blykins wrote:David, no need to private message me with anything. I just thought it would be a good exercise to try another dyno. It's not very often that you pull parts off the shelf and make 1.5 hp/ci...
Most engine builders/dyno operators aren't out to jip the general public with bogus numbers, but I've seen where an innocently misplaced weather station could offer up quite a few free ponies. There are 3 dynos in my area. There can be up to 70 hp difference between them and they are all calibrated....
Would you mind offering up the correction factor and the weather station data from this dyno session?
Actually i think it would be a good idea to PM you. There is some interesting Ford stuff on your site and I am doing a Ford book. I think we should talk.
Yes having a sensor in the wrong place can make for some optimistic #s.
A few years ago I was asked by Aston Martins historic race division to help break the 400 hp barrier with the 3 litre engine that was introduced back in the fifties and powers such cars as the Bond 007 car. The dyno curve I was shown when I got there indicated we only had to bridge the gap form 386 hp to 400. A step of a mere 14 hp. However on looking at the printout I noticed that the dyno testing was done in january and that the recorded ambient air temperature was in the low 80f range!!!!! Turns out the temperature was being taken from a point directly over the exhaust pipes! A check with the weather records revealed the true ambient temp to be about freezing point so the numbers were optimistic to the tune of some 40 hp. That meant I was supposed to find 57 hp not 14. A new set of ports and chambers plus some wet flow refinements with the Weber carbs and the intake manifold plus six months work resulted in a big torque increase plus 411 hp peak output. All would have been good but now the block life was reduced to an hour or so at the most.
Yes I will look through my paperwork to find what you need here. I may be a few weeks as I have quite a bit of preparatory stuff to be done prior to possible surgery at the base of my skull due to an accident at Brands Hatch in 1989 (44 G and no Hans device!). The dyno tests posted were done just before I had a series of run-ins with the ER department of which one resulted in emergency heart surgery. This year I only made it to PRI by the skin of my teeth. My good friend James Harris, a fire fighter with medic experience had to be with me the entire time. As a result I got to go to the show but was operating at half speed. I had on my list to visit Chris Straub but just simply ran out of time (sorry to have missed this opportunity Chris).
Just thought of another point concerning the flow curves I posted on the AFR heads a page or so back. Usually AF heads have above average intake valve discharge coefficients in the range right off the seat to about 0.250 lift. With average CD #'s a cam advance of typically 4 degrees is most often about it. However with an intake flowing slightly better than average at low lift the amount of cam advance required for max output is usually less. Here we had a situation where the intake valve geometry favored high lift rather than low lift. When the cam was set in at the traditionally accepted 4 degrees of advance it produced, as I expected, way less output. Making full use of the Jesel belt drive unit I use for dyno testing the cam was advance until the optimum was found. This proved to be right about 6.5 degrees advance. Power adjusting the cam advance to what the engine wanted rather than the cam companies best guess resulted in some 14 hp and 12 lbs ft to the better.