Gen ii busa - what does it really make?

[cwalker2]

This is a great comparison. I see many people post their shops print outs and they are often in STD. The STD factor is about 4% higher than the current SAE standard. STD corrects back to a cooler temperatute and higher barometric pressure. Therefore the print out is saying, "Under these nearly perfect conditions your bike made X hp." SAE is corrected to a hotter temp and is therefore lower by 1% right away based on that fact. The lower baro pressure makes up most of the next 3% difference.

The one thing I'd like to add is that the problem with the Dynojet dynos is that they are NOT accurate. Many say how they are the most accurate. They are often repeatable, but certainly not accurate. Back when Mark Dobeck first developed the DJ100 dyno, he was upset that his dyno didn't read 119hp for a stock 1985 Yamaha V-Max. It read in the 90's. He was missing some very big factors (two bevel drives, countless bearings and flex couplings, fluidic drag as well as rear wheel inertia) trying to obtain a reading similar to a water brake dyno run directly off the output shaft of the transmission . Thus the Dynojet's have inflated numbers in order to match the 119 the magazines measured on the Kerker and Webco dynos. They've changed the factors several times over the years, but never returned to zero inflation.

I've owned a DJ Model 100 since the old DOS software days. I tested back to back revision of software and it was surprising how a new revision would read higher or lower than the previous when run back to back within minutes of the previous run using the same correction factors. I worked closely with the folks at Dynostar when they were trying to figure out the methodology employed for their inflation factor. Adding 20 hp was incorrect as 5 hp minibikes would test at 25 hp. Adding an inflation % didn't work because 300 hp bikes would become 360 375 hp bikes. They seemed to have a factor that increased up to a certain % based on hp measured and then a decrease in % after a certain point in order to keep numbers from getting too big. Absolutely crazy.

Factory Pro, Land & Sea and Superflow read lower than DJ as they never tried to make their units read 119 hp for the '85 V-Max.

It's been posted many times before, but Dobeck's confession is here:

The Story Behind the Dynojet Chassis Dyno - The Truth Meter - Hot Rod Magazine

 

[POWERHOUSE]

This is a great comparison. I see many people post their shops print outs and they are often in STD. The STD factor is about 4% higher than the current SAE standard. STD corrects back to a cooler temperatute and higher barometric pressure. Therefore the print out is saying, "Under these nearly perfect conditions your bike made X hp." SAE is corrected to a hotter temp and is therefore lower by 1% right away based on that fact. The lower baro pressure makes up most of the next 3% difference.

The one thing I'd like to add is that the problem with the Dynojet dynos is that they are NOT accurate. Many say how they are the most accurate. They are often repeatable, but certainly not accurate. Back when Mark Dobeck first developed the DJ100 dyno, he was upset that his dyno didn't read 119hp for a stock 1985 Yamaha V-Max. It read in the 90's. He was missing some very big factors (two bevel drives, countless bearings and flex couplings, fluidic drag as well as rear wheel inertia) trying to obtain a reading similar to a water brake dyno run directly off the output shaft of the transmission . Thus the Dynojet's have inflated numbers in order to match the 119 the magazines measured on the Kerker and Webco dynos. They've changed the factors several times over the years, but never returned to zero inflation.

I've owned a DJ Model 100 since the old DOS software days. I tested back to back revision of software and it was surprising how a new revision would read higher or lower than the previous when run back to back within minutes of the previous run using the same correction factors. I worked closely with the folks at Dynostar when they were trying to figure out the methodology employed for their inflation factor. Adding 20 hp was incorrect as 5 hp minibikes would test at 25 hp. Adding an inflation % didn't work because 300 hp bikes would become 360 375 hp bikes. They seemed to have a factor that increased up to a certain % based on hp measured and then a decrease in % after a certain point in order to keep numbers from getting too big. Absolutely crazy.

Factory Pro, Land & Sea and Superflow read lower than DJ as they never tried to make their units read 119 hp for the '85 V-Max.

It's been posted many times before, but Dobeck's confession is here:

The Story Behind the Dynojet Chassis Dyno - The Truth Meter - Hot Rod Magazine

Thanks for that info, it was an interesting read. Two things: one, 1985 was over 25 years ago, last I checked. And most shops worth their salt are now using the DJ250 eddy - current load control dyno from Dynojet, a far cry from a DJ100.

Second: we have dyno tuned many Vmaxes from that era, and NONE of them dynoed at 119 rwhp on our dyno. The most I've ever seen on a bone stock Vmax was 110. The best one did 122 rwhp - after a four into one pipe and a Stage 7 jet kit. So again, interesting read, but I think the jury is still out on the premise of making a dyno read what someone thought a Vmax should be at.

Regardless of all of that, Dynojet's chassis dynos have become the standard in the industry in all forms of motorsports, and the SAE correction factor the standard when comparing one chart to another. Bottom line: the only numbers that count are the "before" and "after" gains that you see, I think we can agree on that!

 

[Mr Brown]

Yeah, well my bike made 297.4 on a DJ dyno, n I got the sheet to prove it, so I'm, like, all badass n stuff right bro?
Dyno numbers mean nothing by themselves, as stated the before and after are all that matters. Give me a timeslip from the strip over a dyno sheet ANY day!

My bike really did make that, with a boost spike of 26 lbs, and it hurt the motor. Rudy fixed it, and now it makes about 240. Now I need the tracks to open so I can learn how to ride it.....

 

[cwalker2]

1985 was over 25 years ago, last I checked.

