K&N air filter with stub stack

[yellowpinky]

I've just got hold of the cone type K&N air filter to go with my HS4 carb. I was wondering if anyone has views on whether or not to use a stub stack to increase air flow? Do they work? I have read mixed reviews about them, none in context of a Minor.

Here is a link to the sale on ebay

http://cgi.ebay.co.uk/Mini-SU-Stub-Stac ... 5d25621981

Thanks<br><br>

[Innovator]

A well designed stub stack increases airflow (there are graphs in Vizards book) He says use one so I would use one and recommend that everybody else does.

He also recommends a rolling road tune up after any modifications to get the carb jetting spot on.........

[bmcecosse]

Alternatively - take a half round file to the mouth of the carb and file a nice radius at the entry point. Same effect (elimination of the Vena Contracta) and zero cost! If the carb uses a 'swing needle' - try the AAA. As long as the plugs are then light beige after a good run - no real benefit on a rolling road.

[yellowpinky]

Well I decided to get one of the stub stacks (same as in the picture on the first post-from ebay total £12.50 inc p&p). I would say that the van is performing a little better, but difficult to tell the difference with such a slight difference, as you'd expect. But every little helps. An additional thing I found that because the stub stack is quite a solid lump, it helps to pull the filter housing to the carb inlet section evenly and firm.

[jonathon]

The stub stack as John says , will benefit air flow if correctly designed. The length of the stack should be balanced with the carb you have. There are long straight versions or full radius ones which are shorter in height but have the same over all length
Generally these will give a longer inlet track which in turn will increase torque, but not necesarily noticable on a Minor carb.

[yellowpinky]

Just adding pictures for future reference incase anyone else is interested.[frame][/frame]

[yellowpinky]

[frame][/frame]

[bmcecosse]

The radius on that doesn't look nearly enough to eliminate the vena contracta!

[linearaudio]

In fact it looks more like an angled cut than a radius, and Vizard reckons that decreases airflow by at least 1.2 percent. He says to go for something more like a 3/8" full radius to give + 5.5 percentish.

[jonathon]

This is more like the trumpets to give good airflow.

[frame][/frame]

[linearaudio]

Lovely piccy! The two in the middle at the bottom, strangely, are the form most likely to give highest flow according to the Bible.

[jonathon]

Yep , we use those on the supercharged Zetec motor.

[bmcecosse]

And it's relatively easy to file that form into the mouth of the carb! It MUST roll back with a full radius - a wee taper like that is useless!

[mike.perry]

No room on my Traveller to fit cone filters to my twin HS2s I had to make do with a pair of K&N pancakes

[horrace]

i know its an old post but where can i get some trumpets like this for my a series

This is more like the trumpets to give good airflow.

[frame][/frame]

[GeorgeHurst]

Have a search for 'stub stack' on ebay and you'll find quite a few

[horrace]

ive found several on ebay but not sure which one, anyone got aaany recs?

[GeorgeHurst]

You should check out what David vizzard has to say about it. From memory, but don't qoute me, it's something like an inch and a half long with a full radius to the end. Bear in mind you have to fit it inside a filter so that pretty much riles out the long ones anyway. I'm just going to file a radius to the mouth of the carb to save cash

[ferret76]

Here's my set-up. A Ramflo 300 series air filter with a stub stack from Calver Special Tuning in the UK. Nice full radius on the stack and lots of room inside the filter for the air to flow into the carb. Stub stacks seem to work better when the filter is centred over the carb inlet, not offset. I have noticed a nice little kick at higher revs.[frame][/frame][frame][/frame][frame][/frame]

[horrace]

thanks ill have alooky round