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[Dr.D]

Please help me understand these dyno sheets.

What are the smoothings in the upper right corner?

Are they done in fifth of sixth gear and if so how do the numbers compare?

Since atmospheric conditions of temperature and humidity affect the numbers how can we compare sheets done under such varying conditions?

Can the tuners cook(skew)the numbers to show better than actual gains?

I have only been back to the motorcycle game for two years after being out for 20. I do not remember these kinds of in depth discussions back in the early eighties. Thanks for helping the not so young(51 years) but ignorant/

[Supershooter]

Please attach the dyno sheet.
Supershooter

[Dr.D]

I was not so much asking to have my sheet looked at as general questions about comparing them to each other. Guys come on with numbers and sheet but can they really be compared with out interpretation of the conditions? I heard mention of the smoothing, what is that? Are all done in the same gear and if not the dyno's are not comparable. Sorry if the questions were ambiguous.

[LC110]

This may help you. http://www.bishopsperformance.com/dynoinfo.htm

[Half_Crazy]

I see that you have something to read above for a better understanding.

A Dyno is just a measuring tool. It is best used to determine if changes made to the engine were beneficial and in what way. As in doing a 'before' set of runs to establish a baseline, and doing runs after changes are made to see what the differences are. The only way to get accurate before and after is on the same dyno with the same corrections and smoothing. The exhaust can be 'sniffed' by the machine to allow the operator to tune the engine to an optimal mixture of air and fuel.

Horsepower is a calculation from the torque. HP = (Tq x RPM) / 5252 (this is why the HP and TQ graphs cross at 5252 RPM).

Let's look at this one:



Smoothing is at max of 5. The graph is SAE (corrected for weather/elevation).

The torque line starts at 100 ft-lbs @ 2650 RPM, ramps up quickly to 120 ft-lbs @ 2950.... and it's still making over 120 ft-lbs @ 5252 RPM. Nice torque for a cruiser/bagger/dresser. The HP graph is a nice diagonal line... but you can see that the HP is probably still building at the 5500 RPM rev limit. This engine would benefit from extending the rev limiter out to 6000+. Theres probably another 4 or 5 HP up there if it would rev out.

Here's another:



SAE correction, smoothing at 4 so the lines are a bit more jagged. This motor kinda lays there until around 3200 RPM where the torque ramps up. Needs exhaust restriction to flatten out/fill-in that dip down low.

The dyno is only as good as the operator. Dyno tuning is an art, and what you need is an artist.   

[Spiderman]

And yet another dyno thread with no mention of ET (elapsed time) between twisting the throttle and the various full power points.

One more time for those who may have missed it the first 100 or so times I posted it 

A motor with lower numbers but a quicker ET will produce a much greater seat of the pants feel than the opposite. Most Big number dyno motors are not getting to peak TQ and HP til into the 5 and 6 second range. If you're up against a guy with say 10 less on each graph but he's doin it in 3-3.5 seconds you're screwed, hand him your pink slip, you lost.

B B

 

[Half_Crazy]

And yet another dyno thread with no mention of ET (elapsed time) between twisting the throttle and the various full power points.

Good catch.

The guys who are doing my motor shaved a crank down and lightened it by 14 pounds. The bike didn't make any more power at all... but... a dyno pull from idle to rev limit in 5th gear was 1.5 seconds quicker. I'll be surprised if that's not a 9 second street bike.

[bigjohn]

And yet another dyno thread with no mention of ET (elapsed time) between twisting the throttle and the various full power points.

One more time for those who may have missed it the first 100 or so times I posted it 

A motor with lower numbers but a quicker ET will produce a much greater seat of the pants feel than the opposite. Most Big number dyno motors are not getting to peak TQ and HP til into the 5 and 6 second range. If you're up against a guy with say 10 less on each graph but he's doin it in 3-3.5 seconds you're screwed, hand him your pink slip, you lost.
B B

Thats exactly right
 big numbers are nice but only if you have to play catch up, 99% of the time a rider that knows his machine and has that quicker launch wins. The bigger numbers means they have to launch so their back tire wont break loose or their front end stays down. In the mean time the other guy is in his power range, If you havent  caught him at 5000 rpm ...your not going to.
Thats where the dyno comes in, dialing in components to get that. I have seen many a bike with 100/100 smoke big numbers.

[ALRG8TOR]

Excellent information! Thank you for adding to MY understanding. 

[Half_Crazy]

Thats exactly right
 big numbers are nice but only if you have to play catch up, 99% of the time a rider that knows his machine and has that quicker launch wins. The bigger numbers means they have to launch so their back tire wont break loose or their front end stays down. In the mean time the other guy is in his power range, If you havent  caught him at 5000 rpm ...your not going to.
Thats where the dyno comes in, dialing in components to get that. I have seen many a bike with 100/100 smoke big numbers.

The rider has a whole lot to do with it. Cutting a good light, launching, shifting at the right RPM... All the HP in the world is useless if you can't get it down the track.



