FRISKY

Does the PCM ('02 Z06) use logical algorithms to deduce what gear the transmission is in?

There are some charts that show the rev-limits on engine RPMs for each gear. Fifth gear on my car shows a 9000-rpm limit. How does it know what gear it is in without a sensor in the transmission or shifter?

Corvette00Car

And once we know that would it be too difficult to tap into that and have a display indicating what gear we're in like a motorcycle. Simple colored lights would do fine also. Yes flame me but how many times have we been in 4th listening to the radio and thought we were in 6th. I'm ready be kind.

Dope

Hmm strange. I'm pretty sure when I used LS1edit, it only showed rev limit in gear and out of gear. When I used ls1edit on my auto car, it did have individual gear rev limiters.

Regardless, if you can't tell you're in 4th, your exhaust is too quiet ;)

Dope

angryfly

Good question. I am a bike mechanic and they have gearposition sensors that tell the ECU what gear the bike is in. I had no idea the car could tell this also. ttt

BlackZ06

The PCM has no clue what gear your 6 speed manual tranny is in. My Autotap shows the selected gear as "3" .... always.

The rev limiter is therefore set at 6500 rpm (LS6) and 6000 (LS1) regardless of what actual gear you are in.

Steve

thefly

then why would GM have custom rev limiter on/off points for each gear, it is only because it does know somehow. i believe autotap isn't looking at the correct gear and that the table for the auto is used for something else.

Bink

Here's the reply to FRISKY'S post, on LS1Tech, by Paul Blackmore - the owner of EFILIVE :


The PCM "knows" the transmission input speed (i.e. RPM) and the transmission output speed (i.e. VSS vehicle speed sensor).
It uses both of these to determine the current gearbox ratio.
There is a PID that you can log called {GM.BOXRATIO} (in EFILive - I don't know what it is called in other scan tools). It works with a 6 speed manual and shows the gear ratio that is currently selected.

Regards
Paul

2k1vert

Thanks for the info Paul. I'll add that PID to my list. Sometimes when I log for a couple of hours under all sorts of conditions and reviewing later that night, I sometimes wonder what gear I was in. It is usually fairly easy to tell, but at a glance would be sweet. :cool:


:cheers:


[Modified by 2k1vert, 7:53 PM 1/19/2004]

gojo

You can also select Transmission Input Speed and Transmission Output Speed PIDS. Since you know the tranny gear ratios you can see slippage. If you save to an Excel file you can see how long slippage lasts at each shift. It was really useful when I installed a higher stall converter and thought the slippage was the converter. It turned out the trans was slipping and this confirmed it.