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Date:         Thu, 16 Oct 1997 07:55:19 -0400
Reply-To:     mark keller <kelphoto@BRIGHT.NET>
Sender:       Vanagon mailing list <Vanagon@Gerry.SDSC.EDU>
From:         mark keller <kelphoto@BRIGHT.NET>
Subject:      Re: What is rpm @ 70 mph?
Content-Type: text/plain; charset="us-ascii"

> In order to keep him >from over-reving the engine, it would be helpful if he knew the rpms at 70 >mph, which is the top legal speed in this state. (Of course, all of us >remember that we never exceeded the speed limit when we were his age.)

My 91 Automatic at 72 MPH is indicating a RPM of 4000. However when you climb a grade I've noted about a 5% increase in RPM.

More importantly though, is that "over revving the engine" could mean, When do the Valve springs begin to fail, when do the rods grow, or when does significant wear begin.

Well the Red area is at the 5500 or so RPM. Thankfully I cannot report an idicated speed to go along with it. As far as "significant wear" A good rule of thumb is to keep piston speed below a 1000 fpm. That RPM for a 3" stroke of the 2.1 engine is 4000 RPM. It seems that at around and above this 1000 fpm piston speed the rings begin to resonate and increased wear occurs.

Another individual on the list stated that I believe a crankshaft center bearing would also wear at an accelerated pace at "high speeds", He didn't define high speeds, but did say that this phenomena was known for all VW flat engines.

I hope this helps

Mark Keller 91 Carat WLE Lazarus


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