Turbo LT-1

[Gary Derian]

Reciprocating pistons place an alternating compression/tension load on the
rods that is transmitted to the crank.  We all know that.  High rpm
increases these loads by the square of the rpm.  Gas pressure loads tend to
counteract the tensile loads on the piston every other revolution.  Too much
rpm will cause part failure.  Too much boost at a low rpm can cause the rods
to buckle.  You must balance boost and rpm to extract the maximum amount of
power from a given engine.

High boost/low rpm will buckle rods (not to mention bearing and crank
loads).  Low boost/high rpm will create inertia loads.  Each engine is
different, but factory redline ratings are a good clue as to the rpm
capabilities of the bottom end.  It is relatively easy to calculate gas
loads and derive a boost/rpm curve that creates minimum stress on parts.

Gary Derian <gderian at oh.verio.com>

> Yeah, Its true about the rpm thing....{kinda...}
> You see he was talking about the difference between compressive and
> inertial loads......
> like take a con-rod and try to push the big and small ends closer to
> each other....thats a compressive load.....now try to pull them
> apart....thats what happens whrn the piston applys inertial loads....
> so, if Force= Mass x Acceleration, then you can see that the inertial
> loads grow exponentially with increase in rpm.....{I did the math}.
> The thing is Corky forgot to warn about things like heat, and
> detonation, and ring end-gaps closing up....these are real; problems
> when trying to slap a turbo on an un-altered Lt-1.....thats the stuff
> that'll bite ya!
> >
> > >From what I hear in the responses, the GN V6
> > >was built bullet proof from
> > >the factory, so when you increase the boost,
> >
> > It is, and it isn't.  The fillet crank is a nice feature, and there
appears
> > to be a lot of speculation of a slight increase of nickel content in the
> > iron block, however the differences between the GN engine and the stock
> > engine is not that great.  In fact, the 4.1L N/A engine has the same
crank
> > as the turbo 3.8L engine, so the extra "neat" parts are worth something,
but
> > not all that much in my opinion.  Don't forget the journals in the 3.8L
> > engine are slightly smaller in diameter than the LT-1.  These are the
kind
> > of differences that have to be payed attention to.
> >
> > As far as slapping on a turbo to your LT-1, its very doable.  In its
stock
> > form, there is room to expand power, however you have to keep in mind
some
> > "reasonable" limits.  Keep the boost down, or build more boost at lower
RPMs
> > and keep the RPMs down. THis depends on your driving tastes.  In
general,
> > RPM's are what kills motors (that and lack of maintanence), and using
> > turbochargers merely lower the threshold of explosion on an identical
> > engine, but below that threshold, there is much more power to be made.
I'll
> > see if i can get the exact quote from my Corky Bell turbo book, but he
had
> > stated something to the effect that its not the boost level that kills
> > motors, but the RPMs that do.  he phrased it in a very clear way, and
I'd
> > like to share that with you.