thunderstruck507

iTrader: (18)

Something I have noticed when trying to make corrections to the VE and MAF tables is sometimes the 4l60e transmission shifts can get spongy in certain areas, and I have even experienced WOT slipping just prior to upshifts which go away if the tune is reverted.

Can someone better explain the relationship and/or what is going on to cause this? I am under the impression it can be caused if the values for fueling and airflow are too low but this might not be correct.

Would there be an easy way to reduce the relationship between them so that it didn't have to be a concern?

MontecarloDrag

iTrader: (3)

There is a direct relationship between airflow and shift firmness.
By definition, airflow equals to engine load so the more load the engine has, the more holding pressure needed in the trans clutches

You can't expect to have the same shift pressure at low throttle and wot because the trans will shift very harshly at low speeds making it too uncomfortable

There are trans tables where you adjust shift pressure vs tps and speed, you can raise the values to get firmer shifts

ddnspider

iTrader: (26)

There are 2 excellent auto tuning tutorials, one on this site in the auto section and an even better one on efilive's site. There is a pid related to trans engine torque so you can verify that it doesn't go negative. If it does then the airflow model has issues.

thunderstruck507

iTrader: (18)

Thanks, I guess I will just try another run at it and see if it does a better VE correction. I did a nice long log with lots of varied driving and smooth throttle transitions so I was expecting this one to be great.

rpturbo

iTrader: (47)

I believe you are on to something, I have a solid for lack of a better word, slip on full throttle into 3rd. It didn't happen before the tune, and if I back out for a split second, it will shift and hold fine.

ddnspider

iTrader: (26)

Care to post the tune and we can look at the trans tables and stuff?

thunderstruck507

iTrader: (18)

I will try to put it on a flash drive at lunch. It is still unfinished at the moment as I have spots at part throttle cruise which have positive fuel trims I need to work out.

I did some more reading and might have found the source of the problem for this particular case. My new TB didn't have a physical throttle stop and the blade was over rotating past 100% throttle so on my WOT hits I might have let it fluctuate. That has been corrected now so I might just need to take another stab at it.

jimmyblue

iTrader: (11)

Trans line pressure %, during steady and shift operation,
is driven from calculated "Delivered Torque - Trans" (and
this in turn, figured from cylinder air mass in a roundabout
way we don't get to see). Then that line% and trans fluid
temp are passed to the Force Motor Current Positive table
to give you the PCS duty cycle / current that controls
line pressure and shift speed.

I have my force motor table modified so it's all in (negligible
PCS current) by 300 lb-ft and slightly more line at low cruise
than stock (not to mention getting rid of that stupid blow-off
value in the rightmost column). You can limit how stupid it
is allowed to get, by massaging all of this.

Anyway, head of the snake is air mass fidelity, against the
actual torque being made and multiplied (which latter, we
got nuthin' as far as telling the PCM what the scale-up
from motor output to trans input torque, @ RPM, slipRPM
and load is - but we all change it).

thunderstruck507

iTrader: (18)

Current tune is attached

ddnspider

iTrader: (26)

That is exactly the pid I was referring to, I just didn't have time to look up the real name of it lol. Is the force motor table what you would tweak if your trans pressure shows zero at cruise? I've noticed harsher shifts at almost zero throttle and it looks like its because min airflow would correlate to zero psi in the stock trans pressure tables. I haven't really seen much explanation of the force motor table.

ddnspider

iTrader: (26)

Any reason why your trans pressure tables are all over the place and not linear?

thunderstruck507

iTrader: (18)

No, I will look at them. I do not recall having messed with them since I started using this base tune when my current heads/cam went on the car. I have primarily been messing with MAF, VE, PE, timing, a bunch of idle stuff, and injector tables.

I ran this tune all last year but at some point did a MAF calibration correction not knowing the MAF was dirty, so when I cleaned it recently it messed up my fueling and I have been trying to correct that and thought it wouldn't hurt to smooth out the VE table a little from where it was while I was at it.

I will look at it on lunch. Does anyone have a recommendation on pressures for the table? The trans is built like most "level 2"s:

trans go hd2 kit
beast sunshell
upgraded clutches (altos everywhere but 3-4 had BW HE)
wide carbon band
sonnax HD 2-3 shift valve (keeps overrun clutches applied when in manual 1, 2, or 3)

ddnspider

iTrader: (26)

It was always recommended to me to just set them linearly from zero based on engine torque, but I don't like going all the way to the max pressure so I level off at 80psi or somewhere in there.

thunderstruck507

iTrader: (18)

Do you have all shifts set this way? Mine are considerably lower on the 2-3 which if anything I would expect should be higher.

I have the tables from an SSR which has standard and performance pressures, the performance tables look really good so I might try those and work from there.

thunderstruck507

iTrader: (18)

Ok this is what I've got to try. Does anything seem excessive or out of whack?

I copied the performance shift pressures from the SSR tune then adjusted them to be more in line with the advice from Jimmy and then smoothed them around the 280-295 ft/lbs area to make them more linear rather than stepped.

ddnspider

iTrader: (26)

That looks more like it to me at least.

Ed Wright

iTrader: (1)

If you don't know what else to do when altering the MAf table, you just need to leave it alone.

thunderstruck507

iTrader: (18)

The car has been tuned using the calc.vet method through EFI live to correct the VE and MAF for fueling and it has worked well in the past. When the car was dynoed previously the dyno wideband was within .1 of my corrected/commanded fueling and the graph for it was perfect so it seems to have worked well. Some point after that I changed some things and during retuning for them did not realize the MAF was severly dirty and skewed the results.

Just seems this particular time there was a problem with the logged information used to build the correction tables.

I don't understand how I could just use the stock MAF table seeing as how the car has an 85mm MAF with a non stock airflow straightener. In the majority of the tuning methods it seems scaling the MAF table is required. Seems to make more sense to me than just inputing altered commanded PE targets or altering fuel injector flow rates. I don't recall having seen other ways to obtain correct WOT fueling.

The point of this post was just to try to better understand the relationship between other aspects of the tune to the transmission's shift pressures. I am just trying to learn.

ddnspider

iTrader: (26)

He already said in post 12 he knew he had to touch up the MAF table and obviously knows how since he's already tuned the car. We were talking about trans pressure tables and how correct airflow relates to the eng_torque pid that is used to determine trans pressure.

joecar

The shift pressure tables you see come into play during shifts, not during running...

but otherwise the PCM calculates running pressure from its calculation of engine torque which it calculates from cylinder airmass...

so if MAF and/or VE are reporting low, then, indirectly, line pressure is going to be low.