[Shotimes] rod bearings

[Donald Mallinson]

Jim,

I know that lugging for a car generally does NOT have the 
condition that speed/rpm drops even though the throttle is 
open.  That just about only happen in a car when going 
uphill.  An airplane has a lot more going on dynamically to 
stay in the air!

When I bought my first and only RX7 (first gen body)  I was 
told by a long time Rotary mechanic and racer to NEVER lug 
the motor, keep the rpm's above 2500 at all times if possible.

I did and enjoyed the car till selling it at about 150,000 
miles.  Motor had never been opened up.

Secretary type that bought it was cautioned strongly by me 
to never lug the motor and I demonstrated what I meant, but 
sure enough, I could hear here drive by my city square 
office every day at what must have been 1000 rpm  or less in 
fifth gear trying to get up some speed.

In less than two months she was calling complaining that the 
motor seals were shot, and local Mazda dealer was talking 
LOTS of bucks.

I got her hooked up with some other RX7 racer friends of 
mine that bought the car and then took it racing with a 
fresh motor that lasted for years.

I also drive my SHO at or below 2000 rpm a lot.  But when it 
comes time to pass or get up some speed, I either use small 
throttle openings, or downshift.  Especially if I come to a 
stop and get at or below 1500 rpm, and the light changes, I 
downshift to save my bearings.  Trust me, this is good advice.

Again, just cruising is not the problem, but trying to gain 
speed with a LOT of throttle at very low rpms.

Don Mallinson

Jim and Debbie Leyden wrote:
> Thank you Don.
> 
> A few months back there was a discussion on here in which several people
> defined "lugging" as running below 2000 rpm.  I was a bit confused by this
> since I was taught in the military that lugging was a condition best likened
> to an airplane stall.  An engine is considered to be lugging when the RPMs
> continue to drop even though the throttle opening was increased.  That is
> the reason I responded the way I did.  IIRC there was no mention made of
> throttle opening in that former discussion but the number 2000 RPM was
> tossed about considerably.
> Personally I drive my SHO below 2000 RPM all the time.  I cruise in 5th at
> 45 MPH on the way to work on a nice flat stretch.  I also run the engine to
> 7000 RPM almost every time I leave a stop.  I don't think that my driving
> style contributed to early bearing failure.  After all 200,000 miles is
> really not too bad for ANY motor.
> 
> Jim
> '93 MTX
> and 238,000 before replacing the transmission