Peter Cobbold Posted April 19, 2017 Report Share Posted April 19, 2017 (edited) 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 Quote Link to post Share on other sites
Waldi Posted April 19, 2017 Report Share Posted April 19, 2017 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. Quote Link to post Share on other sites
oldtuckunder Posted April 19, 2017 Report Share Posted April 19, 2017 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 Quote Link to post Share on other sites
Peter Cobbold Posted April 19, 2017 Author Report Share Posted April 19, 2017 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 Quote Link to post Share on other sites
BlueTR3A-5EKT Posted April 19, 2017 Report Share Posted April 19, 2017 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 Quote Link to post Share on other sites
Peter Cobbold Posted April 19, 2017 Author Report Share Posted April 19, 2017 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 Quote Link to post Share on other sites
barkerwilliams Posted April 19, 2017 Report Share Posted April 19, 2017 Or, perhaps..... https://www.highpowermedia.com/blog/3360/barrel-butterfly-or-slide ....the butterfly lives on to fight another day. Alan Quote Link to post Share on other sites
Peter Cobbold Posted April 19, 2017 Author Report Share Posted April 19, 2017 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 Quote Link to post Share on other sites
GT6M Posted April 19, 2017 Report Share Posted April 19, 2017 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 Quote Link to post Share on other sites
Peter Cobbold Posted April 19, 2017 Author Report Share Posted April 19, 2017 (edited) 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 Quote Link to post Share on other sites
GT6M Posted April 20, 2017 Report Share Posted April 20, 2017 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 Quote Link to post Share on other sites
barkerwilliams Posted April 20, 2017 Report Share Posted April 20, 2017 That collection would make interesting exhibt at IWE Alan Quote Link to post Share on other sites
GT6M Posted April 20, 2017 Report Share Posted April 20, 2017 ok, eer,s a taster M Quote Link to post Share on other sites
Peter Cobbold Posted April 20, 2017 Author Report Share Posted April 20, 2017 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 Quote Link to post Share on other sites
john.r.davies Posted April 20, 2017 Report Share Posted April 20, 2017 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 Quote Link to post Share on other sites
Peter Cobbold Posted April 20, 2017 Author Report Share Posted April 20, 2017 (edited) Twin Roller throttle - no obstruction at wot: http://motorsport.bdg.com.au/roller.html Iris: Edited April 20, 2017 by Peter Cobbold Quote Link to post Share on other sites
GT6M Posted April 21, 2017 Report Share Posted April 21, 2017 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 Quote Link to post Share on other sites
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