88°C thermostat thoughts

[jicaino]

That's great info all...thanks for all of that and sorry OP for cranking on your thread. I like that idea of the 88 not having a plug so it opens on water temp alone. Seems like you all have stated that this 88 will have a trickle down effect to lower temps in the motor oil so the only other factor is the MAF...so the combination is quite important and should be to have cold air and cooler oil...what a concept:-)

The side effect on the MAF Is less heat soak. Not much of a difference on the road, but in stop and go without the clutch fan and with the 88°C tstat intake air temps are way cooler.

[angeleye540i]

And it trickles down to the MAF too, motor surrounded by 35F lower temp coolant less heat radiates / convects to MAF , = faster in every condition... Altho it is behind the radiTor so there are many variables... Working clutch fan, AC, car soeed and momentum of travel/trip

[Kenny1958]

I am running the same stat as Hozy. Works great. My car lit up CEL so I had to add the resistor. Some seem to throw a CEL and some not.

I also left my stat unplugged when i installed the 88 stat but it does show a map cooling error in inpa. I'd like to do the same as you have done Chris, how do i do it ?

[philly98540]

Just connect a 12 ohm resistor rated for at least 25 watts.

I used a 10 ohm 100 watt, but some say a 12 ohm more closely matches. I hacked an old connection off an old stat but you can just splice in.

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[geargrinder]

I have the resistor, done in a fairly elaborate bulletproof manner, and I have found over long term, I still get occasional code. No CEL, just a code.

Based on all the anecdotes and my own experience I am now hypothesizing that there's 2 logic checks. The one for an open circuit (code from being disconnected) we know for sure is there. But I am also suspecting there's some kind of other logical check. Like maybe a check to see if temp changes when the circuit is triggered, or an 'absolute' temperature check under particular not-highly-frequent occasions / circumstances. If it doesn't see the proper temp or change on trigger it may also throw that same code. I think this is what happens when you have the resistor but get the occasional code.

Seems like it might be that situation is triggered by longer WOT's which would be when the factory triggers the wax pellet. If I piddle around town for days w/o getting on it, it seems I don't get that code, so that WOT connection seems likely - it could be at extended WOT when the wax pellet is supposed to be triggered, it actually checks for an absolute temperature range being achieved, and then finds the engine too cool already, and thinks the MAP has failed.

All hypotheses on my part but that's my current thinkin.

[jicaino]

It's been several months rocking the 88°C tstat here. It takes the worrying away for me. The car's always well behaved, way cooler than it was (sheet metal, cabin, radiant heat under the hood, etc)

I've even installed back the clutch fan I had (a 530i unit) for the AC on hot summer days doing stop and go, and I can't even tell it's there. That's how little I've worried about the car since I installed the 88°C tstat. I haven't even think about operating temps, triple checked everything, and so on.

Before, it felt like a boiler close to exploding. Plus the car got quirky under really hot weather and such. I was always considering temperature, what kind of driving I was going to be up for (traffic, etc) Now I just happily hop in no matter what and I'm with my mind occupied at what I'm doing, not the car behavior.

Heck, it's running so fine that I have my really expensive Wizard Cooling radiator and haven't installed since I don't feel there's the need for improved cooling system efficiency now.

[geargrinder]

Just connect a 12 ohm resistor rated for at least 25 watts.

And actually that's overkill since max wattage dissipation is going to be more like 13-14W (assuming your voltage ran high) so anything 12-20W is probably fine - although indeed if you're sourcing at RatShack or other retail where choice is low, 25W is a common value.

The advantage of a lower wattage handling is just packaging - smaller part takes up less space in tucking it away - but the 25W has zero downside otherwise. "overkilling it" might help if you were running them constant-load, but none of these will ever heat up to any notable degree at all since the duty time is so short on activation... I would be willing to bet even a 10W will probably work fine and not burn up from my experience (I've used a lot of power resistors like these in Audio work where I load them heavily and constantly w/ a big power amp and that's a different story) since the rating is for constant duty, and they can take short periods of over-load for sure.

Here's a Mouser search for anything in that general ohm range (I think the OEM part is labeled 11.2ohm inside or something like that) and 15-20W power handling.

http://www.mouser.com/Passive-Compon...z0wn12Z1z0wo4t

[Uturn540]

I just did a long WOT run yesterday on the way home. I also have the 88c thermostat and 10ohm 25watt resistor with no clutch fan. I will check for codes on mine this evening to see if the WOT affected mine. I like not having the clutch fan just for the fact there is less stress on the WP bearings, but it is going to get hot soon so I will be watching temps. The plus is I live in the sticks so very little stop and go traffic.

[geargrinder]

I"ve driven mine through several summers and triple-digit temps w/ AC on as well as driving it from Mass to Florida and back (granted not in the summer...) and have the supercharger installed, and zero issues running just on the electrical fan, per Randy's long time advocacy. Front of engine access and visibility is so much easier without it there too.

