[quote=“ChrisK,post:60,topic:3633”]
Agreed wholeheartedly (with regards to trying to compare absolute dyno numbers; a dyno is an important tuning tool though). A little late to this particular party, but I definitely agree.
This was awesome
[quote] Not one person will say… oh go get your dyno sheet and meet me here tonight. We will pull them out and see who has the best car
[/quote]
I’m still laughing
While everyone can agree that dynos differ there is something in the back of my mind that I relate to and that is Patrick Hale’s simple equation to calculate an engine’s output based on weight and trap speed as well as the physics professors before his time. Here lies the reason why I question some (not all) of the dyno outputs I’ve seen on various forums. IMO, people need to forget about the ET when looking at the HP. It can be calculated, but getting out of the hole takes practice and that mutters the end result. Any seasoned racer can relate when someone with a stout vehicle botches the start, but screams down the rest of the track. With a given hp and weight the trap speed can be better calculated within a very small margin. Some people believe in statistics? Well these guys have mounds of data to dial in their simple equation. I relate to Patrick Hale because he brought this equation to the digital world and is an accomplished racer who has developed programs we used back in the day (very detailed) to calculate HP, ET’s, or MPH.
MPH = 234(HP/Weight)^1/3
I know this isn’t a dyno, but if anyone can agree on a given drive train loss then you can see where the inflated numbers do not match up with some of the quarter mile trap speeds. This doesn’t include amateurs that have 2 second shifts and bog their ass off the line, but when you see moderate drivers run a certain MPH a proven driver will only best it by a few more.
My post doesn’t mean I’m anti dyno. Hell I like dyno plots. It’s a good representation of where power is coming on or falling off in a given gear; a very good tuning tool IMO. But anyway, my .02
Possibly the best, and most rational post in the entire thread. Way to be.
I personally don’t care what some random RX-7 calculator says one way or another, but just a heads up that Saki, or whomever, is going to pounce on you for using ‘whp’ in that calculator for ‘hp’.
No its meant for RWHP
I’m not sure how that calculator is formulated, but the coefficient (using a standard equation) is different than what I’ve seen. Furthermore, if you look at their clause you can see they altered the formula for aerodynamics so this may be why it’s a little off the path. There is also something relating to that calculator. In the pop-up they indicate the referenced car @ 2150 lbs for that 2004 event, but his car was 2050 lbs according to his own website. Also, if you pulled the referenced car’s info for that event (2004) he trapped 127.xx mph. Plug in the advertised 2004 season weight of 2050 and the advertised 340 whp (which is not mentioned anywhere) and the calculator says he should trap 131.xx mph. Let’s use Ken’s other drag car (turbo RX-8). Car weighed 1937 with him in it. He pulled off 834 whp @ 35 psi packed up and went for the strip to pull of a personal best of 189.04 mph trap speed. If you use the RX-7 calculator he should have only trapped 174.x. Let’s use a 15% drive train loss. That puts the his 834 whp to an estimated 981 hp at the flywheel. Use the equation I mentioned above [mph=234(hp/weight)^1/3] and it results in a trap speed of 186.x mph.
There are several things that don’t add up as well as incorrect information used for the example car. There are also more variables when using a dedicated drag car as a reference hence why I wouldn’t use this calculator.