MG Midget and Sprite Technical Ram pipes BBS discussion at MG-Cars.info

MG Midget and Sprite Technical - Ram pipes

What are the collective thoughts on whether these are any use for a road going car? Do they add much in the way of performance other than making induction louder? No filtration so more engine wear? Can they be fitted inside air filter cartridges and if so are there any benefits? Shorter the ram pipe, the higher up the rev range any improvements are apparent? Is it because they're nice shiny things that they appeal? - Yes. Engine is standard with 1.25" HS 2 SUs, pancake air filters and with Maniflow LCB and RC40.

Jeremy MkIII

Yep, except I have stub stacks. Mine are like these, inside K&N air filter. Actually I only have one now, as I swapped to a single hif44. "The K&N Stubstack is designed to increase the airflow of carburetors, by decreasing the restriction around the choke horn." https://www.knfilters.co.uk/racing/stubstacks.htm As for how much difference they make, I think Vizard has a section suggesting they are worth it. But when I bought mine they were dirt cheap. Not sure I'd fork out now, as I doubt they add *that* much oomph. Lol. I think Vizard says the type you show, would be bad in a pancake, because the air flow is side entry inside a pancake, and so is slowed down. Whereas it is helped by the rolled stubstacks. You could improve it though with deeper pancakes. Here's a mini forum discussion on a new version of stubstacks. https://www.theminiforum.co.uk/forums/topic/338253-new-hif-44-stubstack-design/

anamnesis

The A Series guru David Vizard, whose book was the bible for my engine build about 20 years ago, wrote a whole chapter on ram induction. Basically he said the main benefit was to have a curved intake mouth, as a sharp edge reduces the effective diameter. Initially I followed this by making a bell mouth out of resin inside the K and N filter. Otherwise known as a stub stack. I still have that, but I now have a long ram pipe between the filter and the carb. To be honest I doubt if it helps a great deal, for two reasons. Firstly, my engine is an original 948, albeit bored to 998 and with the usual performance upgrades. It's quite well known that ram induction works better on the bigger engines. Secondly, I'd be better off having the extra length between the carb and the manifold. This is what the flow bench testers have found. My impression is that the engine is a bit more flexible, and will pull fairly solidly from 2000 rpm. Meanwhile I'm working on modifying the manifold to increase the length, but it's quite difficult to do. Of course, my experience is with a single HIF 44, and it will probably be more complicated to apply this to twins. But don't think about doing without filters, or your engine life will be merry but short. Get a pair of K and Ns and put bell mouths inside them.

Les Rose

Archive thread. "Stub stacks" https://mg-cars.org.uk/cgi-bin/or17?runprog=mgbbs&access=&mode=archiveth&subject=97&subjectar=97&thread=2011092616483031637 28 September 2011 at 12:58:49 "The shape of them is very, very important. There's a diagram in Vizard's book regarding flow and shape, but for those that don't have it, here it is. The radius of the edge is probably the most important part of the shape, as a sharp or poorly formed edge will make things worse." But also, "I have a paper about the design of such things. It looked at a plain pipe end and radius, eliptical and aerofoil profiles. Long story short it concluded that it doesnt really make much of a difference what profile you use, as long as there are no sharp edges. Anything other than a straight pipe end is a good improvement!"

anamnesis

This is a Paddy Gaston period manifold that is said to be good for providing extra torque.

Alan Anstead

Thank you for all the info and links. Error in my original posting. Not pancake but standard saucepan air filters. I'd like to try the cast K&N Midget twin carb casting set up but they're NLA and used examples are like rocking horse poo. Unless anyone knows of one for sale? Anyone tried these from MED? They come with machined aluminium stub stacks (similar to yours Anam and your link?) From the diagram it seems the elliptical shape is the most efficient? Nor cheap at £155 but cheaper than two single K&Ns for HS2s at £117 from Demon-tweeks. 3D printing is the future P Peters, maybe we could make replicas of Alan's inlet manifold?

Jeremy MkIII

Ram pipes, yes, got those. The longer they are the lower the torque peak. This is at 160bhp at 7650 from a 1600.

Rob Armstrong

oops, forgot photo ...

A de Best

Jeremy I've found most of the K&N filter. This is one that I converted to a cold air box many years ago, replacing the filter element with a collector box. I haven't found the filter element yet, but it's out there somewhere. As you can see, the 'Midget' cover plate met with a nasty accident!

Dave O'Neill 2

It’s a nice straight line, but a bit rough close up.

Dave O'Neill 2

This thread was discussed between 30/05/2025 and 09/06/2025

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