I've noticed recently when I give the car a little gas, maybe 1/2 throttle, in first and second gears from 3 to 4k it seems like the car lags a little bit. Anyone know why this might be?

 

I have a similar problem with my car. It has MTH Tuner file and 380cc injectors. It has a distinct lag/flat spot from about 2800rpm to 4000rpm when using part throttle. full throttle seems to be OK.


Do you have MTH?

John.

 

Large bore TBs have a tendency to exaggerate this effect. The flat spot is representative of a very lean condition. What mods do you have?

 

On my car I have:

19%
CAI/ silicon hose
Alta Diverter
NGK Iridiums
380cc Bosch
MTH Tuner

Tried swapping around some MTH maps today and found my original MTH "non tuner, non 380cc" got rid of the flat spot along with a lot of power

The tuner file is night and day better than the standard MTH as far as performance goes but this flat spot is annoying.

I havent talked to Franz yet as i have been ruling out all the other possibilitys before I contact him.

Looks like I will have to talk to him after his Vacation.

John

 

You both have the YoYo (trust me...) Read the extremely long thread called the YoYo chronicles. Or read my posts on how I described my problem, then solved it with the VGS mod. I can almost guarantee it will solve the problem.

Now I've heard some people say it masks the problem, but here's the synopsis:
Problem: flat spot, or surging, between 2.8k and 3.5k rpm at partial throttle.
Cause: Either or a combination of i) oscillation between vacuum take-off that controls the bypass valve butterfly and the butterfly itself and ii) a bypass valve that does not close completely due to misalignment at factory.
Solution: i) move the vacuum takeoff further down the inlet manifold. Easily achieved as described in VGS mod. and/or ii) replace or repair bypass valve with Ryephix valve, or DIY adjustment, even though this will keep the OEM spring (read thread on Ryefix valve for more info.)

Good luck!

 

Already adjusted the valve and done the VGS. I never had the yo-yo before or after these mods.


It all started after the 380cc and tuner file went on the car.

 

I am currently working with Volker on some testing concerning the flat spot @ part throttle. As most people have remarked, it doesnt happen at WOT (which is what 85% of MTH modifies, since it goes to open loop operation @ WOT and relies on the tables, not what your O2 sensors are feeding back like at part throttle).

I feel this will be much easier to diagnose than the my cooper's strange 'pulsing' at 125mph. For all I know, it could just be wind resistance building up, then releasing, or... me poking through the space-time barrier.

 

I thought it was just me. I've only had my car three weeks and thought maybe I hadn't learned how to drive it very well yet. Mine has that hiccup for lack of a better word.

 

there is a tremendous amount of help on this forum. do a search for:

1) yo-yo
2) flat spot
3) VGS
4) throttle body

Between those four things you'll find a ton of info re: your problem.

 

THANKS!!! Is this something I should mention to the dealer?

 

If you get a chance to see the matrix that is "the map" you will see that partial throttle and load are part of the criteria. When riding with Josh doing the Unichip tune.....we worked the hardest and longest on partial throttle, mid-band driveability. Josh's comment was that "WOT is easy, we can do that in 10 minutes at the end." We spent the better part of 1 1/2 hrs getting the mid-band partial throttle worked out,....then 10 minutes dialing in WOT. The car runs great now. The ECU gets caught between conditions and doesn't know what to do (my assesment) I went round and round with all the differing mods and this is the best yet.


I know this is limited help...but...hey....I'm no Randy.

 

Unless you have a stock driveability problem that you are trying to correct, why would you want a chip to do anything different at part throttle. If you are at part throttle and you want more power, wouldn't you just push down harder on the loud pedal?

 

You are right as you state it but the issue is a "drivability problem" that shows up when modulating other than WOT.....apparently, in this case, there is one. ....... I have noticed that at under certain conditions, some static...some dynamic that the car gets flat, yo yos etc in the mid band with and without varying loads.....it is annoying to some ... me included... the further applying of the "loud" pedal does not solve the problem..... it is slightly more subtle. As I stated WOT is easier....

 

This is the very same problem I am currently having with the tuner file,
I also have the VGS mod and I also experienced this with the standard file
so Franz sent me another file a while ago and it sorted the problem,
I love the tuner file and the power gain but the hesitation @3k is annoying,
I've contacted Volker and am still waiting on a fix for this.
I have great faith they will sort this out

 

I had a 4500 RPM flat spot only under WOT. It seemed to go away after the dealership upgraded the ECU to the current version and possibly me installing the short ram intake.:smile:

 

Well it has put my mind at ease that I am not the only one suffering this problem and it is a known issue with Franz.

