Crazy bad gas mileage!!!

So I filled up today, and am sitting at 22.5mpg. I've never gotten fantastic gas mileage out of my vfr, but this was the worst it's ever been! Most of my riding has been around town, and I've averaged around 28mpg and highways in the low 30's (31-33). So, list of mods....

De-Californication

Pair/Snorkel removal

O2 sensor disabled (resistors)

Cat-back Scorpion exhaust

PCIII (cozy's)

Running temp ranges:

180-210

Fuel:

Premium 91

Any suggestions?

Ditch the premium and go with the 87. Doesnt make sense to me, but I have heard it works.

Keeping your rpm below the VTEC range greatly improves mpg.

BillyZ

Ditch the premium and go with the 87. Doesnt make sense to me, but I have heard it works.

Your temperatures look good, so Id say the map is too rich for your bike. Id expect to give up a couple mpg's with a power commander, but the map is going to make a Huge difference too.

When I first put in my PCV I noticed a drop in MPG but never that significant amount of difference. I also heard that running 87 Octane helps but I have yet to try it. Maybe the next fill up I'll give it a go. Unless it starts detonating, the worse that can happen is that I save money, at least 10 cents/gallon at most stations.

The common practice back in the day when there were an abundance of octane choices at the pump, the way it was done was to put in the high-test and see what happens(Knock or no knock), if no knock then go down a grade till it did knock, then go up one grade, as there's no advantage to running any higher than that............ The best time to do this was in the hotest part of the summer..... Or just not learn anything from history. :laughing6-hehe:

The vfr seems to do okay on 87 octane, but Ive run all 3 grades and it really doesnt make a difference on milege.

Run a few more tanks before you worry too much. Could just have been a stale tank of fuel at your last fill up.

And your wasting you cash on 91oc fuel. 2 reasons.

1. 6th gen doesn't call for it, like everyone has said.

2. Tank is only 22liters a multi-grade gas pump can hold between 10-12liters of fuel in all of the pipe work. So unless your getting gas behind someone that used 91oc your getting half a tank of whatever the guy before you bought.

Do the plugs and air filter check out as good? Also, if the gas mileage issue started with the mods, double check all vacuum hoses, etc are all connected properly.

Buy the proper octane for your vehicle

Contrary to popular belief more octane doesn't make your engine perform better nor is the gasoline any cleaner than lower octane ratings. Octane is a burn retardant, that means that it slows down the rate of combustion (burning) for gasoline. Octane ratings higher than those required by your engine actually decrease performance, albeit very slightly and probably imperceptively at that, so buying higher octane ratings than needed just wastes money.

I am not reccomending violating your owner's manual requirements, if your owners manual says to use mid grade or high test then by all means do it, don't jeopordize your warranty to save a few cents per gallon, but if you're adding high test because you think it is better gas and your manual doesn't suggest or require it, then you should revisit this logic.

posted by bates on January 04, 2009

this tip works for 85% of voting Fuelly members.

What ambient air temps are you running in? If in cooler temps and you have sticky t-stat issues (like sticking open) and your coolant temps are not getting up past 180 degrees F, the EFI will send extra fuel until the bike "warms up". My bike always gets worse mpg in cooler temps...

Read what Monk said here again, at least 3 times, there is such a misconception out there. This is truth.

Monk

Buy the proper octane for your vehicle

Contrary to popular belief more octane doesn't make your engine perform better nor is the gasoline any cleaner than lower octane ratings. Octane is a burn retardant, that means that it slows down the rate of combustion (burning) for gasoline. Octane ratings higher than those required by your engine actually decrease performance, albeit very slightly and probably imperceptively at that, so buying higher octane ratings than needed just wastes money.

I am not reccomending violating your owner's manual requirements, if your owners manual says to use mid grade or high test then by all means do it, don't jeopordize your warranty to save a few cents per gallon, but if you're adding high test because you think it is better gas and your manual doesn't suggest or require it, then you should revisit this logic.

posted by bates on January 04, 2009

this tip works for 85% of voting Fuelly members.

dallasb

Read what Monk said here again, at least 3 times, there is such a misconception out there. This is truth.

Monk

Buy the proper octane for your vehicle

Contrary to popular belief more octane doesn't make your engine perform better nor is the gasoline any cleaner than lower octane ratings. Octane is a burn retardant, that means that it slows down the rate of combustion (burning) for gasoline. Octane ratings higher than those required by your engine actually decrease performance, albeit very slightly and probably imperceptively at that, so buying higher octane ratings than needed just wastes money.

