Induction air flow vs power/torque output question

[sapperj]

All,

I have been playing with my Air Box / Filter set up on a Hyosung GT250R. There have been plenty of sugestions / comments on how changing the stock airfilter affects mid range and top end performance.
Also, I have put Cycleworks Can on... sounds nice
So the Factory, who must have a budget in the Millions for R&D and also emission levels to work too, bring out a bike with a huge airbox, paper element air filter drawing air through a 'snorkle' / tube built into the filter cartridge.
Seems restrictave whan you look at it, so...
Mod #1 is to open up the orifice to allow greater airflow, right?
Mod #2 is to put a K&N 'Pod' type filter on... No restriction there aye?
Mod #3 is to replace stock paper filter element with K&N or similer type...maby?



So my questions are,
1. what is the point of the snorkle?
2. How does the 'air box' affect induction?
3. Is less restriction better or do these engines need regulating at that point in the induction?



Jas

[bogan]

is the snorkle situated in such a way as to draw warm air from near the engine (prevents icing I learnt the other day), and maybe out of the way of bugs etc, if so, thats prolly why its there. All the mods you listed assume the bike isnt getting enough air as it is, try sticking a vacuum guage after the filter. Is the simple answer, but theres bound to be complicated interaction between intake runner lengths and airbox volume and swirly wirly air currents round the place too :P

[vifferman]

The simple answer is that air intake construction and modification is not simple. There are factors at work here that include designing the thing to give reasonable performance without excessive noise (at least, not in the range that compliance noise testing is carried out); the Helmholtz effect (google it - it's too complicated to explain simply); making sure there's no carb icing in cold conditions; making sure that any dust/debris that enters doesn't just clog up one part of the filter; making sure airbox volume doesn't compromise tank volume too much; blah blah blah, etc etc.
The simple answer is that there are usually no mods an owner can do that will result in significant power gains or performance advantages without some other undesirable negative effects, especially on a 250. The manufacturers (unless they do a crap job of R&D) usually don't design a motor such that they've left some horsies lying around to be found by an owner tweaking this'n'that.

To answer your questions:
1. The snorkle prevents ingress of large foreign objects, water, and too much dust, and directs airflow such that the incoming air isn't affected unduly by outside factors such as airflow past the bike, outside temperature, etc. Sometimes/usually (?) it plays a part via the Helmholtz effect in assisting efficient airflow into the engine.
2. The airbox creates as large as possible (given dictates of space) a reservoir of filtered air to the engine. If designed right, there will be a resonant effect at some (hopefully well determined rev range) which assists with achieving good horsepower (more than is achieved with no airbox). That is, more airflow should result from having this particular airbox than another one or no airbox. Short of you testing umpty-zillion different designs with sophisticated equipment, there's really no way of determining if the manufacturer got it right, unless it's REALLY badly wrong. Many bike owners butcher their airboxes and decide that more intake noise is the same as "the bike goes much faster and has more power".
3. See #2. Only the manufacturer's R&D department or an accomplished tuning house can answer this.

[sapperj]

WOW

Awesome answer............. I'm stunned!

I googled the Helmholtz effect, and can see how the 'snorkle' would improve induction at a particular engine speed. That would explain Steve saying why you loose a bit of mid range when you cut your airfilter up

I might have to dig through the bin out in the shed and get out the glue and sticky tape.

Thanks guys, to KB

[vifferman]

Perhaps not particularly helpful though, huh?
If you're REALLY interested, try trawling teh Interdweeb for independent tests of airfilter efficiency. You'll find that the over-hyped K&N doesn't perform quite as well for either filtration or airflow as the company (and many people that have shelled out $$$ for them) would have you believe.

[BuzzardNZ]

removal of the snorkel was the biggest free mod i've done, noticed a huge gain in mid to high rev range.
I have a bmc air filter, notice no difference there, but its reusable, not like a stock filter ( i.e. washable )
Point to note, when i removed my snorkel it fucked up my EFI/ECU, I had to get the ECU remapped, but as urs is on carbs it may need to be re jetted, not sure, but you can always put the snorkel back in if you don't like the effect.
It also sounds louder without the snorkel in.

[sapperj]

Yeah I have tried several combinations with my air box etc... I think the most noticable gain was when I cut the snorkle out... top end improved. What got me questioning this was a reply to my previous post in club 250, stating that doing this mod would have a detrimantal effect on mid range power / torque.
Possibally so, yet to see some dyno figures to prove it though. Allthough the Helmholtz effect might be working at that rev range and the removal of the snorkle takes that away... again, still speculation.
I think what happens is that because of the improvement at top end, it 'feels' like the mid range is lacking? Just an idea.
So I tried on a K&N pod type filter... seemed all good at top end but way too loud for my liking and this time I noticed it felt really flat between 5 and 8K... got me thinking about it all but I had allready paid for it and didnt want to go back to a paper one, so I decided to try and use it inside the airbox to quieten things down and it fit the oval hole perfectly, sweet! so I made up a plate to hold it there and dropped it in like a stock one would fit. Now it seems to me to be the best configuration I have tried to date. Quite but free flowing.
I believe the air box is an important part of the induction system and any free flowing filter element can only help, as to the snorkle... dunno.