Over Boost

You know the Misfiring system you see on rally cars? Anyone ever use it on a Porsche? How about a street driven one? I’m not considering it or anything just wonder how it works and if there would be any advantages. I mean its suppose to keep your turbo spooled right? Sounds like that would be a handy little thing to have on a laggy 951.

Ian Carr

special tool had it on his car, its actually launch control. It limits the revs when the clutch is pushed in, so say you want to do a 3500 rpm launch, you can floor it and it will only go to 3500 rpm. Kind of rough on the engine but sounds cool as ****

-Ian

Brian Morris

Definitely not for a street car. You need a straight through exhaust. What is described on ST's car isn't really an "anti-lag" system. There's was just a thread on this within the last two months - search will find it.

The way it works is it continues to dump fuel in the cylinder after you've closed the throttle. The timing is changed to ignite the mixture when the exhaust valve is open - blowing the burning gases out the exhaust. This keeps the turbo spooled while you're going around a corner. It also keeps your exhaust glowing hot. Most higher end engine management systems like some Motec and Autronic have this option. I've heard it on a 800+hp GT2-Evo and a 962 - sounds cool.

--Brian Morris
89 951

reno808

Turbo X that is not a Misfiring system. Brian hit it on the spot. My friend is working on a set of chips. Its made so you have little or no lag. The old rally cars use to use that allot.. It pops allot once the exhaust is hot. It kills thru mufflers. And you have to do it right or else say good bye to your head gasket.

Over Boost

hmm could you make it so you could turn it on and off I wonder?

reno808

YEah most likey. Its only timing and fuel. I know vitesse has a switch to witch octanes. And thats all what it is.

tedesco

What I once anounced in the other thread (but finaly did not do) was to post a video to show how it worked on mine. I used a simple clutch activated soft cut rev limiter. Depending on the limit you set you can dial in the boost you want when you floor the throttle and the clutch is "open". I did several tests and you can improve the launches by adjusting the rev limit. I also tried to do full trottle shifts but it did not really work. Trouble is that if you do full throttle shift on a TURBO car, the boost pressure remains (which is good in one way) but it also sends huge amounts of unburned gas into the header and exhaust so that it will blow up ANY exhaust stystem I know. You would need to allow only a certain amount of unburned mixture to get into the exhaust which is enough to keep the turbine spinning. Allowing full boost mixture to enter the exhaust it far too much.
FOr launches it is good. I set the limit around 3500-3800rpm for best results (on a modified turbo) and it gives me about 0.3bar of boost which is just below the threshold of spinning the tires directly.
According to my experience a system like this is of NO practical use when street driving (besides waking up your neighbours if you like). The backfires are spectacular but don´t help you really.

special tool

This is a very timely thread.
I agree-I abandoned my MSD system becasue it was too rough on expensive turbohargers.
However, I expect to be testing the new Vitesse FUEL cut flatfoot/launch system in a couple weeks........
This will be exactly where you want it and be harmless to the turbo.

Porschefile

Antilag destroys turbos. Last time I checked it was a time consuming process to change a turbo out on our cars, so this isn't exactly the greatest idea.

2 step launch control set to 3.5k? Weaksauce. First off, the only reason you'd really need launch control is drag racing. Second, if you are drag racing your car to the point you are using launch control to try and lower your ET, you better have it set a little bit higher than 3.5k (like 5 or 6k) if you don't want to bog out of the hole. If you aren't spinning your tires when launching, you're not launching hard enough, period (if you really care about ET's that is). Next time try a manly 6k 2 step cv snapping, transaxle cracking, ring gear breaking super launch! j/k

Ian Carr

i was just giving an example ... hater

fast951

NOTICE: Unless I announce the release of a new product, assume it's not a real product.
There will be NO " new Vitesse FUEL cut flatfoot/launch system in a couple weeks........"!!!! Good try ST.

tedesco

Porschefile, just belive what I wrote! I did the tests myself. If you try anything higher than 4000rpm with this system the car does not even start to move at all because of tires spinning. 3800rpm was the highest level that worked on roads with highest grip. There is no boging at all. Don´t compare the launch bahaviour with a stock car without soft cut rev limiter. With this system you are on FULL throttle during the lanch and not at part throttle as you would normally do to keep your let´s say 5000rpm for hte launch.

tedesco

@ST: According to m experience the soft cut is not hard at all on turbos as long as you keep the rpm limit low. I observer basicaly two different levels:

1. at low engine rpm (<3500) there is hardly any backfire. The unburned mixture runs through the manifold and does not cause any bachfires. Still is helps spooling the turbo because the engine is running at wide open throttle and acts as an air pump. Engine has a high volumetic eff and is not restricted like on part throttle. My impression until this point was that it is very mild to the engine and turbo.

2. the higher you go up in the rpm range the more violent the backfires will get but this still did not lead to a boost explosion. In fact I was first surprised that the boost did not go up higher quickly. With my engine I reached 0.3bar at 3500, about 0.8bar at 5000rpm. So I thought that the mixture did not ignite in the header but in the exhaust only. FIrst I wanted to counteract by installing a spark plug in the crossover but than I decided to try with a "glow plug" first. My glow plug was a simple screw for wood, so very shart at the end. FOr the next test I first heated up the exhaust, turbo and "glow plug" and tried again to see if anything changes on the boost buid up... but nothing, exactly as before. Finaly I arrived at the conclusion that at least I could not make the system work to really ignite the mixture before it passed through the turbine. The backfires are just ignitions in the exhaust and I did not observe that this actually helped to generate boost. It is loud and violent and in this condition certainly very hard on turbos. Still, only the initial working mechanism (pump) remains.

In the end I just found that it was without any practical use for myself and did not persue this route any more