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chickenstomp
01-24-2011, 05:14 PM
I know you are supposed to let a turbo cool down for a bit before turning off the engine, but what is the protocol for something like a gas-stop? Is it ok to turn off the car without cooling down if it will only be off for a minute or two?

Luni
01-24-2011, 05:27 PM
Youll find all sorts of conflicting opinions on this.

Heres my take on it...

Back in the 90s our oil technology wasnt as good as it is now. So theres one thing to consider. The manual says to let the engine idle for ~45 - 60 seconds after using it to cool it down so the turbo doesnt coke and clog the oil lines.

If you are running synthetic, youre most likely not going to experience the coking effect as the oil wont break down like the dino oils of the 90s. Even if youre running a decent modern dino oil, youre not likely to coke.

If you decide youre going to boost right before you get to the gas station, yeah, you should probably let it idle for 15-20 seconds before shutting it off. As a general rule of thumb, I dont even use my turbo timer. If I boost hard before stopping I just let it idle a bit with myself in the car before turning it off. Most of the time I "turbo time" the car by just driving it nicely the last 1 minute or more before I get to where Im going, so when I get there, I can just turn it off and be fine.

So my take on it is, you shouldnt need to cool it down unless you do a hard boosted run up to the gas station. I wouldnt shut my car off right after doing a hard boosted run. Whether or not it really does coke, in my mind thats just asking for trouble.

UtahSleeper
01-24-2011, 06:14 PM
To me it makes sense just to wait the 45 sec. Nothing is ever so important that you can't wait for a few :) Thats how I did it when I had a running trac.

Facime
01-24-2011, 06:25 PM
I agree with Luni, better chemicals make for different conditions. I followed the same protocol for shutdown, Longer delay immediately after a boosted run, and almost no delay if I idled in traffic or crawled into a parking lot before stopping.

chickenstomp
01-24-2011, 06:53 PM
What I mean is do you have to let it cool down if your going to start it right back up again in a minute or two

Facime
01-24-2011, 07:03 PM
I think the point is, that if you dont have to delay shut down in the first place then its not a problem. If you feel you are in a delayed shutdown situation...you just boosted your ass off to come screaming into a gas station for a nascar style splash and go...then IMHO 1 or 2 minutes of extreme heat soak is enough to potetially cause a problem. It really is those first couple of minutes after shutdown where your temps go up you are trying to avoid in the first place.

I wouldnt do it to my turbo.

Mafix
01-24-2011, 08:38 PM
water cooled turbo = no worries
non water jacketed turbo = get a timer

Blackcloud
01-27-2011, 05:22 AM
water cooled turbo = no worries
non water jacketed turbo = get a timer

I agree. I relate it to trying to sweat a pipe when its still got water in it ( soldering a copper pipe) you cant do it when there is liquid in the pipe, the heat is sucked away by the liquid.. the same will happen in your turbo


Ive seen 1900+deg egts on my truck in a WOT run. usually by the time i get slowed down, and stopped truck in park and ready to get out my egts are back down to around 350* which is a normal idle temp. which im ok with shutting down at.

so like everybody else says.. just come to a stop.. give your self 30 seconds to get your shit together before you get out and you will be fine.

temperacerguy
01-27-2011, 07:48 AM
water cooled turbo = no worries
non water jacketed turbo = get a timer

I disagree.

I've had numerous CT-26s, and even a brand-new Toyota installed CT-26 only lasted 40K miles on my MR2 without a Turbo timer. (the CT-26 is a water jacketed Turbo). This turbo NEVER saw any Dino oil, only Mobile 1 and Redline. It's not the EGTs that cause the oil to coke, it's the HUGE MASS OF IRON in the center cartridge that heat soaks. The purpose of idling the car is not to let the EGTs normalize, it's to let the oil and coolant pull the heat away from the iron in the center cartridge so that when the oil stops flowing, the hot iron doesn't coke the now sitting oil.

Mafix
01-27-2011, 03:44 PM
the shall i state anyone using a real turbo. not a 20 year old designed ct series hot air blower.

