M60 T-Stat, use 95C or 85C one?

[bubba966]

Can't say I'm too happy with the M60 using a 95C stat as that seems a bit high to me. Wondering if BMW has a lower temp stat I found one available for the M60 Gulf Version that's an 85C stat (part #11531729720).

Anybody use the 85C stat in their M60? If so, how's it run? And is the software in your car stock or not? Having the 93 octane E.A.T. software in the car and seeing how much more power that produces I can't help but think that the 85C stat would be a good idea. Should help the cooling system last a little longer as well I'd think.

I'd just buy one and try it, but the 85C stat costs about 4x what the 95C stat does. So I don't really feel like going out and dropping $100 on the 85C stat just to find out it's not a good idea...

[yaofeng]

I don't even remember what I used. But based on your description of the price differential I must have installed the cheaper one. I don't seee anything wrong with it.

[winfred]

the 95 should be ok, it's cooler then the later v8 thermostat, they went to a 105 and typically cycle between 228-236 when everything is working

[bubba966]

I'm not having any problems with the 95C one. But a cooler running engine should be easier on the cooling system. And as I've been having some of that crap out on me in the last week it's been making me think or a cooler stat.

Cooler running engine usually = more power, while a hotter running engine = better emissions. I could care less about the emissions as my car runs stunningly clean. Any slight drop in emissions from running a cooler stat wouldn't make any difference when the emissions test comes around.

Mostly wondering if the 85C stat factory cars had any other provisions for that stat temp. That's a lot bigger difference than the M50 stats that are 88C & 92C. S38 stat is 79C.

[yaofeng]

Hotter running engine has more power.

[mottati]

bmw bumped up the thermosat to help with the nikasil issues, cooler temps damaged the cyl walls more quickly. Should be fine with an alusil engine. The M cars run 79C thermostats (s38 and s62, maybe others).

[bubba966]

Hmm, maybe I'll give the 85C stat a shot as I've got an Alusil block that's in great condition.

[Fetch]

Hey there, I'm running the 85C thermostat on my M60 3.0, I posted the same question as you awhile ago when I noticed my water pump was about to blow up - and was surprised to find I had purchased an 85C thermostat partially accidentally...

Follow up, I'm enjoying the 85C thermostat on my car (nikasil)....I noticed _no_ change in MPG at all, car runs just as well as before....The temp needle hovers just below center with the 85C.

Go for it, Good luck!

[Jon K]

Hotter running engine has more power.

actually a colder running engine (between 165 - 185) has more power, but higher emission output.

[yaofeng]

Read this and tell me if you still think a colder engine has more power.

http://www.grc.nasa.gov/WWW/K-12/airplane/work2.html

[bubba966]

Read this and tell me if you still think a colder engine has more power.

http://www.grc.nasa.gov/WWW/K-12/airplane/work2.html

There's a lot more to the entire process of the internal combustion engine than just one thing like that. Not saying that's an invalid fact, just that there's a lot more that effects the entire outcome than just one thing like that.

The temp range Jon mentioned has been proved to be the best temp range for producing the best power. And just as he mentioned higher temps reduce emissions outputs.

Exactly the reasons why cars are now running in the 200-210 range (to meet those even tightening emissions standards). And there's a good reason why the boys in the M Division put 79C (174F) stats in the M series motors (who puts out some of the best power to displacement NA engines in the world).

Don't believe it if you don't want to. That's fine by me. Mottati was good enough to remind me of why BMW bumped up the running temp of the M60 (I'd read about that so long ago I forgot). And Fetch was nice enough to give some experience running the 85C stat.

I'll run an 85C stat at some point. And you can continue to run your 95C stat. And we'll both be happy.

[yaofeng]

Of course I realize temperature is not the only factor. Many things come into play and are affected by temperature, mechanical clearance, seal life, lubrication breakdown, etc. Every engine is engineered to operate in a range of set temperatures best for the performance.

A hotter engine is a direct result of hotter combustion temperature. Does it produce more power? Of course. This is from a pure thermodynamics point of view of gas combstion. Is it good for the endurance of the engine? If it veers away from what it was designed for. No. It may or may not even produce better performance all things considered.

[whiskychaser]

These are only the temps the stats start to open. So that prompts two questions:
1. When are they fully open and do they open at the same speed?
2. What is the operating temp of the engine when its warmed up fully?
If the answer to 2 is greater than 95-and I rather suspect it is - what difference does it make? Its function is to get the engine to operating temp. Once its done that it plays no part. Its a low tech item so do I really believe it does what it says on the tin? Maybe not.

[Jon K]

Yaofeng - its not gas temperature I am talking about - its materials. The cooler you keep the head, the less likely it will lead to detonation. 165 - 185 is a great number for producing torque. Hotter running engines (as you see as years get later and later) are for emissions compliance. A hotter combustion event makes more power, but it requires a cooler running cooling system to keep it in check. The temperature of your combustion can be very high and have tons of btu behind it, but if your cylinder head and coolant are running at over 240F average, you're turning liquid into gaseous pockets (hurting cooling) and making the motor exponentially more sensitive to detonation.

[bubba966]

These are only the temps the stats start to open. So that prompts two questions:
1. When are they fully open and do they open at the same speed?
2. What is the operating temp of the engine when its warmed up fully?
If the answer to 2 is greater than 95-and I rather suspect it is - what difference does it make? Its function is to get the engine to operating temp. Once its done that it plays no part. Its a low tech item so do I really believe it does what it says on the tin? Maybe not.

A stat doesn't open and stay open. It'll open and close depending upon how much heat the engine is producing versus how much heat the colling system is dissapating.

Now, you might be in a situation as to where the engine is producing enough heat that the coolant doesn't get below 95C thus keeping the stat open at all times. Or you might be in a situation where your cooling system can maintain 90C, but the stat keeps closing when the coolant gets cool enough, then opening again when it gets back up to 95C+. And it continues that constant cycling. But if it had an 85C stat and the cooling system could keep the coolant at around 90C then the stat would stay open and you wouldn't get the hot/cold cycling. And the constant heat cycling isn't good for the longevity of the engine or cooling system, not to mention it'd make the power output less consistent.

Sure, those kinds of differences in power output and longevity are small.

But, BMW did put a lower temp stat in the M60's to begin with as we were reminded earlier in the thread and only changed over to the 95C stat to combat the Nikasil problem.

So, I'll be putting the 85C stat in at some point as I've got an Alusil block that's amazingly clean burning. And Replacing my rad with a Zoinsville all aluminum rad that will dissapate heat a bit better and have a 65% larger coolant capacity. The larger capacity and better heat dissapation of the Zionsville will be able to keep the coolant at a lower operating temp. And a lower coolant temp should work better with a lower opening temp stat.

It's probably not worth the extra $ to most people (to install an 85C stat and Zionsville rad instead of 95C stat & Behr rad). But I do like a good torque curve. And anything I can do to improve that while I'm replacing worn out parts I'll be doing. Because as nice as a well running chipped M60B40 is, it still doesn't put out enough power IMO...

[Jon K]

Most thermo stats stay open for the most part, its just a matter of how far.