This is a story of unintended consequences; how one small change can set into motion a series of modifications, ultimately achieving a result that exceeded initial expectations.
The motorcycle is a 2012 Triumph Tiger 800 Roadie. The initial, small change was the installation of an aftermarket muffler. The OEM muffler, to me, looks over-sized and unbalanced compared to the rest of the bike. And while I oppose loud motorcycles, I do like to hear at least a bit of an exhaust note. So I replaced the original can with a Leo Vince aluminum slip-on, keeping the dB killer installed.
The appearance of the Leo Vince can is pleasing to my eyes and I like the exhaust tone. The weight loss of 6.5 lbs is nice in theory but I cannot tell any difference in feel or handling. What I did not like was loud popping in the exhaust on deceleration from virtually any engine speed.
The decel popping indicates a lean condition that might cause damage to the exhaust valves due to combustion occurring in the exhaust ports. And the popping annoyed me a great deal.
So I decided to richen the fuel mixture and considered several options:
• The simple route of installing the Triumph “Arrow map” into the stock ECU. Based on a number of online comments of increased fuel consumption, I decided against this option and later checking the PC V software, which has the Arrow map included, I can well understand as many data points are as much as 35% richer than the stock settings.
• Booster plug: literally a plug-and-play insert into the wiring to ‘trick’ the ECU to richen the fuel mixture. Positive reviews of different brands in places like Motorcycle Consumer News made this an attractive option for reasons of simplicity and cost. Unfortunately, none of the suppliers have a plug available for the Tiger 800 but if you have a BMW, a Tiger 1050, a Yamaha and, soon, any number of Ducatis, a plug-in looks like the way to go. Jens Lyck of Booster Plug (www.boosterplug.com
) is very responsive to e-mail inquiries.
• Previously, I have had a positive experience with installation of a Dynojet Power Commander on a Suzuki DL650 WeeStrom with increased displacement (http://www.advrider.com/forums/showt...=278911&page=3
) so I purchased a PC V and Autotune, which is designed to continually adjust the PC V for optimum fuel mixture.
Nearing 15,000 miles, the bike was overdue for its 12 K mile major service. The PC V and Autotune install would be part of this service work. Incidentally, 5 of the 6 exhaust valves were all on the tight side of the clearance spec, so the cams had to come out. Not particularly difficult but fiddly as the packaging of components is tight.
As an aside, I have developed a little Xcel spreadsheet (visible in the photo above) to calculate required shim thicknesses when making changes for the purpose of eliminating manual calculations. Send a PM and I’ll be glad to share the spreadsheet via e-mail.
The PC V and the Autotune boxes fit under the seat; I mounted them behind the frame cross bar behind the battery.
Hooking up the PC V is relatively easy but somewhat fiddly with a number of connectors to be inserted between the existing connectors on the injectors and sensors (crank position, throttle position), more on this later. The throttle bodies have to be removed for access to some of these connectors.
Power-wise, the Autotune should be connected to a switched circuit; I spliced into the wiring for the heated grips plug under the fuel tank on the assumption that this circuit is not part of CanBus. The Dynojet instructions are clear and well-documented.
The Autotune receives its signal from a wide-band oxygen sensor that replaces the existing O2 sensor, which is located on the exhaust pipe, just after the junction of the three header pipes. The original O2 sensor has 12 mm thread, the wide-band unit is 18 mm. So the headers had to come off and the bung was re-cut with 18 mm threads by Gary Okoren in Golden, CO, an exceptional craftsman.
The sensor can be tightened on the bench, getting the header and brackets for the skid plate installed is a bit tricky with the sensor installed but is doable.
Otherwise, installation of the wide-band O2 sensor was straightforward. All the parts are supplied in the box, including a plug with resistors that is inserted into the bike's wiring harness connector for the original O2 sensor. Also provided is a bung to be welded on to the exhaust pipe if your bike was not originally equipped with an oxygen sensor.
Once all the important parts were installed but before hanging the plastic back on the bike and securing the fuel tank, it was time to check that the engine would run. No problem, it started right up and sounded good. Plugging the laptop into the PC V indicated that all was good there, too.
But there were a couple of snags: the fuel gage indicated empty in spite of at least 1.5 gallons in the tank and the ‘check engine’ light was lit. Head-scratching and checking with smarter people than me, motodutch and Bob Wells, the latter with a diagnostic tool; after a couple of false starts I became convinced that there was no major problem and finished the assembly of the bike.
Except for more snag: the fuel tank fasteners wouldn’t to line up because of minor interference between the fuel tank and the air box. Turned out that one of the new PC V connectors was jammed between the top of the engine case and the throttle bodies, preventing the throttle bodies to fully seat in their bores and thus raising the air box a fraction of an inch, just enough to prevent the fuel tank to fit properly. The parts on this bike are just about shrink-wrapped in place.
Once corrected, the ‘check engine’ light was still lit. One small hose on the underside of the air box had gotten left off, this hose leading to the MAP (manifold air pressure) sensor, one of the more important sensors in the fuel system. NOW, the engine ran really well.
