Allen Brzeczek wrote: ↑Fri Mar 28, 2025 11:18 am
I suspect that my comment will be greeted with derision and disbelief by many but I for one, as with the majority of my past vehicles, have used unfiltered open bell mouths and ram pipes. However, after testing a race bike down a track on a farm where I once lived and picked up a small stone into the 2 stroke engine which caused significant damage to the piston crown and squish band in the cylinder head, I now use those with expanded gauze across the mouth to stop the entry of larger particles.
I had a similar experience albeit on my track prep'd 205GTi 1.9 running dcoe carbs, open mouth trumpets no filter and collected debris into cyl 1 causing an immediate stop and split liner, queue a £6k rebuild back then (12 years plus). The item ingested, it was a small nut that made a nice impact into the crown of the piston and jammed itself down the side and split the liner, the engine then hydro locked.
I know it sounds good especially at full chat but the damage to the pocket was extreme, I won't be dong that again (especially if I ever get my 1293 running)
Allen Brzeczek wrote: ↑Fri Mar 28, 2025 11:18 am
I suspect that my comment will be greeted with derision and disbelief by many but I for one, as with the majority of my past vehicles, have used unfiltered open bell mouths and ram pipes. However, after testing a race bike down a track on a farm where I once lived and picked up a small stone into the 2 stroke engine which caused significant damage to the piston crown and squish band in the cylinder head, I now use those with expanded gauze across the mouth to stop the entry of larger particles.
I had a similar experience albeit on my track prep'd 205GTi 1.9 running dcoe carbs, open mouth trumpets no filter and collected debris into cyl 1 causing an immediate stop and split liner, queue a £6k rebuild back then (12 years plus). The item ingested, it was a small nut that made a nice impact into the crown of the piston and jammed itself down the side and split the liner, the engine then hydro locked.
I know it sounds good especially at full chat but the damage to the pocket was extreme, I won't be dong that again (especially if I ever get my 1293 running)
have H4,s with open Ram Pipes on my late Brothers W/Replica.. i also worry about "Open Intakes ".. so to ease my worries i bought a pair of Socks that just slip on or take them off as & when.
Audiologist sold me a Pair of Expensive Hearing Aids.. but even without wearing them .. that H4 Intake Noise is just that bit too much after a few Miles on song .. so do take care of your own Hearing because once its has gone .. your H4,intakes are still just a bit too loud
Peter Laidler wrote: ↑Thu Mar 27, 2025 10:22 pm
I have said it many times on the forum that Unipart carried out a whole series of tests on the two most important components of all of the air filters offered by all of the UK suppliers. AIR FLOW AND FILTRATION properties. The best, throughout the tests by far away and ahead were the paper filters by COOPERS. As a result, the Unipart filters were Coopers.
As a little aside, the top filter box arrangement wasn't the best design for several reasons that I've mentioned before. But as for filtration and air flow, it's the Unipart/Coopers
I'm with Peter. The Coopers filters are fine. The problem is the airflow into the filters.Therefore the modified filter box as shown.
I did similar, but put the holes at the front with the vain hope it might keep some of the induction noise down (K&N) and push cooler air in from the front end
SMOKE GREY wrote: ↑Fri Mar 28, 2025 12:54 pm
Be interested if the Cooper gauze filters are original ones or the remade ones. I seem to recall Ian at OAP did a car and the dyno results between the cars original cooper mesh filters and a K&N was very minimal, which surprised a few people.
Your original Cooper Gauze filters on the 997 was as good as K&Ns on the dyno...and 4hp better than a airbox.
Minigman wrote: ↑Thu Mar 27, 2025 4:38 pm
,,,,Based on dual HS2s we managed 66bhp without the filters and 58bhp with. With that in mind I’m considering ditching the filters in favour of period looking ram pipes (with no filter socks as I’ve heard they’re quite damaging to power too).
For a road car, personally, I'd rather sacrifice the 8hp loss, than go unfiltered. It won't take too long to loose that 8HP and more, running unfiltered.
Fanfaniracing wrote: ↑Fri Mar 28, 2025 12:23 pm
It was all tested and written down by A-Series Guru David Vizzard in the yellow bible...
Dave Vizard explains how the K&N filters works.
"He's tested K&N filters against paper elements on a flow bench. K&N clean down to microns even when covered in dirt and they flow almost as well as having no filter installed."
The air filter info starts about 4 minutes into his video below:- https://www.youtube.com/watch?v=ow5cGV7bXCw
Peter Laidler wrote: ↑Thu Mar 27, 2025 10:22 pm
I have said it many times on the forum that Unipart carried out a whole series of tests on the two most important components of all of the air filters offered by all of the UK suppliers. AIR FLOW AND FILTRATION properties. The best, throughout the tests by far away and ahead were the paper filters by COOPERS. As a result, the Unipart filters were Coopers.
As a little aside, the top filter box arrangement wasn't the best design for several reasons that I've mentioned before. But as for filtration and air flow, it's the Unipart/Coopers
I'm with Peter. The Coopers filters are fine. The problem is the airflow into the filters.Therefore the modified filter box as shown.
I did similar, but put the holes at the front with the vain hope it might keep some of the induction noise down (K&N) and push cooler air in from the front end
Looks good. The reason I put the holes in the back was to reduce the amount of dust etc. blowing directly into the box due to the forward movement of the car. Also to pick up the heat from the manifold on cold mornings. Not sure if the former is realistic as dust and stuff is going to get blown about everywhere under the bonnet. Your solution probably is better because of the cooler air and the consequent higher air pressure. You've got me thinking again.
I'm with Peter. The Coopers filters are fine. The problem is the airflow into the filters.Therefore the modified filter box as shown.
I did similar, but put the holes at the front with the vain hope it might keep some of the induction noise down (K&N) and push cooler air in from the front end
Looks good. The reason I put the holes in the back was to reduce the amount of dust etc. blowing directly into the box due to the forward movement of the car. Also to pick up the heat from the manifold on cold mornings. Not sure if the former is realistic as dust and stuff is going to get blown about everywhere under the bonnet. Your solution probably is better because of the cooler air and the consequent higher air pressure. You've got me thinking again.
That is in our old rally car (hence the state of the engine after several years in a barn!) so it spent a lot of time high revs, low gears and lots of dust. The K&N's worked very well. I had an additional thought of either putting some trunking from the front to the back or as this is a Hornet making an airway under the bulge in the bonnet to get more air to the rear. One for the rebuild list
