Air Filter/s for Race Use

[1969race125]

Apologies if this has been asked before - I searched but couldn't find it mentioned.

I'm wondering what air filter set-up you would recommend for a 2L 8V race engine running 45 Delortos. I'm currently running with no filtration, which I am comfortable with for short races on our local track (Manfeild, New Zealand). However I'm concerned about running longer endurance races with the track getting dirtier and dirtier. I'm also planning to run at the newly-extended Taupo track which is currently notrious for dust and building rubble etc. from the extension works.

We have tried running with individual sock filters, and with a pair of K&N oval filters but they seem to strangle the engine above about 5500 rpm.

The next step up from those is expensive, so I'd rather make an educated choice based on others' experience, if possible.

I've included pictures of the engine bay and the dyno graph (without filters) if they help. I'm getting 149bhp at the rear wheels at 5690rpm.

Thanks!

[Guy Croft]

That's good power, well done, and of course, yes - way too much airflow for socks. They're only good for about 30bhp per cylinder.

In this case I recommend foam - ITG, and FWIW GCRE will hopefully be soon appointed as a distributor for them. I have known the owner Jonathan Douglas for a long time, very clever man. There is a case history in the GCRE manual about one of his GC engines.

There is foam and foam (!) but this firm does really invest in technology for filtration.

GC

[Julian]

I have to concurr on that one - we've been using ITG for quite a while too and have an excellent relationship with them. Their products are consistently excellent in terms of both filtration and performance.

[Testament]

What about making an airbox around the trumpets and using a large single panel or pod filter?

[Julian]

Looking at how close the trumpets are to the wing and suspension I think a simple airbox would be a real headache. The only real option that I can see is to use trumpet socks - the big question though is why the socks tried already were that restrictive above 5.5k rpm.

[SteveNZ]

Does that dynopac measure power at the wheels or the hubs? Ive had my car dynoed at chequered flag and always thought they had a hub dyno.

Sorry, I can't offer a suggestion for the filters. Although, I think Testament's suggestion is good.

[Guy Croft]

yes sorry, airbox sealed and ducted would be great, filter inside or remoted turbo style. I just dived on 'air filter' without thinking.

GC

[Yugo_Turbo]

Fiberglass could be solution for airbox.
You could build airbox of this material exactly the size which will fit in this tight place around wing.

I'll try to find a picture od airbox on Peugeot 2.0 16v SuperProdaction class...very intereting set-up...

[Yugo_Turbo]

Couldn't find Pug's here is one from BMW...just to give you idea:


Or something like this one:


These could be build of fiberglass too.

Hope I helped a little.

[1969race125]

That's really, really useful - thanks everyone for your suggestions. I think enclosing the airbox will be feasible. I assume you would still recommend ITG for the remote filter?

Steve - yes that is at the rear hubs. Is there a big difference between bhp at hubs and at wheels?

Thanks again everyone!

[SteveNZ]

Steve - yes that is at the rear hubs. Is there a big difference between bhp at hubs and at wheels?

There is some difference. However it takes the tyres out of the picture which is good as they can be a big variation. Even wheel balance and alignment can make a difference.

e.g check this dyno plot. This was from my friends car. Note the drop at about 5000rpm. some may think its a tuning fault but I was watching at the time and notice one of the wheels was way out of balance. It would have probably make another 5kw or so with a balanced wheel.

[petert]

I'm not very confident with glass or carbon fibre, so I built an air box from 0.5mm stainless sheet. Stainless, unlike other metals, is a poor conductor of heat, thus making it a suitable material.

[sumplug]

Seeing that the trumpets are virtually touching the inner wing, wouldn't the use of downdraft carbs be the answer here? Even fitting remote filters will be a struggle.

Andy.

[1969race125]

The photo might be a bit deceiving on clearance - there's enough room to fit socks on all trumpets without the socks touching the wing. While the bottom of the airbox will need to be contoured to fit the shape, enclosing the whole space should not be too difficult. I might run something up quickly out of thin alloy just to see if it will work. Will let you know how I get on.

[SirYun]

you can make a blank from foam (if you are in surf country visit your local boardsmith see if you can get leftover foam) in a way will fit the weird space you have. a belt sander is a quick way to shape the foam.

you can use 3M spraymount to get the first layer to stay put during the layup

then lay it up with fibreglass/ carbon/whatever fit to budget, sand it and then pour acetone (fumes !!outside!!) via a cut hole to dissolve the foam.

here is a webpage that pretty much explains the technique

http://www.mci.i12.com/carbon/lost_foam.htm

you can make up a baseplate which has the trumpets fitted. Are rampipes that are a bit shorter an option ? I'm not very familiar with webers and i'm not shure if changing the rampipe would upset the metering due to the reduction of the main jet signal strenght.

i find it a bit odd that weber rampipes do not have a rollback, adding a 1/4 radius to the edge should add about 6% flow

As a rule you need at least the diameter of the intake of space between the pipe and the wall.

hope this helps

thank you,
Joost