Stoping backfires?

BraneDeadx · Post by **BraneDeadx** » Tue Jan 10, 2006 8:34 pm

Well with every time i drive my car now i get closer to fine tuning her in! which is great and all....

some the issues im haveing are when letting off the gas coasting in gear, i get some mean back fires...... nothing to intense just sounds like a old lawn mower back fireing hahe....

ive tried tuning my VE map in the very low KPA bins (30 or lower) so the amount of fuel is very minimal..... in datalogs i see im injecting maybe 1.5ish of fuel when coasting...... ive also in the ignition table made my advance in the mid 40's what not......

anyone have some advice on anything eles i can try??? i wish i can do a 100% fuel cut ,,,

Sean.....

WolfGTI · Post by **WolfGTI** » Wed Jan 11, 2006 6:24 am

What variant of the code are you using? MSnS-E can do a full fuel cut based rpms, kpa, coolant temp and time interval before it kicks in.

boost junkie · Post by **boost junkie** » Wed Jan 11, 2006 6:33 am

They call it "over run fuel cut". It works really well. Kinda freaks people out when you coast and the air/fuel goes way lean.

78Spit1500Fed · Post by **78Spit1500Fed** » Wed Jan 11, 2006 6:51 am

On a carburetted car, this is usually a result of the butterfly slamming shut before the primary/secondaries are switched over to the decel jets. Most use some method of keeping the butterfly cracked open for a second... like a tiny shock absorber.

On an EFI car, the same applies... there is still fuel being injected at a rate higher than that which the air intake will support. Some OEM's handle this by keeping the idle air control mechanism open when warmed up.

Adjusting your VE bins isn't a great way to remedy this, I'm afraid... some cruise MAP values can be as high as near-idle MAP values, and RPMs can be similar as well. Tuning those bins to cut fuel would cause some major cruise problems!

As WolfGTI and BoostJunkie have suggested, you need to tune your "overrun fuel cut" values, or if you're running the standard code, the "Decel fuel ammount". See Setting the Acceleration Enrichments for more information... it's about 4 paragraphs down.

-Brian

BraneDeadx · Post by **BraneDeadx** » Wed Jan 11, 2006 8:17 am

yeah im afread im running MS2.33 .... ive tried the decel fuel amount % in the accel wizard but that caues some problems when i let off gas to slow down but not let it off totaly (bucks little bit) ..... and ur right about trying to get the VE bins down in those areas there very close to the cruse area (30kpa) .... is there anythying eles to suggest?? i recently got a fix it ticket from a a**hole cop because when down shifting he said my exahust was to load (CVC 27151) notthing big i just got mail in a certificate to show its below 95db which it is (funny) but im sure the back fires are louder then 95 (pops a good one now and then) soundsl like m80s going off hjehehe.....

so ill figure something out , i should have a muffler between my downpipe and exahust

Sean,.,,