Idle problem solved

ntst8 · May 23, 2019

Excuse the scruffy sketch, but if i understand the valve and injection timing correctly then at low revs injector 1 is pumping while inlet valve 2 is open.
Perhaps the oddities of airflow with a 270 crank then cause an issue on the 270 degree separation which doesn't arise on the 450 degree separation. The momentum of air into throttle body 1 might cause a pressure build when the inlet valve closes, combined with the venturi effect in body 2 causing the cross flow?
A bit simplistic, there are all sorts of dynamics involved which are beyond me.
Of course if the graph is rubbish then pls ignore.

TonyA · May 23, 2019

Thanks for your feedback iwilson . Your are doing us a great service on the forum . ntst8 , I think that about describes it !

iwilson · May 23, 2019

ntst8 said:
Excuse the scruffy sketch, but if i understand the valve and injection timing correctly then at low revs injector 1 is pumping while inlet valve 2 is open.
Perhaps the oddities of airflow with a 270 crank then cause an issue on the 270 degree separation which doesn't arise on the 450 degree separation. The momentum of air into throttle body 1 might cause a pressure build when the inlet valve closes, combined with the venturi effect in body 2 causing the cross flow?
A bit simplistic, there are all sorts of dynamics involved which are beyond me.
Of course if the graph is rubbish then pls ignore.
View attachment 10251

I've tried to envisage what's going on a few occasions - but generally I've had an alcoholic beverage in one hand at the same time, so didn't make much progress! I figured it I didn't need to understand exactly what was happening, but rather rely on testing. But here's a quick pic I've just drawn up. Which would seem to indicate how it might work, with the exhaust stroke of cyl. 2 drawing charge from cyl. 1. Hopefully it's anatomically correct!

contours · May 24, 2019

Thanks for such an enlightening discussion. Love your investigative work on this, iWilson! The only thing I can’t understand is why I do not have an idling issue (or at least one that bothers me). My Mk1 starts and idles reliably most of the time. It does sound rough, but it rarely stalls. But I do empathize with your quest for perfection. Good work!

cliffa · May 24, 2019

iwilson said:
Yes you could, that was my original plan. But... I've already spent more money on this problem than I should have. Secondly, it's all well and good to come up with ideas that 'might' work. But what if it doesn't and I'm left with a useless set of throttle bodies! Norton are quite happy to sell me another set, but as I have no commercial aspirations it could get very expensive, very quickly! The bike as I've proven actually starts and idles a hell of a lot better without the IACV assembly, so spending money on 'properly' fixing it would only get a marginal improvement over what I have right now. I am a bit of a perfectionist and it certainly niggles me, but really it's something for Norton to address with Jenvey. Bearing in mind despite the evidence I only have my bike as prove of the problem and solution.

I did send Norton my thoughts on the fix (below). But they seem more concerned at the moment with the TT and going forward I'd imagine their new range of bikes is where all the money is going - if not then maybe a MKIII will get it right! Jenvey kindly offered to make me a new set of throttle bodies with my changes for only 6,000 pounds!

Hi iwilson, I know you are happy with yours, so when I said "couldn't you" , the "you" was meant to be anyone who wants to experiment further. £6,000 yikes! what are they platinum ?

Cheers,

cliffa.

iwilson · May 24, 2019

cliffa said:
Hi iwilson, I know you are happy with yours, so when I said "couldn't you" , the "you" was meant to be anyone who wants to experiment further. £6,000 yikes! what are they platinum ?

Cheers,

cliffa.

I just meant it’s free to postulate what the fix might be - but potentially very expensive to try them out for real with no guarantee of success. If I’d just gone ahead and drilled a couple of new IAC holes for new hoses - I might have just ended up with a useless set of throttle bodies!

Kind of doomed myself by trying to come up with something that didn’t involve modifying the throttle bodies. If I had the required engineering skills and equipment I’d have persisted with another version. Got a brother in Canada who’s a Fitter and Turner - might send him the MKI version to correct its deficiencies.

As Norton own the design, Jenvey can’t modify a set for me. They would need to design a set just for me then build a mould to cast them. Group buy anyone?

iwilson · May 24, 2019

contours said:
Thanks for such an enlightening discussion. Love your investigative work on this, iWilson! The only thing I can’t understand is why I do not have an idling issue (or at least one that bothers me). My Mk1 starts and idles reliably most of the time. It does sound rough, but it rarely stalls. But I do empathize with your quest for perfection. Good work!

