Tested and Ready 70° and 75° Thermostat

[bigjae46]

No on almost everything you said. Those temps are only optimum for fuel efficiency and emmisions at cruise and light load which is the main goal of the OEMs. It is well known that lower coolant temperature makes more WOT power due to better knock resistance and improved VE due to increased charge density. Often you need to make changes to run colder to ensure proper mixtures, ignition timing, running clearances, and control friction losses due to potentially colder oil temps in certain conditions, so ideally you keep oil hot but colder coolant.

Aero on F1 cars trump just about everything so they are choosing to run hot due to running small radiators for aero reasons. It is simply a by product of conflicting requirements and the ultimate goal for lower lap times not more power and aero is king and higher priority

The whole running hotter thing makes zero sense. My car feels like trash when the coolant would get over 220f. Feels excellent at 170f. My top speed data backs this up. My lap times also support the engine runs better at when the coolant and oil temps are lower vs higher.

F1 cars generally trim cooling when they run higher speed tracks like Monza.

[Anri]

No on almost everything you said. Those temps are only optimum for fuel efficiency and emmisions at cruise and light load which is the main goal of the OEMs. It is well known that lower coolant temperature makes more WOT power due to better knock resistance and improved VE due to increased charge density. Often you need to make changes to run colder to ensure proper mixtures, ignition timing, running clearances, and control friction losses due to potentially colder oil temps in certain conditions, so ideally you keep oil hot but colder coolant.

Digger,


Spot on all of it Digger. When I did 55°C t-stat on
our track E46M3 alongside with larger radiator
70% distilled water and 30% coolant it did run
tight very torque and running at near the max
ignition it made big difference between the stock
system and after.

Absolutely yes on fuel economy. My E31 840Ci M62
at summer time in traffic on AC running temp 115°C
it does ping every singe time off traffic light, the T stat is
97°C, let alone the power drops like its 4cylinder....it
so bad..

Updated the T-Stat to 71°C and no
more pinging, soon the S62 is going
in but still felt did not want to destroy
the M62.

Bank-2 on inline-6 runs always hot.

On my S38 I have dual wide band on both
banks separate. Bank-2 always run little hotter
not by much than Bank-1 but my temps are in
the ~75°C

Another $2k and it will get me individual EGT
probes for my upcoming 4.0l S38 to be able
to monitor individually the EGTs and control
the ignition timing on each cylinder.


Regards,
Anri

[digger]

The best opearting temp for internal combustion engine is 90C to 120C due to material fatigue and design clearance. In theory, the higher opearting temp is better as less loss to combustion temp and pressure needed to push the pistons down. Cool air/fuel mixture is desirable but it should be treated separately from coolant temp.

So having a stable coolant temp at 85c or 90c is not bad, but when it continues to rise then it is bad.
Again, I don't think having the Tstat opens early at 70c is good, but a 70c Tstat inherently opens more than the stock Tstat at 90c, and this allows more coolant flow through the radiator - it's what one wants to prevent overheat on the track.

The ideal Tstat should not open until the coolant reached 90c, then continue to open more to keep the temp at 90c as the engine generating more heat. Unfortunately a classical spring loaded wax motor can't do this. Don't know why BMW didn't use an electric heater in the Tstat to control it as an "ideal Tstat" -- propably due to reliability issue.

F1 cars have coolant opearing temp at 120C.

No on almost everything you said. Those temps are only optimum for fuel efficiency and emmisions at cruise and light load which is the main goal of the OEMs. It is well known that lower coolant temperature makes more WOT power due to better knock resistance and improved VE due to increased charge density. Often you need to make changes to run colder to ensure proper mixtures, ignition timing, running clearances, and control friction losses due to potentially colder oil temps in certain conditions, so ideally you keep oil hot but colder coolant.

Aero on F1 cars trump just about everything so they are choosing to run hot due to running small radiators for aero reasons. It is simply a by product of conflicting requirements and the ultimate goal for lower lap times not more power and aero is king and higher priority

[Anri]

The best opearting temp for internal combustion engine is 90C to 120C due to material fatigue and design clearance.

Can you explain yourself in more deep technical details were did you
read this or come up with these numbers ?

If this is truth why all S engines do have T-stat at 79-80°C as opposite
of M54 or say my E31 840Ci M62 at 105°C with thermostat of 97°C?

Why BMW Motorsport made the 55°C on a car without AC condenser and
all nicely ducted up the front ?

F1 cars have coolant opearing temp at 120C.

And how does F1 engine starts from cold ?! with coolant heated
up to temps (I can find out asking Brian who is on F1 world) to be exact.

F1 internal clearance are design to operate in specific conditions and they
are only in hi revs.

Regards
Anri

[sapote]

The early opening and lower operating temp is desirable from a pure perfomance persective though assuing some adjustments. if you arent able to consisently operate at the t-stat temp or thereabouts on track then it's fairly pointless

The best opearting temp for internal combustion engine is 90C to 120C due to material fatigue and design clearance. In theory, the higher opearting temp is better as less loss to combustion temp and pressure needed to push the pistons down. Cool air/fuel mixture is desirable but it should be treated separately from coolant temp.


