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Discussion Starter · #1 ·
The 1998 ST2 that I have came with a UltiMap UM 161 installed. I have the original Chip that is marked St2 USA 067U. Someone recently told me that my bike would run much better with the original chip installed.

I know next to nothing about the subject so I thought I'd ask here.

I guess 'running better' leaves a lot of questions. I'm not looking for better gas mileage, just the best running bike I can have. I live at 6,000 feet and my bike runs like crap up here compared to sea level. Not only is the 3,900 rpm stumble terrible at altitude but just overall it's unreal how nice the bike is at sea level.

Anyway, someone mentioned that my bike runs to lean and that I should swap back the original chip.

I should also note that I have gianelli pipes.


thanks.
 

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Most likely if you have the um161 chip installed you're running richer now than you would be if you reinstalled the stock chip. And being at altitude it will run leaner due to less O2 molecules. Hence why it runs better at lower altitude.
You could try trimming the pot to see what kind of results you obtain in your area; LH rich and RH lean. Be very careful to note when you have reached the limits as you can damage the pot if forced beyond its travel.
Good luck.
 

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Discussion Starter · #3 ·
Er, um yeah... You are speaking greek to me...

You could try trimming the pot to see what kind of results you obtain in your area; LH rich and RH lean. Be very careful to note when you have reached the limits as you can damage the pot if forced beyond its travel.
 

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If you know which chip you have then I thought you knew about the potentiometer in the ecu you can adjust for fuel flow. My bad. Have a look in the ecu with the rubber plug removed. You will see a square device next to the chip with a very small slot for a jewelers size screwdriver. Turn the screw ccw for rich and cw for lean. A small adjustment may help alot.
 

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less o2 would make for a rich condition? the carb guys let more air in as they go up, usually by opening the air box.
 

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The FIM chip is about the best chip out there to put in your ST , from what I have heard. I have no experience with other chips. You can have the stock chip flashed at a dealer to try to correct your problem. I purchased the 161 for my 98 ST and like the performance.There is a sensor that feeds air temp and barometric pressure to the ecu, I wonder if changing that would help?
 

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lets try the simple stuff first. when did you last change the spark plugs and are they standard plugs or iridium and at what gap? how many miles on the airfliter? these are all easy and inexpensive to replace and will give you a firm foundation for further troubleshooting.
edit; when was the last valve check/adjustment that you have had done or have firm documentation on.
 

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less o2 would make for a rich condition? the carb guys let more air in as they go up, usually by opening the air box.
Just to clarify what I meant about the lean at higher altitude. I was referring to the fuel injection system being temperature and density compensating thereby less fuel at less density unlike a carb that is not conpensated for density and would be RICH at altitude.
 

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the st2 fi seems to have a narrow window for compensating since the system requires a chip change for a different exhaust. hard to say if it is over compensating for lack of o2 which would be a large swing in the add air direction or can not make the large change required and is rich. given the narrow band available it could very well be outside the adjustment range.
 

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Old Wizard
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Less Air Plus Less Fuel Equals Less Power.

The UltiMap UM 161 chip programming is the result of many hours on a dyno and represents the optimum fuel and ignition set-up for a PROPERLY TUNED ST2. It will produce more power and better throttle response than your stock Ducati chip at any altitude. Period.

Since your bike runs properly at sea level then you should assume that its basic tune is correct, that is, the throttle position sensor, the throttle body balance and idle adjustment are all correct. This also suggests that your ignition system components are OK and fuel injector nozzles are spraying correctly.

The truth is that EVERY bike will produce less power and poorer throttle response at higher altitudes than at sea level. There's less oxygen in the air so the computer supplies less fuel to compensate. This fuel reduction happens no matter which chip you use.

Here's some background.


Ducati Engine Management System

Ducati’s engine management is provided by an open-loop fuel injection system that uses a computer to control the opening duration of its injectors based upon voltage levels presented to it from several sensors. The longer the injector is opened, the more fuel is supplied to the engine.

The computer contains a Eprom chip that stores a look-up table of injector durations for 16 throttle positions and 16 engine speeds. This chip can be removed from some computers and replaced with one re-programmed with different durations (fuel map) needed for fuel mixture changes necessitated by engine modifications. The fuel map supplied by Ducati is programmed to provide good fuel economy and to meet exhaust emission standards, so does not really provide optimum performance.

The chip also contains a look-up table of degrees of ignition advance (spark map) for the same 16 throttle positions and 16 engine speeds that are used for the fuel map.

The computer determines throttle position from the voltage level sent from the throttle position sensor (TPS) and determines engine speed from pulses sent from a pick-up coil on the engine that indicates crankshaft RPM.

Unlike a closed-loop system that also samples its exhaust gases to make corrections to fueling, the Ducati system only makes corrections (trim factors) to the base map based upon engine coolant temperature, ambient air pressure (altitude) and temperature.

The coolant temperature sensor (thermocouple) monitors the engine coolant temperature so the computer can supply additional fuel while the engine is warming-up and retard ignition timing if the engine gets too hot.

