Turbo Bypass

ECMnut at aol.com ECMnut at aol.com
Thu Aug 13 12:40:49 GMT 1998


In a message dated 8/13/98 12:22:22 AM Eastern Daylight Time, bearbvd at sni.net
writes:
> High RPM low load might be able to do it, Part throttle, low RPM definitely
>  won"t. You'v got me tempted to run some numbers (another ten Excedrin
>  headache) to explore the situation, but I doubt it would happen. There were
>  an awful lot of draw through conversions built in the carburettor days, and
>  not even McInnes mentioned the possibility, and he was always pretty
>  careful and conservative.

I think you may be right on the part throttle aspect..  I'm questioning my
reccolloection of the problem after 15+years.   I know it involved overspeed..
My "fix" was to get rid of the goofey .69 exhaust housing that Accel sent with
the smallblock chev  conversion kit.  I went to a .96 AR exhaust housing & it
was much better.   Not long afterwards, I yanked it, and insatlled 13:1
pistons, a rowdy cam & headers....The car was more reliable with the turbo on
the shelf in those (pre digital FI) days.   Still have the good (big) turbo on
the shelf.. It's an AiResearch TO4B / V1 trim.  Good for 4.5 to 5.5 liter
applications (wana buy it?)..  There has been at least one revision of the
McInnes book.  The earlier edition mentioned "some" nagative aspect of
Accell's draw-through set up.  If not overspeed, then it was unwanted charge
heating.  I though it was overspeed though..  It was in the text box, below
the diagram of the Accel setup.  I'll see if I have the remains of that book
somewhere if you want.  When they revised the book, they left the Accel fiasco
out altogether..  There was this huge butterfly near the compressor inlet that
would start to close when desired boost was achieved, instead of a wastegate
opening on the exhaust side.  Come to think of it, that was the overspeed
culprit, not the carb.  Restricting compressor inlet airflow (removing
compressor load) , while failing to dump the exhaust, which was driving the
whole thing, caused stellar shaft speed numbers..
Sorry, was mistaken about the carb causing the overspeed..
Mike V.




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