Starter Valve Syncing And Low Speed Throttle Response

[HighSideNZ]

Hi all

I've been working on how to get the low speed, throttle position from 0 to 4-5%, throttle response better on my 2010 VFR800 Vtec.

There is a huge post over on Bikers Oracle where one member has been saying for a long time that the flat syncing of the starter valves, as shown in the Gen 6 service manual is not correct and they should be synced similar to the Gen 5 and earlier VFR's.

This is where 2 starter valved are set at +10 mm/hg and the other adjustable one set at -10 mm/hg, hence staggering how the vales open in the early throttle opening (0 to 4% by what Honda UK have said).

I've been testing this theory over the past few weeks and changing the steps between the offsets until I've now got to about +/- 20mm/hg between them.

With the valves set like this, the low speed response is amazing.

I must say that I have a Rapid Bike 3 ECU fitted and have built a good map for it over time using a wideband O2 sensor and data logger, so I've been able to remove the 3000/4000 rpm stumble and lessen the Vtec kick in pretty much.

Back to the starter valves.

I've not stuck with the exact process that the Gen 5 uses and have set valve 1 at +20, and valves 2 and 3 at -20, with valve 4 (unadjustable) used as the datum at zero.

I feel that this gives a more varied throttle application off closed as the valves with a higher vacuum reading when synced will stay closed longer. So I think I get cylinders 2 and 3 applying power first, then number 4 kicks in, and lastly number 1. A much more staged application of power until you are at 4% throttle, then the butterflies take over.

What I can now do with the throttle, at no load in neutral, is bring the rpm up to 3000 and hold it, raise it to 3500 and hold it, drop it to 2500 and hold it and then go back to 3000. All quite fluidly.

In the past, when I tried the above, you could hold the 3000, raise it to 3500, but when trying to drop to 2500 the rpm would drop all the way and you couldn't get any smoothness.

It's completely different now. Rolling the throttle on thru a corner or round a roundabout is just soooo much smoother.

As the starters only affect the throttle from 0 to 4% on the tps, this seems to have no effect on power or cold starting, but it make a huge difference from a closed throttle.

Below is a photo of the end settings on my vacuum gauges as an example.

[Skids]

Interesting....

[Switchblade]

Nice !!

[Rush2112]

How did it feel when you set it like a 5th gen?

Sent from my SCH-I200 using Tapatalk

[Lint]

This is excellent timing for your post, thank you. I just read yesterday or the day before about setting it up like a fifth gen, but I couldn't find the data about it.

I an definitely doing this this coming week and seeing what difference it makes. As I do not have a fuel controller, I am interested in how it affects it.

I know that disconnecting the PAIR valve electrical connection, pulling the vacuum off of the flapper valve and taking off the snorkel has helped a great deal. If this theory of yours plays out, this should make the last little bit of difference I need.

[HighSideNZ]

When set like the 5th Gen I feel there was an improvement definitely over all valves being set equal.

But the most improvement has come with what I'm running now.

Food for thought!

Phil

[vfr350]

When you started how far out of sync were you from factory spec?

[HighSideNZ]

To be honest I didn't take much notice as the first time I synced them was after I did the valve clearances and I set them at that stage to flat as per the manual as I thought that was what they should be.

It's only after that, and chasing a tractable throttle response that I started looking at what earlier model did.

Back in the day I had a couple of VF750F's and being a Honda mechanic at that stage, I remember the tolerance for syncing the carbs was 60mm/hg. Of course being CV carbs you didn't suffer from the light switch effect of the FI systems we have today but 60mm is still 3 times the tolerance for the VFR.

Phil

[Mohawk]

I think you have a misconception about how the SV's work.

The throttle butterflies are not involved in this, thus when you open the throttle all throttle plates open at the same time, same rate as the rest. The SV's are a seperate air induction circuit for idle only.

That said the 5th gen uses a differential vacuum setting so that the intake & exhausts are in balance & it does make a huge difference to the throttle opening response & engine pickup when set correctly.

Doing the same on a 6th gen should assist in a smooth idle & transition to the throttle butterflies. But please note the 6th gen has differential length velocity stacks the may change some of the behaviour when refitted. The SV's don't draw air through these, as they use a seperate air intake per cylinder !

