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Fat Duc O2 Manipulator

Fat Duc O2 Oxygen Sensor Manipulator

Fat Duc O2 Manipulator Review Summary
Review Summary
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A few weeks ago I received a breviloquent email from “Jason” at Fat Duc:

“Just wanted to make you aware of a new product that we’re seeing great results in curing many of the low RPM problems plaguing late model Ducatis.

The Fat Duc O2 Manipulator is a simple, yet effective way to alter the closed loop air-fuel ratio and reduce/eliminate popping on decel, improve throttle response and reduce surging.”

OK Jason, you snagged me.  “Sounds interesting”, I thought.  But I don’t have this problem, right?  I cured it with the installation of the “Euro” ECU and the 14-tooth sprocket on the GT1000, no?

Some sniffing around the forums turned up a gaggle of SportClassic owners who have tried everything but were still complaining about the surging, hiccoughing, popping, snapping and hair-trigger throttle response that seems to be endemic to Ducati SportClassics of every type, even after an ECU transplant.

I was getting a pop here and there, but nothing like it was before I brought the GT1000 to the ace mechanics at Duc Pond Motorsports in Winchester, Virginia, where somehow or another Donnie Unger talked Ducati NA into forking over a replacement Euro ECU under warranty.

I covered this almost one year ago in my “Ducati GT 1000 ECU, Throttle Body Balance and Lean Running Fix” article, and never looked back — I’ve been having too much fun riding the now-transformed GT1000.

The ECU and a 14-tooth sprocket I had them install transformed the bike, but I will admit to a throttle response that still could be a bit smoother and a lumpy idle that sounded like gremlins were shoveling in gas a spoonful at a time.

So why not take Jason up on his offer?  I had no idea what an “O2 Manipulator” was — O2 is oxygen, right?  And tell me again why I’d want to manipulate it?  And besides, isn’t this thing in the same category as those wacky carburetor vortex generators and fuel atomizers?

I was all ready to call Jason’s bluff on this one.

The thing arrived a few days later in a tiny package.  It’s a very professional-looking wiring harness (photo above) with simple instructions and a simpler note: “I think you’ll be amazed with the changes even with a stock exhaust. You’ll want to set it somewhere between a 13.5/1 – 13.2/1 reduction.”

The silver dot on the O2 Manipulator screw is the richest setting (highest Voltage reduction).
The silver dot on the O2 Manipulator screw is the richest setting (highest Voltage reduction).

The Fat Duc O2 Manipulator is apparently some type of electronic gizmo that’s way beyond my level of understanding.  It manipulates (makes sense, right?) the O2 and, I guess, fakes out the ECU into believing those gremlins are on holiday.

The device has a tiny little screw that allows “AFR” settings (which I assume means Air/Fuel Ratio?) between 13.0:1 and 14.2:1, according to the diagram on the single page instruction sheet.

Don’t ask me why, how or what this is all about — all I did was follow Jason’s instructions, and turned the screw until it looked like it was between the 13.2 and 13.5 setting he suggested.

After playing with the O2 Manipulator, I threw it on the shelf in the garage, where it bounced around for a couple of weeks, nearly forgotten.  Then the weather turned fall-beautiful again, so it was time to give it a whirl.

But first, the install.  As it turns out, the hardest part is tracing the wiring harness from the bike’s O2 sensor; it’s the only thingie plugged into the exhaust that has a wiring harness leading up into the guts of the bike.

2007 Ducati GT1000 oxygen sensor, plugged into right-side exhaust.
2007 Ducati GT1000 oxygen sensor, plugged into right-side exhaust.
Stock GT1000 connector; this is where the Fat Duc O2 Manipulator is plumbed in.
Post Fat Duc O2 Manipulator installation, with the two connectors tucked in to clear the seat.

I traced the harness a few times to make sure I had it right and discovered that it ended in a connector right under the seat of the GT1000 (see photo).  I’m not sure if it’s the same with any of the other SportClassics, but it shouldn’t be hard to find, once you start at the O2 sensor.

It took me literally 10 seconds to plum the new harness into the system and tuck it in — once I found it, of course.  “OK, now we’ll see”, I thought — pretty smug, thinking this entire exercise would be a flop.

But as soon as I started the bike, I could sense something different.  Was it me?  Or did it start quicker and jump immediately into a nice, smooth idle?

Where’s the lumps??

Earplugs in; helmet and gloves on as the bike was warming up, then I hopped on and pulled away.  Wow!  The throttle feels so…smooth!  I noticed the difference immediately.

Tearing around the back roads revealed the truth — this little manipulator gizmo has brought the bike to a whole new level of driveability.

