Thursday, August 13, 2009

Diesel torque, horsepower and performance

2005 Volkswagen Jetta TDI: Track Testing | Long-Term Road Tests Blog on Edmunds' Inside Line: "By stingray454 on February 12, 2008 12:56 PM

Yeah, diesels are a bit weird with acceleration. They've got unbelievable amounts of torque right off of idle practically, so they really jump off the line, but they have hardly any high end horsepower (relative to the torque anyway).

My diesel Suburban has 430 lbs. of torque at 2,100 RPM, but only 195 hp. Off the line, this torque in combination with 4.10 gears makes this 6,000 lb. truck downright snappy. Just for fun, I raced a riced out Acura Integra at a redlight three times a few months ago. All three times, my Suburban killed him off the line and up until about 35 MPH, by which time my diesel was out of breath, and his VTEC was just waking up. It was hilarious to see a huge SUV taking a riced out sporty car off the line like that. It was also a clear demonstration of the two engine's vastly different power characteristics. They pretty much couldn't be any more opposite.

The diesel is funny at full throttle - it displays all of its power right away, and up to 2,700 RPM. After that, it just makes more noise and seems to go slower! Its one of the few engines where I think you're better off short shifting to keep the RPMs down to keep it in its powerband (unfortunately I can't as its an automatic). It seems the higher you rev it, the less power it makes."

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