Outer Limits 4x4 Board

I have a 3.5l V8 in a 2wd off road buggy.
its a race motor built to run to 7000 rpm.
Currently running twin SU carbys.
Im planning to spend over a week running it around in dusty red sand mallee conditions.

The filers are mounted out in the fresh air/wet mud/sun/dust/rain/dew etc (no bonnet)

Im leaning toward running a pair of large pod style filters (the better ones of these supposedly handle moisture no worries)


Im wondering if you can recommend as a great high performance air filter.
Pls mention brands and suppliers.

Thanks.


ps - I also have the option of a huge ex truck cyclonic filter with 3 inch plumbing - but I dont think this will get the air flow I need.

Sounds like you're doin' the Mallee Rally?


If you're gunna run pods, then make sure you clean them AT LEAST every day out there. And check your intakes for dust ingress while you're at it each day. Personally, I'd have the spare cyclonic number on hand as a back up in case you find dust getting through. Better to have a bit less performance than a shagged motor.


$0.02

If space isn't an issue, get the biggest truck/excavator filter housing you can find and fit a donaldson filter (they should all have an integral cyclonic pre-cleaner). These filters are made for the dustiest conditions, and if you fit a large enough one you should have a similar pressure drop to a pod filter.

Off-road filters run 2 elements - an outer/main element and an inner/safety element. If you prefer performance to air cleaning ability, then don't use the inner element (or use it in non-competitive sections?). Just the main element will filter MUCH better than any pod-type filter.

I know the good pod filters will flow HEAPS of air (I was told one of the large ones can flow 600hp worth)

but how does this compare to a truck style filter.

has anyone got some dyno experience comparing these filters ??


ps - There is no non-competitive sections !! Its 6 buggies away for a week of almost non stop driving !!

BrettInUte wrote:I know the good pod filters will flow HEAPS of air (I was told one of the large ones can flow 600hp worth)

but how does this compare to a truck style filter.

has anyone got some dyno experience comparing these filters ??


ps - There is no non-competitive sections !! Its 6 buggies away for a week of almost non stop driving !!

HP doesn't really come into filter selection. Flow rate and pressure drop are what is important.

Your 3.5L engine - assuming a volumetric efficiency of 80% at 7000rpm (probably MUCH lower) - would flow around 940m3/min (34600cfm) at redline. That would be an equivalent flow to a 5-6L turbodiesel that redlines at 2500rpm (since it will have a much higher VE). So if you get a filter and housing for an application like that it would be fine.

Pod filters (usually) have much lower pressure drop (restriction) than fibrous elements (surface area for surface area) - that's why they have less resistance and "flow" more air (but only filter out rocks). But if you go large enough with a fibrous (cellulose/paper) filter you can get one with the same pressure drop, so shouldn't make any difference on the dyno.

A filter company I worked with designed and manufactured a fibrous filter for some F1 engines after they found the K&N filters were letting in too much crap and killing the engines. They managed to design a filter that had almost as low pressure drop (flowed air as well) - even with the VERY strict size and weight limits they had to deal with. An F1 engine flows twice as much air as you need to deal with - and the filter size restrictions meant the air velocity through the filter was about 5-10 times what you would have. The slight increase in DP didn't make a difference on the dyno - and the engines managed to last a whole race with the new filters - which was a bonus .

BrettInUte wrote:I know the good pod filters will flow HEAPS of air (I was told one of the large ones can flow 600hp worth)

but how does this compare to a truck style filter.

has anyone got some dyno experience comparing these filters ??

I don't think many people would have compared a large donaldson set up properly to a pod, they solve a different problem for most people, but in a buggy, you should be able to work around the packaging issues.

BrettInUte wrote: ps - There is no non-competitive sections !! Its 6 buggies away for a week of almost non stop driving !!

All the more reason to run a very good airfilter, even if you loose a little bit of HP (which you shoudl be able to avoid with correct element selection and piping)- To finish first, first you have to finish. I don't believe a pod filter will filter effectivlely over this duration, and if they are exposed to mud/water they will pass it through. (from experience)

Steve.
Steve.

Go the Donaldson. Unless you enjoy oiling up air cleaners it is the only way to go.
A friend of mine a few years ago dyno'd a class 6 buggy trying to squeeze every bit of an advantage out of his motor. He had two filter setups being a small Donaldson with small pipework going into a small air box. And the other being a K&N with a foam prefilter.
Their was a small amount of difference in the horse power, but I would not think that it was the doing of the filter but more the pipework choking it.
Just make sure that you think out the pipework right , this includes trying to duct cold air from in front of the radiator into it rather than hot air.
Good luck racing.

Thanks for the info guys.
Thats just what I was looking for.

The donaldson I have came off a huge V8 diesel truck.
So it might well have enough flow.

I know how to make intake plumbing really flow. Just make it bigger than it needs to be - and try to remove all the bends. I was told (and shown) each 90 degree bend loses about 3% power.

Looks like I might use the big donaldson (think 10L bucket size).
I will have to do some serious work to connect it to twin SUs - but sounds like the way to go.


Thanks guys.

I've got a Donaldson hooked up to twin SU's on a Rover V8. Its a great filter but the hardest part is keeping the inlet ducting sealed, mostly at each end of the dodgy cast alloy elbows which connect to each SU. When you put your hand over the inlet to the air cleaner barrel and the engine doesnt stall, theres a problem.......

If its really dusty, I'd use a precleaner bowl as well. Any hp you lose with a good dust filtration set up is going to offset what you lose forever in lost compression from a dusted engine.

tripple SU's starved my torana with a 202 ...

was a race car...

dunno how u manage to feed a porformance 253..

the 202 was good for 7800 befor it was a bit clappy tho

Mark2 - I was planning to get it 100% sealed. Kinda defeats the purpose if it doesnt. Duct tape is great for emergency sealing...

Mousie - I dont really get what you are saying...

mate i run a k and n as mush as i hate them! I fitted fuel safe filter foam over mine about 1/2" thick ans soaked filter oil over it. works sweet and captured all the dust well before it got a chance to get near the n and n dust funnel

cheers bru

finner filters are an excellent choice

I run Unifilters / Finer Filters on my truck. I use a pre filter over the top of my filter which is easily removed cleaned and oiled.

LudaCris