deveous9 Reader
Dec. 14, 2011 11:51 p.m.

Setting up my mk1 rabbit for track day use and was wondering if I should remove or keep the thermostat? Should I just get a 160 degree thermostat with a 170 degree fan switch or should I bypass the thermostat? Any help would be appreciated.

BoxheadTim SuperDork
Dec. 15, 2011 12:03 a.m.

For track days and assuming your radiator is in good condition I'd just run it with a good thermostat at the OEM temperature or at a little lower (say 160-170 in a car that normally has a 180F thermostat). Removing the thermostat is going to extend the time the engine needs to warm up and normally doesn't add enough flow through the radiator to make up for the fact that you're running cold (and thus rich) much longer.

What I would do is get a good water temperature gauge, preferably with peak hold, make sure the cooling system is up to scratch (and fix it if it isn't), then run a track day and watch the coolant temps. Unless they're in scary territory I'd run with the standard system with maybe an upgrade radiator and potentially an oil cooler, but I'd decide after checking if it needs either.

novaderrik Dork
Dec. 15, 2011 1:34 a.m.

set it up like the oem engineers did first and go from there. the thermostat only sets the minimum operating temp, so if it does overheat then you've got other issues.

alfadriver SuperDork
Dec. 15, 2011 6:45 a.m.
novaderrik wrote: set it up like the oem engineers did first and go from there. the thermostat only sets the minimum operating temp, so if it does overheat then you've got other issues.

That's a very good way of putting it.

mad_machine SuperDork
Dec. 15, 2011 8:32 a.m.

agreed. If you want to remove the t-stat, you need to install a restictor to slow the flow or the car will never warm up.

deveous9 Reader
Dec. 15, 2011 8:45 a.m.

All very good reasons to leave on a thermostat. Think I will stay with a 160 degree stat and a 170 fan switch. Is that a good combo for track use?

aeronca65t Dork
Dec. 15, 2011 8:48 a.m.

For a fairly modern fuel injected car (1980s to 1990s), keeping a thermostat in place is probably a good idea. Maybe drop it down 10 degrees F (ie-from 190 to 180). The cooler temps may help keep oil temps down.

I forget if first gen Rabbits use a carb or not.

Many very new cars run thermostats around 210F but the systems in these cars are calibrated on this higher coolant temp. If you run a cooler thermostat is something like a 2008 model, you may end up causing it to run slower with less power.

Those of us running older, carb-ed vintage cars often use a "blanking plate" (the restrictor mentioned above). I generally just create a restrictor plate from an old thermostat. Just cut off the "guts" (spring and valve) and use the remaining donut as a blanking plate. For a race car, this keeps things simple (no thermostat sticking) and less to go wrong.

BoxheadTim SuperDork
Dec. 15, 2011 8:52 a.m.

In reply to deveous9:

Given that most modern-ish engines (ie, stuff from the 70s onwards ) is designed to run at higher temps (ie 200/210) than that, why do you really want the fan to kick in at temperatures that low? Maybe I'm missing something obvious here as to why you don't want to run it warmer than this but I still think it's not a good idea.

Woody SuperDork
Dec. 15, 2011 8:56 a.m.

I tried a gutted stock thermostat like the Spec Miata guys use in my 96, but the engine never came up to proper operating temperature and I wasn't comfortable pushing it too hard. I switched back to a stock piece and never had a problem.

Unless you're running nose to tail for the duration of a track session, it shouldn't be an issue if everything else is working as it should.

Alternatively, you could always just lead from start to finish like I always do...

mad_machine SuperDork
Dec. 15, 2011 9:50 a.m.

track day use.. I would be tempted to run a fan override. This way you could manually turn the fan on if necessary.

iceracer SuperDork
Dec. 15, 2011 4:45 p.m.

The old Ford flathead V8 would overheat when driven hard,ie:dirt track racing. Problem was too much flow because of two water pumps. After installing restrctors, problem solved.

wbjones SuperDork
Dec. 15, 2011 7:30 p.m.
mad_machine wrote: agreed. If you want to remove the t-stat, you need to install a restictor to slow the flow or the car will never warm up.

are you sure ? my '76 Civic did fine w/out a thermostat

deveous9 Reader
Dec. 15, 2011 9:03 p.m.

This would be my first vw that i would track. Dont know how much of a beating these things can take compared to other cars that i have tracked before. If i see the starting to overheat with a stat i will remove it.

16vCorey SuperDork
Dec. 16, 2011 8:00 a.m.

I ran my challenge Rabbit for years without a thermostat. It did fine, but it never got up to normal temps. The gauge would creep up a bit while sitting still, but as soon as you were moving it would drop like a rock to the bottom of the gauge. I'd use a thermostat.

81cpcamaro Reader
Dec. 16, 2011 9:28 a.m.

I run the Camaros engine with a gutted thermostat (when it was in the El Camino), it only ran cool when the outside temp was below 50 degrees. But I gutted it after having two different thermostats that kept sticking, no fun watching the temp climb to 230+ before they would open. Unless it gives you a problem, I would run with a quality thermostat and maybe change it out every so often just to be safe.

drmike Reader
Dec. 16, 2011 11:48 a.m.
iceracer wrote: The old Ford flathead V8 would overheat when driven hard,ie:dirt track racing. Problem was cavitation at the pump because of a high pressure drop through a poor coolant system design combined with marginal pump efficiency. After installing restrictors to raise the pressure delta across the pumps, thereby increasing the suction pressure and delaying cavitation, problem solved.

Flathead story, Revision A

iceracer SuperDork
Dec. 16, 2011 5:23 p.m.

My version was simpler. (;) for us guys at the track.

For whatever reason, the restrictors fixed it.

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