correct stall speed & launch rpm

[Ian Turgeon]

I'm trying to chase down a launching issue where it takes me a long time to build boost.

(stock converter)
what rpm/tps% are most people at before the truck begins to creep?

I'm assume my problem is with my converter having a low stall speed, because everytime its right at 2000rpm, 100%tps and boost build VERY SLOWLY.

this is even with an external that isn't opening. It will eventually build up to 7-9lbs where the brakes cant hold it back anymore, but staying at the solid 2k rpm.

Am I right in thinking this rpm is an indication that my converter is stalling at ~2k rpm? And is it normal?

I've compared mine to 2 others by looking at recorded runs, and they are getting up to 2800ish before the computer registers speed.

 

[Christian Dionne]

"Double A, beep beep, M C O"

I can't believe you get 100% TPS on stock brakes @ 2000rpm.

I remember mine would goto 2400-2600 at 5-10psi on manual cylinders.

I also remember 2800 before speed registered, but it was 12 mph or so. I don't believe that is very accurate info from the datalogger.

I have almost 100 runs on datamaster on my laptop you can look at. Bring over your Diacom runs and you can compare them side by side.

Wanna help remove a 9/11 this weekend

 

[InvisiBill]

I've never really heard much about it here, but the manual says that boost is cut when the brake is held down and throttle is at 100%. But if you have an external wastegate/controller setup, that shouldn't matter... *shrug*

 

[Tooky]

Something seems off. My truck makes 2-3 PSI around 2100 with original stock trans and converter with 49K mi. If I look at my DataMaster , the first frame on a launch where it registeres positive speed in MPH, its around 2800 RPM which is consistent with Christian's experiences. Was your tranny rebuilt? Maybe you got a regular N/A 4.3 V6 low stall speed torque converter. That's interesting - how does your truck drive compared to other stockers?

 

[Ian Turgeon]

yes it was rebuilt, and thats why I'm after some answers with this.

I dont know if I can get a proper tc outa the company now that its outside of its service window, but I did want some ammo to take to them as evidence that they gave me the wrong parts.

as far as boost, it will build. but its slow as all hell. I now know why I've had lame launches in the past, it always seemed like it was time to go way before I had the right boost. I can get it to 1-3psi positive in a few seconds, but if I'm aiming for that sub 1.8 60' at 7-10 psi, my reaction times become rediculous.. 8-9 seconds.

a good comparison between mine and adams (both "stock" converters with same mods) on the video below. You can see how long it takes to build boost, and I only got up to about 4psi in this one. Meanwhile adam is creeping past his brakes in 1/3 the time.

http://fast.sytyarchives.com/Bradenton/Desoto Race Day 26 Jan 03-Adam-Ian2.mpg

 

[Loeryder]

Have you compared your shift points (RPM/Speed at shift) to Adam's?

It sounds to me like you may not have gotten the correct internals for the SyTy trans when they "rebuilt" yours.

Hopefully it is stil the same case, if its not I'd be willing to be they just swapped out the trans for a shelf stocked rebuilt unit.

The stock converter stall speed is 2100RPM, but of course it can very from one TC to the next. You may have gotten one on the lower end.
You can have stock converters restalled if you don't feel a 9/11 is necessary just yet.

 

[Ian Turgeon]

I will have to look at the shift points, from my experience they tend to very on everything ive seen.

it does shift into od at wot, so one would believe its probly the same case. I do know for sure they removed the junk outa the old case, but didn't think at the time about them swapping a fully built in as a replacement.

I was very explicit at the time that they reuse what was usable because these were not the same as the rest of the s-series trucks. Turn around time was definately slow enough to suggest they did work with the parts on the truck.

(this was about 3 years ago)