Question on air intakes

[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

[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

[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

[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

[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

[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

[Ronnie]

CCC had a good article about this subject 60's - 70's.

[Exminiman]

These may help with the shape, let me know if you need any dims.
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9E4B99E1-063F-4D93-863F-DA297314A4C8.jpeg

[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.

[Exminiman]

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

[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.

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

[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.

[MiNiKiN]

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.

[MiNiKiN]

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.

[Peter Laidler]

That made me laugh out loud Minikin. Great answer!

[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.

[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.

[Exminiman]

Have they been tried on IDAs ?, would expect similar results ?

[OzOAP]

Have they been tried on IDAs ?, would expect similar results ?

IDAs tend to have long venturis so that would need changing