Rotors R Cool

I was thinking about how a car kicks a flame. And I was talking with a friend, who unlike me, knows a little about tuning a car. And he told me there is a map on the PFC for fuel delivery based on TPS and RPM. So you could force the car to dump fuel while off the throttle, and above say...5k rpm. I guess that would force it to kick a flame but then I got to thinking. If I'm still getting spark and some air, wouldn't the car try to keep pulling if I introduced fuel? Basically, I would be accelerating, get above 5k rpm and hop off the throttle while still in gear. When that map kicked in and added fuel, wouldn't the car try to keep accelerating.

I love thinking in theory about stuff like this but I can't figure all the aspects of this scenario. Out of pure curiosity, is that a possible side effect and what other side effects would arise?

dinosaur

no it won't. Closing the throttle closes the throttle plates, cutting off most of the air (hence vacuum at closed throttle). no air, no fire, just unburnt fuel. Some fuel will burn since there is some air getting in, but most won't.

Rotors R Cool

Would that harm the motor or be the perfect way to turn the car into a flame-thrower? Possibly burning the bumper off the car. Probably some bucking right? Would it depend on the amount of fuel that is dumped?

dinosaur

I'm not an engine guru, but heres what I think.
(My lawyer has a long disclaimer he wants me to put here. It goes on about how little I know and that no one in their right mind should ever follow my advice, yada, yada, yada. But I don't feel like typing that much.)

Would that harm the motor?
I don't know if would be good for the spark plugs, but I don't think detonation would be a problem, it would be super rick, and no "fire" anyway.

the perfect way to turn the car into a flame-thrower?
depends on the exhaust system you have. Straight exhaust might work, pre-cat would not, downpipe with cat, maybe so, maybe not, I don't know. The unburnt fuel needs to remain oxygen free till it gets past the muffler, so O2 pump would just cause a BIG back-fire.
getting a kit (from a Hot Rod parts place) that inserts a spark plug in the tailpipe and a Nozzle that injects a fuel (propane or such) would be easier and you could control when it blew flames.

Possibly burning the bumper off the car
do a search for a picture of the white FD with the bumper cover melted. Carry a good fire extinguisher.

Probably some bucking right?
I wouldn't think so.

Would it depend on the amount of fuel that is dumped?
well, yeah. more fuel more fire, I don't know if there is such a thing as too much. There may be a point of diminishing returns.

Watch a NASCAR race( I can't believe I just said that). they shoot flames going into the turns all the time

Houstonderk

iTrader: (3)

If you have seen an exhaust off a race car in nascar you would see that its basically half the length of the car with just straight pipes off the manifolds. That would make it pretty easy to shoot flames.

Rotors R Cool

The length of the exhaust doesn't really affect how well it shoots flames. After the combustion there is really no oxygen left. Therefore even if you have fuel and a hot enough exhaust pipe, you won't get a flame until you introduce oxygen. So there is usually not any flame until the tip where the whole mixture reaches atmospheric oxygen. On the other hand if you have really short headers only along with an aggressive cam/port the flame that you may see is usually just the unfinished combustion.

In the case where you're off throttle and still dumping fuel, it will depend on the amount of fuel dumped. If you are dumping enough fuel to match the oxygen or even surpass it, then you will be left without any oxygen after the combustion. However, if you don't dump enough fuel to match, then you will get some seriously pissed off air coming out of that motor.

trochoid

iTrader: (6)

I'm not familiar with 3rd gens, never had one or worked on one, 1st gens are my forte, 2nd gens to a much lesser extent. What I've found for flame shooting, propagation, is to take the rpms up to 7k, hard. full throttle then let off. When the rpms drop to 4k, slam the go pedal to the floor. Taught this to a friend of mine, GSL-SE, he nearly jumped out of his seat the first time it worked. All he had was headers and a glass pack.

I've tried and tried to get flames/backfire on my 12A 1/2 sp-1.2 bp and try as I might it never does. Even took the exhaust system off down to the headers. All I managed was a blue flicker of 3-4" and that was short lived. I've come to the conclusion that I can't make backfires because I have a full 3" exhaust. The exhaust flow lost too much velocity and heat due to the pipe diameter. Even jetting the carb richer didn't help.

You can give my method a try and see what happens. What may happen is the turbo momentarily spins backwards, worst case, if you have too big of a backfire, you might blow the seams on a muffler. Whoever said there's never too much fuel hasn't seen some of the pics posted in the 1st gen section. One of them showed a Rotaflow muffler with the muffler seam spit from one end to the other and most of the rear end cap blown out too. A Rotaflow is not a cheap muffler but is one of the best in terms of flow and sound for 1st gen and older rotaries.

ScrapFC

iTrader: (5)

All you need is a rich condition off throttle, no cats and (preferably) straight through muffler(s). At the last hillclimb I went to, my NA was said to have been throwing 4 foot flames when I chopped the throttle once it started going rich at high coolant temps. That's with a stock fuel system, "test pipe" and a big nasty single catback. One of the officials told me I needed to check my mandatory spark arrestor, so we were more careful to let off the throttle more gradually after that.

Rx-7Addict

iTrader: (2)

get a shitty tune

Terrh

iTrader: (7)

flames on ANY carbed vehicle are easy, even non-rotaries and motorcylcles.


coast in gear with the throttle just slightly open for 2-3 seconds with the key turned off, when you turn the key back on blammo!

vetteracer79

Heres my 2 cents.

Ill give u my setup up first. single turbo 3inch down pipe to gutted cat then to a straight thru. Every time i shift if im on the car decently hard i can hear it makin flames out the tail its a decently hard fire ball. All my buddies tell me they are bout 3 foot or so.
IMO its about the amount of fuel and the egt's that are bein made. that comes from timing and fuel amounts. If the egts are up enough to make the unburnt charge hot enough to combust when oxygen rich atmosphere smack it in the face at ur tail pipe ur gonna get flames regardless. if i sit still in a parking spot pin the motor to 82 for bout a tenth of a second and get off completely the throttle ill get a fire ball. same type of sound and look as if i was shiftin hard. Just a thought.

ls1motorsports

get a two step .. to cut ignition n not fuel . it will definatly throw out flames outa the back ..

ls1motorsports

my buddy put a 2 step on his rx7 and threw flames out every time he used the two step

ls1motorsports

leme knw if that helps

TurboMazdaSpeed

stock ecu + strait pipe + bov + fuel pump = flames on decel @ 3,000 rpm

http://ca.youtube.com/watch?v=xTzPlWHkBak

http://ca.youtube.com/watch?v=hlwpnrmKbgU

cptpain

iTrader: (1)

it has potential to cause irregular wear since your essentially washing the combustion chambers of necessary lubrication/oil which translates to more frequent oil changes since that fuel will dilute the oil in the pan.

pauli311

iTrader: (2)

lol works as advertised?