My bike also started and idled ‘most’ of the time. But not all the time! My theory is if you spend very little time at idle you’ll probably be ok. But with cyl. 2 running rich you run the risk of fouling the plug and it’s all down hill from there as cyl. 1 is so lean it’s not really contributing much. You’ll be amazed at how sweet the engine sounds once the problem is corrected. But if you prefer a lumpy idle leave things as they are.

ntst8 · May 24, 2019

Sounds exactly how mine behaves. I live i a semi rural area. If i ride straight onto the open road the bike runs relatively well, even if i the slow down for small towns etc. But if go straight in an urban area (60kph speed limit from here) it runs like a dog.

contours · Jun 9, 2019

ntst8 said:
Sounds exactly how mine behaves. I live i a semi rural area. If i ride straight onto the open road the bike runs relatively well, even if i the slow down for small towns etc. But if go straight in an urban area (60kph speed limit from here) it runs like a dog.

Yup.

TonyA · Jun 9, 2019

Are you using the O2 sensors ? The low to mid 3000 - 3800 rpm steady state throttle ?

ntst8 · Jun 9, 2019

Yes and yes. Roll on then roll off the throttle, repeat and it runs ok, get revs above around 4000 rpm and goes ok.
Wondering whether the sensors getting drenched is also part of the wet weather poor running issue. I greased/sealed all sorts of bits but haven't touched the wiring to the O2 sensors, and things are much improved from the first experience where i could barely keep it running in the rain. Again below 4000rpm need to roll on/off or drop to 4th and keep the revs up. Seems suspiciously tied to iwilsons note about mapping not being sensor related above 4000rpm.

Edit - i fitted a Bosch head temp sensor and cam sensor before the last run, speed sensor still to be done.

TonyA · Jun 10, 2019

It's the O2 sensors. I don't have that problem anymore. But , I am not telling you what to do . Just an innocent observer here.

contours · Jun 10, 2019

But cold starts, Tony? There has to be a sacrifice somewhere, right?

iwilson · Jun 10, 2019

contours said:
But cold starts, Tony? There has to be a sacrifice somewhere, right?

My o2 sensors are currently disabled and no IAC whatsoever. Bike starts from cold without touching the throttle, sits at 800rpm perfectly happy. Once warm around 1,200. Vid below.

TonyA · Jun 10, 2019

contours said:
But cold starts, Tony? There has to be a sacrifice somewhere, right?

No sacrifice . Only benefits . This has been fully proven on (Euro 3) Norton 961's by me and others in Canada . Also in England no names mentioned . Both New Omex and SC ECU's respond well . I have been O2 sensor free since May 2018 More than 6000 miles tested. Idle is smoother , Gas mileage is much better below 4000 rpm. If I drive 65 MPH indicated (62-63 actual) = 3800 RPM , I am getting 56 MPG US Gallons. There is nothing but upside from this. AND lastly no more gurgle/flat spot below 4000 rpm steady state throttle. We tried to tell you guys , but when the Euro 4 guys were getting issues we just stopped talking about it. I am never going back I can tell you that much , and my bike does nothing but run good ! In fact I am getting ready for another 2000 mile trip .

lcrken · Jun 10, 2019

Me too, Tony. 2015 961 with no cats, no O2 sensors, no idle air control valve, and it runs great in every way, except it does still sound like a thrashing machine. But no running problems.

Actually, it does still have O2 sensors, but they are not connected to the ECU. I'm monitoring and logging AFR data from two wideband sensors, but that has no effect on how the bike runs. I'm just trying to get a better feel for how the engine management is working, and maybe improve it a little by changing the maps. But it's going pretty slowly.

Ken

ntst8 · Jun 10, 2019

Even i am seeing the trend here... one more thing added to the to do list, thanks.

So much to read that it all gets to be a blur, i hadn't quite worked out whether iwilson's balance tube blocking had done away with the O2 sensor deletion, now crystal clear.

iwilson · Jun 10, 2019

Mine are only disconnected because the ECU is seeing some voltage on the o2 input pins even with the sensors physically disconnected. They do have a useful role to play but only if working correctly! Unfortunately without access to the ECU you’re flying blind when trying to figure out what’s going on/wrong.

contours · Jun 11, 2019

Awesome! I guess i haven't spent enough time here since the O2 sensor fix was first being tested.

TonyA · Jun 11, 2019

I am running the resistor plugs , not just disconnected O2 sensors. 330 ohm and 1 Meg ohm , one is for the heater pins the other for the signal pins .

Idle problem solved

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