<VV> 3-Speed Corsa and Spyder

[djtcz at comcast.net]

http://www.vv.corvair.org/Library/benzinger.htm 

Benzinger said this - 

"We wanted rather desperately to match up a turbocharger with an automatic transmission. It has some pretty attractive aspects about it. But we just could never make it go. The thing that you run into - and maybe some of you have even experimented yourself with this combination - is that when you wind up the engine in low gear, get the turbine wound up to full boost and then make the upshift, it suddenly pulls the engine RPM down with the boost still up where it belongs for a couple of thousand RPM higher. With the low engine speed and the blower still wound up, it gets into combustion difficulties that makes wild detonation look pale. There was just nothing we could do to get the engine thru this rough spot. Once the malcombustion starts, you can't just shut it off again. Perhaps the availability of a three speed automatic or maybe a four speed would have done it by getting the gear steps tighter. But with Powerglide being a two speed set up we could never find anyway around it." 

I take that to mean the issue was maintaining bigboost airflow when the engine rpm changed almost instantly , not the large rpm drop per se. 

powerglide ratio 1.8, softened a bit by the torque converter. 
Early 4 speed drop on the 1-2 shift 1.55, with direct rpm change, but with a noticeable period of closed or reduce throttle between shifts. 
My recollection is the boost has to build back up between even my quickest shifts. 

Long ago A New England racer used a Turbo PG combo in a dune buggy (Meyers Manx maybe) in some form of oval track or circuit racing pretty successfully. 
At one point he claimed he was using one of the factoery hot cams and did not feel the need for "more," 
I do not recall him mentioning special tuning or driving during the 1-2 shift back in those non-digital days. 

Dan T 

====================== 

From: RoboMan91324 at aol.com 
Subject: <VV> 3-Speed Corsa and Spyder as rare as MONO "Sgt Pepper" 
LP? 

Beside the undesirability factor, I imagine that another reason for a 3 
speed being rare is that it would cause similar problems (but maybe not quite 
as severe) paired with a turbo as a 2 speed automatic would have caused. 
Specifically, too much RPM drop between gears. I understand that no 
factory turbo motors were paired with 2 speed automatics for this reason. I 
suppose the 3 speed would work OK with the 140 Corsa but were any 3 speed 
Spyders or turbo Corsas available from the factory? If so, any feedback as to 
performance? Was the 3 speed tranny/turbo combination one of the 
"standards" that GM disallowed at the factory whether you wanted it or not? 

Doc 
~~~~~~~~~~~~~~~~~~~~~~~ 

I