Quote:
Originally Posted by Terry England
The diesels engine needs about 22 to 1 compression ratio to detonate the fuel. To do that you need a long stroke engine or you will put an awfull lot of load on the top end. My "rule of thumb" research is that 3400 RPM Volvos, Yanmars and Vws last 6 to 10 years. 2400 RPM 3208 Cats last 15 to 25 years and 1800 rpm in-line Detroits last 20 - 30 years. If you spool 'em up you'll burn 'em down.
The old 170 Yanmar put out the same torque as a 454 at 3200 rpm's. the problem is the Yanmar was "against the wood" and the 454 was a half throttle. I run them all easy - an engine only has so many "frams" in - no use in using them all up today. Equipment is expensive to replace and It's tough to figure out how to depreciate "toys" with the IRS!!!
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The Tier 3 VW's run a 16.4-1 compression ratio. As for the 170 Yanmars, I see a hell of a lot of them still running after many years. There was a gringo owner in Mazatlan who ran a couple of old 29 Robalo express boots as charter boats with pairs of those very engines. 20 plus miles out to the fishing grounds every day and 20 miles back for years. Those are 3.5 liter blocks that weighed 900 pounds dry. I was a history major, but I think that works out for less than 50 hp per liter. As for torque, don't turbodiesels tend to produce much of their torque well off of WOT? The current 550 hp Cumins QSB 6.7 has a top end of 3200 rpm but produces max torque starting at 2000 rpm. Mercury doesn't have a torque curve for the diesels or the gassers on it's performance reports. I did look up the similar 150 hp BMW based By series Yanmar 2 liter TDI. It has a top end of 4000 rpm but reaches peak torque at 2500 and holds it up to around 3500 which is about 100 rpm's shy of the max continuous rating for that engine. That would lead me to believe that if the old 4LH series 3.5 liter Yanmar actually put out the same torque at 3200 as the 454, it probably put out MORE at 2500.