How do you Cool down your engine.
 

Hello,

I really get into the little processes and details of operating my 8. I live in the back of a larger neighborhood with a 30 mph limit. I love this because it gives my care a very easy rolling warm-up before I get to the main road. It also gives me a chance to let thing settel down and cool off a bit on the way back through to my house. Generally I run in 2nd at about 3400 rpm on the way in but I have run in 3rd at 3000. On really warm days sometimes I pop the hood and or with the windown down turn the air fent to warm to help take some of the heat out of the coolant.

Here's the question: what is thought to creat less heat; 2nd gear at 3400 (more coolant and oil flow) or 3rd at 3000 (less heat generation combustion cycles)?

Also, what do you think about the hot vent air and poping the hood?

Thanks,

CWB

i dont know which is better for cooling, but id say popping the hood is a bad idea while moving, its made of light and relatively weak aluminum, even at those slower speeds it can warp and bend by virtue of air pockets.

Haha, that's funny. I think he meant after he got to his destination that he pops the hood.

I don't know for sure. When I bought mine, the sales person told me to let the engine idle for about a minute when you get to your destination before you shut off the engine to help cool it off. Don't know if that is true. They say that for some turbo cars.

My sales lady said the same thing as Jeffjett. I was pretty good about it at first. But now, I just shut her off when the idle settles down. I think this is more an excersise in preventing flooding than it is cooling though.

Re: How do you Cool down your engine.
 

I'd vote to lower rpms - less frictional heat, less combustion heat. The cooling system is designed to adequately cool the engine (water flow, etc.) at idle, so lower revs will generate less heat.

Lower RPM will result in less heat generation. Running lower RPM will not necessarily result in a lower temp. after shutdown. The metal in engines stores a lot of heat. It takes about 1-3 min. to get it transmitted to the coolant (think of it as a heat pulse - the pulse takes that long to travel through the metal and into the coolant). So if you ran at a lower RPM for a minute, you'd still have up to 2 min. of higher energy going into the coolant after you shut down.

All that being said, the only time you really have to worry about it in a NA engine is when you are driving fast (freeway for example) or under high load (drag racing, or climbing a steep hill such as a mountain pass, for example). Then it's a good idea to drive slowly or just let it idle for a few minutes to get the high energy heat pulse out of the engine (the coolant will flow sufficiently at idle and the fan will transfer the heat to the air). Oh, and the oft repeated axiom "run turbo cars slowly to cool down the turbo so the oil doesn't coke" is a myth on modern cars. We now have coolant in the turbos, and it goes a long way to limiting the max. heat the oil in the turbos will see. It's still a good idea to cool down any car after hard use.

A few anicdotes -
Check out your downpipe right after you come off the freeway at night - it will probably be glowing. This doen't get transferred to the coolant, but is a good reality check.

Check out cars at freeway rest stops. If they come charging in and stop and turn off the engine you will see some of those cars loose some coolant.

At freeway speeds you are using only about 30-50 HP, so imagine how much heat is generated when you use the full 180 HP your engine produces at the rear wheels!

I learned not to take any TECHINCAL rotary advice from auto SALES persons unless they own their own rotary powered car.

Most of it has been incorrect.

The only time I have ever worried about the car cooling down was after a 25 minute session on the track. And I was more concerned with my brakes than the engine.

put bags of ice under the hood

Why would you do any of this??? Not in the owners manual... So why??

I agree, unless you have done any serious mods to your engine's breathing or cooling systems, following the owner's manual should be fine... just stop the car, let it come to an idle, and shut it off... Of course this is different if you are racing your car, as the manual is not written for that, but for daily driving, I wouldn't over think it, things like the cooling of the enging are designed over-conservative, especially in a daily driving engine that can handle the race track.

agree not necessary

Nothing special is required. You're likely going to do more damage by putting some thought into it.

In my 3 weeks and over 2000 miles of rotary ownership experience, the only part of the car that seems to require special attention is the oil. It needs to be checked much more frequently than a modern otto-cycle engine.

i dont get it

i thought you're NOT supposed to shut off engine when it's cold - doesnt that cause flooding?

arent u actually supposed to rev to 3k rpm before you shut down so the engine heats up to let all the gas evaporate?

Cold, as in room temperature. After driving for a few minutes, it heats up to its operating temperature, which is probably a few hundred degrees (anyone know the operating range?). I think I heard between 400 and 1900 Farenheit (normal driving vs. racing). Letting it idle just brings that value down closer to the lower end before you shut down (cooling, etc. all turn off). Also, I was under the impression that revving the engine before you turn it off was to suck the excess gas out of the intake, thereby lessening the amount of spark-plug-fouling raw fuel that gets injected when you start up the next time.

In my MR2 I needed to let the engine come back up to temp if I had been hard on the turbo. The problem with a turbo car is that you don't want the engine cooling down too fast. That is real hard on turbos. You can solve this by running the engine for about 1-3 minutes before shutting down or you can buy and install a good turbo timer. I will jump on the bandwagon and say that I don't see a point in trying to cool down the RX-8. Mine does just fine without. I do rev the engine to 4-5k before shutting down (just a flooding scare reflex).

This thread is insane....the only time you need to cool things down is after hot laps at a performance driving school or track day.....at the end of a session you do a slow lap to let things cool off before parking your car. For normal everyday driving, there IS NO COOL DOWN PERIOD. Don't be so gullible. RTFM.