Gearshift Maps

[cdvs]

Hi Phil, You are probably right, but I have very good results with just changing the Drive Ratio value. Before your work, we were all pleased without even this change. You're not suggesting that not changing these values would cause the problem Timpani is having, are you?
Charl

Originally Posted by 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.

[longassname]

Hey guys,

Tapani has a seperate issue he hasn't diagnosed yet which I think makes the downshifting at high speed come to front of his mind. His rev limiter isn't working. It looks like the calculated rpms in his tcu are way low so he would have to be over 8k before his rev limiter kicked in.

With that at the front of his mind he started looking at the downshift maps and noticed that in the UK 3 to 2 map there is a threshold preventing downshifts above 60mph or so and that on the US model there is no threshold on the gear 3 downshift.




So when the gear ratio constant is changed to match a 4.44 gear ratio and the shift maps are not modified if you are at high speed and floor it it downshifts and you're either at overrev or so close to it that it certainly wasn't fruitful to have downshifted.

I've agreed with him that I think thresholds in the downshift maps are a good idea for 4.44 cars.

[longassname]

Originally Posted by cdvs

Hi Phil, You are probably right, but I have very good results with just changing the Drive Ratio value. Before your work, we were all pleased without even this change. You're not suggesting that not changing these values would cause the problem Timpani is having, are you?
Charl

Tapani also suggested scaling the maps like Phil is suggesting. This would certainly keep the engine at lower RPMs though there might still be a quirk if a threshold wasn't added to the 3 to 2 downshift map; however, from what I've heard from 4.44 owners this might not be what they want. They like being in gear longer between shifts. My personal guess is that 4.44 owners are going to prefer maps that haven't been scaled but don't downshift at high speed. I told Tapani I would like to get a consensus on the speeds to put the thresholds on the downshift maps and I will make both maps that only have the thresholds added and maps that are scaled so that they might be compared. He seems to be discussing this with Sean; I think Sean's car has a stock engine and might be a good test bed if he is interested.

[Tapani]

Good points, everyone

Since my car is a low pressure turbo, there's quite a bit of midrange thrust and that's why I might not be representative of the 4.444 crowd .

Any way, with the current set up I feel I am always one gear too low.

And on the TCU erev signal, I had the chance to monitor another SVX - all values are identical to mine. There might be something wrong in the formula in the definition file. Also the TPS signal was similar to mine.

Tapani

[Tapani]

Good morning,

Just a note on down shifting more than one gear at a time.... I looked at the operation of the hydraulic control system and, if I understand correctly, there are a few functions in it to improve the direct down shift from 4th to 2nd speed.

There is a table C on pages 28 and 29 on my AT manual, check out the 4-2 relay valve (prevents 4-3-2), 4-2 sequence valve (holds brake band applied) and the servo charger valve (sufficient oil flow to band servo while shifting 4-2).

I'm not saying that the TCU can calculate a direct shift 4-2, it might well be a fast 4-3-2, but at least my car does the shift and the hydraulics seem to be designed for it.

Also, w/o the 100% threshold on the gear 3 down map it will over rev in 2nd, then shift back up to 3rd - of course if vehicle speed is high enough.

Br,

Tapani

[Sean486]

Originally Posted by longassname

Tapani also suggested scaling the maps like Phil is suggesting. This would certainly keep the engine at lower RPMs though there might still be a quirk if a threshold wasn't added to the 3 to 2 downshift map; however, from what I've heard from 4.44 owners this might not be what they want. They like being in gear longer between shifts. My personal guess is that 4.44 owners are going to prefer maps that haven't been scaled but don't downshift at high speed. I told Tapani I would like to get a consensus on the speeds to put the thresholds on the downshift maps and I will make both maps that only have the thresholds added and maps that are scaled so that they might be compared. He seems to be discussing this with Sean; I think Sean's car has a stock engine and might be a good test bed if he is interested.

Yes I do have a stock engine, and I'd be happy to test one out.

