List---The question came up among a few of us as to whether it is
advisable to rev a motor up near redline, when the motor is "unloaded".
I had thought this was not a good idea, but had no particular law of
physics to back it up. I consulted two of my favorite people about this,
and got two sort of different answers. Here's what Dennis Simaniatis
(R&T) and Kas Kastner have to say:
From: EngEd@aol.com Date: Tue, Jan 20, 2004, 4:08pm (PST+3) To:
tr6taylor@webtv.net Subject: Fwd: Motor Revving (From Kas Kastner, via
Dennis S
Hello, Dick,
Just in case, here's Kas' original message.
Dennis
From: "kas kastner" To: <EngEd@aol.com> Subject:
Re: Motor Revving Date: Tue, Jan 20, 2004,
The way and thing I was taught by respected hot rodders of the time was
that a high rev unloaded was just that, UNLOADED, meaning that things
were free to "wander" LIKE PISTONS AND RINGS AND ROD SIDE PLAY, THUS IN
A DIFFERENT PATTERN THAN WHEN LOADED WHERE THEY MUST STAY IN THEIR
RESPECTED AREAS. I believe it and would never run an engine at a high
rev unloaded. I truly beleive there is a little knowledge from the old
guys, and I mean a lot older than me.
----- Original Message -----
From: EngEd@aol.com
To: tr6taylor@webtv.net
Sent: Monday, January 19, 2004 7:46 PM
Subject: Re: Motor Revving
Hello, Dick,
With the exception of racing regulations, it's not true that
"revs are free." They evidently cost in terms of wear, fuel, etc. On the
other hand, I've never heard this jazz about not revving an unloaded
engine. I wonder if it began back before rev limiters? An unloaded
engine's revs obviously grow quicker than one with load on it, so maybe
people worried about going past redline.
A more sensible question might be "Why rev an engine to redline
if you're not going somewhere quick?" That is, I can imagine blipping a
throttle as part of warming up, especially if an engine doesn't want to
idle smoothly (because of high-performance specs, etc.). But this
doesn't involve revving to redline.
So my answer is "Provided redline isn't exceeded as overrun,
there's no essentially difference between revving an unloaded or loaded
engine. But why bother? Especially if you're not going anywhere."
Thanks for your query and your interest in R&T.
Cordially,
Dennis Simanaitis, Engineering Editor, Road & Track
Dick Taylor
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