Simple Tunnel ram Question

[j-c-c]

Is the fact that a typical Tunnel ram uses gravity more effectively then any other NA manifold give it an inherent notable advantage?

I guess vertical IR stacks might share also share the same advantage regarding gravity.

[swampbuggy]

A fair question i guess, in 45 years of being around hot rods i do not remember talk about your question. It may however hold a little merit ????? Mark H.

[In-Tech]

It has nothing to do with gravity.

[Tuner]

It has nothing to do with gravity.

If the engine was upside down it would. Standard air weighs about 1 lb per 13 CFM and that mass has to be accelerated to move it through the engine, so, if it were normal side up or upside down, what ever acceleration force will be plus or minus the one G of Earth's ambient gravity. Side draft, it wouldn't matter.

[In-Tech]

Google says:
Air weighs 0.0012929 gram per cubic centimeter or 1.2929 kilogram per cubic meter, i.e. density of air is equal to 1.2929 kg/m³. In Imperial or US customary measurement system, the density is equal to 0.080713 pound per cubic foot [lb/ft³], or 0.00074734 ounce per cubic inch [oz/inch³] .

I would think we can agree, without radials and upside down engines, what really matters is atmospheric pressure and the ability to use that to fill the engine as quickly and efficiently as possible. A tunnel ram and side draft does both with the least turn. Now if the fuel was introduced at the top of a tunnel ram like a carb does and it was on nitro, I suppose gravity might matter a bit so I'll digress.

[j-c-c]

Thanks guys, but not sure weight matters much, as a we all know, discounting air resistance/drag, a feather and a bowling ball both fall at the same speed, and we also are more then likely talking wet flow regarding density, and all those related concerns.

Thought i would ask, since I have never read this factor discussed.

Maybe the key word in my question was "notable".

[n2omike]

Most of the charm comes from straight runners and good fuel distribution with the 2x4 setup putting a carb straight over each end of the manifold.

[n2omike]

Most of the charm comes from straight runners and good fuel distribution with the 2x4 setup putting a carb straight over each end of the manifold. The 'gravity' aspect would be a minor player, but doesn't hurt.

Edit... Sorry, double post.

[MadBill]

FWIW, many engine have (and more had) up-draft carbs...

[BOOT]

Runner length and wave tuning is another factor. In my opinion not so much even fuel distribution but more quality, as it's 2x the N&S. I like to think of a NA engine as a kinda drain and swirl helps fill the cylinder.

[cardo0]

Making air turn produces at pressure loss/acts as a restriction. Fewer turns the better. Tunnel ram has it over a cross ram in that respect as far as I'm concerned.

Up draft carbs? Yes majority of general aviation aircraft use them and a bunch of other idio devices that make no sense on a performance motor. Updraft air cooling too but I don't see anything at the strip using that. Well they do use magnetos but that's because they use 2 of them for reliability and simplicity.

[CharlieB53]

Updraft carbs may have a slight advantage in atomization as larger droplets may be slightly restricted by gravity simply by their weight until more evap lessens it’s weight.

This could be a tough one to measure and prove.

Another possibility may be less prone to flooding.

I know I’ve seen lots of industrial updrafts and older in/lines use them. Ran flawlessly for years.

[cardo0]

Let the updraft carb die! Ish! We're talking cylinder filling advantages of a tunnel ram meaning better flow into the cylinder. Updraft intake is so ass backwards I don't know how someone could even compare the two?

Give me a tunnel ram with 2 carbs on anything, over anything except maybe individual runner carbs.

[n2omike]

Updraft carbs may have a slight advantage in atomization as larger droplets may be slightly restricted by gravity simply by their weight until more evap lessens it’s weight.

This could be a tough one to measure and prove.

Another possibility may be less prone to flooding.

I know I’ve seen lots of industrial updrafts and older in/lines use them. Ran flawlessly for years.

Very good, often overlooked points! Not everything is a race car!

[Tuner]

The point in mentioning an upside down engine was to illustrate the need to accelerate the weight of air from zero to port velocity. 650 HP requires approx. 1000 CFM. 1000 cubic feet of standard air weighs approximately 75 lbs. and will be accelerated from zero to approximately 300 fps. The acceleration force of gravity is always there and to compare updraft to down draft was to illustrate the intake air's weight is either being lifted or falling. Accelerating the air from zero to port velocity is a portion of an engine's pumping loss. In a tunnel ram with vertical down-draft runners, gravity assists the acceleration of the air.