Does anyone know how much horsepower is used when the AC is on assuming 90 degree temp.? I have an 06 V8. I can feel my engine give a slight "bump" of some sort periodically when the AC goes on and off. If it's an 85 degree day I usually set my temp at 75 or so. I am wondering how much hp I gain if i'm going up a hill and turn off the AC or otherwise want maximum performance?
AC horsepower loss
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wilsoncwil
New member
I don't know how much hp you lose with the AC on but based on my experiences it seems like a lot. When driving through the desert heat to Vegas I almost have to step on the gas all the way to the floor just to merge onto the freeway or trying to pass when going uphill. Under normal conditions my 4Runner never has to huff and puff like that.
I know everyone in here praises how much power the V8s have but I sure don't notice it in these conditions.
I know everyone in here praises how much power the V8s have but I sure don't notice it in these conditions.
KnightFire
New member
wilsoncwil said:
I'm sure it had more to do with elevation than with your A/C. Actually using A/C doesn't consume THAT much HP in the grand scheme of things.
It also doesn't rob you of any time loss at the the track (1 second loss comment, which would be a MASSIVE loss), A/C compressors shut down when your go WOT. Of course when racing you want to turn off all accessories anyhow...
HAGO
The only loss in HP I feel is when the fan is engaged all the time because its too hot. Usually this happens with the A/C on. You will know when its engaged because the 4Runner transforms into a giant vacuum sounding beast. You will also feel like you lost 50 HP also. The only time I have my fan kick on full time is when I'm driving in traffic, or around the city and its about 90 out and the car has been running for a while. So the loss in HP can be attributed to the engine sucking in super-hot intake air too. Usually, the fan will kick off and the performance will increase when you drive at highway speeds for a couple minutes.
As far as a cold start (relative term) and putting the A/C on while driving at highway speeds; for example if the car was sitting out in the sun all morning but hasn't been started, so its hot in the car but the engine is cold, I don't notice ANY appreciable difference in performance with the A/C on until the entire engine, coolant, intake air gets hot enough to engage the fan clutch...
As far as a cold start (relative term) and putting the A/C on while driving at highway speeds; for example if the car was sitting out in the sun all morning but hasn't been started, so its hot in the car but the engine is cold, I don't notice ANY appreciable difference in performance with the A/C on until the entire engine, coolant, intake air gets hot enough to engage the fan clutch...
KnightFire
New member
Bill3508 said:
It's an absolute proven fact that you lose 1 Second off your ET time in the 1/4 if your A/C is turned on?
Please state your source of this factual data.
I've drag raced for a very long time, and I've known guys that forgot to turn off their A/C at the lights...(while I never recommend using it while staging in the 1st place)...regardless, their times were FAR from a FULL SECOND off their normal pace.
You do realize just how HUGE a difference a full second is in the 1/4...right?
Absolutely. I've seen it time and again and have done pass runs in various cars with it on and off. My factual data is only real world experience backed by timeslips. Also depends on the car your running. Heavier cars that do not have lots of horsepower are hurt worse by it than lighters cars. I've also seen that V8's tend to strugle more with the AC problem than turbo's 4 or a 6 cylinder. For example a 1996 Impala SS, running 13.56 without air would run 14.76 with the air on at the start. I've know about WOT cutoff but there is enough delay to cause lag, and its not the same for every vehicle.
This is my experience and thats all I can give. Its also fun to see the time sheets on cars raced in cool to mid temps and then run them on a high temp day. Its sad to see the times go up when your car ran so well earlier that morning.
Bill3508
This is my experience and thats all I can give. Its also fun to see the time sheets on cars raced in cool to mid temps and then run them on a high temp day. Its sad to see the times go up when your car ran so well earlier that morning.
Bill3508
KnightFire
New member
Bill3508 said:
WOW! I'm not calling you out or stating that your data is faulty, but your numbers have me amazed!
ET/HP Calcs on a 1996 SS (~4300 lbs) running a 13.56ET is around 341RWHP (nice numbers for an LT1 Impy BTW), while the same car doing it 14.76ET is only netting 264RWHP. Thats a difference of ~77RWHP!!!! My numbers would be more accurate, but I only used the data you provided...
Were these back to back runs? With the same DA, same 60' times, and same car???
I just find it incredibly hard to believe that the AC compressor was sapping away 77RWHP. I've been drag racing the SAME LT1 power plant (as stated in your SS Impy times) in my 1993 Formula for 12 years...and have watched others do the same...I've never seen that kind of reduction in power due to a simple accessory being turned on...there would have to be massive issues somewhere else contributing to that kind of loss. Don't ya think?
The times I spoke of at the track where the fellow club members (4th Gen F-body Club) had forgotten to turn off their A/C in the lanes, their times were only off by .2-.3 ET...
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Thats the only way I remembered it as it was a large difference. There were 3 runs and that was the worst of the 3 numbers with the AC on. The other 2 runs were in the .75 to .95 range if I remember. I've also got two dyno runs somewhere on a 98 Camaro with the AC on and off, but I don't know if I can find them or not, so I won't guess on the HP numbers. I haven't raced in about 6 years, but it was interesting keeping data for things like AC and making runs according to temperature by spacing them out by 10 degrees per run as the day progressed.
I don't recall the 60' times and there wasn't any issue with the car, just the AC putting a strain on the engine. These runs were with the same car. The only other times I saw time losses like that were running in cold/cooler weather, and then having to make a run late in the day with temps in the high 90's.
I attempted to make a intake tube for the Impala that was water encased and would freeze them for dyno and 1/4 runs just for running in the heat, but it still made very little difference with the air that hot as it still did not have time to cool.
Bill3508
I don't recall the 60' times and there wasn't any issue with the car, just the AC putting a strain on the engine. These runs were with the same car. The only other times I saw time losses like that were running in cold/cooler weather, and then having to make a run late in the day with temps in the high 90's.
I attempted to make a intake tube for the Impala that was water encased and would freeze them for dyno and 1/4 runs just for running in the heat, but it still made very little difference with the air that hot as it still did not have time to cool.
Bill3508
Mr. Lambdebois
New member
I'm glad other have noticed this as well.....
Any time its over 90 and the a/c is running I have a signifigant reduction in power. It is way more than any other V8 vehicle I have owned. Comparing it to two different v8 explorers and several mustangs and cobras I barely even notice the power loss when running the a/c on them in 90+ degree temps at least compared to the 4runner with the v-8.
also this is at 700ft to sea level
As a side note when you go to WOT or wide open throttle the A/c compressor should shut off.... not saying it still doesn't slow you down
Any time its over 90 and the a/c is running I have a signifigant reduction in power. It is way more than any other V8 vehicle I have owned. Comparing it to two different v8 explorers and several mustangs and cobras I barely even notice the power loss when running the a/c on them in 90+ degree temps at least compared to the 4runner with the v-8.
also this is at 700ft to sea level
As a side note when you go to WOT or wide open throttle the A/c compressor should shut off.... not saying it still doesn't slow you down
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KnightFire
New member
Bill3508 said:
Pretty significant actually, on mine if I run back to back several times and heat soak the entire motor, I see losses of up to .3 in my ET.
Of course the DA factor and ambient temps play a HUGE role in those times as well...
HAGO!
wilsoncwil
New member
If I lived in Vegas or Arizona I definitely would not purchase a V8 4Runner, they are way underpowered in the heat.
