Originally Posted by spensley
Just because somebody does not have a dyno sheet does not mean that there car has/is not making any more power than it was before.
If somebody pays $xx and feels an increase in power, that may be all that matters to them. They may not be concerned about getting an extra 20hp, all they want is an increase - and they have it. I've made modifications to cars and bikes before, and not had a dyno - but I can still feel an increase in either hp and/or torque. I may have made dyno runs later, and all that has done has confirmed the increase in power/torque - the only difference now is that I have a value of x hp or x lbs/ft tq. Oh yeah, and I've spent $xx for a piece of paper putting a value on my improvements. The dyno is not the be all and end all. I'll agree it is a very worthwhile instrument.
You are correct that the dyno is not the end all be all. The drag strip is a great place to test the results of any changes/modifications.
What is useless is the "butt dyno". I have seen more than one person swear up and down that their car is not faster due to a change in the exhaust system or intake filters. The car is louder so it must be faster right? These people have then put their cars on the dyno and been shown a loss in HP.
A great example is the Sprint Booster. Now this product does not claim to make any additional power. It clearly states that the change is only to throttle response. Yet many people talk about how much faster the car feels. No HP or Torque has been added and the car will not be any faster through the quarter. It is supposed to be a great product but if they marketed it as actually producing additional HP and I purchased the product and did not net any gains I and most other people would be very unhappy.
Personally I don't care to trust my hard earned money to a product because "someone feels good" about the purchase. This of course only applies to "performance" modifications that claim increases in HP/TQ.