Forget the lumpy idle and backfiring, which had been pretty much eliminated with the new ECU and 14-tooth sprocket combo anyway.  I could live with that.  What I really notice is that the bike now has an incredibly smooth throttle response — like no other fuel injected bike I’ve ever been on.  The little bit of on/off response, which even after the ECU transplant still reared its head after rolling on the gas when turning into a slow corner is completely gone.

The only way I can describe it is like going from Coltrane’s Interstellar Space back to Blue Train.  Smooth, baby, smooth.

Here’s where I can really tell the difference: I always ride with two digits on the shorty brake lever and I’ve trained myself to goose the throttle simultaneously with braking, when I’m double-clutching and downshifting.

I also like to hold or roll on the throttle while I’m braking and entering a corner to smooth out the transition and get on the gas quicker on the exit, a trick I learned in Lee Parks’ Total Control Advanced Riding Clinic.

This is a hard trick to get right, made doubly so on the GT1000, nearly impossible with the stock ECU and difficult even with the ECU changes on the Duc.

But now it’s like buttah baby; no problemo!  I’m pretty astounded actually — it’s really like a big, fat mellow filter has been draped over the throttle.  The engine has lost every bit of the raw harshness that it had before.  You can still tell it’s a Duc, but it’s tamed.

I have no idea if I just happened to hit the sweet spot when I twisted the screw on the O2 Manipulator, but I’m not about to change a thing to test it, sorry!  It’s just right as it is and I’m not going to take a chance.

And here’s something else — even with the 14-tooth sprocket, I could almost never preivously get the bike into 6th gear at anything under about 75 MPH.  And since I don’t ride on open roads or freeways, I’m usually down in 3rd and 4th max on the twisty country ribbons that start right outside my front door.

But lo and behold, I find myself in one or two gears higher than before, sometimes completely faked out, toeing up the lever, thinking it must be a mistake — I simply can’t be in 6th gear, right?

I can now take it all the way down to about 3k RPM in 6th gear, about 45-50 MPH, and it will pull right up to redline without a complaint as I twist the throttle.  Sure, there’s a bit of bumping from those big 500 cc pistons winging through their way back and forth through the 90 degree cylinders, but not a spot of the lugging and chugging and coughing that would make this a definite no-no before the O2 was, well, manipulated.

Now here’s the disclaimer: I have the Euro ECU and the 14-tooth front sprocket installed, but nothing else has been changed on the bike.  Stock mufflers, everything stock.  I use Shell Premium fuel always.  Other than that, nada.  And I’ve done no “scientific” testing at all on this — it’s all in what my wrist and little grey cells tell me.

By the way, I/we have no relationship with Fat Duc, financial or otherwise.  Jason sent us a sample gratis and that’s it.


The Euro ECU and 14-tooth sprocket made a world of difference on the GT1000 — I thought this was as good as it was going to get.

But my opinion is the Fat Duc O2 Manipulator is to the Euro ECU as the Euro ECU was to the original, harsh, on/off throttle and backfiring that plagued the bike right from the factory.  About another 100% difference.

I don’t know if the Fat Duc O2 Manipulator would do the same for a stock SportClassic, but for 80 bucks and — get this — a 30-day return policy, how can you go wrong?  I’ll bet the savings in fuel from being able to ride 1-2 gears higher than normal will pay for the thing in no time.

But don’t ask me to measure the fuel mileage — I’m having too much fun riding!  Next stop: Staintune!

wBW Tech:  Fat Duc O2 Sensor Manipulator
Available From:  Performance Boulevard, LLC Suggested Retail Price:  $80.00 + S/H
Colors:  N/A Made in:  Unknown
Review Date:  October 2008

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From “J.G.” (4/09):  “Thanks very much for working so hard producing a quality web site, I really appreciate it. It has been a great resource for me.

I wanted to chime in on the Fat Duc 02 Manipulator, it has made a big difference in how my 2007 GT1000 performs.  When I first bought my GT1000 the gearing was too high and the throttle response was very edgy.  I made a couple of changes to improve things.

I replaced the front sprocket with a 14 tooth sprocket which made the bike usable in city traffic and my dealer replaced my ECU with a Euro ECU.  This made a huge difference in the way the bike performed.  The gear range was finally appropriate for mixed city and highway driving and the throttle response was much less edgy.

However, there was still an on/off throttle response that bothered me in stop and go traffic and when throttling up coming out of corners.

I read about the Fat Duc 02 Manipulator on your web site and thought, for $80, it was worth giving it a try.  Installation was a breeze and your photos on the web site made it even easier.

You could tell it was working immediately.  The strange loping idle was gone, replaced by a smooth, steady idle. The on/off throttle response has been really smoothed out but, I still find myself being extra cautious applying throttle coming out of corners out of well ingrained habit (I suspect I’ll get over that soon).  I didn’t expect highway riding to change but, I was really surprised to find myself comfortably in sixth gear at 65 mph.  I have never seen sixth gear before under 80 mph.

