I recently installed a BMP Promini Cold Air Intake on my 03 CVT Cooper.

The car used to yoyo like pretty much everyone elses, at low speeds, but now the yoyo is gone. Also acceleration is much smoother and stumble free.

I should also mention that I had the car only 10 months, when I removed the factory filter and it was filthy with leaves and deposits. Those of you that never check this, do so and clean it often.

Anyone else have the same experience after changing air filters?

 

I wasn't aware that the cvt had a yo-yo effect. I thought only the MCS did. And no a filter does not cure the yo-yo because I have a new filter non-stock. Yo-Yo still there....

 

I think he got a CAI and not just a drop-in.


I think it could improve if the yoyo was caused by too much fuel.

 

Yo-yo, as I'm familiar with it from this site, is a result of the supercharger bypass valve opening and closing rhythmically. As a CVT Cooper has no supercharger, how does it have a yo-yo?

I'm looking to learn here. I haven't heard of a MC with yo-yo before.

 

You can't have a yo-yo on a Cooper. The phenomenon is a function of supercharger bypass valve operation. No supercharger, no yo-yo.

You could have some other condition that feels like a yo-yo, subjectively. But in the strict definition of Yo-Yo, that would be something else.

Check out the yo-yo chronicles and this other thread about the bypass valve for details.

 

I think he is talking about a non-smooth take off that seems to be common with the CVT.

 

Bingo!

Sorry, but the CVT when travelling at 0-10 miles an hour has a yo-yo effect. I did not realize that "yo-yo" is now a technical term associated with a specific MCS problem.

Basically, yes, my takeoffs are smoother and I do not get the jerking effect any longer.

 

Hey everyone I'm getting my Cooper S with the works in a couple of months...i'm just curious what is the yo-yo exactly?...

 

Lurch,
I had everyone jump on me when I mentioned my MC 5 spd had a 1st gear stumble. I guess the people that have a MCS like to think they are the only ones that have problems with their cars.

 

Thats one arguement I would want to win...

"I HAVE MORE PROBLEMS!!"
"NO, I DO!! "

 

You already beat me. I got rid of my MC, too many problems.

 

actually that jerking effect did not bother me, i rather liked it in some twisted way. it was like driving an old school manual Fiat

 

If it isn't a Duncan, it isn't a Yo-Yo.

 

That's right! All MCS's come with the Duncan Butterfly YOYO. Maybe he has the classic Duncan Imperial!

 

Its when you accelerate (especially pronounced in 2nd gear) and the engine
sort of hoppidie hops your car while you try to maintain smooth, linear acceleration.

My MCS has that if you engage 2nd gear at too low of an rpm with a quick
clutch engagement. I slowed down my shifts and gently engage the clutch
into 2nd and the yoyo phenomenon (?) is gone. :smile: I am on pre-v36 program.