T-spoon
01-27-2011, 04:02 PM
Kind of an interesting thing to note regarding this topic: On all my previous turbo cars I'd let the timer go a full 1 to 2 minutes and everything seemed dandy, but on the 88 alltrac I discovered that it seems to be so bad at evacuating heat from the engine bay that it makes me wonder if it's not SIGNIFICANTLY hotter under the hood sitting there idling than driving along at 35 MPH. I have the TT set on 30 seconds on it now, enough time to let things circulate a bit, but hopefully not adding as much heat under the hood. I never got around to it but I'd be interested to know if anyone else has taken some temperatures on the stock st165 setup vs the stock st185 (since it has hood ventilation, a scoop and what appears to be better bumper cover air flow) to see whether what I'm talking about is an issue. I do know that I've had the 165 reluctant to start once or twice in the summer after running for a while with a short stop (15-20min). Popping the hood seemed to let out a lot of heat and started pretty quickly after that.

Mafix
01-27-2011, 06:31 PM
165s get stupid hot under the hood. have you removed the rear gasket? that helps some.

T-spoon
01-27-2011, 07:58 PM
165s get stupid hot under the hood. have you removed the rear gasket? that helps some.

I haven't, but that's an idea, I had thought about stacking a couple washers to prop the rear of the hood up too, tacky as that would probably look. Maybe the best option is to grab a cheap GT/GTS/ST hood from a junkyard and practice cutting it up for ventilation (if I were keeping the car).

In any event, sorry for the minor thread jack, though it is somewhat related. Fully on topic, I personally treat short stops the same as I would treat a long one. Timer goes for 30 seconds, which is usually just about the right amount of time for me to get the pump ready with my bank card and everything. Regardless of your opinion on length of cooldown, I don't see why a short stop would be any better than a long one, the only thing effecting your cooldown was mentioned already, which is how hard you were driving it just before stopping.

temperacerguy
01-27-2011, 11:08 PM
the shall i state anyone using a real turbo. not a 20 year old designed ct series hot air blower.

I agree with you 100% here, however the majority of turbo owners of this car, are still running that CT hair-dryer.

joe's gt
01-28-2011, 06:15 AM
Run your hard car hard, let it sit. Long stints at high rpm, let it sit. Normal driving, don't worry about it.

Cavanagh
01-28-2011, 05:19 PM
Most of the time I "turbo time" the car by just driving it nicely the last 1 minute or more before I get to where Im going, so when I get there, I can just turn it off and be fine.

This, my buddy does this with his boosted car, and I even do it and I'm N/A! Just being safe I guess.

chickenstomp
01-28-2011, 05:26 PM
I agree with you 100% here, however the majority of turbo owners of this car, are still running that CT hair-dryer.

I don't see how my turbo is a "CT hair-dryer" when it's putting down 300-400 hp. (Not dynoed as far as I know)

Luni
01-28-2011, 06:06 PM
Youre not making that kind of power on a CT26 turbo dude.

chickenstomp
01-28-2011, 07:02 PM
Youre not making that kind of power on a CT26 turbo dude.

I wouldnt be so sure, it can burn rubber in 4th gear

Siyx
01-28-2011, 10:02 PM
I run a CT-26 hairdryer in my car and i'm putting down 241hp :)
My TT is set to 2 minutes regardless.
My Supra runs a CT-26 hairdryer and it puts down 358hp ...

chickenstomp
01-28-2011, 10:28 PM
I run a CT-26 hairdryer in my car and i'm putting down 241hp :)
My TT is set to 2 minutes regardless.
My Supra runs a CT-26 hairdryer and it puts down 358hp ...

Is your Celica 3s-gte swapped?

joe's gt
01-29-2011, 03:47 AM
I don't see how my turbo is a "CT hair-dryer" when it's putting down 300-400 hp. (Not dynoed as far as I know)

Dude, those turbos are massive, I think you could possibly be in the 500-600 hp range!!!

Grot
01-29-2011, 04:57 AM
Is your Celica 3s-gte swapped?

