Ram pipes

[Ignatzcatz]

I'm on the hunt for a set of velocity stacks, more commonly known as ram pipes, for my Zenith 40 TINs. I know they are not the greatest things to run on the road but I have a clearance problem which makes them rather necessary. If anyone could point me in the right direction to obtain a set I would be most grateful. One small thought in this regard is, would Weber stacks possibly fit the Zeniths?

[fetuhoe]

All Zenith and Weber carbs were fitted with Velocity Stacks that sit inside the filter housings. many of the Zenith Stacks were made from Plastic and burn quite well during a backfire.

Weber Stacks are steel and will it the Zenith. We have new parts in stock.

If you plan to run the car on the road without filters then a dusty day could well wreck your piston rings and I would worry.

[stretch]

Graham,

don't be tempted to run those open. You might look cool, but your wallet won't after a re-build..!

Options : K&N filters or tea strainers. I am using my own "homemade Aluminium housings as i hate the look of the K& N one's.

Chris, are your pipes steel or Aluminium.? Care to post up pictures and prices? Interested if Aluminium.

Dave

[fetuhoe]

Dave,

They are standard steel. We are planning to make Aluminium at some time but.......

[Magnum]

Hi

FWIW I was interested in the very cool looking "tea-strainer" solution, however after reading up I determined that apart from looking very cool, they aren't actually a solution!

They're a problem - they do not really filter out the bad stuff, and they lead to detrimental air flow changes (reduction/pattern). It may not matter to a gently used vehicle though......somebody will be along shortly

That's as technical as it gets here, but there is information out there!

[sfl993t4]

Hi ignatzcatz,
I went through this with the maserati project and found that https://www.carbparts.eu/ were good and made me some custom aluminium trumpets (for clearance I needed shorter than stock).
For the look I went with mesh screens from Bill Hirsch in the US (he makes the ones here: https://weberjets.com/index.php?page=sh ... t&Itemid=2 )
As other have mentioned, be aware that any mesh filter significantly restricts open area (since the wire takes up at least 40%) and so its worth going for domed ones if possible and certainly not the low profile.
Its fair to say that a multi carb filter on a backing plate like these:
http://itgairfilters.com/category/megaflow/ will always flow better than a strainer, but it depends what look you want (and these cars are toys / jewellery anyway and so ultimate power may not be the main consideration).
Looking forward to seeing your hot rod one day
Steve

[Ignatzcatz]

Thanks for all the info chaps, it's only the rear pair that have clearance issues so I will have to cut into the inner skin of the engine cover so it can close over the back two ram pipes, when I get them. I note your concerns over unfiltered air reaching the engine internals and wouldn't want to run things 'au naturel' so to speak. What I hope to be able to do is construct some filter arrangement that is attached to the engine lid so that when it is closed down the intake would be surrounded and sealed by filter material. But the main deal is to open the engine lid and see six anodised aluminium ram pipes looking at you.

[Lightweight_911]

.

I had similar problems with my 904 - no room under the rear body work for any 'off the shelf' air filters.

I managed to find (& bought) some shallower K&N filters which fitted - in conjunction with short alloy trumpets - but there still needs to be a minimum of (from memory) ~25mm 'free space' above the tops of the trumpets so as not to severely affect the air flow & there wasn't (evidenced by affecting the engine breathing).

In the end I resorted to using alloy trumpets with medium-sized holes in the mesh & covered these with Ramair foam sock filters which only took a few seconds to whip off if I parked the car with the back open to display the engine.

In addition I made up some cheap covers to slip over the trumpets if the back was open for any length of time.

[anglophone1]

We are putting Webers on my 924 race car- I bought a complete set with manifold etc. from Mike Pierce whilst at Rennsport last year.
They came with open trumpets - and as they will be side facing under the bonnet in theory should be OK.
However it is (mostly) road legal and I do plan to use it on the road when Jaffa is in UK, so some screening is probably a good idea - keep out any West Cork crap!
Thanks for link- the domed covers will be ideal!
C

[smallspeed]

Ramair make some nice aluminium velocity stacks, available in a variety of lengths and fitments - about £10 a piece I think (it was a while ago I ordered the ones in the picture below) from ebay

