I have this exhaust popping sound when I rev the engine in gear to say 6000RPM then release the accelerator and as the car decelerates I get this popping sound from the exhaust? can anyone help me with this issue? My wideband goes nuts when this happens so i cannot tell if it is rich or lean.

I've tried fuel cut on various settings. Doesn't help, perhaps ignition map?

Help someone. I'd like to finalize my fuel map and its the only area I have left which is difficult to recreate.

Air leak at the exhaust manifold gasket probably

air leak

edit: too slow

[Edited on 9/2/10 by tomgregory2000]

This is caused by a number of things, there could be a leak in the exhaust system letting in air , or the mixture could be to weak on the overrun bins or ignition does not have enough advance leading to unburnt fuel in the exhaust system or a combination of the above.
Paul

could be unburnt fuel you need to cut the fuel when the throttle is shut until the engine gets back down to about 1500 rpm
Ray

hmm, thanks as for the air leaks, can it be anywhere on the exhaust manifold from the head onwards or should I be looking and somewhere specific?

I'm running megasquirt, when the popping sound happens the lambda reading goes nuts

My bet is that you have overrun fuel cut turned on which almost completely cuts the fuel during the over run which leads to lots of popping and banging on the overrun.

What I do is turn this option off then control how much fuel cut i want on the overrun by reducing the VE table values.

I would go for around half what your idle value is, which will still give you a few pops but not too much. And set your overrun advance to about 40 deg.

Done that/tried already Ray

I'll re check all gaskets at this point.

ok cool try what flak monkey says he knows more than me
Ray

Thanks Flak, I'll try that method. Cheers.

Might not work for you, but it works for me

Is this noise bad? I love the sound of popping exhausts, and a bit of flame action!!

I agree with Flakkers. If I run mine with overrun cutout activated I can get some spectacular bangs and flames from the exhaust. You need to turn off overrun cutout and adjust the bottom row of VE bins to give you around 16:1 AFR on overrun so that the engine is still combusting. You'll also get better pick up when you touch the throttle again.

Sonds like its to weak on overun.Had mine rolling roaded and the last thin they did was get rid of the banging just by richening the lower bins up till it stoped.

Worked for me Mr.Flak just a little popping happens when over 4000 Rpm so its all good now.