Filthy PAIR valves

[Whooshka]

And how exactly did removing the PAIR valves do that?

Consider that during deceleration with PAIRs installed there is no air entering the exhaust manifold. And with the PAIRs removed there also is no air entering the exhaust manifold. No large bangs (afterburn) either way. And if there was some decel burble before the PAIRectomy there will be some after... nothing has changed in the exhaust manifold.

On the ST1100 the next suspect for afterburn would be the air cut-off valves.

Sorry... if you want to remove the PAIR valves and pollute all the time instead of just during engine braking, just do it! Please don’t rationalize your actions and perpetuate erroneous info.

Again... respectfully, John

John I don't know how it works, I just know it does. With no air getting pumped into the exhaust there is no burning hence no popping. I don't need any scientific data, just my ears. Perhaps they work opposite of what you believe? I'm not rationalizing my actions nor perpetuating erroneous info. And you refer to the exhaust manifold. As far as I know on the 13 there is no separate manifold and header. The exhaust system starts right at the header straight to the muffler, somewhere in-between the exhaust is ignited causing the popping. No erroneous info there.

No disrespect intended.

correct in that when you remove the cats from a bike ( assuming there is no down stream O2 ) with an air system the air system becomes redundant. on a bike with cats the air system adds air to help reignite unburned hydrocarbons which also keeps the cats hot which helps with cat efficiency. on the ST this is a HUGE creator of heat on a bike that already has heat problems if you take out the cats the pop pop noise your hearing is the igniting of the unburned hydrocarbons so when you remove the air system the unburned hydrocarbons do not reignite but just leave making the bike smell "sweeter" LOL
I should note that bikes with cats NEED the extra air to keep the cats hot or they will eventually clog

there are lots of ways to disable the air systems. On my ST I just took off the valve and hose then installed caps in the reed valve covers. This was the free option

On my old ZRX guys would remove the hoses coming out of the plates and JB Weld in pennies. Called it the 2 cent block off plates.

 

[Catmandu2]

On my old ZRX guys would remove the hoses coming out of the plates and JB Weld in pennies. Called it the 2 cent block off plates.

Kits I have seen (for various bikes),, include a couple of marbles that you just shove in the pair hose, for the same effect. Saves on JB weld,, and pennies (what's a penny anyway,, we got rid of those long ago !!). CAt'

 

[mello dude]

Kits I have seen (for various bikes),, include a couple of marbles that you just shove in the pair hose, for the same effect. Saves on JB weld,, and pennies (what's a penny anyway,, we got rid of those long ago !!). CAt'

Kinda the reason why I make laser cut plates.... I dont like to do anything half azzed.... The final installation looks professional.....all hoses go round file as well as the air pump...no marbles required.

 

[thekaz]

Do I understand that to mean it’s not advisable to remove PAIR systems from catalytic converter quipped engines?

John

In general yes .... it would be better to remove the cats and then the air systems. There are some cats that can stay hot enough on their own to stay unclogged like several fords applications .....

 

[John OoSTerhuis]

John I don't know how it works,

Um... er... please read the description of the “secondary air supply system” in the ST1300 service manual. Clearly explained there. It is most likely in Chapter 1. Kevin Elliot posted it up verbatim when this came up some time ago, but I can’t find it right now.

With no air getting pumped into the exhaust there is no burning hence no popping.

Exactly! The same condition as when the PAIR valves have cut off the filtered air during deceleration. If the PAIR valves have been removed then of course no air is being drawn in either.

Decel popping on non-PAIRed engines happens to some degree. It’s normal.

Perhaps they work opposite of what you believe?

No. Again, read the manual.

I'm not rationalizing my actions nor perpetuating erroneous info.

Well, you seem to be still holding on to the mistaken belief that removing the PAIRs somehow affects decel ‘popping,’ but can’t explain how.

As far as I know on the 13 there is no separate manifold and header.

You are correct, I should use exhaust “port”, not “manifold.” Each, separate, cylinder exhaust port.

No disrespect intended.

None taken, nor intended.

