I know it's been discussed a bit, but no one really ever proving one is better than the other. Has anyone used both an airbox and a sock type filter on the same engine and dynoed in between?

Does it really help to pull air from a static mass of air for pulse tuning the intake charge?

Or is it about getting as much air in and then adjust the fuelling?

Any help'd be appreciated!

Chris.

Noise will be the key factor....an airbox will cut out most of the induction noise

would agree with previous comment as induction noise can be as much of a problem as the exhaust esp on track days etc air box would also mean jetting could be left reasonably standard saying that i run a tts filter and jet kit so can,t really comment on which is best.would think a well designed box with a cold air feed is probably best alround compromise for noise and performance but open filters sound faster

can you ft the air box under your bonnet? The sock on mine is very close to the fibre glass.

A foam filter and straight through exhaust, with a rejet or power commander, will give more power than standard. If you keep the airbox and use only a car exhaust then you may be able to rejet using the existing needles on lower grooves. Your choice really.

ive tried the old method of cutting the carb holes out of the stock airbox and rotating them so the box can be turned over to be lower. it can work in a fasion but its still way too high to fit under the MNR bonnet. looks like it would be a good 2 inches higher.
i guess a bonnet bulge could be used but it'd have to be damned big!

From playing with mine, having sock filters reduces the power and the closer the end of the sock is to the trumpet the more power you lose.

Panel filters are much better than some advertising would have you believe. So a large air box witht he biggest flat panel filter you can fit would be better.

It's amazing the difference in opinion on this front. Most people feel that rejetting to suit a pancake filter will give you more power than an airbox due to more readily available mass of air. But is this maybe related to the added noise influencing this thought?

I would have thought that the engineers that designed and built the airbox wouldn't have done it for fun? I realise there are noise constraints and regulations that have to be adhered to for road bikes, but is it proven that pulling air from a static(ish) mass is better?

I know an airbox is quieter but does it follow that an airbox with an aftermarket free flowing filter, that has 'access' to as much air as a pancake filter, produce more power?

I think that the main problem with airbox types, is that the filters are out of sight and therefore may not be cleaned/changed often enough. Sock filters can be 'seen' and are probably cleaned more often.
I personally have change the airbox to a sock type filter and seen the dyno go up. But I did also make sure that a small airscoop was placed in the engine cover to duct air into the filter.
A lot of airboxes have ducted scoops from the front of the car, so they have a bit of ram air.

Not opinion, winston, but rolling road data. Dynojet claim between 5% and 15% extra somewhere in the rev range, depending on the type of exhaust / filter used. The only reason you need to rejet is because more air is flowing into the engine, making the air / fuel mixture too lean. By rejetting, you put more fuel in to match the increased air flow. With more air and more fuel, I'd want more power and companies like dynojet publish rolling road graphs showing just that.

companies like yamaha have to satify all kinds of regulations and customer expectations, like noise, emissions, fuel consumption, reliability, cold weather starting, smoothness of power delivery, vibration, tone of the exhaust note and also cost. A plastic airbox and paper air filter will be cheaper than a foam filter.

Also, The bike has to travel at speeds upto 180 MPH with the airbox out in the rain. Your engine will only reach 120 MPH or so with the filter under a nice fibreglass rain cover.

You will get 5 or 10 mpre BHP with a good aftermarket set up than using the stock air box, exhaust and carburation.

That all makes perfect sense smart. Just curious as to why all the RGB lot are going back to airboxes?

Might contact them about that one...

RGB people are limited to the noise they can make on track. My R1 engine with foam filter and R1 can read 100dBA at SVA. With the MNR can fitted it is quite a bit louder. I wouldn't be allowed on to some of the quieter circuits.

Perhaps there is more to be gained by having a noisy can that is lost from having a quieter air box. From the shape of the box, it looks like it could act as a silencer.

quote:

---

Originally posted by chris mason
i was told by a guy who build race engines for side cars that removing the standard air box is like chucking as much as 5-10bhp down the pan.
the amount of monet spent by the japanese manufacturers on air box design is quite high. i'm sure all that research and development was for a reason

me personally although the sock's or open panel filter may look better the standard airbox is the one to use. could also be the difference between an early finish on a trackday and lasting all day.

Chris

---

quote:

---

Originally posted by chris mason
i was told by a guy who build race engines for side cars that removing the standard air box is like chucking as much as 5-10bhp down the pan.
the amount of monet spent by the japanese manufacturers on air box design is quite high. i'm sure all that research and development was for a reason

me personally although the sock's or open panel filter may look better the standard airbox is the one to use. could also be the difference between an early finish on a trackday and lasting all day.

