well, I threw in the towel on my MCS. 1000 miles and a little over a month. It is/was a fun car but the little things combined with the YoYo got to me and it wasn't the right car for me at this time. I traded it on a new Volvo V70R, a completely different direction. I may check out the MCS again when BMW does a refresh or offers an AWD setup.

This is a great community, kudos to all. Ryan, I hope Mini drops you a free JCW kit for your R&D on the YoYo.

cheers.

 

--->stew7710: I'm SO sad to hear you traded in your MCS, but I do understand very well your frustration! If I wasn't so in love with the MINI, I would be right behind you putting a deposit on the new Volvo V50. Thanks for your compliments, and I hope to see you back in a MINI when the new platform comes out in a few years!

Update; My dealership just FedEx'd a hard copy of this thread to Chris Weiler at MINI Engineering. Chris said he'd look at it the second he recieves it. Finally, an official MINI reaction!

 

So, just how prevalent (sp?) is the yoyo? I've read that lots of people have it and can produce it in any gear. Is it a constant thing every time you try to accelerate whether from a stop or already moving? Or is it an occasional annoyance?

 

The Yo-Yo seems to be vehicle dependant. Some have it and some do not. Those that do, the amplitude of the oscillation is different from car to car. The nature of the Yo-Yo leads it to occur only when accelerating, not launching, decelerating, and not steady-state cruising. Most MCS's do it at part throttle, though Randy has driven one that does it at wide-open-throttle. Most MCS's do it in 2nd and 3rd gears, due to the relationship between engine loading and throttle angle, however some do in every gear. The oscillation frequency is RPM dependant; resultantly it feels like a fast bucking at higher RPM, and a slow pulsing at lower RPM.

I hope that helps clarify more :smile:
Ryan

 

how is the V70R?
love my mini but at times i really long for AWD, especially as i contemplate putting on the snow tires to go skiing...

 

Keep us posted. :smile:

 

the YoYo on my '04 was very noticable when cold in 2nd, 3rd, a bit less in 4th and slightly in 5th. I don't recall sensing it in 6th. After warmed up 2nd and 3rd gear the YoYo was still there, enough that passengers noticed. Combine the YoYo with "lump lump" of cold run flat tires while trying to block the glare of the morning sun coming in the side window (useless sun visors) makes for an "entertaining" ride each morning.

The V70R is obviously a completely different category but for daily driving much more comfortable. The Advanced suspension mode setting is firm, not quite as firm as the MCS but you can definately feel the surface of the road, unlike the Comfort mode setting which is considerably softer. I miss the AUX input! The iTrip just doesn't have good enough sound quality. The AWD combined with Vredestien snow tires makes for a lot of fun. :smile:

If the Yo-Yo would have not been there or if v36 would have corrected it I think I might have held on longer.

 

I received my bypass valve from Classic MINI today (yay UPS!). I promptly ripped it out of the box and tore it apart I couldn't immediately find a stiffer spring rummaging around the house, so I'll go play around at a hardware store or two tomorrow. Here's the deal:

"Air Shut Off Valve" Part number 11-61-1-501-937 Cost: $49.95 from Classic


A shot for scale, I have a size 9 hand. Where my thumb is, that's the linkage you disassemble when you go to tie the valve shut. The setscrew at the tip of my thumb; you tie the zip-tie around that and the metal shaft of the linkage.


The disassembled bypass valve. From Left to Right:
Vacuum diaphragm-to-butterfly casting mounting plate
Vacuum diaphragm top
Spring
Vacuum diaphragm bottom
screws for the mounting plate
The Diaphragm, with plastic tie-rod
The Casting, includes the butterfly, vacuum line and metal shaft for the linkage


Now, this assembly is totally self-contained. The vacuum line goes from the front side of the butterfly to the vacuum diaphragm top piece, which sucks in the Diaphragm. The spring tries to keep the tie-rod pushed out (so the butterfly is closed). I am going to put in a stiffer rate spring, to make the butterfly harder to open per given vacuum. The idea is the bypass valve will tend to stay closed except for very light throttle cruising, coasting/engine braking, and idling (all big vacuum situations).

Whew, enough for now,
Ryan

 

Sounds like a good plan :smile:
It seems like a stiffer spring will address the issue...
I wish you luck and success

<<"Air Shut Off Valve" Part number 11-61-1-501-937 Cost: $49.95 from Classic >>
For some reason I expected this part to be much more expensive.????
It seems reasonably priced....

