Last month we covered installing a Yuill Brothers Stage 2 Kit on our 2007 Road King Custom. This month we'll explain how we tuned the bike and report our performance results. Plus we'll look at a self-tune versus a custom dynamometer tune.
You'll recall that the Yuill Brothers Kit included a high flow air cleaner, exhaust system, gear driven cams, and a MasterTune TTS ECM reprogrammer. After installing all the parts, we used the TTS to reprogram the stock ECM with a Yuill Brothers supplied TTS base calibration file (YA179000.MT7). Then we hauled the bike to The Dyno Difference in Dallas, Texas, where owner, Ed Dahir, spent the day tuning the bike with both the MasterTune TTS and his own custom setup. The following table shows maximum horsepower and torque numbers and gain over stock.
|Horsepower Gain over Stock||Torque Gain over Stock|
|HP||Gain||% Gain||Torque||Gain||% Gain|
|Yuill with Vtune||85.4||18.6||28%||105||22||27%|
As you can see, the Yuill Brothers base calibration file delivers some very respectable results right out of the box. That's a testament to how much effort they invested in tweaking the map to match their parts. The self-tune with the MasterTune Vtune program made only modest gains over the base; but by incorporating real data from actual bike runs, the difference is a smoother power curve and a better running engine. No matter how good the vendor's base calibration, until you can allow for bike-to-bike variables you can't optimize performance for a particular bike.
This is especially true for a custom dyno tune. Ed's final tune, using his setup, produced slightly less maximum horsepower and slightly more maximum torque. But the real story is that Ed produced gains in both horsepower and torque in the low to mid (2,500 to 4,500) rpm range and that on the whole he created a significantly smoother power curve. Both of these created a positive effect on the rideability of the bike.
Our conclusion is that the differences in these three states are small but tangible. A base calibration file from a vendor, like Yuill Brothers, that spends the time to tune it for their parts will let you run well. Then, to optimize the tune for an individual bike, you need some self tuning using whatever tools are available, preferably a high quality product like the MasterTune TTS. Finally, to fully tune all the variables for best efficiency and overall rideabiltiy, you need to let a qualified tuner, like Ed Dahir, tweak the bike on a dynamometer.
Dyno tuning is a small extra cost for a big gain in the quality of the ride.