Idle Surge In Gear

Having the same problem. Surges so bad its hard to get it in gear. Idles (but surges bad) at 2200-2400 but then its harder to stop the car after burnout or backing up. Brake pressures are good.

Pro mod, Bruno, Neil Chance convertor, Lenco 3 speed.

526 BAE Hemi, CFH heads, Kobelco HH 29%, Rage 18 GPH pump, Mag 44 at 28*. Pump PSI is about 45# @ 2200RPM port nozzle is "0" so I don't think they are leaking at idle. Idle check is 8#, BV leak is 80%. Port check pressure opens at 8# with a stiff spring. JBR 4 blade injector is .012 all the way around the blades. EGT are all around 4-500* with the exception of cyl 1 (6-700ish) and cyl 4 is (4-500ish) Flow meter shows less than 1 at idle. We have an adjustable air valve on the BV as well as have pulled lean out plugs in the hat. Turn the air vale all the way open and pull a 5/16 plug and it cleans up very very slightly. I would assume the change should be drastic with such big openings.

We have had idle check PSI everywhere from 4 to 12 PSI without much difference. BV from 84-76% without much difference. Changed hat nozzles to ones with out air bleeds (saw no difference) also reduced the hat nozzle area down some. (saw no difference). Changed timing to 30 and it cleans up and idles better. (they tell me 30* is to high to be safe.)

When you push the trans brake button to stop the trans the surge gets really bad, let off it goes back to just bad. We have an MSD grid that we have retarded the timing at launch- release of the button, and also set it up with no retard. Engine still surges really bad when button is on, bad when its off weather we retard the timing or not.

Breather tubes on valve covers are open.

We are trying to get it to idle at 2200 ish with no surge and 28* timing.

WHAT THE HELL ARE WE MISSING... Damn this is frustrating. Thanks for any advice.

 

Wow 28? Hope you have like 10-1 compression. And 2200 idle with 1.0 fuel flow seems lean. With that amount of timing and fuel says a very lean condition to me. Have you tried 25 degrees and then see what happens. Or warm it up and pull the valve cover breather tunes off while it's on the brake in the pits? I was on the dyno and the tubes were open or so we thought. Pulled the tubes off and whalla , beautiful idle !! Same exact thing your describing to me now

 

Lean. Seal the hat and if you're using a spacer be sure to seal it good as well. Mine was surging bad even after setting blade gap, BV, etc. New gasket between hat and spacer and new o ring between blower and spacer cleaned it up. Idles smooth as glass right around 1700. Also try dropping your timing down to 26* and see what it does.

 

Jay-Compression is about 11:1. Breather tubes are off when we are doing this- on Pro Jacks.

TD- We have resealed everything- o-ring and silicone on everything. Even sealed up the front of the injector where the aluminum frame for the butterflies is attached to the injector. We have had timing from 18* to 30*. As expected at 18 its so fat, lazy it barely wants to run.

Mike- We have tried exactly that when setting up the barrel valve. Even thought maybe the spool was modified so I bought a brand new BV and nothing changed.

Some more things I thought about:
1-It uses fuel like crazy at idle- to me that's rich??

2-Could it be leaking (sucking air) in the lifter valley? The intake not sealing to the heads type problem? I would think when we cracked the throttle we would see smoke out the pipes because it sucked oil??

3-The Racepak pan pressure sensor is located in the intake oil cap, where you would pour oil in the back where a traditional distributor would go. Its reading 0.1 or 0.2. I don't know what normal is because we have never used one. If it was sucking air through the intake/ heads wouldn't the vacuum be higher on the sensor?? Is there a such thing as normal vacuum / pressure at idle?

4- On regular engines you can spray carb clean or use propane to check for vacuum leaks-idle raises up when you hit the leak. How could we do it on this?

 

Have you checked the cam timing and for a bent or broken valve?

 

We have not

 

Might sound silly but silicon didn't work for me in regards to hat/spacer sealing. I found a nice gasket from RBS that worked great and the surging stopped. You may want to give that a shot? Also maybe try simplifying your fuel system setup. More poppets more problems. Just my .02

 

I'll look into the gasket. We have capped off the ports and just tried it on the hat and same surge.

We just tried starting the car and measuring PSI at the dist block for the hat nozzles and get -5 or -6. Is that right? Shouldn't it have pressure? also switched the sensor out and the same thing with a new sensor.

However with no other changes the pump pressure measured at the pump is now 35# at 2200 rpm. We have not changed anything else and it was 45-50# yesterday. WTF!

 

Is the oil saturated more than normal? Have you checked your pump seals? Might be leaking where your extension is. Would explain the fuel being used at idle, the drop in pressure and the lean-rich-lean-rich condition causing the surge. That pressure at the block doesn't seem right either

 

The oil really isn't to bad. The pump was sent to Rage and was checked out as good.

What should the pressures be? I know you cant say exactly but whats a normal range on a Racepak?

Pump pressure measured at the pump?
Pressure after the BV measured at the hat dist block?
Flow at idle?
Pan pressure at idle? Can it be negative (vacuum)?

 

We have gone clear down to 76% with no luck.

 

The idle ck. could be worn - how old is it?

 

We put a new one in and even switched it with the pump saver one to make sure.

 

that wont work----

 

Who's blower? I had a customer buy a used Littlefield blower. LB20. I could not get the motor to stop surging. Found out previous owner of blower changed the rear bearing plate for one that was machined out for a standard rotor instead of non machined hi helix rear bearing plate. Littlefield told us what to look for. Changed rear bearing plate and surging went away. Just a thought.

 

Its a Kobelco that we had dynoed at SSI. They said everything was good but it something we can check into.