Cooling questions – seeing conflicting info

[IamFODI]

For these items…

1. Engine oil cooler
2. Main radiator
3. MTF cooler
4. PSF cooler

…Are there any aftermarket options that are proven to work better than good-condition stock coolers, assuming a stock engine bay and underpanels? If so, how much better?

I know credible people swear by do88 and CSF. But I’ve also seen posts (sometimes from the same people) suggesting there’s not much improvement to be had vs. stock. That lines up with my understanding of cooling system theory, i.e. bigger radiators won’t help much if airflow is the limiting factor, which it almost always is. So, it’s hard to know what to think.

I’ve also read that the oil diverter valve mod helps a little, and higher octane fuel can help fairly significantly. Bimmerworld also apparently likes to control oil temps with engine oil choice.

What else is out there that has a track record (pun intended) of improvement vs. just replacing everything with new OE?

[spammysammich]

Whatever brand radiator you choose, do88 or CSF etc will gain you the benefit of never having one of those bullshit plastic end tanks crack or the connector neck shatter while you’re trying to swap out hoses. Straight up F BMW plastic craptastic.

[Redd]

I don't think larger coolers will reduce peak temp much but they will give you a bit more time before hitting peak temp = more hot laps. They will also help temps drop quicker when you're taking a cool down lap.

[IamFODI]

Originally Posted by Redd

I don't think larger coolers will reduce peak temp much but they will give you a bit more time before hitting peak temp = more hot laps. They will also help temps drop quicker when you're taking a cool down lap.

Interesting.

Not sure the physics of faster cooldown but similar peak temps; I thought peak temp was basically an equilibrium between heat coming in and heat going out, so wouldn't faster heat shedding also mean lower peak temps? Maybe I'm missing something.

I guess taking longer to hit peak temp makes sense given more mass and more oil in the cooler itself, though. That alone would be enough to justify a purchase IMO, barring other problems. Hmmm....

[roastbeef]

do88 seems to be the best. for manual transmission cars, the cooler doesn't seem to be an issue, but go ahead and remove the cooler blockoff plate. look in the duct and you'll see it.

i run trackspec hood vents and they help a lot. i realize that a lot of people aren't willing to cut holes in their hoods; either for fear of aesthetics or water. (regular rain doesn't hurt anything in the engine bay, by the way).

i have recently been focusing on proper ventilation and ducting. simply put, air needs to be forced where you want it to go. this is done with proper ducting, and creating a low pressure zone behind the cooler (this is where hood vents help).
our main heat exchanger is ducted pretty good, but once you remove the a/c condenser, you create large gaps that air flows around and isn't forced through the cooling fins. i plugged these fins with some high temperature adhesive-backed weatherstripping.

i am currently working on the ducting for my do88 dct cooler and oem oil cooler. the do88 cooler ducting isn't terrible, but it can be improved. the oem oil cooler ducting is terrible...
there isn't much you can do about the ps cooler, besides maybe upgrade it and put a sweat band over the reservior cap.

a commonly ignored piece of cooling is the front felt undertray. it is lightweight, seals up the front end nicely, and helps create a low pressure zone for the oil cooler exit. this is one area where aftermarket panels have not been an improvement. make sure your front felt is in good working condition.

[IamFODI]

Originally Posted by roastbeef

do88 seems to be the best.

Yeah, that seems to be the prevailing opinion.

I was skeptical of their data showing better performance than stock, and I couldn't find any other apples-to-apples comparisons between their pieces and good-condition stock pieces. But they told me in an email that they never use old beaten-up stock radiators for their testing; if it's not in good shape, they replace it.

I guess I'll file this under "there's probably some benefit."

Originally Posted by roastbeef

for manual transmission cars, the cooler doesn't seem to be an issue, but go ahead and remove the cooler blockoff plate. look in the duct and you'll see it.

Will do. Thanks.

Any idea why that's in there in the first place? Usually it's to prevent overcooling, yeah? But AFAICT the pump is electronically controlled based on temp, so that can't be the reason...

Maybe they figure it wouldn't get enough flow in normal use without the blockoff?

Originally Posted by roastbeef

i run trackspec hood vents and they help a lot. i realize that a lot of people aren't willing to cut holes in their hoods; either for fear of aesthetics or water. (regular rain doesn't hurt anything in the engine bay, by the way).

What kinds of differences did you notice? Have you posted specifics about this already? Happy to look it up if so.

Any opinions between the center vent and the pair of side vents? Any idea if one is more effective than the other?