He has the OEM engine still

































But he does drive a 'Trac

KoreanJoey
01-29-2011, 05:24 AM
I wouldnt be so sure, it can burn rubber in 4th gear

You need better tires...

chickenstomp
01-31-2011, 05:15 PM
You need better tires...

Hey, just because I'm doing it on ice doesn't mean that I need better tires lol

Siyx
01-31-2011, 08:49 PM
JDM GT-Four all original :D
3S-GTE with the twin entry CT26 turbo equipped with the "hidden" 20% air bypass cheat.
(dunno what I'm talking about?? do some research to find out about Toyota and their rally car setups and how they got nixed from rally) :)
(complicated story made short, but you will get the idea.)

temperacerguy
01-31-2011, 10:02 PM
Um... The 25% bypass cheat didn't increase the capacity of the turbo, it just let air past the restrictor (which lowered the performance of the turbo further than designed)


The FIA estimates that 25 per cent more air was allowed into the engine than permitted although admits it's difficult to estimate how much more power that would achieve. An expert put it as high as an extra 50 bhp�a considerable advantage when the cars are supposedly limited to 300 BHP.

Luni
01-31-2011, 10:23 PM
I always thought the "25 percen bypass cheat" was just them hollowing out the inside of the TVSV to allow it to bleed more air which in turn increased boost...

temperacerguy
01-31-2011, 10:41 PM
No, it was ingenious. It was a device that actually pushed the restrictor out of the turbo when the clamp was tightened on the turbo. It was probably the most engineered component in the entire engine. When the hose and clamp were connected to the turbo inlet and tightened , the restrictor was pushed out of the compressor housing from 50 to 55mm, this created a 5mm gap around the restrictor plate. The additional distance from the compressor blades, in addition to the air that could bypass the restrictor itself created the additional power.

When the inlet pipe was removed, a strong spring pulled the restrictor back into the compressor housing so hard, and so precise that it looked pressed into place.

To remove the device and restrictor, you had to use a special tool made for this. Without this tool, you couldn't remove the device and everything was hidden and looked "stock"

TTE, and all team members of TTE (other than the drivers) were banned from numerous rally championships (not just WRC), for 1 year because of this. The ST205 was a horrid chassis for rallying that TTE was forced to use by Toyota to retain the factory backing, and TTE was despirate to make the car competitive against the better balanced Evo's and STi's

Here, I found a pic of the illegal restrictor...

http://carphotos.cardomain.com/ride_images/3/2572/1681/31428340145_large.jpg

temperacerguy
01-31-2011, 11:40 PM
Here's more quotes about it:



It was discovered that these irregularities were made possible by a flange which had a special hidden bypass device which was held open against a very strong spring. The hose which connected the restrictor to the turbo had a metal casing inside, and attached to this casing were catches which could secretly force open the by-pass flange to the extent of 5 mm.

Max Mosley explained: "When the system was dismantled, the flange would automatically close itself and remove evidence that extra air could have entered engine. This system not only allowed extra air which did not pass through the restrictor to enter the engine, but also the restrictor itself could illegally be moved further from the turbo.

"The hose was fixed to the restrictor by a jubilee clip. A special tool was then applied to open the device and then the device then gripped in the open position by a second clip. Both of these clips had to be undone for a scrutineer to check the restrictor and in the process of opening those clips the device snapped shut.

"Inside it was beautifully made. The springs inside the hose had been polished and machined so not to impede the air which passed through. To force the springs open without the special tool would require substantial force. It is the most sophisticated and ingenious device either I or the FIA's technical experts have seen for a long-time. It was so well made that there was no gap apparent to suggest there was any means of opening it."

Cavanagh
02-01-2011, 01:34 AM
Good info Temper!

Blackcloud
02-01-2011, 03:21 AM
I wonder what my stock turbo can do

I know they can take about 42lbs of boost.. and a buddys truck is sitting at 550hp on the stocker.

temperacerguy
02-01-2011, 03:38 AM
What's your turbo? a compressor map can show you pretty easily

Blackcloud
02-01-2011, 04:26 AM
its a Garrett gt3788va. variable geometry turbo