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Less engine power with A/C turned on

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Old May 4, 2018 | 11:51 AM
  #1  
thanson90's Avatar
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Less engine power with A/C turned on

I did some searching but couldn't find much.

Stock 93 FD (48k miles) with stock ecu, the A/C works great, blows nice and cold.

Problem is that when I have the Air conditioning on the engine has less power. Its definitely noticeable that I have to give it more throtle and/or slip the clutch more to pull away from a stop. When I turn off the A/C the engine is fine. I know that A/C is going to load the engine a little bit but you shouldn't be able to notice it.

Any Ideas?
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Old May 4, 2018 | 12:21 PM
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I just recently got ac in mine and its very noticeable. Just posting to see if others have the same issue or if my compressor is just causing too much drag from being open to air for 23 years.
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Old May 4, 2018 | 01:11 PM
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Originally Posted by thanson90
... I know that A/C is going to load the engine a little bit but you shouldn't be able to notice it.

Any Ideas?
Who says? It’s been noticeable in every car I’ve ever owned. And the rotary isn't an engine famous for low-rpm torque, so the AC load is probable even more noticeable than most.
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Old May 4, 2018 | 01:26 PM
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Originally Posted by Sgtblue

Who says? It’s been noticeable in every car I’ve ever owned. And the rotary isn't an engine famous for low-rpm torque, so the AC load is probable even more noticeable than most.
Very interesting.....I’ve never noticed a difference even with low power economy cars but havet rode in any other fd’s before. Must just be a characteristic of the A/C in the rx7. I personally just hadn’t experienced that before soassumed it was a problem.

Good deal, one less thing to fix.

Thank You
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Old May 4, 2018 | 01:50 PM
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My stock '95 does it too.

The reason you are noticing it is because this car doesn't make much low end torque AND it doesn't have electronic throttle to mask it. Drive a 90s Civic and you will feel the same thing. Drive a modern low torque 4 cylinder (or an Rx-8 for that matter) and it's nowhere near as noticeable because both have electronic throttle. The electronic throttle compensates by requesting additional air to make more torque and overcome the parasitic drag of the A/C compressor. Since the throttle position is independent of the pedal position, you don't feel it nearly as much on an electronic throttle vehicle that has a good factory tune.
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Old May 4, 2018 | 01:53 PM
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Originally Posted by arghx
My stock '95 does it too.

The reason you are noticing it is because this car doesn't make much low end torque AND it doesn't have electronic throttle to mask it. Drive a 90s Civic and you will feel the same thing. Drive a modern low torque 4 cylinder (or an Rx-8 for that matter) and it's nowhere near as noticeable because both have electronic throttle. The electronic throttle compensates by requesting additional air to make more torque and overcome the parasitic drag of the A/C compressor. Since the throttle position is independent of the pedal position, you don't feel it nearly as much on an electronic throttle vehicle that has a good factory tune.
That makes perfect sense.

Thank You
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Old May 4, 2018 | 04:23 PM
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I agree with the low end torque. It's very noticeable off a dead stop and admittedly I'll sometimes choke the car when I forget the AC is on and the music is up.
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Old May 7, 2018 | 07:41 AM
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I've had the opposite experience.

I bought my '94 R2 with 68,000 miles on it near-stock and fully working R12 AC system. Blew ICE cold, like it would run you out of the car it was so cold.

The AC made ZERO difference when it was on. It didn't feel less responsive, bogged, anything, just totally felt normal.

Right now it still has R12 in it but the AC doesn't cool like it used to after I did the front mount. I think it's a combination of factors. The car doesn't get as cold, BUT the engine still doesn't bog or hesitate with the AC on.

Now, if you have too much oil in the compressor or have changed to 134a which many times has to be over-charged to get similar cooling, that can be a problem. That puts more work on the compressor and you feel it when driving.

I don't know about '95s that came factory with 134a, I've never driven or been around a 95 much to know.

Regardless, I'm not a fan of 134a in these cars. It will never get good and cold. Go with original R12 or dust-off, that's the way to go.

Dale
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Old May 7, 2018 | 09:03 AM
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Completely normal for a small, low torque engine. AC compressor kicks off at full throttle anyway so the ultimate power loss is negligible. However if its really bogging down the motor you might have another problem with the system such as a bad compressor or clutch, too much oil like Dale mentioned, etc.

Last edited by IRPerformance; May 7, 2018 at 09:06 AM.
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Old May 7, 2018 | 10:16 AM
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Yes, I noticed right away on my ~30k mile FD that the AC affected off idle power as you describe.

Then when I went to lightweight flywheel/dual plate clutch and it was even more noticeable.

Rotary is the weakest engine ever at idle/off idle rpm because of poor low rpm chamber sealing and very little rotating mass.
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