drcook

I created an alternate save file under a name I would never mistake to update my car with. Then I went through and did the recalculation. After that I went back and did a compare of the original file to the recalculated file and YES it is changing the values in certain tables but NOT ALL tables that reference mph.

The next step is to have forum member Barchetta to send me the original saved file from his 1996. He has the 2.59 rear gears while I have the 3.07 rear gears. Then I will compare the 2 of those files and look at what the difference is.

If the differences are the same as what the Jet box is, then I understand what you are saying. If they show (2.59 -vs- 3.07) the same tables having differences, then the programmers did a cheat due to the primitiveness of the computer in the LT1's and substituted MPH for RPM in certain tables so that they would not have to perform a calculation.

Just for the record, this is what created the whole Y2K debacle and while everyone says it was a non-event, it was a non-event because there were 1000's of programmers across the country making sure it was a non-event. I was running a crew of contractors for the bank making sure the system I had responsibility for didn't crash.

But back to the subject. Once I look at the 2.59 -vs- 3.07 tables then the next step that would be in order, but we really don't know at this point is what RPM was the car at with the old gears at a certain speed -vs- what RPM was the car doing at a the same mph after it was correctly compensated for through the ABBOTT box. From this information we can the calculate what RPM the motor was at in the original file for the car and hit the tables and where it would hit the tables using the recalced MPH from the RPM after being adjusted.

That would really tell us if the ABBOTT was causing incorrect values to be attained due to where it hits in the table or does it actually work out because the fudge is at the VSS -vs- the fudge being in the tables using MPH instead of RPM. That is what they are doing in the TCC tables from what I saw in the compare file after I did the adjustment through the Jet box.

MatthewMiller

Ah hah! You are correct. When I trialed that change I only hit the "Calculate" button. It doesn't ask you if you want it to make all those other changes until you hit "Apply." I just went back and tried that, and it sure did ask to make a bunch of changes in the transmission table, just like you said. So you are right. Well...in my defense, I told you I might be missing something! Always good to hedge one's bets.

So yeah, if DST wants to go through and change any of the transmission tables based on the new gear/speedo setup, then we can be sure that those tables will not get changed just by adding the Abbott box upstream of the PCM. Now I'm totally on the other side of the discussion: I don't see how the car can possibly run correctly with the Abbott box in place. OTOH, if the car had a manual trans it probably would run just fine with just the Abbott box and no recalibration.

ETA: Now it makes sense why this speedo calibration function is listed under the "Tools" menu of DST rather than as a "Constant" table. It really is a tool to make life much easier for the tuner. That's a pretty neat function for anyone with an automatic transmission to have.

bjankuski

Thanks, and thanks for the intesting discussion.

drcook

Let's wait until I get a copy of a 2.59 calibration file to compare to my 3.07 calibration file (from the factory) and then we can see if the same tables are changed -vs- what the Jet software is changing.

Notice above I also agreed it is changing tables, but I also said it is not changing all the tables that have MPH referenced in them.

I am waiting for Barchetta to respond to my text and email asking for a copy of his file so I can load it up and use the Jet software built in compare function to look for differences.

Unless someone else here on the forum has a '96, a Jet box, a 2.59 rear ratio and a saved file of the original settings before modifications were made.

Here is where the changes going from a 3.07 to a 3.54 calibration were made:

Constants
Transmission Parameters
Low PRNDL Upshift Speed Threshold
Low PRNDL Downshift Speed Threshold
System Parameters
Speedometer Scalar
Speedometer Scalar, Fraction
Speedometer Scalar, (Scan Tool)
Time Between Pulses For 'Stop'

