High stall converter, sluggish launch?

[DartorDemon]

I'm trying to figured out some of the issues with my car as a recent track trip was pretty dissapointing. So today for S&G's i thought i'd go out and try some hard launches with my car's 3000 stall converter. The cam i have in the car called for a 2800rpm converter, but i went 3000 due to a good deal and thinking that 200rpm shouldnt make much of a difference right?

I tried several different techniques:



-Foot on the brake, very light on the gas, release as i roll into the gas
-Stall up just before tire spinning, release while quickly laying into the gas
-Stall up to spinning and launch

The problem is that every time the car just fell on its face gave a rather piss poor launch. So i much so that i think it the car got off the line quicker when i just stabbed the throttle.

This is a PTC 3000k converter on a mopar 904 transmission with an unknown number of miles.

I meal isnt a stall converter suppose to have a full launch thats akin to launching a stick car at said rpm? I wonder if maybe its the transmission itself thats slipping on the launch??

[carguykeith]

Are you 100% sure its a trans thing, sounds like the engine may not be able to handle the load. You need to have a lot of timing and the right AFR at launch to footbrake with good traction. Are you carb'd or FI?

[DartorDemon]

Well now I'm not entirely sure. I'm running an edelbrock carb setup. After I posted this I read a small blurb about having bog issue on a launch because of the accel pump. So I moved the pump adjustment to its max shot position and went for a ride. I couldnt try any launches, but it made a massive difference in how the car would react on just a wot hit.

[carguykeith]

Sounds like you're onto something, try some launches and see if things inproved. I think a carb can run almost as well as fuel injection, you just need to tune it right. The absolute best investment I've made in my money pit of a car has been the wideband O2 sensor and analog gauge setup, probably less than $250 total cost and has been amazing at helping with the tune!

[DartorDemon]

Sounds like you're onto something, try some launches and see if things inproved. I think a carb can run almost as well as fuel injection, you just need to tune it right. The absolute best investment I've made in my money pit of a car has been the wideband O2 sensor and analog gauge setup, probably less than $250 total cost and has been amazing at helping with the tune!

Well the carb setup is temporary. I didnt want my money pit to include 2k worth of efi parts if it wont run well on an carb.

I may need to spring for a wide band setup. Do you run just one sensor on one bank of the exhaust or two sensors?

[sam 74]

when there is a problem with launching, or hitting the throttle in general and there is an issue the first thing i look at is the accelerator pump adjustment.

[carguykeith]

I made the same choice, it should at least run good enough on the street and pull hard at the track with a carb to know if I'm happy with the drive-train. I bought the carb used so figure I can get most of my money back when I go FI.

As for the O2 sensor, I'm just running one sensor and figure as long as I do everything the same on both banks and check the spark plugs every once in a while it should be fine. Hell the manufacturers have been doing it forever that way... After having an AFR gauge I wouldn't have a project without one and would even keep the gauge after going FI.