john3_16 said:It still is not an accurate comparison unless you do a pre modified baseline....
You just can't pull a dyno chart out of a hat to prove that another bike is "more powerful" unless you do them all on the same day and same dyno...
And still, different dyno's read differently so this is why it is important to do them all on the same dyno...
steve125 said:All im saying here is that dyno chart that Marcus provided shows that bikes true HP numbers for the state of tune it was in. Sorry you don't like the numbers, but the SAE software is there so the runs can be compared on different days and temps.
His chart is good and since there has been no other comparasion made on that dyno to the one he's shown I don't know what the beef really is with it?
Is the number too low in your mind?? if so don't worry it only applies to that dyno anyway.
pace said:That is the fact that John is alluding to, I believe. Any engine builder knows that comparison between different dyno charts are largely meaningless unless it's the same dyno on the same day.
-pace
steve125 said:What is the difference between 1 day and the next on the same dyno?? Temp and humidity that can influence the results right? The SAE correction factors that out, so runs can be compared on different days. I've done it many times when repeating runs on different days and my numbers have not changed when returning to a previous setting. Now with no correction??? My numbers are all over the place.
john3_16 said:Yeah it was a good read....He left Honda because they wouldn't sign him to the deal he wanted..
And, he sure didn't have any problem with his starts in 02' when he had the perfect season...Even against a whole laod of 4 strokes in 03' he got good starts.
pace said:I don't think anyone is disputing that a particular dyno will produce the same SAE result on Wednesday as on Monday of the same week. The 'same dyno, same day' comes from observations that dynos do get out of calibration, that tires do wear, that motors heatsoak under certain conditions, etc. And the main point of contention is that different dynos will produce different results, SAE or not. Furthermore, different engines react differently to differing ambient conditions. SAE is good for a 'ballpark' figure, but if you think it's universally infallible then you might want to read up on what happens when we SAE correct high-altitude output, particularly from turbocharged motors (just one example).
There are bunches of good articles on the web that talk about the problems with trying to compare charts from different dynos - the different methods in which horsepower is derived, the variables that SAE does not take into consideration.
You can find the same dyno chart vs. dyno chart bickering on every auto forum out there, and many of these arguments arise from ignorance in the fundamentals of how horsepower is 'measured'. Now it personally makes no difference to me whether the CR makes 0.5 HP more than the YZ, or vice-versa. Does your bike feel good at the track... are you pulling on other riders...? My riding partner pilots an '00 KX250, so he's my main target. He pulls me on the bottom, and then I walk him on top. Overall my bike is faster. That's really all I care about, not what my 'SAE' output measures at on dyno XYZ.
-pace
Rcannon said:What does SAE stand for exactly?
marcusgunby said:I forgot to say on bottom end from a cr engine, KP did the ex world enduro champion(Eddy edmondons) cr250 this year, he lowered the cylinder , used different pistons and lots of other tuning and still couldnt get the bottom end power better than a yz/rm it had about 44hp which was plenty but didnt have a nice straight line like you see on the husky cr, the honda engine is actually borrowed from a road bike in japan i believe-they did this to save in R+D as the 450 was on its way, you can see why its not the best mx engine-it was never designed to be.
pace said:The charts between different dynos are comparable if you're unconcerend about 5% (whatever) discrepancies. You really should inform yourself before making assertions that are simply not borne out in reality. As I said, google will yield you with a TON of information on why quoting/comparing different dyno charts should be accompanied with a caveat.
In the 'real world' there are dirtbike owners in the Netherlands, in midwest America, and in the Rocky Mountains, who operate under vastly different conditions. John's argument was that different dynamometers in different locations may produce different dyno results, so let's stay on topic if you want to debate that point. I already stated, very clearly, that we're not contending the same dyno producing the same result on two consecutive days.
The supposed 50-something horsepower 250 reminds me of these 40 horsepower 125s that pop up from time to time. ;)
pace said:but if I see such obviously misleading statements that dyno sheets are universally comparable then I'm gonna call it.
-pace
Rcannon said:As a basic consumer a person see's these things. The Dodge diesel advertisements come to mind. They will boast about 600LB/ft of TORQUE!!!!! But the horsepower measures at 180.