Trying to Control the Surging..

My setup:
572 Fuel Head Hemi
LB20 14-71 35% over
Timing is set at 32 degrees
1200 Enderle Pump Fresh
BAU with 5 9/16 butterflies
Blades set at .012
Leak set at 83%
Idle Check is 9lbs
Port Check is 23lbs
High Speed is 60lbs with a 60 jet
Pump Sizer Loop is 23lbs with a 85 jet
Pump Saver is 150lbs

It is a converter car. Idles around 1800 and has a significant surge to it. Does anything stand out that I am doing wrong that may cause this?

 

Can you take the output off of the pump sizer to see if it’s cracking at idle? I think it’s possible if it’s right on the pump outlet.

also, unrelated, have you run this combo? How long are you in the converter before launch? 2-step, throttle controller, or both? What launch rpm? That port check is pretty high. If you’re wide open against a low 2step on a quick pro tree you’re probably not opening the ports until way after launch. On a converter car that goes WOT on the brake, you get boost in the port distro before the port check cracks so now fuel pressure has to be greater than boost plus port check crack before you’ll get the ports open. That’s probably right where your high speed is at too so seems like it could get dicey

 

You can always make the barrel valve richer. Some hats just don't idle good. I've also seen the butterfly shaft be twisted from too big of return springs and cause idling issues trying to suck the blades closed making a surge as well.
Is the coil on plug by chance ?

 

all of the above is a good base line -
1- open the butterflies first - idle will go up, surging will stop, let engine clear up
2- richen the BV until you get desired idle, let engine clear up

you will go through a lot of fuel doing this...

 

I have run this combo. I'm on the converter for about 1 sec, on the two step set at 3500. What are your recommendations?

 

No sir. Its a Promag 44/grid setup. On the throttle return springs, don't you want a spring on both sides or just one side?

 

I use 1 spring that is just enough to bring the throttle back. It's one of the softest ones I could find. Also don't worry about the leakage. Most of the time those are just starting points. Try lengthen the barrel valve 2 flats and see if that fixes it. My carbon hat will idle around 1100 Rpms if I need it to without surging. But I also run the barrel valve rich.

 

Use two hat nozzle ports (1/8" NPT), fit one with a jet (Ø - TBA) and a 1/8" NPT pneumatic flow control valve in the other port to fine tune idle speed.
https://www.mcmaster.com/45045K36/

 

Check that flow control valve before & after every pass for tightness. The lock ring can loosen on vibration. If it fully disassembles on a pass it becomes a nail to run over.

Chris Saulnier - Team Tigges
Mechanic Falls, Maine

 

Good point Chris.
The McMaster Carr one was shown as an example ..... maybe find a more heavy duty unit that could accommodate a lanyard or some other type of safety retention feature.