[longassname]

Great, you have a 4.44 TCU right? While you have TCU firmware with the correct constant but without thresholds would be a great time to test where they should be. If you could repeat the exercise you did in the video Tapani sent at lower speeds you aught to be able to figure out what the highest speed is for a useful downshift for each gear. If you could do that and report back the speed, the rpm before the downshift and after the downshift that will get us started.

Originally Posted by Sean486

Yes I do have a stock engine, and I'd be happy to test one out.

[longassname]

Also, I guess we aught to move this discussion over to ECUtune TCU thread. Although we are discussing gearshift maps I get the feeling there are some who don't see my participation in the thread as a contribution no matter what I do. Let's have our discussions in the ECUtune thread.

[Tapani]

Dear all,

How is the vehicle speed for shift maps defined in the TCU? Is it VSS2, VSS1 or average?

4.444 gears, stock TCU - there's obviously a difference in the speed signals. Rear 85, front 70 @ an indicated 74 mph. If I insert the FWD fuse the shift points change quite a bit - this leads me to believe that the rear speed is ignored with fuse in place.

Is "slip" for solenoid C control defined by difference between VSS1 and VSS2 or is ABS signals used?

The solenoid C pulse width acts logically even though there's the above mentioned difference between the two speed signals.

Just trying to understand how all this works :-)

Tapani

[longassname]

speeking of cars with 4.44 gears I recently made a chip for an Australian car with 4.44 gears. I use the UK firmware for all of Europe and Australia. He hasn't gotten and installed it yet so I don't have any feedback but for public record here are the changes I made beyond my regular changes for the UK firmware:

705622 BASE CODE

************************************************** **************************************
4.44 CHANGES

C01A=D4 : changed vss1 constant for gear ratio (3.700=FE 3.900=F2 4.111=E4 4.444=D4)


***************Downshift Changes***********************************
STICK D Gear 3 Normal Downshift D220-D22E
0F0080
2814C0
4619F0
5200F0 <-(downshift threshold REDUCED FROM 65 to 52 = 4800 rpms)
FF00FF

STICK D Gear 4 Normal Downshift D232-D240
230080
500EC8
7810F0
9B00F0 <-(downshift threshold REDUCED FROM 98 to 7E = 4800 rpms)
FF00FF

STICK D Gear 3 ECONOMY Downshift D322-D32D
0F0080
3716F0
5A00F0 <-(downshift threshold REDUCED FROM 5A to 52 = 4800 rpms)
FF00FF

STICK D Gear 4 ECONOMY Downshift D331-D33C
230080
5F0EF0
9600F0 <-(downshift threshold REDUCED FROM 96 to 7E = 4800 rpms)
FF00FF

STICK D Gear 3 POWER Downshift D418-D429
160080
2818B0
5200F0 <-(downshift threshold REDUCED FROM 5A0CD8 to 5200F0 = 4800 rpms)
5200F0 <-(downshift threshold REDUCED FROM 6522 to 5200 = 4800 rpms)
5200F0 <-(downshift threshold REDUCED FROM 6F to 52 = 4800 rpms)
FF00FF

STICK D Gear 4 POWER Downshift D42D-D43E
280080
500BB0
7E00F0 <-(downshift threshold REDUCED FROM 820AD0 to 7E00F0 = 4800 rpms)
7E00F0 <-(downshift threshold REDUCED FROM 9B14 to 7E00 = 4800 rpms)
AC00F0 <-(downshift threshold REDUCED FROM AC to 7E = 4800 rpms)
FF00FF

************************************************** *****************
************************************************** **************************************

[SVXRide]

Michael,

Is the thinking here to keep the engine more in its peak torque band?

Thanks.

Bill

[longassname]

Hey Bill,

Can you rephrase the question? I don't understand what you are asking.

Originally Posted by SVXRide

Michael,

Is the thinking here to keep the engine more in its peak torque band?

Thanks.

Bill