KTM 500 - Less is more?

[DirtJack]

Originally Posted by neduro

3) The fuel injectors are inconsistent. To get the smaller bikes to start easily at elevation, they have to mess with the mapping, and they found they required different settings on different specimens of the same model. They started swapping parts and found that the fuel injector is the cause.

Ned, here's a link (from the 990 TuneECU thread) by a well known tuner which sheds some light on this point.

http://www.advrider.com/forums/showp...postcount=1009

Oops, should have checked the link in Power-Tripp's post (it's no longer working). Here's another post to another forum (which also has the same broken link), but he explains the problem in a little more detail.

http://www.r3owners.net/rocket-perfo...tml#post114748

Finally found the column at another location:

EFI 102: The injector industry’s dirty little secrets

Throughout 2011, this column has covered some of the technical details of engine operation and support systems such as fuel, oil, cooling, the basics of engine management, etc. Now for 2012, it is time to dive into the things that we need to know to make the engine operate efficiently and perform best. With nearly all motorcycles coming off the showroom floor with fuel injection and electronic engine management, the days of carburetors are quickly com- ing to a close. Sad, but true. As a result, we need to become knowledgeable on the detailed parts that make electronic engine management work, and the first and foremost is the injector. Even though this is a subject on wet flow, the topic tends to be a fairly dry discussion. We will try to cut it down to its most basic parts.

A fuel injector is an electric solenoid. This means that it is a valve that uses an electromagnetic coil to open and allow fuel to fuel flow through it. In the simplest terms, an injector is nothing more than a tube that flows fuel from one end to the other. Inside the tube is a spring loaded shaft with a tapered end that fits tightly into a seat cut into the outlet end of the injector. An electric coil on the outside of the tube lifts the shaft off the seat and opens the injector when electricity flows into the coil. The spring pushes the shaft down against the seat as soon as electricity is turned off. This stops fuel flow. The amount of time that the injector coil is turned on is termed the injector pulse unit (IJPU) and can be measured in the percentage of on-time versus off-time – called duty-cycle. A 10 percent duty-cycle means that the injector is only turned on 10% of the time. And a 100% duty-cycle means that the injector is open all of the time.

Inside the ECU module are coil drivers that send the electric current to the injectors. These drivers and injector coils heat up when they flow current through them, as a result, the ECU software tends to shut them down when they exceed 85-87% duty-cycle to prevent heat damage to the drivers and injectors as well as the rest of the ECU. This sets the limit of useable flow for a given injector at a specific fuel pressure. As the injectors wear, and are exposed to operational heat from the engine and the injector coil itself, the flow changes at a specific duty-cycle.

If you take a set of brand new injectors out of the box and flow test them at 100% duty cycle, even production new injectors tend to all flow within 1-1.5% of each other. [WOW! A matched set right out of the box! Lucky me... yeah, RIGHT! Guess what... they all do that. No need to send them out for matching, the manufacturer has already done it for you at 100% duty-cycle. But this doesn’t mean much.]

At 100% is where most OEM and aftermarket injector companies tend to test and match injectors into sets. But as we have seen, the ECU cannot operate at 100% duty cycle without damage to the drivers or injectors over time. So why anyone would care about flow at 100% duty cycle is anyone’s guess. The fact that most injectors are flow tested with “test fluid” instead of actual fuel, and most use mineral spirits as their “test fluid” only makes things worse. Mineral spirits have a different density and viscosity than pump gas that results a 13% difference in actual flow. Race fuels vary even more, and the spray pattern with mineral spirits is different from that with fuels. Only a few select companies will actually test fuel injectors throughout their duty- cycle range (dynamic range testing) and match them up in sets for flow and spray pattern with specific fuel pressures, voltages, and fuel types.

[Some high flow injectors purchased from aftermarket suppliers are nothing more than stock injectors that have been taken apart and given a whack on the pintle shaft with a pin punch and large mallet to make them open further and flow more. Sad, but true.]

