Tuneboy finally does open loop


Jun 23, 2006
Just got a call from my tuner who told me that he was finally able to achieve open loop at all times with Tuneboy.

Contrary to what it says on the Tuneboy website, lowering the A/F values below 14.5 will not achieve open loop in areas where the bike is programmed to be in closed loop.

A couple of months ago, my tuner lowered every single value that was listed at 14.57 (and that one at 14.7) below 14.5 and couldn't get open loop. He even went so far as to lower those A/F values to 0 and still could not get open loop. His remedy was to simply order a Dynojet O2 eliminator. However, his remedy wasn't wihtout a few bumps.

Dynojet lists an O2 eliminator on their website for Triumphs (76423006), which costs $15, so I ordered it and sent it to the tuner. He tried it but could not get it to fit. Dynojet swore up and down that the part was made for the Rocket III and that my tuner was incompetent.

I asked for help on the discussion forums and got it (Thanks Tom & Sam!!!), and determined that we Rocket captains need the O2 eliminator that comes with the PC III package for Rockets (76423016), which also costs $15 but does not appear on Dynojet's website.

I had a hell of a time ordering the correct O2 part. I went through 3 different reps before I was able to order it and was told "We stopped making 76423016 because it was flawed - 76423006 is its replacement," "You can only get 76423016 with the PC III," and "76423006 is an enhanced version of the 76423016, so you need to order 76423006."

I did have problems with UPS delivering the part to my tuner, but he did finally get it and did finally get that custom Tuneboy map finished with no closed loop.

The bad news is that I can't get anybody to drive me down until Saturday morning, which I guess isn't a huge deal since it isn't supposed to stop raining until late Friday / Saturday.
I apologize for the ignorance question, but there has to be others out there that don't know what you're talking about....besides me

Can you please explain what the difference between "open loop" and "closed loop" is and why would it be important?

Inquiring minds want to know...and I don't have a clue:eek:
A short and simple explanation...

The Rocket has an engine management system that is controlled by the ECM (Engine Control Module). Many sensors give an input to the ECM and it then makes decisions on how to run the engine, and does so by adjusting the amount of fuel the injectors squirt out and adjusting the ignition timing and so on.

To simplify things lets make believe that the only sensor the ECM reads is the O2 sensor. Based on that reading the ECM can calculate if the mixture is too rich or too lean and make adjustments to get the best politically correct pollution free burn. So it is running in "Closed loop", the loop being.... O2 sensor to ECM to fuel injector to combustion chamber and back to O2 sensor.

"Open loop" happens usually when the engine is cold or some of the sensor readings are way out of spec. During "Open Loop" the ECM doesn't rely on the sensors, but preprogrammed maps for the injectors.

Why do we want to be in "open loop"? When we are in closed loop we have little control over the air/fuel mixture because the ECM is trying to keep our emission levels low. But when we are in open loop we can reprogram those pre programmed maps to enhance our horsepower levels. Yesssssss... we want more horsepower at the expense of being stinky.:roll:
Thanks Tom for the explanation... that helps a lot...

So if someone has invested in a TuneBoy, they may not be getting all of the impact becaused the ECM is modifying the downloaded tune as we roll down the road?

Only when we're in "open loop" is the bike running the exact tune that we downloaded?
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Just to chime in on this subject, I originally had popping out the exhaust and a bit of cutting out at even throttle no matter what gear or what speed. I installed a PC111 with the O2 bypass, and it fixed life (except fuel mileage). The Tune boy came out and I wanted to open the secondary throttle plates with it and fix the speedometer inaccuracy. I removed the PC111 and O2 bypass and the bike started the same old problems. I tried a couple of different MAPS to no avail, the I reconnected the O2 bypass, but left off the PC111 and the bike runs great although I believe I can tinker around with Tune boy to lean it out a bit, it seems to rich.
The ECU is closed loop in the areas where A/F ratio is 14.5 and higher. This is the A/F map in Tunedit. It is really at small throttle openings (15% and lower) that it is in closed loop however when you are cruising at 65 mph you are probably operating in this area. I have been told by tuners the same that TTG's tuner is saying---what is the point of a custom map if the ECU is going to trim it in closed loop back to 14.57?
Danno- I will post a thread in the trading tunes section that shows where to add fuel in Tuneboy to stop decel popping. However it will return somewhat because of the closed loop, but not nearly as bad.
Correct part: #76423016 (not listed or pictured on website)

Incorrect part: #76423006 (listed and pictured on website)