[JimLev]

Here's one for you guys that don't have an account at Mouser.
https://www.amazon.com/uxcell-Alumin...2+ohm+resistor
Free shipping too.
I have my resistor tucked down in the front of the engine, not visible.
GG, I know Randy was a big proponent of no clutch fan or an electrical replacement fan, BUT if the Aux fan fails your screwed.

[philly98540]

JC, I bet your right on the code caused when dme expects results and does not get them. Odd some never get the code though. Maybe Some variations In the dme's?

I suggest 25 watt min to be safe. It's hot underhood already and if the dme malfunctions and sends continuous voltage to the resistor, it could go way hot. Not likely, bUT ship happens.

Jim, I still got beauty cover so putting up top is good for me. That resistor you posted looks ideal.

[geargrinder]

Here's one for you guys that don't have an account at Mouser.
https://www.amazon.com/uxcell-Alumin...2+ohm+resistor
Free shipping too.
I have my resistor tucked down in the front of the engine, not visible.
GG, I know Randy was a big proponent of no clutch fan or an electrical replacement fan, BUT if the Aux fan fails your screwed.

Yeah Jim these days Mouser lets anybody order - same as any web order - no major account setup required.

Sure on the Aux fan, but, there's lots of things that if they fail I'm screwed (throttle body for one!) and it's not exactly completely screwed... it's situationally dependent. In cool weather where your miles to home were all highway, you'd be fine. 100F and traffic lights? Yeah. Yer'd be forked up the chute (well at least sitting on side of road for 10 minutes for every 3 minutes of driving or something...)

It is true I've been thinking of proactively replacing my Aux fan, but I don't sweat it that much. Its surprising how little it runs, which is why so many cars (here's one of Randy's arguments...) these days only come from the factory with 1 electrical fan system anyway. Because mostly they are reliable enough that they are fine.

[computiNATEor]

Yeah Jim these days Mouser lets anybody order - same as any web order - no major account setup required.

Sure on the Aux fan, but, there's lots of things that if they fail I'm screwed (throttle body for one!) and it's not exactly completely screwed... it's situationally dependent. In cool weather where your miles to home were all highway, you'd be fine. 100F and traffic lights? Yeah. Yer'd be forked up the chute (well at least sitting on side of road for 10 minutes for every 3 minutes of driving or something...)

It is true I've been thinking of proactively replacing my Aux fan, but I don't sweat it that much. Its surprising how little it runs, which is why so many cars (here's one of Randy's arguments...) these days only come from the factory with 1 electrical fan system anyway. Because mostly they are reliable enough that they are fine.

It's funny, but with the coolant temperature lowered to 88ºC on my old 530i, the aux fan hardly ever ran except for when the AC was on. On my new 530i, without the adjusted thermostat, it runs a lot more, even with a new fan clutch.

[jicaino]

I don't know about your cars, but on mine, the resistor could be a .5w one. It's just polled by the DME to see if it's there. It never tries to actuate the MAP cooling, just checks for it much like cold monitoring on the lights.

[geargrinder]

I thought same thing originally J, but from observation I think the DME might actuate the MAP "regardless of temperature" under prolonged WOT. At least thats my working hypothesis, which I am still waiting to be able to proof...

[jicaino]

I thought same thing originally J, but from observation I think the DME might actuate the MAP "regardless of temperature" under prolonged WOT. At least thats my working hypothesis, which I am still waiting to be able to proof...

I've never really observed it while driving hard for obvious reasons. I measured it statically, it gets polled every now and then, but sets a code only if you scan with a comprehensive tool that checks all the sensors, not just stored codes.

I stuck a 10 ohms .5w resistor in the plug when I measured it and forgot about it. Last sunday while taking care of doing 4 helicoils, I took the strut bar and engine cover off, snapped the manifold P/N and checked it. Still in place, no signs of overheating or anything, and certainly still operational. I've done plenty of driving since I installed the 88°C tstat, and it's not been very civil maneered but haven't done silly butt WOT driving as I used too... I just drove fast and spirited but in an old(er) gents kind of way, you know.

[fullthrottle540]

Just heard about this for the first time. Where are you getting these 88C thermostats?

It's made the old BMW diesel motors

[geargrinder]

Not that old. At least no older than our cars, which is why its the newer snap-fitting style hose connect.

It's from E38 & E65 740D's w/ the M67 engine.

http://www.realoem.com/bmw/enUS/partxref?q=11512248542

[ThePhantom!]

Hi JimLev, very late to the party here but curious if you'd be kind enough to assist me in determining if the BMW 1000 ohm resistor (part #13901734469) would work with the 88C thermostat swap (from the stock 105C)? I am doing the thermostat swap now on my 03 540i and am curious if this resistor is sufficient to use as a plug in with the plug for the stock electronic thermostat?

[JimLev]

^_I used a 12 ohm 25w metal resistor, like this.
https://www.amazon.com/uxcell-Alumin...-3&tag=mh0b-20

A 1Kohm may work and not give you a code, I never tried it.