Jump to content
cuoccimix

Gas mileage on a 98 5th gen

Recommended Posts

Hi, this is my '98 5th gen VFR 800 FI. I bought this bike one year ago with 27500 km on the clock. The bike was like new - not a single scratch or rust spot. Went through a very long series of small issues (R/R, connectors, etc) caused by the long inactivity of the bike. Now they are all solved, except one - the gas mileage! It is pretty bad, around 14 km/l  (33 mpg) riding in "mixed" mode (around 5000 rpm with some high speed launch). The exhaust always smell a bit rich, the bike runs well though. I did the usual snorkel / flapper mods, went through a lot of discussions, somebody says it's a normal mileage for a pre-cat bike, somebody other says i should clean / synchronize the injectors, but my mechanic says that everything is OK on my bike. I would like to know if the bike mileage is normal and if it can be improved without buying a Power Commander.  BTW, it is true that US bikes from the same year have a different ECU? Maybe they have a better gas mileage? Thanks!

22046730_950063718464740_4183134102309083936_n.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Hi Michele.

Poor fuel economy - Have you checked the state of your air filter.? Are you running Ethanol added fuel? Check for any vacumm leaks. Possible fuel pressure regulator issue. Assume you don't have any flashing Fi codes? Make sure your Thermostat is working correctly, bike is reaching normal operating temp.

No dragging brakes?

 

If you don't have the full Service Manual you can download it from this site at the forum home page.

Good luck.

Ciao ciao.  

  • Like 1

Share this post


Link to post
Share on other sites

The US models do have different ECUs than the European models, but I'm sure they're not vastly different in terms of mileage. 

 

Where are you based?  My ST1300 resides in my brother-in-law's garage in Bologna.  But a VFR would be better for Futa, etc...  

 

Welcome to VFRD!

 

Ciao,

 

JZH

  • Like 1

Share this post


Link to post
Share on other sites

Hi, air filter has been replaced, no dragging brakes, the bike works well but i never checked the fuel pressure regulator. I had some FI issues caused by bad connectors and/or ground connector. Now it' OK and i have also poured a whole can of injector cleaner in the tank. The gas mileage was always the same - never seen a real improvement. JZH, i live in Bari, South Italy. Quite far from the classic "motor valleys" in the North, but we have nice roads here too 🙂

  • Like 1

Share this post


Link to post
Share on other sites

I told you on Facebook, you are chasing ghosts. Early 5th gens aren't as gas mileage friendly as newer generations.

You describe pretty normal mileage for a 98-99. Sync those throttle bodies (mainly just good maintenance item to do for smoother riding), can take the injectors out and have them cleaned and flow tested, and check the FPR just in case.

 

The 6th gen got better gas mileage, and the 8th gen gets even better. 

  • Like 1

Share this post


Link to post
Share on other sites

33 mpg for a US bike is pretty horrible, not anywhere near normal. I'd be doing some serious looking into things if my '99 only

managed 33 mpg in mixed riding. If I wasn't getting at least 40 mpg I'd be really pissed. Unless you're really getting into it a lot.

And running 10,000 rpm more than 5,000 rpm most of the time.

  • Like 1

Share this post


Link to post
Share on other sites

Mine has had ~32-38mpg since 1199 miles on the ODO. I manage 44mpg on the 8th gen. Wife gets 48mpg on her 8th gen, softer on the throttle and weighs less.


Rider weight and luggage also factor in. Heck, so does tire pressure. Rolling resistance goes up a ton even if psi is down by 5-10.

Share this post


Link to post
Share on other sites


 

3 hours ago, thtanner said:
Mine has had ~32-38mpg since 1199 miles on the ODO.

 


FWIW, my 6th gen is very similar during the cold and wet months with mixed city and highway commuting. In summer when doing mostly longer rides away from cities, I see 40-44.

 

  • Like 1

Share this post


Link to post
Share on other sites

1998 VFR 44-45 mpg on E0, ~40-42 mpg on E10, 87 octane, very consistent mpg for the last 70K miles.  And yes they smell like they are running rich, sorta like a mid 60's muscle car🙂

  • Like 1

Share this post


Link to post
Share on other sites

Here's a bit of information that hasn't been mentioned yet in this thread: the 5th Generation VFRs breath pretty heavily through their crankase ventilation system, which dumps the oily blowby gases into the bike's airbox.  As a result of this the intake valves can end up with a good bit of carbon build-up on them.  If you're going to take off the throttle body, for something like getting at and replacing the thermostat or to remove the injectors to send out for cleaning, you should look at the intake valves to see just how much carbon is stuck on them.

 

Both of my two 5th Gen VFRs are low-mileage but both of them have a good bit of carbon build-up on the intake valves.  I'm currently looking into various ways of cleaning them up.

 

Another possible cause of fueling problems is a fuel pressure regulator that is beginning to fail.