I am not reccomending violating your owner's manual requirements, if your owners manual says to use mid grade or high test then by all means do it, don't jeopordize your warranty to save a few cents per gallon, but if you're adding high test because you think it is better gas and your manual doesn't suggest or require it, then you should revisit this logic.

posted by bates on January 04, 2009

this tip works for 85% of voting Fuelly members.

The vfr as long as you dont develope alot of carbon raising the compression it does okay on regular. Some of the High test fuels actually have higher level of detergents, even if you cant benefit from the higher octane. Exxon used to be one of those fuels, their Premium had much higher levels of detergent, But this guys problem has nothing to do with the grade of fuel he's running.

Even though its been repeated 10 times.

Make sure the Air Filter doesn't look like this!!

[image: filter]

Remove the Power Commander and see what happens.

Thanks for the suggestions! I definitely don't think it's the high octane though, since I've ran high octane the entire time I've had it. I was more concerned about the recent drastic drop rather than the overall low mileage. Definitely don't have a rat's nest in my air cleaner :) and I swapped out spark plugs a month and a half ago, so likely not them either. I'll double check my map, just in case something screwed up with the power commander and my map switched (it's been about 6 months since I installed cozy's map).

Leaking fuel pressure regulator. Fuel leaks through the diaphragm inside the FPR and into the vacuum signal hose and into the throttle bodies.

You didn't mention the mileage on the bike. Is it high enough to require valve adjustment or starter valve sync? I have the gauges to do the starter valve sync and am only 38 miles away.

Kirdro

So I filled up today, and am sitting at 22.5mpg. I've never gotten fantastic gas mileage out of my vfr, but this was the worst it's ever been! Most of my riding has been around town, and I've averaged around 28mpg and highways in the low 30's (31-33). So, list of mods....

De-Californication

Pair/Snorkel removal

O2 sensor disabled (resistors)

Cat-back Scorpion exhaust

PCIII (cozy's)

Running temp ranges:

180-210

Fuel:

Premium 91

Any suggestions?

Just one.

Check it again.

Many things can contribute to a single fill-up giving a bad mileage result.

Probably the most common is operator error, either in the math or not filling the tank to the same level for each time.

It's been a week, have you filled up again?

Same results?

Up until I noticed it was a 6th gen, I was going to say check for spark. I'm going to suggest it anyways. That's how I managed to get 25mpg on my 96. The wires for my ignition coils came off a couple of them.

CharlesW

Kirdro

Any suggestions?

Just one.

Check it again.

Many things can contribute to a single fill-up giving a bad mileage result.

Probably the most common is operator error, either in the math or not filling the tank to the same level for each time.

This seems likely to me. With only a 5 gallon sample, it's easy for your data to be off. You should average your readings over several fill-ups to be sure. If you filled it all the way to the neck one time, and didn't the next time it could be off. Or one pump was less accurate than another, it's easy to be off by 30%. And maybe you got bad gas. Maybe you're used to 100% gas and you got an ethanol blend.

Veefer800Canuck

Leaking fuel pressure regulator. Fuel leaks through the diaphragm inside the FPR and into the vacuum signal hose and into the throttle bodies.

Are there any symptoms of this Rob, apart from poor economy?

I just filled the bike up this morning, and a quick calculation says I got only 25mpg on the last tank. Admittedly, that was all commuting at often much less than 90km/h, but even so, it's lower than I expected. Admission #2 is apart from changing the oil and checking tyre pressures, I've done no maintenance on the bike this year (haven't even washed it for as long as I can remember). Next up (when/if I ever get time) is to clean or replace the air filter. Checked the plugs last night - they just look like plugs (albeit a bit weird, coz they're iridium NGKs).

Happened to me once. Dropped down into the 30's mpg. Dirty fuel. After I burned through that tank, mileage went back to normal (45-50mpg).

Or what they said up there.

If it's a sudden drop after your last fill, it could just be something simple like a bad tank. *shrug* I'd burn through it all then fill up again and see what happens before you go digging around your innards.

Also, another +1 on the "Ditch the premium." Doesn't make a difference and the VFR is made to run on regular. I ran it on Premium for a while and it actually felt worse.

My $.02

Ian, I've never had a bad FPR myself but you would have bad mileage, fouled plugs and rich smelling exhaust.

It's real easy to lift the tank, remove the vacuum line to the FPR and fire the bike up.

If its leaking, you'll know right away. Depending on how bad it is, you might have to let it run a few minutes.

