Airbox modding

[mik_str]

heading out shortly.....

[mik_str]

Just got in from a 140 km ride and here are my preliminry results/impressions:
- bike pulls noticeably stronger in the very low end (below 3 k rpm)
- lower midrange seems at least as good as before
- bike seems to requires less (almost none) throttle to maintain 100 km/hr

It's a long weekend here and the roads were littered with cops so high-speed testing was very conservative.

Now, as everyone knows, the seat-of-the-pants is not a very reliable dyno; however, there were no negatives to the swap.

I filled up upon returning and fuel mileage seemed to be about 3% better than usual (granted, very small sample size). However, I did do a lot of full-throttle roll-on testing, whihc is hardly the recipe for fuel economy.....I did not (have to) change anything at all in so far as jetting is concerned, it rain spot-on (granted, it was already set up for a BMC street filter and ran very, very well with it).

so, it stays in adn I will continue riding it like this for a while. The next test will involve replacing the lower airbox unit with the enlarged unit (whihc will also seem the valve cover vents/hoses being run outside the box and dumpng into an external reservoir).....

[lloydie]

it would be good to see a fuelling chart before and after .
good report mik

im going to order a second standard filter to play with

[mik_str]

will get it on the dyno eventally, but not anytime soon.... though I completely agree with you about a fueling report..... I will wait, however, to get it dyno'd after I get the modded box on too....... hoping it works out, of course.......

[mik_str]

it would be good to see a fuelling chart before and after .
good report mik

im going to order a second standard filter to play with

If you want to give it a go (ie. copy what I did), let me know, will gladly share my notes with you.....

[lloydie]

it would be good to see a fuelling chart before and after .
good report mik

im going to order a second standard filter to play with

If you want to give it a go (ie. copy what I did), let me know, will gladly share my notes with you.....

Thanks but what I gave in mind is to raise the standard filter element up 10mm and widen the raised area by 25mm all round just to give the stacks a chance to get more air .
I will try to get it done in a month or two on the dyno but I need to get the akrapovic cans on first

[mik_str]

funny as I was just thinking something similar for the filter, essentially keeping the very top of the OEM filter "base" in place, but cuting out the 90-degree angle at the bottom and putting in either an angled straight piece or, better yet, a midly arced piece (cutting a sliver out of a 2" ABS pipe, for example) to facilitate the drawing of air from below the bell mouths into the "chamber" above.

The nonsense can go on forever, literally.......

I may need another OEM filter base, lol

[VTRDark]

This has just turned into a new level of OCMD Medication may be needed.

(:-})

[lloydie]

This has just turned into a new level of OCMD Medication may be needed.

(:-})

no cure it seams just need to mod more

[mik_str]

"can't...... stop........ have to......... get........ another......... filter........ must......... mod......"

[VTRDark]

When you find some some missing power to be gained it will all be worthwhile and a sense of achievement too. That makes it all worth it.

But you need to start thinking where's the compromise and how to fix that to counter balance. What's next. The OCMD continues....

(:-})

[mik_str]

At the end of the day, all you can do is optimise.... the idea of raising the filter medium away from the bell mouths is based on sound physics, so it SHOULD work....... not sure if I mentioend it here or not, but I found some info from a chap who used to work on racing Porsches and noted how they found 15 hp (on a 440 hp engine mind you) by simply changing the air filter design to open up some headspace above the stacks (he noted how testing showed that the area up to @ 5 cm above and @ 2 cm below must be unobstructed for optimal airflow). One cannot expect to uncover 10 hp on a VTR, but 2-3 (or more?) may be reachable. Same goes for the larger airbox. I was reading on an Aprilia site that the Evo airbox kit (which essentially removed the airbox lid and uses the bottom of the tank on various RSV/Mille/Tuono models to, yossir, increase volume) has shown as much as 6 hp gain in the midrange. FWIW too, in its last redesign, the RSV had its airbox enlarged to 10.3 L (for better breathing). By my calculations, opening up the stock box, routing the houses outside the box and using a spacer should get the stock 9L VTR box very close (if not slightly over) that figure...... Again, the physics is sound....... Add up all these little bits and you are soon talking some decent gains (personally, I am not overly concerned with 2 hp at 9000 rpm as my bike very, very seldom gets spinning that fast; however, show me 3 lb-ft between 3000-7000 rpm and you'll definitely have my attention)......

[VTRDark]

Oh I have no doubt you will find some gains somewhere, Honda are always going to build things on the side of caution, the more conservative side. Where the gains are, will be interesting to see. If it's down low/mid then we will be dancing. Adding more air will require more fuel and therefore a bigger bang. But I'm thinking there has got to be an optimum amount the space in the cylinders can handle. So things may start with being a big gain but percentage gains may tail off the more that is added.

It's a bit like putting gunpowder in a tube (fireworks for example) you can have one tube half full and another full to the brim with gunpowder and both will give the same power/bang. The only difference being that the excess in the full to the brim tube just gets wasted away up in smoke. Literally!

(:-})

[mik_str]

Installed my modded box this morning..... routed the valve cover vent lines to the Krankvent behind the box, woth the outlet line feeding a holding tank located under the seat (with small cone filter on the end). Took it for a short ride but it feels rich on the bottom, will try turning in the fuel screws 1/8 turn and see how that goes.... hard to draw any inferences, however, as it's a super-muggy/humid day.......

[mik_str]

so, turned the fuel screws in 1/8 turn, it was still running a bit rich, gave them another 1/8 turn. It is defintely better now and pulls very well, though still a bit "burbly" below 2.5K..... will ride it like for a day and may try to turn the screws in yet again....

no regrets so far

P.S. FWIW, a rough calculation shows that the airbox volume is now at or slight above the 10.3 L that the Aprilia RSV got to in its last update......