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Question on air intakes
Posted: Sun Nov 10, 2024 11:08 pm
by 360gts
During an outing at the local track this year I noticed a lot of the competitive classes (eg Formula Fords etc.) were using an air intake on the webers like the one on the right in this picture.
So, I decided to turn one up and thought I'd get some feedback on which one might give the best power. Standard intake is on the left.
1071Bob...are you there?
Cheers
D
Re: Question on air intakes
Posted: Mon Nov 11, 2024 12:15 am
by timmy201
The only way to know is to test them on the dyno. The length, shape, bellmouth all play a part. The length will change where the power gain from the ram pipe is, some will boost lower rpm and others higher rpm
There’s a fella in NZ who does lots of dyno testing (on a Toyota 4 cylinder engine) and has done a few tests on intake ram tube length and style.
https://youtu.be/G8L9_XO3iCw?si=yIBHRJTYEx6yOuhq
https://youtu.be/kSM0JRGRYTM?si=n2zCIFae2xiCnUjo
https://youtu.be/W_-4AXGTpYc?si=7WR1SBkpuOqTzUmY
Re: Question on air intakes
Posted: Mon Nov 11, 2024 7:12 am
by Exminiman
Nice work Dermot, the rounded one should be best, Vizard did quite a bit on this as well.
As far as I understand it the broader and more rounded the inlet the better it will flow as it gives a smoother flow into the carb.
Inversely, the sharp trumpets see a much smaller area of available air, imagine the air flow outside of the diameter of the trumpet end, how much smaller it is.
The length is important as well as regards Ram charging, vizard did lots on this in Yellow book
Re: Question on air intakes
Posted: Mon Nov 11, 2024 8:35 am
by roger mcnab
hi
ram tubes do make a difference with my bikes in the distant past i used them a lot also with my yamaha race bikes i made spacers to move the carbs further back from the engine with good resultsthe 125 was very good with these fitted it was compettive even in the 250 class amaroo was its best results usually 2nd place in the results the first time i fitted them we went to bathurst but was not allowed to race as of the noise funny enough
it was louder with the spacers off traced to clogged mufflers so new ones and it was all good that quite they could not believe it was same bike
dyno testing is good for getting the best every thing with engines is always a compromised by the application and use un fortunately
cheers roger
Re: Question on air intakes
Posted: Mon Nov 11, 2024 10:51 am
by MiNiKiN
This is my design and realisation. For obvious reasons, only partially suitable for Weber carburettors.My stacks are designed using a tractrix curve. Yet not Dyno tested, but they already sound lovely.
Actually designed for H4 not HS2, as can be seen.
MiNiKiN_Tractrix_Bellmouth.jpg
Re: Question on air intakes
Posted: Mon Nov 11, 2024 11:26 am
by Peter Laidler
I say that air intakes is just another play on plumbing for air. Air, like water and even humans always like and take the line of least resistance. Air and water as Bertolli told us many years ago, don't like sharp edges that cause eddies and currents or other disturbances. The smoother you can make the air flow - and liquids - the better they perform. And more to the point, the greater the volume at the other end.
Just as I was taught it
Re: Question on air intakes
Posted: Mon Nov 11, 2024 4:57 pm
by Ronnie
CCC had a good article about this subject 60's - 70's.
Re: Question on air intakes
Posted: Mon Nov 11, 2024 8:01 pm
by Exminiman
These may help with the shape, let me know if you need any dims.
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03A476F4-7254-42D1-8A8F-028A4AE05434.jpeg
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9E4B99E1-063F-4D93-863F-DA297314A4C8.jpeg
Re: Question on air intakes
Posted: Mon Nov 11, 2024 9:49 pm
by MiNiKiN
This is Ian Osborne's (OAP in co-operation with Thunder productions) take on weber stacks:
45-06.jpg
They look a bit Carlos Fandango but not bad if you can stand the 3D-Print-Look.
Re: Question on air intakes
Posted: Tue Nov 12, 2024 8:51 am
by Exminiman
MiNiKiN wrote: ↑Mon Nov 11, 2024 9:49 pm
This is Ian Osborne's (OAP in co-operation with Thunder productions) take on weber stacks:
45-06.jpg
They look a bit Carlos Fandango but not bad if you can stand the 3D-Print-Look.
Wow, do the well ? There is a whiff of Flash Gordon about them
Re: Question on air intakes
Posted: Tue Nov 12, 2024 10:55 am
by MiNiKiN
Exminiman wrote: ↑Tue Nov 12, 2024 8:51 am
MiNiKiN wrote: ↑Mon Nov 11, 2024 9:49 pm
This is Ian Osborne's (OAP in co-operation with Thunder productions) take on weber stacks:
45-06.jpg
They look a bit Carlos Fandango but not bad if you can stand the 3D-Print-Look.
