Blowing flames out the tail pipe...?

[Batmobile_Engage]

Okay, I know this isn't very important in the whole scheme of things, but I've wondered
about this for a long time and it's making me crazy.

Why do some cars shoot flames from their exhaust with NO anti-lag, NO launch control,
no flame throwing exhaust modification, etc....?

I've seen numerous videos, many are of STIs and EVOs, blowing flames between shifts
or even just while sitting still, revving up and bouncing hard off of the rev limiter.

I've looked at the driver's list of modifications, and they are practically the same as mine.

So what gives? Originally, I thought they must be running catless (which they are, and
so am I) AND have a super rich tune. Though, some of the videos I've seen of this happening
are of very well tuned cars, making butt tons of power on the dyno. I'm going to guess
that these guys are NOT running a super rich tune, because they obviously aren't retarded
if they're making that kind of power.

JJ and a few of the other guys say they shoot flames periodically. Sooooo....why don't I?

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(Check out my member journal if you want to see listed EXACTLY what mods I have)

 

[finallymysti]

Maybe it hs something to do with how hot the down pipe gets?

 

[HolyCrapItsFast]

Sometimes it is not enough to just be rich but to be rich during shift and overrun. Some tuners actually tune performance oriented cars this way to allow the engine to maintain fuel during turn in when you are off the gas. This way when you are ready to come back on the gas you have less of a lag between the time you command fuel and fuel actually begins to come back. Otherwise the injectors will simply shut off and then come back on when fuel is commanded. Backfires are usually a byproduct of that situation and the idea is that it accumulates unburned gases in the exhaust during overrun and when EGT's are low. Then as the car resumes normal operation, the gases are ignited by the incoming exhaust pulses and the higher temperatures that are associated with them.

You can achieve this simply by adding a VTA BOV and doing a little bit of counter tuning to make it safe to run. Or there are tables that you can adjust that are related to overrun that you can use to lengthen the amount of time overrun enrichment occurs.

There are other methods you can use if you are not using the stock ECU. For instance with an AEM EMS you can choose not to employ deceleration fuel cut off routines which will maintain enrichment during any deceleration condition meaning the injectors will never shut off.

It would also help to remove any resonators in your exhaust.

Regardless I can't say that I would ever recommend anyone do this on purpose. For one it is illegal in just about every state and backfires are never good for the turbo because of the pressure waves it creates in the exhaust. Over time it can eat away at your thrust bearings. but you have to do it allot for that to happen.

 

[35r]

Hah, well that explains why i have a welding torch for an exhaust sometimes.. Haha

 

[Batmobile_Engage]

Hmm....now that you mention it about overrun fueling, I'm thinking I might not have quite enough
fueling during overrun (not for the sake of throwing flames, but for driveability, you'd understand if
you drove my STi).
Since I know we have the e-tuning service here, how difficult would it be to take my tune and just
tweak those parameters?
Especially when I am shifting from 1st into 2nd, it's almost like there is that slight delay in fueling that
you were describing. As soon as you mentioned it, a light bulb went off in my head so to speak, like
"ohhhh maybe that's what the deal is..."

 

[HolyCrapItsFast]

My guess would be that there is an issue with the tune. In almost every case you would never touch the overrun tables unless you have an express need to do so. Sounds like you just have some drivability issues that need resolving and we can certainly take a look at it if you like.

Hmm....now that you mention it about overrun fueling, I'm thinking I might not have quite enough
fueling during overrun (not for the sake of throwing flames, but for driveability, you'd understand if
you drove my STi).
Since I know we have the e-tuning service here, how difficult would it be to take my tune and just
tweak those parameters?
Especially when I am shifting from 1st into 2nd, it's almost like there is that slight delay in fueling that
you were describing. As soon as you mentioned it, a light bulb went off in my head so to speak, like
"ohhhh maybe that's what the deal is..."

 

[Batmobile_Engage]

Cool cool. I'm about to finish up work for the day. I'll get back to you on the tune when I get a free minute. Thanks buddy! :tup: