Airbox modding

[mik_str]

had some time and cooperative weather this evening, so I did some riding, and calibrating. After trying out the bike with the extra 1/8 turn I leaned out the fuel screws last evening (but never tested), I came home and turned them in another 1/8 turn, then after a quick ride, yet another. The bottom end is now about 70% cleaner and, once over 2.5K rpm, it pulls very cleanly with no surging or hesitation at any rpm. It seems to pull quite strongly too, though I know all about the accuracy of the ass dyno..... I will ride it like this for a while and see how things go.....will monitor my fuel consumption too to see how it gets impacted further to the significant leaning of the pilot circuit.....

[lloydie]

My ass dyno is crap lol what feels rich is actually lean ! Lol
Keep up the good work mik

[sirch345]

It sounds like you're making some progress Micky in the right direction, keep it up

Chris.

[VTRDark]

what feels rich is actually lean ! Lol

What you have to do in situations like that is try one step more or less in both directions on whichever circuit your working on and see which feels best. The you know which way to go, so keep going until it gets bad again, then go back one step and you good to move onto the next circuit down. Start with your mains, then needles then the pilot circuit last.

(:-})

[tony.mon]

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!

(:-})

Another example is exhausts.
A big bore exhaust usually delivers more power.
But if you go for the biggest bore of all, with no restrictions whatsoever (i.e. no exhaust pipework fitted, just the port opening to atmosphere) it will run very badly indeed...

One problem i notice is that an enlarged airbox, or one with the snorkel improved always sounds so much better that you think it's running better- same as fitted a can instead of a stock can.

It ain't always so....

[VTRDark]

This is very true Tony. Sometimes the changes can be very obvious and other times not so, but may have a placebo effect. It can all be very complicated and a bit confusing at times messing with the intake or exhaust system and there are times when things go against all logic. Some we win and some we don't, but it's good fun trying And more importantly one learns things along the way. I was reading up the other day on how the length of the end can can effect things and from what I can gather the shorter cans can give you more top end and the longer give more bottom. Also with packing, this has an effect on the pressures and resonance inside them which also changes things.

(:-})

[8541Hawk]

This is very true Tony. Sometimes the changes can be very obvious and other times not so, but may have a placebo effect. It can all be very complicated and a bit confusing at times messing with the intake or exhaust system and there are times when things go against all logic. Some we win and some we don't, but it's good fun trying And more importantly one learns things along the way. I was reading up the other day on how the length of the end can can effect things and from what I can gather the shorter cans can give you more top end and the longer give more bottom. Also with packing, this has an effect on the pressures and resonance inside them which also changes things.

(:-})

This is very true and there is a lot more going on than most people realize and on top of that the systems have to be able to work together also.

[lloydie]

It'll be interesting to see how the long and tapered akra cans and link pipes change things on mine when I fit them

[VTRDark]

Tapers control the expansion rate of the high speed gases as they are ejected out so smooths things out as the forces are changed from a kinetic energy into pressure. In an ideal world one would have a taper at each end of the pipe. One coming out the exhaust outlet at the head end and one going into the can. I have yet to see tapered header pipes at the head end for the VTR. V twins especially benefit from tapered pipes as the pulses are so strong.

(:-})

[tony.mon]

But a gentle taper, around 7% is a good figure.
Remember the old reverse cone maga cans, Dunstalls etc?
7

[mik_str]

Tried another variation on the filter..... lol

Removed the filter medium, cut down the base at the "step" (removed @ 7mm), and re-glued the element. End result is that the filter is now even with the cast pocket underneath. I then put the spacer under the filter (to raise the filter back up relative to the stacks, is now esentially right back to where it was last time, but have increased the post-filter volume via the spacer). Essentially, doing this allowed me to maximize post-filter volume, while also removing all steps and possible source of turbulence underneath. Can't really see what else to do to gain any additional improvement (logically speaking anyhow, given my limited knowledge of airflow).

Took it for a ride and am (very) happy to say, I think we have a winner gents!!!!! Runs better than it has ever has. Very clean (and urgent) pull at all engine speeds. Me happy!!!!!!!

My work here is done......

Now what else can I mod........

[lloydie]

good work im still waiting on parts to refine mine

[8541Hawk]

So where are the pics??

[Tweety]

Well... Here I was thinking I had an original idea...

Damn you mikstr for stealing my thunder...

I basically did the same as you... I took my trusty BMC road filter, and the stock filterbase, stuck them together and added a spacer... The same as you did... Then I copied the gutting of the airbox you and others have done...

But... Given that, I think I have one up on you... Sorry...

I kind of needed to setup/calibrate the dyno in my new shop... So I had a play with the carbs... I now have a confirmed ~3 hp increase midrange, ~1 bottom and high end... With no rough spots, dips or whatever that I'm unhappy about...

IE, what your ass dyno tells you, my dyno confirms... Thanks friend!

[mik_str]

guess it just conforms that great minds think alike, lol

thanks for the info Markus (BTW, nice to see my ass dyno got it right... for a change, lol)

P.S. no pics on this one, it went straight into the bike.... sorry....perhaps mext time I have it out I will snap a shot