Nice opening sarcasm. As far as I can tell, the physics behind rotational inertia hasn't changed since then. If it has, please forgive my lack of knowledge regarding current changes in the world of physics.

And most shops worth their salt are now using the DJ250 eddy - current load control dyno from Dynojet, a far cry from a DJ100.

You do realize that the only physical difference is the chassis that houses the drum and the addition of an eddy current brake, yes? The drum design and pick up have been the same for Model 100, 150, 200, and 250. There is no major redesign in the parts that measure the acceleration of the drum. The biggest change was moving the pick up location from inside the drum area (flag on drum of the 100) to the external wheel on the 150 and later. Since then it's been the same. Yes, the moment of inertia changes with the addition of an eddy brake but that does not affect/inertia sweep testing when the correct value is entered. They still employ the same methodology. Back during the conversion to windows (WinPEP) you didn't even need to use the hardware stack that exists on the current gen of DJ units. The software had a user selected option, internal interface card or hardware stack. Yes, I tested the new "Windows" software back in the day.

Second: we have dyno tuned many Vmaxes from that era, and NONE of them dynoed at 119 rwhp on our dyno. The most I've ever seen on a bone stock Vmax was 110. The best one did 122 rwhp - after a four into one pipe and a Stage 7 jet kit. So again, interesting read, but I think the jury is still out on the premise of making a dyno read what someone thought a Vmax should be at.

The Jury may be out? Dobeck made a statement regarding how he designed the tool. There's nothing to decide.

A good running 85 V-Max should read about 117 to 120 ponies on a DJ. The 86 (there was no 87) 88 and later maxes all use a more restrictive exhaust. Oddly they DID use larger v-boost valves in order to make up for the more restrictive exhaust than the 85, but I've never seen a stock 86 and later Max make more than 110 to 112 ponies on the DJ, myself.

On a different note I had a 1985 max in here a little while ago that was bone stock (amazing find). I got to use it to see how close Dynostar had come with their version of DJ replication factor and incredibly it read 118 - albeit once the carbs were cleaned and a new air filter was installed.

Regardless of all of that, Dynojet's chassis dynos have become the standard in the industry in all forms of motorsports, and the SAE correction factor the standard when comparing one chart to another. Bottom line: the only numbers that count are the "before" and "after" gains that you see, I think we can agree on that!

We'll just have to disagree on accuracy. If all Glocks shot 3 inches to the left at 21 feet, but they shipped more guns than anyone else, you still couldn't say "Well 3 inches to the left is the new bullseye." I still had to show Dynojet number to my customers even when using a non-Dynojet dyno and I'm glad the last dyno manufacturer I bought from had a good equivalency factor, but it always bugged me that the DJ factor results were higher than the step and hold testing values. As I'm sure you'll agree, if you calibrate with a dead weight on your strain gauge and you believe the weight and you can believe the rpm, then you can believe HP.

I do agree that using SAE is the only factor that makes sense here in the States. I fully understand that it is more accepted to use DIN across the pond and that makes more sense over there. It's their own standard, but STD itself is simply outdated. Back when we wanted to show muscle cars making a ton of power, STD and SAE-Gross standards where used, but who cares if the engine in a car was tested at the factory for power numbers without a water pump, alternator, air cleaner and perhaps using non-standard long tube headers? Getting an inflated number that had nothing to do with the engine as installed in the automobile we bought was just silly. It was junk testing back then and it's still no good now. When ever I see an STD chart I know it's about 4% high. Easy to do the math in one's head, but shows me the tuner is just dying to display a little more HP than the next guy.

I also agree with you on the before and after testing. To me it doesn't matter if it's measured in ft-lbs, yard tons or pumpkins per fortnight. Give me a repeatable dyno and I can tune with it.

 

[kml]

. The most I've ever seen on a bone stock Vmax was 110.

The Story Behind the Dynojet Chassis Dyno - The Truth Meter - Hot Rod Magazine

'Dynojet's final number-fudge was arbitrarily based on a number from the most powerful road-going motorcycle of the time, the '85 1,200cc Yamaha VMax. The VMax had 145 advertised factory horsepower, which was far above the raw 90hp number spit out by the formula. Meanwhile, existing aftermarket torque-cell engine dynamometers delivered numbers that clustered around 120. Always a pragmatist, Dobeck finally ordered his Chief Engineer to doctor the math so that the Dynojet 100 measured 120 hp for a stock"

Funny how even today factorypro and superflow Dynos all put a stock Vmax at 90 hp and that's what Dynojet got before they "doctored the math".

Another good read;
http://www.factorypro.com/magazine/mag_cyclecanada_Dynojet_dyno.html


cheers
ken

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[GNBRETT]

On a different note I had a 1985 max in here a little while ago that was bone stock (amazing find).

where is here exactly? do u own a motorcycle performance shop in NH? I have a buddy up there lookn for a tuner and doesnt want to travel too far since he doesnt have a trailer.

 

[mark3evo]

In the UK a std GenII with stock exhaust running standard 95 pump gas
runs average 176 - 180 Corrected on dyno.

add an akra 4 into 1 and ecu editor and you should see 188 - 192 rwhp

in 2 weeks my GenII gets the full 4 into 1 Akrapovic... i'll let you know

 

[smithabusa]

I think this further illustrates that you want to look at the improvements made versus the absolutes

% increase using the 3 different reporting methods are all in the ballpark of each other in my opinion. All show within a 2 hp increase from stock to tuned.

STD
194
177
9.6% increase

Uncorrected
195
180
8.3% increase

SAE
189
172
9.8% increase