Tables
Transmission Tables
Normal Mode Up/Down Shift Points
Performance Up/Down Shift Points
Manual Mode Up/Down Shift Points
Cruise Mode Up/Down Shift Points
Hot Mode Up/Down Shift Points
Kickdown Mode Up/Down Shift Points
Hot Kickdown Mode Up/Down Shift Points
Cold Kickdown Mode Up/Down Shift Points
TCC Normal Mode Release MPH Vs. Gear Vs. %TPS
TCC Normal Mode Engage MPH Vs. Gear Vs. %TPS
TCC Manual Mode Release MPH Vs. Gear Vs. %TPS
TCC Manual Mode Engage MPH Vs. Gear Vs. %TPS
TCC Hot Mode Release MPH Vs. Gear Vs. %TPS
TCC Hot Mode Engage MPH Vs. Gear Vs. %TPS
TCC Performance Mode Release MPH Vs. Gear Vs. %TPS
TCC Performance Mode Engage MPH Vs. Gear Vs. %TPS
TCC Cruise Mode Release MPH Vs. Gear Vs. %TPS
TCC Cruise Mode Engage MPH Vs. Gear Vs. %TPS
TCC P.E. Mode Forced Lock Speed Threshold Vs. Gear

drcook

Here are the differences between a 1996 2.59 A4 car and a 1996 3.07 A4 car

Total Parameters Compared: 652
Total Differences Found: 41

Switches
Calibration Options
Performance Mode Light Option
Trans. Hot Mode Option

Constants
Transmission Parameters
Low PRNDL Downshift Speed Threshold
System Parameters
Speedometer Scalar
Speedometer Scalar, Fraction
Speedometer Scalar, (Scan Tool)
Time Between Pulses For 'Stop'

Tables
Fuel Tables
Open Loop AFR Vs Coolant Temp. Vs. MAP
Initial Startup AFR Enrichment Vs. Coolant Temp.
Transmission Tables
Normal Mode Up/Down Shift Points
Performance Up/Down Shift Points
Manual Mode Up/Down Shift Points
Cruise Mode Up/Down Shift Points
Hot Mode Up/Down Shift Points
Kickdown Mode Up/Down Shift Points
Hot Kickdown Mode Up/Down Shift Points
Force Motor Pressure Offset Vs. %TPS Vs. Gear (Normal Mode)
Force Motor Pressure Offset Vs. %TPS Vs. Gear (Perf. Mode)
Force Motor Pressure Offset Vs. %TPS Va. Gear (Manual Mode)
Line Pressure Offset (psi) Vs. TPS Vs. Gear
Line Pressure Mod (psi) Vs. %TPS Vs. Trans. Temp, 2nd Gear
Line Pressure Mod (psi) Vs. %TPS Vs. Trans. Temp, 3rd Gear
Down Shift Pressure Modifier 4 -> 3 Vs MPH
Shift Time (sec) Vs. %TPS Vs. Shift, Normal Mode, Low Alt.
Shift Time (sec) Vs. %TPS Vs. Shift, Normal Mode, High Alt.
Shift Time (sec) Vs. %TPS Vs. Shift, Performance, Low Alt.
Shift Time (sec) Vs. %TPS Vs. Shift, Performance, High Alt.
TCC Normal Mode Release MPH Vs. Gear Vs. %TPS
TCC Normal Mode Engage MPH Vs. Gear Vs. %TPS
TCC Manual Mode Release MPH Vs. Gear Vs. %TPS
TCC Manual Mode Engage MPH Vs. Gear Vs. %TPS
TCC Hot Mode Release MPH Vs. Gear Vs. %TPS
TCC Hot Mode Engage MPH Vs. Gear Vs. %TPS
TCC Performance Mode Release MPH Vs. Gear Vs. %TPS
TCC Performance Mode Engage MPH Vs. Gear Vs. %TPS
TCC Cruise Mode Release MPH Vs. Gear Vs. %TPS
TCC Cruise Mode Engage MPH Vs. Gear Vs. %TPS
TCC P.E. Mode Forced Lock Speed Threshold Vs. Gear
TCC Apply Operating Point (%DC) Vs. %TPS Vs. Gear
TCC Apply Rate (%DC/Sec) Vs. Gear Vs. %TPS
TCC Release Rate (%DC/Sec) Vs. Gear Vs. %TPS

drcook

You are correct as far as tables and values being different. I can see that I was arguing about how it would have been had the programming been dynamic . That was my error. So I have to apologize.

