I don't really know for sure, but I'd heard that turning on the AC in a car requires power for the compressor, which leeches power to the wheels. Estimates go up to 20-30 hp lost.

Do you find yourself not turning on the AC b/c it bogs down your car? I do. The difference is extremely obvious to me between AC on and off, and I've repeatedly passed the "blind test" with passengers testing me

I wonder how parasitic the compressor is in the RX8, and on the flipside, I wonder how Canzoomer's mod increases the car's performance. The gains from the piggyback ECU mod are supposed to be relatively subtle to the passenger, but I wonder if the off-set is as much as the AC compressor. If so, I think it'd definitely be worth it.

Thoughts?

 

yank the f*cker out!!!!! If I did not live in the jungle I would first thing!!!!

 

I turn off the AC when I know I'm going to need power (or more importantly don't want hesitation). This afternoon it was crossing 3 lanes of traffic to get from a side road to an expressway on-ramp...from a dead stop. That said, it (the AC) is not nearly as noticable in the RX-8 as it is in a 4-banger. The impact, IMHO, is somewhere less than in a V6 and more than in a V8.

 

I have a 944S and the diff between ac being off vs on was significant. In the RX-8 I don't think it's nearly as significant, but I'm sure it does make a difference. I'm here in hot sweaty Florida weather right now, so I've yet to do much in the way of testing.

 

I haven't noticed much drop in power from the A/c since the CZ1.1 went in. BTW, the compressor turns off at WOT.

 

The compressor turns off at WOT?

I dare to ask....what's WOT? I can only assume you mean at stop or idle, because I've noticed it. In traffic, the AC doesn't do JACK. I was in traffic in 95 degree heat (100 on the road), and the AC didn't do anything but blow hot air until I got moving again.

Nothing like hot AC to make traffic that much more enjoyable.

The power loss from the compressor is just as noticable in the 8 as it was in my 1996 MX6. Basically, it feels like you're suddenly hauling another 500 lbs.

 

wot= wide open throttle. so when you drop the hammer the ac compressor turns off for extra power. i believe its cutoff is atsomething like 65% wot

 

The first car I drove didn't have the auto shutoff of the A/C at WOT - you had to turn it off manually. From the second car on, they have all had the automatic shutoff at idle and at WOT. BUT, and this is a big BUT, there was still a significant drag on the engine even when the compressor would shut off, with the system on - for whatever reason - and this I haven't noticed as much in the 8. Maybe other systems actually just lower the compressor instead of completely shutting it off?

 

Yep, at 65% throttle, the AC cuts off to free up power. Of course, from 0-65% it's still on, so you will feel some lag from a standstill. I believe it only stays off for like 5 or 10 seconds, even if you are still above 65%.

 

I'm almost sure that it doesn't rob the engine of 20-30 horsepower. That would be a huge difference, and the butt-o-meter would definitely notice. I don't really notice that big of a difference in my car (2002 Mazda Protege5) when the AC is running, but maybe it's more significant in the Rx-8.

 

I have a highlander v4 as well, and you can really notice the a/c in that. I mean your speed on the highway will drop 10mph if you turn the A/C on and don't adjust by pushing the gas down farther.

It is not as noticeable in the RX8, but I hardly ever use it even if it is. Weather here is regularly around 90, but opening the windows works just as well. I don't use the a/c mainly for gas milage. Windows down gives you better gas mileage than ac on.

 

I thought it was pretty much a given you get much better gas mileage with the AC than the windows, because the open windows create such a large amount of drag.

 

On my Civic I have definitely used the compressor to help me brake more quickly in turn lanes :D Having not driven an CZ1 8 yet, but having watched the video overlay comparison between stock and CZ1, I'd have to say that's about the degree of difference between AC and no AC on my civic.

 

I thought the reason the compressor turns off at WOT is to keep the compressor from overheating and to extend it's life.

 

hmm lemme see.

AC is cutr at 65% throttle for 5 seconds, I assume it will remain cut unless throttle reduces to under 65% i.e. AC does not restart untill throttle drops below 65%, and then only after 5 seconds.

And if I REALY want to hoon I can always manualy switch it off.

So whats the problem?

 

I thought it was just your everyday AC loathing. That or determining if the zoomer could offset it, in some fit of compromising rationalization.

I still probably wouldn't use it if I had an 8 with the zoomer mod, but I'm die-hard and don't use my A/C even in the summer rush hour. Something about drawing from the car even more when it's already heat-soaked and stressed....

As long as I can get away with the sweaty shirt at work coming back from the lunch hour...

 

I agree with some of you - I don't notice much of a difference at all with A/C on. That said, I always turn it off if I'm going to be passing someone on a 2 lane road. It's a habit I've developed over the years.

But in just normal driving, it doesn't seem to impact the RX-8 nearly as much as it did my '92 Miata or even my V6 Accord.

 

Hi, folks ... I've been lurking for a couple days, so here's my first official post.

If the AC compressor turns off, what is the lag time? In other words, when you hit 65% of WOT, how long (milliseconds, seconds?) does it take for the compressor to figure it out and shut itself off? I guess the flipside to that question is whether it's just faster to turn off the AC yourself if you know you're going to need some extra power (say when passing a slower moving car)?

Danny

 

With the A/C on the car felt weak to me. I turn mine off too when I want the extra power. I have a hill to climb to get to my house and I turn it off before going up the hill so that I don't feel the lag. Also turn it off so that it will blow out the moisture so I don't get mold growing in the A/C.

 

Well as long as your are not on the interstate with the windows down you get better mileage than with the ac. Tested it myself on the car, same shift point, same driving route.

 

A/C compressors use approx 5 HP or so... I've read this many times in various publications.

 

I suppose if you are accelerating lightly you're only using about 40 horsepower, so then the 5 horsepower would make a difference. I'm always annoyed at how the revs seem to drop quicker with it on so I sometimes turn it off if I'm doing a lot of shifting.

 

My lord, it only uses 5hp and makes THAT much difference? No wonder people put mods on their car to get that extra 5-10 hp, it's apparently huge.

I thought the butt dyno was no good below 10-15 hp?

 

Yeah I'm thinking that it zaps more than 5 hp. I actually noticed the biggest difference when the car is just starting out and at low rpms with the A/C on. The car almost seems to hesitate and not want to fly up on the rpms like it usually does leaving us in our weakest rpm range (the low end). It feels more like 20-30 hp to me.

 

Mazda's been cutting out the AC compressor under hard acceleration for years. I'm almost positive the 8's also cuts out at idle. For an illustration of the well-known inaccuracy of the butt dyno, just check how much better your car seems to run after you wash it. And even better after you wax it.