Date: Sat, 08 May 2004 21:55:53 GMT From: Andrew F. Dicker <a.dickernospamast.net> Subject: Re: Compression ratio w/turbo blowing ?
On Sat, 08 May 2004 16:03:04 GMT, -Bob- <uctraingNOSPAMMEnospamanet.com> wrote: >On Sat, 8 May 2004 17:21:29 +0200, "MH" <nomailnospamere.no> wrote: > >>The compression ratio does not depend on the boost pressure, it is the ratio >>of the smallest and largest volume in one cylinder (piston at TDC and at >>BDC). >>see http://en.wikipedia.org/wiki/Compression_ratio >> >>Max boost pressure in a FPT 900 is 0,7 bar (over atmospheric pressure = 1 >>bar), at that pressure the waste gate will (or should) open. > >But wouldn't the "effective" compression ratio be higher since the >charge is denser than a normal charge ? Or does the turbo simply make >the pump run faster ? -------------------- The turbo boost fills the cylinder (at TDC) with more air (fuel air mixture), or if you will is pre compressed ("boosted"). The **RATIO** that volume (as explained above TDC [Top Dead Center/piston head at top] to BDC [Bottom Dead Center/piston head at bottom] is compressed remains the same as if the cylinder had 'only' a normal atmosphere's worth of fuel/air mix. To restate: the turbo stuffs more air/fuel mixture into an uncompressed (by its piston) cylinder, but the *ratio* of the compression from largest to smallest cylinder volume - by the piston - remains the same.