Hello guys, This is my first time posting on the forums. I have a few questions about carb tuning according to the readings I get from my wideband in my fc. I realize this is more of a muscle car chevy forum kind of question but it seems like for the most part those guys don't use widebands to monitor their afrs and tune, so I had hoped maybe there were some carbed v8 gurus here in the forums who were also runing widebands and could give me a little input. Anyhow here goes, I have a CHEVY 302 build in my turbo 2 fc, its the high rpm motor modeled after the 1st gen camaro z28s, anyhow I have noticed on my innovate wideband that it is very common for me to be cruising along in the 14 and 15 afr range (where I want to be) and then when I decelerate in gear my afrs get very rich (usually in the 12s). It seems this may be due to a high vacuum condition with the throttle closed in gear and may be a common problem, I'm curiosus if anybody else has run into this. My other concern is that when I'm cruising along in gear and then put the car in neutral and/or push the clutch in to coast my afrs get very lean for a few seconds before going back to my 14-15 afr idle ratio. I'm wondering if anybody else with a carbed v8 and a wideband in their rx7 (or any car really) has noticed anything similar to my symptoms or perhaps has suggestions which could help me out. Thanks

 

The slight richness on decel is caused by the high amount of vacuum under the carb. With the throttle blades closed the motor can't pull enough air to make up for the excess fuel being pulled from the idle circuit.

As for the other concern, that's normal as well. It won't (shouldn't) hurt anything since there is no load on the engine.