John

 

[RaYzerman]

Well all this discussion prompted me to consult several bike service manuals and try to further my knowledge of PAIR systems.... firstly, John is quite correct in how the ST1100 systems work, but in the ongoing evolution of things and as emission standards get tighter, later systems use a solenoid to cut off/on the flow of air, ECU controlled (e.g., ST1300). There is no pump (as we had on 70's cars), the air passively flows into the exhaust ports and is drawn in by negative pressure caused by exhaust gasses flowing out the exhaust. This solenoid is controlled by the ECU based on whatever parameters have to be met (air temp, coolant temp, vacuum, rpm, etc., etc.). Oddly enough I read the greatest negative exhaust pressure is at idle, which I thought was interesting. But to keep it simple, there isn't any good detailed info I could find, and the ECU will do it's thing based on how the manufacturer programmed it to meet the emission standard of the day.
I will take a stabbing guess with ECU controlled systems there might be air entering on decel, as most of the popping seems to go away with a blocked off PAIR system or perhaps it could be simply "catching up" with air already in there from a previous activation.... who knows, technical info isn't readily available. The ST's are so quiet, you likely don't notice, unless you have a louder aftermarket exhaust but have cat's upstream..... wait, are aftermarket exhausts legal.. don't answer that, LOL.
Removing/blocking off these systems has been done to clean up the engine bay (particularly on in-line 4's) and lose a pound of hoses, clamps and a solenoid. There is no performance gain but I think we'd agree there is an effect on emissions... OBDII came into being with Euro4 emissions on a lot of bikes, and I know of one which will record an error code if the PAIR solenoid is not present. Euro5 is required for 2021 in Europe which may cause them to lose some bikes from the market... FJR for one. I think this has also spawned the development of smaller displacement bikes that can meet Euro5, just an opinion.

 

[TerryS]

Oddly enough I read the greatest negative exhaust pressure is at idle, which I thought was interesting.

That would be due to the Bernoulli effect where the pressure exerted by a gas drops as the velocity increases; the same reason a carburetor generates a vacuum to suck fuel into the airstream.

The following is a section from the 1988 Honda Common Service manual on PAIR; as John states, these were controlled by the intake vacuum signal on carbed bikes (shutting the PAIR airflow under high vacuum specifically to reduce the afterburn popping), whereas the 1300 uses a solenoid that is driven by the ECU.


The 1300 manual is silent on exactly when the PAIR system is functioning but given the FI system's ability to completely cut fueling on a closed throttle it is possible the system might remain open under a closed throttle on the grounds that more oxygen in the exhaust will reduce unburnt hydrocarbons. This is from the VFR800 manual:

What this does tell me is that the PAIR valve is CLOSED by a signal from the ECM or in other words, it defaults to open, so just unplugging the solenoid will not disable the system.

Actually my stock ST has always given a bit of a pop on over-run when I blip the throttle at a standstill, something none of my other bikes have ever done. Is this something others experience with the 1300? I've never heard it do that when riding however. I guess I should try it with the PAIR disabled and see what I get...

 

[Whooshka]

Um... er... please read the description of the “secondary air supply system” in the ST1300 service manual. Clearly explained there. It is most likely in Chapter 1. Kevin Elliot posted it up verbatim when this came up some time ago, but I can’t find it right now.
Exactly! The same condition as when the PAIR valves have cut off the filtered air during deceleration. If the PAIR valves have been removed then of course no air is being drawn in either.

Decel popping on non-PAIRed engines happens to some degree. It’s normal.
No. Again, read the manual.
Well, you seem to be still holding on to the mistaken belief that removing the PAIRs somehow affects decel ‘popping,’ but can’t explain how.
You are correct, I should use exhaust “port”, not “manifold.” Each, separate, cylinder exhaust port.
None taken, nor intended.

John

You seem pretty adamant about it, especially after admitting you don't know about how the 1300 works. And just because I don't know how it works doesn't mean it isn't working. My ears tell me so. Go back and reread what I said. It cured 90% of the popping. There are posts all over the board saying removing the PAIR system stops popping. We must ALL be wrong!

The PAIR solenoid opens on deceleration to allow air to passively flow into the exhaust to help with unburned gasses. You may hear popping in the exhaust occasionally as a result. At other times the reeds close with exhaust pressure to prevent backflow. Completely normal to carbon up, gently clean and reinstall or as some do, remove the PAIR system and replace with block-off plates.

