Well, I just spent the weekend at BeaveRun enjoying some track time with the Audi guys. While I was there the Evo managed to put on a good show not only by passing everyone in my run group but also by shooting flames whenever I shifted in the straights. Typically I'd pull out of turn 11 into the front straight in 3rd gear and run it up to redline through 3rd and 4th gears. On each shift flames would shoot out the tailpipe a couple of feet. Quite impressive but I'm sure it's what contributed to the 6mpg I was getting on the track.

Mod list:
Buschur Stage 3 w/ HKS 264/264 cams
Stock injectors/stock fuel pump
BuschurFlash/Dynoflash mail in tune
Running cat less at the time

Why am I shooting flames? My idea is that because my injector duty cycle is maxed out @ 100% at around 6500rpm that the fuel being sprayed on the back of the valves is lighting off when it gets sucked downstream into the tailpipe.

Ideas? I'm hoping that when I upgrade my injectors and fuel pump that the reduced duty cycle will get the rich condition on throttle lift under control.

 

Getting rich on lift throttle is normal, so is spitting flames on the track. You're running the car hot, so when it goes rich, the high EGT's will light the excess fuel.

Plus, it keeps people off your bumper.

 

maybe because you're running cat-less. I dont know much about it, but I've read that some guys running test pipes or cat-less are shooting flames outta their exhaust.

Nebo

 

awesome. how was beaver run? I heard it is a new track? was it a difficult track to run? I have a couple of guys trying to get me up there on an open day.

do you suggest going to this track? was it worth it. I am like 50 min away.

thank for you input.

 

It's exactly what he said. No cat = flames out your @$$

 

I dont have a cat, and I dont think ive ever popped any flames..haha.

 

Yeah, I'm with these guys. The fact that you had no cat is more than likely what was causing flames to shoot out your exhaust.

 

Haha, sounds like fun. Like to see a video of your pyro evo.

 

I was at Summit Point last weekend and my car was shooting flame when I lift and shift. I'm also running catless. I email Mark at TT who tuned my car and he said its normal. It's also because I told him I will be doing track events and he tuned my car a little richer to be safe, so unburn fuel got ignited in the exhaust. Looks cool though on the track but not on the bumper lol.

 

I pretty much figured running without the cat is the reason the flames are there this time out on the track versus my previous run down at VIR where I had no flames (with cat). I'm just wondering why I'm seeing enough fuel at throttle lift for there to be something to light off. Once I get my WBO2 installed permanently and logging it along with other data maybe I'll be able to tell what's going on.

BeaveRun is a fun little track. Despite the impression the website gives you, there is only the north track. The south track hasn't been started yet. The facilities are rudementary, mainly consisting of portable trailers for most of the "permanent" structures. I'd say it's equivalent to Summit Point in terms of development, at least until the new circuit at Summit is completed. Once Summit Point is complete it will be the better facility. It is a short track, but to me that means it's easy to memorize but all the turns are challenging. If you're close to this track, definately check it out.

 

Regardless of the EVO running catless or not, or where the fuel lighting does occur, I have a question of...does the EVO have a 'more' of a potential of shooting flames than say other cars? Is there a paticular combustion chamger/head-design that causes this? Is the fuelling system a little 'slow' for the adbrupt "just-off-throttle" situation, our EVOs get upon shifting?

FYI I just spent a weekend watching the World Superbike racers zip around a Cali. track and found the inline three cyl. the Foggy Patronas FP1 bike spit about 3 foot long flames out the back, followed by a huge CRACK! The head design was apparently done by Ford Cosworth.

Somebody...please help satisify my insanely hungry curiousness.

Thanks,

jcnel.

 

well if you're running a VTA valve, i think when you shift, the car momentarily runs super duper rich when you shift... that may cause some of the richness, and also the fact that the cat is not there, well boom, BBQ time yum.

Nebo

 

Exactly my point... when injector duty cycle hits 100% the injectors are spraying constantly through the whole window of time available for injection. When this occurs the fuel is simply loaded onto the back of the valves and normally is sucked in and atomized during the next intake stroke. I think when the throttle is lifted the fuel sucked in off the backs of the valves isn't burned in the cylinder and instead is pushed out through the exhaust. When I get back on the power the fuel in the exhaust is ignited.

I guess really my question is, do guys with properly sized injectors (ie injector duty cycle <80%) and properly tuned systems have flames?

 

Yes, it's a common attribute on turbo cars.