In a message dated 5/23/2003 5:47:23 PM Eastern Daylight Time,
alventures@email.msn.com writes:

> Of course you're wise to be skeptical Al, but it's unrealistic to
>  expect a dyno sheet on every engine that's sold at these prices.
>  
>  Of course not every engine - just on one - unless there is something
>  significantly different. We're not talking about a big amount of money
>  after spreading it out over a few engines.
>  
>  Al
>  
The dyno run should be made with what intake system installed?  What exhaust
system? In the case where all of the end items have identical systems, then it
would be helpful to dyno each engine. Everyone could expect the same, or
similar performance. But that is not the case at all. Nearly all of the props will
be different, and many will be a poor choice for the application.

Each person could dyno their own installation but to what end? You would want
to assemble it just the way it will be installed in the airplane. This is
almost never possible because of the layout of the dyno mountings. Often a
special exhaust system must be used to clear this or that on the dyno. Let us
speculate that your new engine arrives and you rush it to the local dyno shop, who
just happens to have a rotary setup. With your home made 4 tube intake and
exhaust system installed, you play with it all day with the local expert helping
you make change after change, adjusting the timing for each setpoint of each
run. At the end of the day, you have found that Max power demands too much spark
lead and too much heat. Better to settle for less power and manageable heat.
While water and oil temps are controlled on the dyno, there is no ram air for
the induction system to replicate the motion of the airplane. So this data is
going to change on the airplane in motion. The testing goes quickly because
you only need data between 5,000 and 7,000 RPM. You might get 15 passes if you
and the dyno guy are very good, and nothing at all goes wrong. Now you have 15
pieces of paper to show your wife, and a day and $500.00 is missing from your
life. You will learn all kinds of interesting stuff about engines. The dyno
guy will like the change from and endless parade of Ford and Chevys. If you have
not done this before, it is required for every motorhead. You will notice
that much of the engine noise is not from the exhaust system. Just the pieces
flying around at speed and the combustion process heard through the metal of the
engine.

 The best 13B I have heard of is about 310 HP at 9,300, with bridgeports.
Daryl Drummond. GT-2. Without bridge ports, (big street ports) 228 or 229 HP at
9,000 RPM in E production, Stanley Lizauskas and Daryl Drummond. My Drummond
race engine (a 12A) had 173.3 HP at 6,500 RPM. Max power was 244.9 HP at 9,400
RPM.  A friend did dyno his 13B last fall with very small bridge ports and
after a day of tuning got up to 259 HP at 9,000 RPM. I have no data below 6,500
for a 12A and nothing for a 13B beyond what is above. I can post the dyno sheets
from my engines as soon as my wife shows me how to get them out of Paper
Port.  



A bridge ported engine can have the same intake closing point as stock, but
the overlap period goes way up. (intake and exhaust open at the same time). I
think Tracy can go as fast as the airframe can stand with a bit of porting.

Lynn E. Hanover