Sorry if some of you think this is dragging on a bit long, but Alan mailed this
to me for comment before mailing to the list then lost it!
So here it is an answer to Eric's question (the last answer?)
BFN
Dave B
72 BGT
76 Midget
Date: 11-Aug-1995 02:54pm
From: Dave Brooke
BROOKED
Tel No: 01923 664574
Subject: FWD: Re:Engine life at high revs
I N T E R O F F I C E M E M O R A N D U M
Date: 09-Aug-1995 06:47pm GMT
From: MX%"alban@psdb-tb.demon.co.uk"
MX%"alban@psdb-tb.demon.co.uk"@MRGATE@BROOK
Dept:
Tel No:
TO: BROOKED@A1
Subject: Re:
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Date: Wed, 9 Aug 1995 17:36:22 +0100
To: brooked@bre.co.uk
From: Alan Brooke <alban@psdb-tb.demon.co.uk>
Subject: Re:
>>How about this for an answer to Eric Lund
When car companies perform their relability tests they run engines and
gearboxes at full chat for the equivalent of 1000's of miles and expect
them not to break (often enough to cause warranty problems). A race car
using a basically standard engine wil be on full throttle for 65% of a lap
or more, the acceleration is not huge because it's standard so it takes
much more time to get up to speed than it does to brake back down to
cornering speed. Gear changes are obviously involved which gives temporary
respite from the incessant high rpm.
10 lap races at approx 1'30" per lap gives a total of 15 mins of which ~10
may be at full thottle, half a dozen races between rebuilds gives an
expected lifetime of about an hour at full throttle. OK I know this isn't
at steady max revs which is what you really asked.
The usual mechanical cause of catastrophic engine failures is due to
fatigue of the con rods or their bolts, sustained high rpm causes more
stres reversals in a given time than lower rpm therefore components reach
the upper limits of their fatigue lives quicker. I would still expect the
mechanics to last more than 20 mins.
The biggest problems are probaly caused by the cooling and/or oil systems
not being able to keep the temp down after a couple of minutes flat out,
oil starvation certainly wouldn't help reliability
I have heard a story which ran along the lines of: a Beetle rally where an
engine, with the cooling fan taken off, was fired up with the throttle
wedged wide open, after 1/2 hour or so it stopped. Investigation showed a
spring had dropped off and the throttle had shut. This fixed another hour
or so passed before it ran out of petrol, refilled it ran for another hour
or so then fell apart!
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