barrel throttle

[Peter Cobbold]

One for the racers - reduces wot air flow loss by 37% compared with butterfly

http://papers.sae.org/2017-01-1078/

but hidden behind a paywall but theres a preview.

Peter

Edited April 19, 2017 by Peter Cobbold

[Waldi]

I assume this does not mean a 34% gain in massflow through the entire engine, as the butterfly is only one of a series of restrictions.

But 34% potential improvement on one component is significant, and I would not have thought so.

[oldtuckunder]

I know from data logging Inlet Manifold pressures that at WOT above 6K with twin 1.5" CD's that vacuum starts increasing quite fast, and that purely by fitting 1.75" this effect disappears, how much is pure size restriction and how much the butterfly set up restriction I don't know.

 

However a rough calculation shows that on a 1.5" carb at WOT with no butterfly the max area is 1017 sqmm but with butterfly installed its only 795 sqmm, so there is a theoretical 25% increase in area available by just removing the spindle, and as the bulk of this restriction is in the middle of the throat where air speeds/volumes are greatest it may have a bigger effect than just that based on pure area.

 

Alan

[Peter Cobbold]

Yes inlet valve by far the biggest obstruction to flow. But the higher the pressure at its mouth the better for power.

The butterfly loss may well be the largest within a carb, whether SU or Weber types. But finding data is not easy

 

I know from data logging Inlet Manifold pressures that at WOT above 6K with twin 1.5" CD's that vacuum starts increasing quite fast, and that purely by fitting 1.75" this effect disappears, how much is pure size restriction and how much the butterfly set up restriction I don't know.

 

However a rough calculation shows that on a 1.5" carb at WOT with no butterfly the max area is 1017 sqmm but with butterfly installed its only 795 sqmm, so there is a theoretical 25% increase in area available by just removing the spindle, and as the bulk of this restriction is in the middle of the throat where air speeds/volumes are greatest it may have a bigger effect than just that based on pure area.

 

Alan

Alan,

That sound to me its a butterfly loss, assuming your take-off for the sensor is on the manifold ( ie you're reading MAP)

The choke tube depression before the butterfly should be failry constant. But if the 1.5 piston is fully lifted above 6k the constant depression feedback will cease and choke tube depression increases as the mouth 'entry loss' continues to climb. A trumpet can eliminate much of this. The 1.75 may still be operating without the piston becoming fully lifted.

 

 

The butterfly does seem to make a big hole in the flow, even at wot. I have seen cfd results where the bfly was built up so that it has an aerofoil shape incorporating the spindle. And flattening the centre of the sprindle helps also. Try google images for butterfly + cfd.

Peter

[BlueTR3A-5EKT]

My memory of driving a car with slide throttles was that they were ON or OFF - a complete horror in traffic.

Think Amals on a Mini

Here is a useful link to pdf docs of the period

http://www.mk1-performance-conversions.co.uk/technical_carb.htm

 

Peter W

[Peter Cobbold]

My memory of driving a car with slide throttles was that they were ON or OFF - a complete horror in traffic.

Think Amals on a Mini

Here is a useful link to pdf docs of the period

http://www.mk1-performance-conversions.co.uk/technical_carb.htm

 

Peter W

Peter,

Their 'barrel' valve is of this type, different forma slide throttle:

http://www.ctgclean.com/sites/www.ctgclean.com/files/wp-content/uploads/Ball-Valve2-1024x434.jpg

 

A butterfly is fascinating. The flow velocity around its edge is choked - sonic - up to about 30degrees of opening. This means the pressure seen by the inlet valve is about half of atmospheric for the first 30 deg of operation. The mass flow rises but the iv pressure is held constant. I think that's what make the b'fly progressive.

 

Peter

[barkerwilliams]

Or, perhaps.....

 

https://www.highpowermedia.com/blog/3360/barrel-butterfly-or-slide

 

....the butterfly lives on to fight another day.

 

 

 

Alan

[Peter Cobbold]

Or, perhaps.....

 

https://www.highpowermedia.com/blog/3360/barrel-butterfly-or-slide

 

....the butterfly lives on to fight another day.

 

 

 

Alan

It has certainly stood the test of time !

A butterfly has a useful secondary effect - at part throttle the sonic air flwo around the edges smashes up the fuel droplets. A slide presents a flat surface to droplets from the jet- not so good. Barrel- narrow gaps and high speed air - should help.

 

Peter

[GT6M]

Ahhh butt, !!!

 

its oksaying its gonna get moer air in,

butt, after 3/4 throttle,ish, and 3500 + revs

 

then yer engine cant consuum moer air

as is shown by the masses of EFI RR charts

 

after thee,s figs above, the fuel take is as near as damit for the whole top part oft fuel map

 

 

And, oot of curiosity for some, Triumph actually med a revolving throttle set up

but never actually got aroond t,fittin it

 

 

 

M

[Peter Cobbold]

Ahhh butt, !!!

 

its oksaying its gonna get moer air in,

butt, after 3/4 throttle,ish, and 3500 + revs

 

then yer engine cant consuum moer air

as is shown by the masses of EFI RR charts

 

after thee,s figs above, the fuel take is as near as damit for the whole top part oft fuel map

 

 

And, oot of curiosity for some, Triumph actually med a revolving throttle set up

but never actually got aroond t,fittin it

 

 

 

M

Markus,

where did you find that? was it for the PI?

Cant help thinking it might be bit stiff to open with a bar of pressure across it. Heavy right foot needed to open it from over-run.

Would be intresting to do a RR run with a removable b'fly..... there could be a 5% pressure drop across it. And that should improve VE by similar percentage.

Peter

Edited April 19, 2017 by Peter Cobbold

[GT6M]

It was destined for a LeMans car as far as I no off,

butt the one to say, would be Slim Boy Pearson as they call him,

 

he got some intresting stuff

 

like a 5 speed box TR box oe wid an attachment ont end

a transaxle

a semi direct injection heed

a heed wid round ex ports

V8 PI inlet manis

 

all Triumph experimental

 

M

[barkerwilliams]

That collection would make interesting exhibt at IWE

 

 

Alan

[GT6M]

ok, eer,s a taster

 

M

 

 

[Peter Cobbold]

It was destined for a LeMans car as far as I no off,

butt the one to say, would be Slim Boy Pearson as they call him,

 

he got some intresting stuff

 

like a 5 speed box TR box oe wid an attachment ont end

a transaxle

a semi direct injection heed

a heed wid round ex ports

V8 PI inlet manis

 

all Triumph experimental

 

M

But no supercharger....grrrrr.

 

There's a diy teflon-lined slide throttle here:

http://www.rotaryeng.net/slide-throttle.html

 

Peter

 

Peter

[john.r.davies]

Barrel throttles not entirely unknown:

http://www.jenvey.co.uk/faq/barrels-or-butterflies

 

http://www.burtonpower.com/titan-roller-barrel-throttle-body-duratec-he-i4-tbi4.html

 

http://www.raceline.co.uk/products/part_section.asp?SectionID=13&CategoryID=1

[Peter Cobbold]

Twin Roller throttle - no obstruction at wot:

http://motorsport.bdg.com.au/roller.html

 

Iris:

Edited April 20, 2017 by Peter Cobbold

[GT6M]

I like the bit aboot self cleaning of the slides,

rubbish,ok in a lab enviroment, or short term use

 

butt, try that valve in a house system, esp doonn south,

it,ll clogg up in nee time at all, an leak like a mad

 

Unless yer engines gonna be going into 14000 + revs

a barrel throttle is no as good as a butterfly

 

M