Higher-Octane Gas Could Improve Fuel Economy

[Fast355]

I would think that E85 with 13:1 statc c/r would do well. Although supposedly when using true R+M/2 ratings, E85 comes down to 94-96 octane. Some of GM'sGM's stock calibrations were upping power by 15 sae Cert hp and 20-30 lb/ft on E85 over gas.

Is that 100 octane Sunoco you can get at the pumps out West rated at R+M/2?

I was able to get a 9.8:1 engine to run very well on E85. The factory ran the intake cams relatively retarded at low-mid loads and only stepped up the advance under heavier loads and higher RPMs, then retarded the cams very quickly after peak torque. I remapped the intake cam advance to fully advance under less load, stay more advanced for a bit longer and pulled down 398 RWTQ @ 2,980 from a NA 5.6 on E85. I was able to run a substantial amount more timing advance off-idle and through the midrange as well. Also did not have to retard the timing (up to 35-37*BTDC) up top after leaning out the very rich factory calibration like I did on 91. Ordinarily my change from 10.8:1 air/fuel ratio to 12.6:1 required retarding the timing down to 32-34* BTDC.

Cams are 232/244 @ .006, 199/210@ .050, .375/.385" lift, exhaust lobe center of 112* and an ICL ranging from 94* to 124*. LSA can be as tight as 103* or as wide as 118*.