Sign in to follow this  
Followers 0
eduardo426

Anyone with dyno numbers??

20 posts in this topic

Can anyone tell me what are the numbers for a good Wr?

No matter what kind of mods...some dynos can calculate the power available at the clutch as well as the rear wheel. I believe four strokes loose a lot of hp from the engine to the wheels. I`m going to dyno my Wr and would like to know what numbers are you guys getting with your mods or even stock. Some products sites have their own dynos but i believe they dyno their bikes with a road tire wich can make a bit of difference in the results.

Thanks a lot. :)

Share this post


Link to post
Share on other sites

A month ago I dynoed my '03 WR450 Supermoto with altered jetting, pump gas and the Yamaha GYT-R Ti exhaust can at CAD Cycles (Dynojet #?) in Gaithersburg, MD. and posted 48hp.

I've since put in a YZ450 Exhaust cam, switched to Jardine full exhaust and will run VP Ultimate 4 on the next run, probably in a week or so. I'm expecting 50-52hp with the new changes and go-go fuel.

Share this post


Link to post
Share on other sites

Those 48hp are shown at the wheels right? If so, did you had access to the clutch or crank numbers?

I was told that four strokes loose a lot of power from the engine to the wheel. .. :)

Share this post


Link to post
Share on other sites

My Canadian 426 made 42HP stock and 45HP (at the wheel ) with jetting, no lid and a Doma pipe. The real benefit of the pipe was through the mid-range - its up about 5HP from stock from 6500 to 8000 RPM. YZ timing is good for about another 2-3 HP on top judging by the seat of my pants.

Share this post


Link to post
Share on other sites

Why would a 4-stroke "lose" more power through the drivetrain than any other type of motor? It would seem to

me that the power lost via the drivetrain is a function of its design and not really whether or not the motor is a 4-stroke or 2-stroke.

In other words if you took a 2-stroke motor and a 4-stroke motor and mounted them to the exact same drivetrain (clutch, tranmission, final drive) then the HP lost over the drivetrain would be the same. :)

Any experts care to comment?

Share this post


Link to post
Share on other sites

48 was at the rear wheel.

Crank and Countershaft numbers will always be higher.

The crank turning all the gears in the transmission, through all that extra oil as well as the bearings and such before you get to the countershaft is just extra power-robbing drag.

Same thing from countershaft-to-rear wheel, chains are extra drag.

Same

Share this post


Link to post
Share on other sites

Had the 2nd dyno run today with the following changes:

Jardine full exhaust , Yz Exhaust cam, VP Ult4 fuel=52.5hp

My airbox lid on the left is vented with 5 3/4" holes, we completely removed the airbox cover and gained another 1hp which puts it at 53.5hp up from 47.8.

One goof I made that could've cost me a hp or two was run 15/46 gearing the 2nd run, I had 15/52 on the first run. The dyno operator said that taller gearing would produce a lower HP number since the bike is trying to spin the drum faster than with shorter gearing. Ooops.

Share this post


Link to post
Share on other sites

One goof I made that could've cost me a hp or two was run 15/46 gearing the 2nd run, I had 15/52 on the first run. The dyno operator said that taller gearing would produce a lower HP number since the bike is trying to spin the drum faster than with shorter gearing. Ooops.

This is strange! Isn't the dyno supposed to take also the speed/time/rpm in consideration, so that gearing do not change the results.

Share this post


Link to post
Share on other sites

So you are saying it takes the same energy to spin that drum at 94mph as it does 106?

Or, for example, if you did a 3rd gear roll on with 15/46 vs 15/52 wouldn't it be easier for the bike to turn the shorter gearing?

Obviously changing the gearing doesn't give the bike more power. Where I goofed was not checking what gearing I used the first time so I could eliminate all variables. If the resistance on the drum increases as speed increases I would think it could affect the numbers.

Any dyno operators out there that can attest to whether altering gearing will change output numbers?

