OK I posted a request for suggestions and help re the 5000 rpm yo-yo question New kind of yo-yo?, plus an earlier attempt at looking for help re
YO-YO at 5000 rpms!?!? Suggestions??

I thought it was weird, or I wouldn't have asked. But is it that weird?

Well over 100 views and not even a single reply or suggestion?

Should I have worded it differently?

Should I have posted it in Beneath the Bonnet?

C'mon gurus! What are your words of wisdom?

 

You wrote:

Anyone ever heard of a pronounced yo-yo at 5000-5500 rpms at part throttle?

Most people are not going to respond with "no" as that makes no sense. Your looking for a yes

When someone has, I bet they answer. GIve it time

 

Thanks, chows4us.

Since there've been no suggestions, I'm starting to think I'm alone in this one.

 

Is it under full throttle or lift off or what?

-Brian

 

Ive never heard of this, and I go through old posts like crazy.

 

OH NO!!!

It's the power of suggestion. Everyone who reads this will start straining all their senses from 5000-5500 to detect even the smallest of flutters.

Eventually, someone will notice it...
... and then you won't be alone any more.

 

what is this? what is a yo-yo? (i know about the toy)

 

Yup, I was 1 of the 100. Just needed to think about it.
Does the tach look like it had a few too many?
In the other post you mentioned you just had a new tune for a Unichip? Yes? If so does the car act the same with the OE?
Does the Yo Yo happen at 5k in every gear? If not it could be in the drive train while the car is at speed. On tight twisties this may not be an issue, breaking, accelerating would hide some drive train problems.
Another possibility could be a bad BPV that indeed had a few too many, it is the season.
That's about all the wisdom I had stored up. Need more input

 

Just like the toy, only harder to figure out.

All Minis don't have this. The ones that do act like they are searching up & down for the right mixture. If you do a search there are some good threads on the sublect here on NAM. Since this is not all that common BMW does not have a cure, to my knowledge. Some software upgrades have cured many Yo Yo cars. The latest upgrade has cured at least 2 friends cars that I can think of.

 

From the earlier posts. Hope it's not too much detail:

It happens at part/half throttle. TPS (Throttle Position Sensor) between 43-48, especially noticeable in 4th or 5th gear, but also 3rd. I use a ScanGauge II, so I can see the TPS, Intake Air Temp, Manifold Air Pressure in lbs./sq. in., Ignition Advance, Water Temp, RPMs, Battery Voltage, etc.

It seems that the only repeatable trigger is the constant TPS between 43-48, typically in 3rd-6th gears. Also seems to begin about 5000 rpms, in 3rd, 4th, subsiding around 5500, but in 5th or 6th, it'll start at 5000, and continue up to almost 6000 rpms.

The car's typical whine when accelerating (Alta CAI) is interrrupted by a quick on-of on-off cycling action. As long as the throttle position stays relatively constant between 43-48 TPS it'll exhibit this lack of smooth acceleration until I hit 5500-6000 rpms.

It's as if the car is leaving and then re-entering a closed correction loop or something. I estimate it happens about twice/second. It's a funny whine/no whine sound, while the car pulls and hesitates in synch with the sound.

At one time I suspected the belt slipping, but that was before inspecting it and noticing the definite spot where this "yo-yo" occurs.

If I apply stronger throttle, or full throttle (TPS 88), it won't do it.

Easier to notice in higher gear, such as 4th and above. Trouble is, when testing it, by this time, the speed is, ummm, a bit higher than I might use for highway driving...

I wondered if it might be the recent retune of my Unichip to address the afr in colder weather. But when I switched to the older map, it still exhibited the same problem.

Re the engine, I have insulated Alta CAI w/boxtop, 15% pulley, 2% crank, m7 DFIC, m7 400 cc injectors, m7 intake runners, m7/Cosworth head, Schrick cam, NGK one range colder (did have two ranges colder, but had some "random misfire" codes in colder weather, eliminated with going back to the one range colder NGK), latest Unichip.

OEM header/cat, but ceramic coated. Milltek exhaust.

Re gearing, this is an 06. I also use lightweight 15" wheels with 205/50-15 tires for street use.

All these have been on the car since I bought it new, back in the summer. Installed at the 1250 break-in point.

When I auto-x, or play in the twisties in the GA mountains, it's usually OK, because they aren't generally part (half?) throttle applications. But you'd be surprised how often this happens on the interstate. I'll just step on it a bit to pass without downshifting, the car steps out nicely, and then, yo-yo-yo-yo...

All that being said this car is strong and pulls authoritatively (SpiderX and Gr8Force have commented to this effect from their firsthand experience).

Car pulls smoothly and strongly through the dreaded 3000-3500 rpms range (although it took several Unichip tunes & tweaks to get it just right last summer).

Just as long as I don't let it drop into that yo-yo twilight zone...

 

Still need to know if the car does this with the OE without the Unichip?

 

I went back to the second Unichip map from the summer which never exhibited the problem.

It does it now.

I have not removed the Unichip.

 

Have you considered the Vaccum Gain System, sounds like it would cure this for about 30min, and 3.50 in parts? Sorry can't give much info as I don't have the chance to romp around 4th-6th gears much in these parts, I'll see if I can hold it around there in lower gears and notice anything (took the VGS off 10k miles ago, just for kicks)

 

No guru here, but I've never had this through 3rd, 4th or 5th. Remove Unichip for S&G's?

 

I would try disconnecting the Unichip like everyone has said.

Sounds like a bypass problem when you decribe the on/off s/c whine. Maybe a vacuum leak? Have you messed around under the intercooler latley?

-Brian

 

Actually, I put the Alta silicone boots on the DFIC about three months ago. They would/could leak, so we kept messing with them.

Harrison Motorsports (BMW/MINI service center here in the Atlanta area) did a smoke test on the system to see if there were any more leaks. They were their usual thorough selves. We couldn't find any.

Peter has sent me his silicone m7 DFIC boots, so I'm waiting to install them when they arrive. In the interests of checking one thing at a time, I'll see what happens after they get installed (reportedly a much better fit for the application).

But if it's a leak, why would it disappear at lower throttle applications, as well as at full throttle?

The ScanGauge II may not be fast enough for me to watch for a boost variation when this is happening. I'll try setting it to it's fastest setting. Do you think the manifold air pressure would show up as unsteady with this yo-yo? Not sure what it'd tell me though, since it shows full boost under heavy throttle.

If I get a chance, I may try to bypass the Unichip this weekend. But if nothing changes, I'll put it back for the m7 silcone boot install next week, in order to keep a simple path for checking this out.

Guess I was kinda hoping someone else had noticed this phenomenon since there's probably a lot of cars with my general set-up.

 

It's too fast for the tach to show much.

As I replied to Brian, I need to bypass it fully just to be sure. But it kinda reminded me of the old yo-yo, which the DT BPV seemed to help.

I'll just say it's easier to see and notice in progressively higher gears. If it's happening in first or second, it's swamped by other noises and stuff happening...

Would the BPV be in play at half-throttle at 5000 rpms?

 

Hornguys,

I am experiencing the exact same thing with my wife 06 MCS.

Mods:

Mini-madness 15%
Myminiparts intake (ITG filter)
JCW exhaust
GIAC ECU tune

Like you, only happens at partial throttle, not at WOT and it started happening the day I installed the pulley (no GIAC or exhaust then)

I thought it might have something to do with the belt since the tensioner was not showing any holes. I switched from the stock belt to a Gatorback 060537 (53.75) and it's still happening even though the tensioner is showing enough tension now.

Did you ever resolve your issue?

 

Sorry LoF, I can't help on this one for you.

It was the Unichip.