I'm not really sure how to ask this question, so pa'lease bare with me.

On the highway at a constant 4,000 rpm, 90 degrees, 90% humidity, no AC, the car, on occasion, feels like a lug when the throttle is opened partially. However, when the AC is on, but the compressor cycle is off, the car pulls like a monster. What's happening to the timeing, A/F ratio and or cooling?

I can only think that when the AC is on, the fan cools things down a bit helping timing and all the other above mentioned crap. The car runs better in these conditions with the AC on What's going on here?

 

I've also noticed that after a little drive on the highway (about 1.5hour) with the AC running, I turn it off and get on "city driving mode", my MCS pulls a lot stronger...

I don't know why, because on the AC, my MCS seems to miss a little bit of torque...

But as soon as I take it off, the engine is a lot more responsive.

 

My WAG would be that the ECU is programmed to offset the parasitic loss of the AC, so provides relatively more throttle (remember, it's drive by wire) when the AC is 'on' than when it is not. But that's just a WAG.

 

...sounds reasonable. Do you think post fan cooling has some effect as well?

 

That is very possible. My MINI does run completeley diffrent in cooler weather. This week we are about 20 degrees cooler and I am flying. We all know that these cars hate heat. I will try to wire a switch to the fans.

 

What I notice with the AC OFF, the car seems to be smoother,better torque and more responsive like what DarkMiniCooperS mentioned. With the AC ON the car is a bit sluggish

 

I think your feeling the power when its cooler from the intercooler dropping air temp. My car is a rocket on some mornings and on cool nites. I dont think keeping our fans on with a switch is gonna make a difference.

I am installing my pulley tonite at my friends shop and this mod my friend did on his lowered the IC temp by 20-30deg i think he said....I'll take sum pix of what we will be doing.

 

I have a 50 mile commute to and from work. These observations are within the 50 miles. Again, the car feels sluggish when the AC is off at the ambient above. When the AC compressor is on, it is still sluggish for obvious reasons. However, right after the AC compressor shuts off, the car accelerates much like it did all last winter...depsite a JCW intake flap that still refuses to open after 4,500 - right from the install date. "We dunno, this has never happend to anyone before." #%#@%#%!

 

Did your check your vacuum lines and wiring?

 

The tuner MTH file takes care of the AC lag, AND turns the fans on sooner. Best of both worlds!

 

Very quickly 1FSTMINI. Everything seems okay. I just have not had the time, the Dealer(s) are not very cooperative, and I'll probably end up with the Alta anyway.

 

...hmmmm...

 

Tell me about this MTH thingy please!

 

Does it means the fan will be ON most of the time? I didn't know the tuner file can do such.... impressive.

 

Yes it turns them on at a lower temp than stock specifically for these reasons.

 

can you take a hose from your AC and then plumb it into your intake hose, then you would be jetting in 40 degree air into the intake. That would make the intake charge alot colder. Could this work or am i just full of ****. Cause this performance shop that i go to alot, they make custom performance parts and i saw them make a water/air intercooler thing and they plumbed it into the AC to when the AC is on or what ever the water going through the intercooler is really cold. Just a wild thought. Tell me if it could work.

 

Well, you are almost on the right track. The a/c line is not *dumped* into the intake...that would stop the engine. Some setups however do run basically a small heat exchanger through the intake, acting as a refrigerated intercooler. The downside is, it only lasts a few seconds, as the heat builds back up.


Ford actually did it stock on a Lightning. It was good for a quick ~20HP boost, and automatically recharged itself for a few minutes after use. Kind of like a free, real small nitrous boost. I wouldn't pay extra for it though.