Bob D.,
I try to cruise at 3300-3500 rpm. The engine seems to run smoothly and
happily there and, until recently, it was fast enough with my gearing to
unduly avoid obstructing overtaking traffic. Now that the legal limit is
65 in CT and the usual travel speed is in excess of 75, I am resigned to
driving on the highways the few hours a day that traffic is light. My
Toyota pickup turns its 2.4L engine 2500 rpm at 70 mph.
The 2500 ft/min rule for piston speed has been around since the 1930s
I know and the 1920s I guess. For our TD and other XPAG engines, and
those with 90mm stroke, it's near 4M rpm. The idea is that it's a
maximum sustainable piston speed above which engine wear is increased
rapidly. An interesting exercise would be to work it out for different
engines and to compare the RPM for them.
September 2003 issue of Thoroughbred and Classic Cars has an article
on the Bugatti type 35 engine. Its first iteration had 60 mm bore (same
as XPAG) and 88 mm stroke (XPAG is 90). The article does not mention max
RPM, but my recollection is that they were, max, 5M engines.
Bob
On Tue, 26 Aug 2003 22:28:01 -0000 "Bob D." <bobmgtd@insightbb.com>
writes:
> Andrew:
>
> If you can buy/borrow a portable GPS, you'll be able to measure
> your speed to an accuracy of 1/10th mph. You can also use it as an
> odometer, and of course it will show you where you are any where in the
world.
> (It's like magic!)
>
> The rear ends of the T series are really short, even for the
> period in my opinion. I have a TD with the stock 5.125 rear end. It
takes 4500
> rpm to go 60 mph. Does anyone know of any other car manufactured in the
> '50s with gearing that short? But, I have cruised many thousands of
miles at
> that rpm, and the engine keeps coming back for more. I never cruise
beyond 60
> mph, because that exceeds some rule of thumb about not sustaining a
> piston velocity above 2500 ft. per min. Has anyone else heard of this
> piston velocity rule?
>
> I'm really curious about how fast other T owners cruise. Please
> reply.>
> Bob Donahue (Still stuck in the '50s)
> Email - bobmgtd@insightbb.com
> 52 MGTD - NEMGTR #11470
> 71 MGB - NAMGBR #7-3336
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