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It will work fine without the air box but you need to understand first what the air box contributes and therefore what you will lose without it. I've got some books you can start with :)
And after reading up on the subject you will (unfortunately) still just be speculating. :icon_scratch:

If someone really wanted to know they could dyno the bike, pull off the "suction pipes" between the throttle bodies and air box, clamp a pair of K&N's onto the throttle bodies and do another pull on the dyno.

That would give you an idea of what the airbox is, or isn't, doing without any mods that aren't easily undone. :eek:ccasion14:
 

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I have to say I'm with @JohnT on this one. Until someone gets their airbox-less 9T dynoed, all opinions are just that. What's needed here is hard evidence.
 

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Stevem77, I agree with all of what you say there, but with the exception of the long cam timing, I'm not sure much is very effected by the airbox. My thinkning is that it's a long stroke, low revving engine and as such, an airbox has a much lower impact than it does on a short stroke, high revving motor.

But, I am certainly no expert and am only going by my own experience of playing around with other bikes.

I'd take you up on the book offer, but don't think that's too practical! But I'd very much welcome any inputs you can share with us on the specifics of the subject if you can.

I'm not in front of the bike right now, so not sure how possible what I'm about to say is, but can one detach the tubes that connect the injector bodies to the airbox in order to test the effect and re-attach them with minimal effort?
 

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Well, I took the RHS tube of that connects the injector to the airbox today for a 'look see'.

The tube, along with the large trumpets inside the airbox, were interesting. If you imagined these straightened out, they form a very nicely shaped and large velocity stack. So my fist thoughts were, irrespective of the airbox per se, losing these velocity stacks doesn't seem wise.

So I spoke to my dyno man, and he was also rather downbeat about the idea. He said individual pod filters can be made to work 'ok' but not as well as the stock set up.

His biggest issue is with the sensor that's located in the airbox. This can be made to fit inside a pod filter, but however well you do it you're only measuring / reading from half of the engine.

So all in all, I'm probably gonna stick with the stock airbox myself.
 

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Stevem77, I agree with all of what you say there, but with the exception of the long cam timing, I'm not sure much is very effected by the airbox. My thinkning is that it's a long stroke, low revving engine and as such, an airbox has a much lower impact than it does on a short stroke, high revving motor.
Well, I took the RHS tube of that connects the injector to the airbox today for a 'look see'.

The tube, along with the large trumpets inside the airbox, were interesting. If you imagined these straightened out, they form a very nicely shaped and large velocity stack.
So I spoke to my dyno man, and he was also rather downbeat about the idea. He said individual pod filters can be made to work 'ok' but not as well as the stock set up.

His biggest issue is with the sensor that's located in the airbox. This can be made to fit inside a pod filter, but however well you do it you're only measuring / reading from half of the engine.
There are a few mis-conceptions here. Being in the USA and using our antique measuring system our R NineT's have a 4" bore and a 3" stroke. That's a big bore short stroke motor. These aren't low revving motors. With a 3" stroke we have a mean piston speed of 4,000 feet/minute at 8,000 rpm, a figure a modern engine can live at just fine.

I can't find info on the cam timing. The engine runs like it has moderately "long" duration with lots of lobe separation to minimize overlap. Pretty normal emissions strategy. FWIW it does look like HP2 cams (that I also can't find specs on) and their valve springs will swap in.

The "sensor that's located in the airbox" is the inlet/ambient air temp sensor. It can be mounted anywhere it can "see" ambient air temp.

Those "long velocity stacks" can be an issue. I've had engines that benefit from filters attached right to the throttle body (or carb) mouths and some that liked more length.

I suspect our airbox is there to muffle intake noise and was "tuned" to minimize the "damage" done. Priority being intake silencing and then "tuning" to make it hurt performance as little as possible. The way to find out is to just remove the throttle body to airbox "hoses" and clamp on a set of individual filters. Easy enough to do. Forum members have removed the airbox (usually chopping it up to get it out) and installed individual filters. None have said it made their bike run bad/poorly. Unfortunately it seems none have dynoed theirs...
 

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Hello chaps,
I have just removed the Airbox, and installed the Pier City Battery box. This is in addition to a Competition Werkes baffle less exhaust, no exhaust flappy thing and of course the K&N's on my ports.Oh, and booster plug.
Now, this afternoon is the first time Ive given it a good run with all this in place at the same time. It's a different animal to be sure. The torque has most definitely diminished, engine braking non existent by comparison.
Delivery of power has become a bit mundane to be honest.
I'm having a custom exhaust system made a week Monday for it that will closely resemble the Clutch Customs R Nine system. With this in place I think it's going to need a PCV and dyno. Perhaps the change wouldn't have been so noticeable had I left the valve in place ? Don't know.
I will update on whether or not this results in happy boy or one that should have left well enough alone.
 

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I will update on whether or not this results in happy boy or one that should have left well enough alone.
Give it some time for your fuel trims to reset/adapt, it may take a while. If you have a GS911 it would be a good idea to do a reset, it would speed up the process.

You've made enough changes all at once to muddy the water as to what did what...
 

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Delivery of power has become a bit mundane to be honest.
This is the sort of result you get - not because the K&Ns flow more or less air but because the length of the inlet runner is tuned to match the cam phasing, duration etc which affects the efficiency of the air intake. The airbox also provides a store of stable air hence the volume of the airbox is important is important.

