Rye, could you do a vacuum test on the stock and the modified bypass valve? If you have a Mityvac just connect it to the valve, and see what vacuum is required to initially actuate/then fully open the valve. I am curious to see what the spring changed.

 

---> snoopy: Thanks for the Link. What seems to be happening with our application (the MCS) is not the blower regurgitation, but the bypass valve itself resonating on its' too low a rate return spring. I feel aerodynamics within the intake are also playing a part, and the boosted air is actually pushing on one side of the bypass valve butterfly. The stiffer spring does not allow the airflow disturbance or the resonance.

---> h_lank: The external spring was something Chad and I looked into initially, because it would seem to be easier. Since I already had the Bypass Valve disassembled, it ended up being easier to fab one correct spring than to add a second "helper" spring. If you can fabricate an external spring, by all means, go for it! It would not have to be a very heavy spring, since it would be in addition to the stock spring.

---> 2Cool: Stock MCS engine pulls about 15 inches of Hg at idle, and about 22 in.Hg max engine braking. With Ryephix #1, the engine idles at about 13 in.Hg, and engine brakes at 24-in.Hg max. With the Ryephix #2, the engine idles at 14 in.Hg, and engine braking 23-in.Hg max. With the stock bypass valve, the butterfly progression from fully open to fully closed is between 15 in.Hg and about 5 in.Hg. With Ryephix #2, the butterfly goes from about 60% open at 23 in.Hg to fully closed at about 10 in.Hg. As you can see, the stiffer spring never allows full-open of the bypass valve, and closes both at lower throttle angles, and literally quicker with the stiffer spring and greater pre-load.

Day Two with Ryephix #2: Still no Yo-Yo, I believe this stiffer spring has definitely eradicated the physical instability, however the software instability is still quite annoying. Even a non-automotive friend could see with my boost gauge that the throttle wasn't doing what my foot was (the overshoot). I am still dropping off MM2 at the dealership to have the ECU replaced, just to rule out a possible bad part. You'll know when I do!

Cheers,
Ryan

 

Instead of a new spring, is there room to add a flat spacer (washer) inside between the spring and the housing to increase pre-load? Say a 1/4 inch thick piece of material.

 

The added preload with the stock spring would simply change where in the throttle range the instability is. A stiffer spring rate is the key. To answer your question - not really; the spring is keyed in on both ends within the diaphram, so a spacer would have to be relatively elaborate. Good question, however!

 

I can't beleive I missed this thread, I assumed it was one more documentation of a known problem with no hope of a fix. Good Job Ryephile.

I have an '04, TD77442 that has a mild Yo-Yo just as described here, right around/below 3000 RPM.

 

Never did include my info:

2003 with a moderate to severe yo-yo, Dec 2002 build, TD64498

Thanks.

 

With Ryan's permission I would like to nominate myself as "Keeper of the List". Below I have assembled all the vins and have placed them in order. If I mised yours please repost and I will add it.

TD50353 03/02 travelkids
TD51104 05/02 911RSAmerica
TD51401 05/02 2Cool
TD53564 06/02 cpeters
TD58121 10/02 ScottG
TD58445 09/02 RECOOP
TD61199 11/02 cooper44
TD62476 11/02 mudshark
TD64498 12/02 Minimoto

TD68072 ??/03 SB
TD68136 04/03 coopstas
TD68953 04/03 Darxar
TD69237 05/03 mmanasas
TD69664 05/03 Tugboat
TD70585 06/03 Wastik
TD70666 06/03 agokart
TD72531 07/03 brit-in-usa
TD73852 09/03 minionrails
TD74156 08/03 fishey72
TD74337 09/03 KatanaPilot
TD74723 09/03 apexer
TD75054 09/03 mczinn
TD75106 10/03 fuzzyface
TD75586 09/03 Koopah
TD76176 10/03 Ryephile
TD76754 10/03 JustGo4It_
TD77119 10/03 countrym
TD77442 ??/03 LeeL
TD78393 11/03 johnnycircuit
TD79087 12/03 earlyapex
TD79674 11/03 stew7710
TDS8656 09/03 Spanky_03


no vin 12/03 zfxr
no vin 9/03 mbur1024
no vin 6/02 capsfan13


_________________
Not waiting any more :smile: MINI is in the garage.

 

How about me? May '03, TD69433


>>With Ryan's permission I would like to nominate myself as "Keeper of the List". Below I have assembled all the vins and have placed them in order. If I mised yours please repost and I will add it.
>>

 

I made a typo JustGo4It_. Mine is an 04/03 build.

 

Thanks for being the KOTL JustGo4It_! Everyone note - if you have the Yo-Yo (see page 1 for definition), be sure to post your VIN ID (last 7 characters), and most importantly, tell your dealership to get ahold of MINI Engineering and ask for a fix for this problem! Mass complaints are the key here; if MINI keeps hearing that everyone has the Yo-Yo the more likely they are to release a fix.

Until then, Motor-On,
Ryan

 

hey ryan, thanks for your tenacity, patience and hard work on the yo yo problem.
TD71389 built june 27 2003
taking mine into bobsmithmini in the morning for its 10,000 mile service and the v36 software update and of course the yo-yo.

 

TD79661, 11/03 build.

Hey, if production numbers are sequential, then my car ran down the line only 13 vehicles ahead of stew7710's MCS. They probably got to know each other in the marshalling yard. So if your MCS picked up its bad habit from mine, I apologize.

 

I bashed my list with Ryan's and came up with the following. I will update the list every 2 days depending on the number of replies. Unfortunatly for us, the list is long .

