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Discussion Starter #21 (Edited)
Nice to make your acquaintance!

I assure you the engine management system does not run in closed loop unless it’s steady-state-cruise-steady-throttle. The rest of time the ECU runs in open loop and the O2 sensors are not used, the ECU and then relies on the various other "inputs" such as TPS and of course the OEM map. Note the PCIII does not change the OEM map as the PCIII is after the ECU.

A lot of people on VFRD have done a cat-ectomy, also FWIW I have not heard of people with failed or overheating cats from PAIR disabling.

I have talked extensively with Honda Canada and the top whizzes on VFRD I own the shop manual and have an OK background in this stuff but I don't make a living at it like you, alas. BTW the reason Honda did this silly stuff was to meet emissions regulations not in place yet (I cannot recall the standard but it's CARB 2010 compliant or some such).

I truly welcome any ideas and input you have on making the throttle action more linear.
 
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Nice to make your acquaintance!

I assure you the engine management system does not run in closed loop unless it’s steady-state-cruise-steady-throttle. The rest of time the ECU runs in open loop and the O2 sensors are not used, the ECU and then relies on the various other "inputs" such as TPS and of course the OEM map. Note the PCIII does not change the OEM map as the PCIII is after the ECU.

A lot of people on VFRD have done a cat-ectomy, also FWIW I have not heard of people with failed or overheating cats from PAIR disabling.

I have talked extensively with Honda Canada and the top whizzes on VFRD I own the shop manual and have an OK background in this stuff but I don't make a living at it like you, alas. BTW the reason Honda did this silly stuff was to meet emissions regulations not in place yet (I cannot recall the standard but it's CARB 2010 compliant or some such).

I truly welcome any ideas and input you have on making the throttle action more linear.

Maybe let me know where you heard about the closed/open loop steady throttle deal. I have never heard of this, especially if they are trying to meet CARB standards. If this was the case then disconnecting the PAIR system or removing the o2 sensor connections would not make the slightest difference as the only time the bike would be in closed loop would be when none of these issues we are having are taking place.
 

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Discussion Starter #23 (Edited)
There are six main things that can exacerbate VFR throttle problems:

1) At very low throttle openings if the SV's are not synced.

2) At steady state when the ECU goes into closed loop the EFI fuel ratio wants to go stoichiometric and thus you can have lean surging.

3) While spinning up through the VTEC transition @ 6,800 RPM (this changed on the ‘05’s but I’ll not bother talking about that here) there is a stumble then a hit due to the abrupt opening of the extra valves. This is most notable at smaller throttle openings at lower engine loads when transitioning slowly up and down repeatedly through the VTEC transition.

4) At some throttle openings and gear positions etc the EFI maps too lean for smoothest performance (this one is somewhat contentious but if you look at the maps of people’s VFR's before and after proper dyno tuning the end results are most often a higher F/A at some given settings, so I give it credence and hey Dynojet thinks most modern bike EFI's are too lean at certain operational points).

5) There is some argument that the VFR VTEC’s engine management system does not work as well as some other bikes, and if you check the 05’s on up they have made some changes such as a different (finer) injector, altered the VTEC engagement RPM, staggered the VTEC engagement/disengagement RPM's, and altered the EFI map - maybe other stuff too but that’s all I know of related to the engine management system. Understandably this one is also somewhat contentious and I do not give it as much credence as the general map leanness viewpoint because some other brands of bikes appear to have EFI systems no more (and perhaps less sophisticated) than the 6th gen on up to the ‘04’s, but OTOH you would need to ask why Honda made these tuning changes if there were no issues related to this argument. There have not been a lot of 05’s on up sold as of yet to get a picture, but the consensus so far seems to be that the engines are more tractable and more predictable.

6) Throttle cable slack.

In answer to your question about my sources I have already listed them in my first post and in subsequent posts to you and others as discussed.

