I was doing some brief reading on this in one of my rx-7 books but they didn't go into alot fo detail. So what causes the afterfire and what makes one rx-7 backfire worse than another, shoot flames and such. Also would this afterfire work similar to the way WRC cars have misfiring systems that causes strong exhaust pulses which keep a turbo spooled?

 

well backfire on rx7s happen cause the rotary engine naturaly runs rich..... theres more gas than air in the air/fuel mixture......so say your going WOT and let off the gas, excess fuel leaks out into your exhaust and the hot air ignites it which causes backfire.....but i dont know about missfiring systems

 

i think i read somewhere that on FCs, when the throttle plates snap closed after going WOT then letting off, the ECU cannot tell the injectors fast enough to stop giving fuel, so...

 

do rx8's backfire? i would guess not in stock form. The reason spot skater gave is why older cars backfire, but I don't know if that's the only reason a rx7 does it. A backfire is simply caused by the air/fuel mixture not fully burning and being dumped into an exhaust system with non-functional cats.

The misfire system from what I understand from initial d....... is not what an afterfire is. We only get backfires on downshifts or other quick transitions from WOT, or whatever would cause enough of a gap to allow too much fuel into the chamber and out the exhaust. A misfire system does misfires whenever your not WOT to keep the turbo spining, something a singal backfire would prolly not do. I'm way out on a limb so don't take what I said about misfiring systems to heart, just me guessing based off a relatively accurate anime series.

 

A true "misfire" system has an injector in the exhaust manifold. It'll inject fuel when off throttle, causing a "misfire" in the exhaust, thus keeping the turbos spooled.

 

rx8's w/ only midpipe's and catbacks backfire and shoot flames, seen it lots of times

 

Care to explain more on exactly how this works? I don't really understand how this would create enough pressure to keep the turbo spooled....

 

This is what i've read to. Not good for turbo's but good for race application like WRC, where your on and off the throttle a alot. WRC engines last what 2 races so its not like they care.

 

When the driver lifts his foot from the gas pedal the ignition timing is altered with sometimes 40° or more of delay (retard) and the intake air and fuel supply mixture is made richer. The inlet butterfly is kept slightly open or an air injector is used to maintain air supply to the engine. This results in air/fuel mixture that keeps getting in the combustion chambers when the driver no longer accelerates. The ignition being delayed, the air/fuel mixture reaches the exhaust tubes mostly unburned. When the spark plug fires, the exhaust valve is starting to open due to the ignition delay mentioned above. Additionally, the exhaust temperature being extremely high, the unburned fuel explodes at the contact of the exhaust tubes. Luckily the turbo sits right there and the explosion keeps it turning (otherwise it would slow down since its intake, the exhaust gases, is cut-off). The effect is vastly lower response times with some downsides:

A quick rise of the turbocharger's temperature (which jumps from ~800°C to the 1100°C+ region) whenever the system is activated

A huge stress on the exhaust manifold and pipes (mounted on a street car a bang-bang system would destroy the exhaust system within 50-100 km)

The turbo produces significant boost even at engine idle speeds

The explosions which occur in the exhaust tubes generate important flames which can, sometimes, be seen at the end of the exhaust tube

Reduced engine brake

The ALS effect is mostly dependent on the air allowed into the engine, the more air supplied the more the ALS effect will be noticeable. Consequently ALS systems can be more or less aggressive. A mild ALS will maintain a 0 to 0.3 bar pressure in the inlet manifold when activated whereas, when inactive, the pressure in the inlet manifold with the throttle closed would be in the region of -1 bar (absolute vacuum). Racing ALS versions can maintain a pressure of up to 1.5 bar in the inlet manifold with the throttle closed.
While the systems mounted in Toyota and Mitsubishi racing cars are relatively smooth and noiseless those fitted in Ford and Subaru cars are much more noisy and aggressive.
The bang-bang system owns its name to the loud explosion noises one hears whenever the driver lifts off. Most racing implementations have user selectable anti-lag settings depending on the terrain, usually three settings can be selected by the driver going from mild to very aggressive.

Note that some regional or national European events prohibit the use of ALS systems while more and more WRC events regulate the noise levels allowed by competition cars effectively disabling ALS.

Starting in 2002 new anti-lag techniques, such as Exhaust Gas Recirculation (EGR), are slowly overtaking the method described above as they are kinder on the engine's mechanical parts.

 

My Eclipse has an anti-lag feature built-in to the reprogrammed factory ECU. With about 10 degrees of retard, you can build full boost (20 psi) revving in neutral.

 

i dont kno i wish i could stop mine from doing it. if im going ove 100mph when ever i get off the throttle it happens.

 

My RX3 has always backfired untill my newest exhaust system was installed. The mechanic that built the system had never worked on a rotary before. He put a 2 inch system on using a glass pack and a muffler he said worked great on 302's(5 liter). The air pump and after burner has been gone for a long time. The system is a little louder(sounds good) and only backfires if I turn off ingition with the engine reving over 4 grand. I had understood it all had to do with unburnt gas in the hot exhaust system. I assumed my system has the "right" backpressure to stop backfires????

 

On what Eclipse to you have ant-lag? Definitely not a factory 1st or 2nd gen. If you're buildng boost at idle, something is seriously wrong.

 

Anti-Lag does not come standard on Eclipses or any car in general. Force13B knows what he's talking with how anti-lag works.

 

so if i run a str8 2inch exhaust in my N/A 13b fc it will back fire and still have better performance and sound good? do you need back pressure in rotories?if there N/A

 

you need back pressure in any car. Any turbo charged cars need not apply, for them the less back pressure the better.

 

be prepared to change that glasspack and possibly the main muffler. if you get the "right" backfire, it will blow apart ... literally!.

 

He said boost in neutral not at idle.

 

I read somewhere that in a rotary engine, when one side of the rotor does the power stroke and going to exhaust stroke, the following side of the rotor air and fuel mixes with the side on its exhaust stroke when the apex seal passes through the spark plug holes.

Either way, rotaries run rich

 

Probably DSMlink, they can do cool things with re-programmed stock ecu's on those cars, stutter box

 

You can idle under boost with certain types of antilag.

Jacked open throttle plate + retarded ignition timing + rotating fuel cut = the engine needs 2psi just to idle at 1500-2000rpm.

Then you push the accelerator down and it stops cutting fuel and ignition timing comes up to normal and away you go.