running bike carbs on a 1.3

thanks for the info!, will keep that in mind, but i think i have decided to let bogg brothers do it, as they have 20ish years experience with it lol

simon

same here si, thats one hell of a good quote, you can't buy webers for that money. i need to put my time into sorting out my 3F lump ready for dropping in later. 8)

Dubstar_04 said

Alright guys, just a little pointer.
Any one making their own manifold will have to concider the length of the runners. The length will predetermin at what rpm the power and torque will come in. Best bet is to find some one who has bought a manifold and copy that length.

Sorry for sticking my nose in, i just thought it would help.

Tis a good point, though this is where stuff starts to get complicated!

A standard valver inlet manifold is really long, as it wraps over the rocker cover up to the shared plenum chamber where the throttle body attaches. Adding bike carbs to a stubby manifold is dramaticclay shortening the intake ports.
Am I right in saying that this will produce greater power at high revs, though less power low down?

:dontknow:

sim0n_parker said

:dontknow:

LOL - Thanks Simon!!!  

Going on what I can remember (so don't quote me on this!!!) I think you're right - the power will be better higher in the rev range. From what I recalll the logic is as follows: -

Shorter pipe = shorter wavelength for resonance
Shorter resonant wavelength = higher resonant frequency inside the pipe

So when the frequency of the inlet valves opening and closing matches the resonant frequency of the pipe, you get optimum intake conditions… This will be higher up the rev range.

EDIT - I got this next part wrong the first time, but just in case anyone's interested…

There are also overtones, where the wavelength is exactly half, a quarter, etc… of the length of the pipe. The frequencies of these conditions will get larger as the wavelength gets smaller, hence if you have a longer pipe, you will get optimum conditions at lower revs, and then smaller peaks of near-optimum inlet conditions further up the rev range…

HTH

Rich

Mcscrew - I think you're right.
I recall reading something about pulse frequencies etc before…

I was actually thinking about buliding an adjustable manifold of some sort to test if the length of the intake actually made a noticeable difference to the power band…
I suppose this could be achieved with different lengths of rubber tubing though, as this is how the carbs seem to be attached - nice and quick to swap over too…

got my carbs through today,
   
but.. :?  i cant seem to see where the choke cablke goes??  its a set of r carbs, it has a cable coming from what i think is the throttle mechism that screws in on like a little screw, but you cant pull the cable like youi normal would with a choke cable, it basicaly looks like the adjuster screw for the tick over????? but insted of using the screw driver its on a long cable about half a meter or so, could this be my choke cable?
the other thing is i need a bellmouth, or what ever there called trumpet? as one of them is broke, havent got all the pices to glue,anywhere know where i can get this from,
just gota save some doller now to get  my manifold.  :twisted:

The bit you refer to is a tickover adjustment.
You often see riders reaching in and fiddling with something at the lights etc… they are adjusting the idle speed (it just opens/closes the throttle butterflies a little).

Your choke should be a little sliding pin/valve thingy on the top of each carb. They will all be connected together with an aluminium brace. If you pull the brace (it will have a cable attachment on it somewhere) it opens all the valves.
If you wnat the choke to be active, then you are going to have to make a bracket to fix the cable to something and probably use a custom cable of sorts…

Here you go…

These are of an R6.
See the goldy looking bar with the elongated holes above the ports… That is the choke mechanism… In this pic, chokes are closed. Pull to the right and they open. You can see there is a cable attachment to the left of the pic.

hmm, cool looks like i will have to have a fiddle about and try nmake a bracket at the wkend,
chears for the reply

Will ram pipes on front of the car therefore alter the power band! meaning you wont need to change ur manifold but infact just increase trumpet length??

right then people.
will be ringing upsometime this week to get my manifold orderd, and carbs sent of and stripd cleaned rejeted etc, and was looking at my throttle cable today, do i use my origanel throttle cable or will i have to get a diffrent one and mod it to fit??
what choke cable shall i go for the standerd golkf one or what??
help please want to get it done with in the next two wks heehee :dance:  :pray:

many thanks peeps,

simon

dicky_morris said

Will ram pipes on front of the car therefore alter the power band! meaning you wont need to change ur manifold but infact just increase trumpet length??

Not sure if the length is total intake length or from the Choke to the head?
Saying that though, if the choke is fully open, then it doesn't matter, so it must be full intake length, meaning longer ram pipes would work!?!?

3ft pipes sticking out the grill it is then!!!   :mrgreen:

just got the latest issue of PPC, and theirs a nice article on bike carb conversions featuring the work of bogg bros.

dan_73 said

PPC

Not something I read - What is PPC?
Practical Perfomance Classics?  :dontknow:

AL_Mk1 said

dicky_morris said

Will ram pipes on front of the car therefore alter the power band! meaning you wont need to change ur manifold but infact just increase trumpet length??

Not sure if the length is total intake length or from the Choke to the head?
Saying that though, if the choke is fully open, then it doesn't matter, so it must be full intake length, meaning longer ram pipes would work!?!?

3ft pipes sticking out the grill it is then!!!   :mrgreen:

I think the critical length is the one from the butterfly valve to the head, as the valve itself interupts the airflow up to that point.

If you let me know the diameter of the pipe you're using, I could work out the optimum length for you if you like…

Rich

Al-    practical performance car mag, thrs nothing in it that hasnt been covered really tho. bogg brothers hav agot a new website…www.boggbros.co.uk

running polo gt engine on r6 bike carbs, anyone no the pressure it has to be regulated to? am using a facet solid state fuel pump to.

chears

simon

matt-mk1 said

Al-    practical performance car mag, thrs nothing in it that hasnt been covered really tho. bogg brothers hav agot a new website…www.boggbros.co.uk

Cool - cheers.

Just looked at their new site. It seems that my concerns about the un-equal spacing of the carbs compared to the inlets on the head shouldn't matter as it is quite clear in the pics on their site that some of the intake tubes are longer than others (Due to the angle the are attached).

AL.