Air Box Mod

[nofreeride]

I know that there has been a lot of discussion and debate on this forum regarding modifications to the airbox, but I need to weigh in with my results.

I did cdog's airbox mod on my '04 as shown Here. I have since plugged the hole in the right side due to disastrous results:

1. Very Noisy. Not desirable IMO.

2. Very diminished low-RPM throttle response.

3. Consistently lower fuel economy (2-3 mpg).

Unless you have a PCIII or aftermarket tuner, or maybe the Barbarian mod, or don't care about fuel economy, I would not recommend it. Looks like maybe Yamaha got it right the first time. BTW, I did do the TB sync after modding the airbox. I'm sure many of you have different opinions or experiences. Feel free to post.

 

[charismaticmegafauna]

<snippage>... modifications to the airbox, but I need to weigh in with my results. 1. Very Noisy. Not desirable IMO.

I'm sure many of you have different opinions or experiences. Feel free to post.

okay....

Intake "honk" -- some like it. On other bikes, ones that have the airbox in front of the rider and above the engine, the intake "honk" can be considerable -- and sometimes tends to signify, aurally, 'performance'. Similar, imo, to loud-pipes.

Not-to-say that properly flow-benched/dynoed intake and exhaust modifications can't enhance performance numbers in places on the power-delivery curve -- they may. But, there's usually a decibel trade-off.

Actually, bikes with pronounced intake "honk" cause me to ride somewhat 'anti-socially'....

 

[RadioHowie]

Unless you have a PCIII or aftermarket tuner, or maybe the Barbarian mod, or don't care about fuel economy, I would not recommend it. Looks like maybe Yamaha got it right the first time.

There is positively NO reason to do an airbox mod on the FJR without doing modifications to the amount of fuel delivered.

Modern bikes are too lean-running to begin with. Without fueling enhancements, gutting the airbox is also going to gut low to mid range power by making the AFR even leaner than the manufacturer intended.

Now, imagine how poorly your bike would run with a modded airbox AND enhanced scavenging from an aftermarket exhaust, if you don't do something to increase the amount of fuel delivered.

All this is NOT to say there cannot be some benefit to "poor man" hotrodding...but to make intake and exhaust enhancement work properly, one can't leave increased fueling out of the equation.

And the Barbarian mod ain't enough.

 

[FJRGuy]

Unless you have a PCIII or aftermarket tuner, or maybe the Barbarian mod, or don't care about fuel economy, I would not recommend it. Looks like maybe Yamaha got it right the first time.

There is positively NO reason to do an airbox mod on the FJR without doing modifications to the amount of fuel delivered.

Modern bikes are too lean-running to begin with. Without fueling enhancements, gutting the airbox is also going to gut low to mid range power by making the AFR even leaner than the manufacturer intended.

Now, imagine how poorly your bike would run with a modded airbox AND enhanced scavenging from an aftermarket exhaust, if you don't do something to increase the amount of fuel delivered.

All this is NOT to say there cannot be some benefit to "poor man" hotrodding...but to make intake and exhaust enhancement work properly, one can't leave increased fueling out of the equation.

And the Barbarian mod ain't enough.

Where was this response in other threads on the topic? Exactly what the masses need to know! Thanks Howie.

 

[Wicked Webby]

I know that there has been a lot of discussion and debate on this forum regarding modifications to the airbox, but I need to weigh in with my results. I did cdog's airbox mod on my '04 as shown Here. I have since plugged the hole in the right side due to disastrous results:

1. Very Noisy. Not desirable IMO.

2. Very diminished low-RPM throttle response.

3. Consistently lower fuel economy (2-3 mpg).

Unless you have a PCIII or aftermarket tuner, or maybe the Barbarian mod, or don't care about fuel economy, I would not recommend it. Looks like maybe Yamaha got it right the first time. BTW, I did do the TB sync after modding the airbox. I'm sure many of you have different opinions or experiences. Feel free to post.

Sorry.. All I can say here is.... DAH!!

I agree. You can't have it all.....

1) If you expect to gain power... Expect more noise.

2) If you want to add more air, you MUST add more fuel. You should also reduce exhaust restrictions too... Or you might just effectively de-tuned your bike.

3) More Hp power often means more fuel consumption.

BTW, the barbarian mod does a very good job of adding fuel after your air box is modded. My dyno runs and original tuning was done with only that method of adding fuel..

