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Single TB 750 AND V7Mk2 e.f.i. Accessory

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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 05 Feb 2018 at 20:43
Actually the Lambda sensor gives a high voltage for a rich mixture and a low one for a weak mixture. The modifying gizmos like the Finebau and Fat Duc reduce this voltage slightly to make the ECU think the mixture is too weak, and it richens the mixture accordingly. 
oxygen sensor switching voltage
 
You can get a similar result with a straightforward resistor bridge, or indeed just a schottky diode in series with the sensor output. The latter has been proved to work on earlier V7s, but don't know about the later ones. I tried it on my Norge, but it sometimes brought up the Service light, reporting a lambda sensor fault.
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Brian UK View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 05 Feb 2018 at 20:48
You could just disconnect the lambda sensor and try it like that. The small block still seems to work and runs on the base map, which is often better than closed loop. It would also highlight a fault with the lambda sensor.
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motopete View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote motopete Quote  Post ReplyReply Direct Link To This Post Posted: 06 Feb 2018 at 19:12
That’s right Brian, a Zirconia lambda sensor produces an output voltage when the mixture is around the stoichiometric point.
ECU's typically decide weak/rich at around +0.4V. In my experiments I shifted this threshold to +0.8V, which is the same as attenuating the sensor output by half using resistors. On my engine I found the shift to +0.8V made a small difference, but definitely still too weak.
 
Whilst the resistor technique or indeed a schottky diode is attractive due to its simplicity, it has 2 disadvantages:
 
1) It’s only possible to shift the lambda sampling threshold, therefore only a small shift in AFR is possible using a 'standard' narrow band Zirconia sensor. 
 
2) The resistors must be high value (100’s kohm minimum) to avoid loading the lambda sensor. The sensor is a very weak voltage generator, and unless the resistors are connected very close to the ECU there’s a strong chance of noise pick-up on the ECU signal, thereby confusing the ECU (false “rich” indications).
 
  
Exclamation something to be aware ofit's easy to "over adjust" a resistor based gadget such that the sensor's unable to generate a voltage high enough to reach the ECU sampling threshold. In this case the bike will probably appear to run well and you’ll be well chuffed, but the reason it’s running well is because the ECU isn't receiving any feedback so it defaults to open loop mode.

Lamp The same effect can be achieved by simply unplugging the lambda sensors... Which begs the question, why not just unplug the lambda sensors and run the default map?
I suspect the default map is safe  because that’s how the ECU would operate if a lambda sensor fails…
 

BTW, if you have access to a digital voltmeter (basic ones are pretty cheap nowadays) it’s fairly easy to check whether the engine’s running closed loop or open loop . Tap into the lambda signal and watch it switch from around +0.1V (weak) to +0.9V (rich). The switching rate might be too fast for your meter to keep up with, but over a few seconds you’ll see the signal in both states (low and high). The fact it's changing state means the ECU's running closed loop.
If the engine’s running open loop the lambda voltage will be stuck high, around +0.9 to +1.0V, because the default map is slightly rich.

End of waffle Beer
 PS. With a threshold of +0.85V and about 300ms delay I find my engine is quite happy, with a nice pale grey dusting on the plugs.

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V7Chris View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote V7Chris Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2018 at 18:00
Thanks for the comments guys. I can't pretend to understand all this electronickery, I am strictly a spanner man. Ultimately, how the Finebau unit works is of less concern than the source of the failure to respond to throttle input as it ran fine when I initially installed it. I shall hopefully get a chance to disconnect it this weekend and see if that makes a difference.
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motopete View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote motopete Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2018 at 18:32
Just a thought Chris, but are your plugs/plug caps OK? I'm sure I've heard the standard plug caps can go dicky - although I've had no problems with mine (11k miles)*

* Until next time I come to start it no doubt.

But as you say, the easiest way to eliminate the Finebau is to disconnect it.
Try running without the lambdas connected initially, it should run fine because it won't go into silly-weak closed loop mode.

Then stop and connect the lambdas. You should be back to original behaviour (i.e. tempermental throttle response at low revs/low throttle opening until it's thoroughly warm).

I'll be interested to hear how you get on...
Pete.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote V7Chris Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2018 at 23:17
Thanks Pete, will do and if the elimination of the Finebau unit doesn't work, I will look at the plug caps.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Boy Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2018 at 17:09
Speaking of spark plug caps, the dealer replaced mine under warranty due to what they said was a recall from MG.
I didn't receive any notification myself from Guzzi, just a call from the dealer who collected, fixed and returned the bike. That was late 2015 on a V7II bought that August.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote V7Chris Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2018 at 17:25
Hi Jonny
My v7ii was bought May 2015. I don't know if they did this at the first service but nothing was mentioned. Interesting though. Which dealer out of interest?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2018 at 21:14
I doubt Guzzi would replace spark plug caps as a recall. Recalls are only for safety items.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote V7Chris Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2018 at 17:29
Well, finally got around to disconnecting the Finebau unit. Gave it a 15 mile run and pretty much back to standard v7ii behaviour (poor part throttle/ low rev running etc.) But a strange episode at one point where the poor response to throttle input/ misfire occurred once. So if it doesn't settle down after a longer run, I shall change the plugs and caps and see how I get on as MotoPete suggested.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rapheal Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2018 at 21:41
I fitted one to my breva, after a long European tour where i got fed up with the popping and banging on the over run
what a difference
downhill no popping and banging
pulling away, the engine spools up much quicker with more power
and no more juddering below 3k when riding in traffic
worth every penny, I was considering getting rid of the bike and going back to an old BMW for the better low speed riding ( but not handling)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote motopete Quote  Post ReplyReply Direct Link To This Post Posted: 21 Feb 2018 at 20:02
The Breva 750's I've come across seem to run quite smoothly compared to the later V7's, so I imagine a little tweak to the fueling will make it nigh on perfect.

I'm pretty sure the V7 II runs leaner than the Breva, so it's more difficult to coax the fuelling back to anything approaching sensible.
What the V7 II really needs is the V7 III engine!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote V7Chris Quote  Post ReplyReply Direct Link To This Post Posted: 25 Mar 2018 at 17:21
Originally posted by motopete motopete wrote:

T<span style="line-height: 16.8px;">he Breva 750's I've come across seem to run quite smoothly compared to the later V7's, so I imagine a little tweak to the fueling will make it nigh on perfect.</span>

I'm pretty sure the V7 II runs leaner than the Breva, so it's more difficult to coax the fuelling back to anything approaching sensible.
What the V7 II really needs is the V7 III engine!


Or even the V9 engine perhaps? Went for a couple of runs in the last few days and very irritatingly, it is fine 95% of the time. Intermittent stutter/missfire /failure to respond to throttle input. Recommendation for plug caps - NGK perhaps? Can't remember the last time I bought some but must be 10 years +
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