DDP

Just buy an aftermarket MAF and you will hear the sound. You don't need to vent it to the Atmos to hear that sound. Once you have an aftermarket maf, there is no trap door closed when you shift so you will hear it. That way you won't have to worry about your a/f ratio and you will have the sound. Also, there are many cars that vent to the atmos that come like that from the factory. I believe the DSMs are like that.

eastendr

Vent to atmosphere - 20 Mb mpg file

This is a link to a clip of my 2.0 litre Cosworth RS500 doing a speed run using 18PSI boost (when run in it was 36 PSI). The noise from the dump valve gives you some idea of the amount of air generated by the T04E turbo.

I run a vent to atmosphere on the 951 with a MAP kit.

For my part, I don't hold with recirculating when the boost / aifflow goes right up as I think it's more important to vent the 'air column' between the turbo / throttle valve as quickly as possible to

a) prevent the compressed air from backing up and slowing the compressor

b) re-introducing even more hot air in to the inlet tract, whether it's recirculated through the intercooler or not.

That said, I'd say that a stock 951 works well with the recirculating valve (I ran both types on stock) because of the AFM and relatively low boost.

Rick

black944 turbo

Ventingt to atmosher also gives lag between gears. As previously stated the maf will allow for the sound turst me on that. Very high boost is some times good to vent to atmosphere so that you don't blow lines off. That is my understanding.

faithless

Thanks guys! great infoz!

I asked the tehnical staff at www.gofastbits.com what they knew about it, heres their reply:

"Hi Sean,
I can't say I've ever seen any proof one way or the other. There is more to
reducing lag than simply keeping up the compressor speed. On one hand, if
you release a large amount of air to provide as little resistance as
possible, the turbo *might* slow down slightly less, BUT, you lose all the
boost pressure in the turbo piping. Alternatively, if you keep a little
backpressure in the pipes, provided you change gears relatively quickly,
there can be a slight benefit in lag reduction because there is still some
pressure in the system. However, wait too long and the pressure is gone
anyway, and the turbo will have slowed down more.

So the lag will have more to do with the spring pre-load and the size of the
valve than whether or not it is plumbed back."

This issue is pretty controverisal.

NZ951

I think its important to keep in mind that MAP does not have the problems MAF does with this topic...

faithless

Yeah, thats what I gathered by reading prior threads. I understand that and I'm sure it would be a huge hassal to change it, especially just to have a PFFFSH sound.