Chip

Often see the boys in their Escorts dring around streets with their cars going BBBRRRMMM.WHHOOOOSSHH.
Whats happening and why?

I always thought a DV got rid of pressure from the turbo wheras an anti-lag system kept it in to keep the turbo boost up.

Chip.

Andy McCord

as far as i know when the turbo has compressed as much air as is possible through the intercooler & then the cylinders it then starts to decelerate rapidly because theres no where for the compressed air to go, this then starts to stall the turbo which is not good, so a dump valve then opens to release the pressurised air that cannot fit in to the cylinders, now the whoosh you hear on some cars is because the compressed air is dumped to atmosphere, but most cars actually recircultate the excess internally, p.s hope i have it right

the only bit off stuff i know about anti lag systems are the ones fitted to WRC cars, they reduce turbo spoolup speed by igniting the unburnt fuel going down the exhaust pipe so it explodes & gets out off the exhaust faster thus reducing back pressure in the exhaust, hence why they go pop & bang so often do i sound like know what im saying

[Edited by Andy McCord - 5/21/2003 2:58:50 PM]

RB5_245

look at the threads on wastegates, there's quite a lot on that just now

ChristianR

iTrader: (1)

A dump valve releases the pressure in the intake manifold. It does this when you release the accelerator. When you close the throttle i.e. let go of accelerator, you stop air from getting into the engine - but the engine wants air. So the pressure inside the intake manifold drops to vacuum (as it is sucking in air, but the throttle is closed so it can’t get any - hence vacuum).

It has used all the air that was there and is now sucking as much air as it can passed the closed throttle valve (not completely closed else it would stall). But, just before you closed the throttle by letting go of the accelerator, the turbo had pressurized all the air between it and the other side of the closed throttle valve. i.e. in the intercooler and all the pipe work.

When you close the throttle all that pressurized air has nowhere to go, so it goes back and works against the turbo. Which causes it to slow down massively or stall. The effect of this is equivalent to hitting the blades with a hammer. You use the dump valve to let all the pressurized air out so that it doesn’t have to go back and slow down the turbo.

The above is vent to atmosphere (vta), for re-circ, the only difference is that it sends the air from the dump valve back into the inlet of the engine. i.e. after the air filter but before the turbo. This is different to vta, which just opens and lets the air out into the atmosphere.

Timmy Tato

So is there any particular reason to go for a vta verses a re-circ? The vta's make the whoosh sound, right?
Tim

Trout

iTrader: (1)

My recirc is louder than a lot of VTA cars I have been in due to a very open inlet pipe which acts like a trumpet!

Rannoch

JonGould

A recirc valve is better as it will send the air back round to the front of the turbo, pressurising the pipework infron of the compressor wheel. the pressurisation will help to keep the revs up in the turbo.

all cars have a recirc on them already. the ECU compensates for the amount of recirculated air and adds extra fuel. if you vent to atmosphere then the ECU will be sending in to much fuel, and this is when you start to get big flames coming out (not on full throttle like F&F shows us)

[Edited by JonGould - 5/22/2003 5:25:05 PM]