  • Like 2

Share this post


Link to post
Share on other sites

I have a '98 as well- bought new. I have never gotten good has mileage but don't really care. It's a motorcycle and I ride it fast. I also weigh around 230 lbs. Last summer I did a mileage comparison between using the Power Commander and without (running non-ethanol 92 octane gas). The difference was small. The PC gave me a bit better gas mileage and certainly better fueling. The actual numbers are posted on this site. My only mods are the PC, K&N air filter, and a Vance & Hines titanium pipe. Ride and enjoy!

Sent from my SM-G955U using Tapatalk

  • Like 2

Share this post


Link to post
Share on other sites

I usually get 40-45 MPG riding the mountains of North Ga. you mention you tried the Power Commander. Do you have a PC3 or PC5? I have a PC5 and it's driving me insane. I cannot get the bike to run decently witht he PC5 on line. (1998 VFR800). What Map are you using? Would like to pick your brain if you're running a PC5. Thanks. 

 

-Tony

  • Like 1

Share this post


Link to post
Share on other sites

I have a PC 3. Got the map from a fellow on this site. If you search there are guys who have uploaded maps for the PC's either here or on the other VFR blog. I just tried the one that closely matched the mods I had on the bike.
David

Sent from my SM-G955U using Tapatalk

  • Like 1

Share this post


Link to post
Share on other sites

My experience so far has been with '00's and '01's so I cannot comment on mileage but my current '01 came with a Staintune and an PC2. Low rpm's were snatch-free and the machine felt faster but gas mileage was at least 10% less than I'd gotten on three previous 00 - 01's. Sold the can and PC, went back to stock and mileage returned to 50's and better. Easily. 

And I cannot remember where I learned this but I believe the K&N filters are bad news. I replaced the K&N mine came with. The OEM air filters have always worked well for me. I believe the K&Ns restrict air flow.

  • Like 2

Share this post


Link to post
Share on other sites

I have a 99 (no cat) with a bit over 100,000km on it. It has well-balanced throttle bodies, well-maintained K&N filter, new plugs, correctly working thermostat ( usually sits at 78-80C except in traffic) and in-spec valves. I typically see 270-290km before the last fuel bar starts flashing, and that equates to 16-17 km/L. I thought that was a bit low and have replaced the FPR but that made no difference. It is pretty sensitive to riding style, lots of point and squirt will see that drop, and highway droning would make it a bit higher (but less fun). 

Share this post


Link to post
Share on other sites

With PC5 running autotune, bosch 3 bar FPR, large airbox/dual trumpet mod, and Micron slip on I average about 40 mpg with about 60% of mileage on interstates and 40% stop and go city.

 

I had poor economy several years ago that was resolved with replacement of the leaky stock fuel pressure regulator and injector cleaning.  At the state of mods on your bike, I was averaging closer to 44 mpg.

  • Like 2

Share this post


Link to post
Share on other sites
3 hours ago, interceptor69 said:

How much do u weigh?

Sent from my SM-G955U using Tapatalk
 

 

eheh, that's a good question....I'm a big guy, but my weight was the same on my previous ZZR 600. As Thtanner said, i'm chasing ghosts...i can't really cope with the fact that there are other bikes from the same years that have an higher mileage. I bought the viffer also for long travels and that fuel hunger really pisses me off, actually it prevents me from embarking more often in long journeys. You know, average price in Italy is 1.60 Euro per liter.   

Yesterday i checked out the average 5th gen mileage on Fuelly, and apparently US bikes have a lower consumption than EU bikes. I even thought to install a US/California ECU. Apparently i got 10 km more after pouring a can of injector cleaner in the tank. Will try to buy another can and/or to manually clean the injector.
Wow, if only we had lower gas prices, i could live with that.

  • Like 1

Share this post


Link to post
Share on other sites

By the way, doing "the usual snorkel-flapper mods" isn't really a great idea.   

 

Yeah, there's a lot of back-and-forth argument on this subject but I can tell you that 99% of the guys (maybe even 100%) who argue in favor of this modification have not read Chapter 21 of the 1998-2001 Honda VFR800FI Interceptor Service Manual, which is entitled, "Technical Features".

 

If you were to carefully read (and understand) the information Honda has provided in this chapter you would realize that disabling the flapper valve and messing with the snorkel is a counterproductive effort.  I'm not going to try and explain the whole situation here in this post to your forum thread, but the most important piece of information contained within Chapter 21 is that the VFR800 ECU runs in two different modes, depending on "demand" (which is closely, but not completely, related to throttle position).  In conditions of low demand the ECU makes its fueling decisions primarily based on information provided by the Manifold Absolute Pressure Sensor, and in conditions of high demand the ECU makes its fueling decisions primarily based on information provided by the Throttle Position Sensor.

 

Now I'll leave it to you to carefully read and understand the Chapter 21 information and by doing so come to an understanding of why the snorkel and flapper are installed on the engine (and why the Honda engineers programmed the flapper to open and close when it does).

