How to beat turbo lag........

[Guest Martin F]

I'm just trying to get my head round how an aftermarket ECU can help reduce turbo lag.

 

Is it because you can retard the timing at certain points in the RPM range and therefore some of the combustion is still occuring as the exhaust port opens and hence the expanding charge will spool the turbo's better than a spent charge ?

 

Or is there some other reason.

[Terminator]

Originally posted by Martin F

I'm just trying to get my head round how an aftermarket ECU can help reduce turbo lag.

 

Is it because you can retard the timing at certain points in the RPM range and therefore some of the combustion is still occuring as the exhaust port opens and hence the expanding charge will spool the turbo's better than a spent charge ?

 

Or is there some other reason.

 

 

Err would this cause rapid valve seat deteriation on the exhaust side?

[JamesG]

That's going a long way to describe what anti-lag systems do on rally cars.

 

When the driver lifts off the throttle, the ignition is retarded something like 30-40 degrees and a certain amount of air is still allowed in. This, combined with increased fueling at that point, sits around unburned in the cylinder until the exhaust valve opens. The air-fuel mix ignites and forces the turbo to keep spinning instead of stalling.

 

The flames and banging would be pretty cool driving around town but it knackers up the exhaust, so I wouldn't bother doing it to the Supra

 

James.

[Wez]

my mate runs anti-lag on his scooby, its awsome, he was told to stop using on track though as it was too loud

 

[Ian C]

Originally posted by Martin F

I'm just trying to get my head round how an aftermarket ECU can help reduce turbo lag.

 

Is it because you can retard the timing at certain points in the RPM range and therefore some of the combustion is still occuring as the exhaust port opens and hence the expanding charge will spool the turbo's better than a spent charge ?

 

Or is there some other reason.

 

Ignition timing has a lot to do with turbocharging. I'm no expert, but I think it's the other way round to what you describe. The ignition is retarded because you are on boost. As the pressures go up, so does the need to retard the timing to avoid detonation.

 

So, advancing the timing must be good for power while the turbo is spinning up.

 

And therefore a big single (or even a parallel conversion) running on a stock ECU will experience problems - either very laggy as the ignition has been retarded before it's on-song, or dangerously advanced as you are on full boost before the sequential twins would be.

 

That's what I think, anyway. Fire away

 

-Ian