Peace,
D

_________________
PM d-mini-ero

 

Ryan --

Could you take one more quick set of photos showing the "Ryephix" installed on the Air Shutoff Valve you have purchased?

It might help those wishing to execute the fix.

Cheers,

 

Ok, after some research, I managed to find out why there is a bypass valve on the blower. It is there to prevent trapping and heating charged (compressed) air during part/off-throttle, and also to cool the blower during off-throttle running via the airflow over the rotors.

So this mod could have an effect on the long term durability of the blower, and short term effect by providing intermittent higher than normal temp airflow. Not sure if this could lead to intermittent short bouts of detonation due to the heated air, but it is a concern to me. So hopefully the stiffer spring works, as simply zip-tying the linkage is not a good long term fix.

 

RYEPHIX: An illustrated guide in six easy steps
______________________________________________
Tools needed:
- #1 flatblade screwdriver
- Needle-nose pliers
- Nylon zip-tie

Vehicle performed on: 2004 (11/03 build) MINI Cooper S

1. Using the #1 flatblade screwdriver, release the clamp holding the flexible rubber tube to the air inlet snorkel. Simply insert the screwdriver and twist anti-clockwise.


____________________
2. Using the same screwdriver, release the four tabs holding the air inlet elbow to the radiator core support shroud. There are four plastic tabs that can be accessed from the front of the shroud. Remove the elbow and set aside.


____________________
3. You should be able to plainly see the bypass ("Air Shut Off" to MINIdivision) valve at this point. The circled area is shown in close-up.




____________________
4. Using a pair of needle-nose pliers, gently pry off the plastic linkage from the vacuum actuator to the bypass butterfly.


____________________
5. Secure the linkage for the bypass butterfly to the set screw for the butterfly stop using the nylon zip-tie.


____________________
6. Re-install the air inlet elbow. First, push the rubber hose over the inlet snorkel, then snap the inlet elbow into the radiator shroud. Re-tension the hose clamp by squeezing it back together using either your needle-nose pliers, or optionally a pair of slip-joint pliers



Hope this helps, guys.

 

Parklife - thanks for posting an excellent How-To!

--->2Cool - I've been thinking about your comments for a while. I would like to know where you found that information, because it just does not sound right. The supercharger is always compressing air, the density of the compressing is strictly based upon how much air the throttle body lets in, so air is always "flowing" over the rotors in proportion to how much air its' compressing. Subsequently, the amount of air being compressed over the superchargers life will be greater provided there is no bypass valve, however then again it's power output will be greater too. This is a compromise. Modern production tolerances will ensure the M45 lasts for well beyond 100k miles, however Eaton still recommends the supercharger be replaced every 100k miles. At that relatively low mileage, I can't see why there would need to be a distinction in bypass or no bypass valve. If you're trying to squeeze 150k+ from your M45, then most likely you're also interested in maintaining the fuel mileage of a bypass-valve equipped system. Furthermore, if you simply cannot stand the Yo-Yo, then the zip-tie method (Ryephix #1) is the perfect short-term solution, as we have both said. I hope this clears the air a bit


The bypass valve butterfly mechanism. I backed off the setscrew about a half turn in order to have the bypass valve butterfly close fully - thus allowing for more boost via less leakage.


The diaphragm top (on left) and the diaphragm itself, with assorted prototype springs in the background.


The kicker - The Prototype Bypass Valve spring (on left); 0.082" diameter wire versus stock 0.050" wire.

I added one turn in the coil for added preload. This new springs' thicker wire results in a much higher spring-rate than stock. The idea of this new spring is to keep the bypass valve closed or mostly closed under moderate to heavy acceleration. With the new spring, the bypass valve only opens up about 30% at 15 in Hg (idling), and about 50% under 22 in Hg (engine braking). This means that even during heavy engine braking, the bypass valve is still only half open now. With the heavier rate spring, it follows your foot "mashing it to the floor" much better than stock.

Conclusion: With this heavier spring and the bypass valve hooked up like stock, there is no Yo-Yo. The ECU P.I.D. overshoot is still apparent (just like with the Ryephix #1), however the increased spring rate now implemented in the bypass valve does not react to the overshoot of the ECU. This means that I've solved the issue from a hardware perspective. Now MINIUSA needs to get off their butt and write some quality code for once!