Honda Canada
VFRD (there was big crash so older data is gone)
The Honda shop manual
and http://www.bikersoracle.com/vfr/forum/showthread.php?t=44763&page=1&pp=15

I forgot to mention I also had a number of chats with the fine people at Dynojet. I would not say they were experts with the VFR VTEC’s idiosyncrasies but they are a wealth of general tuning information. Remember I said I cannot recall the future emissions standard the VFR was targeted for........I could find out. You sound about the same age as me; perhaps we can meet up and go for a spin and a beverage sometime.

Cheers,
Dan
 
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There are six main things that can exacerbate VFR throttle problems:

1) At very low throttle openings if the SV's are not synced.

2) At steady state when the ECU goes into closed loop the EFI fuel ratio wants to go stoichiometric and thus you can have lean surging.

3) While spinning up through the VTEC transition @ 6,800 RPM (this changed on the ‘05’s but I’ll not bother talking about that here) there is a stumble then a hit due to the abrupt opening of the extra valves. This is most notable at smaller throttle openings at lower engine loads when transitioning slowly up and down repeatedly through the VTEC transition.

4) At some throttle openings and gear positions etc the EFI maps too lean for smoothest performance (this one is somewhat contentious but if you look at the maps of people’s VFR's before and after proper dyno tuning the end results are most often a higher F/A at some given settings, so I give it credence and hey Dynojet thinks most modern bike EFI's are too lean at certain operational points).

5) There is some argument that the VFR VTEC’s engine management system does not work as well as some other bikes, and if you check the 05’s on up they have made some changes such as a different (finer) injector, altered the VTEC engagement RPM, staggered the VTEC engagement/disengagement RPM's, and altered the EFI map - maybe other stuff too but that’s all I know of related to the engine management system. Understandably this one is also somewhat contentious and I do not give it as much credence as the general map leanness viewpoint because some other brands of bikes appear to have EFI systems no more (and perhaps less sophisticated) than the 6th gen on up to the ‘04’s, but OTOH you would need to ask why Honda made these tuning changes if there were no issues related to this argument. There have not been a lot of 05’s on up sold as of yet to get a picture, but the consensus so far seems to be that the engines are more tractable and more predictable.

6) Throttle cable slack.

In answer to your question about my sources I have already listed them in my first post and in subsequent posts to you and others as discussed.

Honda Canada
VFRD (there was big crash so older data is gone)
The Honda shop manual
and http://www.bikersoracle.com/vfr/forum/showthread.php?t=44763&page=1&pp=15

I forgot to mention I also had a number of chats with the fine people at Dynojet. I would not say they were experts with the VFR VTEC’s idiosyncrasies but they are a wealth of general tuning information. Remember I said I cannot recall the future emissions standard the VFR was targeted for........I could find out. You sound about the same age as me; perhaps we can meet up and go for a spin and a beverage sometime.

Cheers,
Dan
Sounds good, I will take you up on that!
My bike is an 05, so I don't think they have achieved much.
I'm originally from the UK so I always pick up BIKE magazine, its ironic but this months tests the VFR against the BMW 800. They really pick fault with the "snatchy" throttle the VFR has and even write an article about what happened to your wonderful engine Honda?
I will bring my bike into the shop at work one day and measure the emissions and do some experimenting with the o2 sensors.
If you pm me your email I will scan the article and send it you if you wish.
 

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Discussion Starter #25
I would like to read that article sure! I’ve pm’d you

Does your bike have the clear turn signal lenses? If so that hopefully will confirm it has the latest changes I talked about such as the different (finer) injectors, altered VTEC engagement RPM, staggered VTEC engagement/disengagement RPM's, and altered the EFI map.

Don’t get me wrong I still think it’s a nice bike. I was going to sell mine but after all the farting around getting it running decently I can’t really find anything I like that much more to warrant all the hassles of selling and buying.

I’ll say this: Honda sometimes has wacky ideas about how to apply technologies, OTOH Honda sometimes gets it amazingly right too.
 

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Discussion Starter #27
Then I made a mistake in that the most recent engine management changes I talked about start with the '06 model year. Sometimes it’s hard to remember all the trivia associated with VFR’s. Back to watching South Park!
 

