04-22-2020, 03:55 PM | #67 |
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I would be hesitant to tune this out (if its even possible) without knowing why BMW engineers did it in the first place. They no doubt felt this issue during their own tuning/driving and chose to leave it in....
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04-22-2020, 04:02 PM | #68 | |
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I'm of the opinion that BMW engineers left it in from DME tuning other less highly tuned cars in an attempt to reduce the amount of stress on the drivetrain if the shift is done badly. I also find it funny that many people believe that manufacturers of products have done a huge amount of testing. Yes, they do a lot of QA testing, but it's focussed mostly on longevity, emissions and safety. I work in a completely different industry, and I know that so many things get found by the aftermarket enthusiasts that we just weren't aware of or didn't have time to focus on. I also believe that because DCT is seen as the more advanced transmission, and sells more globally than the 6MT, especially in Europe, the 6MT is something of an afterthought when it comes to tuning, both from BMW and from aftermarket tuners. The DCT is unquestionably, undoubtably faster, so if you're a tuner going to build a fast car, why would you focus on daily drive ability of 6MT... Having said that, any time you tune your car, you inevitably risk parts wearing faster and / or breaking. That's a risk I'm happy to take in this case, even if it means that my turbo dies early; I wanted to upgrade it anyway!
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04-22-2020, 11:53 PM | #69 |
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[QUOTE=Nezil;26083209]They also left in the clutch delay valve, which only makes shifting rough with 6MT.
Agreed. BMW engineers good cars, generally, and the M2 is no exception. But they are not perfect, and mods will improve them. Nezil is looking for a needle in a haystack, but he's relentless about improvement, and I admire his tenacity. And, since I have a 6MT that I've tweaked considerably as well, including particularly the shifting experience, I'm hoping to profit from it eventually.. |
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04-23-2020, 12:05 AM | #70 |
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Some say I'm a pain in the ass, my wife says I'm tiring... I don't mind, I can't change how I am and I get a huge sense of achievement if I'm successful!
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04-30-2020, 10:30 AM | #71 |
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Hey Nezil, have you seen this from Dinan? It's their new (non-M2) N55 flash. The only reason I thought it might be of interest, maybe, is that near the bottom of their features bulletpoints for this flash is "no hesitation between shifts." It might be worth a follow-up with them to see whether they have addressed your issue in their recent tune...
https://www.dinancars.com/products/s...V1utY2xZDIA7K4 |
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05-01-2020, 06:18 PM | #72 | |
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05-01-2020, 06:22 PM | #73 |
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It's too early to give a conclusive report, but I can say that I'm already seeing a massive improvement in the maps I'm trying with the tuner I'm working with.
Not only is the waste-gate behaving correctly after the shift, but boost is even being held for a short time between shifts. It's not 100% consistent yet and more work needs to be done, but the feeling of a shift when it all comes together is incredible. It truly feels naturally aspirated, and I'm confident that it would be much much faster than a typical 6MT car that needs over a second to build boost between shifts.
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Current Performance Mods: CSF FMIC, ER CP, Fabspeed Cat, Aquamist WMI, GFB DV+, NGK 97506, BM3 (Stage 2 93 OTS), CDV delete, UCP, M2C/M3/M4 Strut Brace, M3/M4 Reinforcement Rings |
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05-02-2020, 03:35 AM | #74 | |
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Is your tuner on the bm3 platform? Be great if so as it'll be easier to share the tune (or variations of it) once sorted. |
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05-06-2020, 08:33 AM | #75 |
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I've just read through this full thread and tried to follow along with the log graphs posted. I 100% agree that there is an artificial lag induced by the ECU when you don't shift at redline. I too have been playing around with driving styles since I got this car 4 years ago and it is my single biggest disappointment with this car.
