Cool Weather HP Gains!

AustinPaul

AustinPaul

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Jan 18, 2020
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Location
Austin, TX
Wow, I've forgotten about my hotrods and Harleys in the Fall weather. Our TJs despite electronic fuel injection and ignition, (mine's an '05), are as still quite old school. As such, I can't believe the performance gains I get in cool, dense air, vs our usual brutally long and hot summers. Talk about feeling it in the ole butt dyno! Man! Our dog, my wife and I, along with my TJ, feel a new kick in the butt! Feel like it's never been as dramatic as this year. My newer Tundra, nor my wife's Grand Cherokee? I don't feel any differences. Their ECUs are so much more advanced.

Do you guys have the same experience with your TJs? 4.0s? I love it!

20200222_184351.jpg
 
Yes. It's very noticeable on my 05 LJR.

Turning the A/C on or off also makes a noticeable difference. The A/C probably accounts for much of the difference between hot vs cool weather performance here in NM. That said, every vehicle I've ever owned made noticeably more power in cooler weather.

Here, at roughly 5-6,000 feet elevation and hills/mountains in all directions, I'm down on power compared to those at lower, flatter locales. Any improvement is noticeable.
 
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I can relate to OP, when cold comes i always notice a difference, but would not call it a boost, more like Jeep is much easier to drive.
I think amount of wind is reduced around cold season, and it moves a bit above the road. Yesterday i was driving on highway, soft top was noisy as if there was a decent wind is blowing but it did not push Jeep around, i barely touched gas pedal to keep it at speed.
 
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AustinPaul said:
Wow, I've forgotten about my hotrods and Harleys in the Fall weather. Our TJs despite electronic fuel injection and ignition, (mine's an '05), are as still quite old school. As such, I can't believe the performance gains I get in cool, dense air, vs our usual brutally long and hot summers. Talk about feeling it in the ole butt dyno! Man! Our dog, my wife and I, along with my TJ, feel a new kick in the butt! Feel like it's never been as dramatic as this year. My newer Tundra, nor my wife's Grand Cherokee? I don't feel any differences. Their ECUs are so much more advanced.

Do you guys have the same experience with your TJs? 4.0s? I love it!

View attachment 374421
Click to expand...

It is definitely noticeable on my '06 LJ.
 
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g.hayduke said:
Yes. It's very noticeable on my 05 LJR.

Turning the A/C on or off also makes a noticeable difference. The A/C probably accounts for much of the difference between hot vs cool weather performance here in NM. That said, every vehicle I've ever owned made noticeably more power in cooler weather.

Here, at roughly 5-6,000 feet elevation and hills/mountains in all directions, I'm down on power compared to those at lower, flatter locales. Any improvement is noticeable.
Click to expand...

Oh, running the compressor is a HUGE drag on mine, especially with 33x12.50s. I'll sometimes flip it off if I'm going up a long grade.
 
Jerry Bransford said:
Your air intake sucks in the hot air located at the top of the hot engine compartment. Your engine isn't getting cold enough air to make a significant difference except perhaps from the placebo effect.
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Jerry, I know you know your TJs, and I should have added that I have one of those Spider Customs hood vents. But, yep, it's a very noticeable difference that a dyno would support.
 
AustinPaul said:
I should have added that I have one of those Spider Customs hood vents. But, yep, it's a very noticeable difference that a dyno would support.
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Is that Spider custom hood vent, poison? Post the live dyno data please. I tried to tell everyone my Jeep has 20 extra HP when it's below zero outside, because it's sucking the cold air through my proven "Tornado" system. If I leave the hood open when I drive, it increases by 7 hp more but it's hard to drive with the hood leaning on the windshield frame. Prove them wrong, then send your results to mrblaine to confirm it. :geek:
p.s. I didn't tag @mrblaine because I know better. Oops!

tornadoair (2017_11_20 00_38_12 UTC).jpg
 
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I have noticed a difference every year I’ve had my 97 4.0 tj. Very noticeable. Mainly when on the highway when going up specific (decently sized) hills… summertime 90 deg I’ll have to almost floor it to keep 65-70mph (no one else in jeep and doors/top off) , this time of year with hardtop and hard full doors on I barely have to modulate the throttle on the same hill.

