Bolt-on Engine Air Filters

Post by **millerman** » Mon Jul 28, 2008 11:49 pm

Advice needed on the best bolt -on air filter to go on a 1275 marina engine.

Is this a good buy http://www.demon-tweeks.co.uk/products/ ... e=P/CC1501
or the equivalent K&N or this one http://cgi.ebay.co.uk/Mini-Performance- ... .m14.l1318

I don't want a lot of induction roar, hopefully better performance but it will tidy up the engine bay and, it would seem, easy to put on

Thanks

Post by **superchargedfool** » Tue Jul 29, 2008 9:32 am

any open element performance filter will make a certain amount of induction roar, so if you don't want to hear that I would stick with a standard marina or metro type, not as good looking but quieter.

Post by **bmcecosse** » Tue Jul 29, 2008 10:42 am

I fitted the second one - K&N 'copy' and it's fine - but indeed there is some induction noise (not quite as much as open carb) - and I didn't pay that amount for it either!

Post by **Stig** » Tue Jul 29, 2008 12:12 pm

A general guide for open element filters is that bigger ones are quieter than smaller ones. I can't really tell but those both look about the same size.

Post by **millerman** » Tue Jul 29, 2008 2:18 pm

BM have you got the link to your supplier?

Thanks

Post by **bmcecosse** » Tue Jul 29, 2008 2:48 pm

It was from a seller on ebay! Dunno if my past records will show it. I'll have a look.

linearaudio · Post by **linearaudio** » Tue Jul 29, 2008 6:56 pm

The Vizard book reckons that the MG Metro casing with an aftermarket element is good flowing, but QUIET! He also reckons you will get more air flow improvement by putting a "stub-stack" (mini bell mouth) on the existing set up than by bolting a fancy noisy filter on. Food fo thought?

Post by **bmcecosse** » Tue Jul 29, 2008 11:05 pm

Yes -well my carb is heavily modified at the air entry flange to form a radius there - to eliminate the 'Vena Contracta' - which is what a 'stub stack' does!

Post by **Kevin** » Wed Jul 30, 2008 9:41 am

I think you will find that the pancake style are quite a bit quieter than the cone style that have quite a bit of induction road this is the type I prefer
http://cgi.ebay.co.uk/K-N-pancake-air-f ... dZViewItem

Post by **bmcecosse** » Wed Jul 30, 2008 12:42 pm

Yes - but 'pancake' have terrible air-flow - they are much too close to the inlet flange of the carb.

linearaudio · Post by **linearaudio** » Wed Jul 30, 2008 7:35 pm

bmcecosse wrote:Yes -well my carb is heavily modified at the air entry flange to form a radius there - to eliminate the 'Vena Contracta' - which is what a 'stub stack' does!

I'm sure the girl up the road had vena contracta, I was told to keep away from her! Seriously though, your'e dead right about the pancake filter (put your hand near an open carb and feel the suction) yet people still rave over them I suppose because theyr'e big and chromy.

Post by **bmcecosse** » Wed Jul 30, 2008 7:50 pm

Well - the bigger the better!

Post by **Kevin** » Fri Aug 08, 2008 12:09 am

but 'pancake' have terrible air-flow - they are much too close to the inlet flange of the carb.

your'e dead right about the pancake filter (put your hand near an open carb and feel the suction) yet people still rave over them I suppose because theyr'e big and chromy.

I would agree if you mean the aftermarket ones from speedograph and the like but not the deeper K & N ones and to quote David Vizard, the air flow restriction is caused by the lid/cover of the filter being to close and it varies depending on the intake flare but his rule of thumb is no closer than the carb bore, so if a stub stack is fitted you will have ideal clearance of 1 1/2" if an 1 1/2" carb is fitted and so on after that it becomes beyond the sphere of influence.
One other point is that he doesn't mention

my carb is heavily modified at the air entry flange to form a radius there

doing that mod instead of using a stub stack.
So I will stick with the K&N pancack as there does not appear to be a disadvantage in using one.

Post by **bmcecosse** » Sat Aug 09, 2008 5:26 am

The Wizard DOES mention the mod to open end of carb - in fact he does it with some plasticine and lists the increase in flow. Fitting a stub stack is fine - but then the 'distance' to the filter cover MUST be that 'carb bore minimum' from the end of the stub stack!

Post by **Kevin** » Wed Aug 13, 2008 3:22 pm

The Wizard DOES mention the mod to open end of carb - in fact he does it with some plasticine and lists the increase in flow.

Well I thought that referred to a temporary stub stack as for height they are very shallow I will measure one tonight.

Post by **bmcecosse** » Wed Aug 13, 2008 4:20 pm

Yes - it did - but the effect is the same by radiusing the inlet - it is a BIG radius! It's a different thing if you want to increase the length of the inlet tract - for so-called 'torque' increase.

Post by **minor_hickup** » Wed Aug 13, 2008 6:32 pm

It works BMCEcosse, my brothers 2002 on twin solex sideraughts saw a noticeable difference in the power band on the dyno with 8.5" ram pipes moving it down the range, with minimal increase in torque, very useful for street driving.

Post by **bmcecosse** » Wed Aug 13, 2008 7:06 pm

Yes indeed it can - but some of that gain may be down to the radiused ram pipes. However tuned length inlet rams are well know to give benefit on highly modified engines - but doubtful value on a normal Minor engine. Fit a decent cam/head/carb/exhaust - and it's s different beast altogether!

Post by **minor_hickup** » Wed Aug 13, 2008 7:44 pm

Agreed, this is running a 292 degree cam on a very modified head, high CR and free flowing exhaust. However the pipes don't make any more power than the little ones solex supplied but they make the car more tractable.

Post by **bmcecosse** » Wed Aug 13, 2008 8:57 pm

It's finding an effective length that is the trick! If lucky - can maybe get them to 'work' at 2 or 3 different rev bands - the harmonics of the original rev band. 292 degree cam is not too hairy in a big motor. 1275 racing Minis run 300 cams - some use the 310 sprint and some the 320 super-sprint! generally these give more power at max revs, but lose more than they gain at lower revs. I can also say from personal experience that the 320 super sprint is a swine to start from cold!