So having a stable coolant temp at 85c or 90c is not bad, but when it continues to rise then it is bad.
Again, I don't think having the Tstat opens early at 70c is good, but a 70c Tstat inherently opens more than the stock Tstat at 90c, and this allows more coolant flow through the radiator - it's what one wants to prevent overheat on the track.

The ideal Tstat should not open until the coolant reached 90c, then continue to open more to keep the temp at 90c as the engine generating more heat. Unfortunately a classical spring loaded wax motor can't do this. Don't know why BMW didn't use an electric heater in the Tstat to control it as an "ideal Tstat" -- propably due to reliability issue.

F1 cars have coolant opearing temp at 120C.

[Anri]

Gents,

To each to our won for sure on this one.
Not very constructive replies..

Inline 6 cylinder engine Cast Iron block
is waaaaay too long.

When the cooled water from the radiator
enters from the cylinder 1 it takes the heat
up to cylinder 3 aka Bank-1

Starting from Bank-2, 4-6, the water already
took the heat from Bank-1. Now Bank-2
has Hot water to work with and its no longer
cool when it entered the block.

Factory design water pump impeller and
pulley ratios are designed to work at 8000rpm
without making Cavitation, this is the concentration
I am sure we all agree on this one. Mechanical
pump are always concentrated to work at hi rpm
and low rpms are always compromised. (this is
were the Electrical water pump is priceless one
can adjust the flow at low speed to move the
water faster)

Lower range of RPM is compromised when
the water is slowed down tremendously and
thus why Bank-2 works always hot vs Bank-1

Obvious reason why BMW moved to step water
temp gauge starting from E32/E34. On the E24
E28 when the temp raised degree by degree I can see it
on the gauge..I can see when the clutch engages and
brings the temps down...isn't that obvious ? all the S54
cylinder head gaskets are always burned at Bank-2 okay
not talking about the ones that suffered damages
via detonation.

Why BMW put the EGT sensor on Bank-2 not Bank-1 ?
Bank-2 runs always hot

The Block Deck height on S54 is 217.5mm+/-
How come no one talks about that BMW Motorsport
raised the Floor by around 15-17mm ? (I have to look at my notes)
its to increase the rigidity in the main bearings
area by taking some space form the water bath.

On S38 at the same deck height of 217.5mm the water
bath is deeper down by those 15-17mm is what I am
comparing with so they did good on block from 1965
but went backward on 2000 engine block.

With connecting rod ratio of 1.52 the siamesed
bores do receive a lot of heat and with the combo
of 8000rpm for sure its Heat-Bomb

How come no one talks about that the EGT from
the headers which easily reaches ~850/~1000F/ 590°C or
so are located around no more than 1 finger away
from the block, fantastic, you have 900F radiant heat
going directly to the cast iron heat sponge.

I will provide very deep detail data on Jonathan's
freshly put S54 together, you will see.

Starting from Jonathans M3 I am including this in every
engine build.

All arguments and debates are all welcomed.

Regards,
Anri

[digger]

It's not the 70 Tstat early opening is desirable, but it opens more at operating temp when compared to stock Tstat is desirable.

The early opening and lower operating temp is desirable from a pure perfomance persective though assuing some adjustments. if you arent able to consisently operate at the t-stat temp or thereabouts on track then it's fairly pointless

[sapote]

Not sure I understand. Isn't the engine designed to be most efficient at 80 degrees? Willing to learn.

Yes for stock car for normal driving. On race track the AC condenser blocks some air, and the engine generates more heat, so a 70C Tstat would open more at 80C for more coolant flow to counter the higher generated heat.

It's not the 70 Tstat early opening is desirable, but it opens more at operating temp when compared to stock Tstat is desirable.

[nahvkolaj]

Not sure I understand. Isn't the engine designed to be most efficient at 80 degrees? Willing to learn.

[bigjae46]

I think for a track car with the AC removed and has a properly performing cooling system, I'd would recommend the stock 80 deg t-stat. My coolant temps bounce around 170 degrees so the t-stat is opening and closing.

But for a track car with AC...I think 70deg would work great.

[ChapterM3]

Doesn't surprise me one bit, can't wait to see what you've come up with Anri!

[simonnim]

Love it. Look forward to it.

[Anri]

Gents,

I added 75° options as well for Cold states.

The 70°-75° are all tested and it works great and no Check engine Light
is triggered so no need for adjustments in the ECU.

After many tests here is the data from the OEM spec:
At 80° Opens 1mm at 80°, 83°~3mm at 85° is fully open
Completely Closed at 77° +/-1°

70°. At 70° opens 1mm at 73° ~3mm at 75° fully open
Completely closed at 66° +/-1°

75° is right in between the OEM and the 70°.

$220 Shipped


Regards,
Anri.