[Greg Reid]

Maybe you can try it on the Dyno.

[Will]

Originally Posted by bird72

...
The best engine for performance and air conditioning seems like it would be a good HP big engine, because with that comes good torque. It seems a 500lb tq motor would be far less affected by AC drag than a 350 lb tq smaller engine. So would a linear X % parasitic loss be across board true? or a sliding scale of loss actually.....

No, it's not a %. It takes a certain amount of power to turn a given compressor design at a given RPM. That doesn't change no matter what engine you install that compressor on. If it takes 20 HP to turn the compressor at 4000 RPM then yes, the big inch, big power engine will see proportionally less loss than a smaller/weaker engine would.

I've never understood the across the board % power loss idea. Everything the engine turns takes a set amount of power to turn it and that doesn't change regardless of the engine doing the turning, so the % power loss from accessories and other drivetrain losses will be less on an engine that makes more power. This is why it's a bad idea to install a TH400 and a 12-bolt behind a lawnmower engine...

[6TEE8GTO]

Originally Posted by dwallace

Hey Guys,

As a former Drag Strip Owner, I urge you to NOT experiment with your times using and not using A/C on the strip. It's just not worth it, especially for the cars behind you. It's too hard to keep good traction on the track with Street Tired cars running, but, add the water, and you have a major accident waiting to happen, and best case scenario for the guys behind you, is they all have faulty ETs, that they can't explain. And believe me, when there is an accident or traction problem, the serious racers are going to check out the car that had just ran down that lane ahead of them.

It's an automatic expulsion at most tracks.

This.
We constantly have to make announcements over the PA reminding people to not run the AC while in the lanes, and if you enter the burnout box with water dripping, you will be sent right out the "breakdown chute" and not be allowed to make a pass. it's stupid and dangerous for the other racers as well as for yourself. Especially dangerous for bikes, as they tend to run a groove that is right where your AC condensate would drain to.
As far as other effects, while Greg is correct that at WOT the AC clutch is cut off, few people realize that with many EFI systems, especially Ford EEC-IV, the tune actually changes with AC active, small timing advance is cooked into the calibration... This has been debated and proven, and a racer's trick is to unplug the compressor clutch and have the AC switched on on a run. Some swear it can add 10 horsepower... Seriously... .

[njsteve]

Originally Posted by Will

N This is why it's a bad idea to install a TH400 and a 12-bolt behind a lawnmower engine...

So I should stick to the 6-speed and the Dana for my John Deer 185?
:-)

[Alvin]

Originally Posted by njsteve

So I should stick to the 6-speed and the Dana for my John Deer 185?
:-)

Check! And keep that A/C off when you race that green monster!

[Transporter]

Not to mention that I think some of the old time magazine tests also ran a VERY loose alt. belt/power steering belts for the same reason.

[6TEE8GTO]

Not sure if it is relevant to the topic, but just wan to add- I am running a Sanden compressor instead of the A6, and it draws lees engine power when the A/C is on...