Anti Lag + Huge Turbo = Streetable?

Someone was talking to me about how Japanese Evos have an anti lag system that makes the car backfire or something when the clutch is out so the turbo doesn't need to re spool so you can basically run any size of turbo you want and it will always be spooled from the top of 1st to the end of 5th and i was wondering of this is how it works and if so why doesn't everyone use it and run huge turbos.

I searched but i couldnt find a good answer.

Thanks

"anti-lag", sometimes called "bang bang" retards the ignition some 20-30 degrees and overfuels like crazy to help spool a turbo. Basically, it shoves a lot of raw fuel into the exhaust manifold and then lights it up, creating an explosion in the exhaust system. This works great for spooling a drag race car or rally race car between shifts or during partial throttle cornering, but its extremely hard on the exhaust system and turbo. Not very "streetable"

I highly doubt any street car has something like this. And if it did, you'd be going through turbo's very quickly.

There are lots of differnt anti-lag systems in use, and in theory.

The most common, seen on WRC and old Group A rally cars is a fuel injector and spark plug in the exhaust, it works just like unclebob descirbed it.
Its not very sophisticated, an you deffinitly can't use it on a street car.

However, Mitisubishi does have a more advanced system that is fitted to the Lancer EVO 7 and up non-US versions.
Im totaly sure how it works, but my understanding is when you lift off it open s valve system in the exhaust manifold, and some of the gas being expelled by the tubro is re-directed back into it with enough velocity to help keep it spinning for an extra second or two.

There are also electric assist systems being developed that attach a very high speed electric motor to the turbo shaft.

i read about one fitted to a pikes peak RS200, the guy who did an acceleration test said that it couldn't be used for hard launches because it puts even more torque through the car's drivetrain, is that a different anti-lag system or did i miss something?

my friend's car has the simple anti-lag whereby an injector and spark plug are fitted into the exhaust to keep the turbo spooling, it's road-legal but it's closer to a race car than a road car and the constant banging from the exhaust is slightly annoying, i don't even notice a difference in lag whether the anit-lag's engaged or not, but i think that's just his car.

heres a turbo lexus sc300 doing what your talking about.

http://videos.streetfire.net/search/sc300/0/e4273e3f-87ba-4170-8833-e1e754fcb95a.htm

Well, the type they use in WRC is what I assume you're talking about. Anyhow, it isn't very streetable because it is going to destroy your turbo. They use it on WRC cars because they can afford new turbos and they tear down the car on a constant basis. The other problem you have is that this would not help off the line. The large turbo would still take forever to spool.

Just match the right turbo for your engine unless you're trying to build a dyno queen.

you could always use two different turbos to reduce lag.
one small turbo to get you off the line, and a huge one that takes over at high RPM's.

i believe VW is already doing this, but they are using a supercharger for low RPM's acceleration

you could always use two different turbos to reduce lag.
one small turbo to get you off the line, and a huge one that takes over at high RPM's.

i believe VW is already doing this, but they are using a supercharger for low RPM's acceleration

its called sequential turbo's. almost any car that has a dual turbo setup is using this. its alot harder to do on smaller engines, like 4 cyl, cuz they don't create enough exhaust pressure to puch both turbos, unless you come up with a special valve system. if you can pull that off then you can do one for me :naughty:

I know people who run antilag on older mitsubishi evo's. They were using aftermarket ECU's and didn't have problems with cooking turbos.

I even know people who would wire it into a NA car. Just because they love the flames out the exhaust.:grinyes:

The anti lag system used in WRC can be used on the street in a slightly milder form. Prodrive actually used such a system in their prototype (P2 it's called if I remember correct), and they have also built a Subaru road car for demonstrations. The system works quiet and it's not hard on the engine or the turbo.

The WRC style ALS system use the ordinary fuel injectors to supply fuel, and air is bypassed to the exhaust system though a special variable valve which is under the control of the ECU. The ECU also get feedback from the turbo speed pickup. The ECU also control the electronic throttle, ignition, fuel and wastegate. When the exhaust from the engine isn't enough to reach the set boost pressure, the system starts to work. It opens the valve to supply a certain amount of air to the exhaust manifold combustion chamber, there it meets up with unburned fuel in the exhaust, the fuel is supplied from the ordinary fuel injectors. Due to the heat in the exhaust system the fuel ignite, burn and therby power the turbine. Note that the ignition isn't retarded or cut, this means that the engine operates like usual.

Based on throttle position and car velocity there is a certain boost pressure and turbocharger speed that the ECU works to achieve.


This system does not only result in zero lag, but also a massive increase in low speed torque.

This ALS system essentially allows the turbo to run as a separate gas turbine when not powered by engine exhaust.

The difference between the street and WRC versions is that the turbo speed and boost is set much lower in the street version.

Systems which work by ignition retard + open up the throttle a bit usually increase the thermal stress on the engine, which tends to overheat. The high temperature/pressure pulses that the turbo/valves/manifold is subjected to is also damaging. These are no longer used in WRC, but they are still used in lower classes since they are much cheaper. Most cheaper aftermarket ECU's tend to support this also while you probably need a more expensive ECU from Prodrive, Magneti Marellli, McLaren or similar to use the WRC style ALS. You need an electronic throttle and a turbo with a speed pick up aswell. Given that for example McLaren may charge you $30,000 for a racing ECU, and the racing turbo fitted with the speed sensor can cost you an additional $10,000 it may take some time until we see that kind of ALS in tuned cars.