Turbo Lag

[Mark Field]

On Sun, 03 Mar 1996 19:35:20 -0800 you wrote:

>At 07:40 PM 3/3/96, you wrote:
>>Maybe I've got the wrong end of the stick on this one, but it
>>appears to me that this idea uses a pump of some kind to produce a
>>tank of compressed air under low-load conditions. This tank of
>>compressed air is then used when needed, to drive a compressor to
>>produce, yes you've guessed it, compressed air. Once you've got
>>your tank of compressed air, why not regulate it and blow it
>>straight though your throttle body and cut out all those mechanical
>>losses inherrant in the second pump/compressor ? 
>>
>>                        Brian Warburton 
>>
>>>
>>>>Check this out, an air motor connected to a centrifugal blower. Air tools
>>>frequently turn at very high speeds. A mid size air motor might be the
>>>ticket. Imagine a small air tank and an electric or engine driven pump.
>>>During low load, the pump tanks the air under high pressure. When boost is
>>>needed, high flow solenoids open up and all hell breaks lose. Almost no
>>>parasitic losses and instant gratification! This should be possible with off
>>>the shelf components. As always, EFI would be needed to make the system
>>>really work. 
>>>>
>>> GMD
>>
>>
>I think you'll find that an air motor used to  spin up a centrifugal
>compressor would require air at substantial pressure (i.e. >100 psi).   A
>centrifugal turbine wouldn't have a prayer of delivering air at that
>pressure.  You'd need the equivilent of an electric transfomer to convert
>low-pressure/high-volume air to the high-pressure/low-volume air required by
>the air motor.....or else compress the air directly using a (gasp!)
>belt-driven vane or piston compressor.  The beauty of the turbocharger is
>that both the input and output sections are of similar "impedance" and no
>transformation is required.  
>
>                                                                            
>          Bill
>
>
>
Just my thought's on the subject of turbo lag.

First let me say that my car has a turbo ( Garret/ Air-Research E-5A
?). My car is a '86 Mustang SVO with the 2.3 liter engine. From what
I've read, and the people I've talked to, the snail (exhaust housing)
is the biggest culpret for turbo lag.

A small inlet increases the exhaust velocity allowing a faster spool
time. The down side of this is an increase in back pressure as the
engine RPM increases. A large inlet on the turbine side keeps the
exhaust gas velocity low, but allows the engine to breath better at
top end. A vicious circle it is.

I've also seen posts about the variable vane exhaust housing that was
available several years ago. From what I've read, and talking to some
of my racing buddies, these didn't pan out as the vanes either warped
from the extreme heat or failed to operate once the carbon deposits
started to develope. A good idea, but not enough demand to warrant
working out the bugs.

Here's my thoughts on how to reduce turbo lag.    Put the  butterfly
valve on the suction side of the compressor. If's there is little to
no air in the compressor( my car pulls 23 inches of vacuum at idle ),
it would take longer to stall the turbine. The down side to this, is
the fact that the intake track has to be filled and repressured before
boost can take place. But, with the turbine allready spinning from the
lack of backpressure in the inlet housing, you would think that the
turbo would spool up significantly faster than having to pedal uphill
against a manifold full of air.

I plan on trying this sometime in the near future when I can afford a
new set of injectors. Mine currently have a severe case of the cracks
from old age, and $600.00 doesn't come cheap.

Anyhow, just my thoughts.

Mark Field
mfield at mail.calypso.com
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