Recentlyconverted

Ok Guys, I know I asked you all a while ago about the whole engine cool down after agressive driving, thanks for the responses. But I have a couple of more questions.

I just got a water temp and an oil temp gauge put into the car. Now what I have been doing after driving is:

Let the engine run at idle for about 5 minutes, then turn the engine off and let the fans run for about 2 minutes.

I've noticed that when I let the engine sit at idle though, the temperatures will go up significantly (about 210-220 F) for both oil and water, which makes sense. What I'm curious about though is what I shoud be using as the monitor to tell whether the car is cooled down enough, i.e. if I finish driving (pushing the car) and the engine oil temp is at 180 F, do I still let the car sit at idle for the 5 minutes and let the engine temps get to about 210 F, then let the fans run, or do I just shut the car down at 180 F?

Also, when driving aggresively, what kind of temps do the turbos go to, i.e. at oil temp of 210 F, hat is hotter when driving aggresively, the metal of the turbos or the oil. What I'm basically trying to figure out is what actually kills the turbos, the oil temp or the temp of the turbos themselves after driving hard. If it is in fact the oil temp, wouldn't letting the car sit at idle and letting the temperatures rise be worse for the car?

Any info would be great, thanks guys.

SteveF

I'm not going to give you actual numbers, but I think you just have to let your car cool down more if you have been boosting a lot. I prefer to just drive the last 2-3 minutes of my trip without hitting boost and pop the hood when I park (if it is a safe place, i.e. my garage). I don't think letting your car idle is necessary unless you for some reason boost up until your driveway/parking lot. The car cools a lot better at speed than sitting at idle anyway .

Steve

adam c

iTrader: (2)

Good advice from Steve. Drive the car easy for the last few minutes before you arrive at your destination. When you get there, turn the car off. Do not let it idle, as that only heats up the engine. I like to turn on my fans several minutes before I arrive. That way, the engine is as cool as it can get when I shut it down.

This is why a turbo timer is such a bad idea. Idleing makes the engine hotter.

1QWIK7

iTrader: (33)

^^could be true but isnt it when you boost, you raise engine temp? idling it for a minute or so before shutdown transfers as much heat as it can to bring it back to normal temp...or i could be wrong..

thats what i do, if i do boost right before arrival to somewhere, i will idle at the spot for a minute or 2, shut down and run the fans for another 2-3 minutes, then get out..

i always thought that was the way, no?

Section8

iTrader: (6)

I think that's better than just shutting the car off, but it's always better to have air moving through the radiator than to let the car idle after you've been boosting. I've got a long drive through my neighbor hood to get to my house, so I normally pop the hood as I pull into the entrace and putt at about 20-25 mph to my house (lots of kids anyway that like to run in front of you)

When I get in the garage, I shut down immediately, open the hood, and my fans run for 10 minutes by themselves. My normal shutdown temp is ~182-185F

Zer0 Cylinder

im a dummy, but i thought the idle process was to let oil get into the turbos or something like that?

1QWIK7

iTrader: (33)

^^it is

but arent our turbos coolant cooled? or half coolant/half oil?

thats why i dont understand turbo timers, they let the car idle to keep the oil moving through the turbos but what about the heat also? they should make one that allows a cool down process and run the fans to pull out as much heat..

adam c

iTrader: (2)

Fact: If the car is stopped at idle, there is no air going thru the radiator (without fans on). If there is no air going thru the radiator, it WILL NOT cool the coolant. The engine will only get hotter at idle.

Drive it easy, and shut it down right away. It's that simple!!

1QWIK7

iTrader: (33)

adam c, i agree with you 100 percent but lets say you do boost like almost right before arrival. it would only be smart to idle there for a minute right?

lets say your water temp went to 205f cause of that boosting, turning it off will be worse cause of heat soak no? at least idling it there for a while would bring it back to at least 195, then you can shut if off and heatsoak wont be so bad..

cause after boosting, if you shut it off, the temp rises like no other..

RotorJoe

Yes. The trick is to bring the turbos/exhaust down to engine temp. So you don't heat warp your turbos or boil oil/water in the turbo housing. Just don't boost a few minutes before shutdown.

Watch you engine temp and bring it down too, by running the fans on high a few minutes before shutdown. Try to shut the car down after not boosting and seeing the temp around 85c. You should be fine then.

If you are really worried. Then pop your hood durning all of this. Leave the hood popped after shutdown. Come back after five minutes and restart the car with the fans on high. Again watch you coolant/engine temp drop even more (as it has probably increase from when you first shut it down, heat soak). You should see it drop to below 80C or so. Then after it stabilizes (the temp and idle) shut it back down. Leave the hood up for as long as you want.

