Idle problem solved

Only air 'should' pass through the IAC assembly. But the system is more dynamic than it might appear. Some air is also passing through the throttle butterfly's. During the engine cycle, valves are opening and closing, pressure is rapidly changing and because both cylinders are linked together via the IAC tube there are situations where there is such a pressure differential between the throttle bodies that charge laden air flows between the throttle bodies rather than down the IAC pipe. Remember at idle there is a relatively small amount of air flowing into the engine so it's easy for one cylinder to influence the other if joined (as they are by the shared IAC tube).

I know this to be the case since by measuring the AFR in each exhaust I can observe firstly with the stock setup that:

• Cyl. 1 runs very lean (AFR over 26:1) and cyl. 2 very rich - (both fuel injectors have been professionally tested and swapped between cylinders).
• I can increase the amount of fuel coming from cyl. 1's injector and when I do so, cyl. 2's AFR goes richer and cyl. 1 is essentially unchanged - I have checked to ensure the injectors are wired up correctly.

When I block the IAC tube that mechanically joins the two throttle bodies I observe the following:

• The AFR in both cylinders normalises - i.e. is approx. the same in both cylinders.
• If I now increase the amount of fuel coming out of injector 1 then I see the AFR for cyl. 1 go richer - exactly as it should.

This proves 100% that the majority of the fuel being injected into the intake port for cyl. 1 is being sucked back and through the IAC tube to end up in cyl. 2. You may struggle to envision it, but I have proven it scientifically using calibrated wideband o2 sensors inserted in each independent exhaust pipe. Not only that, my MKII ears can clearly hear the change in engine tone - it clearly just sounds a whole load happier to the point it can idle at speeds a factory engine could only dream of!

I'm reposting the first video from this thread. This shows the process as in action. First few seconds are with the stock setup - sensor 1 (cyl. 1), showing very lean (26:1 AFR). After that I block the shared IAC tube (remember I'm not blocking the intake so much as blocking the shared passage between the throttle bodies). Once that is done the AFR in both cylinders is perfect. The next part at around the 53 sec mark shows me adding fuel to injector 1 and you can see the sensor 1 lambda number drop as the cylinder runs richer (as it should).



To finally put this to rest here's another video. We pick up the action with the engine idling in factory stock condition. I then switch on cyl. 1's o2 sensor, as it's reading lean it immediately starts adding fuel (the 'Closed loop corr 1%' number starts increasing). But instead of seeing the lambda number for cyl. 1 begin to drop we instead see the lambda number for cyl. 2 drop from around lambda 1 (14.7:1) to .85 (12.5:1) - cyl. 1's lambda improves a touch but you can see the number dancing all over the place as further validation that some crazy things are happening in that intake port/throttle body with fuel coming and going in all directions!

richard-7 said:

We think some problems are from joined exhausts. When you replace with the catless pipes that are completely separate the bikes runs a lot better.

My dad and Tony separately made a manual choke. Works great. More to come.

Click to expand...

First revision then final version with pre-formed hoses . Kits may follow . View from the side shows a clean installation. User adjustable when seated on the bike . Factory IAC remains intact and operational for cold starts etc. Introducing the North American Idle Solution .

ok - that's interesting! It looks like you've inserted a manual valve in the the pipe that feeds the IACV? Is the IACV still active or is it unplugged in the open position? Tony could you explain the problem this setup is trying to solve? I presume the air being fed into each throttle body is still using the shared tube that I think is causing all (my) problems. Is this a manual method of controlling the idle speed?

So many questions!

Edit:
So it's a manual idle control valve. I haven't seen a problem with the IACV not doing it's job (I had suspected it at one stage). Really would be good to see some more data from other owners measuring the AFR of their engines at idle.

Hmm, I’m struggling to understand how this can work if the factory IACV is still working. The ECU sets the idle speed based on engine temperature. At the engine warms up the IACV controls the flow of air to achieve the target idle RPM. If you place a manual valve in front of it then the IACV will just open more to allow sufficient air to reach the target idle speed. If you’re using it to for situations when the idle is unacceptably high then this indicates problems elsewhere as the IACV is simply a stepper motor driven by the ECU to achieve a programmed RPM and should easily be able to restrict airflow sufficiently to regulate the idle. The exception to this would be if the throttle position screw has been adjusted open to far, since the IACV never completely closes, the manual valve could completely close the idle air supply. Is this the idea?

