mr.espresso

Hi I just recently bought a used 1979 mazda rx7 with the 12a engine. I went to start it up the other day and it started and the rpm's shot straight up. I made sure i had not bumped the choke out i do not know anything about cars and i was wondering if someone had had similar problems.

malachiward13

It depends on how high the rmps went up to. But a lot of rx7s start up and begin to idle high between 1500-2000, then it goes down after about 90 seconds once the engine reaches normal running temps.

diabolical1

iTrader: (3)

welcome to the board.

how high do the RPM go once it fires? does it remain there or settle into a normal idle?

Driftslut562

My 79 rx7 idles at 1700 till it warms up then it jumps down to about 700... Is that normal??

diabolical1

iTrader: (3)

with the choke activated? yes.

kraneous

yeah, like other have said, RX-7 engines rev high until they are warmed up (1500-2000 rpm) and then will fall back down to normal idle rang (700-800 rpm) once they are warmed up. You shouldn't drive your car while it is warming up...rotary engines are very fragile when they are cold. You should also NEVER turn the ignition off while it is in it's "high rev" warmup state because you will FLOOD THE ENGINE. They are relatively easy to un-flood but just let it idle down before you turn it off or drive after starting it.

diabolical1

iTrader: (3)

absolute nonsense.

it's not a good idea to be redlining and/or beating on the engine until normal operating temp, but you can drive the car just fine. unless there is something terribly wrong rotaries are no more fragile cold than virtually any other engine when cold - very few exceptions.

kraneous

That's true, but most people don't even know that they should wait for the engine to idle down (warm up) before driving...I see too many people just hop in, start the engine, and take off....just trying to protect those poor rotary engines out there from premature destruction (or rebuilds at least).

driving a little 2L 4 banger too hard when it's cold is one thing....driving a 250HP rotary beast too hard when it's cold is another ball of wax.


...or maybe I have absolutely no idea what I'm talking about!

diabolical1

iTrader: (3)

no, i get it. as a matter of fact, i used to be one of those people ... and then i went to other extreme of waiting until the car got to normal operating temp ... and now i'm back to driving after a cold start (actually, i wait anywhere from 10 to 30 seconds or so). i refrain from taking it above 4000 RPM until warm.

my point was really that the manufacturers (and not just Mazda) assume people are not "warming" the engines and thus, they are built with that assumption in the design (metals, clearances and lubrication systems). it's totally acceptable to just start and go, it's just a little better if you wait or at least take it easy until warm.

kraneous

I guess that is the big thing....just make sure that you don't push the engine before that temp needle is straight up and down. I would just be afraid of having to make some evasive maneuver that requires a little extra throttle before the engine is warmed up properly and risk damaging the engine just to avoid an accident...but on the other hand i guess a short little burst wouldn't cause too much damage.