Please help me understand air cleaner sizing

[C Lee Farquar]

I have a Chevy LS7 in an off road racer and have been running with a Green cotton filter. This is letting too much dust through so I've been looking at alternatives.

I like the Donaldson Powercore filters



The problem I'm struggling with is that from what I can tell the engine needs a little over 700 CFM of flow and to achieve this I need a filter unit the size of a suitcase. Whereas a Powercore filter fitted to the Covette Z06 is quite modest in size. Am I missing something fundamental?

This is the air cleaners I'm looking at Donaldson PSB

[stevieturbo]

Depends how that CFM rating is measured I guess.

If you take a look at OEM paper filters fitted to most cars, they really arent that big, yet often can easily support 2-300hp without any real restriction.

I'm sure the OEM Vette one as you say isnt huge either, and they will have built in some reserve for when it's dirty

You could look at some large diesel engine airboxes and filters. But really, just fit the biggest one you can, that way you're covered. But very little will filter as good as an OEM type paper filter.

[anonymous-user]

For your application i'd be looking to fit the biggest filter box and element from some big engined "off highway" application. Say like from one of these:




High filtration (because they run for a lot of hrs in poor environment) and low restriction.


More seriously, you should be able to buy a filter unit from a commercial vehicle that takes readily available panel filters. Assuming you have the space, then the bigger the better!

[anonymous-user]

Donaldson said:

ideal for equipment operating in medium to heavy dust environments

A filtration system from a passenger car will not be rated to anything like that std, and will loose a lot more performance (much higher pressure drop) as it clogs. That is why the off highway units are so large, so even when clogged they still continue to filter without excessive loss. They also tend to be fitted to vehicles that cost hundreds of thousands of dollars, and which have a heavy utilisation and so are "worth" protecting more (compared to the average passenger car, that never sees poor conditions and needs to be cheaply serviced)

[C Lee Farquar]

Thanks both.

My thinking is to go with the largest I can package and fit a service indicator.

[Evoluzione]

Don't rule out the possibility of using two OE air boxes, I used this on a cheap build as it was cost effective, easy and fitted. I reckoned that because we'd doubled the power we simply doubled the amount of air filters. This gave me the chance to put them where I needed and simply joined them with a Y piece.

[C Lee Farquar]

This gives an idea of what I'm up against Walters Arena

[stevieturbo]

I'd go to a local tractor type supply shop and see what they have available. They might even have catalogues with complete air boxes.
Or maybe even a marine supplies place for big boat engines. Although they're probably in a cleaner environment than plant machinery

I assume there is no reason you couldnt mount the filter casing just behind the roof ? Or must it be inside ? Say with a rear facing intake, so no water would ever splash into it ?

Or go onto some of the big diesel forums in the US, see what they're using for filters for their huge diesel engines they use for drag racing.
They make silly amounts of power, and always with huge airflow.

[Pumaracing]

Everything you need to know here:

https://web.archive.org/web/20110918115057/http://...

[anonymous-user]

C Lee Farquar said:

Thanks both.

My thinking is to go with the largest I can package and fit a service indicator.

Ideally, you want a differential pressure sensor across the element, logged into your ems.

However, by simply logging your EMS you just look at the MAP value recorded during WOT running at various engine speeds. By looking at the MAP value before start you can correct that data for daily Baro changes.

[blitzracing]

Have a look at cyclonic filters- so you get most of the dust out before it hits the filter. Ive seen such units on dumper trucks.

[PhillipM]

We had the same issues with the cotton filters Steve, we went back to normal paper filters and didn't have an issue after - with your scoop being on the roof the same they shouldn't suffer from water making them fail, we just bought a big stack and swapped them every event. The good ones got vac'd out and re-used.

[C Lee Farquar]

Thank you all. I'll fit the largest I can with a precleaner.