Originally Posted by roastbeef

a commonly ignored piece of cooling is the front felt undertray. it is lightweight, seals up the front end nicely, and helps create a low pressure zone for the oil cooler exit. this is one area where aftermarket panels have not been an improvement. make sure your front felt is in good working condition.

Agreed. Mine's in place and checked regularly. FCP Euro FTW here!

[tdott]

Since you are manual, I think the benefits of the upgraded oil/rad are going to be slight because the improvements are only slightly better/bigger. But in theory (baring quality issues, which we seem to be hearing more of lately) the solid aluminum end tanks should be more reliable than plastic.

Whereas the DCT cooler (same as MT Cooler but DCT runs way hotter) is where the biggest size difference is. The Do88 DCT/MT cooler is double the size and the ducting is bigger to account for it. But I don't think the MT really needs additional cooling, I'm sure it can't hurt if you are planning to do longer duration sessions.

If I was tracking a manual car, i'd probably just do an upgraded rad when it was time for replacement. Maybe the oil diverter valve (if not driven in cold climate) & oil cooler if you really wanted to.

[IamFODI]

Originally Posted by tdott

But in theory (baring quality issues, which we seem to be hearing more of lately) the solid aluminum end tanks should be more reliable than plastic.

I've heard of this with CSF. Have you heard of it with do88?

Originally Posted by tdott

But I don't think the MT really needs additional cooling, I'm sure it can't hurt if you are planning to do longer duration sessions.

Roger that.

Originally Posted by tdott

If I was tracking a manual car, i'd probably just do an upgraded rad when it was time for replacement. Maybe the oil diverter valve (if not driven in cold climate) & oil cooler if you really wanted to.

Oil temps are the ones I'm most concerned about.

My fantasy is to be able to hammer the car on track for arbitrarily long sessions without oil temp getting far above the 3/4 mark on the gauge, even in 100º ambient temp. Seems like a significant ask from what I can tell, but at least I'm not fast; I'm on endurance-200 tires in the stock sizes, and my powertrain is 100% stock, so not as demanding as a lot of people's cars here.

[tdott]

Originally Posted by IamFODI

Oil temps are the ones I'm most concerned about.

I friend with a 6MT that runs similar times as me, usually doesn't have oil temp issues. But we also don't run long sessions. He is on stock cooling system. His interior is stripped so he is lighter than my full interior dct car.

Here is a vid of his, this was in cooler temps (87) and it only hit around 260:

This was a time trial event, so we usually only do about 3-5 laps a session, I'm sure if he kept going temps would have crept up, but compared to my DCT I would have been above 280 already.

[tsk94]

I think the cooling package as a whole is what's most effective. Oil temps affect water temp and visa versa. I'd suggest doing radiator and oil cooler at the same time.

I don't think the power steering cooler is necessary, more so some type of overflow/catch can for the stock reservoir. Even though I've done them on my car, I've also used a stock cooler for a long period of time as well (with the other coolers installed).

DCT cooler is 100% a good idea for tracking these cars. I'd also suggest an upgraded pan and the Bimmerworld overflow kit. I've had no issues with transmission overheating or missing shifts on hot days/long sessions with all these upgrades on mine. I know of someone else that tracks one of these locally as well - with no upgrades he has overheating issues, I don't.
For a manual car, meh.

I had the full CSF kit on my manual race car, and it worked good. I now have the full do88 setup on my current DCT track car, and I'm happy with it.
Biggest difference I found was how the do88 parts fit compared to CSF. Much better fit and finish. They do cost more, so I guess you get what you pay for...

[tdott]

Originally Posted by IamFODI

I've heard of this with CSF. Have you heard of it with do88?

You'll need to search but I think I remember a handful of ppl mentioning recent do88 quality issues, like this one:
https://www.m3post.com/forums/showth...=do88+radiator

Prior to 2020 when I got my coolers, do88 quality was top notch.

[okusa]

Originally Posted by IamFODI

Oil temps are the ones I'm most concerned about.

My fantasy is to be able to hammer the car on track for arbitrarily long sessions without oil temp getting far above the 3/4 mark on the gauge, even in 100º ambient temp. Seems like a significant ask from what I can tell, but at least I'm not fast; I'm on endurance-200 tires in the stock sizes, and my powertrain is 100% stock, so not as demanding as a lot of people's cars here.

Buy a P car

[IamFODI]

Originally Posted by tdott

I friend with a 6MT that runs similar times as me, usually doesn't have oil temp issues. But we also don't run long sessions. He is on stock cooling system. His interior is stripped so he is lighter than my full interior dct car.

