How Hot?

[cherokee]

How hot do your Opel race cars run, and where do you have the temp. probe.
I can not seem to get my car to run under 200-220+, this is at idle with the fans running. I have the probe in the stock location. I am beginning to think that the AutoMeter sending unit is iffy. My Oil temps will just be starting to move and the water temp will already be around 180. The oil temp sending unit is right before the oil goes into the oil cooler. New rad. and I put in a restrictor, I was running it open. The car has pretty good power (till it gets too hot). for a mule motor. I realy want to get this cooling issue figured out before I install the new race motor. Any other ideas on cooling off this beast. I am inches away from going to an other rad. and doing some cutting to get it to fit. I am thinking if I can't keep it cool at idle I sure am going to have problems on the track, at high RPM's. Also on the list is a new WP pully any ideas on size what car to pull the pully from.


PS. it is an ITB GT.

Thanks

[petrieopel]

I'm guessing since you're using an AutoMeter sending unit that your gauge is also AutoMeter. Rally Bob told me that 193 degrees is normal temp. My car runs about 180 at idle.

[namba209]

To check out if the temp system is indicating correctly, here's and old trick that's been around for more years than I can remember, and cheap too. Get hold of a cooking thermometer, one that goes above 250, pop the radiator cap and stick it in the top of the radiator in the coolant but not touching the tubes inside. You'll get a fairly accurate indication of the temp of the coolant as it goes into the rad. You can compare it against the dash indicator and go from there. I use this trick, on the stove, to check out the thermostats before I put in the car. HTH.

[RallyBob]

GT's will run hot at a fast idle speed, especially just coming off the track. Did you make sure the sender is the correct value for your gauge? Example: a 250 degree sender on a 300 degree gauge won't read correctly.

Do you have an electric fan? Pusher or puller style?

Underdrive pulleys help a lot 'at speed', but will be worse coming off the track after hot laps or just idling around. Biggest issue with a GT is lack of airflow through the radiator and the engine compartment in general.

FWIW, if your cooling system is up the task (new or rebuilt radiator, new hoses, etc.) a higher pressure radiator cap helps a bunch. I always run a 22 psi cap for racing, no coolant, a water pump lube, and Redline Water Wettor to improve heat transfer. I use a 4" custom crank pulley and a 6" water pump pulley, and though others don't like it...I run without a thermostat, using just a 7/8" ID restrictor in the thermostat's place. Racing temps are 185-190 degrees this way, going to 210 degrees at idle after a race.

Bob

[cherokee]

Thanks for the replies, a little more on the car.
The rad is a re-cored unit, I am running a restrictor, I will have to check the size again when I get home but 7/8 sounds about right. (I made it the size that someone on the IT board suggested, I think it might have been one of the other Bob's, if not you Rally Bob) The sender is the one that came with the temp gauge. I am running just water in the car no coolant. I will up the cap to 22 not sure what it is now. I am running an electric fan, have tried puller's now I have a higher CFM pusher fan.

I am going to open up the heater core get coolant flowing there again and get the fan running for that too. Vent the hot air out the car (does this sound like a good idea). Any little bit helps. I have this fear of hot water in the car, but I need to get this thing to run at a good temp.

Could you tell me what size pully you went to Bob, and what car supplied the pully. I was thinking about cutting the center out of one of my opel pullies and then welding up a new one. Is this how you did it? Just not sure what size pully to go with.

[namba209]

I didn't see in previous posts if you put in a 3-row core in the radiator, that would be a plus of you did. Plumbing in the heater core would help but how much I don't know, but it's one of the things I taught my girls to do if they ever got into an overheating condition. Turn the temp full on, select defroster mode, and turn the fan on high speed. Don't forget to roll down the windows too.

I just posted pics on my electric fan setup for the V-6 on replacement OEM fan thread, along with the specs as a pusher or puller. You may want to check it out.

[cherokee]

yep it is a 3 core rad, sorry I forgot to mention that.

[RallyBob]

Originally Posted by cherokee Could you tell me what size pully you went to Bob, and what car supplied the pully.

As I mentioned before I used a 6" water pump pulley and a 4" crank pulley. This reduces water pump speed by 34%. The pulleys were custom made.

Bob

[cherokee]

I will have to check but last I knew changing crank pully was a no-no. I will start with 6" and go from there. Thanks for the info.

The new cap and having the heater core flowing brought the car down quite a bit. I went from 200 at idle to 160. Now to get it to a track day and see how it does. I think that MAM has some days this year.

Thanks for the help guys.

[jeff denton]

My car runs hard at about 190, when a caution flag comes out I turn on the fans to keep it from jumping up to 200. Same thing when I come in the pits after a race. I need no fans during green flag laps, use plastic sheeting to duct about half of the grille up to the Honda Accord radiator. Stock pulleys, though I should underdrive them a bit, however I am seriously considering going to an electric water pump. I use a thermostat, it opens at 180, as my Autometer mechanical gauge probe is in the radiator top tank the gauge jumps right to 180 when thermostat opens. I am quite surprised and very pleased that my cooling system works great! But as I need more horsepower any way I can get it, I want to do away with the power robbing pump and
v-belt.
Our rules disallow any "auxilary cooling" which would be a heater... Removing the heater sure opened up the firewall into the interior "tunnel", this caused some questions. I was only obeying the rules by removing the heater, there's no rule about sealing the firewall other than " holes in firewall between engine and driver compartment must be closed with sheetmetal..."

[RallyBob]

Originally Posted by cherokee I will have to check but last I knew changing crank pully was a no-no. I will start with 6" and go from there. Thanks for the info.

The rules now allow alternate crank pulleys. This is a fairly recent rule change. Besides, you'd never fit a 6" water pump pulley with a stock crank pulley! The overlap would be tremendous. I don't recall exactly but I think the most you can enlarge the waterpump pulley with the stock crank pulley is 1/4" or so?

Underdrive pulley pics here: http://www.opelgt.com/forums/showpos...8&postcount=44

Bob

[cherokee]

Changing the crank pully would most likely be the best thing to do, I can slow down everything with just one change. I am happy again with how the car is running, in the morning I will pound out the Spec NASCAR....errr Spec Miata dent. and see how everything looks. Get it up to MAM and see how it runs, at pace.

[jeff denton]

Somebody at this site once showed us some nice aftermarket reduction pulleys, I wonder where they went?

[davegt27]

if any one wants to get under drive pulleys made up i would be in for that

http://www.nevo.biz/


http://www.aspracing.com/intro.htm


http://www.nonstoptuning.com/pageNormallyAspirated.htm

Davegt27

[petrieopel]

I would be interested in purchasing an underdrive pully.