performabuilt

iTrader: (25)

Bear in mind that while the shift may be commanded at 5100 it could indeed take to 6200 for the trans to make the shift . You see while the electronics are instant hydraulics are not and several things come into play.

One thing is a constant at WOT it always takes the same amount of time for the trans to complete the shift. This time will of course vary from trans to trans depending on condition, Shift kit set up. Line presure and as long as this stayed constant at WOT with the PCM this would hold true.

What does change is the rate the RPM are climbing under various conditions. These numbers are off but bear with me.
Lets say it takes 1 second to complete a shift from 1-2 and at 340 hp NA the RPM climb 300. Ok same time period at 600 hp the rpm might climb 600 RPM during the same period. Other variables would be for instance gear ratio and engine with 4.10 gears behind it is going to climb in RPM much faster that lets say a 3.23 would so then again you might have another 300 or more increase in the RPM during the same time frame between the two gears.I think this is why many times you hear of people boucing limiter after going to lower gears even though they did set up the PCM for the gear change. They failed to compensate for the RPM rate increase. With the stock converter and stock power the PCM can adapt but once you get outside those it cannot do so on its own. Add a shot and the RPM rate increases again even though the time for the trans to shift is still a constant.

I think this is why you hear so many people talk about bouncing the rev after mods they changed something wether it be power or gearing that changes the rate of the rise and fail to realize that all of these things have to be compensated for. Its not as simple as I want it to shift at 6000 rpm and set it that way because to acheive and actual shift at 6000 RPM where you would actually have to command the shift would be different for virtually any mods you make that can affect the rate the RPM rise during the shift.

So realistically every car would be different depending on the POWER/GEAR RATIO/SPRAY.
Then a converter with a high stall is still a further complication and the RPM due to the slip in the converter may be higher that expected for the MPH and this again would vary again with the addition of power adders such as Nitrous or even rear end would affect this too.

So the conclusion I have come to is there can be no one size fits all when it comes to tuning for shifts it would be unique to each set up. A car with 4.10 might take 500-800 or whatever to complete and shift and a 2.73 car might do it in 200-400 and power adders change these numbers around more. So its kinda a trial and error system I would conclude would have to be used.

Also you have to beware looking at the shift completion times with the 4l6x units since the PCM uses the engine rpm verse output speed to determine when the shift did happen and with a stall these numbers can be way off so are useless. The exception would be the late 4lxx with the input speed senor 07 up with these you would get a true time since the converter is not part of the equation.This would be true of the 4l80e also since it does have input speed sensor.
Ramble over lol

wait4me

iTrader: (10)

Sometimes, the ecm is the reason for it hitting a rev limit. As the faster you accellerate the lower it makes the rev limit. Causing the same issue. You need to log your Actual rpm vs shift.

Im talking 2005 up stuff. There is a table we need to change to get rid of that. Then all is good.

jimmyblue

iTrader: (11)

I would think that the changes in temperature
and viscosity, would result in a different pressure
at the "business end" even if a constant pressure
were maintained at the regulator (EPC / force
motor). And you can see in many force motor
tables that the current is messed around w/
trans fluid temperature; whether GM got it right,
(got -what- right) is a question.

Then you have the foot-race between the
commanded line pressure at WOT, and the motor
torque, deciding how soon the frictions will go
from slip to stuck. That torque is environment-
variable and the engine torque model accuracy
that drives the commanded line%, fuggedaboudit.

I like a force motor profile and shift pressure
table that has line% all in by 300lb-ft, and force
motor current zero (I think I give it 10mA just to
keep it toggling) from ~80% commanded on out.
And ditch that stupid "blowoff" value in the 100%
column, make it low like the rest of the upper
end.

At least you can get it to consistently "give it all
she's got"; just don't leave it so you're still tickling
her when she wants the full salami.

Alvin

iTrader: (2)

If you know torque converter slip near the slip which is pretty easy to calculate you can back out an appropiate shift point that will work out really well. it has to meet two qualifiers most of the time, sometimes its only RPM based or only MPH based but most of the time both have to be met. One you figure out what MPH at the RPM you want to shift at lead it by a couple hundred RPM and make sure the shift RPM qualifier is met and you'll be golden.

DaveX

For my car, how accurate is shift rpm reporting? This is what I go by. I dropped all the WOT MPH shift points by 5 mph so I only adjust desired RPM to change shift points. Commanded vs actual always seem very close.