Marlon

I see that German 160-something thermostats are available for these cars - anybody put one in for the street - thoughts???

SH || NC

Thoughts? I think when the stock system is properly maintained and functioning correctly that its more than adequate. Lower temp t-stats do not increase the capacity of the system; the 3rd radiator does though [Wait - as a tip you might already have the 3rd radiator, right?]. If you are looking for something to tinker with, clean the radiators.

Marlon

Yes, Tip has the center radiator. Radiators are clean.

Jake Raby

I have completed the evaluations on the LN Engineering 160F thermostat and the average temperatures I have seen logged this summer were 12F between the stock vs 160 thermostat. I like the unit because it reduces the thermal shock that the engine sees when the thermostat does begin to open.

I recently completed an engine that made 87HP more than it did stock (added 400ccs of displacement through a big bore, added CR and headwork) that engine with the low temp Tstat ran cooler than the stock engine that it replaced with no other changes to the cooling system or car. The difference was almost 20 degrees.

Next month I have a track day and we'll be swapping thermostats between both my Boxster and 911 test vehicles on saturday evening so we can data log the differences on the same track and the same ambient temps, speeds and drivers...

It does work, EVERY engine I create gets one standard..

Marlon

Jake - I'm merely looking to reduce normal operating temp. Is it DIY-able to change the t-stat??? My depth of P-car repairs is stuff like changing to pressure fed tensioners on older 911's (have done 3 of them - easy), complete brakes and other 'easy' stuff - plugs on 993's (hard).

1999Porsche911

Unless the lower thermostat also increase the flow of the coolant, it will not change the coolant tenmperature by anything measurable. Even running without a thermostat will only lower the coolant temperature by a few degrees, and definately no where close to 12F lower than the normal 194F. This is for both the 3.4 and 3.6 engines.

Marlon

Strange - when I install a cooler t-stat in my Impala SS, the car runs so cold that it will not heat the passenger compartment in the winter time. It runs better in the summer though - nice and cool - you can run just a tad bit more advance thru the computer that way - safely. The whole idea behind the LT1 engine was to route the coolant thru the heads in a reverse routing and drive the head temp down enough to crank up some serious advance on pump gas. The LT1 Chebby Impala is a beast because of it. If the 996 cooling capacity is up to it, a cooler t-stat should result in measurably cooler running temps no problem.

1999Porsche911

I didn't know we were talking about Chevy Impallas.


I have studied the cooling systems of the Porsche 3.4 and 3.6 engines extensively over the past 5 years and it is impossible to run the engine with a coolant temperature at 182F in any climate. Whether it is 0F outside or 100F, short of coasting into a cool breeze, you will never see 182F once the engine has warmed up, even driving moderately.

The biggest drop in temperatures occured in below freezing temperatures without a thermostat where we recorded a 4% drop from targeted coolant temperature . Cooling system was stock with no modifications. Increasing air flow over the radiators had a similar effect while running the stock thermostat.

Without an increase in fluid and/or air flow, you will see no reduction in coolant temperatures.

Marlon

Jake Raby has indicated the opposite of what you say. I'd be inclined to go with the experts in this case.

1999Porsche911

So, you actually think Jack claimed he can reduce your coolant temperatures to 182F? He made no such claim. Like I said, it is a fact of physics that unless the flow of the fluid is changed, there will be no change in coolant temperature. Everything being equal, a opening setting on a thermostst can only be used to increase the coolant temperature. It would take a change in the design of the thermostat to either increase or decrease the volume of coolant flow to have any cooling effect. Otherwise, simply having the thermostat open earlier will just take longer for the engine to reach the same engine it would reach with the stock thermostat.

Tippy

Here's the answer to your question above.

If running thinner cylinder walls from boring and higher compression ratios on a stock cooling system with just a lower t-stat reduces overall coolant temps, then the stock engine should easily benefit from one.

fpb111

1999porsche911,

Let’s advance a hypothesis:
A 911 Porsche cooling system is designed to have a greater capacity to shed heat then the engine’s ability to create heat. So a controlling device is needed to control these two at a predetermined point to facilitate efficient operation of the engine, say 190 degrees. Do you find this a reasonable assumption?

I think the physics of this might be:
If one runs a water cooled engine at maximum heat load with the cooling system operating at maximum heat dissipation and both systems, generation and dissipation, reach equilibrium at 220 degrees with a fully open thermostat. The temp the thermostat fully opened, 160 or 180 or 110 would have had no effect at end point.

I postulate that:
If one were to run the same engine at 50% heat load with the same capacity cooling system with no thermostat the temperature at equilibrium would be lower, for arguments sake 130 degrees. If so adding a 160 or 180 thermostat at the output of the heat producer (engine) would be the controlling factor of when the engine reached equilibrium - 160 or 180 degrees. The cooling system with its extra capacity would be much cooler then the engine.

Marlon

I think installing a cooler thermostat will result in a cooler running engine if the radiator system is up to it. Simple. I will report the results later.

Paul 996

So the net net is that by opening the thermostat earlier with a lower temp thermo it takes you a lot longer to reach the equilibrium temp between the oil and the water heat exchanger.

You will still get there but it just takes longer and in some cases due to the brief drive or conditions you may never reach it.

Now adding the 3rd radiator (for coolant) adds additional coolant capacity and "cooling surface" which is another story altogether.

Marlon

The 'net net' is that by running a cooler thermostat together with a capable cooling system, your car will run cooler. Like I said before with the Impala real life example - with a cooler, sooner opening t-stat, it never ever really reached a condition in the winter time where enough hot water was generated to heat the cabin to a comfortable temp. The 'net net' for the Impala was that the Summer running temps were lowered significantly and with a computer reflash the car picked up tangible power. In the case of the 996, I am looking simply to lower the constant operating temp and lower hot soak starting point. The sticking point for the 996 is if it's cooling system is already operating at max capacity or near max capacity at 180 - 190 degree already, which given the engineering issues associated with the 996 engine, it would not surprise me. (my gut feeling is that the engine life issues center on cooling problems + other stuff) So if there is very little extra cooling capacity with the three radiators and those long coolant runs, the 160 deg stat might be a wash. But I intend to find out if the t-stat is diy-replaceable. BTW: Tips already have the center cooler.