TD50353 03/02 travelkids
TD51104 05/02 911RSAmerica
TD51401 05/02 2Cool
TD53564 06/02 cpeters
TD58121 10/02 ScottG
TD58445 09/02 RECOOP
TD61199 11/02 cooper44
TD62476 11/02 mudshark
TD64498 12/02 Minimoto

TD68072 04/03 SB
TD68136 04/03 coopstas
TD68953 04/03 Darxar
TD69237 05/03 mmanasas
TD69433 05/03 allen_shelton
TD69664 05/03 Tugboat
TD70585 06/03 Wastik
TD70666 06/03 agokart
TD71389 06/03 manoo
TD72531 07/03 brit-in-usa
TD73370 ??/03 reshultz
TD73852 09/03 minionrails
TD74156 ??/03 fishey72
TD74337 09/03 KatanaPilot
TD74370 09/03 Ken G
TD74679 09/03 Greg B
TD74723 09/03 apexer
TD75054 09/03 mczinn
TD75106 09/03 fuzzyface
TD75554 09/03 MidMichMini
TD75586 09/03 Koopah
TD76176 10/03 Ryephile
TD76442 10/03 Chad B
TD76754 10/03 JustGo4It_
TD77119 10/03 countrym
TD77442 ??/03 LeeL
TD78393 11/03 johnnycircuit
TD79087 11/03 earlyapex
TD79661 11/03 Parklife
TD79674 11/03 stew7710


no vin 06/02 capsfan13
TD ???? 09/03 Spanky_03
no vin 09/03 mbur1024
no vin 12/03 zfxr

 

Please add to yoyo list TD78920 11/03 build.
Harvey

 

Please add mine to the list: TD80331 12/03

 

I forgot to list my build date, it is mid/late 10/03.

 

>>Thanks for being the KOTL JustGo4It_! Everyone note - if you have the Yo-Yo (see page 1 for definition), be sure to post your VIN ID (last 7 characters), and most importantly, tell your dealership to get ahold of MINI Engineering and ask for a fix for this problem! Mass complaints are the key here; if MINI keeps hearing that everyone has the Yo-Yo the more likely they are to release a fix.
>>
>>Until then, Motor-On,
>>Ryan

---------------------------------------------------------------------------------
Fellow Yo-Yos,

Everyone on JustGo4It_'s list should send Ryephile's problem and solution information along with the current members of the list to their MINI dealer. It should be a formal note stating, in a direct but reservered "tone" your "concern for the less than stellar level of customer service and engineering excellence"...something along those lines. You need to get the message to the Owner or General Manager and also to the Service Manager, Business Manager, Sales Manager and, if they have one, the Internet Sales Manager.

Request that your information be forwarded to the MINI's Regional Management and make sure that you are copied on all forwarded communications. You may wish to call BMWNA in New Jersey and ask to speak with someone in Customer Relations.

If you can't get connected or have to leave voicemail, pay careful attention to the name of the person you are trying to reach. You may have luck getting an email to that person by sending it to [firstname.lastname@bmwna.com]. If it bounces back to you, try modifying the name (like "chris" instead of "christopher", or the reverse).

Again, the four key elements of the message should be (1) polite dissatisfaction, (2) Ryan's documentation of the actual problem, (3) Ryan's mechanical phix (stiffer bypass valve diaphragm spring) to negate the actual problem (throttle body servo overshoot) and (4) the current list of VINs and production dates.

One can argue if this action will really help.....well, it's kinda like chicken soup for a broken leg..... it certainly couldn't hurt! We need to recognize MINIs classic use (and success) of guerilla marketing and use those same tactics to get US noticed by THEM!

Good Luck All!


_________________

 

Neat thing is that I just installed a boost guage, and I can watch the needle jig with the yo-yo acceleration. It drops and raises in perfect time with the yo, pretty good sign that the bypass valve is fluttering.

 

A Couple of Additional Items:

We need to understand how the MINI business structure is organized into regions. We also need to know the names, titles and phone numbers of key MINI Management in each region. Knowing this will help us focus our communication to the appropriate channels "en masse".

If anyone is particularly cozy with someone in the know regarding this issue, please...please...please try to get this information (or a number of a person to contact) and pass it on to me. I will start building the structure from the botton up and will put together a guerilla communication plan to contact these folks and raise their awareness of this issue. I will hold all information sources in the highest confidence.

Ryan -- might I ask you to author a couple of paragraphs that we might include in our communications? In these paragraphs, you might describe:
(1) the testing data (and test tools) you used to identify the overshoot issue;
(2) the testing data (and test tools) you used to determine the bypass valve's role;
(3) the modifications to the stock bypass valve you made;
(4) the testing data (and test tools) you used to verify the modification's ability to counteract the overshoot problem.

I know you have already done all this in your posts, but collecting it up into a couple of summary paragraphs would allow us to "cut and paste" your words into our communications. Thanks for considering this!

TTFN,

 

TD60679 10/02 DaveNagy

Thanks again for all your efforts.

-Dave

 

How's this?:

If that sounds good - short and sweet - attach that to your letters/emails to your dealership.

Cheers,
Ryan

_________________

 

Phantastic!

Thanks, Ryan!

Folks -- please use Ryan's text above in your communications. Part of the power of this approach is that everyone connected with MINI will be hearing the same problem description and related information.

Let the games begin!

 

hey ZFXR chiming in here-
my VIN ends in TD80285

 

Add me to the list

12/03 TD81147

Cheers,

JD

 

Add me to the yo-yo list. TD67984. I believe that the build date is March/April 03. Again thank you for all the hard work.
Jeff