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CRF 150 Dyno Horsepower !!!!

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O.K. Here's the skinny. Bone stock CRF150 Dynojet rear wheel horse power. 12.2 HP @ 8000 RPM. Max torque 8.8 @ 6500 RPM. We made two changes and more passes for verification. Removed baffle. NO increase in PEAK HP. However, There was over a full 1.0 ft/lb torque increase between 4000 and 6500 RPM, and a full 1.5 horsepower increase at these same RPM. AND, just for you chain swappers !! BAD NEWS. A 428 chain conversion added NO INCREASE IN POWER. REPEAT,NO INCREASE. The only difference was during the very first minutes of testing. The stock chain and sprockets were a little down on the first pass (.2 horsepower)After that the power and torque WERE THE SAME

as with the 428 non o-ring DID Gold chain and sprockets. There was a noticable difference in weight. I will NOT be swapping on MY bike (CRF230) I have over a 1000 miles on my original sprockets and RK x-ring chain. I have had to adjust my chain only ONCE since installing almost two years ago. During dyno testing, I had to adjust the 428 chain THREE times !! That chain stretched like a rubber band. No thanks........

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Thanks for the info!

The 428 chain is kind of like a lighter tire. It doesn't increase horsepower at all but decreases your rotating mass. Which does help acceleration. Not sure how you ran your test but there would be no difference in sustained peak horsepower.

:cry:

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O.K. Here's the skinny. Bone stock CRF150 Dynojet rear wheel horse power. 12.2 HP @ 8000 RPM. Max torque 8.8 @ 6500 RPM. We made two changes and more passes for verification. Removed baffle. NO increase in PEAK HP. However, There was over a full 1.0 ft/lb torque increase between 4000 and 6500 RPM, and a full 1.5 horsepower increase at these same RPM. AND, just for you chain swappers !! BAD NEWS. A 428 chain conversion added NO INCREASE IN POWER. REPEAT,NO INCREASE. The only difference was during the very first minutes of testing. The stock chain and sprockets were a little down on the first pass (.2 horsepower)After that the power and torque WERE THE SAME

as with the 428 non o-ring DID Gold chain and sprockets. There was a noticable difference in weight. I will NOT be swapping on MY bike (CRF230) I have over a 1000 miles on my original sprockets and RK x-ring chain. I have had to adjust my chain only ONCE since installing almost two years ago. During dyno testing, I had to adjust the 428 chain THREE times !! That chain stretched like a rubber band. No thanks........

Cool :cry:

What about with the power up kit. Any HP gains off of that?

Maybe since the baffle was pulled, it leaned the bike more so it got the same hp :cry:

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Removed baffle.

coeshow- Are you meaning you removed the exhaust baffle or the air intake baffle (snorkel) ?

I'm looking forward to your continued findings!

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Toast is right, it increases acceleration. What you need to look for is the time its to achieve max hp with the 428 and with the 520. It's like strapping a big weight on your back and trying to do a 40 yard dash. Your strength or power in your legs doesn't change, but they move a heck of lot quicker without the weight.

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Toast is right, it increases acceleration. What you need to look for is the time its to achieve max hp with the 428 and with the 520. It's like strapping a big weight on your back and trying to do a 40 yard dash. Your strength or power in your legs doesn't change, but they move a heck of lot quicker without the weight.

Good point there :cry:

Drag times would be the only way to really check it, and you would have to do it 5 times each to get it accurate and such...

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HP is a calculation based on time rpm and torque(if I remember correctly)...so more HP would be shown if it accelerated quicker.

here is a quote from a popular site:

"Basically, an inertia-type chassis dyno consists of two great big heavy drums hooked up to a computer. An inertia dyno uses the power of the engine to accelerate the drums to speed.  The computer measures the time it takes to get up to speed, and the horsepower is determined from these numbers"

You would see a difference... if it were there!

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Horsepwer is rpm x torque, not rpm (time) x torque. So acceleration is not a factor for HP.

See Here

You might be thinking of: Power = force x distance/Time, with this formula less time = more power

There is also this formula:hp = force x distance/time (in minutes) x 33,000 f lbs/min, but dynos don't use this one.

Here's another good site.

The last site stated something about they should be close to equal at 5252 rpm. Otherwise be very skeptical. :cry: This is getting complicated :cry:

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You are right on the formula...I was not stating an exact formula...BUT what I was saying was that the Dyno calculates HP from the time it takes to spin a drum of known weight and at how many RPM's that drum spins... then it calculates HP...So if it accelerates quicker...than it will show more HP on a dyno...I rebuilt a race motor...only change was a titanium rod combo...more HP on the dyno.

