The great airbox debate...

Fast Eddie said:
When a get a round tuit, I’ll try and get mine on the dyno, should be easy enough to ascertain if the air starvation to the airbox hypothesis is correct or not by simply doing a few dyno runs with seat fitted followed by a few without.
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Hello FE , Would you consider getting a BMC air filter and include that in your test as well ? With seat , with out seat , with BMC air filter ? That would be great !
 
You’ll have to remind me what a BMC filter is Tony, and why we think it’s better etc...

My initial thoughts were just to try 1. as stock with seat 2. stock without seat 3. As one but without filter 4. As two but without filter.

That will tell us whether or not the air flow under the seat is an issue, it will also tell us whether or not the stock filter is an issue.

IF my hypothesis is correct, and the under seat air flow is the main bottleneck, then replacing the stock design filter with a better flowing one won’t actually help.
 
Fast Eddie said:
When a get a round tuit, I’ll try and get mine on the dyno, should be easy enough to ascertain if the air starvation to the airbox hypothesis is correct or not by simply doing a few dyno runs with seat fitted followed by a few without.
Click to expand...

So is this going to take place in a wind tunnel? May I be so bold to suggest it would be better to connect a pressure sensor to the intake then ride at a fixed revs on a standard piece of road and then see what mods affect it. First thing would be riding/leg position on the saddle? Got a spare map sensor and a multimeter.
 
I don’t know what to look for with regards to a pressure sensor.

More or less? What effect does either have on power?

I would assume that less restriction = less vacuum? But I really don’t know if that always translates directly into improved engine power?

I’m a simple lad, I understand the link between engine power and facial grins...
 
Tony, in the pic below (posted by you I believe) is the red one the BMC?

It looks like a nice filter and is probably a good choice. But, in terms of the purpose of this thread, ie improving air flow and power, I can’t see how the BMC would give a meaningful increase over stock.


The great airbox debate...
 
Nigel,

The only way to tell if the BMC filter is any better than the stock filter is on a real dyno.
I doubt the tiny, if any difference will be perceptible to the 'seat of the pants' dyno.

On many sportbike forums they have tested the BMC back to back to the K&N filter.
BMC offers a race version and separate street version for some sportbikes model.

Consensus is that not much difference between K&N and BMC street filters, but the BMC race filter is much better than the other 2.
This is due to a filter gauze weave that is larger than the K&N or BMC street version filter weave.
However, BMC race filter users say that the race version definitely allows more dirt particles in to the airbox.

I wonder what type of gauze filter material is used in the BMC Commando filter?
 
BritTwit said:
Nigel,

The only way to tell if the BMC filter is any better than the stock filter is on a real dyno.
I doubt the tiny, if any difference will be perceptible to the 'seat of the pants' dyno.

On many sportbike forums they have tested the BMC back to back to the K&N filter.
BMC offers a race version and separate street version for some sportbikes model.

Consensus is that not much difference between K&N and BMC street filters, but the BMC race filter is much better than the other 2.
This is due to a filter gauze weave that is larger than the K&N or BMC street version filter weave.
However, BMC race filter users say that the race version definitely allows more dirt particles in to the airbox.

I wonder what type of gauze filter material is used in the BMC Commando filter?
Click to expand...

When I was looking at the air filter mod, the standard Commando (pre MK 1) filter measured 100mm high. When the factory send me a replacement, the new one was only 75mm tall. When I checked (with Olivia) this was the new standard. Looking at my new Euro 4, this smaller filter is installed. I think that the BMC filter is the full 100mm tall, so an extra 33% filter surface area!
 
Wodgedodge said:
When I was looking at the air filter mod, the standard Commando (pre MK 1) filter measured 100mm high. When the factory send me a replacement, the new one was only 75mm tall. When I checked (with Olivia) this was the new standard. Looking at my new Euro 4, this smaller filter is installed. I think that the BMC filter is the full 100mm tall, so an extra 33% filter surface area!
Click to expand...

If that’s the case then I’d say it’s worth having for the 33% extra...
 
Well Wodge, you persuaded me... I’ve now got a BMC filter coming from R&G.

At £77 inc VAT and postage I’m hoping for impressive results !!
 
Its worth it I tell you . Red one is the BMC .
 
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BritTwit said:
Nigel,

The only way to tell if the BMC filter is any better than the stock filter is on a real dyno.
I doubt the tiny, if any difference will be perceptible to the 'seat of the pants' dyno.

On many sportbike forums they have tested the BMC back to back to the K&N filter.
BMC offers a race version and separate street version for some sportbikes model.

Consensus is that not much difference between K&N and BMC street filters, but the BMC race filter is much better than the other 2.
This is due to a filter gauze weave that is larger than the K&N or BMC street version filter weave.
However, BMC race filter users say that the race version definitely allows more dirt particles in to the airbox.

I wonder what type of gauze filter material is used in the BMC Commando filter?
Click to expand...

I assume street version ? I don't know . I was looking for a K&N Stock Replacemnt for OEM and they said not going to make it. When I saw the BMC it was a no brainer . There are multiple tests showing the dyno increases on variours engines with just a change to this type of filter. The gains are not huge but they are measureable !
 
Looking forward to seeing how you get on with it!
Did you measure your current air filter depth?
 
TonyA said:
What I like about this is he retains the oil catching capability of the air box and keeps it looking stock . I'm not too keen on the road spray though. What is missing is the dyno runs to see if any of this helps .
Click to expand...

time for proper hugger extender. I am actively looking for something that could be adapted.
 
BMC filter. Exact fit? Plug and play? No trimming? Please furnish the model #. Thanks.
 
Britfan60 said:
BMC filter. Exact fit? Plug and play? No trimming? Please furnish the model #. Thanks.
Click to expand...

Not fitted mine yet, others will have to advise on that.
Part details are:
1 x BMC-FM983/08 : BMC Air Filter for Norton Commando 961 (£59.99 each ex. VAT) - £71.99
 
Thank you FE. Don't think I need it. 5 years and mine still looks new, but just to ease the boredom and flex my spending. New is always good.

Addendum: Not finding THAT model # here in the States. :rolleyes: item +VAT+shipping to US = not worth it.
 
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TonyA said:
What do you think of a K&N type panel filter snapped in at the front of the airbox ? Just below where the brass spigots are , say a 4in x 5in size panel ? There was a member who actually opened the hole straight to the bottom and used a k&N filter , Remember that ? I wonder how that's doing for him ?
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Tony, as well as your panel filter idea, I think there’s space in the area you mention to whack a hole in the airbox and fit another BMC filter...
 
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