Caveats: sarcastic ---> Good luck making your own spring! We happened to find a spring of similar average diameter and morphed it to fit within the diaphragm housing. Shaping the spring took quite a while, and even induced a few injuries!

Cheers and Happy Motoring,
Ryan

_________________

 

It should be noted that the spring fix worked out very good, but it would take some number crunching and engineering work to figure out the exact spring rate that would be need to optimum gas mileage and boost performance. While we did pull out some spring books I have (since I am a design engineer) and found out what the spring we fabed was putting out and the stock spring was putting out, it would still take some engineering to find out the exact numbers. But with a team of engineers that mini has, this should have been an easy one to figure out the fist time. It’s basically simple math between boost and vacuum and spring rate. If we had a few more test instruments that we could have gotten hard numbers and could find out what length and spring rate would be best. But since we do not have a few thousand dollars to dump into test equipment that we will only use a few times in our life, I’ll let mini do there job and figure this one out. I would also like to know if that spring has been changed anywhere in the model years and why. Since most mid year 03 and a lot of 04’s have it and not to many 02’s have it and they all have the same spring why does one work and other’s do not. But since we were not asked (or at least I do not thinks so) what year we have, then I would guess it is the same part number for all model years. There are so many ifs to think about that we have to keep testing new things. We hope that this one is very close. Now I just need to heal the cut on my finger ..lol

 

I love the grassroots nature of this fix.

If MINI and MINIUSA were responsive, then customers wouldn't resort to these measures. Come on MINI.

 

That specific quote is taken almost verbatim from the Feb 10th edition of 5.0 Mustang Magazine, page 76, in regards to a Kenne Bell blower setup. It is speaking specifically about the benefits of using a bypass valve. As a KB is an autorotor/screw type blower, much more efficient than the Eaton's roots style compressor; if it is an advantage for that blower then it is even more so for the Eaton. Otherwise why would the blower manufacturers include such a feature? Surely its not just a bean counter requirement for maximum fuel economy and CAFE averages, not when its a desirable item on aftermarket parts for making the most efficient and highest power numbers.

As I said, I am hoping a spring replacement is the solution, as I feel much better with such a minor tweak, as opposed to a complete disabling of a feature that blower manufacturers apparently consider mandatory. Please keep us updated on the spring solution, especially if someone can find a replacement that will not require access to a machine shop for implementation.

Also, you do not actually need to remove vacuum solenoid lever, just zip tie the lever in place and leave it connected. Same result, and you do not risk breaking the plastic lever.

 

I feel that most of the reason for the by-pass valve is purely for maximum fuel economy. The US Government places lots of standards on carmakers. In order for any maker to sell a car in this country hey have to meet a fleet fuel consumption number. So if auto maker X sells a million SUV’s that get 5 mile to the gallon they also have to sell a million econo cars that get 35 miles to the gallon so that they equal 40 or the car maker has to pay a fine. That is why we have air bags and now second generation air bags, and 5MPH bumpers, catalytic converters, and a warning sticker on everything. The list could go on, but I am soooo hijacking the thread right now I am going to stop and not say another thing about it in this thread. But I am sure it is there for gas mileage.

 

Great stuff Rye :smile:?????

Let's hope Mini Division.... takes notice ... and acts!!!!

Peace,
D

 

Is there any way we could do an online petition or something with sigs to help insure MINI takes this seriously and does something about it? NAM has over 11000 registered users. I think that would make quite a statement!

 

Ryan, this is an incredible piece of detective work, thanks.

As a fresh newbie to this board, and a newbie MCS owner (1800 miles), and with a minor yo-yo which v36 did not help, I have the following suggestions. My suggestions are untested. They are possible only because of your hard work uncovered the root cause (pardon the roots supercharger pun):

I would like to propose the following potential fixes which may be easier to get at than disassembly and new INTERNAL spring installation. I propose an EXTERNAL spring.

Theory: If the stiffer internal spring solves the problem by preventing the butterfly from opening all the way (or at a different rate or both), then how about these other external methods to change the movement of the plastic linkage from the vacuum actuator:

Proposed Fix A: Some sort of small C-clamp or screw directly onto the plastic linkage to create a stop. That way the vacuum cannot pull it all the way in. This at least stops the travel at, say 50% of normal movement, akin to what the stiffer internal spring does.

