As promised MINI has been working (at times with the help of MINI enthusiasts) to eliminate the dreaded Yo-Yo issue that has plagued some Cooper S's for over two years now. Now it appears they may have a solution. But first for those who aren't familiar with the Yo-Yo issue here's an excerpt of an article we ran last January about the efforts of one enthusiasts better understand the problem:
Ryan Malcolm (Ryephile on North American Motoring) has researched this subject extensively and gives us the following insight into the problem: “The Yo-Yo is the oscillation of the supercharger bypass valve, which is excited by an under-damped P.I.D. throttle body servo controller. The parameters of the Yo-Yo occurring are simple: typically during medium acceleration, on-boost, and with the throttle pedal reasonably steady. Amplitude of the Yo-Yo seems to vary per vehicle, ranging from imperceptible to an almost violent bucking.”
You can read the entire article here.
Recently Ryan wrote us again to let us know some details of the upcoming official MINI fix:
The V38 (or actually CD version 38) portion of the MINI code was completed as of Monday evening. The V38 is specifically designed to eradicate the Yo-Yo. Currently, MINIUSA is allowing select customers that have severe Yo-Yo to send their ECU's to the New Jersey headquarters through their local MINI dealership only to have the new software uploaded prior to its dealership distribution in June.
We'll hopefully have a full review of V38 in the coming weeks.
<p>Ve shall see, nearing 1,000MI I can say mine's got a bit worse a couple of hundred miles ago. Noticable, but certainly not violent. I wonder how many releases of the software their will be :-(</p>
<p>Yes I am in agreement, though it only seems to happen for me when I first start and only in second or third gears during acceleration. </p>
<p>Gabe I have played around with it, and I honestly think the reason you didn't feel it was because I had just got done driving it the 200 miles to Chicago. Next time you come home I will let you take it out fresh.</p>
<p>So let me get this straight, I have to drive 3 hours to my dealer, then they send my ECU to NJ program it, and send it back and then I will have to come back to get my MINI. When is this going to get easier?? The car is for most practical purposes a BMW!!</p>
<p>The update will be at dealerships in June. At that point you can bring it into any MINI dealership and get the update.</p>
<p>I'm happy with v36 except for the yo-yo. I drive agressively enough that I usually don't feel it. But when the wife's in the car and I'm trying to drive more moderately, that's when I really notice the yo-yo. I'll wait until some 3-tank-full reviews are in before asking for v38.</p>
<p>This sounds like a software bandaid for what really is a hardware issue (the under-damped servo controller). </p>
<p>Am I wrong in thinking that?</p>
<p>That's exactly what I was thinking. I wonder what Ryephile would say to that?</p>
<p>That's exactly what I was thinking. I wonder what Ryephile would say to that?</p>
<p>Ryan (Ryephile on NAM) is the one that sent this in actually.</p>
<p>The problem is actually poorly written ECU code. The under-dampening of the controller (dampening via software, that is) is the symptom not the cause. Controller dampening IS required but is just done poorly by the ECU software.</p>
<p>More to report next week.</p>
<p>Theo</p>
<p>The Yo-Yo is a bit of both [hardware and software]. The root cause is the software, which triggers the hardware into oscillation. With this new software (V38), the oscillation should not be allowed to occur.</p>
<p>Just wondering…</p>
<p>Has anyone noticed this with a JCW MCS or is it limited to stock MCS'?</p>
<p>My '04 JCW MCS hasn't given me any indication of the yo-yo effect in over 8,000 miles, but maybe it's because my usual throttle positions are full off or full on. I do not drive this car moderately.</p>
<p>I want it to be clear, the MCS is not the only model with the Yo-Yo</p>
<p>It's now June and the local dealerships cannot acknowledge that V38 even exists. I too will wait for others to report before I'm upgraded. My new zip tie will work for awhile</p>
<p>My Mini Cooper – not ‘S’ – has been plagued with this yo-yo effect accompanied by surging and hesitation from cold and a stumble at pull away. It also seems to be very flat and underpowered below 3,000 rpm. This has been occurring since new in September ’03. The ECU has been “reflashed” at the dealership five times now and the car still has the problem making it very uncomfortable to drive. On my last visit to the dealership – August ’05 – I was told that “all Mini Coopers are like that” and there is nothing more they can do. I don’t believe that and I’m sure someone out there knows how to cure my car. Can any one Help ?</p>