CFM Continued...

[Todd....!!]

Fred,

You're probably aware that a 30+% loss can be attained by using a stock
or aftermarket WET (Made for Carburetor) intake for a fuel injection
application (No turbo's involved)

With this in mind, I believe a gain of 10-30% in power and gas mileage
attained by switching from carb to FI would be negated by the lack of
efficiency due to this phenomenon...

what are ya'll's thoughts about this?

This is kindof worrying me and is also beginning to make me double think
my twin turbo FI 440/451 project...

Thanks!

Todd....!!

----------

Frederic Breitwieser wrote:
> 
> > a stock 350 ci engine.  I’m looking for an EFI intake system for my twin
> > turbo 434 ci engine.
> 
> Aaaaah.
> 
> > The guy putting the turbos together said that the stock TPI is a good choice
> > because it will give me something really important for a fun to drive street
> > car, great throttle response and low end torque.
> 
> This is true, because the runners are smoothly curved, and long.  Typically
> longer runners give you more low-end torque, however at higher RPMs your engine
> will wease to death.  Several manufacturers have come up with variable length
> runners... the one that sits in my mind is the new Ford Taurus... long runners
> for low end grunt, and shorter parallel runners for higher RPMs.
> 
> Instead of a 2500/3000rpm spool up range you could size for smaller turbos and
> have them spool up faster, thus taking even more advantage of the longer
> runners... but then your high end will suffer from runner length as before, but
> even more from grossly undersized turbos.  but, it will take off the line quite
> nicely.
> 
> I'm doing this with my Dodge truck actually... 383 cid stroked to 431, two small
> turbos, then a max RPM of 4000 RPM.  Great for towing, not top speed.  Its a
> 6000lb truck anyway :)
> 
> You might get more performance by using a much larger throttle body, and doing
> some runner port work.
> 
> > with 15 lbs of boost it seems to me that the stock TPI is still small for a
> > 434 performance engine, or will the boost really make up the difference for
> > the small tubes?
> 
> I believe the velocity would be too great for your engine... but I am not an
> expert in this area.  For my dodge engine, I've already drilled out the
> manifold, welded in injector bungs, and going to use the TPI GM setup to manage
> the dodge motor, and instead of the GM TPI manifold, I'm just using the dodge
> intake with all the GM "stuff" attached.  You might consider that approach for
> your engine... chose a carb manifold that suits your needs and application, then
> mill into it some injector bungs.  Its a fair amount of work, but in the end I
> believe its worth it.
> 
> --
> 
> Frederic Breitwieser
> 
> Xephic Technology
> "Leadership in IT"
> Bridgeport, CT 06606
> 
> Web: http://www.xephic.dynip.com
> Voice: (203) 372-2707
> Fax: (603) 372-1147