Lack of power in warm/hot weather. What is the cause?

[Shurup]

OK, as days bacame warmer and warmer, my X's power is worse and worse. I drive a lot - sometimes from the morning till 1-2 am in the morning and I can really tell that when I start it in the morning when the outside temp in not high, it runs strong. As sun rises, my truck starts loosing power. During the hottest time of the day my truck runs like $h1t. Then closer to the evening it is better again and couple hours after sun is gone it works perfect. In a winter time it was always fine.

My temp gauge never goes past the middle of the scale, so the engine temp is pretty much the same all the time.

I think that the problem is with the temp of the air comming into the engine. Is there any sensors in the truck that measure the air temp? Is there any ways to make the truck run strong no matter what the outside temp is? What can be the problem anyway?

 

[Buds007]

I guess I will chime in here, but others will most likely have to either correct or fine tune my answer. Your Xploder loses power because of the hot air. Hot air is less dense, therefore there is less oxygen in the air, therefore causing your engine to not be able to produce as much power as it normally does. Vice versa, cold air is much more dense, causing more oxygen to be in the air, producing more horsepower. That is why cold air intakes, and the like are very helpful in producing power. Hope this makes sense.

 

[Shurup]

Yes, that is what I was thinking. But I didn't think the loss would be that big - it is still 4.0L engine.

 

[Buds007]

Oh, its definetly feelable. I feel it real bad when it gets around 95. Otherwise, it isnt too bad. My engine sucks real hard when it gets warm though.

 

[rocket 5979]

Heck just to give you an idea of how bad it gets. My quarter miles times are significantly affected by the hotter it gets. My times of runs the same day and conditions but midnoon time and dusk or early night time usually are separated by as much as .3-.5 seconds in the quarter. That may not look like alot but it really is a HUGE difference. I notice that in the daytime i can just barely chirp second gear, but at night time i can squeal second gear no problem because i have morepower to do it.

 

[Alec]

I figure I lose about 1 hp for every degree between 60-90F, and about 2 for every degree above 90F.

 

[X~FACTOR]

Wow... and how do you figure that? Did you use some kind of scientific method?

 

[rocket 5979]

Originally posted by X-factor
Wow... and how do you figure that? Did you use some kind of scientific method?

Actually i learned the formula Alec used in motorbuilding class.

 

[rocket 5979]

..........................................................................................................................Well no not really

lol.

 

[GaSouthern1]

You ever get that blower put on Rocket?

 

[Alec]

Originally posted by X-factor
Wow... and how do you figure that? Did you use some kind of scientific method?

SOTP feel and track times.

 

[rocket 5979]

Originally posted by GaSouthern1
You ever get that blower put on Rocket?

Dan told me that i should be getting my Chip and injectors this coming week. So being that those are the last parts for the charger install it should not be too long after that and it will be in. I will be going on an op the middle of this month so hopefully i can install it before then. Either way the cam and 1.7 roller rockers are going in while i am away at the operation. So even if i dont get the charger in before i go i will at least be coming back to close to 300 horsepower. And then after the charger is in and tuned i will be seeing a little over 400 horsepower. So my prediction is mid 13's in the 1/4 by mid July. Then i might throw a little extra something into it to see if i cant get it in the 12's. But i might decide to hold off on that if i think i will have enough power to stop at 400 for a while. Otherwise if that much cannot hold me over and i need more then there is a little contingency plan in the works too. So to make my reply shorter. No i dont have it installed. YET. lol

 

[rocket 5979]

Originally posted by Alec
SOTP feel and track times.

Actually aside from being a smartass there is a scientific way to tell how much HP you lose in hotter weather. And like Alec said it does involve your longer Elapsed Times at the track. Then as long as you know your exact weight you can figure out how ,much time was lost and in turn figure out how much rwhp lost and how much fwhp too. lol. Though it wont be absolutely perfect it will be close enough where you could use it as a guideline.

 

[Shurup]

When there is about 80-90 degrees hot, my truck feels like it got only about 100 hp or even less.

I haven't noticed such big loss in power with any other cars I ever had.

 

[rocket 5979]

Got to take into account that our cars are much heavier too. So our power to weight ratio goes down exponentially when it get hotter, unlike other lighter cars.