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I am going over everything i have ever heard or read to make sure i know how to properly take care of a turbo so that i will lessen the chance of having to spend mega $$$$$$ getting a new turbo again. I am having a custom one built now and of course want to take care of it.

So when I had the t618z greddy kit turbo in, I would set the tt to about three to five minutes. I noticed that usually on a typical day my oil temps cruising were around 180 degrees (f) but after idling for a couple of minutes the oil temp would increase. It was in the summer but sometimes it got as hot as 210 (F). So if I am idling the engine to let the turbo cool but the oil is heating up, is the turbo really cooling down? I guess in my mind that the turbo is so hot that the rise in oil temp still allow the turbo to cool but I wanted to make sure. Is that right?

Also I have heard everything from idling the engine 1 minute to as much as six minutes. Typically speaking, normal driving, how long is enough?

One last question, in the mornings, how long should I let a turbo 8 warm up before driving?

Thanks guys, I can not wait to get back on the road!

Chris

PUR NRG

Here's my uneducated two bits of deductive logic:
Idling will raise water/oil temps since there is no air flowing through the radiator and engine bay to cool things off. Since the turbo is bathed in hot exhaust gasses it is much hotter than the engine immediately after a drive. So you try to idle long enough to cool the turbo but not so long you increase engine bay temps to the point where you're heating the turbo up again.

Like you I was concerned about turbo heat. What I did was get a greddy oil pan to increase the total amount of heat sink (oil) available to me. I also coated that oil pan in a thermal dispersant to shed even more heat than you get out of the two oil coolers up front. (I also coated the intercooler with thermal dispersant but I don't know how much that affects oil temps.) The net result is when using 5W20 RP synthetic my oil temp is consistently 40-50 degrees cooler than my radiator temp during daily driving. Sometimes I wonder if my oil temps are too cool but it does mean I'm cooling the turbo that much more during pre-shutdown idle.

For daily driving I have the turbo timer set for 30 seconds. Naturally at track events you'd be coasting around the paddock for several minutes to bring temps down.

During startup I keep RPMs below 3k until the water temp reaches normal operating range, which for me is around 190F. Letting the engine alone warm up doesn't do jack for the tranny, diff or other lubricants that need to get up to range as well.
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bald ***** Webcams

zoomzoom_8

The heat sink that you put on the greddy oil pan, where did you get it, I think I may go ahead and do this while I wait for my turbo to come back. Did you have to remove the oil pan to do it?

Speaking of heat, what else did you do in heatshields in the turbo area? All my heat shield has fell off so that can be done while I wait too. I want to stay away from a turbo wrap though.

So in your opinion as long as i let it idle for 30 seconds to a minute after a normal drive where boost has occurred i should be okay? Is there any real safety in the turbo timers that monitor rpms and then calculate how long to idle or are they inaccurate on the rotary?

So on the warmup, you let the water temps warm first then drive below 3000 rpm for a while? Is that what you are saying?

Thanks for the help

Chris

rotarygod

The key to letting the engine idle after driving it with a turbo timer to cool the oil temps down is only important after very hard driving where you have really heated the turbo up. There are times when you will see the turbo glow orange after hard use. You need to allow oil to keep flowing through here to get the turbo, not the oil's temps down. This is because there will always be a small amount of oil left in the turbo after you turn the car off. This small amount will "coke" in the turbo, turning into a sludge. This is bad. You need to let the turbo cool off enough that this won't happen. For easy daily driving where oil temps don't get too hot, you don't need to worry about this. This is also why many factory turbos use water for cooling and only oil for lubrication. The water coos the turbo down faster than oil cooling.

When you are moving slow or are at idle, there is no air flowing through the oil coolers. This in my opinion is a design flaw. When you are moving, there is airflow and heat is removed. That explains that. If your highest oil temperatures are only at idle, don't worry about letting the car run for a while before you turn it off. It's not hot enough. Only do this after a hard or semi-hard drive.

T-von

But you and I both know that it's always better to drive the car lightly before shut down since this keeps the air flow going through the radiator and coolers. Since rotarys are thermally inefficient, I never let mine idle for too long since more carbon deposits will form due to the engines inability to properly burn the fuel air mixture (especially at low rpm's).

pcimino

I remember JC Whitney used to sell an oil resevoir that would fill when the oil pump was running, and when the engine would shut off it would drip oil through the turbo bearings. This was supposed to avoid the need to idle.

I have no idea if it was junk or even worth bothering, but was interesting. I wonder if you could put in an electric oil pump that turns on when the engine is off and pushes the oil around for a few minutes?

PUR NRG

It's not a heat sink per se. It's a coating you put on the oil pan that helps it disperse heat better.

I coated the exhaust side of the turbo housing with a thermal barrier, in addition to the normal greddy heat shielding. Swain Tech did both barrier and dispersant.

I used an HKS TT which has an RPM lead, but don't know how to hook that up so it can read the RX-8. In theory it's better.

