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Loud backfire when opening throttle

drz440@live.co.ukdrz440@live.co.uk Posts: 27Verified User

As the title says, I’m having a problem with a loud backfire in the exhaust when opening the throttle from fully closed. It’s only happening between 6-7000 RPM though.

I have a 2017 R1, and I’m running the unrestricted map currently. My mods are k&n air filter and a de-catted standard exhaust, exup removed. I’ve also fitted AIS blanking plates.

I’m running active tune but only with a bench flash kit, so it has to tune itself every ride, which is fine as I’ve made a few edits to the base map to get it somewhere close, but I cannot get rid of this backfire.

Ive had this issue before when I first started flashing the ECU, but it turned out to be that I had the fuel cut enabled still, and it would backfire any time I opened the throttle back up, so I’ve tried richening the mixture this time, between 6-7000, but it’s not helped an awful lot. I have actually just started to advance the ignition timing in this area, which has helped greatly but not solved the issue completely. I’m worried about advancing too much though at this point.

Any advice would be greatly appreciated.

Many thanks

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Comments

  • jason@ftecu.comjason@ftecu.com Posts: 693Staff User

    Hi,

    On a liter bike with a de-catted exhaust you will have some backfire no matter what you do. In general if you try to tune out all the backfire your on/off throttle response will be awful. There are ways to mostly get rid of it but it's common for the modern day 1000s with exhaust systems.

    I would be careful adjusting ignition time too much on a stock motor. Mess around with your TPS and MAP fueling tables and make sure you link all 4 cylinders together too.

    Thanks,

    Jason A.

  • drz440@live.co.ukdrz440@live.co.uk Posts: 27Verified User

    Hi Jason, thanks for your reply.

    I’m going to try setting the ignition back to where it was and richen the mixture on the active tune.

    Its a strange one as when it’s cold, and I assume running on the base map, it doesn’t backfire. But after a mile or two, when I imagine the active tune is starting to kick in, it then begins doing it.

    The backfire I’m worried about isn’t the usual crackle/pop-corning on the overrun, it’s as I bring the throttle back in it sounds genuinely as if a shotgun has been fired.

    The ignition advance did seem to help, I added 4 degrees between 5,500-7,000 rpm. From closed throttle to 39%. How much would be too much to add?

    Thanks again.

  • jason@ftecu.comjason@ftecu.com Posts: 693Staff User

    Hi,

    Just going up 4 should be ok but I wouldn't recommend going too far that's all.

    On the Active Tune activation limits you can change at what point the Active Tune starts to work based off ECT, RPM, TPS, etc... that may be an interesting area for you to play around with. Seems strange the backfire would be that loud though, I'd say keep working on perfecting your map and see where you can get over time here.

    Thanks,

    Jason A.

  • drz440@live.co.ukdrz440@live.co.uk Posts: 27Verified User

    Thanks again Jason, that’s good to know with the ignition timing.

    I’ll definitely have a look at the activation point for the active tune too, under what heading will I find that, and which way should I go with the numbers?

    I assume that it will mean the active tune begins tuning sooner?

    Thanks again

  • drz440@live.co.ukdrz440@live.co.uk Posts: 27Verified User

    Hi,

    For anyone else having this problem I have resolved it now.

    I actually went ahead and fitted a bike side harness to make a base map, but the bike was still backfiring in the same way.

    It turned out to be related to my throttle mapping. In the zero throttle column I had the throttle so it was still open by 1.44% to reduce engine braking and to smooth throttle transition. Somehow this was causing the backfire, possibly overfuelling when I began opening the throttle?

    Anyway, it’s all fixed now and it’s smooth as silk.

    Thanks for your help though Jason, it’s nice to have the support of you guys at ftecu.

  • jason@ftecu.comjason@ftecu.com Posts: 693Staff User

    Hi,

    Glad you were able to look at some things and get it resolved. Enjoy the ride!

    Thanks,

    Jason A.

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