Not my numbers, John. Holley states that an ordinary low-performance engine has a VE of about 80% at 'maximum torque' and a high-performance engine at about 85%. http://www.holley.com/HiOctn/TechServ/TechInfo/TI-224.html
Other sites say between 80% and 90% is typical for a normally aspirated engine. http://www.auto-ware.com/combust_bytes/eng_sci.htm http://www.epi-eng.com/ET-VolEff.htm http://www.canadiandriver.com/articles/jk/020529.htm This guy went so far as to calculate his on a 99 Z/28. http://www.installuniversity.com/install_university/installu_articles/volume tric_efficiency/ve_computation_9.012000.htm - came out with just a shade over 76% My point is that you can calculate for 100% VE but, in reality, you'll probably never achieve it in a day-to-day car. So, why fool yourself into thinking you can run a larger carb at a higher RPM than you can really use? It's not a point of choosing a carb that'll only "get" you 75%, it's choosing a carb that'll make the most of the 75% you'll probably achieve. Even at 80% to 85% VE with the same basic engine, you're looking at 360cfm to 380cfm range. It's like selecting a camshaft, bigger sounds better (i.e., .580 lift at 320� duration) when a .490 lift and .295� duration will make your car drivable. I'd just say to give it some thought and don't run out and buy the biggest or most popular combo out there...it might not work for you. :*) Dale McIntosh I've stopped 1,542 spam messages. You can too! One month FREE spam protection at http://www.cloudmark.com/spamnetsig/ > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of John Nasta > Sent: Tuesday, February 24, 2004 10:01 PM > To: The Chevelle Mailing List > Subject: RE: [Chevelle-list] Malibu Carb question > > What you are supposed to do is *be realistic* about what max > RPM you will be running at, and find the CFM that will get > you 100% VE at that RPM. Using the formula to find a carb > that will get you 75% VE at your max RPM kind of defeats the > purpose of using the formula if you ask me. > > Now, it's true that there are factors other than the > carburetor that contribute to whether or not you are getting > 100% VE at max RPM, but that doesn't mean you should choose a > carburetor that will guarantee you not to get better than 75%. > > John Nasta > > -----Original Message----- > > But...you're lucky to get 75%-80% VE on any given street > engine. :*) A normal street 283 isn't going to see the high > side of 5500 and live very long either, to be honest. > So...in the real world > > 283 * 5500 / 3456 = 450. Multiply that times 75% and you get > 338. Of course, there are always exceptions and VE can vary > - but not much. :*) > > > >
