Bosch Injector Spray Pattern

[YoungEngineer]

The stock K1100 injectors seem to have a very narrow spray pattern. Almost like a jet from a water pistol. I've had them cleaned not long ago but only noticed the spray pattern recently after I removed them whilst still connected to the rail. Most injectors I have seen in operation have a mist like spray which I would assume would provide much better atomization of the fuel.


Has anyone had a similar experience? Is this normal behavior of these injectors?

[Laitch]

Almost like a jet from a water pistol.

How does the stream appearance differ from a water pistol, YE? If the bike is running and accelerating ok, don't worry about it. You aren't about to get good mileage in London with your bike regardless. Covet not your neighbor's spray pattern. Seen this?

[YoungEngineer]

I'm on a mileage quest right now. It's becoming quite the obsession but I still don't feel like I'm getting the mileage I should be from the bike despite all my tweeks. I've been driving through France for the past week without any traffic and can't seem to get more then 47MPG Imperial. That's on straight roads at 80mph. I read about Americans getting 45mpg US or 55MPG imperial all the time. So something must be wrong. Could it be that the US built K bikes which I believe have a Lambda sensor rather then a Manually adjusted Co pot run leaner?

The video you showed me shows a very different spray to mine, very powerful and broad spray pattern.

[YoungEngineer]

Here's a video of my injectors in action.

[The Mighty Gryphon]

Your spray pattern doesn't really look that abnormal.  I have seen videos of other bricks with injector patterns similar to yours.  Have you checked the fuel pressure in the rail?   HAve you replaced the filters in the injectors themselves?  If they are dirty and causing some pressure drop I would expect that to have some bearing on atomization of the fuel as well.

As far as your mileage, when I am touring I have found that it is quite dependent on speed and driving conditions.  The best mileage I have gotten is when cruising at a steady 110kph, one up no luggage on level ground.  Higher altitudes, lower temperatures, higher speed, headwinds, and a full load of luggage will all reduce mileage as will time spent idling in traffic.  When touring, I usually get an average over the trip of 38 to 40 mpg(US).  I have gotten as low as 35mpg.  These numbers are for my K75RT.  My K100RS4v which is similar to your K1100 has averaged about 2 mpg better mileage in similar conditions, ie. about 40 mpg when touring.

[YoungEngineer]

I never really ride under 130Km/h or 80Mph and without luggage I suppose that could effect mileage as you have mentioned. It is also very cold here now, sometimes 0C in the mornings.  Your mileage figures are similar to mine which is reassuring but I am still not happy with the spray pattern from the injectors.


I think you may be right about the fuel pressure as it seems that all the injectors are performing in a similar manner. I have no way to check fuel pressure at the rail but I believe that the flow rate is good just from what I can see returning to the tank from the rail although I don't think this has any bearing on pressure.


Internal filters in the injectors? That is something I must check.

[YoungEngineer]

I've just noticed that my injector spray patterns look exactly like the ones in this video at 2:52





Pencil like spray.

[Laitch]

I've just noticed that my injector spray patterns look exactly like the ones in this video at 2:52

Your observation doesn't make sense to me, YE. Each injector in the video has a different spray volume. Would you clarify?

It is doubtful your K1100 will exceed 47mpg unless you are light on the throttle through the gears and cruise at 65mph or under.

[YoungEngineer]

What does YE mean? As for the spray pattern what I mean is that all the injectors spray a fine jet rather then a mist. As you can see from my video they are all equal so I don't think there are any issues. I suppose this is just how they are just an observation.

[Laitch]

What does YE mean? As for the spray pattern what I mean is that all the injectors spray a fine jet rather then a mist. As you can see from my video they are all equal so I don't think there are any issues. I suppose this is just how they are just an observation.

Great! A light touch on the throttle will improve your mileage to the greatest extent possible, all other systems being in good shape.

[kris]

YE, this refers to your handle "Young Engineer". As for my mileage observations my '86 K100 RT with 61,000+ miles on the clock returns about 55 MPIG (Imperial gallon = 4.54 liters). This comes with one-up riding, relatively flat surfaces, reasonable throttle (the only person I want to impress while riding my bikes is me) and in the 70 degrees Fahrenheit range. I was surprised to get this mileage. My '04 Kawi Concours gets only 45 MPIG under the same conditions. She has only 25,000 miles on the clock. That's a pretty substantial difference between injection and carburation. I love them both, regardless!


Happy trails!

[The Mighty Gryphon]

If I was running my K75 under your riding conditions I would expect something in the 36-38 mpg range.   The only time I get anywhere close to 45mpg with any of my bricks is when I am commuting 50 miles one way at a steady 65mph on the expressways with little or no headwind. 

I would not be overly concerned about spray pattern.  Atomization will occur when the stream impacts the hot walls of the intake manifold passages in the highly turbulent airflow downstream of the throttle butterflies.  There is more than enough energy in the stream to accomplish effective atomization.  As long as the bike's performance is there(and it certainly sounds like it is) and the plugs aren't loading up with carbon I would let sleeping dogs lie with respect to the injectors. 

Forget your spray patterns and enjoy your trip on an exceptional machine.

[YoungEngineer]

YE, this refers to your handle "Young Engineer". As for my mileage observations my '86 K100 RT with 61,000+ miles on the clock returns about 55 MPIG (Imperial gallon = 4.54 liters). This comes with one-up riding, relatively flat surfaces, reasonable throttle (the only person I want to impress while riding my bikes is me) and in the 70 degrees Fahrenheit range. I was surprised to get this mileage. My '04 Kawi Concours gets only 45 MPIG under the same conditions. She has only 25,000 miles on the clock. That's a pretty substantial difference between injection and carburation. I love them both, regardless!


Happy trails!

I should have guessed, I thought YE was some technical acronym. 4.5L per 100K is really good. Similar In fact to my previous bike a 1999 Triumph Sprint st 955i. I think I am still chasing impossible mileage, I just miss the days of 220-240 miles to a tank. My light is on at 150 miles on the K :(

[YoungEngineer]

If I was running my K75 under your riding conditions I would expect something in the 36-38 mpg range.   The only time I get anywhere close to 45mpg with any of my bricks is when I am commuting 50 miles one way at a steady 65mph on the expressways with little or no headwind. 

I would not be overly concerned about spray pattern.  Atomization will occur when the stream impacts the hot walls of the intake manifold passages in the highly turbulent airflow downstream of the throttle butterflies.  There is more than enough energy in the stream to accomplish effective atomization.  As long as the bike's performance is there(and it certainly sounds like it is) and the plugs aren't loading up with carbon I would let sleeping dogs lie with respect to the injectors. 

Forget your spray patterns and enjoy your trip on an exceptional machine.

Good to know thanks for the reassurement.

[F14CRAZY]

My average with doing mostly 75-80 mph highway, with side cases and 35L top case, and Pichler V1 fairing, is 39-41 mpg. As low as like 36, as high as 47 mpg with varying cruising speeds

[kris]

YE, just a small caution. Check Martin's postings for information regarding grounding your spark plug leads while cranking the engine. Without grounding you could end up doing some damage to ignition components by way of a built-up charge.