bastarddsm
20+ Year Contributor
- 5,620
- 1,458
- Aug 26, 2003
-
Mendota,
Illinois
In my never ending quest to make my car quicker and more street-able I've spent a ton of time and effort trying various combinations of parts, and other things to make them work. Lately I've been working with an ACT2900/street disc setup, as it really works nice for DD. The problem is they typically don't shift well. I've done a lot of work to figure that out and fix the problem - the stock system doesn't move the TOB far enough to full disengage the clutch. So anyway here's a look at a datalog from a 9200RPM 1-2 shift I got the other day.
This is just the raw data, but take a look at it. The green trace represents the upper clutch switch state, the purple like represents the 'nlts' limiter acting and turning the injectors off and then back on. Finally look at the Red RPM trace, notice the peak and where the slope changes. Now I'll add in cursors at the clutch switch transitions.
Clutch up, down, and back up in .357s, average stuff is in the .5-1s, and some really really good guys get it done in .25s. Now here's a neat one - I'll move the cursors to the points where the clutch actually releases, and then grabs.
.280s! That's the clutch disc going from 9200 down to 5600 in .28s. That's crazy!
What's even better about this is the trans is all old beat up junk. It's a used 1/2 slider and synchros that I bought in 2008, and have been using since! For comparison, last fall I was experimenting with a Tilton Twin Carbon, and I was getting shifts (clutch up/down/up) in the .32s range. I was also running a face-plated gear set last summer - even clutch-less shifting only using a blip of the throttle to shift it, these averaged about .30s throttle up-down-up. To give you an idea how quick a .30s shift is:
The secret to getting shifts this quick is simple, get the clutch to release. Look for a new tech thread on this soon!
You must be logged in to view this image or video.
This is just the raw data, but take a look at it. The green trace represents the upper clutch switch state, the purple like represents the 'nlts' limiter acting and turning the injectors off and then back on. Finally look at the Red RPM trace, notice the peak and where the slope changes. Now I'll add in cursors at the clutch switch transitions.
You must be logged in to view this image or video.
Clutch up, down, and back up in .357s, average stuff is in the .5-1s, and some really really good guys get it done in .25s. Now here's a neat one - I'll move the cursors to the points where the clutch actually releases, and then grabs.
You must be logged in to view this image or video.
.280s! That's the clutch disc going from 9200 down to 5600 in .28s. That's crazy!
What's even better about this is the trans is all old beat up junk. It's a used 1/2 slider and synchros that I bought in 2008, and have been using since! For comparison, last fall I was experimenting with a Tilton Twin Carbon, and I was getting shifts (clutch up/down/up) in the .32s range. I was also running a face-plated gear set last summer - even clutch-less shifting only using a blip of the throttle to shift it, these averaged about .30s throttle up-down-up. To give you an idea how quick a .30s shift is:
You must be logged in to view this image or video.
The secret to getting shifts this quick is simple, get the clutch to release. Look for a new tech thread on this soon!