With a fresh fill-up, the fuel gauge returned to service but it took about 500 miles for the ‘check engine’ light to go out. The light can be re-set with a diagnostic tool or Tune-ECU, or the light goes out after 40 engine starts, assuming no other problems.
So how does the bike work now? Very well indeed, better than expected. The decel exhaust popping is nearly gone, now is just a very slight and pleasant burble. Surprisingly, performance is significantly enhanced.
The engine has noticeably more torque at low RPMs. One minor irritant with this bike has always been the difficulty in a smooth take-off from a dead stop, a normal roll-off in traffic for example. It's been just a little tricky to achieve the right combination of throttle and clutch engagement. All that is gone now, hard to believe but starting off in 2nd gear now is easier than starting in first gear used to be!
Another observation: it is no drama rolling along in 6th gear at 2,000 RPM (about 30 MPH) and smoothly and strongly accelerating. In traffic, there is no need to rev higher than 3,000 to 3,500 RPM before upshifting.
Performance throughout the rev range is clean, crisp and strong. Every upshift is a joy with an instant surge of torque and power that is usually only experienced with race engines or at least engines equipped with strong accelerator pumps in the carburetors, and which has been missing in US spec street bikes for years.
This is how the bike should have been delivered from the factory, instead of with overly lean low-speed fueling to satisfy an artificial set of EPA-mandated conditions. As fuel economy is the same or better as before, emissions on a per-mile basis in real-world conditions cannot be particularly increased.
However, the stronger bottom end torque and wider power band now makes the close ratio gearbox seem even more inappropriate for this machine and overall, the bike feels quite under-geared. When it becomes time to replace the chain and sprockets, I will change the ratio to effectively spread the gear ratios, reduce highway RPMs and maybe increase mileage a bit. I have an Xcel gearing spreadsheet that I’d be happy to share, too.
Speaking of fuel mileage: now about 800 miles since the modifications, the last two tanks were burned on a mix of suburban surface streets, urban freeways and rural two-lane roads. My riding style is not overly aggressive, I tend to flow with traffic and move just a little faster than traffic on the freeways, which in these parts runs at 70 to 85 MPH:
Fill-up, some 600 miles after the install: 183.4 miles, 3.5 US gallons = 52.4 MPG. The trip computer showed 55.2 MPG
Next fill-up: 158.1 miles, 3.1 gallons = 51.0 MPG; trip computer indicated 53.0 MPG.
Earlier fill-ups showed similar data. All the fill-ups indicate slightly improved economy after the PC V and Autotune install by perhaps 5%. However, as part of the 15 K mile major service, I also installed a fresh set of iridium spark plugs and a new OEM air filter, which may improve mileage.
• The fuel gauge now reads consistently low as if the sensor has moved lower in the tank. Used to be that the top bar on the gauge would stay on for 20 to 22 miles after a fill-up, now it goes out in 6 miles. The low-fuel light now comes on at about 140 miles, used to be about 175. Not a biggie, just annoying.
• Secondly, the exhaust tone seems to be deeper, but not louder, than before. To my ears, it’s a pleasant sound, at steady speed not unlike the melodious tune my old 650 Bonneville sang at steady cruise. In the past, I have observed a similar deepening of exhaust note when the low-speed fueling was enriched, for example on an early 90s BMW M5 after installation of a Dinan chip.
• The inside of the exhaust tip is sooty. In the old days (before unleaded fuel, catalytic converters and electronic controls), a sooty pipe would indicate overly rich fuel mixture but nowadays, I don’t think so. Before the PC V install, the Tiger pipe was sparkling clean, yet fuel mileage now is a bit better. I’ve observed the same on cars: my Audi turbo with sooty exhaust tips has a lifetime economy of nearly 27 MPG while the wife’s 47,000 mile Lexus has an exhaust pipe that looks as if nothing has ever passed through it, yet her mileage is less than 20 MPG.
• How complicated is this install? Not particularly as it consists mainly of taking things apart and connecting other parts, and the Dynojet instructions are quite detailed. Some parts are difficult to reach and a variety of tools are required. I work slowly and methodically, take lots of pictures for later reference and still, I had to go back and do some of the work over. The bike was out of service for a total of three months, however this time was more related to my frequent business travels, family obligations and waiting for parts than due to the amount of work required. I have other bikes so I could still ride. All that being said, this install does require a significant amount of disassembly so experience with motorcycle repair and maintenance is a definite asset.
• The Power Commander V offers a number of features that I have not yet tapped into – I’m that pleased with the stock set-up. One of these features is that fuel mixture can be adjusted differently for each gear, so, for example, you can set the mixture lean in 6th gear to improve touring mileage, while retaining a richer mixture in lower gears for good response and performance.
In conclusion, I am very pleased with the result of these modifications, well worth the effort and expense. I do expect the bike to be even more pleasant to ride after the final drive ratio has been changed.