spatton100

I have been trying to figure out if an engine sees the intake port as being smaller according to the type fuel used. A typical gas engine requires ~12-14:1 AFR which in a 210cc intake the fuel would take 17-19cc of volume if I figured right which would only leave 191-193 cc for air.
Now if using E85 the AFR would change to 8:1?? which uses quite a bit more volume leaving even less for air.
Would this in turn speed the port and change area requirments.
Any Ideas on this anyone??

Steve Bryant

iTrader: (1)

This is an interesting question. Generally, the intake port volume would be selected for the port velocity versus the flow rate at high valve lift levels. In other words, vehicles that want to emphasize broad RPM range for torque and HP production as well as part-throttle and wide open throttle operation are benefited by the higher velocity smaller runner intake ports. Engines mainly designed for WOT only would benefit from higher CFM.

Now you are asking if the incoming mixture is so charged with alcohol mist with an 8:1 AFR, would bigger ports be better (if I'm understanding your question). My opinion is that with a port injection system like the LS series where the injector spray cone is directed at the back side of the intake valve, the use of alcohol versus gasoline won't make any difference in port volume preference. You should still select the port regardless of your chosen fuel. Again, that's just my opinion.

Steve