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Old 04-23-2001, 10:59 PM   #1
E'scubi
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Post what is that chirping on the rally cars?

I just got done watching the Swedish Rally, and my curiousity was bugging me. So does anyone one know what that chirping noise is that all of the rally cars make?
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Old 04-23-2001, 11:11 PM   #2
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the chirps are the BOV... the popping (small backfires) is the anti-lag system.
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Old 04-23-2001, 11:17 PM   #3
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Wink

I think you are talking about the anti-lag systems that keep the turbo spooled up during shifts...
Basically an amount of fuel is allowed to pass through the engine off throttle so that when it hits the red-hot exhaust it combusts flowing more gas and therefore spooling the turbo very quickly! Then you have instantaneous boost when back on throttle...
BUT the downside is turbo repair/replacement very often and very harsh on other parts as well!

That is the "jist" of it, there is more info available online about it though...
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Old 04-23-2001, 11:19 PM   #4
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Brandon is right (I forgot you said chirping) the chirps are probably the blow off valves
but the flames and gun-like repititions are the ALS kicking in...

[This message has been edited by SubaFast (edited April 23, 2001).]
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Old 04-23-2001, 11:36 PM   #5
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speaking of rally sweden, burns didn't look so friendly when he was yelling at the spectators to help, hehe.
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Old 04-24-2001, 12:07 AM   #6
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Why does everyone think the chirping is a BOV...if you have a BOV on a car with antilag, they preaty much cancel each other out.

Its the wastegate, not the BOV.

Not untill someone shows me a technical drawing proving otherwise.
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Old 04-24-2001, 06:42 AM   #7
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well i woundnt be to happy either. i was watcing the last race they showed, (was it monte carlo?) and when the former subie driver that now drives the Focus RS (cant remember his name) broke down on a turn, about 3 people came down to "help". that would bother me too. some of the fans over there are pure itiots. they should stay OUT OF THE ROAD and on the side where they belong. (end vent )
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Old 04-24-2001, 07:41 AM   #8
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Well, on a street car, that chirping noise occurs when the blow off valve fails. It is caused by compressor surge, in that when the throttle plate is closed under boost, the pressurized air hits the plate, then the wave ricochets back to the turbine and then back to the t-body, etc. creating pretty much the exact same chirping noise. The noise itself comes from the pressure wave hitting the turbine wheel. You can destroy a turbo this way in not too much time.

Not sure if this is what is going on in the rally car.
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Old 04-24-2001, 08:04 AM   #9
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Thanks for the clarification on that subject I have been wondering what that sound is as well.
As for Burns yelling at the fans I think that he was just extremely frustrated which you could see by the expression on his face. At least there was a Subie in the top six.

Later Z
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Old 04-24-2001, 09:09 AM   #10
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You guys are all wrong...


The chirping sound is the back-up squirel drive system.

I think it is the mechanical thingy that regulates boost pressure when the throttle is closed. Is this a wastegate or a BOV?
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Old 04-24-2001, 09:15 AM   #11
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Chirping = Blow Off Valve

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Old 04-24-2001, 09:29 AM   #12
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like WRXRob said, the chirping is due to a compressor surge. Typically race cars do not run a BOV. It's just another place to leak boost and another part to break.

If you are feeling really stupid, and have a MBC installed, you can re-create that chirping by building mad boost with the MBC. It's not that good on the turbo, but sounds really cool.

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Old 04-24-2001, 09:32 AM   #13
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Suspension is what is causing it
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Old 04-24-2001, 09:39 AM   #14
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I don't know the answer myself... but I don't think any of you know what it really is.

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Old 04-24-2001, 09:45 AM   #15
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Engine RPM up, car in gear, lift throttle.
Turbo still making pressure but with throttle closed where does the pressure go?
Blow Off Valve.
Leak? Hardly!

--scott
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Old 04-24-2001, 10:45 AM   #16
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I usually hear a couple different chirping sounds, or sounds that could be described as chirping.

Hardened tranny/suspension/engine mounts? I know those things are noisy as hell on bumpy roads if you don't lube them up.

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Old 04-24-2001, 10:49 AM   #17
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Its the BOV. All grp WRC, A and N cars use them.
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Old 04-24-2001, 11:02 AM   #18
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Geez, I can't believe all the misinformation that is being presented here!

The chirping you hear is the cruise control manifold when it is being turned off so the driver can take manual control of the throttle. That's all it is! And I know, so don't bother arguing!!

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Old 04-24-2001, 11:20 AM   #19
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Question

Is this chirping sound the really high pitched whine that you hear inside the cabin?
I noticed that during the outside shots you can't hear the highpitched whine, but inside the cabin the whine is very prominent. I'm wondering what that whine is. Is it the same chirping sound you describe or something different? I'd like to know.
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Old 04-24-2001, 11:38 AM   #20
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Could it be the chattering of the differentials through the turn?
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Old 04-24-2001, 11:42 AM   #21
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the whine inside the car is just the turbo and the high strung engines remember that their gears are very short so it revs extremely fast

the chirp sound AFAIK is the blowoff valve going off mixed with the anti lag system, the ALS gives off a series of backfire explosions, coupled with the bov's normal psheeeeeeshhh sound ...

you can hear it all well here, check out how the "chirp" sound goes off when they let off the throttle, so basically it goes off when the antilag and bov go off...
http://www.pr-roadracing.com/22B.mp3


[This message has been edited by ProgWRX (edited April 24, 2001).]
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Old 04-24-2001, 11:47 AM   #22
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The sound to which the original poster is referring sounds like rabid squirrels on helium. A whole bunch of them. Always at the entrance to corners/lift throttle. Sort of sounds like tires slightly breaking traction but the pitch and rhythm is too consistant for that. chi-chi-chi-chi-chi-chi-chi-chi

<FONT SIZE="+3">It is the Blow Off Valve</FONT>
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Old 04-24-2001, 11:47 AM   #23
DammitBevis
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Sounds like suspension squeaks to me.
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Old 04-24-2001, 11:58 AM   #24
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Even more specific, it is the HKS Super-Sequential blow-off valve.
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Old 04-24-2001, 02:06 PM   #25
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THANK YOU ANDREW!!!!

Someone from the rallying comunity that KNOWS what he is talking about.

Think about it people, what does a BOV do? Regulat boost presure, and bleed excess boost presure.

What does anti-lag do? Keeps the turbo spooled during throttle lifts, reducing turbo lag, and keeping boost levels up.

Now, why would you run a system to keep boost presure up, only to bleed it all away into the atmosphere and have it do NOTHING for you?

Again Andrew i thank you for providing your profesional oppinion.

As for the high pirched whining sound in the cockpit. Thats from the gear box. The gear box is all straight cut gears, and are cut to VERY close tolerances, so the the transmission is VERY tight. As the gears spin, becuse they are so tight, they make a whining sound.
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