I have a 2002 recently purchased. 100% stock, about 15K. I checked on the mileage, and see that I am getting 25mpg, thats running mostly highway miles, say-75-90 on the highway and I was keeping RPM's say 6-7.5k. The engine runs hot in the Phoenix summer (say 220-235)) but other VFR guys in town tell me they experience the same.

Any ideas of where to look for an issue, or is there a diagnostic check that would be able to tell why the gas mpg is so bad?

Thanks in advance,

Nick

nickpapp

I have a 2002 recently purchased. 100% stock, about 15K. I checked on the mileage, and see that I am getting 25mpg, thats running mostly highway miles, say-75-90 on the highway and I was keeping RPM's say 6-7.5k. The engine runs hot in the Phoenix summer (say 220-235)) but other VFR guys in town tell me they experience the same.

Any ideas of where to look for an issue, or is there a diagnostic check that would be able to tell why the gas mpg is so bad?

I hate to say this but at 90 miles an hour, the 6th-gen VFR eats fuel. Especially once you click over into VTEC, it's gonna get very thirsty. It actually eats it more than bigger bikes. I've seen back to back Blackbird vs. VFR fuel consumption at 120mp/h where the blackbird was drinking way less than the VFR because it wasn't working anywhere near as hard.

The best "is something wrong check" is to fill up close to a freeway and zero your trip meter, then do a good 100 miles at 60mp/h while keeping the bike in sixth as best you can. Then, get to another gas station and measure how much it takes to fill up. From there you can run the fuel consumed through a consumption calculator.

I'm betting you'll hit 45mpg.

kaldek

nickpapp

I have a 2002 recently purchased. 100% stock, about 15K. I checked on the mileage, and see that I am getting 25mpg, thats running mostly highway miles, say-75-90 on the highway and I was keeping RPM's say 6-7.5k. The engine runs hot in the Phoenix summer (say 220-235)) but other VFR guys in town tell me they experience the same.

Any ideas of where to look for an issue, or is there a diagnostic check that would be able to tell why the gas mpg is so bad?

I hate to say this but at 90 miles an hour, the 6th-gen VFR eats fuel. Especially once you click over into VTEC, it's gonna get very thirsty. It actually eats it more than bigger bikes. I've seen back to back Blackbird vs. VFR fuel consumption at 120mp/h where the blackbird was drinking way less than the VFR because it wasn't working anywhere near as hard.

The best "is something wrong check" is to fill up close to a freeway and zero your trip meter, then do a good 100 miles at 60mp/h while keeping the bike in sixth as best you can. Then, get to another gas station and measure how much it takes to fill up. From there you can run the fuel consumed through a consumption calculator.

I'm betting you'll hit 45mpg.

Im not seeing that, my 06 will run all day at 100 mph and get the lower 40,s mpg wise , if I ride sub 45 mph goatpath roads aggresively, then iits get upper 30's, pure city in stop and go Mid 30's, but overall I stay right around that 40 mpg range.

Back before Gasohaul and with harder compound tires, I used to get mid 40's in the deep hot summer, best was about 46 mpg.

Im pretty sure this guys issue, is the rich map on top of eliminating the 02 sensors which lean the mixture to save fuel.

IM completely stock and thats the REAL differnce UNmodified, MPg wise

nickpapp

I have a 2002 recently purchased. 100% stock, about 15K. I checked on the mileage, and see that I am getting 25mpg, thats running mostly highway miles, say-75-90 on the highway and I was keeping RPM's say 6-7.5k. The engine runs hot in the Phoenix summer (say 220-235)) but other VFR guys in town tell me they experience the same.

Any ideas of where to look for an issue, or is there a diagnostic check that would be able to tell why the gas mpg is so bad?

Thanks in advance,

Nick

Thats weird I utilize very little throttle control( use the entire rpm range at will) and never seen that bad) Id have to be idling alot in stop and go to see the mid 30's. Failed tstats are common, maybe yours is stuck half way open causing higher operating temps and slow warm up I dont know, 220 to 225 degrees in high heat is not abnormal, but if seeing alot of 230 degrees , that is very borderline. Maybe someone installed one of the Fuel pumps, that really up the pressure, and this added pressure is leaking through the fuel injectors. Back a few years ago many were installing high pressure fuel pumps. Turbo city or something like that

nickpapp

I have a 2002 recently purchased. 100% stock, about 15K. I checked on the mileage, and see that I am getting 25mpg, thats running mostly highway miles, say-75-90 on the highway and I was keeping RPM's say 6-7.5k. The engine runs hot in the Phoenix summer (say 220-235)) but other VFR guys in town tell me they experience the same.

