: 1994 LT1 Cadillac V4P Shift Patterns Defined!



N0DIH
03-19-06, 11:51 PM
Ok guys, I finally have my cable and letting the cat out of the bag.

http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=34&t=002338#000006

I have started to define some of the V4P PCM tuning. Starting with the trans shifting.

LOTS more to come as I get time to define it all.

I can supply my stock .bin file for anyone with a 3.42 geared car if you want. PM me with an email that I can send it to you.

N0DIH
03-23-06, 11:52 PM
Just for giggles and grins, to see how the car handled the non V4P shift patterns, I copied in all the Corvette shift points, TCC engage/release and pressures (shift points and TCC lockups are close to stock Fleetwood/Caprice/Roadmaster) to see how much difference there is to my stock V4P programming.

The change was dramatic. Interesting enough, it felt like I added 1000#'s to the car. Much slower off the line than stock, much harder to spin the tires off the line, and generally just not as lively. If driven mild, it is ok, but the car really felt much softer. Yes, I can see this car being much slower down the 1/4mile with these shift patterns. Mid to high 15's would be expected. With V4P, I would expect much closer to 15 flat. Very dramatic results in how the cars low end performance is improved.

I was hoping to go a week or so and see mileage, but I couldn't take it that heavy feeling, so I set it back to V4P settings.

The car really 2 totally different cars with the programming as V4P vs non. Even the tune I have that was "from a professional" maintained most of the stock shift points or close to them with increased line pressures. I feel the engineers who did the V4P program really spent a lot of time with the car tuning it, where the non V4P feels much more generic. Although, likely much better for mileage, as OD comes in much lower rpm.

Note that the V4P shift points are geared around a 235 70 15 tire. So an B/D body with shorter tires (like the Impala SS wheels) may not be so happy with them. But if you have a 3.42 geared car with the stock size tires, I would highly recommend it.

The most significant difference I see is shifts are 1-2, 2-3, 3-lockup, 3-4 (TCC unlock) and then 4th lockup. Where the stock non V4P program has more variation in the shift pattern, similar to 1-2, 2-3, 3-4, 4-TCC being the more common shift scenaro. I guess when trailering, it is more important to tow in 3rd than 4th, and the potential to have the trans go into 4th and unlocked converter is much higher, which could result in early trans overheat and potential failure in comparisson to the V4P program.

caddycruiser
03-24-06, 12:31 AM
Hmm...interesting.

The non-V4P cars definately aren't what I would call snappy or lively, just like they're tuned to be decently quick, but to be as smooth and "feel-less" as possible.

What I've always wondered about was the noticeabley lower MPG ratings for a V4P car, but I guess that makes more sense now.

N0DIH
03-24-06, 12:37 AM
You sure can come out of the hole fast in a V4P car, I can say that for sure. With the Corvette shift points/TCC/pressures, it was not all that enjoyable to drive off the line.

I can smoke the rear tire anytime I want (with TCS off) with not a lot of effort. Where with the Corvette tune it was difficult at best. You had to really work at it, where with the V4P trim you can just nail it the gas and smoke em!

davesdeville
03-24-06, 05:46 AM
What does shift points, line pressures, and convertor lockup points have to do with burning the tire(s) in the first place?

Katshot
03-24-06, 08:10 AM
Ok guys, I finally have my cable and letting the cat out of the bag.

http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=34&t=002338#000006

I have started to define some of the V4P PCM tuning. Starting with the trans shifting.

LOTS more to come as I get time to define it all.

I can supply my stock .bin file for anyone with a 3.42 geared car if you want. PM me with an email that I can send it to you.

I'm not sure where Bill got the shift table he posted but it doesn't look "stock" to me. Yours looks fine for a 3.42 car. My "stock" flash (w/2.93 gears) look similar but since we have different gearing, it's hard to compare. For instance, your WOT shifts go:
1-2 = 38mph
2-3 = 67mph
3-4 = 255mph

Whereas mine were:
1-2 = 49mph
2-3 = 90mph
3-4 = 255mph

Mine (after installing 3.73 gears) are:
1-2 = 36mph
2-3 = 66mph
3-4 = 116mph

Notice, mine are virtually the same as yours but I have significantly shorter gears. So I must assume that you have plenty of room to play with. My current issue is getting the 3-4 shift before the rev limiter kicks in. I'm still whacking it about 116-117mph so unless I back off slightly, I can't get the 3-4 shift. I haven't had time to play around more with it but hopefully, I'll get back to it soon. It's been that way for damn near a year so I guess that shows how often I drive that fast.

caddycruiser
03-24-06, 08:34 AM
Katshot...hmm...is the 255mph a typo?

I sure hope so...:)

N0DIH
03-24-06, 09:41 AM
Look at the stock V4P shift points, it has some oddities like that too. Keeps you slower, at WOT, you'll never get to 4th gear (remember the old 700 R4 "problem" that would not allow WOT in 4th gear?), this is the electronic version.

I have revised mine now that it will force 3-4 around 116 mph, TCC is around there too.

Mine is current shift pattern is attached.

I am using the V4P as a pattern, and adding in some patterns of the 9C1 and my own tastes to get it to match. Keeping V4P pressures as a general rule. Some of the "pro tuned" pressures and Corvette made the 1-2 shift almost harsh.

Dave on shifts points affecting off the line, none. On pressures, I suspect the converter stall is affected, but hard to say, it didn't feel like it, but it felt sluggish in comparisson to the stock V4P setup. The stock non V4P has much lower pressures from 0-25% than the V4P has. Not sure all what that could affect in the trans to make it feel that way.

Katshot
03-24-06, 01:18 PM
You have your 3-4 shift at 116? Maybe I'm trying to set mine too high. Hell, if you're shifting at that speed with 3.42 gears.....:hmm:

N0DIH
03-24-06, 03:23 PM
I did that because when I did a run to 113 the other day I felt the engine's powerband would do better in OD at that time, I may be wrong too, as that is only around 4700-4800 rpm (assuming locked TCC, which isn't yet).

Being I rarely ever go that fast, it is probably moot point to set, but I felt that would be more advantages to use the LT1's torque there to make the car push harder.

Katshot
03-25-06, 06:50 AM
I did that because when I did a run to 113 the other day I felt the engine's powerband would do better in OD at that time, I may be wrong too, as that is only around 4700-4800 rpm (assuming locked TCC, which isn't yet).

Being I rarely ever go that fast, it is probably moot point to set, but I felt that would be more advantages to use the LT1's torque there to make the car push harder.

I'm going to take another look at that. You got me thinking.

N0DIH
03-26-06, 02:36 AM
Cars with deeper breathing like headers, head work or cams might be able to handle higher rpm shifting, but I just felt mine might make better use of the torque in a higher gear.

Let me know how it goes!


I'm going to take another look at that. You got me thinking.

N0DIH
07-17-06, 02:33 AM
Just a followup, found another change to the V4P as compared to the stock B/D calibration.*

"TCC DISABLE WITH UPSHIFT" is DISABLED on the V4P, Corvette, Z28 and Trans AM, but ENABLED on the stock B/D, including the 9C1 and Roadmaster with the V92 tow package. I don't have a B4U calibration (LT1 Caprice with V92 I think), but I'll check.

If someone has it, please let me know.

* Latest "BT" $EE Definition File for TunerCat