[torsen] Re: Turbo theory

John Petersen petersen007 at earthlink.net
Wed Nov 21 07:53:23 EST 2001

Engine control shouldn't be a problem. In my car the MAF is in the location 
which you would like to place the throttle in, so there won't actually be 
any metering changes. Also, in my car, if you were to quickly let off the 
gas and put in the clutch in this setup the RPMs wouldn't rise, as there's 
an electronic fuel cutoff when the throttle is closed above a certain RPM. 
Please notice, that your turbo won't necessarily grenade, it just may... 
and with proper design and testing that can be made quite unlikely.
         Blow off valves won't be that helpful, as they don't have anywhere 
to blow off from (the closed throttle situation is not boosted, it's 
vacuum, and you can't blow off vacuum).

         What is the application you are thinking of?

92 S4 mit Bosch motronic EFI

At 09:58 PM 11/20/01 -0800, you wrote:
>Dammit! Why don't these email have a proper "reply-to" built in to them?
>OK, so lets say you set up the wastegate to open whenever the throttle 
>closes. Is that feasible in a purely mechanical setup? Then, hopefully, 
>the turbo would maintain more-or-less the same speed while you shift, 
>instead of grenading.
>The problems that occured to me had more to do with engine control. By 
>putting the throttle so far upstream you would have the huge volume of all 
>the tubing and intercooler between the throttle and cylinders. First 
>problem: you'd need to fill it up when you step on it, which might be a 
>noticable delay (or maybe not, if the turbo is going fast). If you were 
>using CIS, would it go rich while all this plumbing is filling up?
>Second, when you let off the gas all this pressurized air needs to go 
>somewhere. So if you push in the clutch while releasing the gas, the rpms 
>would jump sharply. It seems that either a blow off valve or fuel cut off 
>would be needed to control this.
>This is about the time that Javad should suggest EFI, which would be a 
>good idea anyway.
>>In a message dated 11/20/2001 6:43:28 PM Eastern Standard Time, 
>>bdevlin at stanford.edu writes:
>>>Why is the turbo on my Audi upstream of the throttle? It seems to me
>>>that it would keep spinning faster and longer if it was in vacuum.
>>Because then the throttle would act as a choke to the turbo and could 
>>cause some real spin problems. If the turbo was spinning hard and the 
>>throttle is closed to shift, the turbo would be trying to suck thru a 
>>closed pipe and the results to the turbo and whatever entered the engine 
>>after breakup wouldnt be funny at all. To keep the turbo spinning faster 
>>and have it spool quicker you should reduce any intake restrictions and 
>>reduce exhaust backpressure to as near zero as possible (10lb range is 
>>excellent and I would love to have it) I run a K&N cone where the oil 
>>cooler used to be and gutted cats w/3" exhaust and have more work to get 
>>maximized. Reducing restriction in and out is the key, just like in an 
>>engine. More air in and out: more power for an engine, with a turbo, 
>>minimize the energy required to suck air in and reduce restrictions to 
>>pushing air out and you increase spool-up speed increase bearing 
>>effectiveness, reduce blade instability and decrease heat generated! by 
>>internal friction, all really good things.
>>If you decide to try the throttle first trick, let me know what happens 
>>but be on guard in regards to personal risk (dont stand too close).

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