A couple of rough rules -

- Have the diameter of the inlet (so 40mm on an IDF40) as clear space all around the perimeter of the velocity stack lip, and above it as a minimum. Something like the 911 "rain hats" where you have a solid face above the velocity stack and a filter around the outside work really well, OR a remote filter, then a plenum (which is hard to do on an older 911 without making it look like a newer one)

- Have the capacity of the engine as a minimum volume (ideally 1.5x) inside the filter. So if you have a 2.0 litre flat-four engine, you want 1 litre volume (minimum, 1.5 litre preferable) inside the filter on each side, which should be easily achievable following rule #1 on a 911



Unfortunately its often a case of packaging vs. the "ideal" solution, however if you have the space, start with a length calculation for the whole inlet tract and tweak from there. They will effect the torque curve of your engine and at an extreme, can turn a peaky small engine into a diesel! Getting them right can yield significant improvements in both outright power/torque and also drive-ability

Clive - not sure how much space you have, but on an inline engine you could probably get the best of both worlds using something along the lines of this, where the air filter is mounted at the front, then feeds the throttles via a plenum. You may have to fabricate yourself if nothing is available off the shelf!

[fetuhoe]

The Ramair velocity stacks look good but there are just two small issues that need to considered

The diameter of the intake at the top of a Weber IDA/Zenith 40TIN is 46mm and I think that the Ramair stack is 45mm.

I don't think this ill make much difference but it isn't ideal.

Also when you fit a Velocity Stack into an Airbox I believe that you need a minimum gap of 30mm between the end of the stack and the Airbox.

If this distance is too small then the airflow into the carb will be significantly affected.

If we have another long dry summer then the amount of airborne dust will be quite high and it tends to be these relatively small particles that will damage rings and bores.

[smallspeed]

The Ramair velocity stacks look good but there are just two small issues that need to considered
The diameter of the intake at the top of a Weber IDA/Zenith 40TIN is 46mm and I think that the Ramair stack is 45mm.

If they're of interest let me know - the ones in my picture are 40mm diameter as they're fitted to 40mm throttle bodies, but I can measure and give you an idea of wall thickness. They're fairly chunky so I think you could turn 1mm off the diameter of a 45mm one to suit..

Also when you fit a Velocity Stack into an Airbox I believe that you need a minimum gap of 30mm between the end of the stack and the Airbox.
If this distance is too small then the airflow into the carb will be significantly affected.

This is where I was going with the 1x diameter clearance - its quite important to have that space all around the lip of the velocity stack otherwise the restriction is quite evident. This is why the slip over sock-filters and the slip over multi-trumpet filters ram air and people sell are a poor solution. The larger filters with a back-plate and internal gauze to maintain space around the velocity stack are much better

[911hillclimber]

Porsche never followed that rule on the flat 6.

My K&N filters on my PMO's were designed for the 911 installation and the clearance from the underside of the top to the edge of the trumpet is about 20mm...choke size is 50mm.

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[fetuhoe]

The impact of velocity stack length on engine performance is quite well established with longer trumpets generally being beneficial on mid band to low end power development.

Sadly the design of air filters/plenum chambers is often compromised to suit a specific installation.

A 20mm gap between the bulkhead and the end of the velocity stack will have some impact on the air flow behaviour of the intake due to turbulence and/or resonance

A standard Porsche 911 plenum with a 55mm velocity stack has around 50mm clearance to the bulkhead.

I believe that the PMO Watershield Filter is around 82.5mm deep so with a 55mm velocity stack the clearance should be around 27.5.

This is the same depth as the K&N 56-1770-1 which is longer than the PMO and uses a different element.

I generally believe that 27.5mm is a bit too close but better than 20mm although the real impact depends on the engine characteristics.

We have made our own Filter Bases from pressed steel and Lids using glassfibre with a Fire retardant resin.

The filter is a modern multilayer foam and is 90mm deep which produces a 35mm clearance which is still marginal but is a slight improvement.

This filter also its a PMO Watershield Housing which isn't available from K&N and we also have the longer stand offs.

Back in the days of Rallying Escorts there was always an issue with Air Filters, velocity stacks and bulkhead position and having a 'reasonable' clearance always produced a performance improvement.




There is an interesting article on velocity stack length.

https://waset.org/publications/10007277 ... motorsport

[smallspeed]

That's an awesome article! I've posted this before, but its an extreme example of what a difference the design / length can make -

http://www.emeraldm3d.com/throttle-body ... ntake.html