Crazy bad gas mileage!!!

[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

[kaldek]

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.

[spud786]

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

[spud786]

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

[tbzep]

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.

[Kirdro]

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)

[Polarbear]

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

[soichiro]

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)

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.

[mk2davis]

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.

3: 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.

[2thdr]

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?

[Kirdro]

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.

[mk2davis]

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.

[LEGEND]

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!

[Kirdro]

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 ;)

[Polarbear]

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

You did look for gas leaks, right?

Good luck.

C

[AndyB]

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 ;)

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

[Guest]

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?

[Guest]

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.

[Guest]

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....

[Guest]

Your speedo will be further off than the odo.

I think its 7-10% off ?

[arrow]

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

[Guest]

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

[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.

[Iakona]

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.

[Guest]

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.