Siamesed Runner TPI Questions...

[Doug Dayson]

Hmmm, I was under the impression that the difference in rpm potential between
two identical intakes compared on a 350ci and a 400ci would be approximately
500 rpm, as in the 350ci should see approximately 500 rpm more air etc. Is this
close?

As Bruce knows I'm happy with my power curve and rev range the way it sits with
the dual plane and the carb. I'm primarily looking for better economy and high
altitude performance, but if I can gain something in the switch to EFI I'll
take it (either a mid-range bump with TPI or better top-end with a
single-plane/TBI or MPI or Mini Ram).

Looking at the curves from the dyno runs below it seems as if the TPI intakes
made power to 6K rpm or a little better (on a 350ci crate motor). Would I be
correct in guessing that they would pull to 5500 rpm on a 400ci?

If so with my current power peak at about 5150 rpm it might not be so bad? I
generally shift at 5500 rpm or so and my shift recovery rpm is 3100 rpm in
first to second (3.06 to 1.62), and 3450 for second to third (1.62 to 1.00). To
me if I can improve torque from 3000 rpm to 5500 rpm I go faster, yes?

The Super Ram increases the plenum volume a lot over a TPI, is this what
supplys the extra air for higher rpm work?

Thanks...

Doug

Bruce wrote:

> Naaaa,
> IMWO, it varies on a case by case evaluation.
> For a new guy TBI will always be easier to build from the ground up.
> For a very large displacement engine, MAP is the answer, and cam/rpm will
> guide my response.
>
> 5+7 are mute in my opinion, most of the problems for them are cross
> fire/ignition.
> On a wet manifold, ya there can be problems, but generally at the higher rpm
> levels.
>
> I'd watch getting too short of runner.
> Heck, I advocated the connected runner idea for a long time now,
> What I would do if I were you is start measuring things out for the plenum
> volume and see where you are
> Bruce
>
> > This thread over here too?
> >
> > Its not for everyone... but it is possible to extend the range of the TPI
> > more to popular liking...
> >
> > Think of how the siamesed runners shift the curve. Now say "what if" the
> > runners were siamesed all the way down?  more shift. Now... hmmm.. what if
> > the siamesing was extended all the way INTO the base?  no need for large
> > runners or a ported upper intake now... cause you're drawing from 2 runers
> > simultaneously!  reversion is a concers, especially with #5 stealing fuel
> > from #7 in the cycle of things but cam overlap management can help here.
> >
> > Here is Mike's URL with dynos of some different TPI intakes.. including
> the
> > siamesed-base.
> > http://www.eecis.udel.edu/~davis/z28/winter01/dyno/
> >
> > again.. not for everyone... just another idea for the mix.. complete with
> > dyno data.
> >
> > Oh.. the siamesed-base dyno will be re-done soon. A problem was found with
> > the motor setup and is now repaired.. the dyno comparisons illustrate the
> > mod well enough (a zero dollar mod I might note) .. but the next set
> should
> > show more of an appropriate comparison. stay tuned! ;-)
> >
> > -Dave Z
> >
> > 89 Iroc - '730 - 383 large tube MAP TPI, ZZ3 cam ,dry NOS 50 shot.
> > 12.79 @106 / 12.08 @ 112.   www.delanet.com/~tgp
> > 92 25th annev convertible  305 / T56.  268 mph in a perfect vacuum.
> > ----- Original Message -----
> > From: Bruce <nacelp at bright.net>
> > To: <gmecm at diy-efi.org>
> > Sent: Tuesday, May 29, 2001 5:15 PM
> > Subject: Re: Siamesed Runner TPI Questions...
> >
> >
> > >
> > >
> > > > Researching EFI updates for 71 Vette with 406/400. 218 @ .050 110 LSA
> > flat
> > > hyd
> > > > cam with TFS Twisted Wedge heads and headers etc, currently a
> > well-dialed
> > > Q-Jet
> > > > and Performer dual-plane (hood clearence). Power peak is at 5200 rpm
> and
> > > the
> > > > torque peak is about 4000 rpm.
> > > > So, since TPI stuff is cheap I was wondering how siamesed runners
> would
> > > effect
> > > > the power curve?
> > >
> > > Just the oem stuff.
> > >
> > > > A stock or big tube TPI (with big manifold base) will kill power over
> > 4500
> > > rpm
> > > > with a 406ci, but I'd think that the siamesed runners would behave
> more
> > > like
> > > > the shorter runners of the Lingenfelter/Accel Super Ram as they're
> > > partially
> > > > open etc. What do Ya'll think?
> > >
> > > Still no plenum volume.
> > > If you happy with what you have how about, a TBI?.
> > > Maybe a  Weiand 7527, or 7546 manifold, then up grade one of them to TPI
> > if
> > > you want to progress further.
> > >
> > > > Would a Big Manifold Base/TB Siamesed Runner TPI set-up be able to
> > support
> > > a
> > > > 406ci through 5600 rpm?
> > >
> > > Would be a real push to even try
> > > Bruce
> > > > TIA...
> > > > Doug
> > >
> >
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