Single TB 750 AND V7Mk2 e.f.i. Accessory |
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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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.
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.
Better 5 minutes late in this world than years early in the next. |
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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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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Brian.
Better 5 minutes late in this world than years early in the next. |
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motopete
Senior Member Joined: 18 Aug 2015 Location: Notts Status: Offline Points: 532 |
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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). something to be aware of… it'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. 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 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
Senior Member Joined: 13 May 2017 Location: Powys Status: Offline Points: 1882 |
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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
Senior Member Joined: 18 Aug 2015 Location: Notts Status: Offline Points: 532 |
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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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V7Chris
Senior Member Joined: 13 May 2017 Location: Powys Status: Offline Points: 1882 |
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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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Jonny Boy
Senior Member Joined: 28 Jul 2015 Location: Nottinghamshire Status: Offline Points: 106 |
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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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V7Chris
Senior Member Joined: 13 May 2017 Location: Powys Status: Offline Points: 1882 |
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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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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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I doubt Guzzi would replace spark plug caps as a recall. Recalls are only for safety items.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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V7Chris
Senior Member Joined: 13 May 2017 Location: Powys Status: Offline Points: 1882 |
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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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rapheal
Senior Member Joined: 13 Nov 2014 Location: west country Status: Offline Points: 573 |
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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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motopete
Senior Member Joined: 18 Aug 2015 Location: Notts Status: Offline Points: 532 |
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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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V7Chris
Senior Member Joined: 13 May 2017 Location: Powys Status: Offline Points: 1882 |
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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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jefrs
Senior Member Joined: 12 Aug 2018 Location: West Berkshire Status: Offline Points: 333 |
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Having fettled the Enfield EFI-500 with Power Commander and Autotune (wide-band O2) to produce a ton-up machine (only just, and one of very few such), some lessons learnt - One needs a very good understanding of spread sheets and numeric analysis to program the Power Commander, the dynamometer is not the whole story. One needs to visualise what the numbers in the map and trim tables are showing. One can get a moderate increase in peak bhp but and a substantial increase in torque lower down, wider power band. One can eliminate decel popping by tweaking the map, essentially by cutting the fuel off during deceleration zero throttle. One can get a smoother throttle response by tailoring the injector to the throttle opening (TPS). One can alter the ignition timing, this probably needs to be done to improve performance. Euro4 models seem to have quite different mapping to earlier ones. they seem to be less fussy about changing the silencer but more fussy about fitting a K&N, and disconnecting the Lambda for a 'dongle' resistor. My Enfield is an earlier type. The newer oem maps seem to be getting better at eliminating the idle pickup snatch and hesitancy. That said my V7.ii is stock and doesn't seem to suffer from this problem, it pulls away smoothly and spins up quick, no decel popping, otoh the Enfield was a complete pig and needed fixing. Having one bike that can rival the 1812 Overture, I have no desire for louder pipes on the Guzzi. I discovered that most OEM ECU maps are developed in Italy. The V7.ii is slightly cheaper to insure than the "modified" Enfield, as soon as you change a silencer the bike is "modified" and the premium shoots up.
Edited by jefrs - 17 Aug 2018 at 08:09 |
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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Interesting and useful, thanks. In the real world it's the amount of torque available which matters, peak power makes little difference. All the Guzzi ECUs are Magnetti-Marelli, so yes, Italian. The bit I find confusing is the variation in owner's experiences with their bikes. Some are happy with the way they perform, some say the same model (not the same bike) is almost unridable. Is there a real variation in the bikes, or is there a variation in owners perception?
Edited by Brian UK - 17 Aug 2018 at 10:46 |
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Brian.
Better 5 minutes late in this world than years early in the next. |
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