I have a 2ltr pinto with zx9 carbs and megajolt , with the standard mech pump i was getting BIG back fires on over run so , i was told it could be down to over fueling so fitted zx6 pump but i still have the same problem, i know it could be the timing but how do you time an engine with an ECU, cheers.

sounds like you might need more advance. Backfiring is caused by unburnt fuel igniting out of the combustion chamber on the exhaust side.

This happens when the exhaust side gets too hot as a result of the combustion happening too late in the cycle and the exhaust valve is starting to open before the combustion process is finished.

It may be over fuelling but more advance would still help.

Sorry no idea how to change the timing with MJ though

Cheers

Mark

quote:

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Originally posted by roadrunner
I have a 2ltr pinto with zx9 carbs and megajolt , with the standard mech pump i was getting BIG back fires on over run so , i was told it could be down to over fueling so fitted zx6 pump but i still have the same problem, i know it could be the timing but how do you time an engine with an ECU, cheers.

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Sounds like a mapping issue to me.

I think you need more advance on high vacuum/low throttle openings. Without sufficient advance you will be firing straight down the exhaust on overrun.



As has been said, post a copy of your map and let us know if it is TPS or MAP.

As I am only down the M180 in Epworth if you come over one weekend I will happily plug the laptop in and tweak it for you.

[Edited on 20/11/06 by TangoMan]

hi brad ,i would also check the inlet manifold and rubbers that attatch carbs to manifold as it could be sucking air in.

Hopefully this is the map .
[img]3dmap[/img]

Try again , if this does'nt work it's in my archive.

Here you go:


megajolt map