Chris

---

Stick with the standard air-box wherever possible. Like Chris says, the Japs have spent huge amounts of money developing their air intake systems.

It's not just about the volume of air going into the engine that counts, its also about velocity and flow of air into the individual cylinders. The concept of modern airboxes is to create a pressure differential between the airbox and the cylinder. When the valves open, that pressure differential is what transfers the charge. The airbox has been designed to create positive pressure at a wide a range of speeds without having air "splashing" around and being turbulent. Turbulent air is no good for performance. It therefore follows that bigger is not necessarily better.

Hope that makes sense.

All airbox comments are absolutely correct! I've been involved in motorbike racing for many years and have read many books on tuning, and all point towards airbox development.

I remember in the mid-90's when a friend raced a YZF750SP, he priced a kit airbox and then promptly fainted! I can't remember how much it was, but it was nearly as much as my house!!!!

(that last statement is maybe not 100% correct, but you get the picture.....)

But, it also depends on the positioning and dimensions of the intake to the box. An R1 may gain several horsepower at full chat in the bike, but take that airbox and stick the inlets in a low-pressure area of your car and you may as well bin it!

A foam filter, a decent chimberley and a decent carb kit(TTS?)/Power Commander is adequate for most BEC applications, though a well positioned airbox will reduce noise output.



[Edited on 16/2/06 by Coose]

On the rolling road. We tried several jets with the box on or with socks. Socks were approx 5 BHP less even with rejettiing. The airbox does have a K&N filter in it though.

quote:

---

Originally posted by Lightning
Socks were approx 5 BHP less even with rejettiing.

---

Hey all! Again thanks for the input all.

I find this topic well interesting. Started a thread on Yahoo BEC about this too. And got the following replies... If you have a look on that forum there is some very interesting input...

http://uk.groups.yahoo.com/group/bike-engined-cars/

>-< Snip

Mark
I'm pretty much with you on this, people always think that they can improve
on what Honda's million dollar development team can do in their back sheds.
Whilst it is true that road bikes have to be tuned to meet certain emmision
and noise regulations you won't find many club racers taking off their
airboxes and replacing them with foam domes.
The tuning of the intake system is near as critical as the exhaust and it's
surprising the effect that even minor modification can have (in both
directions).
The carbed R1 is a good example of this. Anyone half serious on the track
was modifying the airbox (or more pricisely it's surroundings) to get a
bigger effective volume of still air out of it. To my knowledge nobody
removed it cos that just messed it up
Are airboxes 'pulse' tuned? Of course they are, to be more precise the
reasonant frequency of an airbox is tuned. But there is a little more to it
than that. The length and shape of the trumpets on the back of the carbs or
TB's inside the airbox has an enoumouse effect on intake efficiency and even
the shape of the radius at the end of the trumpets is far more relevant than
the casual eye might think. Of course many bikes also have some form of
RamAir as well now in order to pressurise the airbox at speed. With RamAir
the airbox design is even more significant as it is harder to achive without
a lot of turbulance in the airbox
On some later bikes like the Fireblade 954 there is even a flap in the
airbox controlled by the EXUP servo so hte tuning varies with engine speed
and another bike has variable length trumpets that have a very possitive
effect (Benneli it think)
Bike design has changed considerably over the years to try and get the
biggest airbox into the space available, a large volume and good supply of
still air is one of the main keys

In short, go with the airbox if you can get it in there, if you have to go
foam try to save some cash to spend on the dyno to get the best you can from
it. Flat out I suspect there won't be much in it but the airbox will make it
more driveable
Cheers
Brian
www.psycraft.co.uk

Online Stock & Shopping
Payment by Cheque, Bank Transfer or PayPal

-----Original Message-----
From: bike-engined-cars@...
[mailto:bike-engined-cars@...]On Behalf Of M 'n' J
Sent: 16 February 2006 13:48
To: bike-engined-cars@...
Subject: Re: [bike-engined-cars] R1 airbox or sock type filter?


