Miss fire at 0.4 boost...??? lol

[antrosser]

Hey guys, this is annoying me and need some help as (supposed to be) getting the car mapped up tonight.

Ive been having mapping sessions and each time its developed a miss fire at 0.4 bar of boost. Sometimes it was ok and did not missfire however.

I have just replaced the coils for aftermarket AEM ones hoping that would be the cure....still missing.

Its got new HT leads, new spark plus, I have just removed the alarm system to eradicate any problem with that.

Im at a loss now. Earthing problem perhaps???

Any help would be grear. Cheers guys.

[Brett]

What is the build specification of the car?

I\'m no expert - but we\'ll need more details of the running gear, fueling, engine management etc.

[m1tch]

HT leads the correct way round?

[antrosser]

It runs smoothly up until 0.4bar of boost...then miss fires. Could this be down to incorrect ht lead postions?

Ok here is the spec...

340lph Aeromototive fuel pump
1600secondary and 850cc primary injectors
t4 master power turbo (t76 I believe although not entirely sure)
AEM smart coils
water injection (Although this is currently not working)
large street ported engine
apexi ecu with commander
3bar map sensor

prob a few bits more but you get the gist

[m1tch]

Have you checked all the hose clamps etc? You might find that under vacuum and up to 0.4bar its all sealed but as the boost goes above 0.4 bar there might be an air leak somewhere meaning the engine isn\'t getting the air that it thinks it is, what does the wideband O2 say with regards to the AFRs?

[antrosser]

That is a good question...I dont have a clue lol. I am getting it mapped later so will ask the tuner and get back to you on that

[m1tch]

That is a good question...I dont have a clue lol. I am getting it mapped later so will ask the tuner and get back to you on that

So you are running a lot of extra fueling and a much larger turbo but don\'t have an AFR gauge?

[fil_auto]

have you changed the exhaust, OOI?

[antrosser]

Yea have a straight through 3" exhaust but no afr gauge :/

[fil_auto]

Yea have a straight through 3" exhaust but no afr gauge :/

Am sure Ben / Mav will look at that for you.....

What i meant is, have you changed the exhaust system recently, poss that\'s the cause.... as in there\'s poss a blockage, causing a restriction!

i say this, as i\'ve just changed to a much quieter pipe myself ( awesome - RE-A Dolphin tip ) but summat is not right... i think there\'s a blockage and it\'s causing a restriction, therefore not allowing me to boot passed .5 bar! Poor!

[antrosser]

You sure a mouse hasnt crawled in and started setting up home I have the changed the back box to a nurspec but shouldnt be restricted. We cured the misfire at 0.4 bar but not have a slight one at around 1bar lol. No winning

So if I put a silencer bung on the back to quieten down, does that mean it will affect performance?

[m1tch]

You sure a mouse hasnt crawled in and started setting up home I have the changed the back box to a nurspec but shouldnt be restricted. We cured the misfire at 0.4 bar but not have a slight one at around 1bar lol. No winning

So if I put a silencer bung on the back to quieten down, does that mean it will affect performance?

The engine is NOT mapped with a silencer, you need to keep the car as it is when it was mapped, if you want to run it with a silencer you need to get it remapped due to the different exhaust flow.

[BlitzBoy]

PUT IT ON A DYNO FFS  , dynos are very good tool in finding where the misfires happen in the rpm and boost , helping to see if its a fuel problem or ignition, troubleshooting on the road mapping is sometimes a useless exercise, doing things on the cheap sometimes bites you in the ass