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2017 Forester XT Touring CVT
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Discussion Starter #1
When driving my '17 Forester XT on the highway during the summer things get hot. I am talking about driving in 85-98 degree summer days. I have noticed that when driving above 85 and mostly keeping a pace of 90 the engine really heat soaks. The oil gets hot and the inter-cooler heat soaks. when all this happens the car pulls timing losing power, and starts hesitating with throttle input. sometimes the CVT will start acting funny delayed auto shifts.

I was looking at adding a thermostatically valved aux oil cooler, hoping to cool the block down better. keeping the engine happy and giving the engine oil an place to put heat. i thick this would greatly help with the CVT since the coolant takes heat out of engine oil and the coolant shares a radiator with the CVT.

But then i though would it be more effective to better cool the intake charge instead. i was looking at a air to water inter-cooler setup. i realized that driving at those speeds the TMIC can not handle the cooling load of the charge air too.

In a perfect world i would do both, since i think they would address shared issues. but im looking to one.

what do you guys think?

Thinking about it, does anyone agree that by cooling the intake charge better, thus allowing the engine to advance timing that im just going to run in to heating up the engine to much and then im back at removing heat from the engine?

Maybe my engine pulling timing is more related to high oil and block temps.
 

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2018 Fozie XT
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73 Posts
Similar car but 18XT. Got my tranny cooler to help with cvt already. I've been looking for the following to help with engine heat:

1. Turbo blanket to isolate heat and prevent soak into engine (decent price)
2. Heat wrap the air intake to help with heat soak from engine (my opinion, cheap hack)
3. Bigger intercooler but i find if car moving it will reduce heat at IC. Offroad may not be as much due to slow speed. (Can be pricey)
4. Bigger radiator: help cool engine oil (bit more pricey)

Love to hear from others on how to keep heat or hot engine in check.

Live in CA so trail ride in hot summer day seeing engine oil to 248F, coolant to 230F, and cvt to 210F (with tranny cooler) - steep hill ascent for good 35-45 min.
 

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2017 Forester XT Touring CVT
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236 Posts
Discussion Starter #3
I was thinking of the larger inter-cooler route. If you look at the price of new parts for 1200$ i get a way better system that drops after inter-cooler intake temps way more then air to air and is constant, i feel after enough heat a larger air to air will just heat soak again.

How did the aux CVT fluid cooler help with highway driving performance? like constant 85-90
 

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2016 Forester CVT
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180 Posts
@1roamingnome Do you have any data to support your heatsoak thesis? It could help you narrow down which parts will give you the most bang for the buck.
 

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2018 Fozie XT
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73 Posts
@1roamingnome Depend on outside weather. However on my 5 hrs drive to 4000ft at 65-75 mph with ambient at 70-85F,
My CVT with trans cooler stay at 192 top.

Around town now i see my cvt is <180F even with ambient at 95F.

Note: cvt temp is not the same on what u see on dashboard. You need obd reader and car scanner app on your phone.
 

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2018 Fozie XT
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73 Posts
@CoolMike I may have from running car scanner (auto logging) for past month. I know my ave engine bay has been increasing on hot day especially after i did some spirit driving on highway for 30 min or 1hr. (My commute)

I'm looking for the monitoring sensor within my obdscanner to read before, after IC. I already has monitoring at maf sensor to see the rise in intake air at maf.
 

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2017 Forester XT Touring CVT
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236 Posts
Discussion Starter #7
@1roamingnome Depend on outside weather. However on my 5 hrs drive to 4000ft at 65-75 mph with ambient at 70-85F,
My CVT with trans cooler stay at 192 top.

Around town now i see my cvt is <180F even with ambient at 95F.

Note: cvt temp is not the same on what u see on dashboard. You need obd reader and car scanner app on your phone.

Which reader and app do you use? I have been having a problem find one that reads tranny fluid temp and works with iphones.
 
2017 2.5i Fozy CVT
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1,283 Posts
Scangauge2 reads trans temp.
Few ?'s;
Premium fuel is bring used?
CVTgetting fresh fluid every 30000 miles?
Total miles on odo?
 

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2017 FXT
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82 Posts
All solid points here!
2. Heat wrap the air intake to help with heat soak from engine (my opinion, cheap hack)
I'd recommend heat wrapping the plastic charge air pipe instead of the air intake. The cooler charge air temp will help keep the IAT in check. Your air intake already has a duct drawing cold air in from the front of your FXT. The charge air pipe doesn't have as much ambient "cold" air hitting it.

3. Bigger intercooler but i find if car moving it will reduce heat at IC. Offroad may not be as much due to slow speed. (Can be pricey)
A cast aluminum end-tank and bar + plate core will more quickly dissipate heat once you start moving at a decent speed. It will also take longer to heat soak, but will then stay heat soaked a little longer if you stay at low speeds. It's a trade-off, but this mod will probably help the best with the timing being pulled.

4. Bigger radiator: help cool engine oil (bit more pricey)
The radiator does cool all of the important systems (CVT fluid, oil, and engine coolant), so a more thick, efficient radiator should help you maintain lower temperatures on all of the systems. There are also less things to "go wrong" once you start separating all of the systems with their own external coolers. The other item to balance is the geographic location where you drive. The liquid-to-liquid coolers (CVT and oil) use that coolant to bring each system up to temp faster, so if you live in a cold climate, it helps a lot.
 

