Dawsonb17a

Alright, my friend has a modded 3rd Gen RX-7, he removed his cats and just has a muffler. Whenever he shifts gears under hard acceleration, he always shoots a quick flame out his muffler. I think thats super sweet! I have an N/A GS-R and I'm wondering what it takes to make a normally aspirated car do that? I'm not too up to date on the thermodynamics of this. Would replacing the cat w/a test pipe alone make this possible, or what about the addition of a fuel pressure regulator, and a reprogrammed ECU with modified fuel curves. Could you shoot flames with a set up like that? (when I say shoot flames I mean just a small one that just shoots out so quick if you blink you miss it, not like those fake flames in TFATF).

Please don't flame me (no pun intended) on this or criticize me. I'm asking a serious, honest question.


[Modified by Dawsonb17a, 2:18 PM 8/7/2001]

B18C-EJ1

Could be done, but you'd need to remove the cat (not recommended) and run super rich all the time.

Dawsonb17a

I could care less about the cat really. I'm pretty sure I've got the original in place still, and with almost 180,000 miles on it its probably toast or close to it. Emission testing in NC is a once a year affair, so if I had a test pipe I could just swap the two in and out whenever I want to. So you'd have to run super rich? That would hurt the fule mileage, but would it hurt the power output of the engine? I don't want an engine that runs like **** just so I can have flames, haha. Is flame shooting something that rotaries are just good at? right now I'm not running a muffler at all (waiting for a new cat back system to be shipped) and sometimes when I back off the gas or shift quickly it'll pop and gurgle. I like it, but what the hell is that noise?

outlawtas

some supra guys put spark plugs in the exhaust tip, or something like that...talk to them over at supraforums.com

GSpeedR

I think that the flames (caused during a backfire) are more detremental than beneficial.

BTW go visit http://www.g2ic.com along with this site.

G

Actually, the flames are from the rev-limiter cutting ignition and the unburnt gas/air mix igniting in the exhaust from the next cylinder that fires. I had an MSD 6al with a home made limiter switch for take-offs, and the cars behind me say flames were coming out of the exhaust when the rev-limiter was engaged. If you have a straight through exhaust, no cat and no chambered mufflers you too can have flames shooting out the exhaust. You just need an ignition cut rev limiter, msd 6al, crane hi sex ignition. The stock Honda rev-limiter is a fuel cut, so you won't have any fuel to burn in the exhaust...........

Or, run a spark plug into the end of the exhaust and run your car rich, like the old timers.....

Did someone say "FLAMER"?


[Modified by G, 2:20 AM 8/8/2001]

GSpeedR

But the rev-limiter shouldn't be engaging after every shift. I was under the impression that it happens after every hard shift (not neccessarily an over-revved shift). As the gasses backfire, I thought they would ignite, causing the flames and the huge bang. My only references is my mom's old Vega, though.

That thing would backfire like a shot and spit flames out the back.

raene

I think the flames are caused by what the other guy listed - the rev limiter. It makes sense to me. However, it's also known that a super-hot exhaust can light off the exhaust fumes, so that if you're running rich you can backfire flames.

Doing this on an N/A car just isn't going to happen without adding rice in some fashion... ie., making it run so rich you'll foul the O2 sensors in three minutes, etc. You COULD do something like picking up a SAFC and making it run rich at the top-end, then adding a sparkplug to the exhaust system so that if you flip the switch the plug will light off the excess gas.

There's just no real benefit to doing this, though. It's just extra complexity, but if you like it, go for it.

Dawsonb17a

Alright, to start off, my buddy's RX-7 doesn't hit the rev limiter when he gets a flame, its just when he shifts gears quickly near or at redline, but he doesn't hit the limiter. As far as my car, in order to get a flame I'm not willing to put a spark plug in the exhaust. I prefer form follows function, so I'm not gonna do something like that. So you think its possible with a S-AFC? For my car I believe I'd use a V-AFC, but whatever. I don't want to only be able to make a flame by fouling plugs/O2 sensor, or hurting performance like I said. So if its not possible then fine, I can live with it.

