Quote:

Originally Posted by Mahjik

This most common automotive failure mode has been eliminated with water-cooled center sections.

I may be reading way too much into this....

So what's the difference in housing temps between water cooled and not? When you shut off your car, your water pump isn't pumping anymore either, obviously. I still see the same issue happening, albeit to a lesser extent.



True, but the water and oil temps are the same if not very similar. The center housing isn't getting any hotter from being used in a rotary application than would a piston one. Unless you are getting far more heat conducted through the manifold, I don't think that the differences there are a concern.

 

The whole point of turbo timers is to allow the turbos to cool enough to eliminate oil coking. Water cooled turbos eliminate the oil coking problem making the intended "purpose" of turbo timers useless on those types of turbos.

Now, there can be OTHER uses for turbo times that people like (i.e. running the car while opening the garage door or other things), but that was not the original intent for them.

 

I might be wrong, but I do think the center housing does get hotter because it's a Rotary. It's getting heat from the exh manifold, turbine and exh. Everything is hotter, that's why we need better mufflers.

 

When you shut off the car the water doesnt drain away either. There is still a small amount of circulation from convection inside your cooling system even after shut down that will keep the turbos cooler than draining away the cooling oil does.

I run synthetic oil in my water cooled turbos. While I typically dont just shut it down immediately after a hard pull I do shut it down within about a minute of a hard run with no worry.
One thing to remember is that any driving after a hard acceleration pull is going to help cool things off. Unless you make a 1/4 mile run and shut off your key while coasting through the light you are going to have a good minute of cool down time before you can get anywhere to stop. If the TT were so important even in water cooled turbos I would think that some of the higher end cars like a 911 Turbo would have included that $100 piece of junk in them from the factory by now.

 

I see no reason to ever shut the car down immediately after driving the car hard. Ever.

One thing to consider is the fact that while your car is sitting there idling, the turbos may be getting slightly cooler but the REST of the car is getting heat-soaked by running while sitting still. People have also lost engines because the car overheated while their TT was running.

I don't know about you guys but if I want to warm my car up for a few minutes while I do something else, I just turn it on and lock the doors. As for shutting down after hard driving, I repeat what I said above -- I cannot imagine any kind of reasonable situation where you would ever shut the car off immediately after running it hard. What, are you powersliding into your driveway after WOT the car through 2nd gear pulling up to your house?

 

That's true. I'm only playing devil's advocate. I have one myself and I typically just do it for 30 seconds or so anyway.

 

I have run my car hard and then had to shut it off.. I never worried about it. I tend to take it easy down my little side street though, just because there's kids everywhere. I think I had my turbo timer set to 30 seconds in my old car (i got it for free - so i said why not and installed it) but I found it much more usefull for leaving the car running while I ran inside a store or something like that. Also the Apexi TT had an a/f gauge built in. Mind you it was so horribly innacurate that it was useless, it still looked cool :P.

 

Do you live on the side of the interstate? The last couple of minutes of most peoples drives home or where they are going the car stays below 2500 rpms unless you drift thru subdivisions and parking lots filled with people

Edit: After rereading the thread I realize rynberg has already made this point.

 

Turbo timers might not be practical for many of you but it's doing what it's designed for (That's my point). Many say that you don't not need to cool down at all because it's water cooled, that's why I posed the question, Do you shut down right after pushing it hard. i.e drag racing.

Some say that you don't need it because you don't go beyond 2500 rpm when getting close to home. But what if I lived off the interstate? Will I need a TT then?

Do you see my point? I'm just saying that TT is not useless and it works.

 

Would you have shut it off immediately after driving hard?

 

Yes, we see your point. Turbo timers peform their duty perfectly: they run the car unattended for a few minutes and then let it shut off.


The thing most people are trying to say to you is that 90% of us don't need to run the car unattended for a few minutes and then shut if off. To those 90% of people, it's extra weight and complexity that you're paying too much money for.




Can you just drop it already?

-s-

 

Sure, I just wanted to illustrate that TT is not totally useless and even though you don't need one others would. It does it function and it works! For me, I totally need it.

 

Nobody lives off an interstate. Interstates go to exit ramps which go to surface streets which go to driveways. I have never seen a driveway abutting an interstate or an offramp.

This is a ridiculous argument.

 

It was designed to prevent coking. It's not doing that so you're statement is false. Here's the graph from the site you posted...

 

I also said that rotarys run hotter so we might be above 1.0.

 

so how much hotter do rotaries run that you think we might be above "1.0"?

 

How hot do you think the turbo on a 7 is getting?

My turbos are watercooled, yet still seems pretty hot. They should be way cooler than the ones on the 7, since I have a piston engine , and the turbo is not very enclosed.

Here's one of them, wrapped in a turbo blanket rated for 1800 degrees F continuous use:



Here it is after just 970 miles:



The insulation inside has completely disintegrated, and the reflective shell almost completely fried off.

Perhaps hot enough to coke the oil?

 

If you wrap the turbo, then you are "completely" relying on the oil and water to cool it (no ambient or moving air). You are basically trying to cool a closed oven running anti-freeze into it. I'm sure it helps keep the surrounding area cool but I can't imagine that being all that good for the turbo in the long run.



web777,

As far as the stock twins, there have been no cases of oil coking on the stock twins since I've been a member on this forum. While I'm not on the "Big List", I'm pretty sure it's safe to say that non-TT users on stock twins most likely haven't had the problem either.

Ok, so we can remove the oil coking problem; what else does the turbo timer do? The turbos are going to cool with or without the turbo timer once the car is off, so what other benefits does it offer (keeping in mind there is no oil coking problem)?

 

Is it safe to say that I can safely shut off my car right after a drag race?

 

Sure, if you want. What are you expecting to happen if you did?

 

Personally, I wouldn't for other reasons than turbo concerns.

But again, WHY WOULD YOU DO SUCH A THING? You keep bringing up these hypothetical situations. I have yet to hear a single legitimate cause for boosting the car hard and then immediately shutting it off.

 

Oil coking

I'm still not convinced that the coolant will not be able to cool down the turbo quick enough. To each his own.

 

For one thing Drag Racing, going to a rest stop of a highway...etc. But this was not my point. I wanted to illustrate those that take easy before shutting down or idling before shutting off can also benefit from TT's. But if you guys are saying no oil coking will happen then we could agree to disgree.

 

the owners manual mentions letting the car idle for 30 seconds to cool down the turbos

 

Good point!