I guess I should start off by introducing myself as I’m new here. I’m Guillaume, I’m from Ottawa (Barrhaven specifically). I’m in the market for an S14 but that’s not what this post is about.
I was just watching some Initial D, and they mentioned something called a misfiring system that is used on WRC cars. Now I’ve been watching the WRC for years now, and I know the effect that they’re talking about, but I don’t really know much about it.
What exactly is a misfiring system? How does it work? Would fitting it to an SR20 or RB26 make any appreciable difference?
i’m not 100% sure but a misfiring system used on WRC cars are only because they run huge ass turbos boosting so much, so it helps the turbo spool up better and less turbo lag. also, the high octane they use combined with the big turbos makes this effect possible, do not take my word on this but this is what i’ve heard somewhere. and i doubt it is realisitc on a 240sx unless its being used like a rally car.
Misfire or anti lag is an adjustment made to the timing/mixture to keep the Trubo spooling between shifts, WRC actually don’t run big HP numbers,( they need only make a max of 300hp ),but they use a small turbo, with a larger comp side to get the TQ and boost down low while keeping as broad a powerband as possible. misfire/anti lag WILL burn out your turbo in less then a year, and it will destroy a cat. unless you have a track only car it’s not worth the expense to use this system.
Ok, awesome, so unless I have a really big turbo and only really want to go to the track I should stay away from them. But how exactly do they work? How does adjusting the timing keep the turbo spooled up?
i dont know either, does anyone know ? I think what it is, is bascially timing adjusted earlier so the car runs really rich and the fuel espcapes the combustion chambers (pistons) when its still burning so its hotter and more exhaust having the turbo spin and then the car basically backfires ? i dont know… someone clear this up theres alot of people wondering i bet haha
Misfiring system
From Wikipedia, the free encyclopedia
The misfiring system
The misfiring system is a turbo ALS(Anti-Lag System), commonly used in rally, it first starts off by running rich then retards the ignition timing by 40 degrees. With the delayed ignition timing this results in some of air fuel mixture being vented into the exhaust manifold unburned. When the mixture hits the hot exhaust manifold it ignites on contact and this is what keeps the turbo spooling even when the driver lifts off the throttle. With the air fuel mixture igniting outside cylinder is what causes the loud bangs. Some of the mixture will continue burning through the exhaust system resulting in flames shooting out the muffler. I will note that a misfiring system will wreck havoc and greatly reduce the life of an engine. It’s also illegal to use on the streets because they’re too loud and produce more emission than a standard car engine.
There you go. Dont do it, you dont need it. Even if you are racing, I doubt that you have/need this at all.
exhaust valve is opening right as the spark ignites and as the burn is started
lots of fuel
by the time the burn is at its full heat i guess it follows fuel all the way to the turbo and ignites it
thats hte only way i see spark having anything to do with anti-lag
now heres what i dont get. how can you have fire out the exhaust without also having the popping from anti-lag? assuming the mani/turbo is the hottest part of the exhaust you would think any fuel would ignite inside the turbo and bang just the same… but it doesnt
just random flames sometimes. silent flames. maybe there is a difference between explosion and burning of the fuel. it must be that.
the difference between the two i have no idea but i have def seen the difference with my car
on my 2step rev limiter with ignition retard setup the car will ride the limiter and occasionaly pop, anyone of you that has heard it knows how ridiculously loud it is
then just racing letting off when the bov goes off the car will shoot out a 3-4ft fireball but it will be silent, like excess fuel is just going through the system and afterburning
i’d like to find out because i want ot learn if this afterburn is bad for the engine and turbo or not.
I’ve also heard a rich mixture in the engine upon deceleration helps cool the motor, however I would think too much fuel in the engine upon deceleration would contaminate the oil pretty quickly
any “modern” misfiring system has an actual injector somewhere in the exhaust.
basically the idea is to keep the turbo spooling between shifts and to push the exhaust gases out faster.
back in the audi days of rally they would just dump fuel but now they’re pretty sophisticated with EFI and what not.
it’s kinda like after burner in jet engines. jet engines experience a ~%50 power increase with after burner (dumping fuel in exhaust fumes) but it’s really bad on mileage, can’t do it all the time.
and yeah, it dramaticaly decreases the life of the turbo, but when you’re swapping turbo’s every 50km like those rally guys you don’t really give a sh…
^^^
edit: the above is when you “misfire” on purpose, of course, like some people mentioned, when venting or letting off throttle you’ll get flames, pops, bangs, etc., you don’t necessary wants those and they’re completely unpredictable. usually they’re very weak and don’t do damage they’re just “annoying” to some people (I think it’s pretty bad ass heh)
that’s what a cat is for as well, to destory unburnt fuels but without one, you’ll get some more popping action.
I’m pretty sure your silent flame out the rear is just extra fuel from letting off at high rpms and the static on the exhaust from the flow. So when you let off at WOT or whenever, that static becomes unstable due to the flow change and ignites the extra fuel. All stock exhuast are grounded to provent static. I’m pretty sure when you just let off in your car you have enough of air/fuel mixture in the exhuast due to the overlappping of the cams, and the static is what sets it off somewhere along in the cat-back. Thats just what I think but I could be wrong.
you would need something to “spark” the static, fuel cannot be ignited by charge build up, the charge woudl need to jump across something and there is absolutely no way there are little ligthning bolts jumping across a 3" pipe, heh. or even a 1" for that matter.
IF there is infact any sort of electric discharge involving the exhaust it would be the exhaust against the chassis on the outside… but that would require the exhaust to be mm’s away from another bare metal contact.
and the only reason I can see the exhaust needing to be grounded is because of the o2, finicky little things.
I school they told me it was to prevent static, so I donno. You wouldn’t need a large spark to ignite it, just a large enough build up. I pretty sure the fuel in the exhaust is what see the static off. Tracking at high rpm you will get a build up quite quickly.
you’re right, you wouldn’t need a large spark, but you still need a spark.
fuel doesn’t make sparks, and even if it possible to have the exhaust to hold a charge large enough to jump across a 1-3" gap (we’re talking 100’s of kV’s) it wouldn’t happen.
if you look at the cylindrical shape of the exhaust pipe as a gaussian surface, using guass law you’ll quickly discover that the electric charge on the inside is 0.
so if there was any sparking it would be on the outside.
this is exactly why they tell you to sit inside a car when it’s lightning because the chassis of the car acts like a gaussian surface keeping all the charge outside.
same reason why the gayest of all magicians criss angelfag can get zapped by a bazillion volts (note how he was wearing a metal meshed suite) and not melt.
there is no way there is sparking in the exhaust system, sorry dude.
I’m not saying it’s sparking across the whole 3inch pipe. It can spark like 1mm on to the excess fuel flowing through the pipe. Gas should conduct the spark.