First Ever Dyno Run

Posted: Thu Jul 09, 2009 7:54 am

So today I did my first ever dyno run. I’m not sure why but I learned a bit and had a blast watching the process. The Machine was a SuperFlow.

http://www.youtube.com/watch?v=wmZPL9_lZUM

Okay, so I’m pretty confused on SAE RWHP vs Dynojet HP vs Crank HP (mfr claimed).

Since there’s been a huge time lapse since rating standards for our old F’s and the varying formulas for Dynojet and crank, and differences between formulas used by various dyno computers; it seems the only useful information is comparative data between bikes tested on the same dyno machine.

The tech who ran the test on my bike has a heavily modded monster 900 and it laid down a maximum 65 SAE RWHP on their machine. The manufacturer claimed stock HP on those was 73 at the crank bone stock. Do we use the 20% loss assumption to conclude that he has only achieved an 8.25 increase in crank HP to 81.25?

If not, what does his 65 SAE translate to for crank HP?

My 28 year-old CB900F put down 77 SAE RWHP today on their machine (or 85 Dynojet HP according to their computer). SAE Torque came in at a paltry 49.1. I think stock HP claimed by HMC at the crank was 91 HP. SO does this mean that stock RWHP was 72.8?

Either way I had a great time watching the process and learned a lot about my fuel mixture. And their dyno room was one very cool place.

Has anyone here used a G-Tech Pro to measure HP on their bike?

Posted: Thu Jul 09, 2009 12:11 pm

try the airbox and a paper filter element instead of the pods.

CB1100F Joined: Jun 18, 2006 Posts: 2527 Location: UK

Agree with firemun59, try the Standard Airbox and Paper Filter,may be better without that large looking Probe down the end of Silencer.

My thought on Dyno HP is if the Bike pulls cleanly on the road without any hesitation or flat spot's and pulls to high RPM in 5th the Bike is OK.

Keith

Posted: Thu Jul 09, 2009 3:59 pm

firemun59 wrote:

try the airbox and a paper filter element instead of the pods.

That's funny. I wouldn't dream of it. I'm very happy with the bike. It pantsed a lot of the new bikes they had on file and a Honda 750 came in around 43 SAEhp on this machine. And since the modded Monster put out 65, I think the low numbers could simply be a reflection of true honest output. These are NOT Dynojet numbers.

I still have one CB900F with a stock choke box. Maybe I'll put it on there in a couple weeks if I can find someone to follow me there on it.

I also agree with krgood0 that the tech should have done a pull or two WITHOUT the fuel probe. The regular tech wasn't working and I seriously think he just forgot. It doesn't matter since I'll be back in a couple weeks after a couple final adjustments based on the fuel curves we got.

Remember, this bike has only intake and exhaust. No other engine mods.

Posted: Thu Jul 09, 2009 4:41 pm

JimAgain wrote:

firemun59 wrote:

try the airbox and a paper filter element instead of the pods.

That's funny. I wouldn't dream of it. I'm very happy with the bike. It pantsed a lot of the new bikes they had on file and a Honda 750 came in around 43 SAEhp on this machine. And since the modded Monster put out 65, I think the low numbers could simply be a reflection of true honest output. These are NOT Dynojet numbers.

I still have one CB900F with a stock choke box. Maybe I'll put it on there in a couple weeks if I can find someone to follow me there on it.

I also agree with krgood0 that the tech should have done a pull or two WITHOUT the fuel probe. The regular tech wasn't working and I seriously think he just forgot. It doesn't matter since I'll be back in a couple weeks after a couple final adjustments based on the fuel curves we got.

Remember, this bike has only intake and exhaust. No other engine mods.

You are running CV carbs - they respond to the consistent vacuum signal in the airbox across all the carbs - pods hurt performance unless you are using round slide or flatslide carbs like keihin Crs or FCRs - dont believe me?......ask around.....better yet retry the dyno with the airbox on.....you will be shocked.

Posted: Thu Jul 09, 2009 5:32 pm

Cool video. Can you post a printout of the graph?

Puke

airbox

Posted: Thu Jul 09, 2009 6:17 pm

blitzkraig wrote:

Cool video. Can you post a printout of the graph?