Any ideas of where to look for an issue, or is there a diagnostic check that would be able to tell why the gas mpg is so bad?

Thanks in advance,

Nick

Click it up a couple notches out of 4th gear. You're running a good 1,000 rpm higher than you should be at those speeds. At indicated 75mph, my 6th gen is cruising along at 5,000 rpm. At an indicated 95mph, I'm at 6,500 rpm. You're either forgetting you have 5th and 6th, or you have aftermarket sprockets that have geared it down considerably.

However, even playing in the twisties in 3rd, 4th and 5th at around 5k-8k, I still get around 35mpg. Check your calculating method and do several more tank fills and calculations before you panic. Either straddle the bike and hold it upright or pop it up on the center stand so you know it will be 100% full. Fill it to the top and zero your trip meter. Like Kaldek said, ride for at least 100 miles, but I'd go until it starts flashing for low fuel so that your calculation will be a little more accurate. If you're just cruising the highways and interstates you should get close to 200 before needing to fill up. Fill it up the same way you did when you zeroed out the trip meter. Divide the number of miles ridden by the number of gallons you used to refill the tank.

As for the temperature, VFR's are designed to run hot. I've had two 6th gens and see those temps all the time in traffic.

So after extended testing (and a long absence from the forum) I'm resurrecting this thread since the problem still stands.

Here's the update:

4,000 miles: average is still sitting right around 22mpg.

I've gone ahead and completely blocked off the PAIR with plates, and checked and rechecked for vacuum leaks. I think I've narrowed it down to a few possibilities.

1: 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.

Also to note, I have tried regular 87, and no difference, so I've stuck with 91. (Btw, if anyone has noticed, 91 is what the fuel rating printed on the airbox calls for. I do know the owners manual says different, but I thought I'd point that out)

If you have a PCIII, dud you try unplugging it and going back to stock?? You should be getting much better mileage. Did you check different gas stations?? No vtec activation??

Good luck.

C

KirdroSo after extended testing (and a long absence from the forum) I'm resurrecting this thread since the problem still stands.

Here's the update:

4,000 miles: average is still sitting right around 22mpg.

I've gone ahead and completely blocked off the PAIR with plates, and checked and rechecked for vacuum leaks. I think I've narrowed it down to a few possibilities.

1: 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.

Also to note, I have tried regular 87, and no difference, so I've stuck with 91. (Btw, if anyone has noticed, 91 is what the fuel rating printed on the airbox calls for. I do know the owners manual says different, but I thought I'd point that out)

Your mileage would be way off. Keep the revs below 7k on the freeway and it will be better. With that gearing you should be in 6th at highway speeds.

The ODO is easy enough to check. Find a GPS. Zero out your tripometer and GPS at the same time, and go for a ride. I don't think your bad mileage is totally due to your gearing, but it can't help. Especially since it sounds like your just starting to engage the VTEC.

Kirdro3: A black bike in Oklahoma during 115 degree summers, with no CA setup, =fuel evaporation.

It's December. Is this statement still accurate? Either MPG still sucks and this is not relevent, or MPG is (a little?) better and this was a contributor.

Yeah, we had quite a few 100 degree days, but 115 was rarely seen...let's not be overly dramatic...

Evaporation would be more a function of how long you let your bike sit between riding and fill ups I would think?

Oh, definitely hit over 115 a few days this summer. Not as bad as last years 100 days over 100, but still plenty hot. Today it's in the mid 60's, and have even been in the mid 70's within the last month. Yes, it gets hot here. Also remember, the tank does sit above a 215 degree motor. I ride it every day, so not really sitting around, and fuel evaporation would remain constant regardless. Fill-ups are once every 2 weeks. Gonna double check my fuel evap line...

Also:

Vtech engages at normal RPM, and after 145 degrees engine temp.

Multiple stations were checked, both with and without ethanol.

No, have yet to remove PCIII, and really don't want to, too much of a difference in performance. Have tried multiple maps as well, (Other than Cozy's) with little change.

Next check is going to be with a gps, as suggested.

The point I was trying to make regarding ambient temperature was that now that it is not summer and the 115 degree days are over, the bad gas mileage continues so we can probably rule out evaporation. That, and I think you would notice the odor. Never helps to check the lines though.

Sounds like a rich map, gearing changes and maybe o2 eliminates causing the issue? My '07 is bone stock and for me to get over 40 mpg I need to be on the open road using light throttle. Like someone said the vfr is thirsty when in vtech mode but 25 mpg is like race track mileage, sounds like something's not quite right.

