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So, you bought yourself a fuelie?

by Chilly Willy

Motor vehicle manufacturers are mandated by the EPA to produce internal combustion engines that use a 17 to 1 air fuel ratio. With that much air, engines product less smog, but are running way too lean. The optimum (for a good running and long lasting engine) is something like 14 to 1. For carbureted engines it's relatively simple to fix by tweaking your carb. But, fuel injected systems have matrices stored in the Electronic Control Module (ECM) called maps which control Fuel/air and ignition timing for different RPMs and Throttle positions. To optimize your fuel/air mixture or ignition timing you need to either remap the Electronic Control Module or provide a downstream correction.

The MoCo's Solution

The stage I/II/III ECM Calibrations (aka chip burn, reflash, etc.) increases your idle mixture, and your rev limiter to 6200 rpm's. So, if your softail with hot cams, SE breather kit and White Bro's 2 into 1 pipe makes its peak hp at 5600 rpm's, (higher than the stock rev limiter), the chip burn will allow you to reach peak Hp. For those into getting the last bit of performance out of his bike, this might be important. Whereas for many of us, that higher rev limit may be of little to no practical value. And, the standard calibrations are one size fits all solutions which may still leave your bike running less than optimally.

So, Harley sells the Screaming Eagle ECM Tuner. Its software you load on a computer, with a cable and a dongle that plugs into your ECM so that you can reflash it with either standard SE maps, or your own custom maps. The maps that come with the system are the same as the ones your dealer offers, and as of this writing, there are no custom maps available from Harley. However, you can precisely adjust fuel/air mixture at different rpms and throttle positions, as well as advance/retard ignition. It comes with directions as to how to adjust settings based on feel, dyno runs or track runs. You can take a track run, download performance curves from the ECM, make adjustments, and upload the new maps.

The dongle is a security device that does not allow you to use the system on more than one bike. The first time you use it on your bike, it handshakes with the ECM and will forever only work with that ECM. Own two fuelies? Get two systems.

Power Commander

The Power Commander is a fuel injection and ignition timing adjustment unit that plugs inline with the bikes' stock ECM. Changes are made to the bikes fuel and ignition curves without making any permanent changes to the bikes' ECM. The PC uses original equipment style connectors allowing you to plug it in without splicing or cutting of the wiring harness. Removing the PC returns the bike to its previous stock condition.

The unit comes with computer software and a link cable that allows you to upload maps or to fine tune your maps. The PC is supplied with a base map, stored in the microprocessor, which generally will provide an improvement for stock bikes. Alternate maps are available for most typical configurations (i.e. TC-88 w/ stage 1 calibration, SE Air Filter and V&H Staggered Dual pipes). Each PC is supplied with a CD-ROM with most common alternate maps. More maps are available for download on their website. You can also change the fuel curve with the faceplate buttons. This adjustment moves the fuel curve richer or leaner in each area of the map. For instance, if you're heavily loaded or its particularly hot weather the PC can be temporarily adjusted at the faceplate to eliminate the "pinging" that is so common during these conditions. If you are about to make a long highway run, you can temporarily make the mixture more lean for better mileage.

For some bikes, Power Commanders can also adjust the ignition curve for increased throttle response, increased peak power, or to eliminate detonation. On most models the ignition curve is close to optimum for "pump" fuel.

For greater optimization or to develop a custom map for a special application, there is a network of "Dynojet Approved Power Commander Tuning Centers" throughout the country that can dyno-tune your bike. See to find a local tuning center.

One poster (MRBHD) had a PC installed in his 98 bagger. His Comments: "The bike had the HD stage II and Sampson slip-ons already. On the dyno prior to the power commander, the bike made 58 HP with about 60 ft-lbs of torque as verified by the dyno. After the power commander the bike now makes 76 HP with about 72 ft-lbs of torque! All of these are at about 3800 rpm due to the stage II cam. The bike now runs FANTASTIC, and it doesn,t ping!!!"

Will a Power Commander Void My Warranty?

Well . . . You shouldn't have to worry about that. And the Power Commander web site has a FAQ that discusses this issue. But, if you are concerned, check with your dealer. And if you don't like the answer, check with other dealers in the area. Some would suggest that you could simply unplug the unit before you go in for maintenance . . . But that would be wrong . . .

The Downside . . .

Fuel economy. When your bike runs lean, you burn less fuel. If you make your fuel/air mixture richer, you can expect a drop in MPG. One poster experienced a 10 MPG drop using a standard map for his bike. He thought Dyno tuning might provide a more optimum map and fuel rate.

What to do, what to do?

If you can afford it, if you have a better than average understanding of how to tweak maps, and you want fine control over your ECM, the SE ECM Tuner is certainly a viable option.

Many in this group like the PC and enthusiastically recommend installing them. The controversy is whether to do the MoCo's ECM Calibration first, or to save ~$150 and use a PC map for a bike without the calibration.

The stage one setup will enrich your idle (which the PC doesn't) and will increase your rev limiter to 6100 RPM (which the PC also cannot do). So many feel (some don't) that the MoCo's ECM Calibration should be done regardless.

If your PC craps out, and you have a stage 1 kit, you can simply unplug the PC and revert to the OEM system in the matter of minutes, and you're back on the road with no lean condition to worry about. The extra $150 might be cheap insurance.

Finally, there are hundreds of messages on this topic in RMH. A Google search of the archives will give you a wealth of experience with these issues.

There are also other online forums which go into more technical detail:

Harley Email Digest
Harley TC88 Email List