Slighlyscratched you should have Tuned (pun intendeded) in here to get it right:

Here is how I did it:

https://www.fjrforum.com/forum//index.php?s...=102302&hl=

(Update 07/08/08)

Here is how I tuned in GREATER PERFORMANCE than I had on the dyno:

https://www.fjrforum.com/forum//index.php?s...hl=wicked+webby

A fuel tuner box (Dolbeck/Techlusion, PWC, Motty) does add a greater tuning capability (specifically adding MORE fuel at wide open throttle at the top of the rpm range).

BUT... It is not required (the bike will still run out AWESOME!) with more Hp and Tq all across the rpm range with only the barbarian mod, the right air box mod, and less exhaust restrictions.

WW

 

[exskibum]

Not surprised that there is a tradeoff (at best) in certain RPM ranges. Rather than get shouted down for again voicing my pessimism and belief that hacking airboxes is inadvisable, since it thwarts the ENGINEERED powerband benefits of airbox resonance, read it for yourself. The first link is from Kevin Cameron's discussion at pp. 50 and 51 of his Sportbike Performance Handbook:

https://books.google.com/books?id=LswdRd2Zm...num=10#PPA50,M1

Here's another:

https://motorcycleinfo.calsci.com/Airboxes.html

 

[UselessPickles]

Not surprised that there is a tradeoff in certain RPM ranges. Rather than get shouted down for my pessimism regarding hacking airboxes as thwarting the ENGINEERED powerband benefits of airbox resonance, read it for yourself. This is from Kevin Cameron's discussion at pp. 50 and 51 of his Sportbike Performance Handbook. Maybe this link will work to those pages:
https://books.google.com/books?id=LswdRd2Zm...num=10#PPA50,M1

Here's another:

https://motorcycleinfo.calsci.com/Airboxes.html

If you look at Wicked Webby's dony chart, you will see that a modded airbox with fueling adjustments does not have any trade-offs across the RPM range. It has gains everywhere, but more gains in some places (mid-range) than others:

My guess is that most of the resonance tuning of the FJR's air box is in the rubber velocity stacks inside the box; not the airflow entry points and flow rates into the box.

 

[exskibum]

Looks like I got quoted while I was still editing that post.

I remember reading that when WW posted it. Still, I decided not to do it. All this follows years of debate on motorcycle forums comparing OEM air filters to aftermarkets like K&N. (Once upon a time, my motorcycles all sported K&N's and back in the 70s, also had the K&N cones instead of the airbox I discarded.)

I'm mindful of many opinions by folks better than me (note bottom of first page in the second link I posted) that modern motorcycle airboxes flow more air than the engine can use. I'm also not sufficiently impressed by the typical Harley mod of reducing restrictions alone (pipes and intake) to gain minimal horsepower. Headers that work on overlap to generate a negative pressure wave up the pipe to pull more mixture into the combustion chamber are a different matter.

I mean -- it's your bike. Do what you want to it. Seriously. I read the whole threads posted by Wicked Webby and Cdogman when they did theirs. Interesting. But with what I've read elsewhere, I'm leaving my airbox alone (I do have PCIIIs and 4-2-1 full header systems on the Blackbird and FJR). I'm just skeptical of the benefits in light of a lot of other stuff I've read from folks with 4 stroke engine engineering backgrounds, and my experiences with a 1975 Kaw Z1 with a Kerker 4-1 (not 4-2-1) -- I was lucky not to float valves on it at high RPM from the gains there, but it suffered from a bad mid range sag).

For similar reasons, I run OEM air and oil filters, too -- I think the engineers got it right on those. That wasn't just the result of reading jestal's posts, but he confirmed it. I would like to hear his take on this -- where the hell has he been these last many months, anyway?

 

[RadioHowie]

Unless you have a PCIII or aftermarket tuner, or maybe the Barbarian mod, or don't care about fuel economy, I would not recommend it. Looks like maybe Yamaha got it right the first time.

There is positively NO reason to do an airbox mod on the FJR without doing modifications to the amount of fuel delivered.

Modern bikes are too lean-running to begin with. Without fueling enhancements, gutting the airbox is also going to gut low to mid range power by making the AFR even leaner than the manufacturer intended.

