Frederic Breitwieser/turbo discussion

[Frederic Breitwieser]

> Ok, I'll start!

There is a certain responsibility with going first :)

> I was mulling around a little idea I had about my Pontiac.  It's in the
> garage with no fenders, the 400 looks pretty bare, with no harness or
> plumbing.  I have a spare (used) turbo sitting there from my old Mustang
> ('84 GT350, turbo4) and have been contemplating adding this along with efi.

Its my school of thought to add the EFI first, get that running suitably, making
sure your EFI configuration is upgradable to the additional boost, either by a
larger MAF or a 2 or 3 bar MAP sensor depending on your configuration.

> Then I thought about a setup something like the original post about the
> variable exhaust system.  I was thinking about a relatively small turbo
> driven by one bank, to get the boost rolling, then a pretty large turbo on
> the other bank that would take over at higher rpm's.  I didn't get into the
> pro's and con's yet.

I spent a lot of time with several friends of mine trying to achieve the best
bottom end combined with an awesome top end on the Buick V6 twin-turbo.  For
scavaging purposes, you want the exhaust restriction to be about identical on
both sides of the engine, so sizing a smaller turbo on one side and a larger
turbo on the other will cause ineffective scavvaging on the smaller turbo side,
unless you achieve a bypass.

We tried running two small 1.6L Subaru turbos off each side, but they weezed out
pretty low in the RPM band (about 3600-3800 RPM on the Buick).  So, we then
daisychained larger turbos (TE44) in series on the exhaust lines... however the
smaller turbos "got in the way" at higher RPMs exhaust flow wise.  So, we got a
little crazy and used four of those cast iron JC Whitney exhaust bypass thingys
and put one fore and one aft on the smaller turbo, so at low RPMs the smaller
turbos were working hard, flowing its waste into the larger turbos to keep them
somewhat spooled.  Then, at 4000 RPM, we'd cut all four bypasses so the smaller
turbos were "out of the loop".  This worked very well, and increased power more
broadly across the RPM band.  The problem now is how to control these mechanical
valves.  Also, this is just the exhaust side of things, we hadn't really done
anything with the intake side... we just monitored RPMs of the engine and where
the turbos small or large stopped making any additional boost, or started to
overspeed.  Plumbing was a nightmare, and certainly the weight of four turbos
plus four cast iron cutouts was not exactly something we wanted hanging off the
headers.

So, the small turbos went, and we used the two TE44's and at 6200 RPM, we blew
the crank apart and testing continued on a second engine.

We also experimented with nitrious for lower RPMs, triggering it in the
1500-3000 range thus giving more punch before the turbos are at max boost, and
this also worked very, very well.  Using the aftermarket ECMs (Haltech in this
case) you have a general purpose output which you can use for Nitrious solenoids
or fangle up an injector driver circuit to drive additional injectors... solder
away my friend.

We ended up with three injectors per cylinder... first two were 93/94 octane
gasoline, the third was an 80% alky 20% distilled water mix from a seperate tank
and worked very well.  This is very similar to what I will be doing on my 383
stroker (431 cid) Mopar block during the spring as the parts start to come
together.

Hope that helps ;)

--

Frederic Breitwieser
Bridgeport CT 06606

1993 Supercharged Lincoln Continental
1989 HWMMV w/turbocharged 500cid Caddy
1975 Dodge D200 Club Cab soon to have 431 stroker + turbos
2000 (I hope) Buick GTP (Mid-Engined Sports Car)