street testing 1/4 mile runs, have trans questions RPM's

uncle don · 11-21-2019, 08:49 AM

took car out this morning for some 1/4 mile runs on our local "strip"

DTC off, car in manual mode, starting out in M1, shifting about 6000-6500....wow it ran good...for stock anyways. didn't hesitate, didn't surge, pulled hard.... big difference from leaving it in normal automatic drive.
so what would this test tell me? something up with the trans if its surging and hesitating in normal automatic mode? but not in manual M1-M6 shifting myself? weird.
only thing I did notice when manual shifting is between gears the cars RPM's would drop significantly, like 1,500 rpm's...for example between each gear I would shift at 6500 it would fall back to around 5000 rpm's.... is that normal? can I take that lag out with tuning? on my turbo buick cars grand nationals etc...the rpms fall very little if any between shifts...or my wifes mustang gt doesn't fall rpm's either...
any thoughts on above??? thanks guys.

matamua · 11-22-2019, 11:00 PM

Quote:

Originally Posted by uncle don

took car out this morning for some 1/4 mile runs on our local "strip"

DTC off, car in manual mode, starting out in M1, shifting about 6000-6500....wow it ran good...for stock anyways. didn't hesitate, didn't surge, pulled hard.... big difference from leaving it in normal automatic drive.
so what would this test tell me? something up with the trans if its surging and hesitating in normal automatic mode? but not in manual M1-M6 shifting myself? weird.
only thing I did notice when manual shifting is between gears the cars RPM's would drop significantly, like 1,500 rpm's...for example between each gear I would shift at 6500 it would fall back to around 5000 rpm's.... is that normal? can I take that lag out with tuning? on my turbo buick cars grand nationals etc...the rpms fall very little if any between shifts...or my wifes mustang gt doesn't fall rpm's either...
any thoughts on above??? thanks guys.

I honestly don't know, but it sounds about right. I'll check mine out in the next few days and let you know what I find out. Either way, I cannot think of a situation in which the transmission would cause bucking/surging...slipping may be one thing but to me that is a different feeling. What you are describing sounds like more of a ignition/fuel/motor kind of thing to me.

With respect to trans tunes there are two that are commonly used, the Alpina flash and the xHP flash.

Alpina is a coding thing and apparentlyeither very low cost or free. People seem to think the D mode is "underivable" whereas the DS mode is great.

xHP costs like $250 and you flash similar to MHD. There are three maps from the tame to the not tame. People seem to like it better.

matamua · 11-24-2019, 01:08 AM

So I checked it out under a few different circumstances. These are all eyeballed and not scientific.

In "D" mode, pedal to the floor:
-drops by nearly 2000 from 6750 at redline to 4500 on each shift

In "DS" pedal to the floor:
-drops by a little less, maybe 1750 to just under 5000

In manual with paddles and traction nannies off:
-drops to 5000, but a little inconsistent depending on where I hit the paddle.

In summary, I think the drops you are describing are in the ballpark of normal. I don't think that it is normal behavior to stay at the same RPMs right after you shift, if this was the case, you'd be going right into the next gear, because that's how transmissions work.

uncle don · 11-25-2019, 08:31 AM

thanks matamua....great answer. appreciate that. helps me feel a little bit better about it now. I may try one of those tunes mentioned above to help it out some. just trying to get it perfect before I take it and get some stock times on it...id really like to break 12's bone stock...that's my goal

.

11-21-2019, 08:49 AM	#1
uncle don Private 2 Rep 50 Posts Drives: 2007 335i E90 auto Join Date: Jan 2016 Location: elizabethtown, ky iTrader: (0)	street testing 1/4 mile runs, have trans questions RPM's took car out this morning for some 1/4 mile runs on our local "strip" DTC off, car in manual mode, starting out in M1, shifting about 6000-6500....wow it ran good...for stock anyways. didn't hesitate, didn't surge, pulled hard.... big difference from leaving it in normal automatic drive. so what would this test tell me? something up with the trans if its surging and hesitating in normal automatic mode? but not in manual M1-M6 shifting myself? weird. only thing I did notice when manual shifting is between gears the cars RPM's would drop significantly, like 1,500 rpm's...for example between each gear I would shift at 6500 it would fall back to around 5000 rpm's.... is that normal? can I take that lag out with tuning? on my turbo buick cars grand nationals etc...the rpms fall very little if any between shifts...or my wifes mustang gt doesn't fall rpm's either... any thoughts on above??? thanks guys.
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11-24-2019, 01:08 AM	#3
matamua First Lieutenant 81 Rep 359 Posts Drives: 2007 e93 335i, FBO, m3 control Join Date: Jun 2019 Location: USA iTrader: (0)	So I checked it out under a few different circumstances. These are all eyeballed and not scientific. In "D" mode, pedal to the floor: -drops by nearly 2000 from 6750 at redline to 4500 on each shift In "DS" pedal to the floor: -drops by a little less, maybe 1750 to just under 5000 In manual with paddles and traction nannies off: -drops to 5000, but a little inconsistent depending on where I hit the paddle. In summary, I think the drops you are describing are in the ballpark of normal. I don't think that it is normal behavior to stay at the same RPMs right after you shift, if this was the case, you'd be going right into the next gear, because that's how transmissions work.
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11-25-2019, 08:31 AM	#4
uncle don Private 2 Rep 50 Posts Drives: 2007 335i E90 auto Join Date: Jan 2016 Location: elizabethtown, ky iTrader: (0)	thanks matamua....great answer. appreciate that. helps me feel a little bit better about it now. I may try one of those tunes mentioned above to help it out some. just trying to get it perfect before I take it and get some stock times on it...id really like to break 12's bone stock...that's my goal .
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