Reduced Power in High Temps.
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Senior Member
Joined: Mar 2002
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From: SW MO.
Reduced Power in High Temps.
I know that warm weather will *slightly* affect power output of any engine. But a couple days ago we had a 70 degree day. First one in several months. I noticed my truck not running nearly as strong as normal. I tested one hill today (mid 30's again). I could gain speed at 70 without unlocking torque converter. In the 70 degree heat, I had to shift down a gear to sustain speed. And take another to gain. Very pronounced difference here. I know there a bulletin out on this but I couldn't find it on our bulletin search. I beleive it is a pcm reburn. Anyone know for sure what vehicles are affected? How much does ford charge for a reburn? I don't think the tuner can affect this in any way, can it? I am always running Conoco 93.
Former Sponsor
Joined: Mar 1998
Posts: 13,385
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From: Virginia
Hi S&B,
Actually, you're probably not going to find a factory PCM program change that is going to do very much for you about this specific issue. It's really more of a physics issue primarily, as opposed to an actual tuning deficit.
What's happening to cause your loss of pwoer in warmer temps is 2 things.....................first, the normal difference in air density and thus the actual number of molecules of oxygen that are getting into the combustion chamber............ Cooler air is denser, thus you can (and have to) burn more fuel, hence more power is made.
Second, add to that the fact that in these vehicles (and most other computer controlled powertrains as well), the amount of spark advance (timing) is tied to several things, like ECT (engine coolant temperature), etc., but most importantly in this case, it's tied to IAT (inlet air temperature) as well.
The "centerpoint" is 77 degrees F, above that the PCM reduces timing to control detonation in warmer weather, below that it adds timing to compensate for the colder inlet air temps. This is precisely why most computer controlled vehicles will have more problems with detonation in the winter than in the summer, just the opposite of what most of us grew up with. It used to be that summertime was the season we had the most detonation in, but not anymore, it's the exact opposite, expecially with vehicles that have significant power gains & supercharged engines, etc.
The difference between temps in the mid-70's & temps in the mid 30's (about 40 degrees) will make a 15-20 horsepower or even more difference in your power output, easily enough to make the difference of whether or not it needs to downshift to maintain velocity up a grade, etc.
This issue of colder air being denser & thus more fuel is burned so more power is made has *always* been with us of course, that's basic physics. Now we have to add to that the additional factor of timing being tied to IAT, and you can easily have as much as a 30+ horsepower difference between the power a given vehicle will make in summer heat versus what they make in winter conditions.
The only thing you can really do about this in practical terms is simply to do more modifications that will add more power, so you'll have more power *all* the time, until you get to the point that you can go up the grade without a downshift even in summer. You've already got a much better powertrain program than anything Ford provides, so the answer isnt' there, it's in finding another 20 or so HP & appropriate increases in torque so you can stay in the higher gear longer, basically.
Give us a call to go over any of this in more detail, go over appropriate mods, etc.
Good luck!
Actually, you're probably not going to find a factory PCM program change that is going to do very much for you about this specific issue. It's really more of a physics issue primarily, as opposed to an actual tuning deficit.
What's happening to cause your loss of pwoer in warmer temps is 2 things.....................first, the normal difference in air density and thus the actual number of molecules of oxygen that are getting into the combustion chamber............ Cooler air is denser, thus you can (and have to) burn more fuel, hence more power is made.
Second, add to that the fact that in these vehicles (and most other computer controlled powertrains as well), the amount of spark advance (timing) is tied to several things, like ECT (engine coolant temperature), etc., but most importantly in this case, it's tied to IAT (inlet air temperature) as well.
The "centerpoint" is 77 degrees F, above that the PCM reduces timing to control detonation in warmer weather, below that it adds timing to compensate for the colder inlet air temps. This is precisely why most computer controlled vehicles will have more problems with detonation in the winter than in the summer, just the opposite of what most of us grew up with. It used to be that summertime was the season we had the most detonation in, but not anymore, it's the exact opposite, expecially with vehicles that have significant power gains & supercharged engines, etc.
The difference between temps in the mid-70's & temps in the mid 30's (about 40 degrees) will make a 15-20 horsepower or even more difference in your power output, easily enough to make the difference of whether or not it needs to downshift to maintain velocity up a grade, etc.
This issue of colder air being denser & thus more fuel is burned so more power is made has *always* been with us of course, that's basic physics. Now we have to add to that the additional factor of timing being tied to IAT, and you can easily have as much as a 30+ horsepower difference between the power a given vehicle will make in summer heat versus what they make in winter conditions.
The only thing you can really do about this in practical terms is simply to do more modifications that will add more power, so you'll have more power *all* the time, until you get to the point that you can go up the grade without a downshift even in summer. You've already got a much better powertrain program than anything Ford provides, so the answer isnt' there, it's in finding another 20 or so HP & appropriate increases in torque so you can stay in the higher gear longer, basically.
Give us a call to go over any of this in more detail, go over appropriate mods, etc.
Good luck!
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Senior Member
Joined: Mar 2002
Posts: 333
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From: SW MO.
Thanks for the info Mike. I didn't realize that temps would affect power that much. So my condition is normal. Maybe my magnaflow will come quicker than I origionally thought. And my AF1.
Former Sponsor
Joined: Mar 1998
Posts: 13,385
Likes: 4
From: Virginia
Hi S&B,
You're very welcome of course, as always.
Yes, it can be surprising just how much power is lost to warmer temperatures, especially in computer-controlled vehicles. Of course, we also tend to forget jsut how much power we're getting out of today's much smaller engines, too, and just how much weight & load we';re asking them to cope with.
Back in the 60's & 70's, we'd never think of doig any real towing with anything less than a 460 cu. in Ford V8 under the hood of an F-150, and that's how many of those trucks were sold, with the bigest engine they made available, in classis American style.
Today the biggest motor we can get in the F-150 is a 260 HP 5.4 (which will thankfully be bumped up to 300-305 HP for 2004), so we certainly need some help to haul around these 2.5-3 ton trucks with these smaller engines. Luckily the aftermarket has done a good job of getting us parts to raise power well & maintain reliability, etc.
You mention waiting on an AF1 & Magnaflow exhaust, & forgive me for asking, but in the interests of providing the best possible service, are you waiting on those parts ordered from us here at Performance? I ask only because if so, if you'd like to give us a call with your name & address we're shipping the order to, we'll be happy to get your tracking numbers for your shipments if you like, so you'll know exactly when your products will arrive.
Have fun,
You're very welcome of course, as always.
Yes, it can be surprising just how much power is lost to warmer temperatures, especially in computer-controlled vehicles. Of course, we also tend to forget jsut how much power we're getting out of today's much smaller engines, too, and just how much weight & load we';re asking them to cope with.
Back in the 60's & 70's, we'd never think of doig any real towing with anything less than a 460 cu. in Ford V8 under the hood of an F-150, and that's how many of those trucks were sold, with the bigest engine they made available, in classis American style.
Today the biggest motor we can get in the F-150 is a 260 HP 5.4 (which will thankfully be bumped up to 300-305 HP for 2004), so we certainly need some help to haul around these 2.5-3 ton trucks with these smaller engines. Luckily the aftermarket has done a good job of getting us parts to raise power well & maintain reliability, etc.You mention waiting on an AF1 & Magnaflow exhaust, & forgive me for asking, but in the interests of providing the best possible service, are you waiting on those parts ordered from us here at Performance? I ask only because if so, if you'd like to give us a call with your name & address we're shipping the order to, we'll be happy to get your tracking numbers for your shipments if you like, so you'll know exactly when your products will arrive.
Have fun,