Shifting quickly at a 5500 RPM shift gives the clunky-ness associated with the rev-hang. A slightly longer shift can be smoother, but in either case there is a huge lag when getting back on the throttle. More than just turbo-lag, which can be measured by simply going to 0% throttle and then back to 100% in the same gear. Thinking it was safety (traction) related, I've tried DSC OFF and it performs the same way. I, too, am convinced the lag is to protect the drivetrain. The only way I've experienced no lag is a quick shift at redline with DSC off. It's to the point that I don't enjoy daily driving the car and have considered an E36 or E46 for more daily enjoyment (both of which I've owned before). I applaud all of the work Nezil has done here and it is the first thread that really tries to use data to get to the root of the problem. If a fix is discovered I am on board. One question though - If SeanWRT suggests that the lag may be introduced on the 6MT to prevent overboost because of turbine speed and a drop engine RPM, how does the ECU on a DCT live with that with instantaneous changes in engine RPM? Seems that would only make it worse..? Last edited by Nick2016M2; 05-06-2020 at 09:14 AM.. |
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05-06-2020, 04:07 PM | #76 | |
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05-07-2020, 06:06 AM | #77 |
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The principal here is that engine RPM = Flow and turbine speed = flow. With a sudden change in engine RPM, you have a sudden decrease in engine airflow. With the turbo spinning at the same turbine speed this would create an overboost. Unless it is quickly regulated at the point by the wastegate. My point is: If the wastegate can react that quickly on the DCT, why does the drivetrain need to be babied so much in the 6MT?
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05-07-2020, 06:22 AM | #78 |
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Have to look at it with PID tuning in mind:
https://www.google.com/url?sa=i&url=...AAAAAdAAAAABAY The chance of overshoot error where turbine speed drop is minimal during DCT shift is small since you are not far from steady state (desired full boost). Large loss of turbine speed during *most* manual shifts requires significantly faster response time and thus higher chance for error over target during rise. It's much easier to control steady state error when closer to steady state. |
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05-07-2020, 09:10 AM | #79 | |
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05-07-2020, 02:09 PM | #80 | |
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05-07-2020, 02:18 PM | #81 |
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A lot of talk on this topic which is great... I'm happy it's getting attention because I too agree with these statements:
It actually shocks me that no other 6MT N55 or S55 owners have picked up on this issue. Anyway... I'm pretty sure that a tuner doesn't want their 'secret sauce' spread about, and I have no intention of doing that with the tuner I'm working with, even if they were to tell me... which they're not. What I will say though, is that the N55 in the M2 (and probably other vehicles) has two ways to control boost pressure... one somewhat crude way, because of latency etc. is with the waste gate and the diverter valve. The other, which is the way BMW does it typically, is with the throttle plate. If you take a look at logs of the manifold MAP sensor vs the pre-throttle MAP sensor there are times with the stock map that the throttle plate closes to control the pressure in the manifold, causing the pre-throttle pressure to increase. With a stock charge pipe you may not want this to happen because any spike in pressure here could cause it to fail, but with the aftermarket charge pipes most of us are using, a boost spike can be tolerated by the engine (by using the throttle plate) and by the charge pipe (because it's uprated).
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05-07-2020, 06:00 PM | #82 | |
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05-07-2020, 06:06 PM | #83 | |
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I was also making the point that it's definitely worth doing. I can say for certain that when it does work, the feeling of throttle response and performance is massively improved.
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05-07-2020, 06:45 PM | #84 | |
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05-07-2020, 06:47 PM | #85 | |
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My personal feeling is that working on this is more important than working on power for a 6MT car. For DCT I totally understand that this wouldn't have even been considered, but for 6MT, having more power only makes the delayed feeling more apparent and annoying.
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05-08-2020, 03:30 AM | #86 | |
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05-08-2020, 01:47 PM | #87 | |
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Prior to my 2017 6MT M2, I had a 2015 6MT M235i. I bought it at 5k miles and had no idea it was tuned until about a year of ownership, when the dealer pointed the JB4 to me. That car had at minimum a new charge pipe and downpipe as well. It may have had an intercooler. I ran the JB4 bypassed, Map2, and Map5. That car NEVER lagged between shifts the way my M2 does. Power hit hard every time regardless of RPM or shift speed. It was noticeable immediately when I bought the M2 on the 200+ mile drive home from where I purchased it. It has driven me crazy ever since. I’m glad people are working so hard to find a solution... because the M235i was much more violently fast. Now, this could be the JB4 software making a change that overrides a BMW setting. It could also be that the unrestricted flow of the catless downpipe made some sort of impact. But there is no doubt a difference, somewhere in the chain. |
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05-08-2020, 04:54 PM | #88 | |
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