Hmm usual novel, one of the curses of knowing how to type!

"Bear in mind that the fuel injector does not fire on the intake stroke, what happens is that it builds up a thin film of fuel on the back of the valve this is constantly being depleted as it vaporises and is drawn into the cylinder.."

Great work for persisting with this.
Out of interest do you have the timing of the injector firing? Just trying to get my head around how the robbing works.

P.S. haven't forgotten the offer, should have some time after Queens Birthday Weekend - assuming the 961 gets me to Brass Monkey and back.

So from this really excellent investigative work would I be right in saying that the ideal setup would be an IACV with two separate channels and two unlinked (?) connectors on the throttle bodies?

I am thinking of the least intrusive modification so could you make a connecting pipe onto the existing throttle bodies with a centre baffle splitting the connector into two and going into the throttle body to split the two sides? Then I got to thinking would this be enough to reduce the flow from one side to the other in itself - ie the charge from one side would have to flow partly up the tube and back down again. Considering the dynamic aspect of the additional air mass to move would this be sufficient - especially if a shaped profile slowed the flow - to solve the problem enough so we could retain the standard IACV? Can anyone give a detailed picture of the throttle body IACV connector? If a modified connector could not be pushed in could we machine out the connector and make a two-port connector to fit into it?

Attempt to illustrate insert re. my incoherent ramblings above - anyone got 3d titanium printing facility?;

iwilson said:

Hmm, I’m struggling to understand how this can work if the factory IACV is still working. The ECU sets the idle speed based on engine temperature. At the engine warms up the IACV controls the flow of air to achieve the target idle RPM. If you place a manual valve in front of it then the IACV will just open more to allow sufficient air to reach the target idle speed. If you’re using it to for situations when the idle is unacceptably high then this indicates problems elsewhere as the IACV is simply a stepper motor driven by the ECU to achieve a programmed RPM and should easily be able to restrict airflow sufficiently to regulate the idle. The exception to this would be if the throttle position screw has been adjusted open to far, since the IACV never completely closes, the manual valve could completely close the idle air supply. Is this the idea?

Hmm usual novel, one of the curses of knowing how to type!

Click to expand...

Good Morning , I like you was not always happy with my idle. I do not remember what you were unhappy with . But I had the inconsistent idle , usually when fully warmed up . It was too high. Then eventually it could settle back down . Not always though . The first thing I did was to install the heat insulator between head and throttle body. This helped , now I could actually put my fingers on the throttle body after a 100 mile run and not burn them. After talking to David a while we discussed the throttle body expanding with heat and other issues. This is when we decided that a pre-regulator installed before the IAC might be beneficial . The thought at the time were to use a fixed orifice but I didn't like that as well . So installing a adjustable regulator might just be the ticket. So far its been working with aplomb ! And its a choice , not mandatory . If folks want to remove their IAC and set the butterflies for idle - Go Ahead . I like this way better. I have cold start facility when I need it and the ability to set my idle if necessary . Actually I set it after warm up before every ride now and this is working well for me .

iwilson said:

Only air 'should' pass through the IAC assembly. it should.......

This proves 100% that the majority of the fuel being injected into the intake port for cyl. 1 is being sucked back and through the IAC tube to end up in cyl. 2. You may struggle to envision it, but I have proven it scientifically using calibrated wideband o2 sensors inserted in each independent exhaust pipe. Not only that, my MKII ears can clearly hear the change in engine tone - it clearly just sounds a whole load happier to the point it can idle at speeds a factory engine could only dream of!

Click to expand...

iwilson,

thanks for the info.
It makes perfect sense now.

I never imaged that charge was being sucked across the common IAC tube.
You have proved the case for sure.

Makes sense also that I spyed a friends Kawasaki 4 cylinder and there were 4 lines coming out of the air control valve housing. 4 keihin throttle bodies - 4 separate IAC lines. The way it should be.

Hello Again iwilson , Have you had a chance to try out your new K&N type clamp on air filters ? I saw them on your bike just wondering if you have made any decisions on it.