Now here's a related question. Right now my current exhaust set up is completely stock, with the exception that I took the muffler completely off, hehe. Whenever I shift quickly from 1st to 2nd, 2nd to 3rd, and sometimes 3rd to 4th i can sometimes here a loud POP come from the exhaust, almost like a backfire, in the period of time while I'm not on the gas. The pop usually chimes in RIGHT when I get back on the throttle.. What is that noise? Also, whenever I let off the throttle while still in gear, around 3000-3500rpm my exhaust gurgles and burbles and pops a little. What causes that noise as well? I personally like the noises, think they're kinda cool, and give off the impression that my engine's tuned for racing, which its not, lol. Oh, and to answer some potential responses, I'm pretty sure these noises are NOT caused by something wrong with my engine. My engine is maintained regularly, runs very smoothly, and isn't rough anywhere in the powerband. It also returns good gas mileage, that hasn't fluctuated at all.

Petah

iTrader: (1)

The RX7 are really good at blowing flames through the exhaust cause rotory engines operates at a very high temp causing the unburnt fumes to ignite in the exhaust.

Dawsonb17a

man, I love those cars...wouldn't buy one though, I can't deal with the hassle of a rotary

nfn15037

Actually, the reason rotary motors blow flames is because alot of air/fuel mixture gets pushed into the exhaust when u lift. This is because rotarys have alot of "overlap", like with our cams, but they have no cams, thats the only way i can explain it.

Dawsonb17a

enough with the rotary! Can anyone explain the noises coming from my exhaust?!?

raene

Exhaust reversion due to loss of backpressure probably... I bet it would go away if you put on your catalytic converter again.

Dawsonb17a

Hey man, read that post more carefully! I said I removed my muffler, not my cat. I still have my cat on! I did think about the flow of gas changing directions very quickly, perhaps it creates the pop? But I still have a functioning catalytic converter on my car!

lude&lascivious

I have seen this on alot of the last gen rx7's. I believe it has something to do with the ECU keeping the Turbo spun up. Not really sure about that, but I asked around while at the track.

Also if you notice other hi performance engine with turbos do the same. F1, Pro-Rally, etc...

However, it still doesn't make any mechanical sense to me. I guess if you take into account the rapid shift and the fact that the ECU only gases it for a second, then perhaps.

Dunno, maybe a pro can answer this one.

Gasoline Fumes

My Wagon will shoot out a small flame when I take my foot off the gas at higher rpm. I hear a loud bang and at night see a flash in the mirror.


[Modified by Gasoline Fumes, 7:16 AM 8/9/2001]

G

Believe it or not, the rx7s actually expell more exhaust than a common V6 at the same rpms, they are inefficient when it comes to fuel consumption and do have intake/exhaust overlap from the port configuration. All these, running rich, crazy exhaust flow and alot of overlap would cause flames to shoot out of any exhaust....and make for a terribly fast turbo'd car.

He could also have a shift rev-limiter to match rpms and speed for more consistent shifts...........

Methos

http://www.studz.freeserve.co.uk/creatures/flame.htm

Have fun and make sure your sun visor is upside down and sideways at all times when shooting flames out your exhaust. Yo.


[Modified by Methos, 12:00 PM 8/9/2001]

Powered by Honda

Ever since I took off my cat and put on a test pipe on my B18C EK, my car shoots out a quick small flame when I let off the gas and my car backfires, not all the time though, but it happens a good deal of the time. It's usually visible at night. I've had friends and my gf drive behind me and they've seen it. Of course, I also run super rich, so that would be another reason for it. I've heard of that spark plug trick, the old V8 guys started that I believe.

Dawsonb17a

Anybody else noticed the flame phenomena with their car? And if so, whats your set up? Screw the sparkplug in the exhaust, to me that seems too Rice/Wheat.

samiam

rotaries tend to run richer than piston engines so it's a natural charicteristic of rotaries to back fire out the exhaust.