Or you could just do what was stated first and go easy on the car before you shut it down. After you own the car for a while you stop being so damn paranoid. I used to do all of this but now I just run the fans and do not boost a few block before I shut down. All is good.

adam c

iTrader: (2)

If you are going to do something smart, you won't be boosting right before you shut down the car

ORX705

it doesn't hurt the engine to idle down. yes the engine will begin to heat soak (such as the manifold, intercooler...). the idea of cooling the turbos down prior to shutoff is so that the heat from the turbos don't cook the oil. coking was more of a problem with some of the older oils and oil cooled turbos. at idle the there is very little coolant flow, so it is better to take your last few min of your trip easy and then perhaps idle her down for a min

RotorJoe

Ha, Ha, Ha,

But I have to race/cutt off my neighbor as he is pulling into his drive way.

DamonB

My stock turbos finally croaked at about 120,000 miles and I have a completely stock car other than downpipe, catback and suspension. I daily drive my car 10,000-15,000 miles a year in the Texas heat with a stock radiator and the a/c on to keep me cool. All I ever do is change the oil with plain old Castrol dino oil, never boost hard before 180F of coolant temp and never shutdown the car immediately after running it hard. Driving anywhere I just drive the last few blocks as a normal law abiding citizen and then shut the ignition off. Heat is not near the enemy people make it out to be, only too much heat is bad. Just use some friggen sense and don't sweat about it so much.

The only exception is during autox weekends. You go out and bang the hell out of the motor (I still make sure I have at least 180F on the temp gauge before I get to to the start) and then don't get a chance to drive the car around to cool it down; you're forced to head back to grid and park. In these cases I soak the radiator and oil coolers down with water from a garden sprayer as the car idles with the hood up. When the coolant temp gets to 200F or below I shut the car off. If it's a really hot day I will start the car very briefly after about 5 mins so the engine can pump the cool water from the radiator into the block. FYI there is practically no heat soak after shutdown if you leave the hood up.

It's not uncommon when it's 100+ degrees outside for me to exit the course showing 220F on the coolant temp gauge and then have it back down to 200 (or less) in no more than a few minutes. The temps drop quick if you have plenty of water to spray.

cletus

Zero: the turbos are lubricated with the engine oil. I have always understood the reason to let it idle is so that the turbos cool down while the oil is still circulating. I forget the numbers, but I think it is not uncommon for a turbo to hit in the neighborhood of like 1300 degrees. I know on my audi it did not take much boosting for that entire thing to turn bright red. If you shut the car off, the oil stops circulating and actually can turn into a powder at that temperature which will kill the turbos.

adam c

iTrader: (2)

A very good reason to do a fan mod. With fans running, the car won't heat up while sitting at idle.

http://www.scuderiaciriani.com/rx7/fan_mod.html

Zer0 Cylinder

why does it have to be hooked up 2 minutes? what happens if you leave it hooked up longer? what if it's on 5 mins, 10 mins?

Section8

iTrader: (6)

This is a good trick I'll have to remember. So far I haven't run had any problems with heat after an autox run, but i've only run with 1 SCCA region and one non-scca club. The SCCA region is laid back, so I can do a cool down lap after my run and grid up whenever I'm ready, and I haven't had temp problems running with the other club yet.

Recentlyconverted

wow, thanks for the info guys, lots of info here. so I guess I'll just not be a jackass and drive like a normal humn being for the last few miles, lol. thanks again.

DamonB

Useless. If the coolant is hot the fans are already running and the hood is already up as I'm parked in grid. My only goal is to get temps down quickly so the car can be cool for the next run. Running the fans after coolant temps is down is not going to cool anything off any quicker with the hood already up.

adam c

iTrader: (2)

Not useless at all. I turn on my fans before the run starts. That way the engine never gets that hot, and the fans are already cooling the engine while I am driving back to the grid. I suspect that my car reaches the grid with coolant temps at least 20 degrees cooler than your car. If cooling the car quickly is your priority, you should try it.

For non racing applications, the fan mod is even more usefull. Not many people are willing to spray their radiators if they are not at a track.

DamonB

I can already kick on the fans anytime I want: I turn on the a/c.

I cross the finish line, brake hard, turn on the a/c and pop the hood. Park in grid and raise the hood with engine idleing and spray radiator with water. Once the coolant temps are down running the fans with the engine stopped and hood up is useless.

As for what my temps are unless we're at the same course at the same time and running comparable times there is no sense in even bothering.

KevinK2

lots of good points. but if you have a sensor on the t-stat hsg, then 'apparent' heat soak after shut-dn will usually show as you get a thermal flow of hot coolant from the turbos. this will not show much on stock gage sensor or one in the TB line.

note that at idle, tubos are more likely cooled by the flowing oil, vs the stagnant coolant in tubo lines.

for leaving car in hot open parking lot, true fan-mod with 10 minute run cycle is best way to reduce temps under hood that tend to bake all the vac lines and solenoids.

adam c

iTrader: (2)

You don't run the AC during your run, so the fans are not helping to keep the car from getting hot.

Thats a good procedure. I never said anything about running the fans at a race after shutting down the engine.

Thats not a very good arguement. You can't seriously believe that my procedure won't provide lower coolant temps, when arriving at the grid, under EVERY condition.

dgeesaman

iTrader: (7)

Hmm, my girlfriend bought a $15 plastic pump sprayer for use in the barn - I'd bet that would be pretty good sprayer if filled with clean water. What do you use?

Dave