Engines need more fuel when for a cold start as there is no heat in the ports and chambers to keep the fuel atomized as vapor, so it condenses. Fuel as a liquid burns very badly in the combustion chamber, so throwing more at it ensures enough stays as vapor for some sort of combustion. Injected engines get a very nice fuel spray from the injectors and this is why injected engines behave well when cold.

The atmospheric pressure sensor monitors the air pressure so that the computer can supply additional fuel when you ride at lower elevations where the air is more dense. Conversely, if you ride in the mountains where the air is thinner, the voltage output of the sensor drops, which tells the computer to make a pre-programmed reduction to the fuel map injector durations.

The atmospheric temperature sensor voltage level tells the computer how much to modify the fuel map injector durations for a given air temperature. When you take a ride on a hot day, the air is thinner and consequently will cause an engine that has its air/fuel mixture set correctly for a nominal 68°F day, to run too rich. The sensor's resistance increases with air temperature.

Manufacturing and assembly tolerances plus a range of test allowables means that each bike will be somewhat different than the bike that was first used to develop the base fuel/ignition map for that model. So an adjustment method using a Mathesis tool is provided to allow making an additional trim adjustment over a very limited range to compensate for normal production build variances.

On superbikes that use either the Weber-Marelli IAW 1.5M or 1.6 engine control unit (ECU), the trim is made using a potentiometer located next to the EPROM chip socket inside the ECU. The trimmer adds/subtracts a millisecond or so to each fuel pulse over the entire RPM range. On earlier bikes that use the Weber-Marelli IAW P7 and P8 ECUs the adjustment screw is on the outside of the unit.

Your dealer will make trim adjustments with the help of a exhaust CO analyzer. The factory setting results in 1.5% CO for a stock bike to meet emissions but best power is usually realized when full-throttle CO is in the 4-6% range. In any event, check the color of the inside of your tailpipes after a few hundred miles. They should be medium to dark grey, not black and sooty.
 

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Er, um yeah... You are speaking greek to me...

You could try trimming the pot to see what kind of results you obtain in your area; LH rich and RH lean. Be very careful to note when you have reached the limits as you can damage the pot if forced beyond its travel.
yes be careful when trimming pot it's dangerous and illeagal:eek:
 

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you can change the amount of air entering the system, by opening or closing off the air intake without changing the fuel supply to the injectors as there does not seem to be a sensor on the air intake volume. some duct tape across the intake will make the system richer, removing the snorkels will make the system leaner.you make some easily reversible changes and see if there are any improvements.
 

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Just curious, I know this bike is newer to you and you have had it to a few people, have you (they) sync'd your throttle bodies and adjusted your throttle position sensor yet?
 

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Old Wizard
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Unless you use a turbocharger or supercharger to push more air into the engine, at an altitude of 6,000 feet any engine's power output will be 20% less than it is at sea level. Assuming, of course, that the engine's air/fuel ratio is correct and continuously adjusted by the Engine Management Unit as you ascend and descend the terrain. The trouble is, is that the altitude compensation programmed into the computer isn't going to give you an perfect air/fuel ratio at every elevation.

So, your best solution is to compromise and have the CO trimmer adjusted by your dealer while you're at 6,000 ft, not sea level. This will minimize any misfires caused by a too rich condition and give you better throttle response. Not more power mind you, but it should make the engine accept throttle inputs more smoothly.
 

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I am still curious about the barometric sensor and whether that is functionally sound. That is what feeds the input to the cpu for as far as altitude and how to compensate the fuel mixture. I suppose only a mathis tester would be able to determine that. Maybe someone could enlighten me. (no flames needed)
:D
 

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Discussion Starter · #18 ·
Bike is at the shop right now, should have it back in a few days. I can't remember the name of the electronic gizmo my mechanic is going to hook up to my bike but he's going to test it out and see how rich/lean things are set and also check the barometric gauge, etc.. His feeling is that my bike doesn't 'know' what altitude it's at and it's aligning itself accordingly. All beyond my comprehension. I'm a photographer. Ask me about fstops and shutter speeds and we're golden.

I'm hopeful that he gets it running better. Looking forward to it.
 

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Old Wizard
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There's a little more to the story about Ducati's fuel correction for atmospheric pressure.

In order to have the correct stokiometric air/fuel mixture at your 6,000 feet the computer should reduce the amount of fuel at all throttle openings by 14% across-the-board. (See table below)

It doesn't, it reduces it only 6%.

The reason is because if Ducati programmed in the ideal air/fuel ratio for all anticipated altitudes it would need a fuel correction table that has a maximum reduction of 32% at around 13,000 feet.

The reason that Ducati chose to abandon this higher percent fuel reduction factor is because when the atmospheric sensor circuit fails, the computer sees a voltage that tells it that it is at the highest altitude and consequently reduces the fuel by the highest amount, 32%.

Unfortunately the bike runs like crap (if at all) at -32%. So Ducati chose to use a correction table that has a maximum of -8% instead, so at least you can limp home.

So the bottom line here is that at 6,000 feet you're running (14-6) 8% too rich which is at least one of the reasons why it's running badly.
 

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like i said earlier open the air box, it works for carb equipped bikes without the use of a turbo, doesn't cost anything to try except a few minutes of your time and is reversible. you might ask the same questions over on the advrider forum, many of those folks are going up and down and may already have a workable solution.
 
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