So I managed to hook up with a local club doing a dyno day to get a few runs on the dyno. The TBI is a holley with 85lb(@20psi) injectors running at 15 psi. I computed the adjusted rate to be about 73lb/hr. The cam is rather large for a 4.3L (222/230@.050, 112LSA, .519/.531 total lift). Overlap is 64 degrees off-seat and 6 degrees at .050. Here's the cam card if anyone is curious. It's installed 4 degrees retarded, so intake opens exactly at TDC. Cylinder filling seems awesome, because I have to basically lie to the ECM about how big my injectors are so I can even fuel part throttle and still have some headroom for the VE2 table (7747 ECM)

Now that you have some background, I have had many a complaint from people who were unforunate enough to get caught in my wash that the blazer smells like raw fuel from behind when I go all in. The wideband from the dyno seems to disagree, and says I'm only blowing 13:1? Is the overlap from the cam skewing the wideband result? I tried adding more fuel on the final pull, but the fuel curve really didn't change much. I'm thinking the next step is to raise the fuel pressure to 20, pull the VE values back (again!) and try again. Also, the blazer does have a cat, and the WB sensor was the tailpipe sniffer variety.

For the record, the ECM currently thinks I have 64 lb injectors, and VE1+VE2 goes from 95% to almost 100% between 3200 and 6000 rpms.



Am I on the right track here, or is the dyno result just misleading?

Teeleton

 

A WB infers a AFR based on O2 content.
There is no way it can figure out the effeciency of the *burn*. So advanced timing can read lean, and retarded timing, rich.

If your relying on their WB, I'd say forget it, and get your own. The maintance some shops devote, and time they get out of sensors can lead to inaccuracies. Not to mention you don't know what sort of fuels or additives it might have been exposed to.

Not to mention give the engine what it wants, not what you think it needs.