Here is a vid of his, this was in cooler temps (87) and it only hit around 260:

This was a time trial event, so we usually only do about 3-5 laps a session, I'm sure if he kept going temps would have crept up, but compared to my DCT I would have been above 280 already.

In high-80s ambient temps, I can go 10-15 mins before the oil temp gauge is between the 3/4 mark and max. I know people regularly run that high or more, but I'd rather have a bit more buffer.

Originally Posted by tsk94

I think the cooling package as a whole is what's most effective. Oil temps affect water temp and visa versa. I'd suggest doing radiator and oil cooler at the same time.

Makes sense.

My coolers/radiators are all original at >171k miles, so probably due for a change. Normally my policy is to stick with OE unless there's very strong evidence that an aftermarket part will solve a problem I have and be worth the downside. Still trying to figure out if any aftermarket oil coolers clear that bar, but there are good looking options for the same or less money vs. OE (e.g. do88 at two-thirds the price), and I find it hard to imagine they'd be worse than stock or have a downside other than a little more weight. I guess technically they could obstruct air flow to the radiator a bit more, but feedback seems to suggest this isn't an issue. Hmmm...

Originally Posted by tdott

You'll need to search but I think I remember a handful of ppl mentioning recent do88 quality issues, like this one:
https://www.m3post.com/forums/showth...=do88+radiator

Oh wow. That's... not good. And very recent. Thanks for the heads-up.

Didn't know Litchfield made an oil cooler. They seem legit as a company. Might give that one a look.

[Redd]

Originally Posted by IamFODI

Normally my policy is to stick with OE unless there's very strong evidence that an aftermarket part will solve a problem I have and be worth the downside.

Yeah that's my concern too. There's really not many reliability issues with the stock cooling components. Haven't even heard many issues with plastic end tanks cracking. Aftermarket otoh I keep seeing leaks, poor fitment etc. That's the main reason I'm still on all stock coolers. I just do some cooldown laps mid session to keep temps in check.

[DRLane]

OP a couple considerations given your hesitancy and intended track use case (running endurance tires under NA power).

Give the existing radiators a good compressed air cleaning, radiator power wash, and straighten the fins with a comb where necessary.

Ensure the under tray is in good condition and the OEM gurney for oil exit is intact.

Switch radiator to >90% water with water wetter for the season. I say 90% so as to make it super simple to run a repeated drain / refill and use a temp tester to get reasonable accuracy of the mixture. End of season, dump a gallon of concentrate in with a drain and you’re likely more than square for sub-freezing temps.

Invest in high quality oil (Motul 300V, Redline, etc) and just change it every couple track weekends. They can all easily and safely sustain whatever temps you’re generating with NA power / street tire laps. Let the ECU pull power if needed. Hammer it until then

Lastly, the temp gauge I believe is a combo (oil/coolant). Get a CAN enabled data logger to get more accurate oil and coolant individual temps.

If you wanted to invest in cooler upgrades, my recommendation:

1. Go straight to the oil diverter valve. It’s messy DIY but reasonably straightforward. Offers the most bang for your buck oil improvement. Just note the additional warmup time to get the oil to temp when it’s cold.
2. DO88 oil is great (old stock before the issues?) namely as it adds an additional liter of oil capacity.
3. CSF radiator is sufficiently nice if you want one.
4. PS cooler is useless. Save your money.

[IamFODI]

Originally Posted by Redd

Yeah that's my concern too. There's really not many reliability issues with the stock cooling components. Haven't even heard many issues with plastic end tanks cracking. Aftermarket otoh I keep seeing leaks, poor fitment etc.

Yep.

#AftermarketLife

Originally Posted by DRLane

OP a couple considerations given your hesitancy and intended track use case (running endurance tires under NA power).

Give the existing radiators a good compressed air cleaning, radiator power wash, and straighten the fins with a comb where necessary.

Ensure the under tray is in good condition and the OEM gurney for oil exit is intact.

Switch radiator to >90% water with water wetter for the season. I say 90% so as to make it super simple to run a repeated drain / refill and use a temp tester to get reasonable accuracy of the mixture. End of season, dump a gallon of concentrate in with a drain and you’re likely more than square for sub-freezing temps.

Invest in high quality oil (Motul 300V, Redline, etc) and just change it every couple track weekends. They can all easily and safely sustain whatever temps you’re generating with NA power / street tire laps. Let the ECU pull power if needed. Hammer it until then

Lastly, the temp gauge I believe is a combo (oil/coolant). Get a CAN enabled data logger to get more accurate oil and coolant individual temps.