  

[Spiderman]

Good catch.

The guys who are doing my motor shaved a crank down and lightened it by 14 pounds. The bike didn't make any more power at all... but... a dyno pull from idle to rev limit in 5th gear was 1.5 seconds quicker. I'll be surprised if that's not a 9 second street bike.

Ayuh !

B B

[Dr.D]

Yeh now we're teachin Dr. somethin. These are the things I never knew. Sorry about missing it the other 100x but I was not here and I appreciate your tutoring a new guy. Don't let me stay ignorant, please.

Are all runs made in fifth gear?

Explain the CF:SAE lettering please.

Are Elapsed times posted on the sheets?

[Spiderman]

Yeh now we're teachin Dr. somethin. These are the things I never knew. Sorry about missing it the other 100x but I was not here and I appreciate your tutoring a new guy. Don't let me stay ignorant, please.

Are all runs made in fifth gear?

Explain the CF:SAE lettering please.

Are Elapsed times posted on the sheets?

No problemo amigo. No disrespect intended, just a pet peeve of mine. The DynoJet Dynomometer computer program produces an ET sheet but you won't be handed one unless you ask for it. Why ? Well usually the guy doing the dyno work is the one who sold you the package of parts and he's for sure hoping you don't know squat about the ET factor if he's pushing a big number combo that has a slow ET. ET is to a large degree controlled by cam duration. Big cams generally have at least 230 degrees of duration to run a redline near stock (5200 rpm) As a rule of thumb, every 10 degrees of duration pushes your peak hp number upward 500 rpms. Your toque number will always peak below 5200. FYI, 5200 rpm is the point at which the torque and horsepower curves intersect. At 5200 your torque curve will be descending while (depending on duration) your horsepower curve will be ascending. If the cam has to get to 6000 rpms or higher to reach max hp then it's obviously gonna take longer than one that reaches it's full  potential at say 5700 rpms. The cams everyone talks about on this site do not peak out at stock redline (generally speaking)  But you know you can run a twincam to 6200 without doing damage to it - - or at least it's been my experience that they hold together fairly well until you start running them above 6200. The lift and duration of your cam plus other factors are referred to as "cam profile" there are other things involved beyond lift and duration that have to do with the ramps and/or shoulders of the cam lobes. You hear folks talk about cams that are hard on your valve train. A cam with steep ramps/shoulders would be one such cam while one with a nice easy slope to the top and back would be the opposite. Some of the nasty cams folks around here speak of are almost straight sided while others have nearly a 45 degree slope to the sides. When it comes to cams it'a complete science unto itself. The best selling cams are those that combine the qualities of a both types I've just described. This is just the basics of it and some of the members around here can really flesh this out to a much greater degree than what I've stated here. The thing I try to keep out there on the table in these discussions however is to be cognizant of what's involved with the numbers somebody is selling you on. If you're buying a cam that you've got to twist to 6500 rpm and wait 7 seconds for it to reach that 125hp you're being sold on, you will be very upset to find yourself getting dusted regularly by some of your riding bros with 110hp. Hey, bottom line ? I'm no fricken mechanical genious. I don't even own a shop. I'm just putting some common sense street knowledge out there for anyone that cares to check out what I'm sayin.

B B

   PS - - - SAE = Society of Automotive  Engineers. I always though CF meant diesel oil  

[Dr.D]

Thanks BB. The dealer recommended the 259e cam and the high compression pistons and I am pleased. If I can figure out how to post the sheet I will do it. It looks a lot like the first one above in this thread, I like it.

Are all the dynos run in fifth gear?

Looks like it is impossible to compare dyno sheets and come to absolute conclusions about which motors produce the best and most usable power.

[Spiderman]

Thanks BB. The dealer recommended the 259e cam and the high compression pistons and I am pleased. If I can figure out how to post the sheet I will do it. It looks a lot like the first one above in this thread, I like it.

Are all the dynos run in fifth gear?

Looks like it is impossible to compare dyno sheets and come to absolute conclusions about which motors produce the best and most usable power.

You can do dyno runs in any gear you choose, but obviously you can't run your motor up to 6200 rpms in 1st gear and hope it doesn't do some damage. So the common answer to that question would be YES, the dyno sheets you will be given would most likely be a 5th gear run. There's exceptions to every rule - - like what ? Well I doubt seriously a big motor bike would hit peak RPM's in 5th gear in an 8th mile drag race so that motor could well be tuned to peak in 3rd or 4th.

Yes, you are 100% spot on in my opinion. It is impossible to compare dyno sheets and come to ABSOLUTE conclusions which is why I get sort of wound up or amused depending on my mood at folks who live and die for their fricken dyno sheets. You can tell a lot about engine performance from a dyno and you can make adjustments to performance based on the information a dynomomter provides you. You can tune an engine to whatever your specific needs are and also test cams and other parts via the information provided but you don't know who's gonna win the race til the rubber hits the road. To say otherwise is foolish.

B B