I'm sure the 6th gen manual does not say set level vacuum, it does say within +/- 10 or 20 mmHg, but does NOT prescribe which cylinders should be set to what setting, like the 5th gen one does !

Anyone that looks at the 5th gen settings, please note the reference cylinder has changed between the 5th & 6th gen, so adjust accordingly.

But good work that man :)

[HighSideNZ]

Yes you are right in what you outline but the SV's are in play until the throttle is about 4% open.

At that stage the butterflies overcome the volume of air coming in via the SV's, hence why they have the effect that they do in the transition from closed throttle to partial open.

Again you are right, the air path for the SV's is outside of the main throttle throats and the bell mouths do not have any impact on the air drawn in to the slow circuits controlled by the SV's.

The manual states a tolerance of 20mm/hg and says nothing regarding how this should be attained but I'm pretty sure most people have taken this to be "all the same" within the tolerance.

Basically, all I'm saying is that there is a co-relationship between how the SV's are set and how the throttle transitions from closed to partial throttle.

And what affect this has on tractability of the whole motorcycle.

I'm not saying this is the be all to end all, but it is worth investigating.

Cheers

Phil

[Mohawk]

I'm with you, I always found it strange that 6th & 5th had different setups ! :)

[nearfreezing]

HighSideNZ, great post. I've been wondering how to sync the valves and from what I've read it seems the 5th generation set-up is the smoothest. What other configurations did you try and what were the results?

[HighSideNZ]

When I was experimenting I started with a standard flat sync, then when directly to the Gen 5 setup. Found a difference straight away.

Next I went to +/-15mm/hg using the same settings as per the Gen 5, as in what valves were set to what. Felt there was a bit more of an improvement.

Thought I'd keep going as it didn't seem to be having any detrimental effect.

So went up another 5mm and kept the same valve spacing's as before.

At 20mm I thought I'd try changing the valves around dependent upon the firing order.

This presented the best so far.

Phil

[digiman]

Found this thread on bikersoracle: http://www.bikersoracle.com/vfr/forum/showthread.php?t=44763&pp=15

They managed to get a translation of the japanese service manual:

The answer is................... from the Japanese manual..............

Rod san,

Thanks for your note! I found the 5 way connector instruction in the starter valve section. It reads:-

Remove the air cleaner case, remove the Pb sensor from it. Put the vacuum tube and coupler to the Pb sensor.

Take off the vacuum connected to each cylinders from the 5 way joint above the throttle body.
Connect each (four) vacuum tube to four manometers.

Remove the air-suction-tube of the secondly air intake device to the lead-valve-cover above the rear cylinder head, then put the cover and plug the lead-valve-cover.

Warm up the engine and set the gear neutral. Use the revolution meter at least 50 rpm reading.
Idling should be: 1,200 +/- 100 rpm

Adjust each intake vacuum pressure same to No.4 cylinder pressure. No.4 starter valve is the base-starter-valve and it is not able to adjust.

This is a draft translation. Sorry I must go out now. I will check the contents again. If you need further section, do not hesitate to ask me!

Best regards,
Kiyo


So, hopefully, this is the definitive answer as to the starter valve settings

[Switchblade]

Found this thread on bikersoracle: http://www.bikersoracle.com/vfr/forum/showthread.php?t=44763&pp=15

They managed to get a translation of the japanese service manual:

The answer is................... from the Japanese manual..............

Rod san,

Thanks for your note! I found the 5 way connector instruction in the starter valve section. It reads:-

Remove the air cleaner case, remove the Pb sensor from it. Put the vacuum tube and coupler to the Pb sensor.

Take off the vacuum connected to each cylinders from the 5 way joint above the throttle body.

Connect each (four) vacuum tube to four manometers.

Remove the air-suction-tube of the secondly air intake device to the lead-valve-cover above the rear cylinder head, then put the cover and plug the lead-valve-cover.

Warm up the engine and set the gear neutral. Use the revolution meter at least 50 rpm reading.