Proposed Fix B : Attach one hooked end of spring onto the end of the plastic linkage or the butterfly pin it connects to. The other hooked end will need to hook onto something solid nearby. (I have not looked). This new external spring will accomplish the same thing as the internal spring, slowing and/or limiting the travel of the plastic linkage, and thereby the opening of the butterfly. Of course, testing with various lengths and strengths of this external spring will be needed.

What do you think??? Thanks, Harvey

 

Further research, which does not back my original as much as I might wish, but is good info is located here: Eaton Supercharger Site

Look down to item #7, where basically they state that fuel economy and lower noise are their reasons for using a bypass valve. The first is good, the second bad, at least in my biased opinion. I will continue to research the bypass usage issue though.

 

Let us not forget that Ryephile and agocart also adjusted the set screw to ensure that when boost is required, there is no leakage around the butterfly valve. This seems to be an interesting point.

The part Ryephile purchased from MINI was not set up properly. That is, the butterfly was not able to close completely because of the position of the set screw. Obviously, this reduced actual boost by some degree. And, hey...aren't folks paying Randy the big bucks for every bit of boost possible?

While a temporary external Phix, as h-lank has suggested, is really easy and appealing, it does leave open (!) the issue of the butterfly valve set screw being misadjusted from the factory. The way I look at it, if I'm going to spend time on the Ryephix, I'm going to do it right and replace the internal spring and also check the butterfly setting.

Or, I'd gladly let MINI do that for me under my warranty coverage! (Hello???)

 

I think all the work being done here is great. I thought I might add this quote I found on the web about superchargers, surging and bypass vavle.

The Bypass Valve
Compressor surge is a problem that affects most superchargers and develops when the supercharger is creating boost, but the throttle shaft is closed. Although not a problem on some low-boost (5psi or less) applications This condition can occur under deceleration or while shifting between gears, and can cause the car to sputter and chirp. Under surge, the compressor forces air into the closed throttle body until the pressure inside the throttle body is higher than the amount of pressure being created by the supercharger, and the air tries to pop backward through the supercharger. At that point, pressure is released inside the throttle body and the compressor forces air back through the supercharger and into the throttle body, which again has nowhere to go, and the process repeats. While surge normally is not highly damaging to the engine it is certainly annoying and can cause damage with time. To eliminate these problems under surge conditions, a bypass valve (sometimes called an anti-surge valve) is used to release the excess pressure. The bypass valve is actuated using intake manifold vaccuum, which opens the vent valve and releases pressure in the air-intake. Air is either released into the atmoshpere (blowoff valve) or recirculated back through the supercharger compressor (bypass valve).

Supercharging online

 

Koopah, I think the set screw adjustment (for when the valve is supposed to be completely closed) would only effect the supercharger output at WOT. or whenever vacuum is less than the partial-throttle or closing-throttle settings that create the yo-yo. So adjusting it shouldn't help the yo-yo.

But if it is set wrong from the factory, then it would rob you of some WOT power. I wonder if a slightly cracked open butterfly would vent enough to do this? The fact that there is a set screw at all implies it might. The total amount of airflow would seem to be small, but if it is worth 2 hp, then.....

I'd go look into my external spring idea tonite but the Mini is covered in snow. Harvey

 

>>Koopah, I think the set screw adjustment (for when the valve is supposed to be completely closed) would only effect the supercharger output at WOT. or whenever vacuum is less than the partial-throttle or closing-throttle settings that create the yo-yo. So adjusting it shouldn't help the yo-yo.
>>
>>But if it is set wrong from the factory, then it would rob you of some WOT power. I wonder if a slightly cracked open butterfly would vent enough to do this? The fact that there is a set screw at all implies it might. The total amount of airflow would seem to be small, but if it is worth 2 hp, then.....
>>
>>I'd go look into my external spring idea tonite but the Mini is covered in snow. Harvey


Yeah, I with you. I didn't mean to imply that any adjustment of the butterfly would lessen the yo-yo. I just want all the PSI that teh MINI SC can muster at WOT!!!

I hear you about the snow! I live in W. MA and it .....well, you know the rest...