With a bike like the R9t, it's not all about power :) I really like the things people do with them and looks can be just as important.

As I said on the last page a proper dyno test will show exactly what's happening but it might be a case of so what - it looks good this way ! :)
 

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Well my current hypothesis is that it's the loss of inlet tubes and trumpets that has the potential to cause most upset.

But we are all only guessing / hypothesising of course!

I plan on taking mine to Hilltop Motorcycles soon (in U.K.) to get the ECU programme re written, as I've heard good reports from others, and having spoken to them, I get a warm feeling that they know what they're talking about.

I intend to do at least one run with the intake tubes removed and pod filters fitted at the same time to see what the effect really is.

If it's a big backwards step, I'll be keeping the airbox. If it's not, I'm back on with the airbox removal plan. I have no expectation of the pod filters actually improving things, but I wouldn't be happy if I was knowingly making things worse.

Will report back as soon as.
 

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I intend to do at least one run with the intake tubes removed and pod filters fitted at the same time to see what the effect really is.

Will report back as soon as.
Sounds good. That's much better than speculation. Should be interesting to see what happens to the AFR's. May require some tuning...
 

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Jenvey might be able to sell you a horn which can be attached to the inlet which will move things back towards the correct length and also fits under a more attractive filter.
Frequently that added length is just the plumbing necessary to get from the throttle body (or carb) mouth(es) to the airbox and its' shape is created to make the intake think it's not there.

Current superbikes that have frames etc designed around airbox requirements still have the usual short (7" to 11") inlet tracts that end in the airbox. Cut away the airbox et al (illustrative purposes) and you have a rather traditional (variable length intakes excepted) looking intake with velocity stacks.

The voodoo is in the airbox volume / shape / snorkel length etc and the resonant tuning involved. Sometimes performance is the greatest consideration, sometimes the priority is silencing. Sometimes it's just a matter of having done the best they could within the limitations of an old design / configuration / layout.

If your priority is what's coolest looking, "more attractive", then none of the tuning considerations really matter...
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Well, I've been too busy to have motorbike play time of late. And I'm sorry to say guys, but I'm gonna let you down, I'm not gonna be doing before and after dyno tests!

"Why not?" I hear you wail.

Well, I did get as far as buying a pair of the bigger, angled, K&N filter pods from PCC and I recently tried them out, on a well known road, back-to-back with the stock air box connectors fitted and then removed and replaced with the pods.

Result? I couldn't tell any difference! I did think at times that it was better, but I'm old enough and wise enough to know this could be placebo effect! But I'm also old enough and wise enough to know that if it's so close as to not feel any difference, then it's not gonna have any real effect to real road riding.

Remember though that this was a quick bodge job test, I did not re-site the air flow sensor. My bike already has a full Apro system sans cat and flapper valve, so is probably quite lean without the airbox as well.

The bottom line for me is that there is no negative effect, so that's what I needed to know as I will now definitely proceed with the airbox removal and buy the rest of the kit from PCC. Afterwards, I will be getting the bike re-mapped at Hilltop Motorcycles who have done a few R9s already.

So to anyone out there who, like I was, is thinking "I love the sans airbox look, but is it gonna upset the fueling and make it worse to ride?" Well, the answer is no it isn't, so go do it !!
 

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...sorry to say guys, but I'm gonna let you down, I'm not gonna be doing before and after dyno tests!

"Why not?" I hear you wail.

...I will now definitely proceed with the airbox removal... I will be getting the bike re-mapped at Hilltop Motorcycles...
No wailing here. If you can just post "after the flash" dyno results it would be great. We have accumulated several of Hilltops flash results so we have the basis for a comparison. That should put an end to the speculation. :bowing:
 

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Hello all, update time...
So, custom exhausts fitted and off to H&M racing in Edenbridge, Kent. The exhausts are LOUD with baffles, and Tony at H&M said they were going to strangle the bike so he's going to dyno with them out. Pre tinkering we are getting 100 at the crank, this is with airbox removed and K&N pods on the booster plug still fitted. Power Commander goes in but Im advised to not expect too much, if any, gains in power now. Fuelling will be much better but manage your expectations.
Outside his soundproofed booth and testing it is ridiculously loud. testing finished and runs across the range we are getting 105. Bearing in mind a full Arrow system with K&N's has got his highest power on record there at 108.
Im not unhappy with that at all, and its riding lovely with the PC5 fitted.
Next up, fork upgrade kits front and back.
 

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I should mention....
It was Tony's view, airbox and snorkel removal with K&N's fitted is a good move.
It's my view, its a great move !
Booster plug obviously gone.
If anyone is going down the PCC route, it is a great kit, although I have put their carbon fibre snorkel replacement to one side and modded the original cover, but pick their brains on the shortcuts ( and there are some ) I didn't and ended up using a reciprocating saw to get my airbox out because there was no way I was taking the back end off.
 

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Now that we've all had this theoretical talk about what this does for the engine. I have a completely stock R9T Scrambler and I would like to get a hold of some K&N Filters to try this out before fully removing the airbox. I have the stock exhaust without the exhaust valve. What is the flange size needed for the filters for this? I'll post up the Dyno sheet once I have this done. Then I'll look into having it remapped once I change the exhaust. I've built many different race vehicles in the past and have handled this sort of thing before.
 
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