08/12/2003

Turbo Boost Control

One of the "problems" of the Mack Truck turbo, is that it is going to have
about zero backpressure.  Tom has repeatedly mentioned the effectiveness of a
controlled backblast of EGR to vaporize the charge and give smoother burning.
This I want.

The turbo is of course, buchi'd and I have found a regrinder for cheapness who
will regrind the cam for the enhanced overlap.  Whilst upon that subject,
increasing the overlap will probably not do a full scavenge like on an
aircraft, however, it will significantly cool the chamber, and will carry thru
some fresh charge into the exhaust at lower rpm and higher loads and
contribute nicely to spin up of the monster turbo.  Heck - its almost as big
as some of the stuff put on 1000hp rice rats!!!!  This is because of
revisiting lean charges - again courtesy of Tom, and discovering theoretical
base of 85% theoretical air having the same peak temperature of 140%
theoretical and possible other bennies.

Excess air will not be a problem with this turbo.

What we plan to do is place a electrically controlled butterfly in the exhaust
- just downstream of the turbo.  This will constipate the turbo quite nicely.
And, as a consequence, the back pressure will rise sharply.  Into a 50-60
overlap early opening chamber.  Which will not "do squat" as most of the fuel
is fired via sequential mechanical injectors after the exhaust valve closes.

But, we will have multiple cold start injectors, and we can trigger one or
more as needed, and the biomass controlled wet computer will reduce the
throttle feed to the sequential computer accordingly.  This will mean the
charge is "wet" and the reverting blast will "fuelerize" the charge.

And BTW, we will need a brake input on this - seeing how this is the method
Gale Banks use's ( a butterfly up the butt ) to grade retard largish rv's.

Both milage and braking from a crummy butterfly.  And now for the ginzo's, GM
also used it to control the EGR.  Nobody would consider EGR on a turbo'd motor
right?