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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Stub stacks

Has anyone experience with the use of stub stacks inside the original air filters?

There are some quite nice stubs stacks available, for instance these:

http://www.aptfast.com/showitem.aspx?id=101220&name=H2/HS2

In the MGB, stub stacks are used inside the air filters, and according to John Twist and others they give a couple of bhp. I will use the original 948cc engine in my 1961 midget, and would like to keep the original air filters, but at the same time need to extract all the power I can get!

Tore
Tore

Use them!

But they are no wonder cure.
Build your engine carefully.
And tune it properly on a roling road.
Onno Könemann

These are nice:

http://www.med-engineering.co.uk/catalogue/ancillaries/ram-air-kits

John Payne

Tore,
I have those stub stacks fitted to my 'saucepan' filters. I have no idea as to how good they are as they came with the car but Mike Entwisle my local MG tuner and guru liked them.

Ian

I Ball

Thanks everybody. I don´t expect miracles from them, if they give 2 bhp on an MGB engine, logically they should give 1 bhp on an engine half the size and power. But when you have 46,5 bhp to start with, every little counts! The MED stub stacks look very nice.

Tore
Tore

On the MED site that John links us to, they are claiming 4.2 BHP at 5,800 revs on a 1293 A series using an HIF 44 carb. It cost £90 for the full kit of stack, and air filter and fitting kit. Not bad. You can also buy the individual stubbs at £25 each and put them inside your existing filters, so I quite fancy having a go at that.

Bernie.
b higginson

We have been having this discussion on the MGA board. Look up Steve Gyles' very long thread "Improved Airflow Stubstacks", and another one called "dyno test carb stacks". The first is about to fall into archives, so be quick!

FRM
FR Millmore

I had em on my A series, got them from minispares here in the UK

http://www.minispares.com/Product.aspx?ty=pb&pid=33713&title=

a lot cheaper than MED, but don't know if they have them in the smaller sizes...
Rob Armstrong

Those ones shown on the minispares site are so roughly cast, and have such a small radius at their outer edge that I wonder if they even improve flow at all.

I ran a pair of them for some years, but when I bought a pair of the APT ones I was surprised to compare and see what a difference there was, and lost all faith in those cheap ones. The photos from minispares and APT both fail to convey the amount of difference that there is between them.

The MED ones have an even larger radius than the APT ones. I wonder which is better?

It would be great for someone to do a flow rate test of all three, on HS2s, and publish the results.


Norm
Norm Kerr

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.


S Overy

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!

Malcolm
Malcolm Le Chevalier

Quite correct. Nearly all the positive flow rates above are within one percent or so of total change, so the shape is of only minor importance, and has much more to do with looks or correctness for period.
S Overy

My base plates are 1/4" thick aluminum. I knew that a sharp edge was bad, so I opted for a 1/4" circular radius. I doubt they improve HP to any measurable extent (never done any comparison).


Trevor Jessie

This thread was discussed between 26/09/2011 and 28/09/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.