Puke

airbox

CVs and pods =

Posted: Thu Jul 09, 2009 6:32 pm

Now that's a dyno.

http://www.superflow.com/Dynamometers/Chassis/cycle_dyn.html

http://www.superflow.com/Dynamometers/Chassis/cycle_dyn_power_absorbers.html

http://www.superflow.com/Dynamometers/Chassis/cycle_dyn_options.html

Posted: Thu Jul 09, 2009 6:46 pm

Neat isn't it. Not so neat is the low HP number compared to what you "think" it will be.

As I said before when they first came up with these inertia type dyno,they put in the calculation into the computer and got "no power".

So they quickly realized the diffeerence between "real" power and selling the dyno to charge people for the dyno run. So they "fudged" the computer to make it read a higher number.

I had a dead stock 900 used for dead stock record in old IDBA. Best run was 12.37@108. The www.amadragbike.com/horsepower.asp estimater says around 70 HP. This was through the stock mufflers as well as stock airbox.

These estimater programs must be close and a computer is involved in either case.

When I did the dyno run on the dragbike it was smoking and spinning the slick on the knurled drum. People behind were being pelted with bits of rubber. When you are making real power a bunch of things happen. the Dyno guy said it was the wildest ride he had had with it trying to jump off the dyno. This was the '92 Brute Horsepower Shootout at Daytona,well before the rise in mega power machines of today.

Posted: Thu Jul 09, 2009 9:57 pm

genesound wrote:

Now that's a dyno.

http://www.superflow.com/Dynamometers/Chassis/cycle_dyn.html

http://www.superflow.com/Dynamometers/Chassis/cycle_dyn_power_absorbers.html

http://www.superflow.com/Dynamometers/Chassis/cycle_dyn_options.html

Yep, that's the one! Seattle Ducati has a great setup.

Posted: Thu Jul 09, 2009 11:01 pm

firemun59 wrote:

You are running CV carbs - they respond to the consistent vacuum signal in the airbox across all the carbs - pods hurt performance unless you are using round slide or flatslide carbs like keihin Crs or FCRs - dont believe me?......ask around.....better yet retry the dyno with the airbox on.....you will be shocked.

Hey, thanks for the comments. Actually I think I saw you selling stock CB900F carbs on EBAY this week. Am I right?

I love a spirited discussion as much as the next guy, BUT, I've heard enough debate on CV's to last a lifetime. They put them on SO MANY BIKES though. I wonder why?

Yes it's true that CV's (no matter who makes them) respond to vacuum. I clearly stated in another thread that if you go pods with good exhaust on stock unmodded CV's you will create a two-wheeled Japanese paperweight. You'll be lucky if it even drives. Every tech who's driven this bike is absolutely thrilled and surprised.

You need to understand what motivates a CV slider. On that note, let's talk vacuum. The sliders in a stock CB900F are designed to open only when certain vacuum conditions are met. So, naturally, the stock slider was CAREFULLY engineered to respond to conditions created by the stock airbox combined with the stock exhaust. If you change either of those, you must ensure the slider will still rise when the demand conditions are right. This is an advantage of a vacuum slide is that it is able to respond to more than simple throttle position. That is why they exist; when they're working, they provide good throttle response combined with excellent 'A to B' drivability.

Anyway, if you open up the intake, it reduces the pull experienced by the carb which is sitting between the intake port (vacuum source) and the atmosphere. An unmodded CV slide will just lay there with pods. You have to fix that. If you know you're never going back to the choke box, then you're safe to reduce the vacuum needed to lift that slider.

New CR's are probably great once dialed in, but they sell for about $1,200.00. More than I paid for the entire bike. With CR's, when you open throttle, you always get everything, NO MATTER WHAT the conditions are. High rev, low rev, hot, cold. They are all about throttle position.

Less airflow is not good for performance so I will never put the choke box back on the bike unless the environmental police force me to at gunpoint.

Yes the dyno numbers looked low but fortunately, they were even lower for most everything they had on file. What can I say? I guess it's not a generous machine. Laughing

Even with that giant probe tucked in my Vance Hines, my bike made better numbers than a lot of the big bad toys they had on file. Anyone else want to show numbers from Seattle Ducati's dyno and I'd love to see them.

I know this bike pulls way better than it ever did stock and much better than my CB900F with a choke box and Vance Hines and as I said, I will try to arrange to have it dyno's there side by side when I take this one back.

Posted: Fri Jul 10, 2009 12:24 am

blitzkraig wrote:

Cool video. Can you post a printout of the graph?