Thank you!

Well all this discussion prompted me to consult several bike service manuals and try to further my knowledge of PAIR systems.... firstly, John is quite correct in how the ST1100 systems work, but in the ongoing evolution of things and as emission standards get tighter, later systems use a solenoid to cut off/on the flow of air, ECU controlled (e.g., ST1300). There is no pump (as we had on 70's cars), the air passively flows into the exhaust ports and is drawn in by negative pressure caused by exhaust gasses flowing out the exhaust. This solenoid is controlled by the ECU based on whatever parameters have to be met (air temp, coolant temp, vacuum, rpm, etc., etc.). Oddly enough I read the greatest negative exhaust pressure is at idle, which I thought was interesting. But to keep it simple, there isn't any good detailed info I could find, and the ECU will do it's thing based on how the manufacturer programmed it to meet the emission standard of the day.
I will take a stabbing guess with ECU controlled systems there might be air entering on decel, as most of the popping seems to go away with a blocked off PAIR system or perhaps it could be simply "catching up" with air already in there from a previous activation.... who knows, technical info isn't readily available. The ST's are so quiet, you likely don't notice, unless you have a louder aftermarket exhaust but have cat's upstream..... wait, are aftermarket exhausts legal.. don't answer that, LOL.
Removing/blocking off these systems has been done to clean up the engine bay (particularly on in-line 4's) and lose a pound of hoses, clamps and a solenoid. There is no performance gain but I think we'd agree there is an effect on emissions... OBDII came into being with Euro4 emissions on a lot of bikes, and I know of one which will record an error code if the PAIR solenoid is not present. Euro5 is required for 2021 in Europe which may cause them to lose some bikes from the market... FJR for one. I think this has also spawned the development of smaller displacement bikes that can meet Euro5, just an opinion.

THANKS AGAIN!!!! Perhaps if Mr. O sees it from somebody else he'll open up his mind.

 

[Whooshka]

Great info in that post. Thanks TerryS.

Big difference the way these air systems work in a carbed bike vs injected.

 

[John OoSTerhuis]

Seems to me that when the ST1300 PAIR solenoid is “tripped” - all air flow to the exhaust ports is stopped. FWIW

Has there ever been a reported failure of the ST1300 secondary air supply system? PAIR failure? Has the Republic of Kalifornia ever failed a dePAIRed ST1300 for emissions? OK, that last one was facetious.

OK, maybe not so silly... trip the solenoid and stick an exhaust gases emissions probe in the muffler. Check the read outs vs without the PAIR valve closed. JAT

Anyway, I’m done with the discussion. Ya’ll can believe what you want.

John

 

[Whooshka]

………...
Exactly! The same condition as when the PAIR valves have cut off the filtered air during deceleration. If the PAIR valves have been removed then of course no air is being drawn in either.
……………………….

John

[QUOTE="John OoSTerhuis, post: 2192613, member: 278

Seems to me that when the ST1300 PAIR solenoid is “tripped” - all air flow to the exhaust ports is stopped. FWIW
………………………..

I’m done with the discussion. Ya’ll can believe what you want.

John
[/QUOTE]

Look!!!! You said it yourself! Removing the PAIR valves eliminates fresh filtered air being introduced into the exhaust, thus no burning of unspent gasses, thus NO POPPING!!!!

Way to back out without admitting you just might be wrong. And all of us who have removed the PAIR with aftermarket exhaust are just hearing things. Or not hearing things, as the case may be. At least our ears are open.

 

[John OoSTerhuis]

THANKS AGAIN!!!! Perhaps if Mr. O sees it from somebody else he'll open up his mind.

Hmm... you quote RaYzerman twice. In his first one he’s wrong about when the PAIR opens and closes. Then you praise his second quote, but what I took away about popping reduction was:

I will take a stabbing guess...
there might be...
popping seems to go away...
it could be "catching up”...
who knows

John

 

[John OoSTerhuis]

Look!!!! You said it yourself! Removing the PAIR valves eliminates fresh filtered air being introduced into the exhaust, thus no burning of unspent gasses, thus NO POPPING!!!!

