Re: The Colorado BS thread
Thanks for putting down the detailed info.
I knew about HP at the crank vs wheel but never thought to look up the XJ stock numbers because I simply used a mental comparison to previously owned vehicles and thought 190 sounded reasonable enough for a DD+weekend warrior. (Personal experience said never buy anything rated less than 160 for all-around, daily driving.)
Did find this:
http://www.rockcrawler.com/techreports/dynomax_xj/page2.asp
They dyno'd a stock 4.H0 got 151 and change...
Depending on the variables... 151 sounds very low indeed.
With 190 at the crank, the power train immediately starts stealing power away as it delivers it. A manual transmission equipped vehicle should be ran on the dyno in which ever gear gives a 1:1 ratio. For our Heeps, that is 4th gear in the manuals. It becomes more complicated with an automatic as the transmission will want to downshift when the throttle is cracked open. Getting the thing to stay in 3rd gear is fun.
OK, no. Fun, it is not. So far, the only method I have found is to disconnect the TCM and then reset the MIL codes after the run. I have looked at the PCM code but it is not straight forward in terms of disabling the shifts.
What I would expect to see in a manual transmission is closer to 175 ponies or, the "Rule" value of 8% loss. Yet another "Rule if Thumb " (those pesky things are just everywhere, aren't they?) says that a loss of 10% is to be expected with the automatic. According to that rule, then my Heep should have came in at 171 instead of 168. As far as I am concerned, the difference is in the noise level of the data.
At 151, that is a loss of 21%. Something wrong there...
As for a "minimum" HP rating for a DD, this is where it does get to be fun. The original VW Beetle made a resounding 24 ponies. Not much. But, it would run for nearly forever.
I find it interesting to look at the loss schedule. Every universal joint steals power away. More if they are old and the lubricant has either hardened or gone away... The differentials steal power, the transmission... Every bloody thing steals a bit as it goes by.
This is
precisely why motorcycles are so efficient. As it turns out, a chain drive is about as efficient as it can get. Belt drives are almost as efficient as a chain, but not quite due to the "stiction" of the belt to the sheeves. Shaft driven are the worst of the lot for all that they are the cleanest.
As for me, I have been looking for additional power for all of my adult life and, for that mater, most of all of my life as I grew up in a household ran by an Original Hot Rodder. We had supercharged cars stacked to the ceiling of the garage... My Dad was big on sleepers. So, although the car would neatly remove your head under acceleration, the bodies usually looked like they had been reclaimed from a wrecking yard.
As it turns out, that was true more than once...
OK, off the soap box. You know how it is, once an Engineer...