TDI is turbocharged so compression has to be lower. Max boost is 18psi I believe. Fuel efficiency is directly related to compression ratio other things being equal. Kirk
-----Original Message----- From: harmonseaver [mailto:[EMAIL PROTECTED] Sent: Saturday, September 28, 2002 12:53 PM To: biofuel@yahoogroups.com Subject: [biofuel] Re: What is the significance of compression ratio in cogeneration context? --- In [EMAIL PROTECTED], Christopher Witmer <[EMAIL PROTECTED]> wrote: > What is the significance of diesel engine compression ratio in a > cogeneration context? I have heard that with cogeneration, the higher > the compression ratio the better. Can anyone tell me why? Is it because > a higher compression ratio means more heat? And how high is "high" for > readily available engines? I think my source said something to the > effect that Cummins has some engines with relatively high compression > ratios, beyond 20:1. Also, how easy is it to increase an engine's > compression ratio? I seems to me that one could damage one's engine > trying, if one was careless. I don't think it makes any difference in "cogeneration", per se, the engines still run at the same operating temperature. Perhaps what you are thinking of is that engines running on biomass gasifiers need much higher compression, which is why diesels are used. Many diesels have 25:1 compression, although some newer ones like the VW TDI's have only about 18:1. You can quite easily raise compression ratio by having the cylinder head milled off a bit, although that needs to be done after careful computation of the deck height of the pistons in the cylinder and the actual volume of the compression chamber in the head. For some gasoline engines, high compression pistons are available, although those are probably only going to take it to 11:1 or 12:1. Even for ethanol you want at least 13:1. You can't raise it much more than that for a petrol engine, since the piston crowns and connecting rods aren't strong enough. Bearings also might be a problem. Better to use a diesel and convert it to spark if necessary. Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ --- Incoming mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.391 / Virus Database: 222 - Release Date: 9/19/2002 ------------------------ Yahoo! Groups Sponsor ---------------------~--> Home Selling? Try Us! http://us.click.yahoo.com/QrPZMC/iTmEAA/MVfIAA/FGYolB/TM ---------------------------------------------------------------------~-> Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
