Ducati.ms - The Ultimate Ducati Forum banner
  • Hey Everyone! Enter your bike HERE to be a part of this months Bike of the Month Challenge!

1 - 8 of 8 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter · #1 ·
Does anyone see anything in the following screenshot that is a smoking gun for a huge stumble from about 7500-9000 RPM when over about 30% throttle? I'm totally new to this fuel injected motorcycle thing. I'm pretty savvy on jets and needles but this stuff is quite a bit more finicky.

I appreciate the help. The bike is a 2005 749R with larger injectors and 57mm termi system.
 

Attachments

·
Premium Member
Joined
·
5,656 Posts
First thing to know is that's not really your fuel map. It's the fuel table stored in your Power Commander meant to lie to your bike by adding or subtracting injector "on" time after the ECU. It essentially intercepts the trigger to your injectors and adjusts the amount of fuel based on TPS and RPM. Your bike's real fuel map is stored in the ECU.

There was a time when Power Commanders were all we had once Ducati when to small ECUs that didn't let you replace the chip. That time is long gone. You can get maps flashed on your ECU pretty easily these days.

No idea the history of you and that bike in question, but I'll assume it's new to you. Step one. Remove the Power Commander. Run the bike. If you have an improvement, reconnect the PC and load an all zero map. Back to the problem? Ditch the PC and get a good ECU flash to match the bike's set up. Bike still runs good with the PC connected and an all zero map? Find a more suitable map, you can have a custom map made, or ditch the PC and and get a real map for your ECU.

Bike still stumbles with the PC disconnected? Trouble shoot the bike. Could be as simple as a baseline set up.
 

·
Premium Member
Joined
·
876 Posts
The fuel system only cares what is at the end of the line. Fueling correctly with a PC has been done for a long time. You don't need to abandon your set up. It's a whole lot easier than messing with chips. That said, the map is meaningless unless you know the ECU map values.

There are many ways a bike can have a flat spot that have nothing to do with the fuel map. You don't provide any history about the bike other than the map defines some mods. Is this a new symptom or forever been there? Have you messed with the TPS or had it's operation and setting verified? As SS904 says, you can determine if the OC is having a negative or positive effect by disconnecting it or zeroing the map. That's a really good idea because it will help you determine if there is another problem with the bike.

All that say, the minus numbers starting at 7500 are suspicious.

Assuming you are avoiding having a dyno tuner tune the bike, I caution you against guessing. Once you have burned a valve, you are past the tuning stage. An alternative is to use a wide band O2 controller and sensor to make sure you aren't going dangerously lean while you fart around. Make sure you have a mapping capability. Gauges alone are worthless.

The
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #4 ·
Thanks for the warnings guys. I just purchased the bike, stumble and all. I am going through a list of things (verifying ignition system integrity, valve clearance, etc.) and understand that this is only a piece of the puzzle. I understand how the PC works as a piggyback system. I don't currently have a way to peek into the ECU mapping so this is my only way to check fueling. Once I've checked off my list of the basics I'm taking it to a reputable tuner, who I already spoke with, for a ground up mapping session. One of the first things I do with a newly procured carbed bike is see what jets are in it, and see if they make sense (ride it, check spark plug condition, ask buddies with similar setups what they run, etc.). I was hoping to bounce this off you guys in the same way. I know If all I do is richen, there's not much chance of burning stuff up. The stumble feels lean in that it doesn't take any time to clear up, its purely rpm and throttle position related.
 

·
Registered
Joined
·
746 Posts
Get it dyno tuned.

See the curves , AF ratio sorted out.

End of the story.
 

·
Excel Addict
2001 900SSie
Joined
·
5,345 Posts
All that say, the minus numbers starting at 7500 are suspicious.
Actually, it is the opposite in the region where it is stumbling.

Some comments.
Unless the ECU has been remapped, it does not "know" you have bigger (flow?) injectors.
So first up, ignoring the PC, it would be providing more fuel.
Then when you add the PC, it would be expecting stock injectors then adding or subtracting fuel based upon some form of testing I presume for the Termis.

So you may actually be running too rich due to the stock ECU combined with bigger injectors, then the PC adding fuel even more fuel on the expectation of stock injectors.

Personally I am not a fan of the broadbrush fuelling of the PC based upon data logs from a Marelli 5AM where there are 20 throttle break points and 32 RPM breakpoints and the AFR was all over the place, so with such large TP and RPM steps in the PC it would be very coarse fuel corrections.

IMO datalogging and mapping to suit is the way to go.
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #8 ·
Working on the principle that I've never seen a carburetor needle with sharp steps, I "smoothed" the region from 6750 to 7500 above 10% throttle by adding fuel. Now the stumble is gone, but I think I am a tad too rich. It just feels a tiny bit dull. With that range working so much better, I did a number of 3rd gear pulls from 5000 at various throttle positions. That exposed a couple more bugs, but at least its rideable now. After some more tinkering it will be off to the tuner...
 
1 - 8 of 8 Posts
Top