Optimum ambient temp for ICE?

[seftonde]

All,

Just curious, does anyone know what the optimum ambient temperature for internal combustion engine operations? I realize it depends on other factors as well, just looking for a guideline - assume standard pressure (sea level), etc.

Many thanks!
Daniel



Mods: 351 Cleveland V8

[SomervillePrius]

I find my Prius gives me the best gas milage in the 50+ to 75+ range. Under 40 it seems to run a different warm-up program and above 85 it has to use quite a bit of compressed air.

Hope that helps

[alexstarfire]

Compressed air? For the AC, or what? I've still got most of my insulation blocking the front grill and it's hit 90F out here in Atlanta already. I haven't seen any problems with heat, but to be fair I almost never drive it more than 30 minutes at a time, so that could be it.

Could be that I've got the older model, but the higher the temps the better it's been for me. Even now when it's over 80F almost every day, sometimes when I'm coasting for a while it'll still have to turn the ICE on to keep stuff warm. Not sure why, since I don't coast THAT long, not even a mile.

[efusco]

Lots of variables....
Ideally if you could start out at about 180F then transition to around 70F after the entire warm-up routine of Stage I is complete I think that would be the best balance. Barring the 180F I still like temps in the low to mid 70s as it provides the best balance of good operating temps for the ICE and good driver comfort without the need to use the AC.

[philmcneal]

70 DEGREE C and 90 degree C is the sweet spot for engine efficency, when your engine climbs above 92 degrees C the engine coolant or water pump kicks in to provide adequete cooling to knock the temperature back down to 86 degrees C and the cycle continues. Everytime you need to cool down the engine that's a conversion lost (aka mpg loss) (from engine to water pump vice versa) so try not to overheat your engine

i'm sure there's a number of times the water pump can operate before being extinguished... but i'm sure that number has to equal 100,000 miles before changing the engine coolant again.

I usually try to keep it at 1500 rpm when coolant reaches 70 degrees C ( stage 4) to prevent any additional heat from reaching the engine, although in the end heat is going to get there no matter what, at least when your soft with the rpm the heat is just isn't as intense and during your trips in EV mode the engine will get a chance to cooldown without the aid of the water pump, saving efficency losses!

[JimN]

Daniel, I believe the car runs better (higher mpg) with OAT (Outside Air Temp) in the high 60's. In the evening with temps in the 80's-90's it takes a lot longer to get the mpg back up.

<div class='quotetop'>QUOTE(JimN @ Jun 8 2007, 08:31 PM) [snapback]458410[/snapback]</div>

Daniel, I believe the car runs better (higher mpg) with OAT (Outside Air Temp) in the high 60's. In the evening with temps in the 80's-90's it takes a lot longer to get the mpg back up.
[/b]

BTW, the insulation for the upper grill went back in place.

[ken1784]

Japanese hypermilers are saying 35C (95F) intake air temp is the best.

Ken@Japan

[abq sfr]

<div class='quotetop'>QUOTE(ken1784 @ Jun 8 2007, 08:00 PM) [snapback]458432[/snapback]</div>

Japanese hypermilers are saying 35C (95F) intake air temp is the best.

Ken@Japan
[/b]

It gets to 95F in Japan? How serious are the Japanese Hypermilers, do they drive when 95F with windows rolled up and AC off to get the best mpg?

[ken1784]

<div class='quotetop'>QUOTE(abq sfr @ Jun 9 2007, 01:02 PM) [snapback]458504[/snapback]</div>

It gets to 95F in Japan?[/b]

Sure!
But, please note that it is an intake air temp.
We block upper grill and two thirds of lowe grill even in summer to keep the engine room warm.

How serious are the Japanese Hypermilers, do they drive when 95F with windows rolled up and AC off to get the best mpg? [/b]

The real Japanese hypermilers never use AC and never drive on highway.
http://www.cleanmpg.com/forums/articles/t-...-2006-1793.html

Ken@Japan

[diamondlarry]

<div class='quotetop'>QUOTE(ken1784 @ Jun 9 2007, 08:54 AM) [snapback]458602[/snapback]</div>

Sure!
But, please note that it is an intake air temp.
We block upper grill and two thirds of lowe grill even in summer to keep the engine room warm.
The real Japanese hypermilers never use AC and never drive on highway.
http://www.cleanmpg.com/forums/articles/t-...-2006-1793.html

Ken@Japan
[/b]

I have a question related to this: What is the warmest that you should let the engine's coolant temp get to when blocking off the grill? I'm picking up some pipe insulation material today and am planning on doing the grill block. Thanks.