07-10-2007, 03:08 PM
having done a lot of this already, i have been reluctant to put one of these together because they are really so much work to get any results that mean anything - it is so easy to screw up and get bad numbers (i see it all the time at those "quickie dyno days") - the price is so inviting that people jump in and expect to get real results, but what they get is almost always garbage, because they don't take the time to measure everything - failing to do that can throw the numbers off by as much as 20 hp in either direction on this car (heck, moving the intake temp sensor 8 inches tossed it off by 10) - all you get on those kinds of dyno days is "it did this on this day under these known and unknown conditions", but you don't get anything that is relevant
but after all the mods and such that have been done, it seems there are those who would like to know what the results have been - sure, i have already tested a lot of this stuff under very controlled conditions, shown dyno charts and such, as have other people with the same results, so there is no reason to test that again, but it seems to be a popular idea to test your own car to see where you are - that's cool - it would be fun
so that the tests would be valid, of course we would measure all the atmospheric conditions - if we want to know flywheel numbers, we would also measure drivetrain loss and not merely plug in a number - every car is different - even things like tire wear affects the drivetrain loss (less mass=less loss) - either way, we would also control the most important factors like engine temp, intake temp, gearbox temp, strap tension, tire pressure, etc - we should also check the compression of each engine to give a relative result (lower compression means lower power) - a leakdown would be better, but i think i will have to do that another day (ooh - another gathering and more beer?) - this would be the only way to give any results that would mean anything
anyway, it means probably close to an hour and a half per car for 3 good pulls - we could probably get 6-8 cars done in a day - this does not include the time to do a compression check, and warm up the gearbox - skipping any steps or going any faster and the results will be meaningless and pretty much nothing but a circle jerk (still usually a fun day, but worthless data)
i can scout around for a dyno that can be relied on to be accurate, well maintained, and recently calibrated (not just cheap or available), and i imagine it would probably be about $150 per car - i might be able to work out a better deal - i can find out
anybody interested?
but after all the mods and such that have been done, it seems there are those who would like to know what the results have been - sure, i have already tested a lot of this stuff under very controlled conditions, shown dyno charts and such, as have other people with the same results, so there is no reason to test that again, but it seems to be a popular idea to test your own car to see where you are - that's cool - it would be fun
so that the tests would be valid, of course we would measure all the atmospheric conditions - if we want to know flywheel numbers, we would also measure drivetrain loss and not merely plug in a number - every car is different - even things like tire wear affects the drivetrain loss (less mass=less loss) - either way, we would also control the most important factors like engine temp, intake temp, gearbox temp, strap tension, tire pressure, etc - we should also check the compression of each engine to give a relative result (lower compression means lower power) - a leakdown would be better, but i think i will have to do that another day (ooh - another gathering and more beer?) - this would be the only way to give any results that would mean anything
anyway, it means probably close to an hour and a half per car for 3 good pulls - we could probably get 6-8 cars done in a day - this does not include the time to do a compression check, and warm up the gearbox - skipping any steps or going any faster and the results will be meaningless and pretty much nothing but a circle jerk (still usually a fun day, but worthless data)
i can scout around for a dyno that can be relied on to be accurate, well maintained, and recently calibrated (not just cheap or available), and i imagine it would probably be about $150 per car - i might be able to work out a better deal - i can find out
anybody interested?
94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com
"It isn't nearly as expensive to do it right as it is to do it wrong."
