Mishimoto 169*F T-stat review

[acammer]

* * * 5/16/2022 update - I have abandoned these Mishimoto thermostats. I very much like the temperature ranges it operates at when working correctly - but I have had two fail. In both cases the rubber around the center sealing surface began to degrade, causing the thermostat an inability to close completely. This causes a delayed warm up, and overcooling under long decelerations. I'm back to the tried and true 160*F T-stat. When the car was bolt ons, this ran a bit too cool, but with the car cammed, it's a little less efficient in the lower cruising RPMs, and that elevates the temps to where it runs right around 180*F in cool air on the highway. * * *

I recently installed a Mishimoto 169*F (part# MMTS-VET-05) on my 2011 Camaro (mods in signature). It's important to note that my fan tuning is such that my low speed fans come on when the engine is started. If my coolant temperature exceeds 195*F, the high speed fans will come on (and stay on regardless of temps dropping back down). This was the previous owners tuner's setup. I would prefer to not run the fans all the time - more on that later.

I previous had been running a 160*F thermostat that the previous owner had installed in the car. I was pretty satisfied with the 160 stat, it would run right around 174-176 highway cruising, which was borderline too cool, but acceptable in my mind. The car would never exceed 185, even under prolonged idling in the heat. This was great at the drag-strip, I had very consistent performance even in high heat and long waits in the staging lanes.

When I changed the car to a 4.10 rear gear, my cruising RPMs rose from 1600rpm to 2000rpm at 75mph. This change as enough to bring my average running temperature at 75mph down to a steady 171. On a long downhill fuel-cut type of coasting I could see coolant temps dip down to 163. That's way too cool, in my opinion. The car was borderline on temps before, but with the increased rpm vs. vehicle speed, I was overcooling.

So, I went looking for a middle ground option on the T-stat between the 186 stock stat, and the 160 that I had in the car. I found the Lingenfelter 174 stat, but knowing that running temps are usually ~10-15 above t-stat ratings I felt that would have me running at 190+. Then, I stumbled on to the Mishimoto 169 T-stat. Thinking it should run right around 180-185 I picked it up.

I've had it in the car for about a week now, and at least 650 miles of mixed driving. At a constant 75mph cruise speed it runs right at 180-181 - perfect! Under real light driving, lots of coasting, I can still get the temps down to 176, which is what I consider the lower limit of acceptable. Under aggressive hill climbing (ie. low speed 1st and 2nd gear switch-backs - I ripped up Greylock Mountain Saturday) it stayed around 185 +/-2. Prolonged idling in 80+ ambient it'll creep up to 192-194, just below what it takes to kick my high speed fan on.

I do think I'm going to amend my tune to keep all fans off until 195, then run the high speed fan, then back to low speed at 192 with it staying on constantly in low (unless it goes back up to 195+) from there. Unfortunately, with the stock fan tables, that's about the best you can do. That way in daily driving it won't be running those fans at all, but if I do have a prolonged idle I will have aggressive cooling, and it'll bring it right back down nicely. I could have it come on low at 195 and high at 199, then back off at 192, but that's not aggressive enough to really take advantage of the stat. I really need to go to the custom HPTuners OS and get the better fan tables.

Overall, I think this is a heck of a find. It is pricey - I paid $48 on Amazon. But, it's the perfect middle ground between the 160 "little too cool" and 186 "stocks too hot". Obviously, the fan tuning helps keep things cool as well, a T-stat without fan tuning is not going to do a lot of good when you need it the most - controlling temps at slow speeds.

Some will say there is no proof that running too cool (to a point) has negative effects. Some will same that anything less than stock is trouble. The best I've ever seen this visually laid out is this:



Having the car a little cooler keeps me further away from the timing reduction tables for engine coolant and intake air temp. It makes for consistent performance at the drag-strip, staying cool in the lanes even with prolonged idle time. The intention is not to start a T-stat running temperature debate here - I'm just providing my opinion and what I found. I think this middle ground could be a solid choice for the guys that find a 160 runs just a little too cool for their liking.

[olblue75]

Are you still happy with the Thermostat purchase.

[blue-bayou]

By far one of the best (actually, the best) product reviews I have ever read. Very informative and illustrates product abilities and conditions of usage. Objective as well. Thank you for posting

[acammer]

Originally Posted by blue-bayou

By far one of the best (actually, the best) product reviews I have ever read. Very informative and illustrates product abilities and conditions of usage. Objective as well. Thank you for posting

Thanks! That's exactly what I was going for - objective and informative. It's a little lengthy, trying to ride the balance point between good detail and too long.

Originally Posted by olblue75

Are you still happy with the Thermostat purchase.

Yes, definitely. I've put some more time on the thermostat and I continue to be very pleased with it.

I have had the chance to drive the thermostat in some cooler weather now, and it continues to run right in the 178-180 range at 75mph, with ambient temps in the low 40's. Warm up continues to be as quick as ever, no changes there.

I did get my fan tuning sorted out, so now I have the fans off until 195, then the low comes on, with the high coming in at 203, and everything back off at 192. This works well with the car, the low speed fan is typically enough to knock it back down on a prolonged idle, and I'm not longer running the fans unnecessarily all the time.

I added a fan switch inside the car so that I can also choose to run my fans when I want. This is really only something useful for the drag-strip where you're trying to keep the car as cool as possible in the lanes. If I run the high speed fan and hold my rpms around 1500rpm I can cool the car down to 170 and below. It also circulates a lot of air through the engine compartment and helps keep things cool under there. And, I can run the fans with the engine off, to continue to circulate air after I shut down.