Share this post


Link to post
Share on other sites

Had the 2nd dyno run today with the following changes:

Jardine full exhaust , Yz Exhaust cam, VP Ult4 fuel=52.5hp

My airbox lid on the left is vented with 5 3/4" holes, we completely removed the airbox cover and gained another 1hp which puts it at 53.5hp up from 47.8.

One goof I made that could've cost me a hp or two was run 15/46 gearing the 2nd run, I had 15/52 on the first run. The dyno operator said that taller gearing would produce a lower HP number since the bike is trying to spin the drum faster than with shorter gearing. Ooops.

did you take off the whole lid or just the battery and modify the lid, im thinking about taking the lid off too and putting the battery behind the airbox above the fender if it will fit :)

Share this post


Link to post
Share on other sites

""Any dyno operators out there that can attest to whether altering gearing will change output numbers?""

What, my answer wasn't good enuf? Nevermind!

Share this post


Link to post
Share on other sites

Ok, let's try this approach...

A dyno measures the rate of drum acceleration over a given period of time, the more powerful the bike, the faster it will accelerate the drum. Do we agree on that?

If so, read on. If not, provide your explanation.

*A bike in 1st gear will accelerate the drum to the motors redline much faster than it will in 5th gear, yes?

* The drum would be spinning at significantly different speeds at max rpm in 1st vs 5th gear, right?

I would assume each dyno operator has a certain gear they use for their dyno runs to maintain consistency between measurements, yes?

Would you agree that a roll on, in let's say 3rd gear for arguments sake, with a six tooth difference on the rear sprocket would produce two diffent amounts of time to reach redline, the shorter gearing reaching redline first?

If a dyno measures the same thing, acceleration over time, why wouldn't altered gearing affect the end number? :)

I stated in my earlier post that I know you don't gain horsepower by changing gearing. You do alter the acceleration and terminal speed.

I admit I shouldn't have done the runs with different gearing so I would not have this variable but I did and I do.

To find out whether or not the bike makes an extra hp or not isn't my point. I'm looking for a mathematical or factual explanation as to why different gear ratios would not produce different results.

Now what do you have to say about that?

Share this post


Link to post
Share on other sites

Yamsocal450,

We removed the left side airbox cover which already had 5 3/4" holes in it. The snorkel on top has been removed also but that was done prior to any dyno testing.

FYI-the addition of the Jardine full exhaust , Ultimate 4 fuel, YZ exhaust cam and no left airbox cover made 15%+ more power from 8500rpm up with over 20% difference at 10,000rpm.

Probably not what you woods riders want but for the Supermoto crew... :)

Share this post


Link to post
Share on other sites

im like FFR,im not a mathematics guy!i do know that when you a do a "all gear" on the dyno the peak number is always the same in each gear.

the graph will be steeper or more shallow depending on the gearing,but i doesnt affect h.p.

most dyno guys use 4th gear on a inertia (dj) dyno.you now have 2 dyno operators telling you that gearing doesnt matter! :)

Share this post


Link to post
Share on other sites

Thank you for pointing out that an "all gear run" produces the same peak HP number. I did not know that.

The reason I was trying to get an explanation out of you guys is because I think the other TT readers deserve more than a "because I say so" answer from "a guy on the internet".

Coming from some of the roadracing boards, especially for the 250 Grand Prix machines, I see so much BS information from "web experts" it's scary.

I had questions and explained my thought process about how I came up with those questions. Burned at least let me know that in his experiences you get the same peak hp in all gears, that helps me.

Share this post


Link to post
Share on other sites

I have a couple of DT setup videos out and in each one I try to explain that I am a better wrench than I am a speaker(or typist). So I guess sometimes I come across as you say, but it is not intentional. I will try to be more explicit in my responses, as most of my responses are pretty short. TW

Share this post


Link to post
Share on other sites

I remember when I tested my wr. I god about 2hp difference between tests with engine warmed at 65C(39.5hp) and 85C(41.5hp). So make sure you warm your byke enough before testing.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0