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Discussion Starter #28 (Edited)
Hi-yah Steve,

You might be interested in what’s happening with the 2nd generation Yamaha FZ1. It too is plagued with EFI problems, but because it’s a much better supported bike in the after-market (Ivan etc) there are now solutions which we cannot get for our VFR VTEC’s. In particular a Fuel Cutoff Eliminator is unavailable for the VFR VTEC.

My prediction is that the next 5 years are going to see more and more bikes with emissions regulations EFI issues.

http://www.bikemagazine.co.uk/nav?page=bikemagazine.contentspage&fixture_page=5289716&resource=5289716&view_resource=5289716


On an efi engine, tickover fuelling is handled by injectors, but the engineers turn them off on closed-throttle coasting. Nobody should notice because the throttle is shut – so the rider won’t care – and there’s less fuel, unburned or otherwise, in the exhaust mixture.

But if you cut off fuel to an engine spinning at, say, 5000rpm (with pistons whizzing up and down 40 times per half second), the motor purges itself of fuel (in fact an efi motor purges itself of everything – with the throttle closed there’s no air either, which creates a vacuum, a problem in itself).

So now the inlet tracts and combustion chamber of the efi engine are ‘dry’. Which is okay if you keep the throttle closed and run the engine down to tickover – the injectors just switch back on again to keep the motor running. But what happens if the rider opens the throttle again before that point?

Engineers call this process ‘fuel reinstatement’. The rider twists the throttle and the bike’s ECU reads this, telling the injectors to deliver fuel into the air-stream in the throttle bodies.

At the same time, a butterfly valve in the throttle bodies opens, allowing air into the inlet tracts (the ECU also opens secondary butterfly valves – slowly – using a servo, to control the transition from closed throttle to open throttle).

So fuel is squirted from the injectors and the butterfly valves are partly open to let air into the engine.

But because the motor is completely fuel-less, the new fuel has to travel the length of the inlet tracts and into the combustion chamber before it can burn. It’s not a big distance, but it’s far enough to introduce a delay between opening the throttle and getting a response.

Also, some fuel from the initial injection is drawn out of the fuel/air mixture and re-lines, or ‘wets’, the walls of the inlet tracts, adding further delay in the petrol reaching the cylinder.

The cumulative effect is called the ‘fuel transport time’ – and the longer that is, the worse the throttle snatch.
 
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Hi-yah Steve,

You might be interested in what’s happening with the 2nd generation Yamaha FZ1. It too is plagued with EFI problems, but because it’s a much better supported bike in the after-market (Ivan etc) there are now solutions which we cannot get for our VFR VTEC’s. In particular a Fuel Cutoff Eliminator is unavailable for the VFR VTEC.

My prediction is that the next 5 years are going to see more and more bikes with emissions regulations EFI issues.

http://www.bikemagazine.co.uk/nav?page=bikemagazine.contentspage&fixture_page=5289716&resource=5289716&view_resource=5289716

Yeh thats the same mag. I got the VFR issue out of I sent you.
Just finished syncing my starter valves. I also adjusted the chain at the same time (never done it yet so figured it's about time)
By the way I checked the pair valve while I was at it, its open unless powered closed on throttle shut off. I did some experiments with the pair on and off while monitoring the mercury tubes. There is quite a difference between the measurements with the pair plugged or not. If you are running the pair I would sync the starter valves with it connected. If your going to plug it then sync the starter valves with it plugged. I know thats not the "Honda" way but there is quite a difference in the back pressure between the front 2 and the rear cyls. With regard to the throttle switch I am experimenting also to find when fuel cut off takes place on the Honda. The VFR has a potentiometer for a tp sensor so it would be easy enough to build iin a circuit so it never sees idle at throttle shut off at higher rpm or road speed. Thats all the guy did to fix the Yam. Ive done it before on cars.
By the way the tp sensor is part of the throttle assembly so you dont want to Fxxx it up!! Right now I have the pair valve working again and will try the bike when the rain stops (if ever). It dosn't take very long to do the starter valves so I will see what has transpired with this adjustment first.
Steve
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Discussion Starter #30
I synced the SV’s the way Honda recommends in the shop manual, I can’t remember if that meant with the PAIR disabled or enabled, as that was two years ago now.

