The CB1100 Community Forum

I found the OEM air-box on the '84 Honda CB750S Nighthawk atrocious on high side-gust freeway days. That was the biggest negative with that bike. Glad to be here today writing about it.

(02-27-2024, 01:02 AM)Whoops_imp Wrote: [ -> ]

(02-26-2024, 10:55 PM)Tev62_imp Wrote: [ -> ]Supporting m in sc's first point is the fact that the airbox is a resonant chamber.

see the explanation here. http://motorcycleinfo.calsci.com/Airboxes.html

That just reinforces my conclusions that performance modifications are far outside of my (and probably most people's) expertise. It's hard for me to easily dismiss the engineering expertise of people that spend their entire careers perfecting their knowledge and experience. However, most car and motorcycle forum I have visited typically have a number of "essential" modifications everyone does. To me they seem to be more fad than improvement. The article touches on exactly that with the old mod most of us probably remember about opening up the air box. While I don't particularly care for the CalSci windscreen I bought for my FJR, they do have a lot of great information on their site. Their windscreen cleaning formula for example, works brilliantly.

That just reinforces my conclusions that performance modifications are far outside of my (and probably most people's) expertise. It's hard for me to easily dismiss the engineering expertise of people that spend their entire careers perfecting their knowledge and experience. However, most car and motorcycle forum I have visited typically have a number of "essential" modifications everyone does. To me they seem to be more fad than improvement. The article touches on exactly that with the old mod most of us probably remember about opening up the air box. While I don't particularly care for the CalSci windscreen I bought for my FJR, they do have a lot of great information on their site. Their windscreen cleaning formula for example, works brilliantly.


There is a lot wrong with that website- and therefore a lot wrong with people's perceptions of what 'truth is'.


Which is funny for a place that calls themselves scientific- as any reputable scientist acknowledges theory & practices - not absolutes.

He was right about airboxes being tuned... but then turned that into an absolute and became wrong when he said this-

"it used to be popular to cut additional holes in the air box to allow more air flow for high rpm. This is no longer a good idea. Modern air boxes can flow much more air than the engine will ever use."

Wrong.

Countless - and I mean countless times - it is dyno proven that a simple airbox mod can make more power.


"The idea that the snorkel makes for a significant impediment to air flow into the engine is questionable at best."

The moment you read that- disregard anything and everything that person says.

A 'scientist' doesn't 'question' then write'. A scientist questions and then TESTS.

Had this guy tested- he would see his assumptions to his thought processed assumptions were fatally flawed. And ready evidence proves it...for decades.

"Removing the snorkel from your air box is the exact same thing as removing the port in your speakers, the tube that's carefully engineered to have just the right diameter and length to reinforce the bass on your speakers at low frequencies. By altering your air box in any significant fashion, you're most likely going to cost yourself three to five hp in the mid range, and gain nothing measurable at high rpms."


WRONG....

He is ignoring the criteria already in his own article.

A speaker port is there to tune for the speaker and box- for best desired performance.

An airbox inlet port has NOTHING to do with performance- as he already mentioned and then ignored- it exists for noise abatement. It is NOT there for anything to do with performance whatsoever.

On pretty much ANY car / motorcycle made in the last 30+ years or more- opening up the intake to the airbox will GAIN flow and power- at the expense of increased inlet noise.

This has been proven over and over and over and over again.

Note- airbox inlet removal is NOT the same as airbox removal.

That being said- although airboxes (and intake plenums) themselves are tuned to a purpose / range- increasing the size of an airbox / plenum will increase it's power output.

If a manufacturer designed a bike/ car expecting people to only use it at 3,4,5k rpm then they had no need to make the airbox/plenum larger... waste of material / weight / cost to them.

SO- if an end user (us) doesn't have to meet emissons / noise / cost / weight- we can happy ignore everything the false 'scientist' said.... and actually do real world physics & results.


On the list of things I plan to test on my dyno is not just different airbox intakes / airbox holes / air filters- but the removal of the secondary airbox itself- while leaving the main box into the TB.

I may also design / build a larger main box into the TB to see what's what.


Some people write articles.... some people make power.

Perfect timing...

another guy like me that has his own dyno...and posts to youtube just made a video showing the difference by removing the airbox snorkel to a new Ducati-

https://www.youtube.com/watch?v=5F1syMr5VJA

As you can see- it gained power...and leaned out a bit a/f which makes sense- more air.

Once he is able to add fuel- the results of something so simple will be even better.

(03-05-2024, 07:48 AM)PowerDubs_imp Wrote: [ -> ]Perfect timing...

another guy like me that has his own dyno...and posts to youtube just made a video showing the difference by removing the airbox snorkel to a new Ducati-

https://www.youtube.com/watch?v=5F1syMr5VJA

As you can see- it gained power...and leaned out a bit a/f which makes sense- more air.

Once he is able to add fuel- the results of something so simple will be even better.

So0o0o you gonna use that dyno of yours and give us a "with factory snorkel" and "without factory snorkel" chart or what

2014 CB1100, 1981 KZ440 LTD, 1993 Yamaha XJ600 Seca, 1994 Yamaha XJ600 Seca

Yea... when both the weather and I get around to it.

I've considered buying an exhaust extraction system so I can run the bike in the garage with the door closed....but decided for what it would cost / space / time to set up... I might as well just wait for nice weather.

(03-06-2024, 08:39 AM)PowerDubs_imp Wrote: [ -> ]Yea... when both the weather and I get around to it.

I've considered buying an exhaust extraction system so I can run the bike in the garage with the door closed....but decided for what it would cost / space / time to set up... I might as well just wait for nice weather.

Ah yes that makes perfect sense.

I have been waiting for nicer weather myself to open the garage and do some spring cleaning so I can have a more productive workspace also.

Still gotta put those honed out air intake funnels in my bike.

2014 CB1100, 1981 KZ440 LTD, 1993 Yamaha XJ600 Seca, 1994 Yamaha XJ600 Seca