Throttle Pumps and 50mm TB's
 

Im using 50mm throttle bodies, my off idle response is terrible.

Can I get some advise when setting throttle pumps

Is it bogging or hesitating?

Bogging = too rich
Hesitating = too lean

itll flat out die if I just punch it at idle.

First thing you need to do is get the base fuel map right. No amount of throttle pump manipulation will correct that.

Next, what system are you working with? What is it installed on? Is the TPS reading full range and properly calibrated?

The map is done, cars been dyno'd and pulls smoothly, everything is kosher except for the the off idle throttle pumps so far.

Im using an e6x on a lightly ported 6port 13b, TWM 50mm down draft, 2nd gen ignition

everything should be calibrated and zero'd out properly.

I did notice last night while reviewing things that the dead band was set to 0. Going to bump that to 10.
I cant do any more tuning till the weekend.

Dead band will probably work best at about 1-2. 10 is way too much and you can get phantom fueling with it set at 0.

Adjusting the throttle pump feature is pretty easy for what you want to do. You're only looking at the 0 rpm and maybe the 1500 rpm range. Stab the throttle. If it's lean bogs, add increment. If it stumbles from being fat, remove increment. Decay rate is how long the additional fueling is sustained. If the initial stab of the throttle is crisp but then the engine leans out, add decay rate. Repeat this process from 1500 and them 3000 rpm. It's all trial and error and done pretty much by feel.

awesome and thanks.

One other thing you might be running into is the size of the chokes just being too big for the engine. If they are, when you crack the throttle wide open at low engine speeds, the air will stall and you'll get a big bog. There is no way to tune around this. Only way to remedy it would be a smaller choke size.

with a carb, that would mean after the accel pump shot the main circuit isn't working yet, or simply its too lean.

;)


Told him to make sure the base fuel map was right and he was quick to say it was.

yeah, so maybe max out the accel pumps? and retry? it would be nice to see the car for this

I put a set of TWMs on a stock port GSL-SE engine years ago and had a similar issue. I feel the choke was just way too big for the small port engine. Off idle was never as crisp as I would of liked it. Get it up over 1500 rpm though and it was quite snappy. That engine is a 4-door 510 with a stripped interior and a good suspension is a HOOT to drive. :D

http://youtu.be/AXstiayVuQo

Still working on this or should say I just got back around to this project.

you may be right about the 50's just being big for a stockport.

178rwhp the way it sits in that video

I thought I would update this. I managed to get pretty good response from 1500 rpms and up, however off idle still stumbles pretty hard if you don't roll into it. Pretty much as C. Ludwig noted.