Clubman pipe basics
Author: Roger Polak

 

Australian karters have been using the AKA39 Clubman pipe for 12 months now and so we thought we would take a quick moment to spell out some of the things we have learned.  Now we won't pretend to give you earth shattering guidance here that will improve your performance out of sight, but here are some observations from the MKC team that might help you get more from the AKA39 pipe.

 

Gearing

A year ago the prediction was that using this pipe (and the heavier S conrod) would result in the use of smaller rear sprockets and lower engine RPM.  By and large this has been the case, but not always.  We have noticed that we rev our engine less than we did in the pre-control-pipe-days.  But there are exceptions.  And that is really something that all Clubman karters need to keep in mind.  You need to be willing to try gearing and pipe lengths that are vastly different to what you might think. So try adding a tooth or two back on to gain bottom end power and then compensate with a shorter exhaust.  This sometimes works a treat.

 

Header pipes

So far we've found the big bore, short length stainless Powemac header to be a pretty good thing.  The Raap one is ok too and soon we'll be trying a few other variations.  But basically you can't go too far wrong with the Powermac header pipe.  Keep an eye on the mounting flange though, which tends to bend and in extreme cases it can leak quite badly.  Bend it back to straight in a vice using a large shifter spanner if that happens.

 

Pipe length

Beware here that not everyone measures the length the same way, and this can throw your pipe length out if you are using someone else's settings.  People will either measure from the flange of the header or from hard up against the aluminum part of the block.  The latter mentioned here is how we do it at MKC.  So how you measure your pipe is with a flexible tape measure that is pushed up hard against the engine then stretched around, past the flex to the first weld on the pipe (where the body of the pipe becomes a cylinder).

Using this method you will most commonly hear of values of around 410 to 420mm.  And that's close to the recommended setting.  But it won't be the optimum length for every class at every track.  When using the AKA39 pipe you have to be prepared to make big changes to see a result.  So when you are shortening the pipe (to gain top end power)  make changes of 10 or 20mm.  Don't fiddle around with 1 or 2 mm changes.  It won't make a significant difference.  And don't be scared to go well into the sub 400mm range when conducting your testing.  At some tracks a really short pipe will work best.  This will also depend on your engine builder's setup too.

 

Myths exposed

Myth1: The pipe makes my engine run hot.  In our experience things are about the same or the engines run slightly cooler.

Myth2: The pipes vary heaps! We have used many pipes throughout our team and not found big differences.  They all seem to be about the same.

Myth3: The pipe slows the class sown.  Definitely not the case.  We are going as fast or even faster than under the previous rules.  You can make this thing work really well, but it takes work.

 

Bottom line

Whilst the AKA39 has successfully brought everyone's exhaust into line, it can be a tricky pipe to gain the last bit of power out of.  Just like in most things in karting you need to approach testing with an open mind and not get caught out by thinking "It worked at Oakleigh, so it should work here!".  Also use info from other competitors you are friendly with or talk to people like us to get an idea on where to head with your pipe length and engine setup.  It comes back to the old saying we like to use a lot around MKC "You gotta work to win!"