I'm new to the whole Mini scene. I have a 2005 MCS w/ stick. Awesome little car, but it seems to bog down slightly when leaving from a stop with the A/C on. With A/C off, seems fine. Is normal behavior of a Mini, something inherent with a small displacement engine being taxed by the A/C, or a possible service issue?

 

Small motors and big loads don't go well together. It's par for the course.

Matt

 

I sort of figured as much but just wanted to make sure. Thanks!

 

If you plan on modding it at all, a pulley will get rid of this problem.

-Cody

 

Ehh, not in my '06.

 

I disagree with you on this one Cody.

If its 90+ degrees out and I'm in traffic with the A/C blasting, my engine feels so weak when starting from a stop. I just have to give it a little bit more gas and bleed the clutch in when I'm taking off. The car definitely revs a lot freer with the A/C off hot traffic, but the a/c will definitely be on when I'm driving it.

As Dr. O stated, it's just one of those payoffs you get with a small SOHC 1.6L engine.

 

I really appreciate all of the opinions! Thanks for confirming what appears to be "normal". I guess it's a very small trade off during the hot weather.

 

Yeah you have to live with it. The solution......I turn off the AC for a few seconds then turn it back on when up and running...

retroom

 

My MC has the problem, I don't know if it's worse than the MCS, but it is downright dangerous at times.

 

That's the reason my wife is driving an MCSa instead of the MCa. With the AC on, the '05 MCa was very sluggish.

 

After installing a 16% pulley, I was impressed in how it helps at the low-end. Especially with the A/C on and during a low RPM launch...

 

eh. i got used to my ac. i still sweat a little at times. but that's when you gotta NOT stop and run those stop signs and red lights..hahah kidding of course.

 

while a pulley helps some, remember, this is off idle acceleration, and the pulley doesn't really kick in until about 3k RPM. An expensive way to fix it is a head that really boosts low end torque. But this is just the nature of the beast with small motors. A/C compressors take a bunch of power, and the car doesn't make that much off idle.

Matt

 

True, there is no getting around the fact that the a/c will sap power and this is most noticable when starting off from a stop. But, if you notice a signiciant degradation, or significant engine shake, a relay may be bad. When the a/c is on, the idle should kick up to be close to equivalent of idle without the a/c on. This obviously won't bring back lost power, but it will make idle smoother and decrease stumble on start off. To test, when idling, if the a/c is on, switch it off. Idle will momentarily jump, then return to normal. Conversely, if the a/c is off, turn it on. There should be a very brief dip in rpm, and then a return to normal.

 

The easiest and cheapest fix for this "feature" is in your own hands, er, feet. You only need to adjust when you engage the clutch relative to when you press the accelerator pedal. You need to give the engine a fraction of a second to rev up from idle before letting the clutch grab. Once you master this, the problem goes away . . . .

 

warm car, no A/C ~800 RPM
Warm car, with A/C ~1100 RPM.

Still far from the power band.

Matt

 

Very true. My point is, you will be less likely to "stumble" at take off.

 

Last saturday it was around 42C (107F i think), I had my A/C on full blast for the first time.... I am soo happy to see im not the only one with this problem.... I recently bought my car and I thought I hadn't still gotten used to the clutch... it was HARD taking off.... I opted for lowering the level for every takeoff....

 

1100 rpm idle? Mine is ~800 rpm whether that A/C is on or off .

 

The other factor no one is mentioning is the tall 1st gear...........it's a bit of a PITA around town, kicking the A/C off realy does make a difference, but it's also a PITA and a distraction when you're in traffic. Just slip the clutch a bit more............or I guess one could put on a set of 15's with smaller rolling radius tires, effectively lowering the gear ratio...........

 

I agree, but since I don't use my A/C very often, I always stumble for the first few starts until I remember that.

 

When we're out at the track, we have A/C off and DSC off because of the sluggish start. It gets hot in the MC!

 

A pulley upgrade doesn't just kick in at 3K. The supercharger is spinning faster at ALL RPMs. A pulley upgrade helped enough for me to not consider lazy take-offs, with the A/C on, a liability... -B

 

and it sucks down low. And all those dyno plots were at wide open throttle, that closes the by-pass valve and generates maximum boost when you floor it. If you don't floor it, the valve may even be partially open. Sure the SC is spinning, but it's not moving much air. Here's a boost curve to show what I mean.....


This is from a my 02 MCS car (15% pulley) and at 2000 rpm it is only developing 50% of full boost. Yes pulleys do move the curve down lower, but there's no getting around the fact that the engine isn't a torque monster down low.

Matt

 

Edit: eh... changed my mind.