Would 112 octane gas help out an N/A engine? and if so...how much? thanks...

 

Hot Rod did a dyno test using tuned SBC motors (350's), changing timing and seeing the differences in how the engine benefits. I think the biggest gain was from jacking timing way up and using 115, that was worth 20 hp from 87 octane baseline. Don't bet on it being enough of a factor, especially for 5 bucks a gallon and 100 ci less. The motor simply won't take much advantage of it- the guys with turbos however can use it to reduce knocking in their cars when the boost is turned up. They also showed octane boosters as being detrimental to performance in some circumstances, and gains of only 2-3 hp in others. I would be interested in seeing what my motor would do on the dyno with say, 110 octane unleaded race gas, but I'd be suprised if it made more than 5 hp.

 

As mentioned, you have to advance timing to take advantage of the higher octane... Advancing the timing raises cylinder pressure slightly which makes more power. I would guess with lots of tweaking on a timing controller like an Apexi ITC, you could probably get 20hp or so. On a turbo SC300 you can get as much as 100hp extra . The difference is in the cylinder pressure... A Normally Aspirated engine can only build up so much pressure at 10:1. Turbo's effective compression ratio under boost can go 15:1 18:1, 20:1 , who knows.... That's where you need higher octane to resist the mixture from spontaneously exploding instead of buring after the spark is introduced.

If you could somehow raise the compression ratio on the SC300 to 13:1 (different pistons?), you'd see a big difference when running 112 octane. Problem is the car would run and idle poorly on normal gasoline.