Since the injector is a mass produced part, it has certain production tolerances for the valve, valve seat, and the coil itself. So even though the injector is rated for a given amount of flow at a set pressure, this varies a bit more than many realize at less than 100% duty-cycle. Most OEM injectors have 25% to 40% overhead at 85% duty-cycle. This means they flow considerably more fuel than the engine can use in stock trim. This causes the engine to actu- ally operate at low duty-cycles, even at wide open throttle, at peak rpm. At low rpm and loads where we cruise, the duty-cycle percentage is very small. As a result of variations in electronic slew rate and electric lag time of the injector coil and driver (the amount of time it takes the injector to open fully), and the variances in machining tolerances of the needle and seat inside the injector, we now have more and more variation in how much a specific injec- tor flows at smaller duty cycles. Injector flow variations of 7%-14% are common, and as much as 30%-40% are not uncommon at cruise duty-cycles. [If the electrical system voltage changes due to charging, regulator, wiring, or battery issues, the injector flow changes. Less voltage means it takes longer for the injector to open, and the lag time takes up more of the injector on-time. The fuel pump produces varying pressures that alter injector flow, as well. Something to think about.]

What does this all mean to the average motorcycle rider? Well, it means that the manufacturer pays an individual to spend a lot of time and effort developing a factory calibration for each specific model using injectors that are flow matched throughout their duty-cycle range, to meet output, opera- tion, noise, and gas emission goals (among others). THEN, the stock calibration is offset for variations in fuels and injectors, as well as other variations throughout the world. This means that if we take 10 different bikes of the same make model and year, and test them at different engine speeds and loads, we get a wide range of results. This is on completely stock engines. If it were not for the stock narrow-band Lambda sensor (exhaust gas oxygen sensor), that the ECU uses to sense fueling at idle and cruise conditions, and to make offsets to the factory mapping or calibrations, most stock bikes would have rideability issues far from acceptable. In fact, many stock bikes are not even truly acceptable due to having to meet strict emission, mileage, and noise standards.

As we change the air flow into and out of the engine with aftermarket air filters, intake kits, headers, silencers, and more, the engine wants specific changes to fueling and ignition timing for best output, fuel consumption, and changes to throttle input (transient response). The good thing is that we can make these changes and give the engine what it wants, because we are not limited by the OEM constraints. If we know how to listen to what the engine is telling us, it will tell us what it wants and needs... all we have to do is listen carefully. Give the engine what it wants, not what you think it wants. The result in performance, transient response, fuel consumption, smooth operation, engine life, and more, are well worth taking the time to listen.
Isn’t it amazing how important injectors are to the operation of your engine?

Time to go, there is fuel to burn, tires to wear, and roads that are calling my name in the wind. I might even get a chance to try these new inexpensive grip heaters that Santa left in my stocking.

By Wayne Tripp
Power-Tripp Performance, Inc. www.Power-Tripp.com

[team ftb]

Dirtjack - Thanks for taking the time to get that post together. Hugely beneficial to nonces like myself grappling the task of understanding FI and its complexities. Articles like the above that break it down in a simplistic manner are truly a boon for us simpletons.

Thank you.

So where is the next article to continue the education?

[neduro]

Originally Posted by team ftb

Dirtjack - Thanks for taking the time to get that post together.

+1

As an acknowledged luddite, it feels a bit like being handed a box of unlabeled jets and told to sort it out yourself.

[DYNOBOB]

Interested to hear what happens to your fuel consumption...


.

[DirtJack]

Originally Posted by DYNOBOB

Interested to hear what happens to your fuel consumption...


.

+1

Right now Viola-tor and I are working on a 990 sudden MPG decrease (to mid 20's) on his bike.



My bike (background) is a doner bike (ECU, throttle bodies, etc.). We are also doing other maintenance while the bikes are apart. See:

http://advrider.com/forums/showthread.php?t=772404

Sorry for the hijack, now back to the thread.

[Foot dragger]

Im curious about the mileage thing as well,cant get far on 15mpg in the woods. I bet the new injector fixes it.

[unaweep]

Originally Posted by neduro

snip
So, the operating theory is that my fuel injector was sticking open, dribbling fuel when it should not have been, and thus giving me terrible mileage. I swapped it for the one I'd had in the airbox, but weather and work have prevented me riding it.

I
News to follow when I get to ride it.

Ned- what are you carrying in the airbox? The "Fuel Rail CPL" or the "Injector Kit CPL" the whole throttle body or some combo?