Puke

airbox

No problem. He couldn't figure out how to e-mail them to me so instead of waiting for that I just took pics and uploaded them.

Here's the tech's Suped Ducati Monster 900
http://img7.imageshack.us/img7/6760/modifiedducatimonster90.jpg

Here's mine (1981 CB900F):
http://img34.imageshack.us/img34/5720/1981cb900flarge.jpg

Here's mine with multiple HP type curves. I just know someone will explain this one. Very Happy

http://img7.imageshack.us/img7/4929/1981cb900fsplitcurvelar.jpg

BTW, I love the airbox puke moticon. Laughing

Posted: Fri Jul 10, 2009 12:40 am

Jimagain wrote:

Less airflow is not good for performance so I will never put the choke box back on the bike unless the environmental police force me to at gunpoint.

Don't know what degree of sophistication our ancient airboxes were developed with, but an "airbox" is a sound performance concept.

Kevin Cameron wrote:

AIRBOXES The Cellar Dweller
new tuning tool? Kevin Cameron

For years, airboxes have been part of the production trash that serious racers routinely discard at once. Airboxes were, it was believed, like mufflers and low exhaust ports – things that might be desirable in a world of civilization and wives, but are definitely contrary to the spirit of good fun. Accordingly, we have either ripped out the aforesaid airboxes, or have gutted them of their fun-destroying (and airflow-killing) elements such as baffles, resonator tubes, and foam. Ahhh, there’s that soothing roar again…now I can hear the intake process all the way to the crankshaft.

But a mystery has arisen, and our hands hesitate as we prepare to gut yet another new airbox. Sometimes, these days, engines make less power after de-airboxing than they did before. What is going on? Is nothing sacred?

What has happened is that the airbox has now been added to the list of “resonant powerband aids” that formerly included only tuned intake and exhaust pipes. Intake noise, once just an EPA-listed source of environmental hazard, can be put to work cramming air into our engines.

Hold an empty bottle up in front of your mouth and hum up and down the scale into it. At certain voice frequencies, the bottle will act as a resonator, and the sound will become louder. At other frequencies, the bottle will be in “anti-resonance” with your note, and the sound will be softer.

The bottle acts as a resonator because it has (a) a spring, which is the volume compressibility of the air in the bottle and (b) a vibrating mass, which is the slug of air in the narrow neck of the bottle. Your humming provides a cyclical driving force, setting the air-slug to vibrating in and out in the neck of the bottle.

This is a different kind of resonance from that found in intake and exhaust pipes, where pressure waves travel and reflect in specially-shaped tubes.

Your engine’s airbox is a very large bottle, and its “ram-air” pipe or pipes act as the bottle’s neck. Your engine’s intake process, occurring hundreds of times a second, is a particularly strong form of humming into the bottle. To boost power, design the airbox volume and the diameter and length of the box’s air supply pipe(s) such that it resonates in step with your engine’s intake process at the desired rpm. At resonance, your engine will take air from the box only when it is above atmospheric pressure, and between intake events, the box will be below atmospheric pressure, refilling itself from its air supply pipe(s).

How can this effect be useful? Well, imagine that peak torque is OK, but the engine’s a little weak at closing the clutch. No problem; just set the box resonance to give a little boost right at the rpm where it’s needed. Or perhaps your exhaust pipes are a little sharp, leaving the engine an airless weakling right where a lot of people want to ride it? Fill in that hole with airbox power. Or maybe you just need to make a bigger number to fill a vacuum that’s formed between the admen and the dyno? Stack that box resonance right on top of peak torque.

This same situation existed in production motorcycle racing not so long ago. Where rules permitted, racers whipped airboxes off new models as if by reflex. This thing’s gotta make more power with K&N sock filters than with that big asthma box. But in the late 1980s, track testing and accurate dyno work began to show less power, not more, after airbox removal. Back on went the boxes, amid heavy shoulder-shrugging and sighing. A litter later, even pure racebikes began to appear with “ram airboxes”. This meant that the carbs were located inside a sealed box, fed with ram air by one or more forward-facing pipes. Attention immediately focused on the idea that ram action would “pack” air into the carbs. But the sliderule people noted that a forward-facing intake, operating at an unlikely 100% pressure recovery, is only worth about a 3% pressure gain at 150 miles per hour. Yet these “ram airboxes” were regularly showing much larger gains of 10 or even 15% more torque. Where was the extra power coming from?

Well, some of the gain on bikes came from keeping hot, lower-density radiator air out of the carbs – but the gains were too big for this explanation, too. But now the mystery is explained; the resonant airbox has come of age. With the airbox humming its big, monotonous tune, in the right range of rpm, the engine performs its intake process only during the positive-pressure part of each airbox oscillation. This is mild supercharging – and it’s essentially free.

There are minor problems with operating in a sealed box. The intake pipe or pipes to the box must be large enough to supply plenty of air without much pressure drop from internal friction. But the physical laws that govern this kind of oscillator must be respected, too. The whole device must fit on the machine. Just putting the carbs bellmouths into the box is usually not enough. Fuel is metered based upon the pressure difference between carb throat and the pressure above the fuel in the fuel bowls. Putting the carbs wholly inside the box makes sure that fuel breather lines are at box pressure. Just as in humming into a bottle, there are resonances and anti-resonances; if the airbox helps in one rpm range, it is sure to hurt in another. Fortunately for the snowmobiler, the clutch keeps the engine at near-constant rpm on full throttle, so a singe box resonance works very nicely.

To give maximal gains, a resonant airbox must be sealed up tight everywhere. Otherwise leakage will damp out and kill the resonance just as surely as a leaking valve will make it impossible to blow a note on a saxophone. Finally, strong airbox resonance still makes a lot of noise, and the EPA is still listening. For this, it is usual to put small sub-resonators into the intake pipe(s) feeding the box, so the sound bounces between airbox and sub-resonators, with a lot less reaching the great outdoors.

This big change in airbox design is one of both knowledge and intention. The boxes were originally just a place to put the air filter, and a way to suppress intake noise. The new boxes tackle both those problems, but also employ box resonance to help boost torque in some desired rpm range.

A resonant airbox is a type of Helmholtz resonator, and there is a formula for calculating its frequency from its dimensions. As you’d expect, the formula is not an exact predictor of reality, but it can give the user a good idea of what has to be changed, how much, to get what effect.

There is a direct way to the same information, too. Go to the electronics store and get a frequency generator, which is the modern equivalent of the singing teacher’s pitch pipe. Feed its output, suitably amplified, into a small loudspeaker. Place the speaker at the entrance to the intake pipe of the box to be tested (installed on the engine), and sweep the frequency up and down until you hit a strong resonance. Note the frequency from the dial. To lower the frequency, you can make the box bigger or the intake pipe longer or smaller in diameter. To raise it, do the opposite. This kind of testing, combined with careful dyno work, will soon reveal just what has to be done to get maximum effect where you want it. In this formula, the frequency of the oscillator, in cycles per second, is equal to 5280 times the square root of the following quantity; area of the intake pipe’s cross section, divided by (oscillator volume times intake pipe length). Obviously, all the numbers have to be in the same system of measurement – don’t, as I sometimes do, mix millimeters, inches, and feet to get a ridiculous answer that takes half an hour to correct.

Intake airflow through the carb and into the crankcase can also be treated with the Helmholtz formula; the crankcase volume itself is the spring, while the air in the carb, manifold, and inlet valve is the vibrating mass. From this treatment, you can easily discover that, with the usual sizes of carburetors and the crankcase volumes used with them, it is practically impossible to make the intake system short enough. This explains why, when an intake system is shortened, there is nearly always a gain. Those of us who like to fiddle with numbers when it’s inappropriate to fiddle with hardware (in business meetings, at family reunions, religious observances, etc.) will find hours of enjoyment in simulating new combinations with the Helmholtz formula and a pocket calculator.

Airboxes are no longer power-robbing annoyances, foisted upon us by the heavy hand of government or voluntary compliance. They are useful, torque-boosting tools in their own right. There is an interesting parallel between airbox development and jet engine experience. Back in 1960, when loud turbojets were coming into civil aircraft usage, the complaints from people on the ground were equally loud. In the resulting efforts to quiet those noisy machines, each time the engineers investigated and controlled a sound source, there was nearly always an accompanying gain in thrust or a drop in fuel consumption. As some are fond of saying, knowledge is power. Now about all that noise coming out the tailpipe.