Just hope it can be fixed, as it ruins the driving experience You pull out from a intersection and the car pulls off the line nicely and then at 2800rpm it feels like you have sucked a sock into the intake.

And you cant drive everywhere at full throttle!!!

John.

 

mine has a flat spot around 3k since getting v42.

my car has a 15% reduction sc pulley, alta intake, milltek catback.
the car is smoother off the line vs the pre v34 it had, but that
flatspot is kinda annoying during faster-than-normal take off...
honestly it feels like the old 98 prelude i had in the low lobe
(before it hits VTEC).

 

Seems there is several different problems people are having in this thread with similar end result

Mine is obviously MTH Tuner/injectors related as nothing else has changed on the car and it started immediatly after installing those 2 parts. Some other people sound like they have the yo -yo etc

 

Mine has a flat spot at about 3k as well. I have a 15% pulley and no modded software or TB (I did adjust the bypass valve to close all teh way.) I did the VGS mod and it helped a little but it is still there.

 

ME TOO!!!

My '05 MCS is stock and I was having cold idle/stumble problems as well as the YO-YO. So I went and had the V42 reflash done. Now the car has ALL the old issue, PLUS a very noticable flat spot at 3000 rpm.

If you are used to imports that run properly for 200,000 miles without a single hick-up, DON"T BUY A MINI, or any other BMW for that matter.

It's really a shame. On one hand, we've got these beautiful cars and an outstanding bunch of people to have fun with, on the other hand there's BMW, that apparently could care less if any of us ever buy another MINI.

 

I do have a flat spot at 3K as well with 15%, VGS, Alta IC, bypass butterfly adjusted and Alta CAI. I was hoping that along with these mods that I added on will cure the flat spot, but no..no..it's there. Now I only drive it like I stole it...seen to fix the problem to me.

I use to have a yo-yo before, but now it's gone. I think yo-yo and flat spot is a different symptom and now I got another one called "Hiccup" I can feel it at low speed on first and second gear at 5-10 inHg It's just like the transition between open and close of the bypass valve. Does any of you have this kinnda thing?

 

My '03 JCW S also has the flat spot between 3.2K to 3.5K especially using JCW 210 hp version ECU. Then I changed 370 c.c. JCW fuel injector to M7 400 c.c. injector, it improved a lot, then I changed JCW ECU to Chiptronic ECU, now the flat spot is still there but barely noticable.
After reading all these posts, I think YoYo or falt spot is pretty common problem for Mini Cooper S, no matter what mods you have on car. And '05 is not better than earlier model. What happen to BMW ?

 

[now I got another one called "Hiccup" I can feel it at low speed on first and second gear at 5-10 inHg It's just like the transition between open and close of the bypass valve. Does any of you have this kinnda thing?]


I have noticed that at low speeds (read stop and go traffic) in first and second gear my car will start jerking when getting on and off the gas. no matter how smooth I try, it jerks like I slammed the thottle open and close. It actually seems to get worse throughout the drive until it gets down right embarrassing.

I have also noticed that at 20mph or 2000 rpm in first and second gear the car will momentarily stop engine braking. I'll be coasting, foot off the gas, and right at 2000rpm the car will jerk and almost accelerate for a moment and then continue coasting.

I have only recently notice this behavior now that I have an insaine commute. It is enough to consider another way to work. Anyone else with this coasting thing?

 

Yup, I'm experiencing the same thing on a 2005 MCS with 15% Pulley, ALTA CAI & Silicone Intake Tube & colder spark Plugs. Tried the VGS Mod for a week, got a little better - but not liveable for the typical daily driving that I do. At WOT the MTH software performance is outstanding, and love the low-end torque, but....
1. Removed VGS mod last weekend - no change in the flat spot
2. Then returned to my pre-MTH mapping - flat spot gone and have had a much better daily-driver to enjoy again.

I know MTH is aware of the issue and have faith they will come up with a solution. I miss the power - I now appreciiate the torque previously gained with MTH as I'm more aware how often I now downshift to get into the power range than when the MTH Tuner file was installed.

Sorry to hear you guys experiencing the same, but glad to know it's not just me being a whiner or too picky.

Looking forward to getting it sorted out ~ Thanks for everyone's contribution !

 

Do you have boost gauge? If so can you tell at what vacuum reading when the problem occur? I'm thinking may be a defect bypass valve. I will try to replace the bypass once I have time since it's only $40. The only concern is that my yoyo was long gone and I don't want to bring the same issue back If I replaced the bypass....oh well