Someone mentioned earlier that the TB, BValve, and Intake formed a resonant cavity. Ryephile said he changed the dampening of the Bvalve by making the spring stronger. What about changing the resonant frequency of the cavity? Lets say you put in a larger intercooler. The volume of the resonant cavity would increase, lowering the resonant frequency. Is there anyone with a larger intercooler that can tell us if they have YOYO? How about a larger diameter vacuum line(and fittings as well) at the Bvalve for faster operation of the diaphragm. This might raise the resonant frequency of the cavity.The end goal would be to change the resonant frequency to something out of the normal range of operation. Maybe changing the length or volume of the intake, before the TB, could also affect the oscillation of the intake air mass. I think we would have better luck than trying to get MINI to change the software. I havent mentioned it before but my May/2002 has the YOYO and so far I've not complained because at least/last I don't have the stumble.

 

I can't understand why folks are all waiting on BMW to find a remedy to your yoyo problems. Many people have cars that work without yoyo.

BMW couldn't make mine work so I Lemoned it - I would have asked for a replacement car if it weren't for the extreme dishonesty from NJ down to the dealer, in the way they dealt with the issue.

Many minis don't have these problems - don't settle for less than what you paid for folks - if your car doesn't accelerate smoothly, take it back and demand it be fixed or refund.

 

Tokio - I understand where you're coming from; there's no excuse for MINI's incompetence in what is a relatively simple issue (not to mention a path that is well worn in the engine manangement community!) Somedays I feel regret I've modded MM2 as much as I have, and contemplate returning it to stock and pushing the Lemon route. That wasn't, however, my initial point starting The Yo-Yo Chronicles. I wanted MINI to be aware of a problem and try to help them rectify it, to better the vehicle and help my fellow Motorists achieve maximum Motoring pleasure from what is otherwise an excellent automobile. I appreciate MINI's efforts, however I'm simultaineously frustrated at the red-tape and additional incompetence (solving some items while messing up others!) Students don't get diplomas for trying but failing a class, and subsequently MINI has no right to feel its "we tried" effort is valid!


--->MINISQL: My 1st MINI had the Stumble, so I have first hand experience on both it and the Yo-Yo. I'll say it again; I'd rather have the Stumble than the Yo-Yo anyday!

 

i did like the idea a few posts ago about adding a bigger intercooler to you motor to see if the yo-yo is still there. i bet we could ask tom to barrow his for a afternoon of testing. and for as far as mini, i would throw the stock valve back on and make then drive it again to show them they have not fixed everything. it's never to late to go back to stock. we can make it happen in a afternoon. all we need is a few parts....

 

Ryan, I just meant that I dont want to install new software and get the stumble back AND still have the YOYO. My original problem was cold start, cured by new sftwr, but added stumble and yoyo. More new sftwr, stumble gone, but still had yoyo. So I'm a little gun shy about the software. Seems like everytime some problems are cured but others are introduced. Your RYEPHIXs were mechanical approaches to cure the symptoms and it seems that for us that path my bear a little more exploring. The FIX for the problem ultimately has to come from MINI via corrected software, but they may not be willing to invest the effort or money since they will be getting a new engine in the next couple years(and possibly a whole new set of problems).

 

As a nonmechanic type, I would very much appreciate someone posting a link to any pics that illustrate the steps to zip tie my yo-yo'ing MCS.

Thanks!

 

--->MINISQL: Have no fears, the Stumble was actually fixed with V36, and is definitely still gone with V38. Yo-Yo is reduced, but not eliminated...more on why in a bit. If V38 holistically sucked more than V36 or prior, I'd tell you!

--->jterk; please visit Page 6 of this thread for pictorial How-To's for both Ryephix #1 and #2

More Deductive Reasoning:
V38 seems to attempt to fix the Yo-Yo by changing some of the gains in the PID controller instead of rewriting a new algorithm. While this essentially masks the problem, it is a band-aid to the sub-optimal algorithm they left alone. As you may have remembered way back in this thread, I mentioned that changing the PID gains takes literally 10 minutes. It looks MINI has taken this very quick (and cheap) approach to try to fix the Yo-Yo as much as financially feasible (breathe in....sigh )

Well, until next time, Motor-On,
Ryan

 

I REALLY suspect it's just a PD controller.

There would be very little need for an integral gain since the user will correct for steady-state errors.

(For an article I wrote 4 years ago about tuning PID control loops, please see Circuit Cellar article)

 

Trippy - I believe your Geek Quotient just went up significantly

 

Ryan,

Ah if only that were true. My 2004 Cooper S with v36 installed has a pretty bad stumble problem -- bad enough for me to often feel uneasy pulling out into traffic -- so that issue has not been fixed either.

 

My 02 MCS seems to have cold start and stumble problems. Should I have my ECU updated or should I leave well enough alone?

 

Pet --

I'm guessing you took delivery of your 04 in the latter half of September or very early October. Is this right?

The reason I say this is because v.36 was loaded on all incoming 04 MCSs at the VPC in NJ beginning sometime in very early October. Yours may have come in prior to that time.

In any case, you may want to ask the dealer to re-flash your ECU with v.36. It is most uncommon for an MCS to stumble with v.36 loaded.

FWIW,

Theo

 

With all of the discussion about ECU versions and upgrades, is there a way for an owner to retrieve the current ECU version number without going to the dealer?

