BMW K bikes (Bricks)


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1Back to top Go down   New engine management for K-bikes Empty New engine management for K-bikes Mon Nov 18, 2024 6:22 pm

flying finn & brick

flying finn & brick
active member
active member
Hello. I would like to hear your thought on this one!

I am doing a project with my -91 K75 where I replace the old Bosch L-Jetronic ECU from my bike. The end-result will be modern closed-loop engine control for the fuel injection.

Much like discussed here:
http://www.motobrick.com/index.php?topic=936.75
https://www.motobrick.com/index.php?topic=9303.0

As I have been planning the project, I can see that the swap could be done almost plug'n'play with using the original wiring loom and original connectors. Biggest changes would be installing a wide-band lambda sensor and maybe getting rid of the MAF sensor since it reduces power by reducing airflow.

Do you think there could be others interested in upgrading their fuel system? The benefits should include: 
- better fuel economy 
- more torque/power
- much better throttle response
- no hassle with adjusting the old system with exhaust CO analyzer (how many even does this properly?)
- no longer dependent on 30yo tech and used parts...

and all this up to you to control with stand alone ECU, if you want to dive into it. (there should be some base maps to use)
The unit could also control the blinkers and support some retrofitted dash. (my blinker unit is done Surprised )
What do you think?


I am aiming to run my machine on E85 but for most I guess the refit could cost around 600€ (in EU with VAT) in a package that would include all wiring, connectors and sensors. The price on these components have become quite attractive in recent years. Possibility to also control the ignition should be considered as here it is left to the original ignition controller.

Edit: My point is to get an idea if its worth trying to put together this type pnp kit. The whole thing would be much easier as one-off, without full pnp readiness but I might look into it if it has some demand as such.

    

jbt

jbt
Life time member
Life time member
About the results you can reasonably expect,  the only eventual gain would be about fuel economy, maybe emissions, but nothing that a fine tuning of the OEM equipment could give you. 
But no gains of power or torque. At all. A modern fuel injection does not gives by magic an engine extra power: it allows to avoid losing power only once you made mecanichal mods that do effectively improve power: rebore cylinder, longer opening cams, high compression pistons, bigger valves, low friction materials, etc.
The MAF does not reduce power nor airflow. The K75 has the exact same capacity/power ratio than the K1, running with Motronic so without MAF: 100HP/L.
The MAF could, theoretically, be restrictive, but only  at full charge, full rev...if the design of the intake pipes and the cylinder head were not much more restrictive than the MAF. In other words: when a meatball is stuck in your trachea, spitting out your denture won't improve your breatingh.
The basics of the architecture of a K75 are preventing this engine to deliver more power at high revs: it's a long stroke 2v engine, excellent for low rev torque and smoothness, but unsuitable for revving. You can worry about the MAF restrictive effect above 12000 rpm. Reach them first.
The Jetronic injection also appears to be a simple but extremely reliable system 40 years later, with components available anywhere on the planet for very cheap money, and that you can diagnose with a simple volt/ohm meter. Any modern injection system requires a PC and dedicated software... That's why I chose this model to travel: all the tools and spare parts that could fail fit in the seat boot.

Furthermore, if you want to run E85, so you will first have to deal with the absolute incompatibility of all the components of the fuel injection with it; fuel pump rubber, fuel hoses, gaskets. See your avatar pic! You will also have to increase the fuel flow by 25% and pressure to compensate the poor energy of E85, so to change the fuel pressure regulator, the injectors, potentially the fuel pump and, of course, create a specific map, with a power bench to validate it.

I've been talking with some people who had prepared K75 and K100 engines for race: You could reach +5% extra power with a real state of the art preparation (not stacking up so-called perf parts), but it will be a 5 number bill. 10000$ to go from 75 to 79 HP. Rolling Eyes

So try implementing your new system, I'm curious about this project!
But don't expect much about it. Making it run as well as a Jetronic will already be a success.


__________________________________________________
Let us enjoy the transient delight
That fills our fairest day.
    

Rolf E

Rolf E
Silver member
Silver member
Well said jbt. I fully agree. Keep it simple and standard.

https://www.teuntin.co.za
    

4Back to top Go down   New engine management for K-bikes Empty Re: New engine management for K-bikes Tue Nov 19, 2024 11:32 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
I agree with all that JBT wrote.  As it is, the K75 engine is amazingly reliable, smooth, powerful and pleasant to live with with the stock Jetronic engine system.

However, a Megasquirt retrofit would give some mental entertainment during the long Finnish winter.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

5Back to top Go down   New engine management for K-bikes Empty Re: New engine management for K-bikes Tue Nov 19, 2024 12:14 pm

Laitch

Laitch
Life time member
Life time member
Point-Seven-five wrote:I agree with all that JBT wrote.

However, a Megasquirt retrofit would give some mental entertainment during the long Finnish winter.
I agree with JBT, too. Once I find something good, I try to preserve it, not alter it. Partially, that's because I'm not industrious but also it's because I'm appreciative. Smile

Here's the summary of the Megasquirt outcome, The experimenter and writer is probably now involved in his career as a physician and I hope is still enjoying his elderly Moto Guzzi California.