My personal feeling is that the Jap engineers know lots more than me,
and they designed that engine/induction system to run with the airbox,
also including a ram system of one sort or another on all the later
stuff.Jet kits and pc's can make it work, but if you can use the airbox,
then I would run with it.I use a sock filter on my 9R , but only coz it
looks better sticking thu the bonnet than the kwak airbox does.
If I could really be bothered, then I would prob make up a proper bonnet
scoop and run with the airbox.
But I cant, and its virtually as fast as the R1 boys anyway, so who cares
?
Cheers
Mark

chriswalter99 wrote:
> I know this has been discussed before but I'm still interested in
> whether anyone has experience in comparing an airbox with sock type
> filters back to back?
>
> So from what I can tell...
>
> These statements are made in conjunction with proper jetting to suit
> the application...
>
> Airbox = Quieter; Harder to fit under bonnet; May produce more
> torque?; May produce more power?
>
> Sock type filters = Louder!; Easy to fit under bonnet; May produce
> more power?; May produce more torque?
>
> I have heard that some of the RGB guys went back to airboxes. Is
> this for power reasons or noise issues with certain tracks?
>
> Is there any truth in the idea of pulse tuned inlet pulses from a
> static body of air? I know there is some real benefits in pulse
> tuning an exhaust system. But an induction system?
>
> Any ideas people?
>
> Very curious as I've just sourced my R1 motor on Monday! 8D
>
> Any help'd be much appreciated,
>
> Chris.

>-<

Ta again,

Chris.

Another one...

>-< Snip

A couple of people have done some back to back testing in RGB, with findings
roughly as follows:
1. Airbox alone wasn't much different from foam filter, but obviously much
quieter.
2. as per GG's comments, source of air (colder) does matter with an airbox
3. Airbox with ram pipe from the front of the car increased topend (Martin
Brooks did back to back tests down the back straight at Cadwell using the DD2
to record the difference)
4. As per Brian's comments, the length of the ram has to be tuned. Mike
Field fitted a pressure sensor to his airbox to do this, and found that changing

the length also moved the hotspot (one length gave better mid range, another
better topend, again all done via datalogging not just seat of the pants)

All of this should be the last thing you worry about, as any improvement was
very marginal and at the extreme end of the performance scale.

>-< Snip

This does sound pretty conclusive to me?

Airbox it is?

Anyone else?

Ta again,

Chris.

Just be prepared to cut a naffing big hole in the top of your bonnet to fit the airbox...

The biggest difference we found with an airbox is it lowers inlet air temps SUBSTANTIALLY... this can also be achieved with a cold air "scoop" on the bonnet above the air filter of choice...

Heat is a major enemy on big 4-strokes, and without an airbox all the heat comes straight off the engine into the intake...

Have you felt how much heat comes off a bike engine at operating temps? stick that under a bonnet and behind a rad/oil cooler and the build up is even worse, especially on a mid engined jobbie...

Keep the air temp down, better density air in the engine, more power...

Everyone of our superbikes ran more power with a decent custom airbox, you wont find a superbike out there running a stock airbox...

Once you change the exhaust, the airbox is way out of tune anyway... but some of you guys havent taken that into account...

I was fully intending to use an airbox but was put off due to how easy a foam filter is to fit. I could do with seeing exactly how to modify the stock airbox and how tidy it can be done.

I think, this must be at worst a good trade off between induction noise and performance and at best, better than a sock filter.

I like Coose' point about the static air under the bonnet of the car vs the ram effect of the bike - Id be interested to see about feeding cold air into the sealed air box. I cant imagine that being too difficult with an abbundance of cold air around just asking to be ducted in. I suppose the only consideration there would be crap and water being ingested if its too low.

Interesting topic though

Richie

[Edited on 16/2/06 by RichieC]

I'm using the std airbox on my R1 injected motor (which has deepper sump than carbed I beleive).... and it fits under the bonnet with 1/2 inch sump below the chassis.

quote:

---

Originally posted by Hellfire
Stick with the standard air-box wherever possible. Like Chris says, the Japs have spent huge amounts of money developing their air intake systems.

It's not just about the volume of air going into the engine that counts, its also about velocity and flow of air into the individual cylinders. The concept of modern airboxes is to create a pressure differential between the airbox and the cylinder. When the valves open, that pressure differential is what transfers the charge. The airbox has been designed to create positive pressure at a wide a range of speeds without having air "splashing" around and being turbulent. Turbulent air is no good for performance. It therefore follows that bigger is not necessarily better.

Hope that makes sense.

---

Ta for that Mark.

I find all this info very interesting as it really does help so much in making an informed decision. I really do think noise will be up there on the priorities front for me...

I have heard of people rotating the airbox on a R1 and then cutting and rotating the carb mouths by 180degrees to get the box underneath the bonnet.

By rotating the airbox aren't you going to change the inherent flow characteristics of the box?

Most importantly has anyone got pictures detailing this cut and rotate procedure for an R1 airbox?

I'm very interested to see how tidy it looks.

Finally, what's a 'kit airbox' Mark? Is it the BSB or WSB term for factory race kit?

