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Mark 1

Launch Control Help

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I'm having trouble with backfiring though the intake when using launch control. its set up using fuel cut on a turbo V8 with no trans brake so can only hold on the foot brake at around 2500rpm. It starts backfiring as soon as the boost starts building.  I've tried adding fuel up to the max of 50%.  Might need main table adjusting for more?? at the moment im pulling timing down to 7 deg. adjusting it doesn't seem to make much difference. The fuel cut limits all over the place. could be a result of the backfiring or maybe the backfirings a result of unstable limit?? Bit unsure of what direction to head

 

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Is this sequential injection, i.e. 1 injector in each port?  What’s the manifold design like?  It sounds like you have some lean combustion events but you shouldn’t have any combustion with a fuel cut in theory if it’s done right.  I’m thinking maybe charge robbing or something.  Log ang map might help too.

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Yep it’s sequential. Manifold is a open plane edelbrock victor jnr. Like a carb manifold in design. I thought I did upload map and a log. I’ll have to have another go tonight. I was wondering if it might be lean due  to the main map. Obviously it’s never been tuned at that lower revs at that higher boost. But chucking in 50% extra fuel should of helped that 

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Heres a log and map. map is still a work in progress. the last log is the best ive managed to get it.

When I first started setting up launch I had it on spark cut and even then I used to get the odd inlet back fire. same if I hit any hard Limits it inlet back fires. 

V8.pclr

launch.llg

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I dont see anything glaringly obvious but have a couple of thoughts:

  1. There's not many parameters logged so there may be more clues if you could do a PC log with all parameters recorded.  It would be nice to see at least, ign timing, dwell, inj PW etc...
  2. Your fuel load source is set to "Off".  This means there is no MAP compensation done in the background which will make the fuel table more prone to error with changes to MAP, this could possibly explain the situation if it is in fact a lean misfire.  This will need the whole fuel table re-tuned if you change to load = MAP. 
  3. Update to the latest firmware.
  4. I think lowering the start cut will help smooth out the limiting effect as it looks like it doesnt need much limiter.

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ok ill change start cut and also do full log next time I have it out. As for the Load set to off. When it was first tuned the tuner turned it to map and it run rough and was all over the fuel table so he turned it back off. and tuned from there. It was a link dealer that tuned it so I never gave it another thought. Is it something that needs addressing? 

Thanks 

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21 hours ago, Mark 1 said:

Is it something that needs addressing? 

It just means your fuel table will be more sensitive to changes in manifold pressure.  I cant see how turning it off would have improved anything.  Im unsure if that is related to your problem, but just something that is not typical so I mentioned it.  I would start with a better log before you go changing anything too drastic.

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Yep not sure either. had a quick muck around with it tonight. Changed it to load= map and all I had to do to make it happy was change the master fuel up. it has to go back on a dyno so will get it tuned properly when it does. Ill leave it off for the time being and do some logs in the weekend. 

On a separate issue I downloaded the latest PC link version but when I connected to the ECU it shut it down and had a warning that the ecu is locked and to contact link for a code. I had to down load the previous version to be able to connect again.

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4 minutes ago, Mark 1 said:

On a separate issue I downloaded the latest PC link version but when I connected to the ECU it shut it down and had a warning that the ecu is locked and to contact link for a code. I had to down load the previous version to be able to connect again.

Yes we are just learning there is a problem with that over the last couple of days.  It seems to be if you connect the new 5.6.6 PC Link to an ECU with older firmware.  5.6.5 is stable if you wanted to update that far, otherwise, please hold off for a couple of days until we fix it.

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I see that the rotary option in launch control cuts both spark and fuel is it worth trying it in that mode? if it would work and not hurt anything. If it was charge robbing could that eliminate the back fires?

 

 

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I would not recommend the rotary cut mode as it will do funny stuff on 4 stroke otto.  With a rotary engine there are 3 combustion chambers per rotor.  So fuel is injected into one chamber then the engine does two full revolutions before that chamber is ready for spark.  So the rotary cut mode takes this into account in how it limits, it has to cut fuel 2 cycles before it cuts ignition then when the cut is finished it injects fuel into a combustion chamber for 2 cycles before ignition is re-enabled.

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