ECU tuning for crackle on overrun - theory?

[RyleyMA61]

I realise this is purely an aesthetic/rice/pointless aspect, but I care not; I don't like the 7MGTE's aural presence and I think a bit of crackle/pop/bang on overrun or decel would add a bit of welcome drama to the otherwise monotone engine note.

I'm running an appropriate exhaust system (virtually straight through) and a full aftermarket ECU.

I was wondering what is the theory behind getting a bit of exhaust drama?

Rich/Lean on decel?

Injector cut/no injector cut?

My tune is pretty rich at the moment and does cut the injectors on decel.

My std 2JZGE with a straight through exhaust used to carry on with bangs, pops, crackles and sounded somewhat brilliant...

Any ideas on how to get the 7M to sound a bit more dramatic?

Obviously a correct/healthy tune is more important - I'm not going to sacrifice that for sound...

[GT1978]

Disclaimer: I have no expertise in this area. Take / use this brain fart at your own risk.
Theory: On decel, richen every second cylinder to throw some unburned fuel into the exhaust which will mix a the collector with the lean (oxygen) mix from the lean cylinders. If this doesn't work maybe retarding the timing so there is an inforced ignition source in the exhaust.
Perceived problems: Burning out exhaust valves. Opening up exhaust Wyle E. Coyote style. Rooting up your tune and its associated issues (detonation etc).

Glen.

[maj]

Bee*R style to shoot flames out the exhaust and all the pop/crackle that goes with it is to retard ignition, fuel gets dumped into hot exhaust and flames ensue.

This is also a surefire way to ruin your cat FAST.
Youtube "Bee*R Flames" and you'll know what I mean.

[SHEPPO3930]

go into the fuel map and add fuel to the row where you have 0% TPS/0% load (add fuel from 2500rpm up to the rev limit). then turn off the "overrun fuel cut", so it keeps spraying fuel when the throttle is closed. this should get you close.

on my bike (YZF-R1, 115rwkw) the overrun fuel cut is disabled and it shoots flames and pops/bangs on decel.

[trdee]

most aftermarket ecus seem to crackle and pop and whatnot on the overrun, even with decel fuel cut enabled. nfi what does it though. residual fuel probably

[RyleyMA61]

on my bike (YZF-R1, 115rwkw)

<3






Thanks for your help mate!

[oldcorollas]

most aftermarket ecus seem to crackle and pop and whatnot on the overrun, even with decel fuel cut enabled. nfi what does it though. residual fuel probably

is just poor tuning...

or maybe they are tuning for "cylinder cooling"

[trdee]

note the part where i said even with decel fuel cut enabled AFR gauge is showing no fuel either, still gets a few burbles going, but nothing like antilag or whatever.

[andrew_mx83]

Yup add fuel and retard timing (lots)

You want the exhaust to have as few bends as possible. If you can see through from one end to the other you should get mad crackles. Crackles are also FTMFW.
As for the cat, one of those super-lightweight hi flow ones (you know what i mean) will help and not get f'd up from the air fuel explosions you are trying to create in the pipe.

[Cuzzo]

Yep go those unobtanium cats . With the honeycomb in the outside ....bin.

[oldcorollas]

note the part where i said even with decel fuel cut enabled AFR gauge is showing no fuel either, still gets a few burbles going, but nothing like antilag or whatever.

oh, i thought you wer emeaning tunable decel cut.. not just enable/disable.. my bad
gauge shows lean if is missing too, which is effectively what you want it to do

someone should send Tony ABbot a stern letter asking why he doesn't support mining licences for Unobtanium

[thechuckster]

my first Megasuirt ECU had a variable decel fuel cut fueling amount (when in decel mode you could cut the fuel by xx% amount until it hit the low limit for decel enabling, usually ~500rpm above idle for me).

If you want simple over-run cackle and the ECU allows it variable decel enrichment, just run it at over 100% - it will overfuel when you drop off the throttle and hopefully the ECU will have a decel fuel cut limit, where it reverts back to the normal map and stops any decel fuel cut/enrichment.

However, as you (RyleyMA61 ) have a turbo, this will lead to uberhigh EGTs and kill the turbo quick smart.

See if your ECU has anti-lag and rotational idle - that should give you the trailing throttle (and gear change crackle/bang) plus with obvious performance benefits. Tunable anti-lag (combines overfueling + timing retard + extra aux air), should also do the rotational idle and the smarter systems keep a running tally of anti-lag and rotational-idle activity and can tone it down or disable it when the turbo gets too hot.

[trdee]

there is a function like this on the adaptronic specifically for antilag, called "enrich/retard" can be enabled by a button or by variables such as speed and TPS position etc etc and then you can configure exactly how much fuel enrichment/ignition retard you want, along with throttle cracking if you have an idle speed controller etc. haltechs also have this function, as would most ecus I imagine.. although probably under different names

thats going to the extreme end of what i would be prepared to do just for a couple crackles to entertain me though. I personally would rather keep the exhaust wheel of my (very expensive) turbo intact instead

[RyleyMA61]

Alright, thanks guys!

Definately not worth it for the expense of the turbo! I think my present tune is rich and advanced, with a fuel cut on decel to save fuel.

I have to lean out all my no-load, light-load, medium load AFRs anyway, so will see after I get it running a bit better

Cheers guys!