Air Conditioning load
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Elder User
Joined: Nov 2015
Posts: 545
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From: Bedford, Va
Air Conditioning load
I was driving yesterday in a 94 degree urban environment with a passenger. The van's title weight plus riders and equipment was a little over 6,000lbs and she has 120K miles on her. The road heat kept my exterior thermometer at 106 and the radiator fan clutch held on on until 2,500 RPM and it took moderate throttle for the EFI 302 and 4R70 automatic to keep pace with the traffic. The FTE Vin decoder says I have a 2.73 rear end but other sources state it's a 3.27 or 3.31. On cooler days it's pretty peppy for a brick powered by a small block. I might mention it recently had a tuneup up that really improved things.
My main question is, could the AC compressor and radiator fan load along with the heat make a vehicle seem so anemic? Or could the engine simply be too small? I'm in no position financially to change things making this a rhetorical question. Simply curious.
My main question is, could the AC compressor and radiator fan load along with the heat make a vehicle seem so anemic? Or could the engine simply be too small? I'm in no position financially to change things making this a rhetorical question. Simply curious.
Posting Guru
Joined: Apr 2014
Posts: 2,196
Likes: 5
From: N Ca.
I was driving yesterday in a 94 degree urban environment with a passenger. The van's title weight plus riders and equipment was a little over 6,000lbs and she has 120K miles on her. The road heat kept my exterior thermometer at 106 and the radiator fan clutch held on on until 2,500 RPM and it took moderate throttle for the EFI 302 and 4R70 automatic to keep pace with the traffic. The FTE Vin decoder says I have a 2.73 rear end but other sources state it's a 3.27 or 3.31. On cooler days it's pretty peppy for a brick powered by a small block. I might mention it recently had a tuneup up that really improved things.
My main question is, could the AC compressor and radiator fan load along with the heat make a vehicle seem so anemic? Or could the engine simply be too small? I'm in no position financially to change things making this a rhetorical question. Simply curious.
My main question is, could the AC compressor and radiator fan load along with the heat make a vehicle seem so anemic? Or could the engine simply be too small? I'm in no position financially to change things making this a rhetorical question. Simply curious.
Logistics Pro
Joined: Oct 2014
Posts: 3,677
Likes: 172
i have read that older compressors can use up to 10hp while newer compressors can be 3 to 5hp. in my 88 i haven't really noticed the compressor kicking off and on while driving around but can tell when I am idling. I wonder if you could have some other issue that might be temperature related?
Mountain Pass
Joined: Oct 2014
Posts: 109
Likes: 25
On hot days especially in stop and go traffic, mine does this. My A/C system is overcharged, and my theory is that it takes more power to push the refrigerant through in that case. I don't have anything supporting this, but I do see that with mine too. And I have a 5.4.
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Elder User
Joined: Nov 2015
Posts: 545
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From: Bedford, Va
On hot days especially in stop and go traffic, mine does this. My A/C system is overcharged, and my theory is that it takes more power to push the refrigerant through in that case. I don't have anything supporting this, but I do see that with mine too. And I have a 5.4.
Lead Driver
Joined: Feb 2013
Posts: 5,006
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From: Roseville, MN
A 302 with only 3.31 gears (let alone 2.73) pushing a full size van with an overdrive trans is working pretty hard. Adding any load to it could be significant.
A lot of people would say that you shouldn't have anything taller than 4.10s with that setup. Personally I might prefer 3.55s. But if you think it feels pretty peppy normally, I'd just be glad it's not a complete dog all of the time.
A lot of people would say that you shouldn't have anything taller than 4.10s with that setup. Personally I might prefer 3.55s. But if you think it feels pretty peppy normally, I'd just be glad it's not a complete dog all of the time.
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Logistics Pro
Joined: Jul 2006
Posts: 4,512
Likes: 18
From: Detroit
I would check the axle code on the door sticker if that is still on the van(?) There will be an alphanumeric code and there are tables on this site and elsewhere on the Internet.
Many years ago I had an '86 GMC 2500 Turtle Top camper conversion with a carbureted 305 and a 2.73 rear end ratio. No overdrive. It was pathetic on any kind of hill and really sluggish around the city. I had the axle ratio changed to a 3.42 and it made a huge difference and I did not lose gas mileage, even on the road. In those old days, it seems like the mfrs geared vans to give them the best EPA mileage ratings and gave up driveability.
A 302 or 4.6 in a big van just ain't a lot of engine...and yes, the A/C and fan will use up horsepower. My '02 E150 had a 3.55 axle and I might have preferred a 3.73 for better performance when loaded.
Many years ago I had an '86 GMC 2500 Turtle Top camper conversion with a carbureted 305 and a 2.73 rear end ratio. No overdrive. It was pathetic on any kind of hill and really sluggish around the city. I had the axle ratio changed to a 3.42 and it made a huge difference and I did not lose gas mileage, even on the road. In those old days, it seems like the mfrs geared vans to give them the best EPA mileage ratings and gave up driveability.
A 302 or 4.6 in a big van just ain't a lot of engine...and yes, the A/C and fan will use up horsepower. My '02 E150 had a 3.55 axle and I might have preferred a 3.73 for better performance when loaded.
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