Bike Tb Suitability , Set Of R6 Ones Available

[sutol 0]

Something like an S.U. carb ?

Into deep water here, think I'll shut up until I've had a think

 

Still convinced that on a single inlet valve motor, one should be able to shove an old inlet valve up the choke and as long as the choke was at least the same size as the valve and the carb flows well then bob's your uncle.

[butpug 0]

I don't understand

 

Edit; used wrong quote!!!!!

 

""Anyway, I can't understand why an engine with one choke per cylinder would require a choke size any larger than the area of the valve opening/openings less the area of restriction provided by the valve guides.""

 

The air is stationary before it starts flowing into the trumpet. Somehow you need to accelerate that air to achieve as greater velocity as possible to fill the cylinder before the valve must close. The most efficient way to accelerate air is to accelerate it at a constant rate. Hench the parabolic shape of the ideal trumpet.

 

With regards to bikes v's car engines, flow speed is likely to be very different, what you need to now is mass flow rate. ie speed and pressure (edit; and before someone catches me out, yes temperature too!)

Edited January 11, 2007 by butpug

[butpug 0]

I'd be interested to see how a butterflyless throttle would work on a SI engine

 

 

BMW have made a throttleless SI engine. It basically uses variable valve lift to restrict air flow, I had a link once but now tis gone.

[sutol 0]

Edit; used wrong quote!!!!!

 

""Anyway, I can't understand why an engine with one choke per cylinder would require a choke size any larger than the area of the valve opening/openings less the area of restriction provided by the valve guides.""

 

The air is stationary before it starts flowing into the trumpet. Somehow you need to accelerate that air to achieve as greater velocity as possible to fill the cylinder before the valve must close. The most efficient way to accelerate air is to accelerate it at a constant rate. Hench the parabolic shape of the ideal trumpet.

 

With regards to bikes v's car engines, flow speed is likely to be very different, what you need to now is mass flow rate. ie speed and pressure (edit; and before someone catches me out, yes temperature too!)

 

Yes but the larger the area available for a given volume of air to flow in -- the slower it will travel

[Rippthrough 98]

Yes but the larger the area available for a given volume of air to flow in -- the slower it will travel

 

 

Imagine it like this - the pipe the same diameter as the valve throat will be accelerating the air right at the end of the pipe only.

Say, like a car doing 0-100 in 10 seconds.

 

The exponential shape inlet gradually accelerates the air over a much larger distance.

i.e. - 0-100 in 30 seconds.

 

 

Which one takes the most power to do?

[sutol 0]

Imagine it like this - the pipe the same diameter as the valve throat will be accelerating the air right at the end of the pipe only.

Say, like a car doing 0-100 in 10 seconds.

 

The exponential shape inlet gradually accelerates the air over a much larger distance.

i.e. - 0-100 in 30 seconds.

Which one takes the most power to do?

In my experience which is not an awful lot, I find that opening up inlet tracts too much just reduces low down torque and moves the rest of the power up the rev range. I can't argue too deep into this one because there are area's where I don't know what I'm talking about but I do believe that in sticking oversize carbs on oversize inlets you are just -----

 

 

 

[Rippthrough 98]

In my experience which is not an awful lot, I find that opening up inlet tracts too much just reduces low down torque and moves the rest of the power up the rev range. I can't argue too deep into this one because there are area's where I don't know what I'm talking about but I do believe that in sticking oversize carbs on oversize inlets you are just -----

 

 

I'm not talking about opening the inlet tracts up too much, I'm saying that a bigger carb than the inlet is a good idea because it helps you get a tapered/exponential shape from the throat back.

[sutol 0]

I'm not talking about opening the inlet tracts up too much, I'm saying that a bigger carb than the inlet is a good idea because it helps you get a tapered/exponential shape from the throat back.

 

Yes, I suppose it might but aren't you going to get a step down at the manifold/ head even if you taper it the step will be there and will have to be elongated to turn step into taper

Meaning a lot of work and not always poss!!

 

Am I making sense here or should I go on ebay lol

Edited January 13, 2007 by sutol

[Rippthrough 98]

Yes, I suppose it might but aren't you going to get a step down at the manifold/ head even if you taper it the step will be there and will have to be elongated to turn step into taper

Meaning a lot of work and not always poss!!

 

Am I making sense here or should I go on ebay lol

 

 

You reshape the port as much as you can and then work the manifold from there.

[sutol 0]

You reshape the port as much as you can and then work the manifold from there.

 

Yes, I,ve got you now, the boy racers used to do something similar in the sixties but not as controlled and sophisticated as the way you explain it.

 

What THEY did is to stick a drill in the port and grind out as far as they could reach with the stone or file it out. Then they would stick a bigger carb on it and call it sorted.

All they succeded in doing was to use more petrol and get less torque

We've come a long way then no offence

[Rippthrough 98]

Yes, I,ve got you now, the boy racers used to do something similar in the sixties but not as controlled and sophisticated as the way you explain it.

 

What THEY did is to stick a drill in the port and grind out as far as they could reach with the stone or file it out. Then they would stick a bigger carb on it and call it sorted.

All they succeded in doing was to use more petrol and get less torque

We've come a long way then no offence

 

No, you just put a tapered shape in the port to match with the manifold, you don't just grind it out.