Now, imagine how poorly your bike would run with a modded airbox AND enhanced scavenging from an aftermarket exhaust, if you don't do something to increase the amount of fuel delivered.

All this is NOT to say there cannot be some benefit to "poor man" hotrodding...but to make intake and exhaust enhancement work properly, one can't leave increased fueling out of the equation.

And the Barbarian mod ain't enough.

Where was this response in other threads on the topic? Exactly what the masses need to know! Thanks Howie.

I was too busy wrecking my valves.

 

[Bustanut joker]

Wrecking yer valves?? Ya mean you have two of em?

Cuffin' the carrot, Beatin' the Bishop.. I know those, but "Wreckin' the Valve"? Thats kinda weird :blink: even for you Circus Boy..

:jester:

 

[UselessPickles]

I just read the info about air box resonance. It's generally based on a combination of air box volume, inlet snorkel length and inlet snorkel cross-sectional area, so the air box mods most likely shift the resonance frequency. This would cause a shift in which RPMs get the most boost from the air box resonance. However, the formulas given are presented as estimates and that actual trial and error testing is also needed to fine tune the dimensions (probably because there's many other factors that contribute in less predictable ways). All this to say that it's quite complicated and difficult to calculate the effect of modifying the air box.

Luckily, predictions and calculations are not necessary if you have measurable results. I know of two sets of real world results that show a large improvement to mid-range torque by modifying the airbox and adjusting fuel. First there's Wicked Webby's dyno results - big gains in the 4.5k RPM area.

I also have the fuel injection map from my Motty AFR Tuner. I have 100% throttle tuned to 13.2:1 AFR. I believe this is the same AFR that is generally used as a target when PCIII's are mapped for 100% throttle. The PCIII map from DynoJet for stock FJRs actually decreases fuel across the RPM range for 100% throttle. With my modded air box, the Motty has similarly decreased fuel across the RPM range for 100% throttle... except for about 3.5k to 5k RPMs, where it actually ADDED fuel as compared to stock. This means that there is more airflow into the engine in that RPM range and, combined with more fuel, more boom in the combustion chamber.

Webby's dyno chart does not show what happened below about 3.5k RPMs, so it is possible that the stock air box is tuned for resonance in the very low RPM range and that the mod moved it up into the mid range. If that is true, then there would be a loss of torque in those low RPMs. However, you don't really do much 100% throttle high acceleration below 3.5k RPMs, and I haven't noticed any loss of torque down in that range. It is possible that I am just opening the throttle more in that RPM range to make up for loss in torque, but I haven't hit the ceiling of 100% throttle in the low RPMs feeling like there should be more.

But, all my information is about a different air box mod than the one mentioned by the original post, so it is probably irrelevant. Let's get back to the original post.

1. Yes, a modified air box creates more intake noise. Most of the additional noise only occurs at large throttle openings. It's also not really that loud relative to the other other loud stuff happening in those conditions (exhaust, wind, shouting "WEEEEEEEE!", etc), so it doesn't bother me. I might even like it

2. Someone needs to volunteer to get before & after dyno results with a PCIII using a stock map before the air box mod, then a PCIII with a custom map after the air box mod. This will be the only way to verify the gains and losses across the RPM range. The diminished low-RPM throttle response could be perceived relative to an increase in the mid range, or it could be caused by improper fueling and could be improved by a custom mapped PCIII. It could also be completely psychological like perceived gains that some people have where there are no gains or even losses.

3. Maybe you've been opening the throttle more to enjoy the gains of the mod? It is also possible that improved airflow could reduce gas mileage. With improved airflow, you might need to open the throttle less to get the same amount of torque. Smaller throttle openings create more disturbance in the airflow and can reduce the efficiency of the air and fuel mixing. Some cars actually run the engine coolant through the air box to purposely warm up the air and cause you to open the throttle more, leading to better fuel mileage, but less available torque at 100% throttle.

 

[rok312]

Unless you have a PCIII or aftermarket tuner, or maybe the Barbarian mod, or don't care about fuel economy, I would not recommend it.

I don't think anyone (on purpose) would recommend increasing air flow without attention to proper fuel management. Of course you're going to see bad results. This is not specific to the FJR - put an 'aftermarket' or modded air box any motorcycle without re-jetting or re-mapping and you're looking for trouble.

 

[radman]

Opened up Franks, didn't do a ****** thing to the bottom end-if anything, he's torqier. But then he has a header and PCIII, and already got **** mileage, so......but when you whack him, be a hangin on.

