Dyno run correction method

[mbohn]

I recently had my bike dyno'd and the data given to me weren't corrected for altitude (or temperature or humidity). I did a little googling and found the following link:

http://www.wahiduddin.net/calc/calc_cf.htm

that explains the SAE method for correcting a dyno run for altitude, temperature, and humidity. Thought this might be of use to someone.

I've also attached my (corrected) dyno run along with a comparison of what Ducati had on their web site. A few observations:

1) There is a big discrepancy above 7500 rpm. I thought the Ducati data would be crank not rear wheel but if that is the case why is my torque as good or better between 5200 and 7500 rpm? I'm also wondering if the Ducati data includes ram air effect?

2) It looks like for my run they could have gotten closer to the rev limiter. The last point looks like it was beginning to shut off but that is a very low rev limit. I know I've hit it just above 11000 rpm, not 10200 as shown on the graph.

3) Looks like the fueling could be improved a lot between 3000 and 5200 rpm.

4) Peak hp is 104 at 7290 rpm for my dyno (rear wheel) run vs 118 at 10700 rpm for the Ducati data (crank?).

My bike is stock as far as fueling/exhaust is concerned. Dynojet dyno for my bike.

Any feedback would be welcome.

[mbohn]

Any body?

[OldBaldy]

I'm afraid it's almost meaningless to try to compare posted manufacturer HP numbers against a specific bike's dyno run.

Dynos vary so much in HP output that making direct comparisons is mostly a fruitless exercise - especially when one is comparing dynos of potentially different makes, models and correction factors and assumed frictional losses (yes, the Duc numbers are calculate numbers with assumed frictional losses added back to simulate crank HP numbers - a ridiculous concept in itself)

I wouldn't lose any sleep of the differences you;re seeing - rather compare your own bike against others on that same dyno, using the same correction factor, or use it as a baseline for any tuning you do. That's where the real value is, IMO.

Still, an interesting question, in terms of the difference in the shape of the curves!

[mbohn]

Let me ask a different question on this situation.

Would I benefit from dyno tuning with my stock exhaust system? I don't plan to go to aftermarket exhaust in the near future.

As I look at the torque curve, the dip between 4000-5000 rpm doesn't matter on the track. I spend all my time between 6000 and redline and there the torque curve is pretty smooth.

But I've been told by one tuner that Ducatis run rich in that range and that tuning can bring out more power. I'd hate to think I'm missing something that could be brought out by a good tuner.

Thoughts?

[Nove-R]

Originally Posted by mbohn

Thoughts?

Cost/ benefit.

[mbohn]

Originally Posted by Nove-R

Cost/ benefit.

Ok, but I need to get a handle on the benefit. I can determine cost pretty easily.

[749Seddie]

Originally Posted by mbohn

Let me ask a different question on this situation.

Would I benefit from dyno tuning with my stock exhaust system? I don't plan to go to aftermarket exhaust in the near future.

As I look at the torque curve, the dip between 4000-5000 rpm doesn't matter on the track. I spend all my time between 6000 and redline and there the torque curve is pretty smooth.

But I've been told by one tuner that Ducatis run rich in that range and that tuning can bring out more power. I'd hate to think I'm missing something that could be brought out by a good tuner.

Thoughts?

My personal opinion......I would have the bike dynoed by a certified Dynojet dealer. If you are not going to add an exhaust right now, at least add a PCIII. This device will help smooth out the power curve, and you may gain a little horsepower. The main benefit would be to get the cylinders running equal, and have better throttle response. This will be noticable on the track coming out of corners, etc. The horsepower number that Ducati is quoting is at the crank(I think). Most 749S that I have seen dynoed have come in around 100 to 105 RWHP.

[mbohn]

Originally Posted by 749Seddie

My personal opinion......I would have the bike dynoed by a certified Dynojet dealer. If you are not going to add an exhaust right now, at least add a PCIII. This device will help smooth out the power curve, and you may gain a little horsepower. The main benefit would be to get the cylinders running equal, and have better throttle response. This will be noticable on the track coming out of corners, etc. The horsepower number that Ducati is quoting is at the crank(I think). Most 749S that I have seen dynoed have come in around 100 to 105 RWHP.

With altitude correction I'm at 99 and 105, right on the money.

Man, I sure would like to feel this bike at sea level! Another 20 hp !!

[Nove-R]

Originally Posted by mbohn

Ok, but I need to get a handle on the benefit. I can determine cost pretty easily.

The stock ECU is detuned slightly to accomodate sound and pollution restrictions. Adding a PCIII and getting it tuned on a Dyno will maybe add a few HP at best. If it idles roughly or stumbles at certain RPM and those problems are fuel related, then you can probably fix them.
Considering that the retail price for the PCIII plus dyno time for the tune will cost you over $600.00, it doesn't make any sense to me.
If you modify the engine somehow or add a larger/ no catalytic pipe or do air filter mods, then you need the PCIII to correct the air/ fuel that will get thrown out of whack.
There seems to be this belief that adding a Power Commander by itself will add more power (it's probably the name ). Not really. You mod other parts of the bike- exhaust, cams, airbox/ filter, etc, and those mods add horsepower. The PCIII makes those mods play nice with your bike. After the tune, you'll make more HP, but not because of the PCIII, rather because the mods that are now working properly with the bike, as they were designed.

[749Seddie]

Originally Posted by Nove-R

The stock ECU is detuned slightly to accomodate sound and pollution restrictions. Adding a PCIII and getting it tuned on a Dyno will maybe add a few HP at best. If it idles roughly or stumbles at certain RPM and those problems are fuel related, then you can probably fix them.
Considering that the retail price for the PCIII plus dyno time for the tune will cost you over $600.00, it doesn't make any sense to me.
If you modify the engine somehow or add a larger/ no catalytic pipe or do air filter mods, then you need the PCIII to correct the air/ fuel that will get thrown out of whack.
There seems to be this belief that adding a Power Commander by itself will add more power (it's probably the name ). Not really. You mod other parts of the bike- exhaust, cams, airbox/ filter, etc, and those mods add horsepower. The PCIII makes those mods play nice with your bike. After the tune, you'll make more HP, but not because of the PCIII, rather because the mods that are now working properly with the bike, as they were designed.

I wasn't claiming big horsepower gains....see my post! I was saying to use the power commander to smooth the power out, thus creating faster, easier exits from corners(better throttle response). He stated that he wasn't going to get an exhaust anytime soon, so this would be a noticable improvement on the track. It seemed like he wanted to get the fuel right. If it were me I would get a pipe,filters, and PCIII to start with. Not sure of his budget