1JZ running hot on track, IC blocking radiator?

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1JZ running hot on track, IC blocking radiator?

Postby texel » Sat Feb 24, 2018 9:05 am

1993 supra with 1jz, 16psi running race gas.

Temp gauge road driving shows about 92C
Electric fans come on about 90C as best I can tell
When shift light was set at 6500 track temp would run about 98C
Changed shift light to 7000, track temp went to about 103c

Front nose cone isn't really ducted, just has a big low hole that is pretty much filled with the intercooler.

Looking at other makes of cars, they often seem to have additional air holes above that area, that would give some decent flow directly to the top part of the radiator. Next practise day I'll take the whole nose cone off and see if that cools it down a bit, as I can't keep driving it at those temps.

So the question is, will cutting a new higher air intake help in cooling, or should I be looking harder at radiator condition, thicker radiator, theromstat fully opening etc. Will post some pics





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Re: 1JZ running hot on track, IC blocking radiator?

Postby GDII » Sat Feb 24, 2018 5:24 pm

That's quite a large radiator. It seems to be semi shrouded too which will help the fans pull air through the right places however on track you are going too fast for the fans to work.

What temperature does your thermostat open?
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Re: 1JZ running hot on track, IC blocking radiator?

Postby Leon » Sat Feb 24, 2018 7:19 pm

TK test to see if you've maybe got a really slight headgasket seep that isn't showing itself in road use?
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Re: 1JZ running hot on track, IC blocking radiator?

Postby matt dunn » Sat Feb 24, 2018 8:18 pm

texel wrote:Temp gauge road driving shows about 92C
Electric fans come on about 90C as best I can tell


The radiator fans should not need to be on under normal road driving,
as the airflow should be enough to keep it cool.
Fans should only be needed when stationary or going slow,
at speed fans are a resistance to airflow even when running.

How accurate are those temps measured?
What is the thermostat temperature?
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Re: 1JZ running hot on track, IC blocking radiator?

Postby 85AW20v » Sat Feb 24, 2018 8:57 pm

Can all the hot air get out from under the bonnet area easily? Years ago the 4WD Escort rally cars had cooling problems. Opening up the front to get more air in didn't solve it but a couple of vents on the bonnet did.

Could also be that not enough air can get through the radiator with the way the fan mountings are. Take one out the next time you're at the track and see what happens, because as Matt said, they're just a restriction at speed.
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Re: 1JZ running hot on track, IC blocking radiator?

Postby texel » Mon Feb 26, 2018 11:17 am

Bonnet is pretty well vented, see pic so don't think there would be a pressure building up behind the radiator.

Temp is displayed on a electric gauge with sender in the top hose, can't say its exact, but the 103 temp certainly smells hot, and blew a heater hose off, so probably about right.

Thermostat, don't know the details on it, assume factory, if it was a bit easier to get out, I would give it a good boil up and see what happens.

TK test, don't even want to think about that, but can't be dismissed.

Pic show the nose off, its hard to believe the radiatator is getting a fair suck of the sav, with the IC where it is, I can drop it probably 100mm if I had to, or just put a tube in its place to see if the cooling improves.

Car was a drift car, which I think went okay doing that, but probably not set up so well for circuit work at high revs for longer

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Re: 1JZ running hot on track, IC blocking radiator?

Postby mlracing » Mon Feb 26, 2018 12:29 pm

Probably worth testing with the pipe and see if the cooling improves. Heaps of ducting and decent fans pulling air out does make a difference too. How about radiator cap? I used to run civic on track and sometimes it would get over 110 but never blew any hoses off.
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Re: 1JZ running hot on track, IC blocking radiator?

Postby Mr Ree » Tue Feb 27, 2018 10:47 pm

Do you have your under-body shrouds in place? They are fairly crucial for keeping temps down.

Also, the factory clutch fan and shroud is far less restrictive than the electric set up you have. Any chance of putting back on the factory bits and doing a comparison?

There are plenty of A80's running around on track without the need to go cutting holes in the front bumper, so I wouldnt get that drastic yet, especially at the power level you will be at.

Definitely check your thermostat and radiator cap, and if possible, do a TK check too.

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Re: 1JZ running hot on track, IC blocking radiator?

Postby texel » Wed Feb 28, 2018 7:28 pm

Under body and radiator shrouds are long gone.

Took it for a 12km road run with the nose on and got temps of 85-86C, then did the same with the nose off and got 81-82C, 100kph and no boost to speak of. Themostat etc seem to be working fine.

Next step is to do the same on the track at WOT and full boost and see what happens

I still think the IC blocking the rad, and no direct flow of air onto the radiator is a oversight, plently of other cars had an IC hole and a separate one for the top of the rad, like R32 for example. Even a 4wd with a high mount winch in front of the rad can give heating issues.

Pic below of a supra in japan with a rad cut in the nose, makes sense to me, but I'll do a bit more experimenting to see. Cheers


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Re: 1JZ running hot on track, IC blocking radiator?

Postby mlracing » Thu Mar 01, 2018 12:42 pm

Could look at a v-mount system if you want to get carried away
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Re: 1JZ running hot on track, IC blocking radiator?

Postby MAGN1T » Thu Mar 01, 2018 8:48 pm

FMICs always make cars overheat on the track.

Instead of plenty of cold air getting to the radiator, you have a restricted supply of warm air trying to cool the radiator.
Failed mods.


Not only that but aftermarket aluminium radiators are less efficient than the original factory radiators.
More failed mods.


But it looks pretty.


TK tests don't work.
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Re: 1JZ running hot on track, IC blocking radiator?

Postby KinLoud » Tue Mar 06, 2018 8:32 pm

Air will try to go around an obstruction rather than through it
Block up any tiny gap to make sure all the air can only go through the radiator.
Seal between the edges of the inter cooler and the radiator - so any air that has gone through the intercooler cannot escape and go around the radiator.

Airflow through the radiator depends on pressure difference - think about adding a stiff flexible air dam directly below the radiator to increase the pressure difference in front and behind the radiator.

What mix of coolant do you use?
Pure water has the greatest heat transfer
Try using lower amounts of anti freeze - just enough to prevent corrosion - I'm sure it wont be anywhere that you'll need to worry about coolant freezing overnight
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Re: 1JZ running hot on track, IC blocking radiator?

Postby BlakeNZ » Wed Mar 07, 2018 9:50 pm

that temp sensor that is in the top radiator hose, can you loosen the clamps , and rotate it back so that it cant possibly sit in an air bubble at the top of the pipe?
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