KrisA

I must be a "Princess and the Pea" kind of person, on EVERY car I've owned I can feel the drag that AC on causes. In modern cars that I've owned that show real time mileage you can see the mileage drop the second you turn on the AC. The Cayman is going to be affected more than most cars as it doesn't have a lot of low end torque. I only ever drive with AC on at high speeds, in the city I just open the windows and deal with the heat. If your car isn't affected by the energy required to run AC then you need to share your source of zero point energy with the world.

sectachrome

I agree. AC stays off unless I really need it. I can definitely tell a difference.

Matt(inMA)

5MT

XuTVJet

So I took the car out early yesterday evening. Temps in the low 80s and real muggy. I typically drive in Sport mode with the Sprint Booster in Sport setting 2. I had the HVAC in Auto at 70 degrees and let the car get full warmed and a bit heat soaked. I then switched the Sprint Booster off. The car was easier to take off more smoothly off the line and time the 1-2 and 2-3 shifts. I then turned the Sprint Booster back on and then it became more difficult to drive smoothly again. I then switched Sport mode off and left the Sprint Booster on. Again, the car was easier to drive. I even put the Sprint Booster in more aggressive throttle maps and it still drove pretty good. I turned Sport mode back on and the car went back to a less smooth driving experience. I then turned the A/C off, Sport mode on, and Sprint Booster on and she drove really great.

So, yeah, there's something going on regarding engine/throttle tuning with the A/C running, the car in Sport mode, and the Sprint Booster engaged. My car doesn't like it in that particular scenario. In steady state driving like the on the highway, there's no issue. It's when the motor is heat soaked and the car is in stop and go traffic does it become a bit annoying to drive smoothly. Given that I have a fairly rare combo of a 987.2 Base with a 6MT and Sport Chrono plus a Sprint Booster on top of it all (which I can't imagine there are many running around like this), it's no surprise to me that no one of these forums has experienced this.

I will say that even when running in the ideal throttle combo, I can still feel the A/C on. It's not nearly as obvious, but it does feel a little more laggy in the lower rpms and more in line with what I would have expected for a high strung, low torque small displacement 6 cylinder motor.

I do appreciate all the responses as it helped me think a bit more critically about what may be happening. It's just another case of an aftermarket part negatively affecting a certain driving situation.

XuTVJet

Totally agree. On my Stage 2 tuned 2016 BMW M235 6MT and my prior Stage 1 tuned 2012 WRX 5MT, I could feel when the A/C is on. Those motors are certainly more laggy in the lower rpms, especially when heat soaked. Turbos tend to be real laggy in the hot too. On my wife's 2020 4Runner, our 2015 Outback 3.6R, and all the rentals I drive for work, I can't tell any real difference with the A/C on or off. All those cars are autos.

With a manual tranny and the A/C compressor engaged, it puts a notable drag on accessories and gives the similar affect of increasing flywheel weight BUT without rotational inertia affect so it's harder to spin up the motor and with the constant drag, it then behaves like a lightened flywheel when you let off the gas thus the rpms drop faster when you're shifting. As such, you need to more aware of the throttle application. If you drive around all the time with the A/C on, well then, you obviously won't notice this effect as you're accustomed to it and don't know any different. When leaving the car in Auto, the A/C in these cars is running almost all the time, even in cooler temps, as the A/C is constantly managing temp and humidity. At least my Cayman and M235 behave like that.

Today's A/C systems are pretty efficient and only suck out about 2-5 hp, but that small power decrease doesn't account for the drag effect on manual transmission drivability. If you have an automatic, you're not going to notice anything because you're not in control of throttle/gear engagement.

Aussie skypig

The “Princess and the Pea” analogy.
I have a thicker mattress. A 3.8 “built for midrange” engine.
I didn’t say the car isn’t affected. I said I can’t feel it. I’m not claiming the AC compressor is magic. Just 1hp out of 350 isn’t noticeable. (But I can’t notice the extra drag in my Corolla or my Transit van either.)

RJ80

I know a lot of people like Sprint Boosters, but I just don’t understand installing a Chinese-built and designed product in these cars. Is the OEM Sport mode really not enough, especially on the street?

McSwine

I don't have sport mode so in my case, yes. But others that do that have said it improves their cars as well.

Julian_KCMO

Neither of my 987 BS or Base Cayman have had sport mode but if you have a manual trans 987, the electronic throttle interceptor (whatever brand) is 1000% the BEST upgrade, I don't think you will find a single person that has driven a car fitted with one that doesn't agree.

Back to the original discussion on the AC drivability, I've now been driving my 07 Base Cayman around for the last couple of days turning the AC on and off in various situations and yes, I believe I can pick up on a difference when pulling away from a stop. It doesn't feel as profound a difference as cool winter air vs summer humid air but is is different. Having said that, its not enough to bother me either. I think I'm just used to my Cayman being slow

Cheers,
Julian

XuTVJet

If it makes you feel any better, the Sprint Booster is made in Greece.

OEM Sport mode is a little better than normal mode, but it's nothing like the Sport vs Comfort throttle in my BMW. The Sprint Booster and others are great because you can tune them for linearity and aggressiveness. With a bit more throttle sensitivity, it is easier to rev match, downshift, etc. It also helps wake up the car and make it feel more lively. It is a must if you have a manual.

Dave in Chicago

I do notice a slight drag with the A/C on, but it’s not dramatic or impeding to clutch work.

It has been into the 90’s and humid here for many days. I happened to change my cabin air filter and immediately noticed the air at the vents was dramatically colder. Old filter didn't look terrible, but who knows?

Connected? Coincidence? …surely noticeable.

dmteter

2009 Base with 6MT. I don't notice any difference between when the AC is on or off. Obv YMMV.

RJ80

Fair enough, though some say the SB is actually made in Taiwan.

Do you now have to push two buttons (Sport, Sprint Booster) to get the desired effect every time you start the car? That is a non-starter to me for a more sensitive throttle.

XuTVJet

The Sprint Booster is on when you start the car.

XuTVJet

It may sound crazy, but check your accessory belt and see if it's a Porsche-branded one. There have been instances of aftermarket accessory belts causing misfires and false knock on 987/997/981 cars.