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Cobb - torque limit active 4 / which limit tables to raise?
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11-26-2013, 10:31 AM | #1 |
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Cobb - torque limit active 4 / which limit tables to raise?
I've been dealing with low / negative timing especially in the higher gears. These are the flatlines where no timing corrections are logged. These have a high correlation with the torque limit being active. When I log this channel and it shows 4, timing drops down even though no corrections are logged.
**** Has anyone identified all the limit tables that impact the torque limiter? And if so what values are you raising these tables to, to get this nanny fully out to of the way? **** My experience so far: What I have done is raise the load targets, reduce the boost limit multiplier and REDUCE the load to torque limit table. This effectively all but eliminates the torque limiter. It keeps the load target (limit might be a better label) out of the way and allows me to still control boost. I believe the load to torque table tells the DME what amount of torque to report for a given load/RPM. I think the word "limit" in the label of this table is confusing. In my opinion, its more of a lookup table and not a limit table. If the amount of torque reported exceeds the limit then timing starts to suffer in the DME's attempt to reduce torque. The unwanted side effect is that when you reduce the load to torque limit table the car thinks its pushing less torque and then you get funky shifting and a lose torque converter cause it thinks its running less torque then it really is. This can't be good for an AT car. The TCU is then being feed false torque numbers. I've now gone back to OTS values in the lower RPMs and lower loads but left the reduced values in the 3 highest load rows / middle and upper RPMS of the load to torque limit table which got it shifting normal when not pushing the car hard but still mitigates the timing drops at the higher loads / RPMs. Its working well but still less than ideal in my opinion. Rather than tricking the car and telling it that its running less torque than it is, I think the better solution would be to just raise the torque limits on all corresponding tables. This way the DME and tranny know full well how much torque its pushing, and do what it can to handle (but not reduce), the actual real amount of torque. And at the same time the limiter is out of the way and power does not get reduced.
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11-26-2013, 12:43 PM | #3 |
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I'd have to pull some logs. I'm swamped at work now. 5th gear will flatline literally at any MPH on the OTS map. The target load on the OTS map where it flatlines is I believe 186. Whereas on my modified map I set the target load at 214. Again boost limit multiplier is reduced on my map so I'm still running about the same actual boost and actual load in my modified map as compared to OTS.
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11-27-2013, 05:05 PM | #4 | |
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There is a calculation in the load the TCU does not like and then starts pulling timing. There is consensus that its calculated torque from what I have read and have been advised from other sites. Usually when hitting 5th gear @ WOT you should be at 120ish MPH or getting there. I would suggest going to the Requested Torque (Drive) table. Reduce column 50.00, 80.00, 100.00 on the last cells for 124 mph by 20% Highlight the 3 cells > Press the M key > Enter 0.80 > Press Enter. I would also suggest going with a lower load for starters. Have your load start declining from 4300 RPMs. So the two cells for 4300 - 5000 rpms start with 178.00(@ 4300 RPMs) and 175.00 (@ 5000 RPMS) etc We didn't get a chance to test this out yet cause its been raining the last few nights here in south Florida and now we need to replace an injector |
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11-27-2013, 06:53 PM | #5 | |
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I just had a huge breakthrough with the Load To Torque limit table!! I believe the word "limit" in the label to this table is very misleading. I think its really a lookup table that tells the car what torque to report for a given load / rpm. I only had to lower the bottom right cells in the 2 highest load rows from 3,000 RPM up. I don't love the idea of "tricking" the DME and TCU with lower than actual torque, but the areas I modified really only affect WOT in the mid and high RPMs in the gears that produce the most load. I'm sure the tranny is locking the torque converter shifting as firmly as it can at reported torque levels below the OTS values and my lowered values in these high load rows. I don't think there will be any negative side effects but I can't say for sure. So far so good. I wish we could just raise the torque limit and get the nanny completely out of the way but it seems like for now we have to get creative with workarounds. This works great and I now log 0 in the torque limit active channel and don't get timing flat lines!!! I have a more detailed post on the "other" site so I can't post the link. Its post #38 under the thread titled: " Is there a practical solution to the IJEOS timing flatline (flash only)?"
