Diagnose this Misfire

Give input on tuning as well as any tips and tricks you may have. Also feel free to share base mapping files for various engine types.
Rob Stevens
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Diagnose this Misfire

Post by Rob Stevens »

My K series Elise started misfiring as in bap bap bap at a regular frequency at bang on 4000 rpm, it would drive through it and then clear up and run just fine until you hit 4000 again.
Set up as follows.
Sequential on, using injection angle map and had been running fine before this started.
Issue disappears when in batch injection mode
Nothing special on the crank or cam errors, perhaps 30 cam errors after 5 trips
Starting fine.
Worse at full throttle than part.
Not a wiring fault or interference
Crank scope fine even when misfiring
Launch, traction and shift cut all off in SW
I recently changed to larger injectors
Lambda working ok
Nothing of interest in the logs

I found the issue last night and thought this would be good for a bit of armchair diagnostics :)
SMR
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Distributor: DTA
Location: Aberdeen

Re: Diagnose this Misfire

Post by SMR »

What's the coil dwell like? Could it be just marginal when in non-sequential, then showing it's limitation when in sequential?
Only other thing I can think of - some sort of interference thats only there on sequential?
Rob Stevens
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Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: Diagnose this Misfire

Post by Rob Stevens »

No, dwell unchanged as I still use the same double end wasted spark coils, so only sequential fuel not spark.
Not interference and cam and crank scope fine.

Keep trying :)
SMR
Posts: 137
Joined: Tue Jan 16, 2018 9:38 am
ECU Model: S100 Pro
Distributor: DTA
Location: Aberdeen

Re: Diagnose this Misfire

Post by SMR »

If nothing else has changed bar the larger injectors, perhaps something to do with fuel pressure? do you run double injectors - is the change-over point at 4k?

I'm stumped! Any clues? / hints?
Alex DTA
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Re: Diagnose this Misfire

Post by Alex DTA »

If it runs fine in batch injection, it's something to do with the injection.
I can't think of anything that's RPM related in sequential injection, so that points to the injector angle map.

No idea what though.
stevieturbo
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Re: Diagnose this Misfire

Post by stevieturbo »

Is 30 cam errors not a lot ?

Why do you mention a recent change to larger injectors ? How recent ?

And is not uploading the map a clue that it was a config problem ? lol

Whether IDT or Inj timing as Alex suggests.
Alex DTA
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Re: Diagnose this Misfire

Post by Alex DTA »

30 cam errors is nothing. You'll usually get one or two on start up
Rob Stevens
Posts: 1247
Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: Diagnose this Misfire

Post by Rob Stevens »

See Alex is the man and I only stumbled on the problem. The injection angle map had become corrupted somehow. the map had the -prefix missing from 4000rpm onwards so it was jumping from -270 deg to +270 in an instant therefore missing a complete power cycle. hope this map corruption thing is just a one off
SMR
Posts: 137
Joined: Tue Jan 16, 2018 9:38 am
ECU Model: S100 Pro
Distributor: DTA
Location: Aberdeen

Re: Diagnose this Misfire

Post by SMR »

Well sussed!

I have another strange one;

I use the "Pit lane speed limiter" set to RPM as a limiter for tyre warming (Otherwsie I always seem to hit my soft limiter as the engine revs up so fast).

If I'm in the paddle shift window, if I try to change any parameter, I get a warning along the lines of "pit lane limiter already in use". Before I can F4 any changes on the paddle window, I have to disable and F4 the pit lane limiter and then go back and F4 the paddle window, and then switch the pit lane limiter back on. Strange as I'm not using that input for anything else?
Alex DTA
Posts: 1622
Joined: Fri Feb 28, 2014 1:03 pm
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79

Re: Diagnose this Misfire

Post by Alex DTA »

Steve, that's a bug in the software.
I'll fix that shortly.

Rob, that's unlikely to be corruption, but more likely a bug in the upload/download somewhere.
Please can you send me an email with a correct map, as well as either an incorrect map, or a description of where the minuses went missing?
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