I am not claiming that I know everything about Dynos(even though they are very simple machines)...but I do have many hundred dyno sheets...and yes they all have crossing at 5250:-)

SuperFlow's website tells how the dyno's work...

are we corn fused yet :cry:

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here are a few easier to read articles...

http://www.roadandtrack.co.uk/dyno_work.html

http://www.bristoldyno.com/info/whatis.htm

"A dyno can measure horsepower and torque at the rear wheel. It does this by measuring the time taken to accelerate a large roller of a certain weight (which the bike’s rear wheel sits on) from one speed to another. If you know the weight and speed of the roller and the time taken to accelerate it, you can calculate the torque and the horsepower"

:cry:

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About the times to accelerate. The times were negligable. I agree with the notion that less mass should accelerate faster but not with these tests. I believe the dyno drum weighs @ 300 pounds. All data taken with 250rpm splits starting at 2250 -9750 RPM. Engine in third gear. Did not do an all gear test. Rev limiter kicks in right at 10,000 rpm, but was done making power well before this.(8000rpm peak) Removal of the baffle did lessen the times slightly, .08 sec. Did not install Full-power jetting, ran out of time. Next tests will be with 188cc big bore and full power jetting, and then swap to stock 230 carb w/ full power jetting. Will also install White Bros. Exhaust system in some of the tests. The chain test was inspiring as I have read and heard people claim a HUGE increase by making the change. I was surprised by the amount of chain stretch !! This chain is supposedly DID's finest.

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Removed exhaust baffle. I do not think this mod (if done alone) really affects the jetting, if at all.

Removing the air box inlet does make a difference in the jetting. This will be removed in all upcoming tests, with full-power jetting installed.

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When you do it, please get your ruler out and make columns all through the rpm range. Top Hp is one thing, but what it's doing through the rpm range is crucial. Plus, at what rpm is the top hp. Since, 12 hp at 10k rpm is one thing, but 12 hp at 10.5 or 11k is quite another. ALso, please look at acceleration time. If one scenario reaches top hp at lets say 5.5 sec, while another set-up reaches it at 5.4 or 5.3, that’s extremely important. That's like a 2 bike length at a start, the difference between a holeshot and midpack. We all appreciate your time on the dyno and would like to thank you in advance for your findings. Trying to convince people to use their dynos for the sake of better set-up is hard to do, especially when there's no money involved. Thanks again!!! :cry:

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"The times were negligable" but the computer uses them to calculate HP none the less...

It really doesn't matter... I guess that we just got off topic about Dyno workings... But... if it accelerates faster... it will show more HP... thats my statement and I am sticking to it... :cry:

Keep us posted... I am thinking on going bigger bore on my 150... so I am anticipating your results.

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I think your right about the computer using time in its calculation. But I've seen different acceleration times with the same hp figure, so go figure. I imagine what the computer calculation is pretty complex to say the least. :cry:

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one more thing and then I will quit...

sure there would be some different acceleration times with the same results...things are rounded...easy enough...and then you throw in the correction facter... the thing is... that the dyno's are just for reference(as you prolly know)... going up in number is good... not the number itself... and another thing is that we are talking about very small number of HP here... you don't see big changes like you do with larger displacement motors. I am not used to working with numbers like 10-15hp...I can make a jet change or sneeze on my ignition and get that many HP on my tweaked Buell :cry:

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The thing with working with small motors is little changes feel BIG. When got my XR120 from 10.5 to 12.1 with a header change and carb spacing, it felt like a new motor. Doubles seemed smaller, big whoops felt like small whoops, the gap between faster riders and me was less. :cry: But the thing to remember is even a 1/2 horse here a 1/2 horse there makes a big difference.

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I hear ya... another question for you guys that are running dirt bikes on the dyno... are you using knobby or street tires? :cry:

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In my post I listed at what rpm peak HP and torque arrived at.The software actually has a neat "drag race" function where you can actually pit different tests together like you mentioned.Many times a pass that has made more "peak" power gets smoked by a test with lower peak power because of the narrower power band. The horsepower on the stock 150 noses over right after the peak at 8000 rpm. We held it open 'till the rev limiter kicked in at 10,000rpm. at 10,000 it was still making 9.0 HP and 4.9 ft/lbs.

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Its got a street tire. We've had this Dynojet model 168 for almost 7 years and have the process down pat. We are used to trying to detect "small" improvements as we built a modified XR50 that made 12.7 rear wheel HP compared to 2.5 stock !!Yea, how'd you liked to get beat by an XR50 ?? Also built many 90+ hp banshees for sand Nazi's, and have tuned dozens of Crotch rockets and Lightening Sprints. Most of the cars for optimizing carb mods when switching to methanol fuel.

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