Turbo Bypass

Greg Hermann bearbvd at sni.net
Fri Aug 14 01:04:09 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.

I,ve got two copies of the McInnes book. I'll look to see which revision on
each. Didn't the ACCEL setup bypass compressed air back to the compressor
inlet? Foggy memories. Ain't it funny how folks who get in the habit of
building junk can't seem to break it? Maybe we could start up a twelve step
program for them!

                                        Regards, Greg
(Off for a week vacation tomorrow AM . Se ya in a week.)





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