Idling should be: 1,200 +/- 100 rpm

Adjust each intake vacuum pressure same to No.4 cylinder pressure. No.4 starter valve is the base-starter-valve and it is not able to adjust.

This is a draft translation. Sorry I must go out now. I will check the contents again. If you need further section, do not hesitate to ask me!

Best regards,

Kiyo

So, hopefully, this is the definitive answer as to the starter valve settings

I also notice a guy who responded that he installed a header and solved all of his problems.

i have often thought the cat had something to do the fueling problem.

[vfr350]

So would the same increase on a 5th gen produce similar results?

[HighSideNZ]

So reading the Japanese translation, it is saying that ALL 4 vales are set the same.

This is what we have been reading re the Gen 6 all along and from my finding I do not believe this is correct.

Also, what Switchblade is saying re the headers and the cat, I'm running a set of Delkevic headers and LeoVince SBK mid pipe and cans.

I this these make a difference but nowhere near as much as the starter valve settings.

Cheers

Phil

[Skids]

So reading the Japanese translation, it is saying that ALL 4 vales are set the same.

This is what we have been reading re the Gen 6 all along and from my finding I do not believe this is correct.

Also, what Switchblade is saying re the headers and the cat, I'm running a set of Delkevic headers and LeoVince SBK mid pipe and cans.

I this these make a difference but nowhere near as much as the starter valve settings.

Cheers

Phil

Without wishing to sound dismissive, what makes you think your way is better than the one designated by Honda themselves? Is there any downside or detrimental effect by changing the SV balance as you suggest that you may not be aware of?

Just thinking out loud here.

[Switchblade]

Got to think the balanced approach is better .

[HighSideNZ]

Honestly, as I said a number of posts back, "food for thought"

I'm sticking with what I've found, but it's up to everyone to make there own decision.

Honda, and any other manufacturer do make mistakes, or make production decisions based on cost or other factors.

Look at what they did with the overall fueling of the VFR. It's a dogs breakfast and they supposedly are the "experts"

Same with Honda and cam chain tensioners since the 1970's

Sorry but the argument that Honda "knows best" doesn't hold water in my experience.

Again, my thoughts and opinions only

Cheers

Phil

[Skids]

Honestly, as I said a number of posts back, "food for thought"

I'm sticking with what I've found, but it's up to everyone to make there own decision.

Honda, and any other manufacturer do make mistakes, or make production decisions based on cost or other factors.

Look at what they did with the overall fueling of the VFR. It's a dogs breakfast and they supposedly are the "experts"

Same with Honda and cam chain tensioners since the 1970's

Sorry but the argument that Honda "knows best" doesn't hold water in my experience.

Again, my thoughts and opinions only

Cheers

Phil

True enough, but what do you think are the downsides or harmful effects, if any, of balancing the SVs the way you describe?

I've done the snorkel/PAIR isolation/flapper valve/O2 eliminator mods and low down the throttle on my 08 is beautiful now. Very smooth, hardly any jerkiness at all, 30mph/2500rpm in 5th is easy, 1st gear throttle only small turns are doable too.

[HighSideNZ]

I've honestly not found a downside so far.

We are talking about the effect on the 0 to 4% throttle and I too can now ride round and round in circles with great low speed throttle control. Got to be all pluses in my book.

[Skids]

I've honestly not found a downside so far.

We are talking about the effect on the 0 to 4% throttle and I too can now ride round and round in circles with great low speed throttle control. Got to be all pluses in my book.

In that case, I might try that next time I balance the SVs (which should be soon as it's on the ramp for an 8k service).

[Lint]

Ok, so, on my bike, partially gutted exhaust, unplugged flapper, unplugged pair, snorkel removed to get a little engine noise.

I synced my starter valves to what I am guessing is close to the modified 5th gen as covered in this topic, that is, about 20 apart.

I followed the service manual, I.e. MAP connected, plugged the hoses going to the pair valves and then adjusted.

It does seem smoother and there is a lot less of a snatchy throttle just off idle. I do definitely like it, however, as I haven't tried it yet with them adjusted per 6th gen specs, I can't tell if there is any real difference between the two.

[Switchblade]

Did mine today again . number 3 was way off ...