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PostPosted: Thu Dec 22, 2005 11:19 pm 
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Has anyone ever fitted the throttle body before the turbo? (Like on a supercharger setup). It occurs to me that it should reduce spool-down on throttle closed events. Theoretically it shouldn't be hard to do.

Graham


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PostPosted: Fri Dec 23, 2005 12:41 am 
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Interesting idea. I 'm sure that there must be a reason why the TB is in the current setup?

Seems that "our" setup is similar to lots of other turbo car setups...there must be some good reason why it is like this?

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PostPosted: Fri Dec 23, 2005 2:31 am 
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Quote:
Seems that "our" setup is similar to lots of other turbo car setups...there must be some good reason why it is like this?


Yes I agree our setup is the same as other turbo car setups, but an inquisitive mind might question why this should be so. Any ideas?

To my way of thinking, putting the TB before the turbo would reduce fast spool down times when the throttle is closed between gear shifts, and also eliminate the requirement for a dump valve. All due to the fact that when the throttle butterfly closes, the turbo impellor would be sucking on vacuum which means no impellor load.

Graham


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PostPosted: Fri Dec 23, 2005 11:03 am 
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Surely you'd be running the risk of overspeeding the turbo when you shut the throttle though?

You're guaranteeing a compressor stall and then making this happen in a partial vacuum while still providing some exhaust gas to keep everything going......

To my still slightly soaked brain that sounds like a BABOOOOOOOOOM event


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PostPosted: Fri Dec 23, 2005 11:25 am 
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I'd agree with Steve.

The throttle butterfly closes and the turbo is left spinning to suck on a vacuum, this would surely be no better an evil than the current situation of trying to pump at presure with airflow back over the compressor. Theres is still going to be a loading on the wheel.

I would suspect that the supercharger route doesnt have such problems with this as the turbo because the supercharger is directly linked to engine speed, where as the turbo can do what i likes really and continue spinning and trying to make boost after the revs decrease.

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PostPosted: Mon Dec 26, 2005 10:23 pm 
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I agree with the Babooooom analysis but that relates to 1950's technology.

An actuator that uses a spring and diaphragm is useful with steam engines but I'm sure we have gone a bit further than that.

Electronic actuators can be controlled by signals from a map sensor and throttle position sensor. If you govern your wastegate by both manifold pressure and throttle position then you can eliminate the problem of a turbo runaway when the throttle closes.

Graham


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