Hi all again

I'm still trying to figure out the whole engine and I didn't get this assembly; it's connect to the cooling circuit.
Thanks for your help,
Joao
Rescued attachment Assembly.jpg

That's the choke. It has coolant running to it and opens/closes the chokes as required.

Steve

Many thanks.
Perfect,
Joao Caldeira

You will need that otherwise it will run like a dog when cold, because the ECU will assume the choke has opened and fuel to suit.

quote:

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Originally posted by ChrisGamlin
You will need that otherwise it will run like a dog when cold, because the ECU will assume the choke has opened and fuel to suit.

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quote:

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Originally posted by G.Man

quote:

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Originally posted by ChrisGamlin
You will need that otherwise it will run like a dog when cold, because the ECU will assume the choke has opened and fuel to suit.

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?????

Ecu adjusts fueling on a carb engine... surely not...

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so if it is EFI .. then why does it need choke?

On a carbed engine the choke also opens the throttle butterflies slightly to let in more air, and I guess thats what this does, so its not acting like a full choke you get on carbs where the choke action also enriches the mixture.

Dont ask me why Yamaha did it this way but its exactly the setup I have on my 2003 engine and that's 100% fuel injected

[Edited on 15/4/06 by ChrisGamlin]

Ok i'm no Genius on bike engines ... but i like to think i know my bit on EFI tuning on cars.

Cris as you very well explained ... I am suspecting that engine does not have an idel speed control valve, so I would gather that Yamaha might have used a simpler and less complicated way of controlling RPM for idle to warm up the block.

It will work kind of like a choke to open up the throttles slightly, hence allowing more air in, and increasing the engine rpm and fuel. On cold engines this will stabilise the running, and warm up the baby, ready for a good thrashing.

This all eliminates the need for an extra PWM channel on the ECU to control an ISCV, thus making the engine, more compact. An ISCV might be small, but the resultant plumbing might have changed things around a bit. Using an already established system from a Carbed engine, makes a lot of sense realy. If it ain't broke, don't fix it.

[Edited on 16/4/06 by clutch_kick]

Ah right Chris, its fuel Injection, I forgot that Yamaha used CV throttle slides on their fuel injection version...

They found it was a better system than motor controlled second butterfly valves for smoothing out the engine..

The ZX12R also opens the throttle bodies slightly to increase the idle for running on choke.. The ECU richens the mixture based on engine temp...

I am sure the yamaha does the same..