My Bking in contrast is a much more powerful (read efficient) motor that easily gets better mileage than my vfr in normal riding. Even commuting in the city the bking gets better mileage but the tiny tank & a frisky throttle hand will drain the tank and get you a ticket!

O2 elimination is mandatory with the PCIII, as it takes over the fuel map. The map's probably not the problem either, it's a popular map, and nobody else is reporting mileage like this after using it. Also, I do keep it well below 6k and 45mph for most of my rides, and at highway speeds, the vtech only kicks in when I'm passing or heading up an on-ramp ;)

Defective PCIII??? Just trying to eliminate all possibilities...

You did look for gas leaks, right?

Good luck.

C

KirdroO2 elimination is mandatory with the PCIII, as it takes over the fuel map. The map's probably not the problem either, it's a popular map, and nobody else is reporting mileage like this after using it. Also, I do keep it well below 6k and 45mph for most of my rides, and at highway speeds, the vtech only kicks in when I'm passing or heading up an on-ramp ;)

If you really want to figure this out, you should not dismiss any possibility out of hand. It could be a corrupted map.

Thread Resurrection!

I did a -1 front sprocket and stock rear sprocket. stock air filter. pair valves disabled (unplugged connector, no plate). flapper disabled. normal running temp 170+. ambient temps from 35-50 degrees.

I have been getting indicated 130-140 miles between fill ups (around 4 gallons). my most recent was 4.6 gallons for indicated 162 miles. because of the sprocket change i know that is about 10% off but dont have gps to check...I figure i am getting mid to high 20mpg maybe low 30mpg.

Know this, i am very tall and weight 300lbs with gear on. I have a touring wind screen which helps...

I get on the vtech a few times every trip which is a few times a week commuting. mostly curvy country roads and highway. quite a few stop and goes. But on days when i slap it on the highway for 80% of the miles i dont notice hardly any difference in mileage.

exhaust doesnt smell great, doesn't smell like gas, just exhaust...since disconnecting pair valves bike has a nice throaty deceleration sound with popping.

I (think I) remember early on with my bike i was getting 180 miles between fill ups before sprocket change.

Reading this thread...either this is normal, or i am running rich...ideas on what i can change? i am thinking about reconnecting the pair valves...would that improve mileage that much?

I had been running the same mods + same gearing (15/43) with the addition of a K&N filter and was seeing 40-41 mpg religiously, 45 with a passenger. ( I guess I'm easier on the throttle)

Lately I've gone back to stock 16/44 gearing due to a 120 mile round trip to work all highway. I still see 39-40mpg on average. I use gps to calculate & I'm 230ish with gear.

Your mileage isn't in the 20's. At 35 mpg your looking at a 4 gal fill up at 140 miles.

I would say its about normal at those ambient temps.

I'm curious what others have to say as well.

Oh, with the 15/43 combo my dash odo was +4% over.

100 miles on gps = 104 on the dash.

Thanks for the info. I assumed i would be 10% or more over on the ODO. If its closer to 4-5% I feel a little better....

Your speedo will be further off than the odo.

I think its 7-10% off ?

You might already have done so, but please check Dawson's post below, it might be useful:

http://www.vfrdiscussion.com/forum/index.php/topic/73156-my-longwinded-theory/#entry864565

If the pair valves are disconnected are they always open (letting fresh air in exhaust) or closed?

the OP has not been active since before christmas, so we are pretty much just talking amongst ourselves.

anyone else with crappy fuel mileage all of a sudden should check for a failed and leaking fuel pressure regulator.

Veefer800Canuck

the OP has not been active since before christmas, so we are pretty much just talking amongst ourselves.

anyone else with crappy fuel mileage all of a sudden should check for a failed and leaking fuel pressure regulator.

And try to catch it before it gets REALLY bad. Mine was pouring fuel into the #4 cylinder, to the point that the bike wouldn't turn over.

Most forums want people to do searches for threads relating to the topic they wish to discuss and pickup the discussion if there is something to add. I have no problem starting a new thread if that's what i should do.

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.

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.

ReefDiver

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...

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.

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.

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

Veefer800Canuck

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.

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.

Link please?

Definitely want to do this.

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

AndyB

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.

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

y3v

AndyB

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.

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

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!

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)

"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.

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.

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.

[image: holy-thread-revival-batman.jpg]

:wink:

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. :)

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

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.

LeakingLewis

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

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.

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Terry

LeakingLewis

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.

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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.

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.

kaldek

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.