 

[exskibum]

I don't think anyone (on purpose) would recommend increasing air flow without attention to proper fuel management. Of course you're going to see bad results. This is not specific to the FJR - put an 'aftermarket' or modded air box any motorcycle without re-jetting or re-mapping and you're looking for trouble.

Indeed. At one time, I had two Blackbirds -- a carbureted '97 and a FI '03. The FI '03 has ram air ducts through the cowling. The carbed '97 only looked like it did, but had two rectangular clear plastic vanes that stood between the cowl opening and the intake ducting to the airbox, which had the effect of stopping that ram air action. More than a few guys with carbureted birds forgot to put those things back in when they removed and replaced the cowling. Result was it'd run fine at idle, but get to even 10 mph, and the bike would cough and die. It was instructive to have both the carbed and FI versions at the same time to see that what looked like similar cowlings was not, and also that a couple nondescript pieces of plastic you might think were unnecessary garbage were essential to making the carbed bike run.

_____________

Useless Pickles -- interesting analysis. Thanks for that. It reads like you have an engineering background.

Still, for me, I'm leaving the air box alone. I can only imagine what a replacement might cost if I should decide to put it back the way it was.

______________

Bust-- "cuffin' the carrot"??!??!?

No wonder Mizz Bust had ta cuff ya around the head.

 

[UselessPickles]

Useless Pickles -- interesting analysis. Thanks for that. It reads like you have an engineering background.

No engineering background, but I did stay at a Holiday Inn Express once

I just have a mind that craves logical analysis.

BTW - here's a visual comparison of the fuel maps at 100% throttle that I was talking about:

Keep in mind that these are from completely different fuel injection devices, so it is completely unknown how the vertical axes are related between the two. Only the general shape and negative vs. positive can be compared. For example, it looks like at about 3250 RPMs that the modified bike is requiring less fuel than the stock bike, which would lead you to believe that there is a performance loss there. That's not a valid conclusion because I have no idea if -10 on the PCIII is equivalent to -10 on the Motty, or -100 on the Motty. I just sized the 2 charts vertically such that they both have about the same vertical range visually.

Also keep in mind that I also have a full exhaust replacement on my bike (Holeshot header and Remus Hexacones). The higher area in the curve from 7500 to 8500 is probably a result of the Holeshot header being tuned for more performance in higher RPMs than the stock header. The huge bump between 3750 and 5250 is most likely due to the air box mod, especially since it coincides with the area of greatest gains in Webby's dyno chart. The zig zag from 2000 to 2500 is probably just inaccurate because I haven't really opened my throttle 100% in that range enough to allow the Motty to make its adjustments.

 

[UselessPickles]

Still, for me, I'm leaving the air box alone. I can only imagine what a replacement might cost if I should decide to put it back the way it was.

No need to imagine. It's only about $30, according to jstewart. He bought a new air box to keep the bike ridable while he modified the new air box, then swapped them when he was done modifying. The biggest hurdle is the cost of getting the fuel injection properly tuned.

 

[Mike-H]

PC3, Muzzy full exhaust, open air box with additional air horn, dyno tuning (Yamaha Canada's race dyno) more performance when asked & better fuel economy when touring....go figure :blink: .....

 

[Bustanut joker]

PC3, Muzzy full exhaust, open air box with additional air horn, dyno tuning (Yamaha Canada's race dyno) more performance when asked & better fuel economy when touring....go figure :blink: .....

Not surprised to hear this.. You guys got some kinda weird air up der.. Can't wait for Bearlys response prolly another 50 horses fer him

:lol:

:jester:

 

[nofreeride]

Thanks all. I am now fully edumacated. Did I spell that right?

I did not assume that increasing air flow without increasing fuel would actually help performance. I thought, however, that the computer may compensate for the increased air by adding fuel (oxygen sensor, you know). But I'm now convinced that I did not actually increase the volume of air entering the combustion chamber (except maybe at high rpm). The opposite may actually be true, the velocity of the air may have actually decreased at lower rpm's due to the de-tuning of the air flow. This would have resulted in lazy response at lower rpm's, followed by more throttle at the right wrist, therefore lowering fuel economy. All I did was screw up the airflow as originally designed and tuned by Yamaha.

Am I way off base here?