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2017 Forester XT Touring CVT
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Discussion Starter #14
All solid points here!

I'd recommend heat wrapping the plastic charge air pipe instead of the air intake. The cooler charge air temp will help keep the IAT in check. Your air intake already has a duct drawing cold air in from the front of your FXT. The charge air pipe doesn't have as much ambient "cold" air hitting it.


A cast aluminum end-tank and bar + plate core will more quickly dissipate heat once you start moving at a decent speed. It will also take longer to heat soak, but will then stay heat soaked a little longer if you stay at low speeds. It's a trade-off, but this mod will probably help the best with the timing being pulled.


The radiator does cool all of the important systems (CVT fluid, oil, and engine coolant), so a more thick, efficient radiator should help you maintain lower temperatures on all of the systems. There are also less things to "go wrong" once you start separating all of the systems with their own external coolers. The other item to balance is the geographic location where you drive. The liquid-to-liquid coolers (CVT and oil) use that coolant to bring each system up to temp faster, so if you live in a cold climate, it helps a lot.
Great advice but im not looking to push out the Heat Soak or get more time out of the intercooler before it heat soaks i want to eliminate it.
 

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2012 SH Manual Diesel
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460 Posts
When driving my '17 Forester XT on the highway during the summer things get hot. I am talking about driving in 85-98 degree summer days. I have noticed that when driving above 85 and mostly keeping a pace of 90 the engine really heat soaks. The oil gets hot and the inter-cooler heat soaks. when all this happens the car pulls timing losing power, and starts hesitating with throttle input. sometimes the CVT will start acting funny delayed auto shifts.

I was looking at adding a thermostatically valved aux oil cooler, hoping to cool the block down better. keeping the engine happy and giving the engine oil an place to put heat. i thick this would greatly help with the CVT since the coolant takes heat out of engine oil and the coolant shares a radiator with the CVT.

But then i though would it be more effective to better cool the intake charge instead. i was looking at a air to water inter-cooler setup. i realized that driving at those speeds the TMIC can not handle the cooling load of the charge air too.

In a perfect world i would do both, since i think they would address shared issues. but im looking to one.

what do you guys think?

Thinking about it, does anyone agree that by cooling the intake charge better, thus allowing the engine to advance timing that im just going to run in to heating up the engine to much and then im back at removing heat from the engine?

Maybe my engine pulling timing is more related to high oil and block temps.
Have you considered a Radiator Fan Shroud?

I put a Mishimoto Fan Shroud (from a 08-14 WRX), and it is way more efficient at directing air (with fans off), than the stock plastic twin fan setup. My Rad fans now only come on when the A/C is on, and when they do, I can see the temp drop (via ODB2).

Also a fair amount of heat at intake manifold, maybe be due to EGR. I can watch the Intake temp change depending on whether the EGR is fully closed to when it is open. My car has a small heat exchanger (under Intercooler), but it’s probably not big enough, or could do with an air ducting pipe to cool it down, rather than relying solely on engine cooling system. Also heat shield between heat exchanger and Intercooler, to prevent heat soak.
 

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2017 Forester XT
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4 Posts
Example of a ScanGauge to monitor CVT temps. If I am running a light trailer or a few bodies and mountain bikers in the hot summer desert west, I keep this out to watch CVT temps. TFT = Trans Fluid Temp
522645
 

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2017 FXT
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82 Posts
Great advice but im not looking to push out the Heat Soak or get more time out of the intercooler before it heat soaks i want to eliminate it.
A TMIC will always heat soak, at some point. The FA20DIT is better than the EJ engines because the turbo is low mounted (compared to right under the TMIC), but heat will still rise. Most 15+ WRX/STI owners convert to FMIC because they are much less prone to heat soak. I'm not super familiar with any direct-fit kits for the 14-18 FXT, but I'm sure you could figure something out (piece together parts from a WRX kit).

Another further step could be an upgraded TMIC with water-meth injection. That has a whole new set of parts/pieces, so many people opt out of that if they are in a not-too-easy-to-service location (biking wilderness, etc.).
 

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2017 Forester 2.0XT Touring
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5 Posts
When driving my '17 Forester XT on the highway during the summer things get hot. I am talking about driving in 85-98 degree summer days. I have noticed that when driving above 85 and mostly keeping a pace of 90 the engine really heat soaks. The oil gets hot and the inter-cooler heat soaks. when all this happens the car pulls timing losing power, and starts hesitating with throttle input. sometimes the CVT will start acting funny delayed auto shifts.

I was looking at adding a thermostatically valved aux oil cooler, hoping to cool the block down better. keeping the engine happy and giving the engine oil an place to put heat. i thick this would greatly help with the CVT since the coolant takes heat out of engine oil and the coolant shares a radiator with the CVT.

But then i though would it be more effective to better cool the intake charge instead. i was looking at a air to water inter-cooler setup. i realized that driving at those speeds the TMIC can not handle the cooling load of the charge air too.

In a perfect world i would do both, since i think they would address shared issues. but im looking to one.

what do you guys think?

Thinking about it, does anyone agree that by cooling the intake charge better, thus allowing the engine to advance timing that im just going to run in to heating up the engine to much and then im back at removing heat from the engine?

Maybe my engine pulling timing is more related to high oil and block temps.
I am having similar issues with a '17 FXT that I bought over the Summer. So what direction did you decide to go??
 
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