Triumphrat

Sheepdog · 06-09-2009, 07:20 PM

There is an interesting article about airboxes on page 107 of the July issue of Cycle World. Technical Editor, Kevin Cameron devotes four long paragraphs to an explanation of airbox resonance and when it can be useful to a engine's powerband. I was pleased to see that much of what we have found to be true here on this forum is similar to Mr. Cameron's conclusions (airboxes are good for many applications, but not all...). I enjoyed the article mostly for the statement, "(an airbox)...is used by engineers for such purposes as filling in any low-torque region of the exhaust pipe, etc. By using intake, exhaust, and airbox resonances, it is possible to cobble together quite a smooth powerband."

To Nark or not to Nark has often been a contentious discussion on this board. I'm not trying to say that airboxes are the answer for everyone's application, but they do have a greater purpose than just silencing intake honk. Particularly for engines that are close to stock and are not going for gains only at redline.

BTW, the Bonneville roadtest in this issue is pretty good, too.

Forchetto · 06-09-2009, 08:00 PM

There's a technical article here about the properties designed into airboxes, lots of science in it, not just for sound reduction but for the proper working of CV carbs. Not to mention waterproofing the air filters. Hosing down the bike or even leaving it in heavy rain can play havoc with unprotected K&N type airfilters, water blocking jets, etc.

The way I understand it is that it can have a power benefit at wide open throttle, if you re-jet correctly, but low and mid-range torque and driveability suffers, specially with CV carbs. Normal slide ones are not so fussy.

'08 T100 · 06-09-2009, 08:19 PM

I'm not qualified in the least to comment on the technical aspects of the AB on a Bonnie.

However, I can comment from my own experience on the benefits gained in my own situation.

First off, I have been lucky with my bike in so far as any mods that I have made to it, have only increased it's performance.

I was running a stock bike with TOR's. Then I removed the AB. I noticed a substantial increase in response, power and overall performance.

Then I replaced the TOR's with a really free flowing exhaust to match the intake, and I couldn't believe the power increase etc, etc.

The really amazing thing is that I don't always ride WOT through the gears although, the carrot is dangling.

Since my most recent mod, (the BC SLEEPERS) I've been playing around a lot with the motor riding in all gears and all rev ranges.

This moto pulls strong and will perform beautifully with Lot's of grunt in any gear, at any RPM.

Or, If I just baby it through the gears, It's just as happy!

Nobody will ever convince me that leaving the intake & exhaust stock on these bikes is a good thing. Also, I am still running stock CV carbs at this moment in time (until the weekend) and so these gains that I spoke about are with stock carbs.

I'd also like to add; that I have learned more about running these moto's to the best of their limits on this forum than any other source I have seen.

Mike

Dave2001 · 06-10-2009, 05:21 AM

What an interesting response.

Apparently technical details mean nothing in the 'real' world. I am worried that all of the comments are purely subjective ( I noticed a substantial increase..,etc.), but it's also interesting to note the comment that - 'Nobody will ever convince me that leaving the intake & exhaust stock on these bikes is a good thing.'

It's nice to see an open minded approach.

propforward · 06-10-2009, 07:13 AM

Well he was open minded enough to try removing the airbox.

Dave2001 · 06-10-2009, 07:38 AM

Quote:

Originally Posted by propforward

Well he was open minded enough to try removing the airbox.

:

Ventura · 06-10-2009, 07:40 AM

I can see this thread becoming interesting!!

Come on Mike, your turn!!

V.

propforward · 06-10-2009, 09:00 AM

Sorry Dave, I just don't know what you're getting at. If you could actually lay out where you're coming from then it can be discussed, but if all you're going to do is post mildly snide comments and head banging smileys then we won't get anywhere.

As for tech articles on airboxes, you have to review the specifics of the airbox in question. Each is designed for a set of goals to suit the bike in question. Some of the goals are the same - example noise reduction to meet epa standards, housing of an air filter and so on.

Other goals may differ. For example the air box on my Ninja is designed to increase airflow and even provide pressurised air at certain bike speeds to maximise performance.

