low temp thermostat

[Eddy]

Hoyhoy.

I would get temps up to 108 when going hard on the track, then changed things to help with cooling, but still had high temps.
Then woke up to switching the aircond on, on the cool down lap. When I pulled into the pits, she was cool & ready to switch off.

[Martin]

However, the point I wanted to get across is, that heat soak from the engine can elevate the water temp enough to trip in the fans. After the ignition is switched off. They don't run by magic.

It's certainly possible and every car is different

I'm not experiencing any heat soak with my Nissan Pulsar race car,
even after a 45 minute race around Wakefield Park
But it's NA - Turbo cars may be more susceptible to heat soak

Thanks for the details on the Polo cooling system,
it sounds fairly conventional and should be easy to work with (modify)

[sambb]

I'm stoked that the electric water pump is dedicated for the turbo, that is a cool little feature. Logically I suppose a lower temp thermostat won't help much after the car is shut down since the water pump isn't moving water around, and the electric one is most likely just for the turbo, and like Martin said there is only convection flow that may happen to some degree.
A lower temp T stat would have to help for sustained track running though surely. I'd be curios what Seans temps are with that 70 degree thermostat. But that's not really my problem on short runs.
Tridon do a standard OEM replacement and a 'high flow' version that allows 30 percent more flow once cracked, so i'll use that one. The only thing really left open to me is to finally re-gas the A/C so that I can make use of those fans on cool down too.
Thanks for all the input fellas.

[Martin]

I'm stoked that the electric water pump is dedicated for the turbo, that is a cool little feature.

Smart German engineering

A lower temp T stat would have to help for sustained track running though surely.

I doubt it
People use these 70 degree thermostats on the street and don't have problems - not highly stressed
But at the end of the day, there is a hot piston to bore clearance that is very important, especially in modern engines (running 5W30 oil)
Running cooler may reduce that clearance and cause more friction and wear

When I was a kid there was a nasty used car sales trick
When they traded a car that was blowing blue smoke they would gut the thermostat
This reduced piston to bore clearances and no smoke
If the buyer noticed the temp gauge at 0 the salesman would let the car idle to show it would come up to temp (no air through the radiator)
After buying the car the new owner is actually wearing out the engine running like this
It's an extreme example but all the race cars I mess run at 90 degrees
The racing guys are really hard core - if there was a good reason to run the engine at 70 they would

Another point: Running at 70 degrees, your oil may be cooler and as such running at a lower viscosity, which could mean more wear

Tridon do a standard OEM replacement and a 'high flow' version that allows 30 percent more flow

I've seen those and am very doubtful about the 30% claim
Just like a turbo inlet restrictor or an air flow meter, to flow 30% more would require more open area
Those Tridon thermostats look much the same as stock

Other points to consider:
30% more flow is huge, the water pump will be what actually determines the flow rate
Faster is not necessarily better - 30% more flow may not cool the engine and water may be travelling through the radiator too fast to be cooled down

[sambb]

I do see where you are coming from Martin I do. For sure you've convinced me that in my situation where its more of a hot shut off issue rather than a sustained running temp issue, I probably would see no benefit from changing to a lower temp thermostat. But for the track guys, our car has commuter rated cooling. Take Eddy's car (the closest thing here to a proper race car from what I can tell) and he said he's seen sustained 105 degrees on the track and that's with an oil cooler and tricky bonnet vents etc. Short of fitting an uprated radiator core, surely a cooler thermostat could help that situation by at minimum buying more time before temps get that high in a system that is otherwise being pushed to the limit. ie his fans would make no difference at full tilt, his thermostat would be wide open in either case, so its basically engine versus radiator - but if he starts from a slightly lower base it'd have to take a hell of a lot longer to get up to those peaks, maybe a whole session. Its possible isn't it?
No I do agree with you regarding the 30 % flow thing. Its hard to know what effect it would have even if it was true. It had crossed my mind that if the flow was too fast that the coolant may not gather up enough heat on each pass. I've got no idea if OEM thermostats are built to restrict max flow by design. Maybe the water pumps have punchy flow from low rpms and the thermostat itself does in fact limit peak flow.

Just for informations sake, tridon do standard flow and 'high' flow thermostats in 71, 75, 77, 79, 82 and 88 degrees increments. By searching under our car/engine, the stock standard flow is the TT1-190 (88 degree) and the high flow is TT2000 - 190. They both have a 54mm flange. But they then have lower temp versions of both of these:

Thermostat | Tridon for the TT1 range of temps

Thermostat | Tridon for the high flows.

[Martin]

When you say the track guys, you mean hill climbs?
At race tracks we have great airflow through the radiator

I do agree with the commuter cooling design, and combined with hill climbs you're in a tricky situation
The conventional approach to not being able to manage engine/water temperature is to increase the capacity of the cooling system
Is there a larger radiator available for your car?
It would be the single most effective change you can make

Water injection into the inlet and over the radiator would be worth looking into
(MCM did a crude water over the radiator setup and got positive benefits)

Will a 70 degree thermostat solve the problem, starting from a lower base?
It's possible it will have limited effect
Without adequate airflow through the radiator (short hill climb),
in a car that is struggling to control temperature
does it mater what temperature the thermostat opens?
I mean, once the temperature goes north, you're back to the original problem
Maybe your second run will be cooler, but eventually the fundamental problem will occur

The oil cooler will only cool oil - not the engine - and only with airflow

By all means use the +30% thermostat - they will work fine
My only point was ignore the +30% claim
(I think I have one in my Pulsar race car! LOL )

[Martin]

All I want is to smooth out any big temp differentials between the engine and radiator and the existing thermostat doing big temp dumps in and out of the engine.