Cheers again,

Chris.

my bike engine came with a k&n in the air box already.

me thinks ill keep it

G.Man, are you talking about the ally airbox for the ZX12R. If so, we were given the design and drawings for it and intend manufacturing one in the very near future.

quote:

---

Originally posted by Winston Todge
Ta for that Mark.
Finally, what's a 'kit airbox' Mark? Is it the BSB or WSB term for factory race kit?

Cheers again,

Chris.

---

quote:

---

Originally posted by Hellfire
G.Man, are you talking about the ally airbox for the ZX12R. If so, we were given the design and drawings for it and intend manufacturing one in the very near future.

---

I Have a blackbird engine with a std airbox turned upside down and fits under JUST, and seems to run very well but needs tunning on RR dyno as top end a bit flat,

if i fit a k&n filter will this need re jetting?

sorry to but in on r1 question but i was also going to get a foam filter but the induction noise may be a issue for track days, certainly on my brothers ZX12R the engine noise is way louder than the exhaust with a carbon R1 can so could be a probelm???

any ideas grateful?

sorry for the hi-jack of the pol

I looked at my air box today and then tried to look at the foam filter on my car when shutting the bonnet. It seems that the filter just touched the bonnet when closed. No room at all for the air box.

It is the shape or volume of the box that is important? If I made one with the same volume and used the top half of the existing box with the inlet tubes moulded into it, would that have the same effect?

Best bet is to build an airbox that fits to the bonnet, that way you can take off the bonnet and airbox as one...

Yes the shape is important for ultimate BHP, but better to have it breathe well than strangle it...

A good airbox is a series of chambers, much like an exhaust to baffle the noise...

need like a Box on the inlets, then the bonnet becomes the top when fitted..

Rubber seal around the box to make it airtight, then a duct to the front of the car to draw in cool air... or chambers fed from a bonnet scoop, even better...

Interesting about the airbox smart...

My plan at the moment is to take the airbox into work and laser cut out an exactly symmetrical shape of the carb openings, then reverse them and re glue them in place and use silicon to seal any other big gaps.

Then perhaps use an MNR scoop or similar to give clearance for the top of the airbox. Definitely don't want a huge box stuck out of the top of the bonnet...

Any comments?

Chris.

I'm going for an airbox if I can find one simply because of the noise aspect.

I don't believe that the argument that the manufacturers made the optimum solution in the airbox because imo they made the optimum design given the space restrictions of the bike. Therefore I don't think you can say that it can't be improved on.

Regards,

Mark

Here's a question. If manufacturers spend millions to get the best possible solution, how come you can get more power than the stock set up when using presumably inferior aftermarket parts like a foam filter and kit car exhaust?

probably because the originals are designed to actually keep the noise down.... wereas these aftermarket parts can't even get you on most tracks let alone through SVA.



how are people justifying gains or losses?

You can very easily gain power and make the engine slower......
10bhp at peak may only be a gain for 1000rpm and a huge loss everywere else, thus be slower on the road. Its the rev range thats important.

I'm using a std airbox with K&N purelly so its quieter..... I can't for one min beleive that its better that a sock etc.. as the air is sucked from around the engine rather than above it.

The manufacturers part is probably near perfect for what they want it for hence the large cost in developing it, but there's a number of factors thrown into that pot which means its not usually perfect for outright performance, its usually a compromise of good performance with good noise suppression, working over a very wide temperature range etc.


[Edited on 20/2/06 by ChrisGamlin]

Having said that, the reason an airbox can be better than an open sock / sausage filter is as Hellfire and GMan have touched on, because of the quality of air delivered to the carbs / TBs. As well as controlling where the air is picked up (ie making sure its cold), with an airbox you can control the flow of air towards the throttle openings much better so hopefully providing laminar non turbulent air to the throttle mouths. With an open sock/sausage filter the filter itself will disturb the air as its sucked into the throttle mouths as well as all the other uncontrolled air moving about in the engine bay etc, so although there may be more air available in the viscinity, because its turbulent less of it will flow into the throttle mouths.

I currently run a sock filter as the stock R1 airbox would block my forward vision, but will hopefully be fitting an aftermarket airbox that someone I know is developing both to reduce noise and provide better quality airflow to the engine.

So you know of someone developing an R1 airbox that will fit under a bonnet? Do tell.

Not for me no, even if it sat flat on the throttle bodies it still wouldnt go under my bonnet

Im not sure of dimensions yet but hopefully it will be shallower than the stock airbox - I'll let you know more info when I have it.

I'd certainly be interested too Chris!

Keep in touch.