Edited: why I have been wanting to do the windstar intake mod for a while…
 
Jerry Bransford said:
Your air intake sucks in the hot air located at the top of the hot engine compartment. Your engine isn't getting cold enough air to make a significant difference except perhaps from the placebo effect.
Click to expand...

holy shit, better tell Chrysler, think of all the money they've wasted on IAT sensors in the past 30 years!

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if moving, underhood temp is hell of a lot cooler with air entering the radiator at 40 than at 100.
 
TheBoogieman said:
Post the live data please.
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That's not going to happen. I've got a sense of where we're headed here. Cool dense air is a well known hp adder. That's undeniable. As I'm sure most of you know, the ecu will pull or add timing per the parameters it's working with, like altitude, bad gas, temp, knock sensors, throttle position, etc.

In terms of my Jeep, I've never done anything to enhance the performance of it. The hood vent was installed by the previous owner, and I'm very glad to have it given the heat we get here, especially for crawling.

I'm just sharing something fun based on 'my' experience that actually caught me off guard. Pulling grades and hills on familiar roads in higher gears (6sp), not bogging down, better gas mileage.

Now let's move on to a forum favorite, like synthetic vs regular OIL, or that running 93 octane add hp! 🇺🇸
 
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freedom_in_4low said:
holy shit, better tell Chrysler, think of all the money they've wasted on IAT sensors in the past 30 years!

View attachment 374508

if moving, underhood temp is hell of a lot cooler with air entering the radiator at 40 than at 100.
Click to expand...

Should I slow down now to lower my temps? My top speed is 97 mph anyway. :(
 
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AustinPaul said:
That's not going to happen. I've got a sense of where we're headed here. Cool dense air is a well known hp adder. That's undeniable. As I'm sure most of you know, the ecu will pull or add timing per the parameters it's working with, like altitude, bad gas, temp, knock sensors, throttle position, etc.

In terms of my Jeep, I've never done anything to enhance the performance of it. The hood vent was installed by the previous owner, and I'm very glad to have it given the heat we get here, especially for crawling.

I'm just sharing something fun based on 'my' experience that actually caught me off guard. Pulling grades and hills on familiar roads in higher gears (6sp), not bogging down, better gas mileage.

Now let's move on to a forum favorite, like synthetic vs regular OIL, or that running 93 octane add hp! 🇺🇸
Click to expand...
I was just having fun with you. My Jeep is in the shop and I'm bored. 🤫
 
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AustinPaul said:
That's not going to happen. I've got a sense of where we're headed here. Cool dense air is a well known hp adder. That's undeniable. As I'm sure most of you know, the ecu will pull or add timing per the parameters it's working with, like altitude, bad gas, temp, knock sensors, throttle position, etc.

In terms of my Jeep, I've never done anything to enhance the performance of it. The hood vent was installed by the previous owner, and I'm very glad to have it given the heat we get here, especially for crawling.

I'm just sharing something fun based on 'my' experience that actually caught me off guard. Pulling grades and hills on familiar roads in higher gears (6sp), not bogging down, better gas mileage.

Now let's move on to a forum favorite, like synthetic vs regular OIL, or that running 93 octane add hp! 🇺🇸
Click to expand...

It's just forum nonsense. Somehow the accepted knowledge that cold air intakes don't add performance gets turned into "air temp doesn't impact engine performance", which defies physics and ignores that the reason aftermarket intakes don't do anything worthwhile on a TJ has nothing to do with the properties of air at different temperatures.
 
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I guess we could ask someone if installing the windstar mod seemed to help theirs… specifically if they are in hot weather. Anyone know someone to tag for comment with hot weather+windstar?
 
DWR said:
I have noticed a difference every year I’ve had my 97 4.0 tj. Very noticeable. Mainly when on the highway when going up specific (decently sized) hills… summertime 90 deg I’ll have to almost floor it to keep 65-70mph (no one else in jeep and doors/top off) , this time of year with hardtop and hard full doors on I barely have to modulate the throttle on the same hill.

Edited: why I have been wanting to do the windstar intake mod for a while…
Click to expand...

👍
 
DWR said:
I guess we could ask someone if installing the windstar mod seemed to help theirs… specifically if they are in hot weather. Anyone know someone to tag for comment with hot weather+windstar?
Click to expand...

nope.
 
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