It isn't just California dynos that have an optimistic attitude. My engine
dynos were Hennan-Froude and checked every week for correct balance. The
weight system is pretty darn hard to screw up. Fortunately I've had my tests
compared directly with the SAME engine on two different dynos at the Triumph
EXP dept. in ENGLAND and the results were amazingly close. Good
instrumentation and a good operator is required. No stones at anyone, but
don't put all types of apples in the same barrel. By the way, on my flow
bench the single 1.75" SU UNMODIFIED IN ANY WAY flowed as much as a 45 mm
Weber. But flow benches are another story not worth delving into.
----- Original Message -----
From: greg
To: FOT LIST
Sent: Thursday, June 09, 2005 10:29 PM
Subject: 225hp
I agree that any dyno figure has to be looked at carefully. Some
California dynos used to be pretty optimistic but I know that Dave
Rebello takes great care in keeping his calibrated before every run. His
240Z improved touring engines will make 240 hp on Hitachi 1 3/4" SUs so
two SUs/Strombergs will flow enough air for the 225 I mentioned
earlier for a 6. The cylinders don't breath simultaneously through the
carbs, each one calls for air sequentially and the TR6 SUs/Strombergs
were highly modified and had a few hours on the flow bench. Anyone take
a close look at an SU off a modern SCCA prod car lately? Hours of work
in every one. Also for those not familiar with SCCA Production rules,
the manifold was highly modified short of cutting apart and rewelding.
Production in the SCCA is nowhere close to stock. SCCA has showroom
stock for that.
One of the last engines Lee Mueller had for a customer that was
intended for the '82 Runoffs was claimed to be 235hp but it was running
a gear drive cam. I don't know how they expected to get that one past
the tech inspectors.
Horsepower isn't everything. Will the engine live? Will it be
tractable? Is the torque band flatter and have more area under the curve
in an engine with less peak hp? I'll take the less peak hp more area
under the curve engine. The 2 Stromberg engine is not as docile and has
peakier throttle response than a Weber carb version with the old DP 32mm
choke configuration but it will make good hp - within 5 -10 of the
Webers. A TR6 engine is affected by inlet restrictions less than some
due to the extremely long stroke and short rod. This is a characteristic
of any bad rod length to stroke ratio engine. Due to the extreme piston
acceleration it has a tendency to help get the air going and overcome
the inertia of the air when the intake opens. By the way don't bother
trying to stuff long rods in a TR6 engine. You can't make them long
enough to have any effect.
I've talked enough about TR6 hp because a friend of mine is still
running in SCCA and SCCA already thinks the 6 makes too much hp even
though now we get to breath through 28mm chokes which kills the 6. It
did stop us from wanting to shift at 7200 rpm though.
Greg Lund
|