This won't be happening - the thermostat opens and closes slowly

[Martin]

Oh - get a manual override control of both fans
Let the engine warm up, turn on the override just before launching out the gate, leave them on for 10 minutes when you shut down

That is likely to help you...

[h100vw]

The oil cooler will only cool oil - not the engine - and only with airflow

The current oil cooling is assisted by the heat exchanger, that is part of the oil filter mount. The purpose being that the heat in the water warms the oil as the engine heats up from a cold start. Perfect logic for colder climates than Australia.

When the oil goes over 90degrees the heat transfer is in the opposite direction. Heat transfers to the coolant.

If an external oil cooler is fitted as Eddy has, including a thermostat, then much of the thermal load of cooling the oil with the coolant is removed. Consequently, the water temps will be way down. Far enough that it may be possible to run a smaller radiator.

Especially true if the heat exchanger is deleted.

[sambb]

jeez I just sat down to a coffee after waking up after my nightshifts (which is why I've been a posting fiend of late) and that whole other variable of inter dependent oil temp is too much for my dusty brain to comprehend right away.
So it sounds as though the exchanger system once everything is up to temp will work to hold the oil and water in equilibrium around 90 degrees.
So if you were running an oil cooler (and especially if you didn't have the heat exchanger in place) you'd need the oil system to be thermostated or at least have a manual bypass of the oil cooler in place for when you're not on the track or its winter or your oil may not get up to temp?
So if the spec oil temp is 90 degrees, how far outside of that will our oil temps climb just in street driven settings, and how out of hand do they get when the car is pushed hard (assuming the exchanger is still in place in a stock setup)???

[h100vw]

jeez I just sat down to a coffee after waking up after my nightshifts (which is why I've been a posting fiend of late) and that whole other variable of inter dependent oil temp is too much for my dusty brain to comprehend right away.
So it sounds as though the exchanger system once everything is up to temp will work to hold the oil and water in equilibrium around 90 degrees.

It will try it's hardest to do that, yes. What you see on the temp gauge is damped, so could be higher or lower in reality. VCDS is the true gauge showing actual numbers. I only every saw my polo indicate anything but 90 or a happy laps at QR towards the end of the session.

So if you were running an oil cooler (and especially if you didn't have the heat exchanger in place) you'd need the oil system to be thermostated or at least have a manual bypass of the oil cooler in place for when you're not on the track or its winter or your oil may not get up to temp?

I'd never fit an oil cooler without a thermostat in it. Overcooled oil is as bad as under cooled.

So if the spec oil temp is 90 degrees, how far outside of that will our oil temps climb just in street driven settings, and how out of hand do they get when the car is pushed hard (assuming the exchanger is still in place in a stock setup)???

Back in the U of K, I had an oil cooler on my G6O GTI. Circa 200hp. Oil would rip past 120-130 degrees during a track day. With the oil cooler on and the heat exchanger deleted, each session, 20 minutes per hour for a full day. The oil temps climbed by 5 degrees, due to starting the session with the oil just a little hotter.

You could see on the dash that within half a lap off the gas, the oil temp count back down.

inline answers

If there was a downside to the G60 set up, I over spec'd the oil rad and didn't appreciate the total effect the oil heat had on coolant temps, once removed. VW clearly balanced the size of the radiator against the heat generated by the oil.

So the water temps were well down all year round. To such and extent that it would barely lift the needle off the stop in winter. I doubt that this would be a big issue here, driving in traffic, plus the higher year round average temps.

[sambb]

Thanks. There's been a lot to digest in this thread. One last question gav - is there an oil temp sensor that can be monitored in vcds? I went through it quickly last night but couldn't find anything.

[Martin]

The current oil cooling is assisted by the heat exchanger, that is part of the oil filter mount. The purpose being that the heat in the water warms the oil as the engine heats up from a cold start. Perfect logic for colder climates than Australia.

Good point

I deleted that item in my Nissan 350Z

[sambb]

"I just got off the phone to VW parts. The part they carry for our car is an 83/102 degree. My best guess is that this is what's referred to as the stock 90 degree thermostat by ECS. The ECS/neuspeed one is listed as 82 degree which probably means open 92/closed 72. If anyone can confirm that that's how they name the thermostats relative to their open/closed specs that'd be great."

Well at any rate, given that the consensus seems to be to leave the thermostat at the stock 89 degrees, the way thermostats are designated may be a bit of a trap for people not even trying to make a change. I'd always assumed that a 90 degree thermostat opened and closed at values above and below that to maintain a 90 degree average. Like in the post above where the part number for our car is on VW's books as a 83/102 and known elsewhere as an 89 degree or something. But I've since spoken to a lots of other people including mechanics who said they always thought a thermostat was rated at its cracking temp. eg the tridon catalogue does this too - a '180' is a 180 farenheit (82 Celsius) thermostat that the catalogue says cracks/opens at 82 degrees! etc

So whats the truth. Is the local VW one listed as 83/102 actually an '83 degree' thermostat, maybe taken one step cooler by the local factory for aussie climes, and the 89 degree ones I've seen for our car were euro/north american spec. Or is the one that VW hold in fact a 90'ish degree because the open/closed temps fall either side of that temp? I'm starting to think it could be the former.

[Martin]

Yeah, I thought the rating was when they opened

You can test them in a saucepan of water to find the opening temperature