If you wanted to invest in cooler upgrades, my recommendation:

1. Go straight to the oil diverter valve. It’s messy DIY but reasonably straightforward. Offers the most bang for your buck oil improvement. Just note the additional warmup time to get the oil to temp when it’s cold.
2. DO88 oil is great (old stock before the issues?) namely as it adds an additional liter of oil capacity.
3. CSF radiator is sufficiently nice if you want one.
4. PS cooler is useless. Save your money.

Thanks for all these suggestions. I know you've been around the block on this so it's good to hear from you.

Do you have a sense of how close to the limits the ECU will let things go before pulling power? I've read that bad things can start happening at ~300º F bulk oil temp (certain metal parts losing temper, greatly accelerated oil breakdown, heavily fuel diluted oil e.g. around the pistons flashing off, etc.) but I don't think the ECU pulls power before that point, does it?

Good to know I can cross the PSF cooler (and the MTF cooler) off my list. Simplifies things!

[DRLane]

Originally Posted by IamFODI

Thanks for all these suggestions. I know you've been around the block on this so it's good to hear from you.

Do you have a sense of how close to the limits the ECU will let things go before pulling power? I've read that bad things can start happening at ~300º F bulk oil temp (certain metal parts losing temper, greatly accelerated oil breakdown, heavily fuel diluted oil e.g. around the pistons flashing off, etc.) but I don't think the ECU pulls power before that point, does it?

Good to know I can cross the PSF cooler (and the MTF cooler) off my list. Simplifies things!

Sadly, my car hasn’t so much as gone around the block in a couple years. It’s in more parts than Beefs speed holes. But that’s the slow life with tiny kids at home.

Everyone that’s responded has been around this platform for a long time. Not much that hasnt been answered already across this forum, so definitely read up on some of the longer build threads (a la dogbone).

I think redline pulls back when oil exceeds 285° (guesstimate). Again, pretty safe for high quality oils. But there are plenty of engineers on the forum that will be better able to guide you there.

I just lean toward changing it more often. It’s $130 ish (15w50 redline 5 quart is $65) ever couple weekends and a cheap insurance.

Another option, that rarely done. Insulate the headers. Bringing under hood temps down is never a bad thing…

[IamFODI]

Originally Posted by DRLane

Sadly, my car hasn’t so much as gone around the block in a couple years. It’s in more parts than Beefs speed holes. But that’s the slow life with tiny kids at home.

🤣 I feel that, man. Congrats on the kids!

Originally Posted by DRLane

Another option, that rarely done. Insulate the headers. Bringing under hood temps down is never a bad thing…

I'd love to coat the headers internally. I wonder if I know anyone who could be trusted to do it right...

[DRLane]

Originally Posted by IamFODI

I'd love to coat the headers internally. I wonder if I know anyone who could be trusted to do it right...

I sent them off to get White Lightening ceramic coating, and then also doing the thermal wrap.

[Redd]

I've gone as high as 135C/275F oil and 112C/234F coolant without DME warnings. I wouldn't push any more past that tho. I have warnings set up on my aftermarket HUD so it's an immediate cooldown lap when I see those numbers. Strangely I've also never had DCT over temp before, even when I was running stock pan. I have a Slon pan now for reliability and the little bit of extra capacity.

[bigjae1976]

Originally Posted by IamFODI

I'd love to coat the headers internally. I wonder if I know anyone who could be trusted to do it right...

I swaintech coated my S54 headers in 2017. As far as I know, no coating is being shot out of the tail pipe. I've never bothered to peek inside. The exterior has some small areas that are flaking off but it looks like there is still another layer of coating underneath. Looks really ugly though, if appearance is a concern then I'd go a different direction.

I did notice a significant reduction in coolant temps when doing this, hood vents, and moving an aluminum expansion tank...remember - E46.

[IamFODI]

It looks like the OE engine oil cooler is a tube-and-fin design. Any chance someone here can confirm?

CSF and do88 use bar-and-plate construction.

I've only just started learning about this, but it looks like tube-and-fin is lighter and more efficient, while bar-and-plate is more durable and has more thermal inertia (on top of which the CSF and do88 coolers hold more oil – even more thermal inertia). So, assuming the OE engine oil cooler is indeed tube-and-fin, that might make sense of the observation that CSF and do88 engine oil coolers don't reduce peak temps but do take longer to hit those temps.

Litchfield's engine oil coolers for this car are apparently tube-and-fin, so they should be more efficient than do88's or CSF's. Shame they aren't available through FCP Euro for that sweet LRG!