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11-27-2013, 08:33 PM | #7 |
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@mfish123
Yea will continue on the "other" site with this. There is a con to both of them but I think it would be how you would like to eat your cake |
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11-27-2013, 08:54 PM | #8 | |
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11-27-2013, 09:19 PM | #9 |
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11-27-2013, 09:56 PM | #10 |
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11-27-2013, 10:26 PM | #11 |
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11-27-2013, 11:05 PM | #12 |
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11-27-2013, 11:14 PM | #13 | |
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I'll be replacing the faulty injector tomorrow and we'll test BuraQ's approach. Lowering load results http://datazap.me/u/bimmer305/e50-atr-map-r73-5?2-17-22
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11-28-2013, 01:59 AM | #15 |
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Not really.
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11-28-2013, 02:36 AM | #16 | |
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Whatever works for you then that would be the best way. Last edited by BQTuning; 11-28-2013 at 02:48 AM.. |
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11-28-2013, 10:56 AM | #17 | |
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In my situation 5th gear is the most affected but occasionally in 3rd, 4th, and 6th I'll also momentarily hit a high enough load to trigger the torque limit. So I think with my method of lowering the calculated torque I don't have to worry about it in any gears. Also, on the highway when going much less than 124 mph I sometimes downshift just to 5th to get a little extra passing power and will still sometimes trigger the torque limit between 60 - 100 mph. I don't always need to pass in the lowest gear possible at WOT with a neck snapping downshift. For me sometimes its nice to get a nice little undramatic smooth downshift to 5th to get the engine spinning just enough feel the strong torque. I want this situation protected from toque limitations and resulting low or negative timing. I've seen my car hit the torque limit as low as 3,300 RPM's in 5th gear and I think maybe even pull timing at even lower RPMs so I think what I'm doing might suit me well for street and highway use. Whereas the other method may be the better option to keep the workaround only active when almost redlining 4th and then up shifting to 5th. Granted if we're really aggressive on the streets (in Mexico of course!) we may get into that situation but probably more of a situation that would be seen on the Autobahn or a track.
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Last edited by mfish123; 11-28-2013 at 12:30 PM.. |
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02-05-2015, 11:26 PM | #18 |
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good info here
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02-06-2015, 03:33 PM | #19 |
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Hi mfish, great discussion you've brought up. Very recently this was discussed in another thread where we explained to those involved why this approach to what you're doing is only a workaround and not an actual fix for the issue at hand.
The proper fix is to raise the torque limit handling on the TCU side so that higher and more appropriate torque values can be reported to the TCU for line pressure management. That is currently only doable via an Alpina TCU flash and only available to post-March 2007 6AT cars. The flash unfortunately has some daily drivability drawbacks that some people would rather not deal with and it'd be great if the tables for it were available for calibration but they're not and it is what it is in terms of TCU calibration, today. Bringing down torque request or load request will only lower your requested boost which isn't what you want to do when pushing power and keeping DME boost safeties in mind. If you go down that road you'll be pushing duty cycle on the wastegates harder to hit boost targets while desensitizing the DME overboost throttle safety mechanism and possibly eventually removing it entirely which can/is risky business to those concerned about safety of their motors.
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02-07-2015, 09:56 AM | #20 |
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The Alpina TCU flash does not fix post-shift flatline on the IJEOS.
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02-07-2015, 11:36 AM | #21 |
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There are various issues that can affect timing at various load vs rpm areas. Alpina TCU flash is certainly a fix for one of those issues. Post shift timing corrections will not be adressed in any way by Alpina TCU flashing as all that is doing is raising torque limits at the TCU. Same IJE0S ROM on a 6MT will never run into the issue that the 6AT cars run into. Feel free to email us at any time to discuss further if you like and we'd be happy to help.
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02-07-2015, 11:57 AM | #22 | |
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cobb, flatline, load, timing, torque limit |
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