Still a product I strongly recommend, even at it's elevated price point.

[SSmitch]

Thanks for the information, I'm going to change my stock thermostat to this in the spring.

[olblue75]

Any news since winter and into the summer heat?

[acammer]

Originally Posted by olblue75

Any news since winter and into the summer heat?

Not really a lot additional to report. In the cool weather the car maintained a nice 178*F highway cruising. In the summer time it was running in the mid 180's most of the time, slipping up to mid 190's (where the fans come on) for prolonged idling. Rarely would it get over 200*F, and the fans would make quick work of it if it did.

Now, this spring I went to a 25% under-drive pulley and an aggressive camshaft. I do find the car running hotter with the under-drive, it likes to hang out right around 190*F when cruising, and bumps the fans on routinely when idling in hot ambient conditions (80*F+). I have considered going back to the 160*F T-stat, but I'm going to hold out until fall and see where it runs in cool weather. Really, it still rarely cross 200*F, so it's pretty reasonable still. And I can keep it nice and cool with the fan switch.

[xc_SS/RS]

Originally Posted by acammer

Not really a lot additional to report. In the cool weather the car maintained a nice 178*F highway cruising. In the summer time it was running in the mid 180's most of the time, slipping up to mid 190's (where the fans come on) for prolonged idling. Rarely would it get over 200*F, and the fans would make quick work of it if it did.

Now, this spring I went to a 25% under-drive pulley and an aggressive camshaft. I do find the car running hotter with the under-drive, it likes to hang out right around 190*F when cruising, and bumps the fans on routinely when idling in hot ambient conditions (80*F+). I have considered going back to the 160*F T-stat, but I'm going to hold out until fall and see where it runs in cool weather. Really, it still rarely cross 200*F, so it's pretty reasonable still. And I can keep it nice and cool with the fan switch.

Are you using EFI live or hp tuners?? Curious to see your fan temp table and compare it with mine since I've got a 160 degree tstat

[acammer]

Originally Posted by xc_SS/RS

Are you using EFI live or hp tuners?? Curious to see your fan temp table and compare it with mine since I've got a 160 degree tstat

HP Tuners - I'm pretty the Fan Desired % vs. ECT goes 192.2*F = 24, 195.8*F = 51, and 199.4*F =91. That should kick the low speed fan on at 196*F and off at 192*F. If you hit 199*F high speed will come on and run till it's back down to 192*F, then both fans will shut off. That's basically the most aggressive setup you can get while retaining a low/high/off functionality. You can tune them to simply be on low (or high) all the time, but that seems unnecessary.

[xc_SS/RS]

Originally Posted by acammer

HP Tuners - I'm pretty the Fan Desired % vs. ECT goes 192.2*F = 24, 195.8*F = 51, and 199.4*F =91. That should kick the low speed fan on at 196*F and off at 192*F. If you hit 199*F high speed will come on and run till it's back down to 192*F, then both fans will shut off. That's basically the most aggressive setup you can get while retaining a low/high/off functionality. You can tune them to simply be on low (or high) all the time, but that seems unnecessary.

nice! i'm going to give this a shot and see how it does. i don't know if i get a fan on at 196 currently but hopefully now i will with these settings

[acammer]

Originally Posted by xc_SS/RS

nice! i'm going to give this a shot and see how it does. i don't know if i get a fan on at 196 currently but hopefully now i will with these settings

A fan switch is always nice to have - I definitely like having mine for drag strip usage. I did a hot-wire article too if you ever want to just wire the fans to run with key-on.

[1JEWLDSSRS]

Thanks acammer for the info on this thermostat. Very good write up. I just ordered one for my 2011 SS that we just did a cam swap on and AFM/DOD delete and LS3 conversion and a 3200 stall. Folks I talked with said that the 160 would be too cool and you share this info, great stuff. Since the car is cammed it seems to have been running about 4-6 degrees warmer than before we cammed it. Had LT's and a custom dyno tune before the cam and the fan speeds have been tuned as well, so I'm hoping this thermostat will do the trick and bring my operating temps down some.. Thanks for sharing sir.

[acammer]

Originally Posted by 1JEWLDSSRS

Thanks acammer for the info on this thermostat. Very good write up. I just ordered one for my 2011 SS that we just did a cam swap on and AFM/DOD delete and LS3 conversion and a 3200 stall. Folks I talked with said that the 160 would be too cool and you share this info, great stuff. Since the car is cammed it seems to have been running about 4-6 degrees warmer than before we cammed it. Had LT's and a custom dyno tune before the cam and the fan speeds have been tuned as well, so I'm hoping this thermostat will do the trick and bring my operating temps down some.. Thanks for sharing sir.

I think you'll be pleased - it's a nice middle ground between stock and the 160*F. I've found the same, since installing the cam my car runs a good 6-8* warmer. That may be in part to adding the 25% under-drive in my case. A 160*F probably would be ok for my application now - but I'll hold judgement till I get to drive it in cooler weather again with the cam.

[xc_SS/RS]

Those fan settings work very well! Temps seem more stable now and I like that the fans don't come on full all of the time (they were set to kick on full at 199 last time but not halfway at 196)

The 160 works great with a 10% ati pulley in single digits temps. I have the 14-15 Hood vent too and ran with the rain tray installed all winter. Uninstalled I could tell it took a bit longer to warm up