Figured I'd share about what I've done so far with my shift points and how I calculated them... I never found much info on this. Some of it may be obvious, but it wasn't to me.

Stock shift points were 5700 RPMs. Looking at my dyno sheet, I decided to lower my shift points to around 5000 RPMs, since thats where my HP curve levels off... will this give me a better ET shifting sooner? Who knows, but I'm having fun trying this stuff out, and I'll be able to test different things at the track.

Anyways...

Using Tunercat, and probably the same with LT1_Edit, you can't just input a desired shift RPM... it uses MPH instead. That normally wouldn't be a problem, but it looks like the computer uses these shift points as a signal, and that it actually shifts at a higher MPH and RPM. I guess alot happens in a split second. For example, the 2-3 shift is set to 73 MPH, but the tranny actually shifts around 80 MPH.

Stock settings:

1-2 = 36 MPH
2-3 = 73 MPH
3-4 = 126 MPH

So that makes it sort of difficult, or so I thought.

Figuring out a lower actual shift MPH was easy, but trying to figure out the even lower "prep" MPH the computer needs was sort of tough. Using a few different methods, and the RPM and MPH calculators, I kept getting roughly the same MPH calculations for each of the shifts.

One way was figuring out the percentage applied to the stock shift MPH and their "prep" shift points. Roughly 80%, 87%, and 92% for the 1-2, 2-3, and 3-4 respectively. I then used those percentages on my desired shift MPHs, and got these.

Method 1:

1-2 = 31
2-3 = 64
3-4 = 110

Another method I used was to just drop 700 RPMs from the stock 5700 to get 5000. I did that by dropping the same 700 RPMs from my calculated MPHs... In other words, I plugged in the stock 36, 73, and 126 shift MPHs into the RPM and MPH calculator, and found the RPMs of 4600, 4969, and 5262. Subtract 700 RPMs from those to get 3900, 4269, and 4562... plug those back in to get MPH...

Method 2:

1-2 = 31
2-3 = 63
3-4 = 109

Of course all this is for my car, with 3.23 gears and stock 245/50/16 tires. You can probably raise your shift points the same way. I did both methods to sort of double check my numbers. I also decided to set my 3-4 shift up to 117 MPH, although leaving it stock would also be fine... I don't plan on shifting into 4th at the track. You also need to have downshifts lower than upshifts, so here is my final table:

Final:

1-2 = 31
2-3 = 63
3-4 = 117
2-1 = 25
3-2 = 58
4-3 = 109

So, it worked out great, at least it appears that way. Tach hit 5K and it shifted, of course that isn't really too accurate. And, looking over my Freescan logs from today (tested in the wet, didn't get any 3-4 shifts .), shifts were pretty much in the 5000-5100 range. Earlier logs show 5600-5700. Tomorrow I'll watch my Scanmaster, I didn't do that.

 

I never thought about going that way to get a desirable shift MPH. I have my car shift at peak power, at 6100 RPM and

1-2....39
2-3....75
3-4....120

2-1....29
3-2....64
4-3....108


I have 3.42 gears and 275/40/17 tires...

AFAIK the computer has to have both values met to shift ie, if you have already met the shift MPH your tranny will shift once the shift RPM is met. Conversly if you have already met the RPM the car will rev till the MPH is met, this being why alot of people bounce off the rev limiter when the change their shift points.

Mine have worked well so far just on trial and error. I used a shift point calculator on the internet and it suggested I shift at 6500 RPM's. I would try it out but not the stock bottom end.

 

Stevil, I tried that calculator and got

1-2 49
2-3 85
3-4 212

Did I do something wrong?

 

Oh crap, don't tell me I figured all that out, when I could have used RPMs instead of MPH. Doh!

Someone posted about setting the shift RPMs to 1000 or something like that, and used MPH to shift. They said thats what HPP did. I'll have to try the reverse and see what happens.

Not sure on the calculator for yours... I got 44 MPH for the desired 1-2 shift and 83 MPH for the 2-3 shift. Then applied the 80% to the 1-2, and 87% to the 2-3 to get the "prep" shift points, which came to 36 and 72 MPH.

But of course it may be different % differences with your setup... not sure what stock settings are, or what MPH your car shifted at stock.