I now realize you were talking about how it was programmed not how it should have been programmed. AND that it applies to automatics, as MM said above, it would probably/should/most likely be just fine with the LT4 (stick cars) as they don't have the same issues (read that an electronic auto trans) to deal with.

The reason I say this is that I can see (as I said above) that they (ins some cases) substituted MPH for RPM in order to make the programming easier and fit within the constraints of the cpu architecture back then, limited CPU/processing power, limited memory, because it had to fit and function in a car. It just made the programming easier.

Now, that I have the compare between a 2.59 A4 96 and a 3.07 A4 96 we can see that there are tables that GM changed that the Jet tuner software (and its predecessor before Jet bought them, unless there were corrections after the sale that they didn't get).

We can also see (by looking at the actual tables) that the Jet software goes to specific tables and applies a percentage to all rows and columns, while GM had selective value changes in those tables. Will it hurt, no, our cars are never going to hit the designated MPH figure so that is a mute point. However, now I am going to go back through and figure out how the Jet software derived the value it did and applied to the tables.

It is too bad we don't have before and after values from the OP's or another person's car that recorded the RPM / MPH at designated points both before and after the ABBOTT box AND GEAR CHANGE so that we could navigate manually into the tables and find out where it hits to see what effect changing the value of the signal from the VSS actually does. But we would also need the values from the TPS.

Other than really figuring out now what is going on in the software and how it is changing the software, it has also forced me down the learning curve on what will need to be changed (if anything) in the tables regarding horsepower changes but keeping the same rear gear ratio.

The other curiousness that we have found (Barchetta and I) was that in the LT4 programming values, there are, yes are automatic transmission values that are different than the LT1's values. We can thank forum member Grandspt for this because he sent me his base JCL from his 96 LT4 car.

Also as I chased some of the links referred to and did some searches, I found a mention about the "performance mode" tables and references to a switch being wired in that allows access to such.

With this said, I now wonder if the B&M ShiftPlus+ is accessing the table(s) ?

drcook

Here is where I found mention of the switch

http://www.lt1pcmtuning.com/tips/#Auto

drcook

OK here goes. I ran through it and I don't think it will really make a difference (FOR MY CAR). Possibly at the dragstrip it might, but for an everyday, probably not.

The real caveat is the originating gear ratio -vs- the new gear ratio. Going from a 2.59 to a 3.54 the results/differences are going to be more than what the results are from my car going from a 3.07 to 3.54 or say a 2.59 to 3.73's.

Using the table in the picture which is a snapshot from my car, a 96 3.07 and the calculator in the link, we will get these figures. I also used the tire size calculator here:

https://tiresize.com/calculator/ I have 275/40/17 tires
http://www.advanced-ev.com/Calculators/TireSize/ even though this link say tire size, it calculates all the variables
http://www.csgnetwork.com/rgpspeedcalc.html indicated -vs- actual speed calculator

At a reading of 50% on the TPS the trans mission is going to shift from 1 > 2 at 26 MPH. To see the math, I used the calculator and derived that at 26 mph, tire size of 25.7, gear ratio 3.07 the engine is spinning at 1044/1045 (depending on if you recalculate the figures to double check, it gets small, rounding errors, too small to care about)

with 3.54 gears indicated speed of 26 is 22.5 actual, so it is going to shift early and at 903 rpm instead of the 1044, or 141 rpms less than it would have

However in the main line pressure table, it has no effect, it will accomodate the difference.

The real bugger is the RPM and where it is at on the performance curve.

when you go to 3.73's, it is going to shift at 21.4 and 859 RPM, but once again in the main line table, it has no effect on the pressure table.

in fact, every table that I looked at, there is no effect on a 50% tps 1 > 2 shift, between the 3.07's and 3.54's EXCEPT the rpm is lower than it would normally be had the computer been programmed correctly.

There possibly could be a STACKABLE effect, where table a chains to table b and an accumulative error occurs, but without actually knowing how the software truly works, I can simulate that.

