[Land-speed] Sorta off-sorta on-topic..turbocharging theory

[Ray Buck]

At 01:37 AM 11/14/2007, Jon Bishop wrote:
>On Nov 13, 2007, at 5:32 AM, MEIERLE Mike wrote:
>
> > Isn't some of this happening during valve overlap? It's not really
> > sucking the exhaust out but actually pushing it out during this event.
>
>Turbochargers don't like overlap. The less overlap in a turbo car the
>better.
>
>Beyond that, I'm not sure I quite understand the original question.
>Could you reword it so that I might understand what it is you're
>trying to accomplish?

Hmmm...let's see.  The original question was about using a 
turbocharger to improve the performance of a motor that had a 
limitation of valve size because of a relatively small bore.  A Chevy 
305 in particular.  A friend is considering dropping one into his 
son's 76 Nova to replace the tired original motor that's in there now.

It seemed to me that using a turbo would force more air/fuel mixture 
into the cylinder and mitigate the problem created by the small 
intake valves.  I know it's not a "proper" way of going about curing 
that problem (a 350 or 400 smallblock would be the route I'd 
take.)  But as a mental exercise (and because the kid's first 
reaction when he heard about the new motor was, "let's put a blower 
on it!") I began to think that while the intake side might be helped 
by cramming more mixture in, there was no real way of dealing with 
the exhaust side and wondered if it might be a bottleneck to the whole thing.

Then I began to consider what might be done to help the exhaust flow 
a little better.  Porting and well designed headers would seem to be 
a good start, but I wondered if there was a way to scavenge the 
exhaust from the cylinder and still use it as the means to spin the turbo.

As I considered further, I wondered if a second driven impeller on a 
turbo might be used to suck the exhaust out of the cylinder and force 
it into the turbine side of the turbocharger.  I know it sounds like 
a Rube Goldberg type of perpetual motion thing...but who 
knows?  David Adin reminded me that "nothing is free" and I'm aware 
of that, but still, I wonder if there was a way to help extract the 
exhaust through the exhaust valve by assisting it in the same way 
that the mixture is forced through the intake.

I hope that's a little clearer.  If not, maybe we can just chalk it 
up to the pain meds as the result of some oral surgery. :)

RtR