I would really like to know the exact RPM fuel cutoff takes place, and also if it matters what gear it’s in, and also if it matters what speed you are going.

I know the TPS is a pot and you could add or subtract resistance by either putting a resistor in series or one in parallel (whichever is required I’m not sure). I am an Electrician so I know RLC resistance / inductance / capacitance circuits.

What I’m wondering though, is that by changing the effective overall TPS resistance so the ECU never thinks the bike has the throttle fully closed, you are in essence throwing the TPS out of sync. That would mean the EFI pulse width would be longer at all throttle positions (expect full throttle) and would make all F/A settings a bit richer. Wouldn’t it?

I brought this up on VFRD http://www.vfrdiscussion.com/forum/index.php? but no one seemed to know and no one I have ever talked anywhere else has tested for fuel cutoff or tried to defeat fuel cutoff. AFAICT you are the first to look into VFR fuel cutoff. I did ask Ivan's Rockland County Motorcycle and he said he did not know and has no plans for the VFR.

Great stuff man, and it sounds like you could get cool results that would make the VFR easier to operate. The question is: does the VFR use fuel cutoff to minimize emissions?
 
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I have not gone in to it yet but a simpler way maybe is to remove the road speed signal at the engine ecu. I have only got the wiring diagram for the non abs model (mines abs) however it looks like the speed signal is hard wired to the speedo, engine ecu and abs cu separately (no can bus) if this is the case it would be easier enough to try. I wouldnt think it would set a fault because it is a normal situation (bike at standstill). If Honda use fuel shut off, that would explain the issue of the sharp turn while moving irritating throttle snatch I get.
Twice on my commute going downhill braking and turning right quite sharply. Also the irritating snatchy throttle going over bumps on decel.
First things first though I have to find if they use throttle shut off!
By the way, looking at the way the idle increases with the pair connected it shows that the pair system is actually helping to overcome the back pressure of the cat/exhaust system and speed the exhaust gas's out.
 

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Discussion Starter #33
Go Freddy!

Assuming the road speed signal can be deleted from the engine ECU without causing problems, why would stopping this signal would stop fuel shut-off? I would have thought RPM and TPS are the two variables needed for fuel-shut off.

With the FZ1 RPM @ 4,500 and over plus closed TPS signal enables fuel-shut off. I don’t think road speed signal is part of fuel shut-off logic, but I could be wrong. BTW Ivan’s FZ1 Fuel Cut-off Eliminator is a small tube with 6 wires.
 
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Go Freddy!

Assuming the road speed signal can be deleted from the engine ECU without causing problems, why would stopping this signal would stop fuel shut-off? I would have thought RPM and TPS are the two variables needed for fuel-shut off.

With the FZ1 RPM @ 4,500 and over plus closed TPS signal enables fuel-shut off. I don’t think road speed signal is part of fuel shut-off logic, but I could be wrong. BTW Ivan’s FZ1 Fuel Cut-off Eliminator is a small tube with 6 wires.
I don't know about Honda but BMW only cuts fuel with a road speed signal.
Anyway the main thing is my VFR is awesome now the starter valves are synced. I rode for 5 hours last Sunday (actually came out your way).
The bike runs great with no snatch at any time, I rode to work today in traffic and it's a different beast!
As I said I synced them with the pair working also making sure that as I opened up the throttle all cyls where pulling the same. I also adjusted the chain. I am running the idle at 1500 with the pair connected.
If I had adjusted them with the pair blocked off as in the book then when it's connected back they would have been a mile out! Try it you will see how far out they are. With the manometer connected set them with your thumb over the pair hose (air cleaner connector) then remove your thumb, the revs will increase and the gauges will be way out!
 