I looked at the TCC tables and they are not that finely delineated. I did not do any calculation for them, but it would need to be done at t 3rd and 4th gear level if it was.

also is it realistic to expect to be at 50% TPS ? I cannot say without some data logging software

drcook

so I think we can postulate that the use of the ABBOTT box is going to result in you getting your foot deeper into the gas pedal than you should have, had the engine been reprogrammed -vs- the signal fudged.

unless I am missing something.

the last couple days I have had to try and drag myself to attempt to catch up with you folks on how this stuff works. as I said, I tend to look at how it should have been done, and erred in not looking at and understanding how it really was done.

it is a lot easier to just say this MPH than it is to populate the table in other values.

Additionally the error in MPH is worse when you go from a higher numerical ratio to a lower one. Take for instance, going from a 3.73 to a 3.07 ratio, the indicated speed is 60 while actual speed is 72.9.

The effect gets wider when you transition from minutes (RPM) to hours (MPH) that extra times 60 makes it bigger.

2LZ

Ok gang. Here's the scoop.

Keep in mind that I have no idea what's up with the tables or programming or most of what's been discussed above. I don't have the Jet unit to gather that info.
"Practically speaking", it works. I knew after I got the 3.54's installed that it seemed to roll through the gears faster, but I drive fairly mellow so it didn't stand out too much. Well, let me tell you, huge difference in shift points now. Transmission is more spirited in its actions and it finally feels like I have new gearing in regards to acceleration. Snapped the back-end loose real nicely.

I still need to get the wife out on the road in her car so I can fine tune the dip switches more closely, but so far, I'm happy with it.
If it has any possible drawback, it may seem to react a tad slowly in regards to speedo readout but it is digital, so there's sample time involved. That said, I never paid much attention to its reaction before. Now I'm watching it.
It's just nice to know that the '96 speedo (OBDII) can also be adjusted with a gadget.

I can also verify that if you ever lose your VSS, expect some really odd behaviors our of your car. I had all the leads test clipped to make sure I was hooking things up correctly, and the feed from the VSS unhooked as I was rolling down the road. Not only did the speedo suddenly read "0"....but the car now thought I was stopped. Talk about instant electronic confusion. It was dying to downshift "right now". I pulled over, got it re-clipped and all was good.

Once I stared at War and Peace (FSM) long enough, I found all the required leads are right there on top at the PCM in both the Red and Black connectors, so the install was a snap after I knew what I was chasing. No laying on your back under the car or dash. i actually sat on a short stool and did most of the work. Gotta love that clam shell hood.

WVZR-1

I'd rely I believe on a GPS based component to adjust 'dip-switches' regarding speed! 2d car and driver doesn't generally work well. Measured miles and the odometer do well for a 'verification'.

** A very accurate verification could be done if you actually used 'your tire dimensions' (not advertised diameters/RPM) along with a very accurate tachometer. Tachometer need verification also but then you've always a 'back-up' so to speak. I believe someone mentioned earlier in the thread 'another component to fail' when using a DRA of any sort.

drcook

Cool, that is what I thought once I started working into the tables. When I said you would have to get your foot into it a little deeper, that is all I meant, just a little deeper. A little more RPM deeper which isn't much (in the example I chased above 141 rpms, I got that in my truck when I switched to Transynd from dyno trans fluid, Transynd is a premium synthetic fluid). That can make it feel a little snappier I would suspect. I could not find any instance where it would have caused a glaring mismatch issue.

It is good that it worked out that way so back when I found it and you bought, then fast forward, you aren't throwing mud at me.

2LZ

LOL! No sweat drcook. I don't do mud. I come here for the excellent info and good conversation.

MatthewMiller

FWIW, even with a manual the car doesn't quite run right without a working VSS. Mine crapped out on me and the car would want to stall as I rolled to stop and disengaged the clutch, for example. I think that's called a "dashpot" function. It was still drivable, but it's clear that even just in terms of how the engine runs, the PCM does use the VSS speed data. With an automatic, it would be a lot more messed up due to the shift programming having to rely heavily on it. I suppose that at WOT it would work as well as ever, though.

Polo Vert

On my 94 I went from the 2.59 to the 3.07 and I calibrated my speedo with a Hypertech programmer I snagged cheap off Fleabay. Worked perfectly.