__________________________________________________
1995 K75 90,000 miles
    

92KK 84WW Olaf

avatar
Life time member
Life time member
I like to travel a bit too and the comment about spare parts fitting in under the seat is so correct. Any others are also very easily available and its really hard to beat that.

I did put E85 in my K one time in France.....the comment about increasing fuel pressure and higher flow...... swap the fuel pressure regulator to K1100.......also swap the injectors to K1100 and voila. I am going to try that some time. I moved the FPR on my K100 Sprint because the fairing doesn't have a removable panel to get at it. Now its accessible, along with the injectors, without removing any plastics.....


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 51,800 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

Ringfad

Ringfad
Life time member
Life time member
I agree with the previous comments but did see this setup fitted to a k1 that was only used for the track.

BSK SpeedWorks - BMW K Series Engine Management Package


__________________________________________________
New engine management for K-bikes Ir-log10

 ;BMW; K1 Black 1993 60K Km     ;BMW;  K1100RS Black 1996       ;BMW; K1 Blue 1990 25K Miles

 ;BMW; K1200RS Red
    

Two Wheels Better

Two Wheels Better
Moderator
Moderator
Ringfad wrote:I agree with the previous comments but did see this setup fitted to a k1 that was only used for the track.

BSK SpeedWorks - BMW K Series Engine Management Package
Sold now only by KPartsHolland for a mere US$1767.91 or 1999.99 which I imagine includes VAT. See the link within BSK's website. Imagine how many tanks of petrol that'll give you running the stock reliable system. If money is not an object it would be an interesting experiment. I briefly (very briefly) considered it when I was putting Big Block together back in 2014/15. In the end I simply used the later Motronic for K1100 w/o the grey box ignition amplifier ('94 on) but with O2 sensor.

Long memories may recall the British school boy who was/is a Forum member and who built his own FI system as a class project on a K100 here several years ago. I have not been able to locate that interesting thread in our search engine after a relatively minor search.

But, file under "There's Nothing New Under The Sun" HERE is a link to yet another Forum member who worked out his own (Microsquirt/Motogadget) system(s) for injection and a reduction in the wiring loom/relays. Sadly, no conclusion or follow ups as to its efficacy down the road.


__________________________________________________
The forest was shrinking, but the trees kept voting for the axe, for the axe was clever, and convinced the trees that because his handle was made of wood, he was one of them. -Turkish proverb
1977 R75/7-100, '93 K11/K12 Big Block, '93 K1100RS, '95 R100 Mystic, '96 K1100RS, 2 x '98 K1200RS, '06 K1200R & '09 K1300GT
    

tinyspuds

tinyspuds
Life time member
Life time member
Two Wheels Better wrote:
Long memories may recall the British school boy who was/is a Forum member and who built his own FI system as a class project on a K100 here several years ago. I have not been able to locate that interesting thread in our search engine after a relatively minor search.

Maybe  @DBRMN?


__________________________________________________
1985 BMW K100RT + Hedingham HUB and LL’s. VIN 0028106.
1986 K100RS in boxes. VIN 0141918.
1954 Royal Enfield 350 Bullet. Original.
2000 Hayabusa with Charnwood chair, Wasp forks and EZS wheels.
    

10Back to top Go down   New engine management for K-bikes Empty Re: New engine management for K-bikes Fri Nov 22, 2024 11:16 am

Two Wheels Better

Two Wheels Better
Moderator
Moderator
tinyspuds wrote:
Two Wheels Better wrote:
Long memories may recall the British school boy who was/is a Forum member and who built his own FI system as a class project on a K100 here several years ago. I have not been able to locate that interesting thread in our search engine after a relatively minor search.

Maybe  @DBRMN?
Yes, but after a re-read I am mistaken. It's not a full FI re-design, just another cafe bike, albeit, with some creative custom edits, and by a talented youngster. Incomplete, as it reads.


__________________________________________________
The forest was shrinking, but the trees kept voting for the axe, for the axe was clever, and convinced the trees that because his handle was made of wood, he was one of them. -Turkish proverb
1977 R75/7-100, '93 K11/K12 Big Block, '93 K1100RS, '95 R100 Mystic, '96 K1100RS, 2 x '98 K1200RS, '06 K1200R & '09 K1300GT
    

11Back to top Go down   New engine management for K-bikes Empty Re: New engine management for K-bikes Fri Nov 22, 2024 1:42 pm

tinyspuds

tinyspuds
Life time member
Life time member
Two Wheels Better wrote:

Maybe  @DBRMN?
Yes, but after a re-read I am mistaken. It's not a full FI re-design, just another cafe bike, albeit, with some creative custom edits, and by a talented youngster. Incomplete, as it reads.
Yeah, but in ten years he will have invented the next generation of Fuel Management Systems  lol!


__________________________________________________
1985 BMW K100RT + Hedingham HUB and LL’s. VIN 0028106.
1986 K100RS in boxes. VIN 0141918.
1954 Royal Enfield 350 Bullet. Original.
2000 Hayabusa with Charnwood chair, Wasp forks and EZS wheels.
    

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