Gearshift Maps

[longassname]

No I haven't

Originally Posted by Huskymaniac

Mike,

Have you had a chance to check if the original duty cycles for solenoid A are the same for the 96 TCU as they were for the older model?

[Huskymaniac]

Originally Posted by longassname

I haven't checked. I haven't done any line pressure mods to the 96 tcu yet.

Originally Posted by longassname

No I haven't

Would you just set the duty cycle maps to the same as in the TCUs for the older models? Is there any reason to believe that they should be different given all of the design modifications the tranny went through over the years? Along similar lines, would they need to be different if the tranny had the upgraded valve bodies?

[amber]

Originally Posted by longassname

Well Ron,

If I were to guess....I would guess they used some formula to project what duty ratio would generate the minimum pressure necessary for the clutch packs to carry the expected torque loads pluss some margin. It doesn't matter to me. I know they missed the mark and the high clutch pack slips at light cruise and I can't imagine the miniscule amount of power it takes to drive the pump against a higher pressure being consequential enough to fiddle around with using anything less than the maximum pressure available.

I can confirm having seen that the gauge Trevor has fitted to his 92 SVX shows approx 60 PSI when the car is cruising at steady speed. This is the lowest pressure which is indicated at any time with maximum being around 175 which is over scale on his 0 - 160 gauge.

[1986nate]

I would like to add here that I drove a 97 for the first time today, and it seems as though the shift maps are much different. 3rd gear holds even under light-no throttle up to about 35 mph instead of shifting to 4th around 27 or 28 mph in earlier models that I have and others that I have driven. I can't recall the other gears as I was just astonished at the higher 3-4 shift point.

[longassname]

Phil,

I made a definitions file to configure my ECUtuner software for communicating with the TCU so one of my customers can do some diagnostics on his transmission (and of course am posting it for public use and hopefully expansion). It doesn't have any of the table/map locations in it yet but it does have the select monitor parameter locations and diagnostic and switch bitmaps. If you could give it a quick look to see if anything doesn't match with what you know I'd appreciate it.

http://www.ecutune.com/ecutuner/defi...efinitions.xls

[Tapani]

Hang on, just downloaded and opened....

Will go for a drive (to the salt mine) and report back in two hours .

Tapani

[Tapani]

Works like a Buick (a traditional saying from northern Finland) .

Tapani

[Tapani]

I played around with the ECUtuner and picked the brain of the TCU.

The Erev (rpm) figure seems a bit odd... at an indicated 2000rpm the ECU side says 2000 rpm and the TCU shows 1550 rpm (15500rpm with Phils original formula rpm=value*250).

I hooked up a scope to the pin 16 in the B61 ECU connector and it shows 10,2msec between ignition pulses which equals to 1960 rpm (three pulses per rev). The pulse height is 11,2V - should be good enough. Same figures at the pin 5 in the B67 connector of the TCU at the other end of the wire and all figures act logically thru the rev range.

With ignition on and engine off the TPS signal at the ECU is 0,49V with a closed throttle and 4.0V when floored. The same figures at the TCU are 9,8% and 80% with this definition file.

Battery voltage at the ECU is 12,69V while the TCU shows 11,84V when the battery terminals show 12,4V with a digital multimeter - all this with ignition on and engine off. At idle all voltages are very close - 13,4V. Strange, eh?

Everything else I have looked at seems logical.

Any comments? The ECUtuner is very nice - so nice to see how the MAF saturates at 5500rpm (and the fuel cut steps in) with a boost level of 0,3bar... no intercooling or larger MAF, injectors and stage 2 (yet).....

Kind regards from Finland,

Tapani

[Tapani]

Ok,

The reason why I looked at the TCU values is that for some reason my 4.444 geared car does not up shift at the rev limiter set in the TCU.

Another thing I noticed is that it will down shift to a gear too low at practically any speed, for example if I floor the throttle at 75mph while in 4th it will down shift to 2nd and over rev the engine (6500rpm equals to app. 65mph with 4,444 gearing in second gear).

I looked at the shift maps on Phils site and noticed that the vertical (+horizontal) 100% threshold to prevent unwanted down shift is missing on several down shift maps, i.e. the line continues horizontally at 88% all the way to the right. The ukm, usm and jpm maps seem to differ in this respect.

Sean486 made some tests on his 4.444 geared car, which does shift up at the set 6580 rpm and maybe 65mph. When he floors it at a tad over 70 mph while in fourth the transmission shifts all the way down to second (first?) and the engines goes into red before shifting up to third.

After talking to Michael we believe that these thresholds should be added in all maps and we will experiment on this.

Any input from other people with 4.444 gearing regarding what these thresholds should be would be greatly appreciated.

Tapani

[cdvs]

Are you looking at the actual hex values or Phil's graphs?

The horizontal lines you refer to are actually somewhat misleading. Phil followed the format established by Subaru in the service manual. I personally believe that a straight vertical line would more clearly represent the actual values stored.

Perhaps identifying a specific market would be helpful. One can assume you are in Drive.

[Tapani]

I'm looking at Phils lines, there's an excel sheet with all numbers on his site. And yes, I'm in drive.

In the usm drive maps the gear 3 down and the gear 2 down lines never reach 100%, but stay at 88%. The 100% threshold prevents down shifting.

Here's what happens, an unneccessary down shift to second, over rev and up shift to third:

http://s644.photobucket.com/albums/u...t=IMG_0456.mp4

I think the down and up shift lines should never cross. So the thresholds should be added and in a 4.444 geared car at lower speeds than the OEM maps. All maps are TPS vs VSS, not rpm.

Tapani

[cdvs]

Now you're referring to gear 3 and 2? If your in 4th, that's the only map it will look at. This is an Apple II era computer. One thing at a time and wait for it to get the job done. I'm going to send you a picture of my TCU program that shows the graph and values in decimal. I don't see any holes.

I don't have a car with a 4.44 here (or time to get to where I might go this fast). I'm not inclined to ask my daughter to perform this test. However, I'm sure I've punched them at such speeds and they have downshifted to 3rd without visiting 2nd. Seems to me others here with 4.44s also have heavy feet and would have noticed this problem. Don't kill the messenger!

[Tapani]

I didn't quite follow... Do you mean that the tranny will never shift two gears down? If there's nothing (a set threshold) to stop it from shifting into second (or even to first) at a too high speed then it will - if you are going too fast for second gear (over ~85 mph with 3,54 gears, ~65 mph with 4,444) it will over rev and then shift back up to third.

Is there something I'm missing ?

Other people with 4,44 ? Stock or modified TCUs?

Kind regards,

Tapani

[cdvs]

Originally Posted by Tapani

... Do you mean that the tranny will never shift two gears down?

All I can say is that the TCU will not tell it to shift up or down more than one gear at a time.

[b3lha]

Basically there are two, maybe three, things you need to do for a 4.444 swap.

Firstly there are some diff-ratio constants in the TCU which you need to adjust. The way these work is slightly different depending on whether you have JDM, Euro or USA style TCU.

Secondly you need to scale the shift and torque converter maps by the percentage difference between diff ratios. Experience shows that it is better to scale maps using software than try to manually edit them.

Thirdly, if any of your individual gears are different you need to change the gear ratio constants.

I did a 4.444 TCU for Ron (NeedForSpeed) in California, I'm sure he'll chime in and tell you how it compares to the stock TCU.