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Old 09-23-2008, 12:32 AM   #1
jetfan2207
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Default drag racing and large turbos

Hey everyone,

I have a quick question regarding drag racing cars fitted with huge turbos. I understand what turbos do and how they work (I consider myself a noob). anyway, I have noticed at the track that a lot of the turboed strictly drag cars stage and rev up, there is a lot of noise once the turbo has spooled. poping and cracking mostly. I'm guessing it's pre-ignition, but IDK. Anyone know what causes this?


Thanks in advance,
Steve
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Old 09-23-2008, 12:38 AM   #2
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It's anti-lag.

Basically they run it very rich with retarded timing to dump fuel into the exhaust and burn it there to spool up the turbo faster.
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Old 09-23-2008, 12:44 AM   #3
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^^ what he said
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Old 09-23-2008, 06:41 AM   #4
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They run anti lag at the launch? That seems odd......I figured it would be the launch control system holding the desired rpm.......
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Old 09-24-2008, 10:20 PM   #5
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Quote:
Originally Posted by Storm View Post
They run anti lag at the launch? That seems odd......I figured it would be the launch control system holding the desired rpm.......
Anti lag is part of the LC system (usually) on turbo cars. Without the retarded timing and stupid rich conditions, all it would do it hold a high RPM without providing any significant load on the turbo. Kinda of like you can go outside right now (don't do it though ) and rev your car to a high rpm and you won't build more than lets say 2-5psi of boost. Do that with anti lag, you leave the line with 20+psi (this will vary greatly, but you get the idea).
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Old 09-28-2008, 06:15 PM   #6
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Quote:
Originally Posted by vlady View Post
Anti lag is part of the LC system (usually) on turbo cars. Without the retarded timing and stupid rich conditions, all it would do it hold a high RPM without providing any significant load on the turbo. Kinda of like you can go outside right now (don't do it though ) and rev your car to a high rpm and you won't build more than lets say 2-5psi of boost. Do that with anti lag, you leave the line with 20+psi (this will vary greatly, but you get the idea).
Not really. You build boost by creating a load on the engine. Creating an artifically lower rev limit for launching, say 5500, then going WOT while not moving will build boost. No anti lag system is needed. The reason you can't build boost just revving an engine is there is very little load on it.

Tony
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Old 09-28-2008, 06:27 PM   #7
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Quote:
Originally Posted by Turn in Concepts View Post
Not really. You build boost by creating a load on the engine. Creating an artifically lower rev limit for launching, say 5500, then going WOT while not moving will build boost. No anti lag system is needed. The reason you can't build boost just revving an engine is there is very little load on it.

Tony
What your talking about is a 2-step rev limmiter, which helps smaller turbos get off the line, but for bigger turbos you need a launch control set-up that can seriously retard timing like anti-lag to build any boost.
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Old 09-28-2008, 08:51 PM   #8
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Some 2-steps (gizzmo for instance) are ignition cut based - so work very similar to retard sysems in that excess, unignited fuel passes into the headers, and then ignites in the headers to provide very similar effects.

The LC patch used on subaru ecus cuts both fuel and ignition, so the benefit is greatly deminished, where the ignition cut systems can generate more then 10psi of boost if you rev it long enough, the LC patch (or most other fuel and ignition cut systems) usually generate less then 10psi (which is still pretty decent).

Saying that, nothing beats a retard LC system at generating as much boost (and flames) as required
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