 

Koopah -

I took delivery in early January 2004. It was built in December 2003. I was all set to ask the dealer to flash to v.38 until Ryan discovered its bad points. I'll get into the debug mode this weekend and verify that v.36 is actually loaded.

 

How do you verify the version w/o going to the dealer?

 

I noticed stumble & yo-yo in my throttle response immediately after taking delivery of my MCS back in Dec 03. I've been regularly watching the yo-yo thread on this site and finally decided to take the Mini into the dealer for a look @ 7 K miles. I had a couple of Mini service managers tell me that the problem was low octane pinging--I refused to take my Mini to any dealership that gave me that line. It appears that the dealships are taking a "damage control" approach to warranty service and are reticent to admit to anything. I hope they can fix the problem permanently. I'm taking a copy of Ryan's discovery with me. I also have the pronounced knocking around 3000 RPM in second gear which seems to be related to the harmonic balancer--we'll see. The tranny has a big clunk moving from 1st to 2nd gear at lower RPMs--seems to go away if you make your shifts at 4000 RPM. I'll keep on it--the car is simply a blast to drive.

DS/WHT MCS:Madness sway & intake :smile:

 

we can guesstimate based upon your build date, that's about it. I don't know of any deciphering codes for the car's various display codes.

 

Would you explain your reference to debug mode, and verifying version loaded? Also, is there any technical documentation provided by BMW, or 3rd party, guiding the use of the onboard computer; or have known features been reverse-engineered?

bobm..........

 

This thread over on MINI2.com shows how to get quite a bit of information from the computer. This thread shows some readouts from those tests. I am pretty confident that section 1.5 shows the ECU version number, but I haven't found anyone that has successfully deciphered what the number translates to. It may be internal reference codes that only the dealers know about.

 

I spoke with my dealer in Oklahoma City this afternoon. They said that they were supposed to get version 38 software on Tuesday the 29th. I made an appointment to have it installed on Thursday, 1 July. I'll let you know how my car reacts to the update.

 

After installing a 0.040 inch restriction orifice in the vacuum line on the SCBPV and after about 30 minutes of testing, the yoyo is much improved. That said, if I try to find the right partial throttle condition I can induce it in 1st gear and slightly in 2nd. It is much better though. The key will be whether I can forget about it while driving. Next week will tell. If this proves insufficient, I might try a smaller diameter that gives the BPV about a 200 ms step response, something with approximately half the cross-sectional area.

Regarding driveability: I don't notice a change from before wrt onset of boost, level of boost, throttle response either faster or slower than before. The main difference is that I don't feel the previous level of pulsation under the most common condition of acceleration - partial throttle (at least for me ).

 

Hi, I have a car with the Yo-yo. It isn't too bad and I can usually get around it by accelerating more aggressively (which is more fun anyway).

Is v38 something you would recommend for the average driver with a sometimes present yo-yo? Or would you recommend that unless the yo-yo is really bad that we should wait for a different version?

Are the problems with 38 things that I will be able to detect in normal day-to-day driving? I don't race and I am not a really a redlining person (a shame, I know).

My car is going in for it's first service on the 1st and I am trying to decide whether to get it flashed or to wait for something better. My car is a Sept built 04 stock MCS that was delivered to the VPC in mid October. So I am guessing it has v. 36 currently.

Basically I don't want to make my car worse and I am not familiar with more of the technical stuff talked about on this thread. A better cruise control would be nice however. But I don't use that function much.

Also, I don't want worse gas mileage. How has your gas mileage been recently? Does v38 seem to make it worse or has that not been concluded yet?

Thanks for your help!

 

My fuel economy since V38 inception has been virtually identical to V35 and V36.

As for updating software, the general rule of thumb is: if the car is exhibiting negative characteristics, get it updated. V38 certainly will not hurt, and will definitely improve at least a few aspects of the vehicles operation. Overall, I still recommend it over all previous versions.

 

Owners;
I am new here, and a new Mini owner #TD85945 build date 03/04, my car has < 3kmiles and have suffered the Yo-Yo effect since I first got the car in June. I live in New Mexico and purchased the car in AZ, it took awhile before it was shipped to me.
At first I thought I was a bad driver then I realized many others have the same problem. I have the usual symptoms; under moderate acceleration starting at low rpm’s about 1.8K till about 4K (have not really revved it much) the car Yo-Yo’s. With passenger/s it is particularly pronounced. When trying to accelerate rapidly and smoothly without punching it, in 2nd gear it is very aggravating and I have to say very disappointing.
Read through most of the threads regarding this phenomenon, trying to make sense of it all, and feeling rather helpless because I don’t know what to do.
I understand the WORKS modified cars do not suffer the Yo-Yo and would gladly do the mod if only I had the money and if the boss at home would allow such an extravagant expenditure.
The v38 upgrade is supposed to fix the problem but to my understanding this is not the first ECU upgrade addressing this problem. Another issue is I live in NM and don’t want to drive all the way to AZ for a non-fix.
The car is what I wanted and expected, all except this dreaded Yo-Yo effect.
What is / what will be the fix?
Is there a petition to BMW for a fix?
Sincerely
Ron

Just as I was writting my little note and noticed you had posted, anyway is there an orginized petition to BMW for a permanent fix or are we to sit like lambs awaiting for the next...
Can the ECU chip sent in or do I need to take the whole car?

 

Rajron-

The Yo-yo is present in JCW modified cars. JCW uses the same software as the standard MCS. My Works car will get the new v38 flash as soon as it is available at my dealer.