At 03:43 PM 3/29/2000 0800, you wrote:
>Theo,
>
>Sounds like a simple, straightforward dyno system that should give at least
>very repeatable, if not accurate, results. The accuracy would depend
>primarily on knowing the exact moment of inertia of the flywheel, which you
>should be able to calculate to within a few percent. I guess they could use
>the electric motor to load the system and measure the electric power output
>that balances the engine's input, but that would involve more calibration
>factors. ....
>
>Bob
>
There is an easier way, just use the 347 motor, rated at 595.83241 Hp
to run the dyno. This will give you an exact calibration point. Then
you could prove that the 2 barrel 260 Tiger motor puts out exactly
446.4450334 Hp, give or take 1 part in 10^8.
Reminds me of the kid who was running his stock 289 at 9500
RPM on regular gas. He was getting over 500 HP (or so he said).
Now back to the real world: Would you assume that the
bearings used to support the dyno flywheel mass would be consistant in
their friction over time and temperature? Consider your comment of
calculating to within a few precent: A "few precent" (say 5%) would
cause you to be off by 20 Hp with a true 400 HP motor. Many dollars
have been spent in the pursuit of 20 HP.
From the articles I have read in Hot Rod and Popular Hot Rod
on the 347 conversion of a 302 as well as the prices I have seen for
the conversion, I would say it is not very cost effective.
One could add a turbocharger or a paxton type blower for a couple Grand
and get more power. Two to three pounds/sq inch of boost on a 302 would
be about equivilent to a 347 with no boost.
This guess is roughly based on 347/302= 1.15. Therefore a
total 14.7 Lbs/sq in. atmospheric times 1.15 = 16.9 Lbs/sq in.
Boost needed would therefore be 16.914.7 = 2.2 Lbs sq inch to have the
same amount of air going into a 302 as a 347 with no boost.
Assuming 5 Lb sq in boost or a total of 19.7 Lbs sq in. Then
the 302 would be equivilent to 19.7/14.7 x 302 = 405 cubic inches
with no boost.
Of course these figures do not take into consideration the heat
inserted into the boosted air. This heat lowers the effectiveness
of the boost. An intercooler between the booster and the intake
cools the air a bit and allows more Hp than the uncooled air.
The 302 could probably take 5 lb boost without major problems assuming
you have the fuel to match and an ignition system that has a boost
retard capability.
A lot of the 302 smog motors had an 8:1 compression. Using
a lower static compression allows more boost before problems occur.
The turbos generally can make more than enough boost once you get
up in the RPMs a bit and therefore a waste gate is generally
necessary to keep from blowing your motor up.
Has anyone out there put one or two turbos on a Tiger
motor without major cutting? There is not much room to route
the exhaust. However, compared to new cars , there is
a tremendous amount of wasted space under a Tiger hood.
James Barrett Tiger II 351C and others