Does anyone think a pair of Keihin EFI throttle bodes, and IAC lines from a Jap bike can be adapted to run on a 961?
I wonder if the SC or OMEX ECU's can operate a Keihin injectors?

What type of throttle bodies does the new V4 use?

I'm not a 961 owner, but it sure is an interesting thread. Similar to what you've already tried iwilson, couldn't you plug the balance pipe drill and tap each manifold, fit a 90º spigit to each, then fit a Y connector to the IAC outlet, connecting a hose to each spigot with a reed valve in line? That way IAC could only feed one cylinder as required. Like this (excuse the artwork, but I think you'll see what I mean)...





Cheers,

cliffa.

richard-7 said:

We think some problems are from joined exhausts. When you replace with the catless pipes that are completely separate the bikes runs a lot better.

My dad and Tony separately made a manual choke. Works great. More to come.

Click to expand...

To separate pipes is exactly what Egli recommended and did with my bike...

Raphi said:

To separate pipes is exactly what Egli recommended and did with my bike...

Click to expand...

De cat pipe from Norton is also two separate pipes these days.

cliffa said:

I'm not a 961 owner, but it sure is an interesting thread. Similar to what you've already tried iwilson, couldn't you plug the balance pipe drill and tap each manifold, fit a 90º spigit to each, then fit a Y connector to the IAC outlet, connecting a hose to each spigot with a reed valve in line? That way IAC could only feed one cylinder as required. Like this (excuse the artwork, but I think you'll see what I mean)...





Cheers,

cliffa.

Click to expand...

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!

TonyA said:

Good Morning , I like you was not always happy with my idle. I do not remember what you were unhappy with . But I had the inconsistent idle , usually when fully warmed up . It was too high. Then eventually it could settle back down . Not always though . The first thing I did was to install the heat insulator between head and throttle body. This helped , now I could actually put my fingers on the throttle body after a 100 mile run and not burn them. After talking to David a while we discussed the throttle body expanding with heat and other issues. This is when we decided that a pre-regulator installed before the IAC might be beneficial . The thought at the time were to use a fixed orifice but I didn't like that as well . So installing a adjustable regulator might just be the ticket. So far its been working with aplomb ! And its a choice , not mandatory . If folks want to remove their IAC and set the butterflies for idle - Go Ahead . I like this way better. I have cold start facility when I need it and the ability to set my idle if necessary . Actually I set it after warm up before every ride now and this is working well for me .

Click to expand...

Yes you're right, if I remember correctly it was erratic - I was never quite sure how it would behave. This was at the same time the oil in the airbox fixes were being rolled out and new ECU maps were coming and going. Unfortunately as I didn't have access to the ECU I'll never know what the problem was, quite possibly a combination of factors.

In regards to your setup and observations. The temperature of the throttle bodies could make a difference at idle as the air flow is quite minimal and the ECU adjusts fueling based on the intake air temperate (in the airbox). If there was a big difference between the measured and actual intake air temperature that will cause problems. But you know what, you could write paragraphs putting forward all sorts of ideas as to what might be going on! All that matters at the end of the day is you've found something that for one reason or another improves the engines characteristics!

Just saying.....


Hosted on Fotki

TonyA said:

Hello Again iwilson , Have you had a chance to try out your new K&N type clamp on air filters ? I saw them on your bike just wondering if you have made any decisions on it.

Click to expand...

Yes I did run the bike with them for a while. No problems, except you need to find somewhere to mount the intake air temp sensor where it won't get covered in crud but will still give accurate data. Once I'd finished mucking around with the idle I put the airbox back in as there was no reason not to.

ntst8 said:

"Bear in mind that the fuel injector does not fire on the intake stroke, what happens is that it builds up a thin film of fuel on the back of the valve this is constantly being depleted as it vaporises and is drawn into the cylinder.."

Great work for persisting with this.
Out of interest do you have the timing of the injector firing? Just trying to get my head around how the robbing works.

P.S. haven't forgotten the offer, should have some time after Queens Birthday Weekend - assuming the 961 gets me to Brass Monkey and back.

Click to expand...

I posted a pic on this thread showing the injector timing table. Good luck with the brass monkey, remember the best adventures are the ones that don’t go according to plan! Hopefully catchup when you return.

Oops, should have read that.
Not that i have a spare but you have probably earned one of these.