squeaking noise from WRC cars

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Originally Posted by Zico

I think you must have the wastegate confused with a dump valve.

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ZICO, do you mean by a dump valve a blow off valve i.e. a by pass valve isn’t a dump valve? Just to clarify that we are talking about same things.

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Originally Posted by OldF

ZICO, do you mean by a dump valve a blow off valve i.e. a by pass valve isn’t a dump valve? Just to clarify that we are talking about same things.

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Yes, my definition of a dumpvalve (BOV) is one that releases the pressure to the atmosphere. Is my info wrong?

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Originally Posted by Zico

Yes, my definition of a dumpvalve (BOV) is one that releases the pressure to the atmosphere. Is my info wrong?

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Not in my opinion. Dump valve as it says waste the excessive pressure. I just asked to clarify that I understood the “dump valve” right.

I read some of this stuff on this forum and it makes me want to scream!

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Originally Posted by anstis

Don't quote me on this but I think I read somewhere a long time ago, from memory it might have been David Lapworth explaining, that when the throttle is closed the compressed air, having gone through the turbo, almost stops as there is less being fed into the engine. The compressed air then momentarily expands forcing some backwards through the compressor wheel as it's still spinning, creating a chirp.

I could be mistaken though...

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Originally Posted by Nenukknak

I really can't imagine that's correct.

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And now I can. The sound is indeed from compressor surge. And probably the reason that you hear it less is due to technological advancements reducing this phenomenon.

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Originally Posted by Gard

Call it what you like :rolleyes:

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What do you call it?
Or more to the point just what do WRC cars use to control turbine speed?

Jan they don't use wastegates in wrcars. They regulate boost by magic

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Originally Posted by Daniel

Jan they don't use wastegates in wrcars. They regulate boost by magic

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Could you please explain the magic they’re using.

To go back to this web site http://www.turbobygarrett.com/turbob...o_tech103.html there are two borders on a compressor map that shouldn’t be crossed. The one to the left on the map, the surge line is described already. The one to the right, the choke line, is where the speed of the turbo approach allowable limit and IMO the only way to prevent this is using a waste gate to slow down the turbo. If someone disagrees, then please explain how it’s done.

◊ The Choke Line is the right hand boundary of the compressor map. For Garrett maps, the choke line is typically defined by the point where the efficiency drops below 58%. In addition to the rapid drop of compressor efficiency past this point, the turbo speed will also be approaching or exceeding the allowable limit. If your actual or predicted operation is beyond this limit, a larger compressor is necessary.

◊ Turbo Speed Lines are lines of constant turbo speed. Turbo speed for points between these lines can be estimated by interpolation. As turbo speed increases, the pressure ratio increases and/or mass flow increases. As indicated above in the choke line description, the turbo speed lines are very close together at the far right edge of the map. Once a compressor is operating past the choke limit, turbo speed increases very quickly and a turbo over-speed condition is very likely.

◊ Efficiency Islands are concentric regions on the maps that represent the compressor efficiency at any point on the map. The smallest island near the center of the map is the highest or peak efficiency island. As the rings move out from there, the efficiency drops by the indicated amount until the surge and choke limits are reached.

I think Daniel was being sarcastic OldF. ;)

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Originally Posted by Nenukknak

I think Daniel was being sarcastic OldF. ;)

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As always. Still I would like to know the magic behind it. ;)