Re: Poping exhaust sound on rally cars.

[Mike Zamikhovsky <MikeZ755@sprintmail.com>]

Seung O Lee wrote:
> 
> On Tue, 9 Dec 1997, Mike Zamikhovsky wrote:
> 
>  > > Both of the Hyundai's and the Lancer Evo II sound that way too.
> > hope that it will make our sport grow. The reason for poping noise is
> > that in order to keep turbo spinning when shifting using clutch (no crash
> 
> I've seen Mazda RX-7's and Toyota Supra Turbo's with modified blow-off
> valves and when they down shift it makes that "PPPPPPfffftttttt!" sound.
> Pretty cool. Reminds me of Porsche 962's at LeMans.
> What the blow-off valve does is keep the turbos spinning while down
> shifting. Greddy and HKS, a Japanese tuning firm makes them. Geddy has
> universal fit blow-off valves.
> If I get an A4 1.8T I would definitely put one in my car. "Pppppfffftttt!"
> Maybe scare someone in a parking garage or something. But then again I
> might get sued.
> 
> I do have one question. How do you get your turbo charged cars to belch
> out flames through the exhaust pipe when down shifting?
> 
> Seung Lee
> 93 100S
> Silver Spring, Md


Pop off valve prevents turbo from slowing down when throttle is closed.
When it vents into the outside it makes whistle sound, not pop.
Fire out of exhaust pipe when shifting comes from ingnition retard at 
idle and unburned fule. When shifting up crash box without using clutch
there is fiewer pops. When downshifting you hear more pops.