OT: FIA Rally-San Remo (and a question)

Did anyone catch this week's FIA Rally recap from San Remo? Is there anything better than seeing Tommy Makkinen's Mitsubishi going thru a toll booth travelling between stages? That was classic, hehe. Anyway, I've always wondered what the chirping sound is when they are decelerating?

Sounds a lot like a turbo pressure release valve operating to keep the turbo rpm up. They are present in some road going turbos and you can buy them for about AUS$150. I have one in my 86 300zx but since the turbo runs at a low boost (relatively), it is quieter and less high pitched than a rally or turbo race car. Might sound sexier when i fit the boost controller but I'm not after noise ;) The idea is - if you come off the throttle when under high boost, you can create a shockwave or at least sudden overpressure in the manifold as the engine is no longer pumping the same amount of air. The effect without an overpressure valve can stop the turbo in it's tracks or even reverse the spin. 120,000+rpm to 0 in a short time is hell for bearings, mounts etc. It also means you need to wait for the turbo to spool back up to operating RPM. With a one way valve attached to the intake (usually on the engine side of the intercooler) any backpressure can escape and the turbo can keep high rpms - reducing turbo lag and increasing longevity. The pressure release is not the same as the wastegate - the wastegate re-routes exhaust gases past the turbine to limit total boost pressure. iksteh Jimmy Sparks <[email hidden]> wrote in message news:lfKC7.1005667$[email hidden]...

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> Did anyone catch this week's FIA Rally recap from San Remo? Is there > anything better than seeing Tommy Makkinen's Mitsubishi going thru a toll > booth travelling between stages? That was classic, hehe. > > Anyway, I've always wondered what the chirping sound is when they are > decelerating? > >

Just wanted to add to this excelent explaination that "these things" are also know as "Anti-lag systems" -- ed_ The GPLEA -------------------------------------- - My name is Elliott Forbes Robinson. Spell it, please. - E-F-R. No, no, spell your name. - E-F-R!! iksteh wrote: > Sounds a lot like a turbo pressure release valve operating > to keep the turbo rpm up. They are present in some road > going turbos and you can buy them for about AUS$150. > > I have one in my 86 300zx but since the turbo runs at a low > boost (relatively), it is quieter and less high pitched than a > rally or turbo race car. Might sound sexier when i fit the > boost controller but I'm not after noise ;) > > The idea is - if you come off the throttle when under high > boost, you can create a shockwave or at least sudden > overpressure in the manifold as the engine is no longer > pumping the same amount of air. The effect without an > overpressure valve can stop the turbo in it's tracks or even > reverse the spin. 120,000+rpm to 0 in a short time is hell > for bearings, mounts etc. It also means you need to wait > for the turbo to spool back up to operating RPM. With a > one way valve attached to the intake (usually on the engine > side of the intercooler) any backpressure can escape and the > turbo can keep high rpms - reducing turbo lag and increasing > longevity. The pressure release is not the same as the > wastegate - the wastegate re-routes exhaust gases past > the turbine to limit total boost pressure. > > iksteh > > Jimmy Sparks <[email hidden]> wrote in message > news:lfKC7.1005667$[email hidden]... > > Did anyone catch this week's FIA Rally recap from San Remo? Is there > > anything better than seeing Tommy Makkinen's Mitsubishi going thru a toll > > booth travelling between stages? That was classic, hehe. > > > > Anyway, I've always wondered what the chirping sound is when they are > > decelerating? > > > > > >

They're not anti-lag systems you are hearing. They have them, but they're the things that pop and shoot fire and stuff. The chirping is from when all that turbo pressure is released during deceleration I believe, then the anti-lag system picks it back up. The reason why I'm saying this is because my dad had a turbocharged car w/o anti-lag that ran 16psi and it made very loud chirping noises like that when it decelerated. There was no anti-lag. At lots of rallies I've heard anti-lag systems, and they pop and shoot fire, anti lag just keeps shooting fuel to the turbo so it stays spooled, and then all that fuel burns up close to the exaust. You don't get a nice chirp from that :) Thanks, Alex Ed Solheim <[email hidden]> wrote in message news:lpPC7.750$[email hidden]...

