Missfire at low RPM

Hi lads,

So after having the car mapped at Racetech i got it back with a slight missfire around 1600-2000rpm, the issue is only on very light throttle

i was advised it could be an ignition component thats at fault so changed the rotor arm, inspected the Dizzy cap (both less than 3000mls old), swapped out the HT leads and replaced the coil and still the same issue, the plug gaps have also been checked and seem fine.

when doing a WOT pull the fuelling is spot on as per the AFR results from the dyno

could this be an ignitor issue possibly?

I have been assured there is nothing wrong with the MAP also

as part of the remap larger injectors were fitted, 450cc, and a 3'' exhaust system

if anyone could shed some light or suggest any possible checks that would be great
 

dac69er

Super Moderator
If it was ok beforehand and not now then it sounds very much like it is something they have done.

What has it been remapped with? If your confident enough to do so you could put it back to how it was and see if that cures the problem.
 
Mapped on emb, am not going into the map as engine Ecu and turbo kit is all under warranty.

Could it be tps? As the light throttle doesn't switch it and it messes with the map or something? Also he did say it was blowing the spark out at higher boost so had to turn it down, could this have something to do with it?
 

dac69er

Super Moderator
If it was ok beforehand Just disconnect it and run it on stock ecu. Put standard injectors back in and try that. If it's ok then you know it's something they have done.

Doesn't sound like it was a very good job if he knew about the tps problem and left it. What setup and boost are you running? I would doubt any setup using emb would cause the spark to blow out.
 

Rev

Member +
x2 It is a tricky rev range 1600-2000 I had a similar issue with a safc the map changed low to medium with too big a jump.
Also depending on setup closed to open loop changes around here and there is spool to consider.
 
was pushing close to 300bhp when it was blowing out the spark

its a bit far gone to be putting stock items back on to try so i think i may have to take it back and stay with him while he looks at it

as for the open/closed loops, that could be part of the issue, i could be pushing the emb to the limit as it does have 450cc injectors in also

its not a major problem as i say its just on very light throttle low revs

the rev counter bounces about when it misses, so is it safe to say it will be electrical rather than fuel related?

but it is rather fucking annoying :)
 
If it was ok beforehand Just disconnect it and run it on stock ecu. Put standard injectors back in and try that. If it's ok then you know it's something they have done.

Doesn't sound like it was a very good job if he knew about the tps problem and left it. What setup and boost are you running? I would doubt any setup using emb would cause the spark to blow out.

setup and boost wise its a forged engine hybrid td04 running 255 12/13psi

i didnt say the TPS has an issue just wondered if it could have something to do with it if it was faulty
 

Skalabala

Member +
Hmmm, maybe hook op an oscilloscope to the trigger and see what it does :/
What is timing and AFR at when miss fire is there?
 

dac69er

Super Moderator
i do have access to oscilloscopes so might be worth checking the injectors at misfire along with the coil ext

think your right dac69er, think ill take it back after checking signals
 
would you describe what you are experiencing as a slight hesitation/jerk at 1600/2000 rpm on light throttle??

if so, i have seen this happen with emu on a similar set up to yours....i'd suggest you look at the fuel and ignition maps in those cells using a map trace (not sure if emb has that feature)

turns out the stock ecu does not like a lot of fuel taken out at low rpm, below 2000/2500rpm while in vacuum/light load.....in lihg to using larger injectors and sometimes in trying to set a lean cruise afr, these cells maybe used to help pull fuel,,...sometimes too much fuel is pulled..,,then you end up with too lean a condition when the car is cold or warming up...i've observed that with the stock ecu it likes to run rich on cold start and warm up.....hence ecu and piggyback fighting kind of and that's the miss/hesitation/jerking right there

similarly, the stock ecu does no like a lot of timing added at low rpm...put those values close to zero or at zero in those few cells so the stock ecu has a bit of control over things in that area......also, avoid big jumps in ignition from one cell to the other over the rev range......try to make your ignition adjustments incremental and smoothe

i'm driven to believe that this is all to do with closed/open loop and the stock ecu wanting to run rich on initial start up and fighting with the emb/emu which is pulling fuel and/or adding ignition

once your outside the closed/open loop cross over point....then the emu/emb can have greater control

remember the stock ecu still has to be happy, especially at the lower rpm and low load areas


well that's what worked for us on two cars with emu
hope you understand what i'm trying to say...

i am NOT a professional tuner....i'm not a tuner at all
this is what we did with afr guage and dyi electronic knock cans....both cars work great

best to let your tuner look at the map and make any adjustments IF its the map

did you do a road test/drive after getting tuned?....or just a dyno tune?
its usually best to let the car cool down completely,,,restart and warmup and take a drive to verify everything is working good....as you may not encounter such a problem on a WOT dyno run
 
Sorry for late reply been on holiday

Yes that's exactly what I am experiencing, I bought the emanage intercepted injector values along with the ignition and fed different values to the standard ecu? I haven't seen the user interface for the emanage so couldn't comment on map traces or cells

I am a lead to believe it is the map so will be paying them a visit to go over what the have done and spot any potential mistakes

There was no road test just a dyno tune, as said the wot results are perfect
 
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