Keith wrote: Modern WRC cars still use anti-lag. You can see the exhaust tips of the Fords glowing constantly.
You're seeing the catalyst glowing.
And to the OP: Nothin' says lovin' like a rotary with an ignition-based flat shift. It's good for quick shifting, and eliminating tailgaters.
dyintorace wrote: Rotary engines seem to be especially capable of fireballs. I love them.
The thing on upshift is, when you lift, the pressure in the intake manifold drops. Lower pressure means fuel that HAD been wetting the walls suddenly re-vaporizes and makes its way into the engine. (And the opposite effect is why even EFI needs throttle-opening enrichment) The more of the manifold is wetted, the more this happens.
Combine that, with a carburetor's propensity for going overrich at high vacuum, and the rotary's babylike ability for air and fuel to pass right through undigested, and you get something like this:
My SAAB c900 turbo has a really good crackle & pop. I'm building my new exhaust system around a vintage Ansa dual chrome tip resonator. I want some flash and bang to go with my bling
I think I'll try an atmospheric dump valve first to richen it up, before I try any special tuning tricks. 
[sigh!] I wish I could get my datsun to spit fire on a GRM budget. I don't think I can pull that off...it will be hard enough to get the car running
HappyAndy wrote: My SAAB c900 turbo has a really good crackle & pop. I'm building my new exhaust system around a vintage Ansa dual chrome tip resonator. I want some flash and bang to go with my bling
I have one of those tips made for a truck application. It is about 18 inchs long and will look good tucked up under the bumper the way that old saab's route their exhaust
Armitage wrote:MadScientistMatt wrote: There are two common ways you can end up with a tune that makes a car spit flames. One is a rev limiter that cuts the ignition but leaves the fuel on. The other is if too much fuel is added at high RPM, low load cells in the fuel table - this results in a backfire when you lift off the throttle.The third is to drive something rotary-powered :)
Truth. A guy I used to autocross against was constantly blowing flames ouf of his RX-8's exhaust. He was slow, but his pictures looked cooler than anyone's...
Knurled wrote:Keith wrote: Modern WRC cars still use anti-lag. You can see the exhaust tips of the Fords glowing constantly.You're seeing the catalyst glowing.
That makes sense, it's such a consistent glow. Although you can still hear the anti-lag on the cars.
Yep, although the antilag is more air-assisted, makes funny pshooshy sounds. I don't see any other way for them to get 30-40psi boost at ~2500rpm.
I wonder if this has to do with some weird FIA noise regulation, or if it's more related to limits on spare turbos. I don't know if they still have to carry the spare turbo in the car, but IIRC they are only allowed one spare per car per event. I guess the old Group A style antilag really did a number on turbo life.
BTW - Saw a dyno plot for a restrictor motor. Don't know any of the specs, but the horsepower was within 10hp of 300 from around 2500 to 7000rpm. Boost started at 36psi and tapered down to 8. Me, I want to know what the turbo was actually doing for pressure ratio. And the question: Better to run at high boost/low RPM and risk hurting the transmission/clutch/bottom end, or run at high RPM and risk hurting other things from spinning a turbo extremely hard to make only 8psi boost?
92CelicaHalfTrac wrote: What's your record so far? I've gotten a good 6-8 feet out of mine.
I am in need of an accomplice to document it. I've seen the glow on an underpass wall at night, but that's about it.
Ah ok... I need to capture it through video as well.
I get flashes under bridges like bombs going off, with sound to go with it.
It's fun, but sometimes i feel bad because it does scare people around me.
it's lots of fun, but not efficent, and as you noted, not very considerate of those around you.
What does it take for carbuetored cars to do it?
Alas, i wish i had the ability to make it stop when i wanted to. Unfortunately, i'm running a stock ECU at the moment and this is just what's happening.
93EXCivic wrote: What does it take for carbuetored cars to do it?
I would really like to know, too....This thread has made me want very badly to have my streetrod spit fire
93EXCivic wrote: What does it take for carbuetored cars to do it?
Rev the motor up, turn the ignition key off and back on very quickly. Or bounce the motor off an MSD-type rev limiter.
Or if you just have some really crappy carb tuning. For a while, my project Dart used a Holley four barrel that wasn't set up very well for boost. Flooring it would give a massive bog, then it would shoot flames out the side exit exhaust and suddenly take off.
JohnyHachi6 wrote: It's also not unusual on RPM-MAP based ecus in race applications for the lowest MAP bins to be set at the max vacuum that you can pull while opening the throttle quickly. When you quickly close the throttle quickly at high-load, high-rpm, you can often get the MAP to dip below that value and it will cause a rich condition that produces popping and flames. You can tune it out by spreading out your MAP bins, but it will lower the resolution of your fuel tables in the normal operating range and hence isn't usually done in race applications.
It depends on the way the ECU handles calculations - if there's some form of air density scaling, the ECU should be able to track the MAP reading dropping "off the table" and still pull a bit of fuel.
The other answer is, a lot of the NASCAR teams use fuel over-run to keep piston temps down. Unburned fuel through the hot exhaust, and VOILA! Flames.
http://www.youtube.com/watch?v=RD2cdmriowg
The Boston Hong doin' the two-step...
It would get loud enough to reset the fluorescent lights in the shop!
later, matt
because this
Knurled wrote: Combine that, with a carburetor's propensity for going overrich at high vacuum, and the rotary's babylike ability for air and fuel to pass right through undigested, and you get something like this: Awesome dyno video
My God that was one of the most beautiful engine noises video I've seen in a long while. Man I love rotaries.
93EXCivic wrote: What does it take for carbuetored cars to do it?
most carbs have a fuel shutoff switch that kicks in when the engine is on decelleration... I think if you just disconnected it
My LS1 swapped 951 spits fire on track when I lift. Keeps everyone behind me very entertained!
The RX-7 and RX-8 spit them pretty easily. The RX-7 would do it driving "normally" sometimes. I haven't noticed any in the Corvette.
The back of my dad's RX-3 once caught fire because it was rich 
My son's cat-less FC RX7 will spit 6 foot flames when upshifting at redline. Definitely helps with tailgaters. After coming back from the first HPDE with the car, I was telling my colleagues about the flames. There seemed to be a strong gender bias in the responses.
Women - Oh no! Can you fix that?
Men - Cool! How do I make my car do that?
Bumping this back up for a question. I just finished putting the catless downpipe on my Miata. I haven't finished putting the rest of the exhaust on yet and don't know when I will. Would it be fine to start it up and drive it for a bit while tuning with the possibility that it could spit flames with a catless downpipe pointing straight at the gas tank? How about with a turndown?
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