1JZ Thermostat modification for cooling

[toy4speed]

Hi guys, I'm just doing some brainstorming on how to keep my autox Supra (mk2 with a 1jz, single turbo) a bit cooler for the 60 sec autox runs. Currently with a stock
1JZ thermostat, and around town normal driving my gauge is about 175-185 degrees. I do some short autox runs and the engine temp gets up to 195-210 degrees, and drops down with idleing. On longer courses (60 secs or more) the temp will spike to about 230 deg briefly, then drop back to about 205-210 deg idling. This is probably pretty normal, with my setup. Currently stock mk2 radiator, dual electric fans, oil cooler mounted in front of radiator, gt30 single turbo, max of 20 psi boost.
I believe (from reading online) that the stock 1JZ/2JZ thermostat is a 82 deg C unit, thats about a 174 deg F. Sounds like a good fit to me.

Here's my thought, without upgrading the radiator (which I probably will do anyway), if I drill a small hole in the thermostat body, that would keep the engine coolant a bit cooler, essentially decreasing the rated 82 deg C. to something slightly lower? Ideally, I would like a thermostat that opens at about 165 deg F. , but can't find one.
Mishimoto has a racing application but that thermostat is rated supposedly at 61 deg C., which is 130 deg F. really too low for me. I'm not road racing, so its just the quick temp spikes that concern me. I guess I could lower boost, but what fun is that?

Thoughts?

Don

 

[f00g00]

Get a larger radiator first, then if you need more, ditch the e-fans and go mechanical and lastly don't try to modify the thermostat by drilling on it.
Read this article for another idea but be aware there have been issues with the redline if you google it.
http://www.turbomagazine.com/features/0703_turp_cooling_system_additives/

 

[OneJArpus]

I see 197-200 on a hot summer day with it getting to 205 some times. When i shut the car off it'll go to 230-235 but 1 minute after starting it'll be back down to 200. Thats with a LS400 Clutch 7M blade Koyo & a MP T61 with a small trans cooler in front of it for the power steering and intercooler. No fan shroud but i have the lower engine cover

 

[Poodles]

Messing with the t-stat isn't going to change your temps under load, just lengthen the time needed to warm up (and screw up the tuning since it's tuned for a higher temp). You need more capacity.

 

[toy4speed]

Ok, thanks for the replies. Drilling a hole in the t-stat seems like a useless move. I have a intercooler that blocks a significant part of the airflow to the radiator. Maybe I can change to a smaller intercooler, something like 24" wide and 6" tall, that would allow more air to reach the radiator face. Between the oil cooler and intercooler, a large portion of the radiator is getting air blocked. I can try moving things around a bit. The water wetter seems to have mixed reviews, and l like redline products generally.

Don

 

[te72]

I can give a bit of input here, but not much. Recently, I removed my AC components from under the hood, since nothing is hooked up anyway. On the highway, I would see temperatures around 210 when cruising the interstate at 75-80mph. Now, without the condenser (which wasn't being used) in the way, my temperatures are anywhere from 190-200.

I know the Mk2 engine bay can be a bit tight, but can you possibly route in some fresh air to the radiator through the use of ducting? Sometimes it is more about where the air is going. Keep in mind that it will always take the easiest path, so any open holes that let the air by, are going to do you no good whatsoever.

 

[Poodles]

The MKII definately doesn't have as much ducting and undertrays from the factory as the MKIII. Stock radiator is a bit smaller as well (and if it's original it's probably clogged).

 

[toy4speed]

Thanks for the input Brad! I know the air flow to my radiator (which is fairly new) is compromised, so I'm planning to look at getting at least 1/2 of the radiator face exposed to air flow. That will involve using a smaller intercooler, and moving my oil cooler around. I had plans from way back (I have more plans than I can remember) to make an aluminum cover plate for the area in front of the radiator. A cover plate on top, and one below, so the air entering he front grill and below the bumper will be funneled to the radiator, and not everywhere else (like it is now). If that is not enough, then I'll start looking at radiators.

Don

 

[te72]

Sounds like you have a pretty solid plan in place Don, you'll have to update us if your tinkering returns good results, with pictures!

 

[toy4speed]

Here's a pic of my current intercooler, its a Mishimoto bar/plate, seems to work very well for dropping intake temps down, the measurement by touching the inlet and the outlets shows a big difference in temps. That part is good. The not so good is the placement and size of the intercooler covers up much of the radiator face. I mounted the intercooler in front of the radiator because I didn't want to put too much weight in the forward part of the car, for weight balance reasons. Yeah, I figured some airflow would be restricted but knowing that cars have the a/c condenser in front of radiators too, I thought it might be ok. Apparently not. From my readings, bar/plate intercoolers cool better than the tube/fin intercoolers, but also restrict airflow more (if you need airflow to continue to the radiator), they are also almost twice as heavy as a similar size tube/fin intercooler.

My intercooler piping is also kept very short with this location, as the piping enters the engine area on each side of the radiator, so a short distance up to the turbo, and to the TB.

Now I am going to try a tube/fin intercooler, about half the height of my present unit, so more air can get to the radiator, and maybe save about 10 lbs in the front of my car.
Whether the cooling capacity of a smaller intercooler will be ok for my needs, well that remains to be seen.

Crazy power is not essential for me, so if my boost must be limited to around 18 psi, that's ok I think.

Don

 

[te72]

Can't really put the intercooler too much more forward anyway, I would think. I would try a shorter height like you suggested you were doing. If nothing else, make some ducting to get air where you need it, fog light holes (well, fog light holes on the Mk3 area, never did figure out what was meant to go in those holes on the Mk2 since the fogs are in the grille) and some tubing could help you out.

I believe IJ put fans on his intercooler to help with the heat exchange issues he was having...

Anyway, do you have a build thread, or pictures of your car somewhere Don? My poor Mk2 is feeling a bit neglected, and I could use some inspiration to fix her up a bit now and then, yours looks like it is in pretty good shape from what I see.

 

[Poodles]

Looks like the end tanks are blocking a LOT of air as well

 

[toy4speed]

Ask and you shall receive

I built my 5mge n/a motor and went to several SCCA Nats in D-Street Prepared, car was competitive, but underpowered. I have several threads regarding my 5mge days, with triple throttle bodies, SDS standalone install, etc. That however was another time. The 1jzgte became my main project end of last year, and sucked not only my time, but my funds. I'm sure many will understand

Here is my 1jz build thread over in celicasupra.com:

http://www.celicasupra.com/forums/showthread.php?64643-Don-s-1JZ-Autox-Project&highlight=

Because of the 1jz motor I have ventured into several other forums for info and advice. Great to interact with new folks!

Don

 

[te72]

I may have actually stumbled across your thread on CS when I was researching a 1j transplant into my Mk2. Realized I would have postponed my Mk3 completion far more than I would like, and the deal on the engine fell through anyway, so I changed my mind.

Plus, I've got that Chevy to finish, so the Mk2 will be the daily once the Mk3 goes under the knife for the widebody... Something about the Mk2 though, just love those cars. My ideal Mk2? Something high revving, with enough displacement to stay NA at high altitude and still be fun, and piped properly with ITB's and the related goods.