http://www.thunderproducts.com/AirboxesDynotech.htm

Posted: Fri Jul 10, 2009 12:46 am

JimAgain,

yes I sold a set of 900F CVs this week - its part of a 900F part out - the F that I ride is an 11 - to be honest I have never used pods on a CBF Honda - but there are far more savvy mechanics than I that have convinced many of us not to do it - if you are having success - great!......and yes CRs are pricey......I am torn as far as which route to go regarding fuel delivery - fuel injection using used throttle bodies or FCRs - the tunability with fuelie sounds great - aalthogh I will be on a very steep learning curve....... Confused

Posted: Fri Jul 10, 2009 1:55 am

firemun59 wrote:

JimAgain,

yes I sold a set of 900F CVs this week - its part of a 900F part out - the F that I ride is an 11 - to be honest I have never used pods on a CBF Honda - but there are far more savvy mechanics than I that have convinced many of us not to do it - if you are having success - great!......and yes CRs are pricey......I am torn as far as which route to go regarding fuel delivery - fuel injection using used throttle bodies or FCRs - the tunability with fuelie sounds great - aalthogh I will be on a very steep learning curve....... Confused

Hey cool, you're the ones making that nice looking stainless pipe! Nice work!

Thanks for being honest about never giving CV's a chance. Careful what you read on the net. Many a tuner played with and raced these by figuring out how to get the sliders to rise under lower vacuum and they will still provide great commuter performance off the track. You can't really race them today unless you greatly limit the age class or just allow 900F's. Laughing

My biggest mistake on a forum like this was not doing a baseline dyno first, so now I have to leave the one bike with an airbox and go dyno it at the same shop I guess. But trust me, the bike feels great, pulls like crap and sounds fantastic compared to it's pre-pod state.

Anyway, you make a sweet looking set of pipes. (at least I think that's you) Sorry about what happened with the 'beta' shocks. I was not involved but read a bit of history. It's tough when you put your trust in and then must babysit factories so far away.

Economics matter with tuning these. If I wanted 150HP on this bike it would be cheaper to just strap an extra 200 pounds on my 954, loosen the triple tree and . . . you get the point. I REALLY love my CBF's because I grew up with them and few bikes sound as sweet as one of these with a good pipe. For now, I'm just getting what I can with what's readily available while trying to keep these old beauties of mine on the road.

Cheers!

Posted: Fri Jul 10, 2009 2:56 am

The intake is the thing to not screw with since it upsets the balance.

The header though is pure gain. It basically creates more airflow and the CV just adjusts to it.

The reverse is true as well. Meaning if the bike is weak,poor valve or ring seal,it does not "draw" as well,but still runs fine until it gets really bad.

Basically the CV was made so it would run very lean,ie improved EPA numbers,but also gives decent gas mileage and runs nice. Thus the reason almost all bikes used them.

In the modern era,even with fuel injection,they use the vacuum piston to act as the "delay" to get smooth power. Now common is two butterflys. The main is throttle and the one on the aircleaner side is controlled by the computer and a servo motor. It only gives the engine what it can take now under computer control.

Posted: Fri Jul 10, 2009 2:59 pm

Where did my post go??? It was right HERE last night, now it's gone. Question

Posted: Fri Jul 10, 2009 3:46 pm

My post is gone as well... But hopefully Glenn fixed the forum, it was working like crap last night.

Anyway... Haven't we been through this before?
http://www.cb1100f.net/modules.php?name=Forums&file=viewtopic&t=37333&start=0

Posted: Fri Jul 10, 2009 4:22 pm

CB900SS wrote:

My post is gone as well... But hopefully Glenn fixed the forum, it was working like crap last night.

Anyway... Haven't we been through this before?
http://www.cb1100f.net/modules.php?name=Forums&file=viewtopic&t=37333&start=0

Wow, thanks CB900SS for posting the link to that old thread. I’m getting higher numbers by running a bit richer than the setup “burned” was running in Sept 2007. My dynojet max of 84.6 looks a lot better now that I’ve seen another honest chart of an actual dyno run. No wonder the bike feels so good, it is!

From the old thread:
http://img.photobucket.com/albums/v699/burned-drz/CB900F.jpg

My run from Wed.
Dynojet numbers:
http://img7.imageshack.us/img7/4929/1981cb900fsplitcurvelar.jpg
SAE Superflow Numbers:
http://img34.imageshack.us/img34/5720/1981cb900flarge.jpg

It might be a tad too rich in the mid so I’ll lower my needles slightly and try a few runs without the giant probe in my VHR 14301. Laughing

Thanks again for bringing that old thread up!