In light of the price diff, I though about just buying the whole throttle body. Have a problem, pop one off and the other on. Sort it at camp.

[jesusgatos]

Spare throttle body? eek.

[unaweep]

Originally Posted by jesusgatos

Spare throttle body? eek.

I know. But, I have two 500s (one for me and one for my brother) and the thought of trying to get the bike out of a place like 5 Miles of Hell, or worse, because I didn't have a part for the throttle body is even more eek!

[neduro]

Originally Posted by unaweep

Ned- what are you carrying in the airbox?

I have 75041023144 (Injector Kit Cpl) + all the O-rings in the system + the clamps running to the fuel line + a spare one of the larger inline filters that everyone was all wound up about last year when the FI bikes came out.

The only issues I've seen with running have been when the injector clogged and quit firing fuel. I heard about someone who made an adapter so that their CO2 tire inflator could push CO2 thru the injector backwards and clean it out, but I thought it was simpler just to carry the injector complete.

There are some good youtube videos of cleaning the injectors, worth watching on a boring day so that you know what you're aiming for if you ever have to clean one.

[Foot dragger]

Originally Posted by unaweep

I know. But, I have two 500s (one for me and one for my brother) and the thought of trying to get the bike out of a place like 5 Miles of Hell, or worse, because I didn't have a part for the throttle body is even more eek!

Maybe somebody will have carburetor retro fit kits....................?

Just kidding and being a smartass as usual,pay no attention.

[Hair]

Originally Posted by neduro

A brief update on my 500.

As a starting point, I love the chassis and the power. From a performance standpoint, it works really well out of the box, I haven't changed a thing, the only thing I can see myself doing is adding a bit of oil to the forks to help hold them up deep in the stroke. They are great on trail chop but a little soft when whoops come around.

However, I'm still getting lousy mileage. Out dry at 53 miles last week. So, I called KTM of Aspen (best shop in the world) and their analysis, based on extensive experimentation, is as follows.

1) None of the sensors can cause bad mileage. They will throw lights, but the bike will run just the same or not at all.

2) The TPS is the only one that can create a strange running condition- if it is way far out of whack, the bike will hesitate and stumble. But, that's at one extreme of the range- with it anywhere in the middle the bikes seem to run fine.

3) The fuel injectors are inconsistent. To get the smaller bikes to start easily at elevation, they have to mess with the mapping, and they found they required different settings on different specimens of the same model. They started swapping parts and found that the fuel injector is the cause.

So, the operating theory is that my fuel injector was sticking open, dribbling fuel when it should not have been, and thus giving me terrible mileage. I swapped it for the one I'd had in the airbox, but weather and work have prevented me riding it.

I think the useful takeaway point for anyone out there trying to tune one of these, is that the sensors are not likely the culprit.

News to follow when I get to ride it.

Having FI doesn't equate to better mileage. The mileage on the 570 was really low. Maybe 30 to 33 mpg. And even the 390 wasn't all that good. I don't think that bike ever got close to the mileage that the 525 or the 530 would make.

I have not read this whole post. But some of the riders on this site have benefited from the OEMs by posting (boasting) about recent product. Not that it's a bad thing to do that. But I think that it should be stated upfront in the thread.

[woodzrider]

Originally Posted by c.vestal

This winter I plan to make it more long distance oriented.
Taller gearing. around 14/45. This motor has the guts to make this work.
Rally Moto Kit frames are cut and I am trying to get the time to fit them on.

Have you had a chance to try tha taller gearing? I am thinking of up/gearing but not quite that high. (maybe a 14/49or48).

[Johnnyktm]

[Johnnyktm]

Originally Posted by neduro

What are others out there seeing for fuel economy?

Mine is stone stock, right down to the pipe, and my most recent ride was in deep sand. I expected bad mileage, but it got barely 15 mpg, which doesn't seem right. I'm mystified that it seems to get substantially worse mileage than my carbed bike, especially when the 450 I demoed was so far on the other end of the spectrum.

Thanks Neduro and all here at the forum for the great information about this incredible bike, and about mileage, I recently purchased a used 2012 EXC 500 and I'm getting around 47mpg without racing it. The bike is stock, with a 13/50 gearing: