David Morris wrote:

G'day Paul

Question for all you engineering types. My friends & I  have been
debating on the validity of warming up a rotary engine prior to placing
load on it. In our case it's for driving off in the Cosmo or RX-7 but we
are all "in-the-habit" of doing this.

We all know the difference in temperature co-effecients between the side
plates, rotor housings & rotors but have recently been told (by some one
worth listening to) that warming up simply adds to excessive carbon build
up with no other benifits & that one should simply drive away
immediately.

We are all in the habit of starting & driving away in our piston powered
cars but what so for the rotary versions.??

REgards
         David

You got motor oil going in there and EGR. I don't know the sched
for EGR vis a vis warming up so I could no say for cars.

In our case we mix two cycle oil with the fuel and disable
the EGR. Both with the idea of eliminating the carbon
build up.

But I will tell you putting a heavy load on a rotary while
cold is bad news. I am not talking about shock cooling and I don't
really think that happens.

One of the things you have to worry about in the rotary is
the rotor housing expanding faster than the tension bolts.
You need those bolts as warm as possible when applying full
power to a rotary. This scenario is reputed to cause
shrinkage of the rotor housing after the engine cools off.

Driving away is probably not bad but a full power accleration run,
climbing a steep hill, or a top speed run should be out of the question.
Cars don't need much HP to drive away. Even the freeway is
only about 30 HP in most RX7s.

In an airplane a takeoff run is full power for up to 5 minutes.
Always warm it up well before takeoff.

Paul Lamar
 
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