flying banana

iTrader: (1)

Is it worth having over fueling on overrun to get some pops and bangs when getting mapping done.just a bit of fun

boosted

Is it overfueling? IE a rich mixture? im not so sure. I think there is more to it than that, my old car was 10:1 on overrun and didnt make so much as a fart. Ive seen cars pop when you map them lean on the overun however. prehaps ignition timing retard has a lot to do with it.

Tidgy

it just adds a bit of fuel extra in the over run for pops and bangs (aka when you take your foot off the throttle), it doesn't alter afr etc, also doesnt do the damage antilag does.

Up to you realy, my old car was epic hahaha

GazJenno

Normally when you lift off and are on overrun the ECU switches off the injectors completely so no fuel is used. They turn back on when the RPM falls below a certain threshold set in the map, partly to help prevent the car stalling. The threshold where the injectors turn back on on mine was set to 1200RPM and obviously before this point the AFR goes through the roof as its just pumping air alone.

I have set my injectors to come back on at anything below 5k on overrun and it does make it pop and bang alot with a 3inch full decat system when hot. AFR's in that region vary from 14.5-13:1 depending on how far up the rev range I am.

It does use ALOT more fuel when driving normally in my opinion with the threshold set that high and I wouldn't suggest doing it unless you can switch it on and off as you please... an Apexi with hand commander allows you to change it as you go along.

Gary

brendy76

iTrader: (6)

There was me thinking it was retarded timing that did it.

GazJenno

Mainly a hot exhaust, no cats or silencers and a little unburnt fuel. However people have been known to try and drop the timing under no load conditions in the hope the mixture ignites as the exhaust valves open... not tried it myself.

http://www.paulr33.com/powerfc-faq/powerfc-faq.htm#71

Gary

brendy76

iTrader: (6)

It works and does not need a hot exhaust neither.

GazJenno

I'd say you still need the injectors to come back on at higher revs for that to work though, other wise you have no fuel to help... other than residuals.

May have to try it with both for a bit of fun.

Gary

brendy76

iTrader: (6)

The bangs are quite loud, you just dont get as many flashes as you are using a reducing amount of fuel left in the chambers. Coasting down with minimal pedal you get a lot until you come under the revs you have set on the rom for negative timing. I have mine set to 3k rpm as any less means it can happen when town driving which is a pain.
This is my wrx after sat idling for around 1-2 mins. fast forward half way into it.

GazJenno

If your coasting down with even a slight amount of throttle I believe the injectors will come back on anyway so I guess thats a way of controlling it without having to change the injector decel RPM. The un-resonated, de-cat exhaust plays a big part in letting the pops out I'd think.

So do you actually have a negative value for ignition timing? or just zero advance.

Gary

brendy76

iTrader: (6)

I have set my first load column to 0.2 load (second column 0.3 so it has quite a limited function) and from revs 3000-5400 I have 0.04 deg pos timing.
To be honest, you can do it from around 5 degrees positive down into negative figures though I found as close to zero has the best effect.

GazJenno

Ahh ok, apexi only allows whole numbers zero upwards for timing.

boosted

I've mapped several cars, a extra fuel on overun doesn't make pops or bangs, and does effect afr

neil-h

I'd have said so. My GB270 pops a little bit but its only really noticeabl at a stand still, although hearing that video makes my inner child want a de-cat.