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steve tech said:
Anyway the main thing is my VFR is awesome now the starter valves are synced. I rode for 5 hours last Sunday (actually came out your way).
The bike runs great with no snatch at any time, I rode to work today in traffic and it's a different beast!
Hmmm, I think both your bikes are essentially stock - except for the fiddling and adjustments noted in this thread. I am fortunate but I have never had any noticeable lag, no real flat spot around 5,000 to 6,000 rpm and always a very smooth VTEC transition. All I have done, besides basic maintenance, is tighten my throttle cable a couple of times to remove any annoying slack and put on Remus CF pipes (cat back set up) which seems to give the bike a little extra mid-range oomph - strictly seat of the pants impression though. Now you have got me wondering if I can make a good bike even better... or should I stick with the old 'if it ain't broke don't fix it' philosophy? I have ridden one other 6th gen VFR and it seemed a little 'jerkier' than mine - a little harder to ride smoothly and it seemed to have a slower throttle response, but all this talk of improving an already great bike has got me wondering. One day I may want to hook up with you guys and compare notes - and see if it is worth fiddling with the bike to get even better performance.
 

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Discussion Starter #36
Hi-yah Steve,
The VFR engine management system is nowhere near as sophisticated as modern autos, Honda’s system would be much more akin to the FZ1 (minus VTEC of course), that’s pretty bare-bones-basic by auto standards. I'm taking a decent guess that if the FZ1 ECU needs RPM data for fuel cut-off, so would the VFR's ECU.

The last time I synced the SV’s was two years ago and I did get them nice and even at idle, but I seem to recall they did not run even off idle. Maybe I should try and sync the SV’s with PAIR enabled and off idle too.

Did you try syncing the SV’s with PAIR disabled as per the manual to see if it made things better or worse?

I have confirmed that the SV’s can go out of sync easily and it takes many km's before they “settle down”.

Hey Thumps,
You might be a happier rider by following these suggestions, shops don’t do this kind of stuff with a routine service. For me this is the first bike engine I was not real happy with out-of-the-box, and I don’t breathe on gear unless it bugs me. Like Steve pointed out, Bike mag agrees about the VFR being wacky.

Colbert Report's on, gotta go!
 

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kinda off the topic but has anyone had issues with valves being out of adjustment?iam curious as i work on these things alot and have run into many that are out.i keep hearing that they rarely go out but iam finding alot are tight and its always on the 05/06's.
 

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Discussion Starter #38
I’ve heard the same things as you that they hold their clearances well. How exactly are you checking them; I am sure you know getting the correct “feel” can be rather subjective.
 

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kinda off the topic but has anyone had issues with valves being out of adjustment?iam curious as i work on these things alot and have run into many that are out.i keep hearing that they rarely go out but iam finding alot are tight and its always on the 05/06's.
My '02 has 53,000 kms now - I have had two valve inspections done - both times no adjustment needed.
 
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Hmmm, I think both your bikes are essentially stock - except for the fiddling and adjustments noted in this thread. I am fortunate but I have never had any noticeable lag, no real flat spot around 5,000 to 6,000 rpm and always a very smooth VTEC transition. All I have done, besides basic maintenance, is tighten my throttle cable a couple of times to remove any annoying slack and put on Remus CF pipes (cat back set up) which seems to give the bike a little extra mid-range oomph - strictly seat of the pants impression though. Now you have got me wondering if I can make a good bike even better... or should I stick with the old 'if it ain't broke don't fix it' philosophy? I have ridden one other 6th gen VFR and it seemed a little 'jerkier' than mine - a little harder to ride smoothly and it seemed to have a slower throttle response, but all this talk of improving an already great bike has got me wondering. One day I may want to hook up with you guys and compare notes - and see if it is worth fiddling with the bike to get even better performance.
Hi, I'm the kind of guy that thinks if its not broken don't fix it!!
I got involved in this because like Dan this is the first bike that Ive owned that I thought was a pain to ride around town.
I think it depends on your mechanical ability, if you really understand how it works and what your doing then go for it. If not you may end up with it being worse.
 
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