You got to love that figure, 7psi. Almost every post in regards to this all agree on this and hover around the 6-8psi figure.
I know some have actually implented this but when most ppl say it it's been recycled info (not attacking anyone here )
If you drop the intake air temparature you change the PSi, so you could be getting more cubes from less pressure. Cubes is what forced induction is doing for power.
So some ppl might get 7psi at a certain temparature and get reliability then other people (perharps in colder climates) set there bypass/blow off valve to 7psi and there engines have a short life.. All because they flowed more cc's when into the same chamber.
You might say well it's the same pressure going in so whats the difference. Well when the valve shuts and piston pushes up.
Imagine a 1324cc G13a. divide by 4 cylinders you get 331cc a cylinder.
With compression Ratio of 8.9 :1 Your 331cc gets squeezed down to 38cc.
That 38cc doesn't change. That's the point you got more fuel and air being reduced to the same size (the eqivalent of higher vcompression)
So at a lower temperature with the same psi (let's say 50cc between temp A and B) more air is going into the chamber and compressing down to the same 38cc you have a lot more strain on the engine trying to compress the gasses and when the bang comes more stresses on the drivetrain trying to channel the power.
I think the solution is in controlling how much cc's a flowing into each stroke and THEN controlling the PSI by reducing temparature, maximising flow in the intake etc etc.
I'd be interested in seeing someone do a 2psi Set up. Sound silly but think about the fuel economy and responsiveness of something with 100% volumentric efficiency 100% of the time
![Smile :)](./images/smilies/icon_smile.gif)
Negate all those losses from the mass cast heads, smaller valves and consevitive cam.
With a positive displacement supercharger you could do ths by working out the ratio in the pulleys in relation to the engine cycle maybe adding a little to account for loses and tuning from there... turbos wouldn't be ruled out but to me it's a lot of homework to get it flowing and tuned to match a blower. a Lot of expertise most of us simply don't have... so why argue that everyone should choose it over the other?
Oddly enough. I am turbo devout. But give me an engine family that doesn't come in turbo and i chase the simplicity and cost vs benifits
-[b]Santos[/b][img]http://www.teamswift.net/images/smilies/icon_furious.gif[/img]
Suzuki, Jeep & Toyota Soft tops with welded seams for SALE (PM me)