Tuning stock L-jet
Posted: Sat Aug 04, 2007 9:28 pm
I'm trying to get my AFR dialed in on my '78 Bus with stock L-jet. This is a bone stock 2.0 with around 80k miles and no known vacuum leaks, fuel pressure within spec and rebuilt injectors. Last compression test had all cylinders at 120-125psi. This same FI is going to be going on my Camper Special so I want to get it as close as I can before making the switch to the new engine.
Using an LM-1 I got the AFR to 12.8:1-13.0:1 at WOT up hill in third doing 40mph. I think this is very close to where I want to be but at highway cruise or light throttle cruise and at idle it leans out to very near stoich, 14.5-15.0:1. This runs the head temp up to high (380°-400° using a Dakota Digital gauge). Double checked the timing and it is at 28° at 3500rpm with advance hose disconnected. It falls back to 8° at an idle of ~1000. This is using a stock 205P distributor. With vacuum hose connected it advances to ~34° at 3500rpm.
I've adjusted the black wheel in the AFM to get to the WOT readings. Also a very small adjustment counter clock wise on the AFM potentiometer using the small screw. As I understand the AFM, the black cog or wheel adjusts the "MAP" of the mixture and the small screw adjustment changes the MAP up and down the rpm range? Is that correct or totally wrong? What adjustment should I make to bring the cruise AFR into line? Or is stoich what I want at cruise and my high head temps are caused by another issue? All of these readings were taken with ambient air temps of ~75°.
Any suggestions?
Using an LM-1 I got the AFR to 12.8:1-13.0:1 at WOT up hill in third doing 40mph. I think this is very close to where I want to be but at highway cruise or light throttle cruise and at idle it leans out to very near stoich, 14.5-15.0:1. This runs the head temp up to high (380°-400° using a Dakota Digital gauge). Double checked the timing and it is at 28° at 3500rpm with advance hose disconnected. It falls back to 8° at an idle of ~1000. This is using a stock 205P distributor. With vacuum hose connected it advances to ~34° at 3500rpm.
I've adjusted the black wheel in the AFM to get to the WOT readings. Also a very small adjustment counter clock wise on the AFM potentiometer using the small screw. As I understand the AFM, the black cog or wheel adjusts the "MAP" of the mixture and the small screw adjustment changes the MAP up and down the rpm range? Is that correct or totally wrong? What adjustment should I make to bring the cruise AFR into line? Or is stoich what I want at cruise and my high head temps are caused by another issue? All of these readings were taken with ambient air temps of ~75°.
Any suggestions?