Dyno Run - RX3 on a DynoJet

[rtking]

I wanted to make sure the air/fuel ratio was good with my Akropovic slip-on muffler, so I decided to put the bike on a dyno. The power output numbers were only a bonus.

I have to say that I'm extremely impressed and pleased with Zongshen and the CSC RX3. As you can see in the plot below, my power output was very consistent, and the air fuel ratio was just about spot-on where it needed to be. It only runs slightly lean at wide open throttle between 8,000 and 9,000 rpm.

I didn't test with the stock exhaust (I probably should have to baseline.) But I have to believe the stock exhaust is not a lot more restrictive than the Akrapovic, so if you do change cans, do it for tone and weight, but not so much for power.

The guy running the dyno was impressed by the RX3. The shop services all bikes... European, Japanese, Chinese...and scooters too. He said that in his experience, Chinese bikes will come in with poorly tapped and aligned bolt holes, substandard quality, and a lot of imitation of other bikes' engines or parts. But he liked what he saw on the RX3. And he was also surprised that there wasn't a hard fuel cut-off like many Japanese bikes. The RX3 liked to rev past redline and up to 10,500 as you can see on the dyno graph.

Despite my enthusiasm about the horsepower number, I have to provide a caveat that every dyno is different, and every day's weather conditions are different. The main advantage of a dyno is to do a baseline (before) run, and a run again after changing a part. But taking just my numbers, and applying the standard 10% correction, it compares very favorably to the factory's numbers (as measured from the crank.) I'm impressed.

OK - enough babble. Here's the bike (first RX3 in the US on a dyno?), the corrected power and the dyno plot.

[rtking]

Here's a really short video of a single pull. I was behind a glass door, and the glass was pretty hazy, so the quality of the video isn't very good. But the muffler sounds good!

[youtube]mdRcapBu7To[/youtube]

[AZRider]

My own SOTP (seat of the pants) testing confirms your findings. This bike loves to have it's neck rung and is always ready for more. I've ordered a new seat, so I'm hoping my numbers will improve.

[SpudRider]

Thanks for posting the great thread, RT. I am adding this thread to RX3 Tech Sticky, under a new subheading, Zongshen RX3 Dynamometer Tests.

http://www.chinariders.net/showthread.php?t=14228

I am pleased to say I am not surprised by the excellent results. Zongshen manufactures superb engines, and the U.S. Delphi EFI on this Zong is excellent.

[SpudRider]

Originally Posted by azrider

my own sotp (seat of the pants) testing confirms your findings. This bike loves to have it's neck rung and is always ready for more...:

x2.

[Lee R]

Those numbers are just a couple horsepower shy of the Honda CB300 series and beat the older 250 by about 3 hp. Very nice output!

[rtking]

Originally Posted by AZRider

My own SOTP (seat of the pants) testing confirms your findings. This bike loves to have it's neck rung and is always ready for more. I've ordered a new seat, so I'm hoping my numbers will improve.

Which seat, George? The taller or shorter seat? I'm thinking that's my next purchase for my RX3. Love the bike, but I sit far enough back that a flatter seat would work better for me.

[rtking]

Originally Posted by SpudRider

I am adding this thread to RX3 Tech Sticky, under a new subheading, Zongshen RX3 Dynamometer Tests.

Many thanks, Spud! I'm honored!

[AZRider]

Originally Posted by rtking

Which seat, George? The taller or shorter seat? I'm thinking that's my next purchase for my RX3. Love the bike, but I sit far enough back that a flatter seat would work better for me.

RT, I ordered the tall and took advantage of the 20% sale, it should be here in the next few days. I'll post my observations after I've put on a few miles.

[keithmaine]

Originally Posted by AZRider

RT, I ordered the tall and took advantage of the 20% sale, it should be here in the next few days. I'll post my observations after I've put on a few miles.

I love the tall seat it is awesome, I do not have any long rides yet but the just the initial feel and seating position change feels so much better.

[detours]

You gotta love that flat torque curve and steady HP curve. That's some nice smooth power delivery right there.

[fratermus]

Very cool!

[Weldangrind]

Thanks for the dyno report, RT! When you say the A/F was a little low, what were you hoping for? According to the graph (which may be off), the A/F was relatively consistent until it leaned out at about 6800 and then again at 8200-8800. As far as I can see, it never leaned out more that 14.7:1, which I presume to be the target (not for max HP, but for efficient operation).

[rtking]

Hi Weld, actually I was saying that the air/fuel ratio was running a little lean between 8-9K rpm. Nothing alarming and I am pleased with the results. My concern was when I saw the header pipe bluing, and was afraid of a lean condition. The dyno graph demonstrates that me fears were unfounded.

There's some that say that richening the mixture to about 12.5-12.8:1 ratio can result in more power. Not sure how much power one can expect from a change in the A/F ratio. But given the engines' excellent reliability, I'm a bit loathe to do much around reciprocating assembly changes and any kind of drastic changes to air fuel ratio.

[Weldangrind]

There certainly is evidence to support that max power is found between 12:1 and 13:1. If I had access to tuning software, I'd certainly add a little more fuel to see what happens. What is the opinion of the dyno operator?