  • Like 2
  • Thanks 1

Share this post


Link to post
Share on other sites
1 hour ago, GreginDenver said:

By the way, doing "the usual snorkel-flapper mods" isn't really a great idea.   

 

Yeah, there's a lot of back-and-forth argument on this subject but I can tell you that 99% of the guys (maybe even 100%) who argue in favor of this modification have not read Chapter 21 of the 1998-2001 Honda VFR800FI Interceptor Service Manual, which is entitled, "Technical Features".

 

If you were to carefully read (and understand) the information Honda has provided in this chapter you would realize that disabling the flapper valve and messing with the snorkel is a counterproductive effort.  I'm not going to try and explain the whole situation here in this post to your forum thread, but the most important piece of information contained within Chapter 21 is that the VFR800 ECU runs in two different modes, depending on "demand" (which is closely, but not completely, related to throttle position).  In conditions of low demand the ECU makes its fueling decisions primarily based on information provided by the Manifold Absolute Pressure Sensor, and in conditions of high demand the ECU makes its fueling decisions primarily based on information provided by the Throttle Position Sensor.

 

Now I'll leave it to you to carefully read and understand the Chapter 21 information and by doing so come to an understanding of why the snorkel and flapper are installed on the engine (and why the Honda engineers programmed the flapper to open and close when it does).

 

I second everything you posted.

 

On 12/28/2018 at 6:09 PM, GreginDenver said:

Both of my two 5th Gen VFRs are low-mileage but both of them have a good bit of carbon build-up on the intake valves.  I'm currently looking into various ways of cleaning them up.

 

Seafoam direct into the TB and a smoke show should help clean them up. Always impresses the neighbors when your vehicle becomes a smoke machine /s

Share this post


Link to post
Share on other sites

I hadn't read the pertinent pages mentioned above, so I got the ol' HSM out and read them. I don't think "counterproductive" is necessarily correct.

I also haven't disconnected the snorkel and flapper, just because I've never bothered. From what I read the benefits of the snorkel is very minimal

since it is saying that restricting air flow slightly at low speeds will help the smoothness of the power output at slow speeds. So if you remove the

snorkel and "flapper lid" or "variable intake duct", you may cause the low rpm response/power output to not be as efficient. But looking at the

difference between the snorkel and the "variable intake duct", the difference is pretty minor all in all.

 

To me it's similar to putting a free flowing intake on an engine: you lose some low end, but gain it back, and then some more, at the top end. It's pretty

much a non-issue IMO.

Share this post


Link to post
Share on other sites
3 hours ago, FJ12Ryder said:

To me it's similar to putting a free flowing intake on an engine: you lose some low end, but gain it back, and then some more, at the top end. It's pretty

much a non-issue IMO.

 

Okay, just in case I'm missing something here:

 

You're saying that performing a mod to make the flapper valve stay open during low Rpm/low "demand" situations (instead of closing as it was designed to do) somehow delivers more horsepower in the higher RPM/high "demand" conditions (during which the flapper was always programmed to be open anyway)?

 

I'm confused.

  • Like 1

Share this post


Link to post
Share on other sites

Yeah, that's about it. Removing the flapper valve and snorkel, which is what several of the modifications basically

consist of, gets rid of any obstructions to air flow into the airbox. With fewer obstructions to the airflow into the

airbox, you could get more air flowing at higher rpm's, possibly resulting in more power at higher rpm's.

 

IMO regardless of the verbiage in the HSM, Honda did the snorkel and flapper valve to help lessen intake noise, and

touted it as a "good thing" for power. Maybe, maybe not.

 

Personally I don't think it makes much difference either way...which of course is why I've never messed with it.

Share this post


Link to post
Share on other sites

My "normal" mileage for my 1998 VFR is 40-44mpg on 93 octane.  Only mod is Vance & Hines SSR2 slip on.  

 

If that were my bike it would be a huge red flag.  I monitor my mileage for two reasons

1.  Curiosity

2.  Great indicator of driving habits and or motorcycle health.  

  • Like 1

Share this post


Link to post
Share on other sites
15 hours ago, FJ12Ryder said:

Yeah, that's about it. Removing the flapper valve and snorkel, which is what several of the modifications basically

consist of, gets rid of any obstructions to air flow into the airbox. With fewer obstructions to the airflow into the

airbox, you could get more air flowing at higher rpm's, possibly resulting in more power at higher rpm's.

 

IMO regardless of the verbiage in the HSM, Honda did the snorkel and flapper valve to help lessen intake noise, and

touted it as a "good thing" for power. Maybe, maybe not.

 

Personally I don't think it makes much difference either way...which of course is why I've never messed with it.

 

You're not getting me (can't tell if you're doing it on purpose or by accident), but let me be clear: I'm completely disagreeing with you on this subject.

 

Once again, reading Chapter 21 of the Service Manual will completely debunk everything you (seem to) believe about Flapper Valve and Snorkel modifications.

 

I'm totally willing to discuss this situation in depth, issue-by-issue, if you would like.  

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy.