I installed the JD tuner on my TE630. Simply put, it works. I'm happy. But...I wonder how it works. The instructions with it talk about various throttle positions and rpm ranges. Except that the unit doesn't read throttle positions or rpms. It intercepts two wires going to the actual injector jet only. Those wires tell the injector what to do...how much fuel to inject at any given instant. The injector head doesn't know or care anything about throttle position, so I find it hard to believe that those two wires contain any throttle position or rpm information. So, the JD unit intercepts the instructions to the injector, alters them somehow, and then sends them on their merry way. But...how does it know what alterations are needed?
did you read the instructions? It does know position and does display this on the unit when it is in use via the lights. Unless you have a CO meter or Dyno you simply tune it to how it runs best while riding. EZ and works great. If you mount it temporarily to the bars you can watch when it is at green (low) Yellow (mid) or red (top end) and then adjust up or down and see what works best. The PRM and position data is already in play via the ECU and sensors. All the huskys need to go richer and rule of thumb seems to be a little on the green, a little more on the yellow and sometime even more to quit a bit on the red.
Yes, of course I read the directions. And everything on the JD website. And your response still doesn't answer the question...the JD tuner does NOT interface* with the ECU, and I can't see any way its little computer brain knows what the throttle position is. The only data it receives is a signal telling the injector what to do. It must "goose" that signal a little and I'm wondering how it decides when to goose and by how much, given that it doesn't know anything about throttle position. And it certainly doesn't know anything about temperature, rpms or air density. Only the ECU knows those things, and it decides what signal to send down the wire to the injector. Said signal is intercepted by our friend from JD and then...what? I'm not saying it doesn't help the bike run better...it does. It's just that the analyst in me wants to know how...my experience is that, when I know how something works, I tend to deploy it better. *...and by "interface," I mean have a two-way conversation with it.
My Guess: Based on the fact that it has two wires in and two wires out and only touches the injector electronically (as well as physically) and has no communication directly with the ECU... I'd pretty much bet the house that it simply intercepts the ECU's output pulses to the injector, and simply adds or subtracts to the pulses based on the device's programming. It must have some pretty sophisticated algorithms to be able to calculate throttle position, but that could be accomplished with fuzzy logic based on the rate of change of injection pulses. One thing that leads me to believe there's fuzzy calcs going on in the background is the fact that I'll sometimes see two or three lights lit while coasting with the throttle closed. Also, I have yet to see all the lights lit when I'm at WOT for a few seconds... so I know for sure it's not directly sensing the TPS. Bottom line: I think this thing is a pulse width modulator/proportional controller with some REAL good background rate of change algorithms calculating throttle position.
Jd told me it has a wireless connection that interfaces to the Flux capaciter and the rest is a trade secret
That could explain the strange urge I get to watch "Back to the Future" every time I ride my 449 since installing the tuner!
OK -- I got the scoop from the man himself, and I missed one obvious thing. I was right in that the JD tuner does not talk to the ecu. All sensor inputs go to the ecu, and only an injector signal comes back out. That signal tells the injector how long to stay "on" -- which is how the fuel is metered out. But (and this is the part I did not figure out), the signal is also timed to match rpms so that the fuel goes into the airstream only when the intake valve is open. So...the JD tuner can figure out rpms since the injector signal frequency = RPM/2. It doesn't need the Hall Effect sensor input to do it. The tuner also knows how long the signal is, which is a rough proxy for throttle position, but also a signal for the load on the motor. The tuner then tweaks the duration of that signal according to its settings and, voila, you have an altered fuel map without doing anything inside the ECU, and without needing any input from any of the FI sensors. For the "transition" settings on the tuner, it looks at how quickly the frequency and duration are changing, and from that it figures out that you're twisting the throttle one way or another. It doesn't directly read the throttle. Pretty slick, I must say. Why hack the ECU when you don't need to?
I was wondering the same thing as you. Thanks for the followup with explanation. If the weather cooperates, I'll get to try mine out this weekend!
Sorry I did not do a good job explaining. The TPS and all other input information is already done by the time it gets to the injector, all the JD is doing is modifying the timing and duration to add or subtract from it. My "The PRM and position data is already in play via the ECU and sensors." was my simple way of explaining the same thing. did you speak to James directly? He is a real nice guy. We have had many long chats about this stuff and it is interesting. He is a good riding too. anyway glad you got a good explanation instead of my butchered one.
I want one! The nice thing about motorcycle technology is it keeps getting better and better making our lives easier. I'm assuming it is essentially plug and play with no wire cutting or fiddling?
yup, plug and play. disconnect one connector, plug that into a harness, plug other connector into what you just connected, attach a ground wire. ride.
The JD tuner is a very elegant solution to a problem that is not really that complicated. I have never been eager to install a device that replaces the ECU's role. A modern ECU does a lot of things and has been subject to tens of thousands of hours of testing and development. The only thing "wrong" with them is that the emissions and economy rules require that they be configured to optimize emissions and economy. The motor benefits from running just a little richer, that's all. What's interesting is that it would seem there is no reason why this approach could not be applied to any FI bike. For example, the ECU in the BMW 1200cc R-bikes is notoriously hack-proof. Right now, the only real tuning option is to fool the air temp sensor into thinking it's cooler out. The JD approach would surely work on the R-bikes, wouldn't it...? That's maybe the largest single motor application in the industry...JD could make some bucks!
It was installed and running on my 630 in about 10 minutes, 5 minutes of which was pulling the fuel tank. I spent longer than that fiddling with mounting locations. I ended up setting it atop the battery with a piece of plastic and some velcro, held in place by the battery bungee.
A couple of questions. Is a JD Tuner beneficial right out of the package? Are rider inputs required? How will it know if you had a 12 port injector or a pipe?
Absolutely! I plan on getting a Hayabusa or ZX-14R next spring and a JD box for those would be awesome.
I was quite happy after installing the Arrows with their new ECU. But then I got the JD and am even happier. Hell knows how it all works. There must be some very clever people out there.
It comes with the recommended settings for the particular bike for which it is bought. Rider changes are not 'required' but may provide benefit in some cases. It wouldn't know if you had a 12 port injector or aftermarket pipe. In those cases, you may want to talk to someone at JD first to get their recommendations.
it is preprogrammed for the bike, you tweak it from there. Don't "have" to do anything and will see better running and power but tuning it to your needs yields even more.
A have the JD on my SMS630 and it is great. A friend has it on his 2012 KTM500 and also says it makes a huge difference to that bike. Sounds like any FI bike can use a JD to help it reach its potential. Cam.