The change I like the most is that the bike just seems easier to cruise with.  Before the 02 Manipulator I just could not stand following traffic, the bike had certain speeds it wanted to cruise at and was uncomfortable cruising at other speeds.  I found myself passing vehicles all the time.

Now it seems that the range of comfortable cruising speeds has widened and I find myself less inclined to pass.  This will help me retain my license.  This was the best $80 I have ever spent on a motorcycle.  I would highly recommend this for anyone with this bike.”

From “Duceditor”, the Editor at Ducatis Unlimited Connection (11.08):  “I was among those who had the privilege of testing the 02 manipulator during its experimental stage.  The unit was fundamentally the same as the one being sold except that the parts were hand soldered and thus, potentially, not as durable as the final, ‘for sale,’ item.

My findings, like almost everyone else who has tested this little gizmo, matched your own.  For a mere $80 the bike’s “carburetion” went from barely passable to perfection.  I, too, was simply amazed.

My bike is almost stock, the two exceptions being the modified cans you commented on in an earlier webBikeWorld posting, and the now almost de rigueur 14 tooth front sprocket.  Thus I can comment that there will be the same extraordinary results with the stock ECU.

Have no fear about tweaking the dial on the manipulator.  There is no magical “sweet spot,” just small changes as the f/a mixture is enriched a bit more or less.

I settled on the setting that is said to indicate a 13.2/1 ratio.  This is technically a bit rich, at least at idle – I can tell by the smell of the exhaust – but is absolutely buttery smooth, possibly because the said “richness” hides any imperfections in the F/I balance between the cylinders.

Nothing, of course, comes without some cost, and in the case of the 02 manipulator that cost shows at the fuel pump, which is now more in line with what one might expect with a high performance 1000cc twin – high thirties to mid forties MPG (depending on how enthusiastically one rides).  This in comparison to the low fifties the over-lean stock setup gave.

Still, all it would take to get the MPG back up there is 10 seconds with a screw driver.  Dialed all the way from the silver dot voids out the unit, i.e., you are back to ‘stock.’  If I was doing a full day on the superslab (heaven forbid) I might do that to extend the per-tank distance capability.

Thanks for giving such in-depth coverage to the GT1000.  As a fellow GT owner I reference your site often.”

From “J.M.” (10/08):  “I just got the Fat Duc and thanks to your excellent pics, installation was accomplished in minutes.  I also have the 14 tooth sprocket with the Euro ECU and (with those improvements only) the bike ran much better than stock but still popped back a lot on the over run.

That has now been completely eliminated and the difference in overall smoothness is very pronounced.  I will give it a good test this weekend but I have to say I already feel it was well it worth the money.  Thanks!”

From “J.C.” (10/08):  Bike: Stock Ducati GT1000 but with accessory clutch master cylinder.  “Well I got it yesterday, and rode the bike to work today (all the way from [Northern Virginia], brrrrr, cold).  I set it to what you have (between 13.2 and 13.5) and it took me < 1 minute to put on (since you nicely already did the tracing part).  Well I can definitely say, it works.

First for the harsh on/off response, it definitely makes a difference.  Not huge, but a difference.  I really noticed it in the stop and go traffic that sit in from Rt. 236 to I-66 on the Beltway. It was a little smoother.

Now, not that it is totally smooth, if, say the stock GT1000 was a 1 and my smooth as silk clutch W650 is a 10, I would say its now a 3.  So to me that combined with the new (hydraulic clutch master cylinder and lever) make it much more manageable.  Still no where as nice as the (Kawasaki) W650, but the total stock clutch was unusable in traffic, now it’s a bit easier and a bit smoother.

But the other funny thing was I was now riding at 60-70mph in 6th gear and it felt ‘right’.  Before I would have to be going >75 to even put it in 6th and have it feel right, but now I can do the interstate in 6th.  Not really sure if it affects the feel of the other gears, I didn’t notice any other shifting differences, but it nice to have a useful 6th gear.  Not really sure how this works as the gearing is not changed?!?

So I assume the downside to this is that I probably have lost a little power and maybe top speed?  If so I don’t care, this bike had 3x the power of any I have ever had and I am not racing it, and for top speed, if it is down it will still be much higher then I will ever take the bike!  Also don’t really care if it might hurt gas mileage a bit.

Overall, a definite keeper.  For $80 (and the easiest install of an upgrade ever), certainly makes enough of a difference to be worth the money.  I probably will play with the settings some to see what difference it makes and if it can get better, will tell you if I find anything different.”

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