No, I start the car and immediately drive, keeping it under 3k RPM until the water temps reach 190F. Living in CA I don't have to worry about freezing weather.
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Lovely Wendie99

yiksing

I totally agree with driving around to cool off the car after spirited driving, helps your brakes as well. Other than that you are gonna have to upgrade radiator, intercooler or extra oil cooler if you are paranoid. As long as you keep oil flowing its good, try better coolant mixture also.

PUR NRG

How does upgrading the radiator or intercooler help cool down the turbo? And by extra oil cooler, you're suggesting the addition of a third cooler to supplant the two already in the car?
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SexyStephanie18

yiksing

Anything associated with heat if upgraded will always be good for a force induction car since heat is the main culprit for wear in a car. Helping the car lose heat through radiator and oil cooler subsquently lets the turbo and other engine parts operate at lower temperature since engine oil is moving heat away from engine parts and eventually to the air. My RX-8 only came with one oil cooler so I guess yours is enough.

PUR NRG

Agreed but that's not what I asked you.

The radiator is filled with water which cools a different part of the engine than the oil does. I don't think heat transfer from one part of the engine to another is that big an issue, as evidenced by my 50F temp differential in the two fluids. Plus the engine needs a minimum operating temp so if it's too cold it will shut off the radiator flow. Color me still skeptical about how a bigger radiator helps cool the turbo.
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Zx14 vs hayabusa

MadDog

I added a third oil cooler because cooler oil = cooler turbo.

Plus, I wanted to combat the heat the turbo dumps in the oil to combat oil breakdown.

PUR NRG

What were your oil temps before and after the third oil cooler?
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CYBERVIRGIN

rkostolni

What kind of thermal barrier did you install on the turbine side of the turbo?

PUR NRG

Go to Swain Tech's website and read up.
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NEXIUM SETTLEMENT

yiksing

Oil flow through turbo and draws heat away from turbo, so cooler oil will have a higher capacity to draw heat away from turbo. Radiator coolant gets heat away from engine oil to air although not as direct as oil cooler do, that's how new cars with automatic transmission cool the ATF fluid through the radiator although still inadequate. The better your car can dissipate heat, the better it is for ANY PARTS of your car. Plus as your car's power increase, the more energy it will lose as heat energy so being able to dissipate sufficient heat plays a role in increasing horsepower.

PUR NRG

Once again I am asking you how that's supposed to work. You are simply restating your opinion without any theory to back that opinion up.
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Alteha19

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i think what he is saying is that if the engine itself is cooler then the oil will be cooler

PUR NRG

And what I said earlier is the part of the engine cooled by water is different from the part cooled by oil, as evidenced by my 50F temp differential. That differential leads me to believe increasing water cooling capacity will have minimal (if any) impact on oil temps.

Also consider this: the engine needs a certian operating temp to function properly. If you are not in an overheating situation then blindly increasing water cooling capacity will have no effect as the engine will regulate its temp to stay in that operating range.
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BUY MARIJUANA SEEDS

zoomzoom_8

thats true and I have read that optimal oil temps are around 180 f for power, no eveidence to back that up though

yiksing

Go get yourself a book and read how a radiator works and what engine oil actually does (cooling the engine, not just lubricating). I ain't gonna spend my time proving a point to you, take it or leave it.

PUR NRG

You know, that's nice when you're talking about pistons, valves and lifters. None of which a rotary engine has.

Here is the sum of my rotary cooled knowledge: the aluminum rotor housing is cooled by the radiator. The eccentric shaft bearing is lubricated and cooled by oil. This supports my theory that the part of the engine cooled by water (the outside of the housing) has little if any effect on temperatures for the center part cooled by oil.

PS. Your last sentence makes you sound like a blowhard who doesn't know what they're talking about and doesn't want to admit it. I've made a couple different observations with fact and inductive logic to support my claims. You've said nothing to refute that logic and simply repeat the same claim without any supporting facts. The reason I asked you those questions is because if you know more about rotary engine cooling I'd like to learn. That is, in large part, what this forum is for: the exchange of knowledge. Unfortunately it sounds like you're just repeating the ricer mantra "bigger is always better" without any thought or explanation as to why. That's dissapointing.
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FERRARI/MASERATI ENGINE HISTORY

rotarygod

Actually each system does have an effect on the other. Yes the rotors themselves are cooled by oil and the housings by water. However the heat has to go somewhere. If the oil or cooling system has a problem, more heat is transferred to the combustion chamber which transfers more heat to the other cooling system as well as out the exhaust. When oil temps go up, so do coolant temps and vice versa. This is definitely noticable. If the oil temps get out of hand, coolant temps can rise. If the coolant temps get out of hand, oil temps can rise. Happens all the time. You need to treat rotary oil and coolant systems as 2 independent systems that are of a symbiotic relationship that need each other to work properly. This does not mean they will both be at the same temperature as each other though.

rotarygod

On a rotary, 1/3 of the engine cooling ability is through the oil and the other 2/3 is through the coolant. This is very different from a piston engine as oil is not typically a cooling medium. It is for this very reason that small rotaries will sometimes need more oil cooling than 1000+ hp piston engines.

yiksing

Call me a blowhard or whatever you want, only 4 words for you

"THINK OUTSIDE THE BOX"