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Well put indeed! At 11:53 AM 10/28/99 -0500, Doug Cutler wrote: >Well put, Watson ! > >R Douglas Cutler > > -----Original Message----- >From: shammar@nsk-corp.com [mailto:shammar@nsk-corp.com] >Sent: Thursday, October 28, 1999 7:17 AM >To: rawant@webtv.net >Cc: turbobike@natvideo.com >Subject: Re: [turbobike] Turbo horse power vs compression ratio > > << File: att1.html >> >That's an interesting and often observed phenomenon. The real question >is, is >it an illusion? Often one's perception is so blinded by the big hit the >turbo >affords up top, that one believes the low end power has been sacrificed. > We >usually find that the power curve never drops below stock unless >something is >wrong. Maybe there is more tweaking in the carburetion that needs to be >done. >Do you have dyno curves before and after? Have you ridden a stock one >again for >comparison? This situation is a lot like when you put nitrous on >something. >After getting used to the big hit, it kind of feels like something's >wrong with >the bike when you twist it without nitrous. Then you realize it was >that slow >all along. > >You can generally make more peak power with less compression and more >boost >unless your compressor is maxed out or beyond its "good" efficiency >range. >Reducing the compression ratio (CR) reduces the peak cylinder pressure >(PCP), >helping to reduce preignition/detonation and reducing the maximum stress >on all >of the components. One might believe that this would reduce power, and >this is >theoretically correct, assuming all other things are equal. But PCP >occurs at >only one slice in time over the power stroke event. The Brake Mean >Effective >Pressure (BMEP) is a measure of what you really have to work with over >the >entire event. By using a reduced CR and packing more mixture into the >cylinder >(via more boost) you can increase the BMEP above what is was before you >reduced >the CR, and end up with a similar PCP. This way the maximum stress >stays the >same but you make more peak power. Of course, this is where you do lose >low end >(off boost) power since there is no additional charge when you're off >boost. >For true street use, less boost and more CR is usually better and >results in a >more linear power curve (if there is such a thing on a turbocharged >engine). > >In practice, getting it right is a delicate balance between chamber >shape/design, boost level, intake temperature, CR, squish, and ignition >timing, >not to mention matching the proper turbo to the application. More >displacement >will always help fill in the bottom and make boost sooner. > >Later, >Bob > > > > > >rawant@webtv.net (RAW ANT) on 10/27/99 08:42:22 PM > >To: turbobike@natvideo.com >cc: (bcc: Bob Shammas/EQA/Nsk-Corp) >Fax to: >Subject: [turbobike] Turbo horse power vs compression ratio > > > >This question is for anyone that can help. >Well my turbo system is complete. I notice that I have a lot less low >end power. Could this be do to the turbos back pressure. The second >question is, if I lower my compression and run more boost will this >actually afford me more horse power or is it just easier on the motor. >THANX everyone. > > > > > bgoodwin@iquest.net FZR1000 turbo EFI (aka The Money Pit)