Wow, do the well ?
I suppose so. But Mr. OAP knows probably more ...
There is a whiff of Flash Gordon about them
indeed! Now that you say it
Re: Question on air intakes
Posted: Tue Nov 12, 2024 11:24 am
by Peter Laidler
To be honest, and I'm certainly no aerodynamicist, but they look like they're based on something out of Dr Who - or Star Wars.
Are there TWO intakes there, an outer one pulling air close to and an outer smaller diameter one pulling air in from slightly further away. Both feeding into one. Not my idea of a clear and unobstructed airflow.
What I always remember about air/gas flow is the cheat......., where if you're stuck, you can always puff out the answer or group discussion by throwing in '...all the D's...'. Ducting, depression, down-draughting dispersion, deflection and plenty more... and all of those that relate to air flow.
Re: Question on air intakes
Posted: Tue Nov 12, 2024 12:20 pm
by MiNiKiN
Peter Laidler wrote: ↑Tue Nov 12, 2024 11:24 am
To be honest, and I'm certainly no aerodynamicist, but they look like they're based on something out of Dr Who - or Star Wars.
Are there TWO intakes there, an outer one pulling air close to and an outer smaller diameter one pulling air in from slightly further away. Both feeding into one. Not my idea of a clear and unobstructed airflow.
What I always remember about air/gas flow is the cheat......., where if you're stuck, you can always puff out the answer or group discussion by throwing in '...all the D's...'. Ducting, depression, down-draughting dispersion, deflection and plenty more... and all of those that relate to air flow.
They optimise air flow in different throttle flap positions. The smaller cone obviously serves at part throttle.
Re: Question on air intakes
Posted: Tue Nov 12, 2024 2:19 pm
by MiNiKiN
MiNiKiN wrote: ↑Tue Nov 12, 2024 12:20 pm
Peter Laidler wrote: ↑Tue Nov 12, 2024 11:24 am
To be honest, and I'm certainly no aerodynamicist, but they look like they're based on something out of Dr Who - or Star Wars.
Are there TWO intakes there, an outer one pulling air close to and an outer smaller diameter one pulling air in from slightly further away. Both feeding into one. Not my idea of a clear and unobstructed airflow.
What I always remember about air/gas flow is the cheat......., where if you're stuck, you can always puff out the answer or group discussion by throwing in '...all the D's...'. Ducting, depression, down-draughting dispersion, deflection and plenty more... and all of those that relate to air flow.
They optimise air flow in different throttle flap positions. The smaller cone obviously serves at part throttle.
They provide better airflow and in particular help to tame cammy engines in the midrange of revs, with considerable power increase compared to other stacks. But I have to stop here, because otherwise Ian will make me an unresistable offer to become his PR-manager.
Re: Question on air intakes
Posted: Tue Nov 12, 2024 5:13 pm
by Peter Laidler
That made me laugh out loud Minikin. Great answer!
Re: Question on air intakes
Posted: Tue Nov 12, 2024 7:58 pm
by timmy201
Those twin ram pipes are specifically designed to provide a better signal to the auxiliary Venturi on the Weber.
IMG_2525.jpeg
MED make a similar system called DCR. As with the OAP pipes above they’ve been proven on the dyno
The DCR system has been dyno tested on numerous race engines with the Weber 45 DCOE carburettor and produced a gain of between 4 to 6bhp over the standard-fitment ram pipes when correctly set up.
The central velocity stack creates more airflow into the auxiliary venturi, which will increase the air speed over the venturi and in turn amplify the mixture signal, bringing the engine on to cam earlier.
On the outer stub stack, an optimised elliptical form smoothes the airflow into the choke area, creating more bhp throughout the range.
IMG_2524.jpeg
Thr most important part is picking the correct length and style ram pipe to suit your particular application.
Re: Question on air intakes
Posted: Thu Nov 14, 2024 4:47 am
by OzOAP
The tested and proven Thunder Productions Duel Cone Stacks speed up airflow into center venturi, giving better fuel atomization.
Bigger gains on 'cammy' engines.
On my engine, due to better atomization, faster fuel burn, we found gains from also backing a couple of degrees of timing out if it.
Air speed over air flow....the same as huge port cylinder heads are not the best way to get power.
Re: Question on air intakes
Posted: Thu Nov 14, 2024 7:00 am
by Exminiman
Have they been tried on IDAs ?, would expect similar results ?
Re: Question on air intakes
Posted: Thu Nov 14, 2024 7:06 am
by OzOAP
Exminiman wrote: ↑Thu Nov 14, 2024 7:00 am
Have they been tried on IDAs ?, would expect similar results ?
IDAs tend to have long venturis so that would need changing
