390cc vs 318cc? anyone know the gas mileage difference after tuning, apples to apples, etc.

98' s/c runner

 

where did midiwall go he should be able to answer your questions

 

Ill give it a minute before he posts. always shows him offline, then bam he posts.

 

318's are plenty with the usual upgraded S/C stuff (headers, intake, smaller 2.2 inch pulley) Midiwall will be using 370's but has all that plus some head work done and aquamist. I was planning on using 440's with my turbo set-up but was told by URD that they are very hard to control at idle and part throttle with a piggyback fuel control system (FTC).

When I had the S/C in with 318's, my mileage dropped by about 1 mpg over just the S/C and stock fueling. I am sure this is due in part to a heavier foot with the extra power though..

 

318 seems to be plenty, I'm running a little too rich at WOT even after tuning the FTC to 8.9 in that area of the map. I am running 50% methanol in the WI though. The unknown to me is how close to max duty cycle I'm at.

 

running rich with 318cc injectors...so does that mean with a s/c, ftc, urd fuel upgrade kit....i'll be really rich with 390cc? Running stock headers right now...I just want to keep the rig reliable, get no worse than 15 mpg, and have around 300hp. I will eventually get the mister from URD. URD had the 390cc selling much cheaper than the 318cc so I grabbed them before asking these questions! Gadget indicated that I'll be ok with the 390cc...from all I've read, he seems to be "the" trustworthy source on the topic. just want to be sure before installing the lil bratts....many hours to do so!

thanks guys!