Power Band

[FestYboy]

dropping 200 lbs on a 1900 lb car will make a notable differance (follow: 63hp into 1900lbs = 30.16lbs/hp, 63hp into 1700lbs = 26.98lbs/hp. that is a 10% loss of weight (give or take) and will net better accel and economy.) totally worth it as it's "free" were a cam runs about $150 and you're still draging that weight around with only 6 more hp to help it out (27.5lbs/hp). now on that thread, we'll go one better, weight loss AND mods... so, 1700lbs + 63hp + ~6hp for the cam, + 2hp for catback exhaust, + 4hp for header and +2 for modded intake = 1700lbs + ~77hp: that's 22lbs/hp (much better)

[FB71]

I may be wrong, but the dyno actually measures Torque (force) & RPM and calculates HP, right?

correct. HP is work over time.

The mathematical correlation between them doesn't change. In theory, you should be able to calculate HP at any given RPM if you know the Torque. What's the difference between the dyno taking readings at the crank vs. at the wheels (other than being less)? Obviously, you have a torque converter and tires than can slip and absorb varying amounts of torque, but that's the whole point of a Chassis Dyno. It measures the bottom line force that the wheels put to the pavement and takes all other factors out of the equation? I guess I can't visualize how a chassis dyno would have any effect on the 5250 point.....I would say that the only factor would be the accuracy of the dyno and procedure.

If the gearing is not accounted for by the dyno operator, the crossing will move on the readout. Most operators properly account for final drive, and direct drive thru the trans is assumed. However, transaxles never have a 1:1 gear, to eliminate hunting gearsets. Its always a tad higher or lower (0.97:1, 1.04:1, etc.). This will move the crossing on the graph. If the crossing is nowhere near 5252rpm, then the pull was done in a gear other than 'direct'. A common trick for a local Aisan/Euro tuner is to do dyno pulls in 3rd to falsly inflate their tq claims.

[blkfordsedan]

Thanks Jim. That helps explains a couple things. Now I just have to figure out the math behind it so I can quit thinking about it.....and check to make sure the oven's turned off......3 times.......while only trying to rotate the knobs counter-clockwise...........and counting the steps from the computer to the stove.................

[FB71]

OCD or just joking? I take some wonderful meds for mine!