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Actually, Rusty. I have always been fuel
injected. My first manifold was using 50 mm twin throat TMW Webber
throttle body (with 4 injectors), a racing beat webber DOE manifold which I flew
on a 86 six port block. I only had one flight on that engine with the new
(longer smaller diameter) manifold before my HALTECH fuel injection system
failed, so did not get a good comparison. However, on that one flight with
the old engine and new manifold I did note that my rate of climb increased by
300 fpm over the old manifold. Certainly not a conclusive nor exhaust test
and comparison, but enough to convince me to keep the new manifold when I
installed the turbo block.
In just about every theory of induction tuning I
have looked at (and its been quite a few), if they agreed on anything - it
was longer, smaller diameter tubes favored torque at lower rpms and short,
larger diameter tubes favored power at the higher rpms. Again, we are
talking about attempt to get an optimum match. That does not mean an
engine will not run nor produce power with less than an optimum setup - it just
simply won't be "optimum". And as I mentioned in an earlier e mail, there
are other considerations that may make a less than optimum setup desirable or at
least the lesser of the evils faced {:>)
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
Sent: Saturday, April 17, 2004 6:23
PM
Subject: [FlyRotary] Re: intake
ideas?
The question of
tuned runners is ‘how much is the benefit?’, and ‘what do you want to give up
for it’.
Thanks to you
both for the comments. I think Al hit the nail on the
head with the above statement. There are so many compromises that
have to be made, particularly when you don't have much room to work
with. It would be great to see a direct comparison of a short intake vs
a nicely tuned one. AFAIK, no one has done that. I know Ed
had a short intake in the past, but I'm thinking that he changed some other
major items (engine or fuel injection system?) at the same time he changed
intakes, which would invalidate the test.
I also agree
about the injector placement, and I'm starting to think the best
arrangement is either to have the primaries in the block, and secondaries
in the TB, or all four injectors in the TB on a short intake. Since
I have both a 2 and a 4 injector version of the TWM TB, I guess I can go
either way on the next
iteration.
BTW, Al, did
you make that intake? It's beautiful!
Cheers,
Rusty (wishing
I was home where I could start working on the new
intake)
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