now logging actual line pressure in A6, less than 100psi in 3rd

[parish8]

i got a pressure sensor hooked up to the test port on the tranny and am now able to log the line pressure. it does some wierd things but the bigest issue for me right now is low line pressure in 3rd gear.

on the dyno at about 600ft/lbs the tranny started slipping and so did the lock up clutch in the converter. car was locked in 3rd gear, circle D tripple disk and manualy locked tcc using hptuners non beta scan tool.

logging pcs1 appears to the the line pressure solenoid. the reported pressure and the actual pressure do not match but they do follow each other exactly. the actual line pressure is somewhere around 3 times higher than the pcs reported pressure.

at times i see 300+psi. mostly at very light load in 1st or 2nd. looking at the logs it seems like it only hits that very high pressure right after i start moving the first time after starting the car. it seems to settle down after a minute or so.

after making significant changes to several of the pressure numbers i didn't see any changes in the actual line pressure.

going from stock numbers to numbers that are 40% higher made no noticable changes to the actual line pressure on these tables. max pressure, max pressure B, max clutch. on the "max line pressure" table i took many of the numbers up a little and set the 4000rpm and 7000rpm colums at 200psi wich is a very large increase from what was in there.

i also bumped up the "oncoming pressure preset 3-4" table thinking it might be lowering the pressure getting ready for a shift?

all of my base upshift tables have been messed with a little. the injectors are a little big so the airflow tables are not exact so the tq numbers are a little low at times. we worked the tq axis so 330ft/lbs is enough to get into the highest cell where it was 440 or so before. i never see less than 330ft/lbs calculated tq. most of the pressure numbers on the higher end of those tables have been bumped up some and i never tried putting them back to stock. keep in mind most of my testing so far is just thru 3rd gear, not looking at the shifts yet.

i lowered my power as much as i could about 4psi and super rich. this allowed me to get into in 2nd gear a little. 2nd looked ok but i didn't get up into the high rpms. 150+psi for 2nd up to at least 5500rpm.

then it shifts into 3rd. pressure goes up nicely to around 200psi. the pressure goes up as soon as the tranny comands the shift but the shift happens later. by 5000rpm it starts going down and by 6000rpm it is down close to 100psi.

the pressure follows exaclty with the pcs1 comanded pressure so it appears to be a tuning thing.

without even thinking about getting thru a shift with this tranny i 1st need to be able to hold the power mid gear. what am i missing? how do i get/keep the pressures up from 5000rpm up in 3rd.

once it hits 4th pressure goes above 200psi, cant say for how long since i cant hold 4th for long without risk of going to jail. i will get some screen shots up shortly and post up my last tune.





here is my latest tune >> http://www.neufamily.org/images/lock...ges%20log4.hpt

[Bluecat]

I'd say your right about the fact that it's in the tune. It could be possible that the PCS 1 pid you logged was an observed reading as apposed to a command value and thats why it follows your external reading. (I don't know if they have an internal sensor or not). But I'd say it is infact the commaned value since it's so perfecty strait at times and is a few frames ahead of your sensor. That the case its for sure in the tune somewhere.

Good to know the actual psi numbers are higher than the dismal numbers computer is telling us. Guess the conversion from binary to engineering numbers still needs a little work.

I hate that you tried all those changes with little or no effect on the actual happenings. I'm as stumped as you are on why the command line pressure is dropping while the calculated torque numbers are staying up. There must be some undiscovered table scaling the pressure down as rpm goes up under certain conditions or time value. I've never logged any of the pressure stuff because I haven't had any trouble yet. Been making changes to many of the tables you mentioned thinking I could tell they were helping. Guess not...

Wish I could offer some help, but like I said, so far I've not had any trouble from an A6 holding. I've not had an A6 car to tune thats made more than 550 either. When most people were having trouble getting them to shift on time, I wasn't. So I felt like I had a pretty good grasp on these things, but now I feel like I just haven't fooled with one thats mean enough yet.

Keep us posted on what you figure out.

[parish8]

^diddo

you can log;

pcs volts - lower volts = more line pressure , high volts = low line pressure

to much and it will burn clutches as it will not allow full disengaugement of the clutch packs and they will slip and burn when shifting.

i didn't see that pid. you sure that is an option on the e38 pcm? i will look again.

[parish8]

talking to my super geek buddy john it looks like we have a pretty easy and bad ass set up if we want to control that pcs1 noid.

using megasquirt 1 and the built in boost contol we should be able to not only control the dutycycle to that valve but use closed loop targeting based on tps and rpm or map and rpm. i can't predict any side effects of doing this. stock tranny contoler might get upset, those pressures might be that low for a reason? who knows but what i do know is i cant turn it up any higher till this is figured out.

going to give it a week or two and see if anyone has any programing sugestions for me to try.

[transam_151]

is this a stock transmission?