RB20 Misfire And Surging Power

[RB20ZED]

Hey guys bought a aussie r31 skyline with a rb20det coversion.
Now it has a misfire and surges under hard acceleration.
Its all fine runs super smooth and will drive smoothly no matter what rpm but when ur foots into it and on boost once it hits around 4-5k it starts to break down and misfire quiet badly. In the higher gears itl usually surge when on full boost. As for mods its just the std cooler zorst number but has a screamer pipe on it what shouldnt really effect it at all.
You guys have any ideas what it could be?

i have recently changed the plugs and cleaned all the coil packs and associated plugs and they all seem good.
I will be cleaning the air flow meter probably today as maybe the oil from the pod is effecting it.
The fuel pump as far as i could tell is a std na rb30 one and it seems that its been perminantly wired on so it runs flat out 24/7 and doesnt shut off when primed so im thinking maybe the rail pressure isnt good?
any other ideas guys and things i could check?

[ER33CTION]

maybe a boost leak somewhere?

[RB20ZED]

but would a leak cause a hard misfire?

[SLEEKA]

what ecu is it running? what boost is it running?

The stock ecu's are poo, 9/10 times they are the culprit, especially in skylines. As soon as they have a few mods ie pod, exhaust and more boost they break down and surge like a bastard.

I would look at the basics first it could be blowing out the spark, so check the spark plug gap, i would go as low as to gap then at .5

coils would be next in line for an ignition side problem, a nice set of splitfires would be good and they arent that cheap, around the 500buck mark.

Just from personal experience my younger bro has a r33 gtst, fmic exhaust and boost at 12psi. Missfired and surged like your describing. We changed the plugs and gapped then properly. Then he installed splitfire coils, it still surged and missfired. Then he bit the bullet and put in a powerfc, problem solved.

Another instance is with a r33 i have as a lil project on the side, it again has fmic, exhaust and boost to 12psi. It did the exactly the same thing as my bros, surged and missfired. I dont really want to spend to much money on this car so i just gapped the plugs, left the stock coils and just ripped out the boost controller and left it on 7psi. It no longer surges or missfires, and even though its not as "quick" it feels alot smoother and is a much better drive. Personally i wouldnt increase the boost until i get some sort of aftermarket ecu/tune, they are just a pig to drive otherwise.

Just a quick note, i dont beleive its the boost that knocks the computer around but more the increase flow of air that throws the maps of the ecu all over the shop since i have noticed with the above cars that would surge even if you werent at full boost ie holding it at 5-6psi throughout the rev range. A boost controller doesnt just increase the manifold pressure but it also makes the turbo spool up quicker than stock (as it holds the wastegate closed for longer) and i think this confuses the stock ecu

[RB20ZED]

runs 10psi as thats the lowest itl go.
hrm dont really want to spend massive $$$ on it seeing a power fc and splitfire coils would be worth half the car i dont really see myself doing it.
Umm did have my zed running 15psi for years with cooler zorst and pod with std ecu never faulted but hey who knows.
Might change the fuel pump 1st and see how that goes as i dont know id the rb30 is large enought.

[SLEEKA]

runs 10psi as thats the lowest itl go.
hrm dont really want to spend massive $$$ on it seeing a power fc and splitfire coils would be worth half the car i dont really see myself doing it.
Umm did have my zed running 15psi for years with cooler zorst and pod with std ecu never faulted but hey who knows.
Might change the fuel pump 1st and see how that goes as i dont know id the rb30 is large enought.

10psi is the lowest? Is that the lowest setting on a boost controller on it or is it the lowest cause it doesnt have a boost controller at all? Just wondering cause the wastegate actuator is normally about 7psi

You must of had a lucky zed, or maybe the fault im talking about only really effects rb25's who knows, but i havent stepped into a 33 gtst to date with simple mods w/ std ecu that hasnt surged.

Yeah that rb30e pump wouldnt be all that flash, maybe something cheap like a walbro would do you well. If you really wanna go cheap i have a gtst pump that has just come out of my bros car that i'm sure he will let go for lil price haha

[Passage GT]

yeah i'd try swapping the fuel pump first
get some quality german bosch goodness into it:)

[ben351]

owains got a spare one for sale !!

[Milhouse]

not anymore. pm ballstick.

[RB20ZED]

was thinking it could also be the fact that the fuel pump seems to be hard wired so it runs flat out all the time by doing this wouldnt you unsettle the rail pressure by always having alot of fuel running back into the return lines
or did that sound like alot of crap lol

[RRob]

There will be no "running issues" by having the pump hard wired. Only bad thing is if you have an accident.

Could be wiring issues..

Most probably fuel pump..

Tried pulling down the plug gaps?

[RB20ZED]

well il gap down the plugs tonight and try a few small things and while im at it might look for a pump