Last month, I suggested that increasing cam overlap and duration would help reduce operating temps on late-model Twin Cam engines. But as good as the simple trick of adding cams with some overlap might sound, it’s no cure-all either. Aftermarket camshafts sporting very much duration or overlap will generally increase manifold pressure (reduce vacuum) near idle. V-twins can ill afford this. Delphi’s system will try to compensate for this aggravation of a poor situation that Harleys have always suffered from anyway by adding excessive fuel, resulting in very rich idle mixtures and other downsides to low-speed tractability.
Look, it’s a fact of life that there are several elements conspiring to constrain traditional V-twin virtues—EPA smog requirements and the fact they must be halved in just a few more years, exhaust noise issues from the same bureaucracy and, not least, the state of the fuel we must run and fuels (E85) we cannot run. All of these issues create plenty of heat, and not just the kind that comes from internal combustion. Add greater rod angularity (accompanying longer strokes) in new 96″ Twinkie engines, and recall business from previous columns that suggests more operational heat is inherent in that, because of the slowdown and start-up velocities involved as the rods swing through their appointed path.
The point is there are a multitude of reasons why we’re suddenly noticing the higher temperatures radiating from our bikes. Seems to me we have a choice or two to make. We can live with it and/or work around the worst, with tactics like blending a little unleaded race gas with the swill from the pumps, carrying along little bottles of octane booster (preferably mostly composed of MMT or Duralt), buying more heat deflectors and/or engine fans, wearing asbestos riding britches or some stop-gap crap like that. Or, we can try to deal with the heat via a couple of cool technical advances and turn the “system” to our advantage.
The problem is there’s no single magic bullet that instantly kills off every issue we might encounter in our quest to beat the heat. What follows, therefore, should be viewed more as suggestions than solutions. (But a hell of a lot better than nada nonetheless.)
The 800-pound gorilla in the room (and on your 96″–110″ Big Twin engine) is the new closed-loop fuel injection. Or, perhaps more accurately, the fact that the whole EFI shebang is now monitored and controlled by sensor input—prime among them, two practically inviolate O2 (oxygen) sensors. Further, the OEM O2 sensors are of the variety known as “narrow band,” in that they function within an electrical range of one volt, keeping air/fuel adjustments at a nice legal, lean (and hot) 14.7:1 air/fuel ratio. We know that ratios of more like 12:1 are best for power (although not so much for mileage) and even 13:1 makes for a pretty good compromise. But most of us prob’ly haven’t thought in terms of cooler engine operating temps as part of that deal. Even if you have absolutely no desire to hop up your engine or defy the Clean Air Act, if your problems, like one reader, now include blisters on your legs from long rides on new Harleys, maybe it’s time.
For most of the dozen or more years that Harleys have sported EFI, the “brains” in the organization have been relatively simple open-loop designs. Some might even say crude, since modifying the parameters of operation started about a week after the original EFI Harley (1995’s 30th Anniversary Electra Glide) appeared. In all fairness, many of those modifications were pretty damn crude as well. Today, traditional options include simple fuel adders, piggyback ECM controller modules, and of course Harley’s own “better mousetrap,” the anything but simple, although quite capable (in the right hands), Race Tuner. In light of the factory’s unfortunate position relative to the federal government’s regulations, what remains to be seen is whether the Race Tuner will be capable of tweaking sensor inputs for better power (let alone less heat) on the latest EFI systems.
VHS vs. Beta
Meanwhile, the not-so-fettered gentlemen of the aftermarket have been busy. The emerging products that will matter in the long run all seem to have one basic concept in mind. As it happens, it all dovetails nicely with our current… uh… hot topic. The basics are one thing (a marketing man’s dream and potentially your best option) even though the details of best execution are still up for debate. (When the dust settles in the future, we’ll likely look back at this current state-of-the-art struggle much like we remember the VHS vs. Beta wars in the video world.)
What I’m trying to get at is this: Of the emerging technology that allows us to buy so-called self-tuning or auto-tuning closed-loop EFI replacement systems, all three options are capable of doing what’s needed to get air/fuel ratios into a range that provides better power and drivability with any given combination of engine components. The big bonus as far as engine heat is concerned, is that it can be reduced in the bargain—in some instances a lot. How cool is that? (Well, would you settle for 20–30 degrees?)