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> Just wanted to add to this excelent explaination that "these things" are > also know as "Anti-lag systems" > -- > ed_ > The GPLEA > -------------------------------------- > - My name is Elliott Forbes Robinson. > Spell it, please. > - E-F-R. > No, no, spell your name. > - E-F-R!! > > > iksteh wrote: > > Sounds a lot like a turbo pressure release valve operating > > to keep the turbo rpm up. They are present in some road > > going turbos and you can buy them for about AUS$150. > > > > I have one in my 86 300zx but since the turbo runs at a low > > boost (relatively), it is quieter and less high pitched than a > > rally or turbo race car. Might sound sexier when i fit the > > boost controller but I'm not after noise ;) > > > > The idea is - if you come off the throttle when under high > > boost, you can create a shockwave or at least sudden > > overpressure in the manifold as the engine is no longer > > pumping the same amount of air. The effect without an > > overpressure valve can stop the turbo in it's tracks or even > > reverse the spin. 120,000+rpm to 0 in a short time is hell > > for bearings, mounts etc. It also means you need to wait > > for the turbo to spool back up to operating RPM. With a > > one way valve attached to the intake (usually on the engine > > side of the intercooler) any backpressure can escape and the > > turbo can keep high rpms - reducing turbo lag and increasing > > longevity. The pressure release is not the same as the > > wastegate - the wastegate re-routes exhaust gases past > > the turbine to limit total boost pressure. > > > > iksteh > > > > Jimmy Sparks <[email hidden]> wrote in message > > news:lfKC7.1005667$[email hidden]... > > > Did anyone catch this week's FIA Rally recap from San Remo? Is there > > > anything better than seeing Tommy Makkinen's Mitsubishi going thru a > toll > > > booth travelling between stages? That was classic, hehe. > > > > > > Anyway, I've always wondered what the chirping sound is when they are > > > decelerating? > > > > > > > > > > > >

thanks for the _very_ thorough responses guys. this is why off topic, yet auto-racing relavent questions are asked here :-) "Alex Kihurani" <[email hidden]> wrote in message news:VVTC7.5048$[email hidden]... > They're not anti-lag systems you are hearing. They have them, but they're > the things that pop and shoot fire and stuff. The chirping is from whenall > that turbo pressure is released during deceleration I believe, then the > anti-lag system picks it back up. The reason why I'm saying this isbecause > my dad had a turbocharged car w/o anti-lag that ran 16psi and it made very > loud chirping noises like that when it decelerated. There was no anti-lag. > At lots of rallies I've heard anti-lag systems, and they pop and shootfire, > anti lag just keeps shooting fuel to the turbo so it stays spooled, andthen > all that fuel burns up close to the exaust. You don't get a nice chirpfrom

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> that :) > > Thanks, > Alex > Ed Solheim <[email hidden]> wrote in message > news:lpPC7.750$[email hidden]... > > Just wanted to add to this excelent explaination that "these things" are > > also know as "Anti-lag systems" > > -- > > ed_ > > The GPLEA > > -------------------------------------- > > - My name is Elliott Forbes Robinson. > > Spell it, please. > > - E-F-R. > > No, no, spell your name. > > - E-F-R!! > > > > > > iksteh wrote: > > > Sounds a lot like a turbo pressure release valve operating > > > to keep the turbo rpm up. They are present in some road > > > going turbos and you can buy them for about AUS$150. > > > > > > I have one in my 86 300zx but since the turbo runs at a low > > > boost (relatively), it is quieter and less high pitched than a > > > rally or turbo race car. Might sound sexier when i fit the > > > boost controller but I'm not after noise ;) > > > > > > The idea is - if you come off the throttle when under high > > > boost, you can create a shockwave or at least sudden > > > overpressure in the manifold as the engine is no longer > > > pumping the same amount of air. The effect without an > > > overpressure valve can stop the turbo in it's tracks or even > > > reverse the spin. 120,000+rpm to 0 in a short time is hell > > > for bearings, mounts etc. It also means you need to wait > > > for the turbo to spool back up to operating RPM. With a > > > one way valve attached to the intake (usually on the engine > > > side of the intercooler) any backpressure can escape and the > > > turbo can keep high rpms - reducing turbo lag and increasing > > > longevity. The pressure release is not the same as the > > > wastegate - the wastegate re-routes exhaust gases past > > > the turbine to limit total boost pressure. > > > > > > iksteh > > > > > > Jimmy Sparks <[email hidden]> wrote in message > > > news:lfKC7.1005667$[email hidden]... > > > > Did anyone catch this week's FIA Rally recap from San Remo? Is

there > > > > anything better than seeing Tommy Makkinen's Mitsubishi going thru a > > toll > > > > booth travelling between stages? That was classic, hehe. > > > > > > > > Anyway, I've always wondered what the chirping sound is when theyare

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> > > > decelerating? > > > > > > > > > > > > > > > > > > > >

On Sun, 28 Oct 2001 02:41:21 GMT, "Jimmy Sparks" <[email hidden]> wrote: >Did anyone catch this week's FIA Rally recap from San Remo? Is there >anything better than seeing Tommy Makkinen's Mitsubishi going thru a toll >booth travelling between stages? That was classic, hehe. Yeah, that was too good, my wife and I got a charge out of that. Great shots of the race, btw - some of the in-car cams during the many off-road "excursions" made me shudder. Hopefully Speed Vision will not toss this kind of racing; between the rally stuff and the Goodwood festival coverage yesterday it was a racing fans dream - I'd hate to see it change, though it appears it may :( Ken