Crazy bad gas mileage!!!

[Guest]

So I plugged my Pair Valve electrical connector back in thus enabling the pair valves to work again.

I think Dawson is on to something. Instead of getting max 150 miles to a tank i am up to 170+ and not even blinking yet. On my 2002 if you disconnect the pair valve connection it leaves the pair valves open thus making the O2 sensor think the bike is running lean thus dumping more fuel in the cylinders.

If you are going to disable the pair valves, do it right and take them off and block them off.

[Guest]

I always thought unplugged pair valves were disabled and not letting air thru the exhaust?

I honestly never researched this, but was going by what I've read on here---->http://johnny.chadda.se/article/pair-and-flapper-mod-with-bonus-snorkel-mod-for-vfr/

Quote:"What is happening is that when the bike is running, the pair is opening to blast fresh air into the exhaust system. This was done to clean up the bikes emissions. This systems worked fine on all models. Even carb models have this system fitted. When the VFR went to the first fuel injected model the PAIR valve was still used again to clean up emissions without any problems. Then the VTEC model came along and it all went wrong. The reason for this is that the VTEC model had an O2 sensor fitted in the exhaust. What happens is that the PAIR valve is working pretty much from idle speed blasting fresh air into the exhaust system. The fresh air entering the exhaust is picked up by the O2 sensor which then thinks the bike is running lean (around 19:1) so sends a signal to the ECU to richen up the fuel mixture. The ECU is now pouring as much fuel into the engine as it can because the O2 sensor thinks its still running lean. The real fuel/air ratio being poured into the bike is now around 11:1 making the bike hard to ride and resulting in the snatchy throttle response we have all been talking about."

Either way, I unplugged my pair valves to get rid of the mid range flat spot and it worked. I'm still getting decent mileage 40-41'ish so I'll leave it be for now.

I'm glad your mileage is improving.

[Guest]

I always thought unplugged pair valves were disabled and not letting air thru the exhaust?

I honestly never researched this, but was going by what I've read on here---->http://johnny.chadda.se/article/pair-and-flapper-mod-with-bonus-snorkel-mod-for-vfr/

Quote:"What is happening is that when the bike is running, the pair is opening to blast fresh air into the exhaust system. This was done to clean up the bikes emissions. This systems worked fine on all models. Even carb models have this system fitted. When the VFR went to the first fuel injected model the PAIR valve was still used again to clean up emissions without any problems. Then the VTEC model came along and it all went wrong. The reason for this is that the VTEC model had an O2 sensor fitted in the exhaust. What happens is that the PAIR valve is working pretty much from idle speed blasting fresh air into the exhaust system. The fresh air entering the exhaust is picked up by the O2 sensor which then thinks the bike is running lean (around 19:1) so sends a signal to the ECU to richen up the fuel mixture. The ECU is now pouring as much fuel into the engine as it can because the O2 sensor thinks its still running lean. The real fuel/air ratio being poured into the bike is now around 11:1 making the bike hard to ride and resulting in the snatchy throttle response we have all been talking about."

Either way, I unplugged my pair valves to get rid of the mid range flat spot and it worked. I'm still getting decent mileage 40-41'ish so I'll leave it be for now.

I'm glad your mileage is improving.

Yeah, that's the exact site i read to do the "pair valve disable." Turns out, it definitely ruins your fuel economy. The pair valves when open do make the bike run rich when it is in open (or closed?) loop. I definitely got much worse fuel economy with it simply unplugged. It makes me believe that it is normally in the open position and closed by the ecu instead of it being in the closed and opened by the ecu.

This would also explain why the snatchiness is cured by unplugging the pair valves...its dumping fuel in the cylinders. This mod might work if you actually plug the vacuum line to the pair valves...

[AndyB]

I just used a marble in the line between the airbox and the PAIR pump. Kaldek has a post on here with pictures somewhere. I left the parts on the bike so I would not have to put caps over the ends.

[Veefer800Canuck]

I just used a marble in the line between the airbox and the PAIR pump. Kaldek has a post on here with pictures somewhere. I left the parts on the bike so I would not have to put caps over the ends.

this is a great idea because it is totally reversible, should you ever sell the bike.

[AndyB]

this is a great idea because it is totally reversible, should you ever sell the bike.

I agree with the logic of this but I hope I never sell this bike.

[y3v]

I just used a marble in the line between the airbox and the PAIR pump. Kaldek has a post on here with pictures somewhere. I left the parts on the bike so I would not have to put caps over the ends.

Link please?

Definitely want to do this.

[AndyB]

http://www.vfrdiscussion.com/forum/index.php/topic/58258-pair-valve-disabling/?hl=marble

[y3v]

http://www.vfrdiscussion.com/forum/index.php/topic/58258-pair-valve-disabling/?hl=marble

Thanks and what do you guys usually get on a full tank of gas (before it starts blinking).

I got ~155 this last fill up.

[AndyB]

I don't recall but I will be doing a long run tomorrow so I should know soon.

[Switchblade]

http://www.vfrdiscussion.com/forum/index.php/topic/58258-pair-valve-disabling/?hl=marble

Thanks and what do you guys usually get on a full tank of gas (before it starts blinking).

I got ~155 this last fill up.

Some where's between 170-180 miles and PAIR system is completely removed.

[AndyB]

I was at 170 today and it had not started to blink.

[Guest]

Since i plugged my pair valve in i am back up to 160 with 1 bar but not blinking. before i was 140-150 on 1 bar and blinking!