I didn’t say it stopped popping. Afterburn is prevented. I said that if you had decel popping with a PAIRed ST you will still have it after a PAIRectomy. The small amount of air still present in the exhaust from the combustion chamber that causes the popping is the same, PAIR or no PAIR; IOW, no additional air has entered at the exhaust port, only what came through the engine’s regular air intake and remained unused after the combustion cycle/stroke.

I also said a couple of times that decel popping was normal in non-PAIRed engines.

Way to back out without admitting you just might be wrong.

I admit no such thing. PAIR valves when closed during decel (vacuum or solenoid activated) stop secondary air from being drawn into the exhaust ports to prevent afterburn. If there is decel popping, removing the PAIR will not change the conditions that cause that.

John

 

[John OoSTerhuis]

AFTERBURN: serious, damaging fuel/air explosions in the exhaust. Often referred to erroneously as “backfire*.” Caused by the presence of excessive amounts of raw unburned gas dumped into the hot exhaust with enough air present to trigger a violent explosion. Think “pow!” or “kablam!” Turn your ignition switch off while underway and then back on after say.. a five count.

Possibly a PAIR that didn’t close... a hole in the exhaust pipe... Check the manual’s troubleshooting section.

DECEL BURBLE/POPPING: normal mini firing of unburned gas in the exhaust during deceleration conditions like engine braking.

*Backfire refers to fuel-air explosion in the intake manifold. The fuel/air mixture is ignited before the intake valve closes.

 

[Catmandu2]

So I gather from all these good discussions that, since I have replaced my oem mufflers/cat's with Del's, I don't really need my pair system anymore. However,,, before I remove anything, I should consider that the bike is running great,, and it is not re-burning much,,, no backfire either,, and it is not running hot. The pair valves are functioning, and although there are no cat's, the re-burn that does occur (it not obtrusive) is actually consuming some raw hydrocarbons, which might otherwise just exit to atmosphere. So the Pair is still doing something good. Removal/disable would provide no real noticeable benefit,, except possibly the elimination of oil mist in the intake box, by the Pair's vacuum port. Have I got that about right ?? CAt'

 

[Whooshka]

So I gather from all these good discussions that, since I have replaced my oem mufflers/cat's with Del's, I don't really need my pair system anymore. However,,, before I remove anything, I should consider that the bike is running great,, and it is not re-burning much,,, no backfire either,, and it is not running hot. The pair valves are functioning, and although there are no cat's, the re-burn that does occur (it not obtrusive) is actually consuming some raw hydrocarbons, which might otherwise just exit to atmosphere. So the Pair is still doing something good. Removal/disable would provide no real noticeable benefit,, except possibly the elimination of oil mist in the intake box, by the Pair's vacuum port. Have I got that about right ?? CAt'

You're on the right track. When I installed my 2 Brothers pipes The popping (not backfiring) in the exhaust was really annoying. It was there with the stock mufflers too I'm sure, but since they are restrictive and designed for quiet I didn't notice it. With the 2 Bros it was obvious. I pulled out the PAIR system, like so many others, and the popping was almost all gone. We can't all be imagining things.

Yet there are others who say they are done with this conversation, who have no experience with this on a 1300, who just can't let go and can't acknowledge what those who have pulled their PAIR have experienced. The choice is yours.

 

[thekaz]

Big difference the way these air systems work in a carbed bike vs injected.

the understatement of this thread for sure

 

[thekaz]

PAIR valves when closed during decel .......

John

Considering there are no published ST1300 fuel maps and you do not have any data logging to prove it ??? well

 

[thekaz]

you can tell for sure its winter and lots of us are not riding as much LOL

 

[Whooshka]

you can tell for sure its winter and lots of us are not riding as much LOL

No, THAT'S the understatement of this thread right there.

Please understand I'm not trying to stir the pot and didn't mean to side track the thread. John O is a very knowledgeable and respected member here. It's just a pet peeve of mine when somebody argues a point about something they admit to not knowing and has no personal experience with. If I'm wrong about something I'll be the first to admit it. But my experience, as well as others, with this tells me otherwise.