Help me understand these dynos.

[Shiv]

So I recently (bout 3 minutes ago) discovered the dynos on this site while looking for info on a DR 250.

So, having only seen two dynos before (one on a, supposedly, 700 HP busa) I didn't much understand them.

So I took two and circled what I think everyone is warning people about when they want to get a 600 for a first bike.

I took a Bandit and a GSXR, both the 600 model. The Bandit is HP vs RPM and the GSXR is HP vs MPH.








Now what does comparing HP and MPH on the GSXR tell me?

On the Bandit I'm pretty sure I understand that the 'powerband' (circled area) means that you're increasing your horse power (and speed) extremely quickly during that RPM range which is why it's not that great of a beginners bike since you're accelerating quickly.

Not sure what to make of the GSXR's HP vs MPH. I guess that during a certain MPH your HP goes up. But that doesn't tell me much about the powerband since it doesn't include the RPM. You could be doing 50 MPH in 3rd gear or 4th gear and have different RPMs going.

I expected the dyno to say something like @ 7000 RPM or something along those lines but it doesn't. Is it supposed to?

[Pongo]

Now what does comparing HP and MPH on the GSXR tell me?

Not much.

[9000white]

very little.

[Shiv]

Has to have some meaning. Why else would people pay money to get their bikes dynoed.

[axidjw]

mph means nothing..
Dynoing is basically for braggin rights..i have a "..." that puts out x amount of horsepower..oh well i have the same "..." with 15 hp more
The 2nd thing dynos are good for is for tuning..shops can use a dyno to super tune chips in your car and for bolt ons like turbo management systems and fuel management systems..nos output..they start with a baseline run and then add in the fuel management system to see where it falls flat through the power curve or where the turbo has lag through the powercurve..it can be a very sophistacated usefull too or it can be just to get that piece of paper..haha

-john-

[earwig]

In my opinion... horsepower isn't what people should be super concerned with, you should look at the torque a bike has that is what will knock you on your butt super fast...

[Shiv]

Really? I never was able to wrap my mind around the relationship between torque and HP.

I know HP is the power of the bike, and torque, from what I understand, is how much force it exerts on the ground. But that's about it. I don't know WHY it'd knock you on your arse.

I guess it pushes off so hard that the front goes up and you go down?

[Skier]

mph means nothing..
Dynoing is basically for braggin rights..i have a "..." that puts out x amount of horsepower..oh well i have the same "..." with 15 hp more
The 2nd thing dynos are good for is for tuning..shops can use a dyno to super tune chips in your car and for bolt ons like turbo management systems and fuel management systems..nos output..they start with a baseline run and then add in the fuel management system to see where it falls flat through the power curve or where the turbo has lag through the powercurve..it can be a very sophistacated usefull too or it can be just to get that piece of paper..haha

-john-

I quite disagree with you. Dynos are essential in tuning any internal combustion engine. Controlled situations allow replicable conditions for better tuning. More power, safer, is always a winning situation in my book.

How do you think car and bike manufacturers tune their vehicles before they hit the showroom? Pure math only gets you so far, a dyno does a far superior job showing what's actually happening than a book full of equations.

[flynrider]

I used to run a motorcycle dyno at a friend's shop on weekends.

The reason that everyone is telling you the HP vs. MPH is meaningless is because the measurement has no connection to real world riding. In the real world, as you increase speed above 35 mph, air resistance becomes the primary force that has to be overcome by HP. Sitting still on a dyno will tell you nothing about air resistance and the HP required to overcome it. The HP vs. MPH chart will be right on the money if you ever go riding on the moon, though.

The HP vs. RPM chart can be useful, particularly if you're into racing. It gives you the rpm range at which you're particular engine will be making its maximum horsepower. In a race, you'll want to stick as close to that rpm as possible.

Edit : Dyno charts can also be useful to the average rider. I used one last year to show a friend that he really hadn't outgrown the power of his EX250. He just hadn't found out were the power was yet. Not an uncommon problem with a lot of folks that have decided a particular bike doesn't have enough power.

[ZooTech]

I'll be scheduling an appointment with a dyno in the near future. Once I get my intake and TFI installed, they can use their EGA to set all the mixture pots correctly to ensure that I'm running a proper mix and getting all the ponies I paid for.