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Ram Tubes / Velocity Stacks


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#1 fredeuce

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Posted 06 November 2011 - 21:40

As I understand the idea behind ram tubes and ram effect science, this is important when you have individual manifold runners on an induction system, be it carbureted or fuel injection.

Is there any benefit to having ram tubes or velocity stacks on say, a conventional style fixed venturi carb on a plenum style manifold?

Edited by fredeuce, 07 November 2011 - 04:24.


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#2 cheapracer

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Posted 07 November 2011 - 03:38

Is there any beneft to having ram tubes or velocity stacks on say, a conventional style fixed venturi carb on a plenum style manifold?


Yes, generally to smooth flow into the carb, negligible ram effect.


#3 Canuck

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Posted 07 November 2011 - 03:57

When you say velocity stack, do you just mean a bell-mouthed opening? Try the Best Bell article for an in-depth look at things. The short answer is yes however.

#4 fredeuce

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Posted 07 November 2011 - 04:43

When you say velocity stack, do you just mean a bell-mouthed opening? Try the Best Bell article for an in-depth look at things. The short answer is yes however.


The answer to your question is yes.

I have always been of the view that the addition of a velocity stack is beneficial for the reason stated by Cheapracer.

To explain a little more I am playing with a little 2-barrel progressive carb. The category of racing is quite restrictive and have to use this carb. Further no increase in throttle valve size or venturi size is permitted. I have added individual velocity stacks to each barrel but it appears to produce negligible gain. This is a seat of the pants assessment at this stage and no dyno testing as yet.

My query is essentially , If done properly what sort of gains can be expected?

Thanks for the link to the Blair article. It looks like some valuable research there. I will need to study that and perhaps back to the drawing boards. :well: :well:



#5 cheapracer

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Posted 07 November 2011 - 05:50

My query is essentially , If done properly what sort of gains can be expected?


More consistent air/fuel metering which may feel a little smoother, better drivability and better fuel economy - sometimes these things can not be seen on a dyno and is just a feel thing.

If gaskets are free then try for an inch thick carb gasket to increase plenum volume, you will notice the difference ...

What car is it, Gemini?


#6 fredeuce

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Posted 07 November 2011 - 06:47

More consistent air/fuel metering which may feel a little smoother, better drivability and better fuel economy - sometimes these things can not be seen on a dyno and is just a feel thing.

If gaskets are free then try for an inch thick carb gasket to increase plenum volume, you will notice the difference ...

What car is it, Gemini?


Cheapy,
It's a Datsun Sunny. The venerable little 1200 motor.

I have incorporated some other mods on the induction which have yielded significant responses. This one however seems at best, rather subtle.

#7 Lee Nicolle

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Posted 09 November 2011 - 11:59

Cheapy,
It's a Datsun Sunny. The venerable little 1200 motor.

I have incorporated some other mods on the induction which have yielded significant responses. This one however seems at best, rather subtle.

Junior Sedan? Be very carefull especially if the car runs at the front.
A ram tube in my experience will always help at least a very small amount obviuosly depending on the carb and intake system. Also be very carefull that any ram tube does not get too close to the airfilter. A lot of airfilters actually do work as a ram tube, or at least shape the air into the carby throat.
Sometimes as cheapy said an increase in plenum works, and sometimes not too. A shorter intake tract will make more top end power in theory but that is often untrue too. Most V8s love a spacer which lifts top end power and mid range torque. Really it is suck it and see and depending on the rules for the category.