Back on the old, old forum Marcus Dodd did a fairly lengthy post about turbos that was quite interesting. Sadly now the archive has gone it's probably consigned to history :(Quote:
Originally Posted by Zico
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Back on the old, old forum Marcus Dodd did a fairly lengthy post about turbos that was quite interesting. Sadly now the archive has gone it's probably consigned to history :(Quote:
Originally Posted by Zico
I found out the cause of this noise, dodgy window seals on frameless windows. Was driving to work today and the car started making the exact same noise as what is being described on this thread :p Scared the bejeezus out of me :mark:Quote:
Originally Posted by Zico
I thought it was stated that wrc cars dont have a waste gate...
I think you must have the wastegate confused with a dump valve.Quote:
Originally Posted by zerodegreec
Yes, two different things.Quote:
Originally Posted by Zico
http://www.turbobygarrett.com/turbob...o_tech103.html
Dump valve = blow of valve, BOV.
“Surge will decay once the turbo speed finally slows enough to reduce the boost and move the operating point back into the stable region. This situation is commonly addressed by using a Blow-Off Valves (BOV) or bypass valve. A BOV functions to vent intake pressure to atmosphere so that the mass flow ramps down smoothly, keeping the compressor out of surge. In the case of a recirculating bypass valve, the airflow is recirculated back to the compressor inlet.”
http://www.turbobygarrett.com/turbob...o_tech101.html
Wastegates
On the exhaust side, a Wastegates provides us a means to control the boost pressure of the engine. Some commercial diesel applications do not use a Wastegates at all. This type of system is called a free-floating turbocharger.
However, the vast majority of gasoline performance applications require a Wastegates. There are two (2) configurations of Wastegates, internal or external. Both internal and external Wastegates provide a means to bypass exhaust flow from the turbine wheel. Bypassing this energy (e.g. exhaust flow) reduces the power driving the turbine wheel to match the power required for a given boost level. Similar to the BOV, the Wastegates uses boost pressure and spring force to regulate the flow bypassing the turbine.
Internal Wastegates are built into the turbine housing and consist of a “flapper” valve, crank arm, rod end, and pneumatic actuator. It is important to connect this actuator only to boost pressure; i.e. it is not designed to handle vacuum and as such should not be referenced to an intake manifold.
Internal Wastegate
External Wastegates are added to the exhaust plumbing on the exhaust manifold or header. The advantage of external Wastegates is that the bypassed flow can be reintroduced into the exhaust stream further downstream of the turbine. This tends to
improve the turbine’s performance. On racing applications, this Wastegated exhaust flow can be vented directly to atmosphere.
So, in plain words, the flow that spins the turbo is controlled by Wastegate, and the flow (compressed air) that turbo generates is controlled by BOV. Is that correct?Quote:
Originally Posted by OldF
So, the noise is created by the compressed air going backwards (when throttle is lifted) through the compressor wheel. In other words neither the BOV or Wastegate are related to the noise. Is that correct?
The BOV/BPV and the wastegate also make noices. Different noises dependent of the setup. BOV are often made so they will sound the most. Many love the blowing/exhaling sound when shifting gears. This can also be heard when using BPV, especially with open air-filters. then you hear the air rushes back. WRC doesn't use wastegate, but the ALS will also make noises.
A turbo engine is like a small orchestra.
WRCars DO use a wastegate.....Quote:
Originally Posted by Gard
Call it what you like :rolleyes:Quote:
Originally Posted by Daniel
There's no need to have an attitude! :laugh: You said that WRCars don't use a wastegate when they do. Perhaps you yourself don't call it a wastegate but they do use a wastegate.....Quote:
Originally Posted by Gard
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.Quote:
Originally Posted by Zico
Yes, my definition of a dumpvalve (BOV) is one that releases the pressure to the atmosphere. Is my info wrong?Quote:
Originally Posted by OldF
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.Quote:
Originally Posted by Zico
I read some of this stuff on this forum and it makes me want to scream!
Quote:
Originally Posted by anstis
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.Quote:
Originally Posted by Nenukknak
Quote:
Originally Posted by Gard
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
Could you please explain the magic they’re using.Quote:
Originally Posted by Daniel
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. ;)
As always. Still I would like to know the magic behind it. ;)Quote:
Originally Posted by Nenukknak
Just the man.. You probably know more about ALS than the lot of us put together, dont scream.. just set us all straight once and for all.Quote:
Originally Posted by bubbaontour