Twin Turbos (Massive snippage safe to read)

[Bruce Plecan]

----- Original Message -----
From: Frederic <frederic at xephic.dynip.com>
To: <diy_efi at efi332.eng.ohio-state.edu>
Sent: Tuesday, April 24, 1990 10:38 PM
Subject: Re: Twin Turbos


> Turned out
> my GM ECM is bad, so I'm seeking a 730 ECM and Andy Quaas and I will be
> sharing notes since we are working on engines with about the same
> displacement.

I'd recommend ya look for a 749 instead.  Running a 2 bar program would be
MUCH better than a 1 bar.

Would allow for much better boost control.

Sneeze valve for a Truck, might be disaster...  (Doc+Grumpy already taking
bets).

> On the back side of the plenum, there is aan ATR adjustable
> sneeze valve, which will be set for 10psi so that additional pressure
> over that setting will blast out into the open area.  I think its ATR.

Usually/Often a sneeze valve is for a high rpm+high load limit (often
trimming, rather than absolute control).  If I understand you right your
wanting a low rpm monster.  It might take a ton of work to limit/modulate a
sneeze valve for this.  Using the Wastegate signal off of the syty 749 would
be one option.  But, Intake tract boost control often winds up a bang/bang
affair.  Meaning anything wrong, and it flucctuates greatly.  Just getting
it right on a 400 CID is gonna be work, and since EGT reflects work done,
heavy payloads might drive ya around the bend...
Might think of using a EGR as a spill valve,  would be to be electric not
vac operated (ie newer Digitial type)

> Corky Bell's
> rule of thumb is 350 cid.  Anything 350cid and larger, requires two
> turbos, whereas below that line, requires one turbo.

One think about sweeping statements is that they are usually wrong.
Bruce