Having looked inside the Bonnie airbox, I don't think maximising performance was part of its design brief. But then, maximum performance was not part of the design brief of the bike.

So, you can leave your bike stock, and as I have said before, these bikes are perfectly adequate in their stock form (except for the headlight) - I had a lot of fun on mine while it was stock.

Or, you can treat the bike like a blank canvas, and turn it into whatever you want. The simplicity of these bikes opens the way for all kinds of different approaches if you feel like it. Pulling the airbox is just one approach. Gutting it is another.

I pulled the airbox off, and after appropriate jetting experiments have my bike set up very nicely. I have noticed no difference in a/f measurement in cross winds or anything, the engine is more responsive, and pulls much harder across the whole range. I know the engine produces more power, because I had to modify the clutch (new springs) to cope with it. Haven't put it on a dyno yet, maybe later on in the summer.

I love my bike in its new form, and have no intention of putting the airbox back in. It eats rear tyres more quickly, but it accelerates much better than ever before, and I like it.

That's how I feel about it, you have to go your own way (ooh! quick theft of a slogan

)

The airbox makes a jolly fine rear mudguard. If you do pull it off rather than gutting it, appropriate thought needs to be given to protecting electrics and so on in my view. I posted some info about that already.

EDIT: by the way a lot of this has been discussed before, you can read some prior discussions in the links in this post:

http://www.triumphrat.net/twins-tech...ml#post1132928

At the end of the day it pretty much comes down to some people want to do it, some don't.

Dave2001 · 06-10-2009, 10:22 AM

Thanks for taking time to reply, but I really don't wish to get into a lengthy discussion with you, as we have been down that road before. Therefore the following are general comments, and not aimed specifically at you.

Beleive it or not, it's not mods persay that I have an issue with. However, there is a lot of 'perceived wisdom' touted on the forum which will 'shout down' any alternate views even if they have some technical basis or merit. Whilst there are some extemely good posts on performance mods, there are many more who make claims that they do not back up, except by 'butt dyno'. Surely these claims deserve to be challenged on the odd occasion?

On the airbox front, I have posted several times, so my views should be well known. However, the original post on this thread tried to impart some interesting information which was summarily swept aside.

I though I was actually quite reserved in my comments, and I'm sorry if you don't agree.

propforward · 06-10-2009, 10:45 AM

Quote:

Originally Posted by Dave2001

Surely these claims deserve to be challenged on the odd occasion?

Certainly.

Preferably with facts. We actually have a lot of facts on the forum. The only scientific measure that you can do is to use the dyno, which gives you a comparison of bike to bike and is very useful.

The trouble is, that does not give you the whole real world story. The butt dyno is important.

I set my bike up for maximum performance on this mod, and now that is done I am about to tweak it a bit more, which may trim a bit of performance from it, but will improve fuel efficiency somewhat, so that I can get the best of both worlds, or at least a very good compromise. I am using an air / fuel gauge to get that right. Once complete I may put the bike on the dyno to satisfy my curiosity on power / torque gains.

So Dave - I just don't know where you're going. We have a bunch of actual measured data on the forum that shows the improvements you can get by modifying or removing the airbox, and then some beyond that. That is the facts people speak to.

As technical articles on airboxes - there is no one set of airbox criteria. While a resonance might be used for maximum performance on one bikes airbox, it may not be used that way on another.

The technical article is interesting, but I am not going to make the assumption that it is relevant to the Bonneville airbox. In fact, when I like at the gathered data on with/ gutted / removed, I tend to believe that the Bonneville airbox was designed to

a) reduce noise
b) provide housing for the air filter
c) provide enough air to meet the original design spec for power for the bike
d) provide a mudgaurd, battery box and safe storage for electrics.

I don't think it was ever set up as a resonator to maximise air flow. Maybe to provide even air flow across the rev range, but not the maximum.

If you've got some data that shows that airbox can actually outperform it's removal in total you should show that, because I think people would be interested.

Regarding Forchetto's comment on driveability, once the jetting is set correctly, the bike rides smoothly and easily in all areas of the rev / load range. I'm talking specifically about the Bonnie now. Results on other types of bikes might be different.