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In a message dated 5/23/2003 9:56:37 AM Eastern Daylight Time,
13brv3@mchsi.com writes:
> Pardon my questioning, but until you see the dyno data, it is just a
> guess. I'm sure it's possible, I just don't think it's helpful tossing
> numbers around that haven't been measured. Personally, I can't quite
> imagine being an engine supplier without having access to dyno to test
> the product.
>
> Of course you can lie with data too.
> -----------------------
>
> ===> 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. Also, as
> you mentioned, if a supplier wants to inflate the HP numbers, they could
> give you a dyno sheet to back up any claim they make. I believe Bruce
> builds a great engine, and I don't believe he's making any wild claims. I
> also imagine that he'd be happy to sell engines without giving any HP
> numbers, but we as customers won't accept that. I'd be willing to bet that
> his engine will produce pretty close to what he estimates, given a good
> tuned intake and exhaust system.
>
> Back to the point of the original post, this guy has a great engine for
> sale, at great price. I've even given some thought to buying it myself,
but
> I just can't justify having another engine laying around.
>
> Cheers,
> Rusty
>
>
>
Years ago, one of my 148 HP Fiat motors could out run a 160 HP motors from
California. While we did discover that California horses are a bit smaller than
Ohio horses, this was not all of the story. I spent $2,000.00 for my Stuska
dyno in used but fair condition. Today, I could buy a nice rental property for
what a dyno costs.
You learn what works and what doesn't work on the dyno. I will never build
another engine for sale to anyone. The interpersonal trauma is not worth any
amount of money. There is always a person who will believe that this new multi
thousand dollar part will solve any problems they may have in life. It is just a
part. Like any other part of your puzzle, it will perform or not perform as a
result of so many other items being done correctly to support it. I built up
a Cosworth FVC engine for a friend who later sold it to another racer. While
we ran raced it, it performed flawlessly.
The subsequent owner got 5 laps out of it before it needed a very extensive
rebuild.
While that owner was yelling at me about being the worst engine builder on
earth, I noticed that the radiator cap was missing. There was no water in the
engine. As reliable as they are, a Cosworth will not last long without water.
It is very difficult to get all of the air out of a Cosworth, and the same is
true of a rotary. The center cast iron used to have a sensor in a flat spot
on top. I used that for a water temp port and it was great for letting air out
of the block. The stock water pump is mounted high on the block, and it will
not pump anything at all if it can get some air close to it. It must be
completely submerged.
Bruce cannot control what happens to his engines after they go out the door.
In many cases, you can predict that one person will have no problems at all,
while another will be on the phone for years.
If I had a choice between buying another dyno or a really great flow bench I
would buy the flow bench. The results read in CFM and that is HP. You can rig
up all sorts of tests and situations. You can make dozens of changes with
modeling clay and never get out of your chair. How much time would that take on a
dyno?
The rotary is very sensitive to exhaust runner length. It is less so for the
intake. Notice the stock intakes are very short. The newest engines are using
very complex systems to get closer to ideal length for any RPM range. Until
you are looking for the last few HP at the top, port timing is not as big a
deal as runner length. If it looks good the rotary will love it. If it looks bad,
the rotary will punish you. The manifolds being built up on some of the web
sites where individual tubes are being run to each port, look good. There are
several exhaust systems that work well. Due to space limitations, the short or
medium systems will be used in aircraft. Both primary runners the same length
is very important. The run to a muffler a smooth long run, and a muffler with
minimal back pressure.
Do it right and you may get 170 or 180 HP. Do it wrong and get 145 to 150 HP.
But even so, air plane engines are hopelessly over rated. In a Cessna 150,
the is 79 HP available.
Many engine builders will go to races and assist customers with tuning at no
direct charge. You paid for this in the engine price. For airplane engines,
this is nearly impossible. You may make a special deal to do this, but it is not
likely to happen. So it is the responsibility of the new owner to equip him
or herself with the knowledge required to support that engine in every area.
A direct comparison of HP is not possible without the dyno, but if all you
want to do is beat a similar aircraft with motor X,Y or Z, then a time to climb
to a specific altitude would work well. You can build in a torque measuring
device in the motor mount, and have a built in dyno. The old radial powered
transports had this.
Best power should be available just rich of peak EGT, so Tracy should have
some additional speed in the bag. Keep in mind that at very high EGTs you can
damage the apex seals. So just don't go there. Find out what it is and stay away
from that point. For racing we want to stay rich of peak a good deal. We mix
oil and fuel, so more fuel means more lubrication. Also, there is a very
slight amount of fuel cooling.
We want to stay below 1600 degrees on the rich side of peak EGT. Some racers
run higher than that without problems, but Mr. Drummond (our engine builder)
says 1600, so that is what we stay below. But I run on again.
Lynn E Hanover
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