Of course, a dyno needs load control to program fuel injection and I'm sure most people know that a model 250 has an eddy brake. A DJ may produce hp readings that are accurate enough for tuning, but what about the limitations of the software and the lack other features?
Ask someone who uses a DJ250 how they determine the correct A/F ratio at any given throttle position or RPM. They can't, because a DJ250 doesn't display the HP at steady state. It only gives HP readings when doing acceleration tests. Setting A/F ratios using acceleration tests is not accurate enough for tuning EFI because of the delay in the O2 readings. Besides that, using the inertia to do acceleration tests doesn't provide the proper load for tuning.
What about Tuning Link? It requires someone to guess at the best A/F ratio and the software sets the FI map to provide that A/F ratio. It does not set the A/F ratio to the best power. No given A/F ratio makes the best power on every bike and even considering a single bike, the best A/F ratio varies for different throttle positions and RPMs. Additionally, a 4 gas analyzer is sometimes needed to optimize a tuning point (like when the exhaust is in reversion). DJ doesn't have 4 gas capability.
Inertia is hard on bikes and the eddy brake. Also, it takes time from the tuning by waiting for the drum to slow down. Tuning a two stroke is more of a problem and it will beat up the eddy brake on an inertia system. Some dyno manufacturers (like MJP) offer dynos with DJ like inertia drums, but the drum does nothing to help in anyway. It's only a option to more accurately reproduce the BS DJ numbers so the shop can more easily sell their services. The problem is that the general public is conditioned to the inflated DJ numbers. This is why MJP (with O2,4-gas, and a FactoryPro-like interface that displays Steady State HP) is selling many dynos to replace DJ250's throughout Europe. There are even a few MJP's imported to the US.
Marc could have included DJ power as an output, but he decided to only output true HP. I respect his integrity to not buy into the DJ BS, although it ultimately hurts his business. I also respect him for trying to educate the masses. It's much easier to conform than educate every potential customer.
DJ needs to makes changes to their dynos to be more like Marc's, but doing so would mean that they were wrong all along. I don't see DJ doing that anytime soon. Until then, the FactoryPro dyno will always be better for tuning than what DJ offers.
Being the preferred dyno for any race series rules enforcement or being the industry standard is meaningless.
Scott,
I'm still waiting for a technical reason as to why you think Marc is full of crap.
Gary M
www.bmgracing.com
CCS SW AM #28
'03 Kawi ZX636R
'00 Duc 748R