If your shift points work fine, I wouldn't mess with them.

 

I just think I didnt used the calculator right!!!

Also thats only true at WOT, otherwise the other tables are used, in LT1 edit its normal mode vs MPH, thats based on a certain TPS.

What you have done so far sounds good to me, no need to rev way past peak power. I just messed around with my MPH to see what worked.

Good luck

 

You will likely find your ET's lower when shifting 300-400 RPM over peak HP.

Imagine the RPM amount that will drop when you shift (like ~2200 RPM in the 1-2 shift on a 4L60E) as a window over your dyno sheet. Now slide that over the peak HP. You want the higher HP numbers on the graph to be in that window... typically 300-400 RPM past peak. Try it

 

MisterGuru,
That is something I would really like to do. But do you think reving to 6400-6500 on the stock bottom end is a good Idea?
I would love too but I just dont want to break things..

 

No, I sure don't think its a good idea. but I do it I shift at 6700. My friend Van has been shifting at 6500 for over a year with no problems related to bottom end. I have been going to 6500-6700 since June w/64,xxx miles

Your mileage may vary... I figure if I spin a bearing it's easier to convince the wife I need a 396

 

Yeah, I'll try a few different things this weekend at the track... shifting at a higher RPM, lower RPM, etc. My idea was, that since I go into 3rd gear for a short bit before the traps, lowering the shift points would make me end up going through the traps at a higher RPM in 3rd, more towards my peak power. Not sure if worrying about 3rd gear is even worth it...

 

Stevil- Setting the RPM is much easyer than that. I went round anround trying to figure this out, and than found out how easy it realy is. First the car can shift useing the rpm threshold table- but remenber that the car takes 350-400rpm to actully shift. The car gets the signal at the rpm you tell it in that table but it takes 350-400 rpm before the shift is completed. But remeber it must all so meet mph. Both mph and rpmthreshold must be meet to shift at WOT. So what you would do is set the MPH lower than it needs to be, to shift at a certain RPM example(1-2 MPH=20,RPM=5400) this would shift the car at 5750-5800 depending how hard your tranny shifts. Another example (1-2 MPH=15,RPM=5400) this would shift the car at the exact same RPM. So there is no reason to work out MPH. Just set the MPH table a little lower and use the RPM theshold table- but don't forget to set the RPM theshold table 350-400 rpm lower than you want to shift at. I hope this wasn't confussing, Tell me if you understand.

 

Kyle, I did the exact same thing you are talking about, but *** backwards with MPH instead of RPM... for some dumb reason I thought you had to use MPH, and couldn't use RPMs. I think I thought that because the RPM table only has upshifts...?

It still turned out like I wanted it to, heh.

 

I have heard 2 stories about the tranny taking up RPM to shift, 1 like dayusmc says it takes 400 or so RPM others say it shifts right on command.

I already have a shift kit and high tranny pressures so Im assuming at most Im giving up maybe 100 or so RPM, so that puts me at 6200....I need some sort of data logging program to figure this stuff out for sure....make things a hell of alot easier.

 

I also have a shift kit in my car. You still shift 300-350 RPM after the set RPM

 

Taking the agreed upon WAG of 350-400rpm for the actual shift to take place....here's what I did....

Normal mode -
1st = 39
2nd = 73
3rd = 117

So that's 5732, 5786, and 5620

I have a hot cam, 1 3/4 headers, OBDI, 3.73s and 2,400 stall.

the reason I went so short on the 1-2 is that with all the previous programming I've had done for me....when I get traction, it hits the rev limiter on the 1-2 everytime and the 2-3 occasionally. My rev limit is set to 6397 and the low 1st upshift is at 45mph (was at 52).

The old shifts were at 40, 77, 125.

I didn't see anywhere else to play with shift points as it pertains to what I'm doing.

I've not downloaded this to see how it works. I was hoping to get some data from you folks on this. Yes, I am running tunercat.

I figure if this works, then I can begin bumping the shifts up to where I can avoid the limiter. I will not turn my stock bottom-end over 6,400rpm. This is my commuter car..!!!

Is there anything different I need to do in the speed calibration that would help...? I know my previous tuner and I had some difficulty making the shifts correct when I went to a BBK 52mm TB.:dunno: