things on and off of heartache.

<{POST_SNAPBACK}>

That caused some serious hair pulling. If you have the car on the dyno have a good listen around the intake manifold, Nik's car made the slightest little whistle and it was only #6 injector that was leaking but caused a really bad miss. It's well worth a look.

[BHDave]

Your problem sounds very similar to mine when i installed external coils.

The car was fine off boost, ok up to about 5psi at partial throttle but as soon as i put my foot down i would experience what i could only describe as complete ignition breakdown. No acceleration at all and it happened instantly.

Long story short, i checked everything except the coils (as i bought them new and had seen the exact same model work perfectly on a CA and SR), swapped cas, upgraded fuel pump, ecu swap, ignitor swap, pulled the injectors and cleaned them, replaced all filters, the lot, no change.

In the end out of desparation i wired the stock rooted coils back in and the car was instantly better (but still far from perfect), so i ordered a set of splitfires, installed them and haven't had an issue since.

I think the problem will most definately come down to the coils. If it can be fixed by adjusting the dwell and firing time, great. If not then it may be worthwhile swapping in a set of stockers for a test.

[grim32]

grim32, i may give this a try. i shall talk to my tuner, datalogit is used to adjust correct?!?

<{POST_SNAPBACK}>

Yeah just talk to your tuner about how to do it, on the wolf its straight forward.

My car seemed to breakdown on 17psi at around 6-6500rpm, that was with standard coils. Put a new set of splitfires in and same problem. New plugs 7 heat range i think gapped to .6 and still no change. With charge time set to 4ms the problem disapeared, but was concerned about burning the coils out. So we set discharge to .6ms (it was 1ms before) and this allowed us to bring the charge time down to 2.4ms.

[RedDrifter]

What sort or afr's are you running?

Could be caused by a two rich or too lean mixture.

Silly question I know but I thought it miht help.

[SimonR32]

11.8 afrs top end

going to have a play today with loom and check everything...

then will try and change charge and discharge times of the coils as grim32 suggested

[N I B]

Falcon coils use around 3.5ms charge and 0.6 discharge time.(Not sure the PFC will do that)

If your using EF Falcon coil packs then its waste spark and the discharge finds it easyest path and at higher boost thats the plug thats not under compression so it will miss,If your using 6 Falcon coils the Nissan module wont be upto it.

Many ppl run upto 30psi on stock coils so there must be a problem with the coils-ignitor-wiring if they miss fire under load.

[SimonR32]

both stock coils and the falcon coils have exactly the same problem...

and its not a single cyl that is having a problem, it is all of them with the same problem