BBC Accel Gen7 tuning problem

[Denvervet]

Bucking until about 2000 rpm and getter better about 2200 rpm. And yes I assume the overlap duration as the cause and just wondering if there's any tuning tricks with accel efi to best deal with it. Understand it maybe the nature of the beast ...literally. I haven't spoken with anyone with this motor that's carbureted to see if same issue. I 'm sure being a mile high altitude doesn't help either.

[supremeefi]

Didn't I send you a cal or something a couple of years ago?
Send me a datalog. Make sure you include timing, O2 actual and correction, TPS and MAP. My email is [email protected]
Have you verified your timing? It may not run real smooth at low rpm due to camshaft size but typically you shouldn't have to run it that fat either.

Happy to help.

[GregWeld]

Originally Posted by Denvervet

Bucking until about 2000 rpm and getter better about 2200 rpm. And yes I assume the overlap duration as the cause and just wondering if there's any tuning tricks with accel efi to best deal with it. Understand it maybe the nature of the beast ...literally. I haven't spoken with anyone with this motor that's carbureted to see if same issue. I 'm sure being a mile high altitude doesn't help either.

I hate to bring this up -- but many times I've found that there is a simple MECHANICAL issue with the motor or install - which confounds the electronics. Simple as in - an exhaust leak. Bad weld on the O2 bung. Valves not lashed correctly. Valves not seating.

Sometimes it takes a leak down test to discover the issue, or a cylinder pressure check or both (leak down should find it).

I've also found that what SMELLS like unburned fuel -- is actually caused by a LEAN condition where the cylinders are too lean to light... thus the unburned fuel. This happens usually when the untrained tuner attempts to "make" some number rather than looking at what the engine wants. What it wants is an idle fuel ratio that gives the motor the highest RPMS and VACUUM --- no different than when adjusting a carburetor! For whatever reason people tend to forget this simple basic when tickling the ivory on the keyboard.

So on top of having Supremeefi look at your tuning -- I'd be also checking for some of the most basic engine health issues.