[donnykaboom]

your engine is designed to use any gasoline that has a pump octane number of 86 or higher.

VFR800 owner's manual 2003 page 97 (servicing your honda)

[Switchblade]

"ODO not reading correctly (-1+2 sprockets <--thought I had stock originally, but when I went to change/upgrade them, I found that it had already been done, which explains the early low readings in the 30's, but not the 22)

2: Valve check needed

3: A black bike in Oklahoma during 115 degree summers, with no CA setup, =fuel evaporation."

I think you found it.

[kaldek]

I did some measurements on my bike when it had an '06 ECU on it and confirmed that the PAIR valves are always open unless the ECU goes into closed loop mode. So if you have put in O2 eliminators, the bike never goes closed loop and you would not suffer any fuel consumption issues by disconnecting the PAIR valve solenoid.

If you plug the PAIR valves or block them with plates, they are obviously always closed and you need to tweak the idle speed to compensate for the difference in airflow. Some folks (like myself) also found that the engine was more troublesome with PAIR disabled - particularly on my '06 ECU.

[Kirdro]

I know, I know, I'm the worst OP ever. Grad college does take over your life. For those who responded, and continued the discussion, THANK YOU! Now, to resurrect this post for an update.

Cause of Poor Mileage:

Thermostat Failure.

Thermo-switch Failure.

Factors Tested and Eliminated:

While the 91 octane is usually the victim of a witch hunt with the VFR, it is not a contributing factor in this case.

Valve Check: Did it, no adjustments necessary. (28k miles)

Speedometer: Speedo Healer corrected, checked with GPS, no issues. Accurate.

Odometer: Speedo Healer corrected.

Anti-California (PAIR, etc.): Contributes ~ -3 or -4 mpg, but not ~15-20

Throttle Happy: Long distance rides under 6800rpm still showed poor fuel performance.

PCIII Map: Multiple maps, disconnected, tested, etc. Initial map was designed for fuel performance when needed, smoothing out the surge, and higher power over 6800rpm. No siginificant changes between stock fuel performance and modified.

Thanks again for the discussion, hopefully this finally puts this one to rest, and helps with future diagnosis.

[adamv]

But seriously - thank for getting back with the information - no doubt that this will help someone else in time to come - and glad to see you've got it resolved. Better late than never. :)

[LeakingLewis]

Let me jump in and ask a dumb question. How do you diagnose a failed thermostat and a failed thermostat switch?

[Otaylor38]

I've just had a quick read at the first page of this.

What octane rated fuel are you guys using? On the first page, 91 octane is mentioned and thats premium?

Here in the UK, 95 is normal, 97 is premium and 99 is available in some places.

[Terry]

Let me jump in and ask a dumb question. How do you diagnose a failed thermostat and a failed thermostat switch?

The thermostat should remain closed below 78-odd C, so during warm up there should be no warm water passing through the rads, they should stay cold until the temp gauge gets to 78-80. So if you radiators start to warm up below this temp, the thermostat is probably stuck open

Not sure what you mean by a thermostat switch...the only switch in the cooling system is the fan switch on the front of the left radiator. Assuming the fan motor works, the fan should come on when the coolant temp exceeds about 102C.

Sent from my iPhone using Tapatalk

[Kirdro]

Let me jump in and ask a dumb question. How do you diagnose a failed thermostat and a failed thermostat switch?

The thermostat should remain closed below 78-odd C, so during warm up there should be no warm water passing through the rads, they should stay cold until the temp gauge gets to 78-80. So if you radiators start to warm up below this temp, the thermostat is probably stuck open

Not sure what you mean by a thermostat switch...the only switch in the cooling system is the fan switch on the front of the left radiator. Assuming the fan motor works, the fan should come on when the coolant temp exceeds about 102C.

Sent from my iPhone using Tapatalk

91 Octane is about as high as is availabe most places here (Oklahoma).

I'd been told the bike runs hot normally, so when it was averaging 200F+ I never thought anything was out of place. This last summer however, I would start leaking from the rad overflow whenever I was in city traffic. The stat was definitely shot, and the replacement has done much better. The thermostatic switch is the one mentioned. It's for the fan, and as stated by Terry, should kick on the fan at a certain temp. Mine would not kick on, and was simple to diagnose the switch as the issue rather than the fan motory by bypassing the switch and grounding the fan to the frame. When the fan is grounded, it will run constantly, indicating that the switch was faulty, not the fan.

[kaldek]

I've just had a quick read at the first page of this.

What octane rated fuel are you guys using? On the first page, 91 octane is mentioned and thats premium?

Here in the UK, 95 is normal, 97 is premium and 99 is available in some places.

USA uses different rating system - RON+MON/2. It's called AKI or the Anti-Knock index.

Ergo, 87 US Octane is roughly 91 RON. So 91 US Octane is roughly 95 RON.

[Otaylor38]

I've just had a quick read at the first page of this.

What octane rated fuel are you guys using? On the first page, 91 octane is mentioned and thats premium?

Here in the UK, 95 is normal, 97 is premium and 99 is available in some places.

USA uses different rating system - RON+MON/2. It's called AKI or the Anti-Knock index.

Ergo, 87 US Octane is roughly 91 RON. So 91 US Octane is roughly 95 RON.

Ooh i see. That makes more sense. Totally threw me that did. Haha.

Cheers.