FCR stacks

[Killerwhale]

Just for argument...

Most IL4´s i´ve seen with keihins has two stacks in one length and the other two shorter/longer...
I guess this is to get bottom and top end in a compromise!?
What if we would put one blue and one red stack on ours?

[Mincehead]

I`ve seen it on 4 pots too Kw but wouldn`t do it myself. You don`t want any variance between intakes in the ideal world. This is interesting but a better read is the pdfs document under the references on that Wiki page :

http://en.wikipedia.org/wiki/Velocity_stack

[M.V.]

I was pondering a similar thing on the weekend over a beer or two, theoretically you could tune one cylinder for midrange & the other for top end power & have the best of both worlds...

Or would your engine just self destruct?

[cobbadiggabuddyblooo]

I pefer your idea killer talked about earlier with a variable length bellmouth that could shorten and lengthen thro the rev range to suit.
Or what would happen if you cut the bellmouth end at an angle so instead of being just a short red one or longer blue one you had a short edge and long edge.
maybe I'm wrong but aren't the bellmouths in the airboxes curved in a similar fashion???

[TRiXy]

If I'm not mistaken, Yamaha have been doing this from factory recently on their R1s... I'm sure I read it somewhere... And yeah, it is intended to be a compromise between top end and mid range... As for cutting them on the angle, that would just have a similar (but less so) effect to a shorter runner, with a larger mouth... I love the idea of a variable length runner, and there's been a few designs over the years. BMW have had a 'infinity adjustable' inlet on their cars many years ago... Toyota had their TVIS system, with 2 different length runners for a single cylinder with a butterfly valve over one runner (one open low speed, two open high speed).

If there's one part of an engine i'd like to spend time working on, it's the inlet, but unfortunately just about every car maker has had a similar idea, and every have had minimal effects. There's so many other inefficiencies with mass manufactured engines, that adjustability in inlet lengths has minimal effect.

I toyed with the idea of making a throttle out of 'crushing' a piece of silicone hose... so it was fully clamped shut on idle/low speed, and just left wide open for full throttle... The sticking point for the idea so far has been the in-ability to 'fail to safe'... That is, if something goes wrong it will fail to full throttle...

[Killerwhale]

I`ve seen it on 4 pots too Kw but wouldn`t do it myself. You don`t want any variance between intakes in the ideal world. This is interesting but a better read is the pdfs document under the references on that Wiki page :

http://en.wikipedia.org/wiki/Velocity_stack

Well, now it´s done!
Bike behaved very strange on the dyno last week..and also went more rich on very top than last time around.
Just HAD to get greasy hands last night....
Some surprises where under the tank, breatherfilter totally clogged...going to make a catchtank instead...left spigot almost all the way out of the rubber and spigot could be turned 2-ish turns before bottom out
Hence FCR´s where angled wrong in the inlet´s
Had a pair of 38mm inlet rubbers laying around so mounted them instead and everything´s ok...exept for the 38mm restriction!

Drilled the main air to 220 to even out the rich drop on top and put blue-left & red-right.

Bike´s SO much better, got scared shitless last night...in a good way!

Hmm, one should care a bit more about TLC!!

[Mincehead]

Kedo do a neat little opaque plastic catch tank for oil or coolant Kw, I`ve just tried to find it on their website but it`s not easily navigatable or simple to search on.
They definately do one because I`m on their mailing list for the catalogues and I saw one in there one night when browsing through it.
Alternatively they`re cheap enough off EvilBay:

http://cgi.ebay.co.uk/KART-RECOVERY-OVE ... 4151bc3ac9

http://cgi.ebay.co.uk/GENUINE-HRC-OVERF ... 27b9bc460e

You could also run the cam cover breather hose right to the end of the bike, exiting to atmosphere.
The length of the hose will stop any oil mist getting all the way to the end, you`ll simply see steam and or condensation coming from it when the bike`s warming up.
Your motor being already quite highly tuned is exhibiting the crankcase pressure issue that might be alleviated somewhat by an additional breather as the guy who is racing the TRX (his forum name escapes me) has found.
I`m going to look into an additional breather when I tune my motor more too, remember air inside the motor is acting as a kind of damper, sapping power if there`s no direct route for it to escape.
Interesting the effect you`ve found from fitting one blue and one red bellmouth, did you do a dyno run to see what it equated to in torque and bhp, A/F ratio?

[Killerwhale]

Kedo do a neat little opaque plastic catch tank for oil or coolant Kw, I`ve just tried to find it on their website but it`s not easily navigatable or simple to search on.
They definately do one because I`m on their mailing list for the catalogues and I saw one in there one night when browsing through it.
Alternatively they`re cheap enough off EvilBay:

http://cgi.ebay.co.uk/KART-RECOVERY-OVE ... 4151bc3ac9

http://cgi.ebay.co.uk/GENUINE-HRC-OVERF ... 27b9bc460e

You could also run the cam cover breather hose right to the end of the bike, exiting to atmosphere.
The length of the hose will stop any oil mist getting all the way to the end, you`ll simply see steam and or condensation coming from it when the bike`s warming up.
Your motor being already quite highly tuned is exhibiting the crankcase pressure issue that might be alleviated somewhat by an additional breather as the guy who is racing the TRX (his forum name escapes me) has found.
I`m going to look into an additional breather when I tune my motor more too, remember air inside the motor is acting as a kind of damper, sapping power if there`s no direct route for it to escape.
Interesting the effect you`ve found from fitting one blue and one red bellmouth, did you do a dyno run to see what it equated to in torque and bhp, A/F ratio?

Yup, got that KEDO book as well..going to be night reading...even though i´m leaning towards the long tube route!

I´m very interested in an extra breather because i´ve seen it struggle a bit when hitting 8k+ revs and of cource all that rotating mass with create nice pressure

I will get it up on dyno again soon, as the carbs where..not quite in their optimal position! and let yall know.
I can describe it as a small burst of nitro coming along when going over 5k-ish revs...but i expect same loss down low of cource...anything else is a nice surprise...

[cobbadiggabuddyblooo]

When reading last night about the bellmouths,wasn't there something there about the optimum tuning length on the blue ones was 3500rpm so I'm sure if the red ones are a little shorter you may find that its tuned length may be around 6000rpm mark.
Just like any principal in resonate freq. and harmonics. don't be suprised if the harmonic of the two further up the rev range will be a sweet spot also.(prob close to the rev limiter tho )