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post #1 of 4 (permalink) Old Jul 23rd, 2009, 1:35 am Thread Starter
 
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Fuel injector firing sequence

Morning,

I have a K1200 RS 2001 and the fuel economy suddenly dropped from 45 down to 25, the plugs and exhaust are totally carboned up.

I removed the fuel rail and injectors believing an injector may have failed and could be stuck open but when I cranked the engine I found all the injectors are firing at the same time. Is this correct?

Thanks

Chris
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post #2 of 4 (permalink) Old Jul 23rd, 2009, 1:44 pm
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That is absolutely correct Sir!

Our efi system is called Bosch multi-point injection which is very simple - all injectors fire at the same time. There is only one driver transistor for all 4 injectors wired in parallel.

Better engineering is sequential injection where the injectors would fire 1,3,4,2.

Multi point injection sounds fancy, but basically every rev. the injectors bang a squirt into the inlet tracts and the fuel timing into the cylinders occurs when the valve opens.

At high rpm there's little to choose between simple multi-port and more complex sequential.

At lower rpms, sequential wins on fuel efficiency and emissions because the atomised injection spray is not hanging about with its fuel globules getting joined up waiting for an inlet valve to open.

A lot of jap bikes and newer Hardlys have sequential fuel injection. To implement sequential injection timing you have to have a crankshaft position sensor. I added a Hall sensor to my KRS when I pulled it apart so I could experiment with sequential firing but it would need some clever electronics sitting between BMW's ECU and the injectors to sync the timing and shorten the injector timing pulse. I just haven't had the time to do that.

Your problem is most likely the O2 sensor, the engine temperature sensor, or a TPS issue. It's far easier to pay for 1/2 hour BMW diagnostics and let them tell you what's not working than hunt for the problem yourself.



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post #3 of 4 (permalink) Old Jul 25th, 2009, 3:54 pm Thread Starter
 
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Thanks for the reply. I shall try the O2 sensor first. I have replaced it before with an aftermarket 4 wire version. Is there an aftermarket Bosch / NTK sensor you could recomend? The BMW one is so expensive.

Thanks

Chris
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post #4 of 4 (permalink) Old Jul 27th, 2009, 6:20 am
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Quote:
Originally Posted by chris
Thanks for the reply. I shall try the O2 sensor first. I have replaced it before with an aftermarket 4 wire version. Is there an aftermarket Bosch / NTK sensor you could recomend? The BMW one is so expensive.

Thanks

Chris
Trot along to your nearest Bosch auto electrical stockist. For my '97, the oem Bosch part is LSH25 0 258.003.854. They will tell you they could probably order the oem Bosch part with the 'special' BMW connector, but it would be on a 6 month back order to the factory (???)

They will tell you their cross reference to the Bosch 'Universal' sensor is a Bosch LS05.

You have to cut the old lead and recover the special 'proprietary' BMW "we make it different to cost you more connector"

Don't bother with the universal plastic splicing kit Bosch supply, it just makes for a bulky untidy splice where space is confined.

You must NOT solder the new to old wires!

Go get 4 small red electrical crimps and some black heatshrink sleeve (2 sizes) to go over the crimps then sleave all 4 in the bundle.

You end up with something that looks neat, nearly like oem but with a slight bulge in the harness. I changed mine about 3 years ago and it's been fine. I seemed to survive the bad gas from Asda et al that knocked out sensors and CATs in many vehicles in the South East.



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