KN Filters

[dmode]

As I used to drive Triumph straight six engined cars, I do miss a little engine noise The Twin Cam in my Elan+2S is ever so silent. The car is running on Dellorto`s, and I am considering fitting it with KN airfilters mainly to gain a little bit more induction noise. I plan to keep the tube, that directs the air from the front, but I will remove the original airbox. However I am having second thoughts because I suspect, that I will actually loose bhp`s with KN`s?? What is your experience regarding this matter?

[terryp]

Claus
Have a look at this
elan-f15/cliveyboy-breather-and-filter-conversion-t17520.html
and look on Cliveyboys site

I don't think you lose with K&Ns unless I'm missing something?

Terry

[dmode]

Thank you Terry, but I would really like an increase in the noise too So I would prefer the KN`s directly at the carbs. How ever it gets pretty hot in the tiny engine bay of an Elan, and carbs need cold air to perform at their best, which is probably why Lotus fiitted the airbox with ducting in the first place?

[terryp]

I had that arrangement on my last car, and yes it sounded great and I had no problems.
BUT (!!) there are a number of posts regarding a fire issue so when I bought the new car I went for Cliveyboys , not as noisey at lower RPM but a great sound above 4500rpm
With the filers directly on the carbs there is also an issue with the breather and the throttle cable where a bracket has to be fabricated. I used a cut down back from the air box with gaskets both sides.

Terry

[davidj]

Hi,

I can assure you that K&N's make the correct noise. My sylva, with Webers, makes a right din, more so than the exhaust!

Also, you should get a slight increase in power as they flow more air than a normal airfilter. However, you need to increase the jet size to gain the power, otherwise you will be running weak. Fitting K&N's on two stroke motorbikes with no mods can result in melting the pistons! The existing filter design does result in cold air to the carbs, but I have heard the inlet manifold is restrictive, particularly for the rear carb.

David

[Carlos A]

I bought a K&N RE-0920 Universal Rubber Filter, a 3-1/2" dia. hose, and a piece of aluminum to make a bracket. The filter I bought it is a bit bigger than Clive's. The results are really good, more power... but yes... you need to adjust the carbs.

Best regards,

Carlos

[alaric]

Hi. I bought the Cliveboy K&N set up to be mounted in the nose. Does anyone know how the carbs need to be adjusted? It's a pretty simple swap of the original airbox and the K&N one but I wasn't expecting it to make a huge difference to the carburation.

All the best.

Sean.

[terryp]

Sean
I think it slightly leans the mixture out but in a positive way. I didn't change any jets and after adjustment with 2 colour tunes and a manometer it passed the French post 1972 emissions test , which is quite strict. CO2 at below 4 I think. When I pull the plugs , all look fine. The car runs without spitting through the carbs.
I do run on Castrol lead additive with octane boost (If you beleive that)

All the best
Terry
It sounds as if you car is getting there!!!!!!!!!!!!!!!!!!

[rgh0]

I am not sure why you would need to rejet the carbs with a change of airfilter. The weber jet chamber is balanced via a hole in the front of the carbs with the air pressure the carbs see. A less restrcitive filter should make no difference.

The pressure drop of the original filter when clean is also so low as to make no difference in terms of engine output whether it is there or you just use an open pipe so in practice a K&N filter on the end of the pipe will make no difference in output.

Changing to filters directly mounted on the carbs will give a nice increase in induction roar if your like that sort of thing. Provided they themselves are non restrictive you get a small increase in hp versus the orginal air box as it restricts flow to the rear cylinders. I measured 1 to 2 hp change when removing the air box on the dyno. You need to leave the hole open where the duct from the original air cleaner was so that cold air flows to the carbs bypassing the radiator.

If you use pancake style filters you need to esnure enough clearance between the end of the trunpets and the outer cover of the pancake otherwise you will restrcit air flow . You need at least the diameter of the carbs barrel from the end of the trumpet clear if possible - most pancake filters are to thin. Most racers use sock style filters over each trumpet.

You need to ensure the filters you use are made of non flammable foam or other filter material and use a non flammable tactifying oil ( I beleive K+N's are Ok in this regard)

regards
Rohan

[dmode]

Thank you very much Rohan, that was just the sort of advice, I was looking for

[terryp]

Claus
My old car with back plate and K&Ns with small trumpets inside as Rohan's post above

[Spyder fan]

Just a quick tip, make sure you check that the trumpet length suits the amount of space in the K&N's. I did a swap in my +2 LTC and got a lovely amount of induction noise mainly down to the fact that the trumpets were nearly touching the cover plates, this seemed to strangle the carbs somewhat. Fitted the next length down and they worked really well for noise and a perceived performance increase, but maybe it was just that lovely induction roar.

[Spyder fan]

And of course I read all the previous posts in the thread before I sent that didn't I!

[bengalcharlie]

Rohan

I have a stromberg euro spec head and currently run the original airbox with a KN filter in the nose. Does your theory also apply to the stromberg head?? Would I gain power by switching to trumpets ( the stromberg does not have trumpets fitted) with socks? secondly where could I buy such a set? preference would be in the US or nz/Australia.
Cheers
Robin

PS for a while I drove the car with the KN filter directly mounted to my airbox and I loved the induction roar but I switched back because the filter would hit the bonnet.

[collins_dan]

I have strombergs, bought some trumpets (I think http://www.rdent.com/) and a pipercross filter with backplate specifically for the strombergs. (http://www.pipercross.net/competition/p ... _px500.asp) Looks, sounds, feels great. The pipercross link includes the height of the dome, so you can figure out what size trumpets to get. I previously had fitted a K&N filter on the front of the original box and it just fit in the space next to the radiator, so eliminated the tubing to the front, but it feels more responsive with pipercross set up.

Dan '70 S4 SE Federal