The three choices I’m currently aware of (and there will be more) have two things in common. They replace the stock ECM and they manage this self-tuning trick via manipulation of—and/or feedback from—the O2 sensors. From there, things diverge quite a bit.
Daytona Twin Tech has the TCFI-IID (specifically), which prob’ly works on stockers, but is marketed more as a hot rod setup for big-inch and modified engines, and naturally enough comes with wide-band (0–5 volt) oxygen sensors to replace the factory ones. As with all these contenders, things get started with a decent “base” fuel map, and adjustments are automatically made from there, based on feedback from O2 sensors. Then once preliminary adaptive maps are merged, the results are locked into the ECM via the provided software. The software, while fully functional for its intended purpose, is, for lack of a better way to describe it, a connect-the-dots sort of 2D setup. One of the earliest learning/tuning systems on the market, there are understandably some updates, advice and add-ons that you may need to get the most out of this system for 2006 Dynas and 2007 everything else, including EFI Sportsters.
Zippers’ Performance calls the system they offer Thunder Max. This system also provides replacement wide- band O2 sensors along with the ECM and implies it’s good-to-go on most any closed-loop Harley (or Harley-based V-Twin) provided the unit, its firmware and software are up to date and the proper application for your particular model. Some fairly extensive basic setup is best. No self-tuning systems can manage a FUBAR base map, and therefore benefit from one that’s in the ballpark in the first place. Perfect tune files arrive with far less saddle time (and fewer rider hassles from temporary weirdness while the system learns) if the respective (also somewhat two-dimensional) maps are close in the first place.
S&S Cycle Inc. goes its own way with the same basic idea, in that unlike the other two companies it won’t market its VFI (Variable Fuel Injection) kits directly to the public or through catalog vendors. (Although, naturally enough, there are systems for both S&S and Harley engines offered.) Rather, you must purchase (and should install and “baseline”) VFI though certified S&S Tuning Centers. Also unique is the sophistication in the S&S ECU (rather than H-D “ECM”) that allows tuning of the narrow-band factory sensors. Seems it’s all done with microvoltages that let the VFI get air/fuel ratios the engine likes within the one-volt range of factory oxygen sensors. (Pretty pragmatic, when you think about it, since there’s no warranty on any wide-band sensors when used on Harleys. Also, quite simply, if you ever need a new sensor you’re likely to find a stock one at your dealer, quicker, cheaper and more easily than a wide-band unit from anywhere.) Interestingly, while Thunder Max and TwinTec claim to manage as much as a 50 percent bump, VFI compensates automatically up to a 20 percent increase in power. S&S advises that from that point on, a new base map (best built by a knowledgeable S&S tuning center) is required. This matters if you are as knowledgeable as you need to be to get the most from the system. Among those of us who aren’t computer geeks, let alone serious full-time engine management gurus, there’s one other motive for leaving all the variables in Variable Fuel Injection to the experts. S&S software is very three-dimensional and a step or two more sophisticated than the home-study type.
Come to think of it, lest you suppose these systems are manna from heaven or simply plug and play, consider some long, intimate discussions with experts in each before you haul off and go for it. Check and see which system will serve your needs best with the fewest flies in the ointment. Stuff you might not even have considered, like the O2 sensor choice, can make or break your long-term results. Even details like compatibility with factory alarms, or cruise control systems, upgraded throttle bodies, or different injectors need to be factored in. The ability to master the software yourself, or to find someone who can, is essential. Setting up parameters for the systems which have nothing to do with closed-loop “normal temperature” operations as such, can mean spending a large quantity of quality time baselining cold start sequences and ensuring that all the other sensors, as well as the TPS, MAP and mostly IAC steps, are right on. Once done, it’s worth doing, since the system of your choice will take over nicely from there, and no dyno is required. You never get more out of auto-tuning, or any other kind of tuning, than you put in, including the option of updating older open-loop Delphi and Marelli stuff to the precision of closed-loop operation. But so far, self-tuning EFI is potentially the coolest plan for dealing with such a hot issue.