Ragtop 99

iTrader: (7)

I just read my PCM and I was surprised at how low my shift points were set in MPH; despite having requested 6400 shift points. I've always thought the 1-2 shift was low and now I'm resetting them.

In order to get the right shift points (in my case I want 6800 rpm), I need to start with the calculated MPH at 6800 rpm and back off that for:

* converter slip
* transmission lag time

I was planning to use 5% for converter slip.
1) What factor are you using for lag time?
2) Do you vary it by gear?

F8L Z71

Damn, I just went lazy style and just added 10mph or so till I got it close to where I wanted.

I can't check my 1st gear shift because I always spin em so bad so I just cruise in 1st till I touch 6400 rpm then look at my MPH and plot it something close to that on LS1 Edit.

2nd gear is much easier cuz you can stab it from a roll and watch till you hit the desired RPM and check your MPH.

May not be the best way to do it but it gets you close then you can fiddle with it here and there + or - a couple MPH.

<small>[ March 29, 2002, 10:13 AM: Message edited by: F8LPONY ]</small>

Ragtop 99

iTrader: (7)

So far my theory bites the dust. <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" />

I am running negative lag time. That is I program the 2-3 shift for 75 mph and I was shifting at 72 mph. I guess the Yank Tranny is clicking off shifts nice and fast. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Been almost impossible to test first gear on the street; just too much power. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Reboot

iTrader: (5)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Ragtop 99:
<strong>So far my theory bites the dust. <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" />

I am running negative lag time. That is I program the 2-3 shift for 75 mph and I was shifting at 72 mph. I guess the Yank Tranny is clicking off shifts nice and fast. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I have the same issue trying to figure out my 1-2 shift points with my FLP Tranny. To take it one step further I put my pcm in a buddies 2001 with the same gearing and stock tranny. His makes the 1-2 shift 800rpm's higher with the my pcm.

I think there is alot of lag in shifting with the stock trannies.

Pro Stock John

iTrader: (34)

I'd have some sticky tires on the car to really figure out the shift points, wheelspin will cause the pcm to shortshift gears.

I've heard go for 300-400 rpms less to converter slippage.

I don't get that much slippage though.

ONYXSS

Ragtop already knows this from my previous experience, and PSJ just mentioned it above:

use your street shifts as an estimate only. My shift points on the street for the 2-3 (punching from a roll) varied significantly from a WOT pass at the track. My street Atap runs showed perfect shift points, yet I banged the limiter at the track....

Ragtop 99

iTrader: (7)

Could be, we'll see. I keep nittos on the car, so the 2-3 I'm not as worried about. I did my testing with ASR on and wasn't getting enough in 2nd gear to trigger it on the downshift.