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Re: Rev counting and limiting

To: WSpohn4@aol.com
Subject: Re: Rev counting and limiting
From: mgbob@juno.com (ROBERT G. HOWARD)
Date: Mon, 23 Feb 1998 12:43:15 EST
Hi Bill,
  A catalogue from Pegasus Auto Racing Supplies appeared here Saturday.
Page 51 has MSD Soft Touch Rev Control "designed to be used on standard
points ignitions or on non-CD applications." $139.99.   There are no
illustrations, but a call to 800-688-6946, or pegasus@execpc.com might
elicit some information of value to MGs of all sorts.  They have a more
expensive unit that cuts out one plug at a time as the revs reach the
limit. 
  Either, of course, would be ideal for your prank of reducing another
guy's rev limit.
Bob


>
>Allow me my .02 in regard to 'T' type matters of which I know 
>relatively
>little. Some of the racing experience might cross over.
>
>First, generator driven tachs - not very good! As stated, for 
>competition use
>at higher revs, a larger pulley is normally fitted, which throws your 
>tach
>off. In cars that rev higher normally, like the Twinkies, we have 
>sustantially
>larger stock pulleys just so tht the generators don't puke their 
>windings as
>often. 
>There are two alternatives - fit an electronic tach, or, the one I 
>think I'd
>favour for a 'T' type, if it works, - fit a distributor with a tach 
>drive in
>it. I've done this on the later MG engines - you simply need:
>
>1 - a TR 6 distributor
>2 - the breaker plate and weights from your MG distributor (so as to 
>get 4
>cyl, and the right advance curve
>3 - someone that can make up the correct (smaller) end for the 
>distributor end
>of your tach cable
>
>This sort of arrangement will be accurate unless you somehow manage to 
>destroy
>your distributor, in which case tachometer accuracy will be the least 
>of your
>concerns.
>
>Next question - rev limiters. I have in the past used the following:
>
>1 - rotor from a Rotus Cortina - mechanical limiting at 6500 rpm, 
>adjustable
>if you need to by carefully changing the weight of the limiter slug by
>removing/changing the tiny screws in it or grinding the weight itself. 
>This
>set up has a weight that is attached to the centre of the rotor by 
>little
>springs. The faster the engine turns, the farther out the weight goes, 
>until
>(you guessed it - at 6500 rpm) it touches a stop thus grounding the 
>spark and
>limiting the engine. Works great, probably hard to find now, and 
>likely
>expensive. Good for the traditionalists. I have also seen a 6 cylinder 
>model
>that limits at 4500 rpm, if there are any Austin-Tractor,  sorry, 
>Healey
>owners out there.
>
>2 - Use an electronic limiter. I use an MSD unit which also, of 
>course, gives
>much better spark. The rev limiting part is adjusted by changing 
>little two-
>pronged plastic bits into a plug on the outside of the MSD unit. They 
>are, as
>I recall, available in about 200 rpm increments. By the way, it is 
>great fun
>to sneak over to a friend's car just before a practice session (not a 
>race -
>not sporting, you know) and slip a 6000 rpm chip in place of the 6800 
>one that
>was in there. Wonderful puzzled look on his face as you pass him at 
>the end of
>the straight!
>These units are reliable and very useful for their spark enhancing 
>properties
>as well.
>Best mounted, I think, under the firewall or somewhere else out of 
>sight, so
>as not to look too out of period for the cars. Obviously only useful 
>if your
>rules allow them (otherwise they must be mounted _well_ out of sight 
>:)
>
>Bill S.
>(Twinkie with MSD, TVR with Rotus Lotor)
>

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