Foam Sock filters cost me 55bhp

[reggid]

so i installed an ITB system with runners and put a cheap set of oiled foam sock filters on as a temporary means to get the engine running before an airbox is made.

doing nothing more than putting socks on caused 25-30% power loss compared to open runners. the power peaked very early and plateau classical sign of a restriction.

the difference was staggering

my question is does over oiling worsen the problem, i used the oil the dirt bike guys use and followed their recommended application procedure?
do cheap filters use poorer flowing elements would something from ITG be likely any better?
or are socks filters just rubbish all together and to be avoided like the plague?

i used these

http://ramair-filters.co.uk/cs-carb-socks/twin-car...

[PeterBurgess]

We tend to find the slipover style very restrictive for power delivery, the filters tend to ride down the trumpets and end up with foam directly in the trumpet opening. Overoiling makes the power loss much worse. Experimentally we established foam air filter element needed to be 2.5 times the area of paper or cotton gauze to flow the same. This was on Chieftan tank donkey engines. We had to mess about with 'proper' dust ( from Arizona desert or some place where 'standard' dust can be obtained!)for the flow testing.

As a ballpark figure we see 8-10% bhp losses with undersized filters. Overoiled can be very very high. Our full race MGB engines make less power even with gauze filters as we cannot get one choke per port scenario and cannot feed enough air through filters even though we hate running on unfiltered air!

Peter

[reggid]

thanks is there a better brand? what oil do you recommend? i have cleaned a lot of oil out and it is better but still not the same by a noticeable amount.

[PeterBurgess]

Unless you are convinced your engine will run in dusty conditions I would consider running clean filters only. The moment you add oil you will restrict airflow and, if the airflow capability is at or even below the required amount before adding oil, power will be lost. May be best just to keep big bits out of the inlet system?

We have been monitoring internal wear on Race B engines for almost 30 years. Running on unfiltered air (last 10 years) has shown no extra wear over filtered engines. We run engines for around 30 race hours before rebuild, when we hone and re ring and replace bearings plus any other wear such as cam etc. The only ingress of something nasty was a screw detached from a weber spindle and left telltale 'thread' marks on the piston crown and headface.

Peter

[Sardonicus]

Sock filters have been a no goer for as long as I can remember (early eighties) always presumed that info was set in stone quite frankly however I have loved any engine that I have built enough to always have some air filtration rather than open bell mouths

[PeterBurgess]

The trouble is, we don't want to sacrifice the hard earned bhp and torque on the race track

With the MGB setup most people use, one has to either dress the inner wing to give clearance to the trumpets or machine the inlet manifold at 5 degrees from the vertical to create clearance.

Difference between fun and race?

Have you worn an engine out running it unfiltered?

Peter

[stevieturbo]

The bottom line is....just how tight for space actually are you ?

Are you forced into running small filters, and placed tight over the actual air inlet ?

[PeterBurgess]

I presume he has plenty of room as he talks of using foam until he makes air box.

If you are asking me? We aren't allowed airboxes in FIA spec.

Peter

[stevieturbo]

PeterBurgess said:

I presume he has plenty of room as he talks of using foam until he makes air box.

If you are asking me? We aren't allowed airboxes in FIA spec.

Peter

Was asking the OP.

IMO any form of trumpet socks are always a last resort, especially ones that sit close to the actual air inlet/bellmouth inside the filter.

[stevieturbo]

PeterBurgess said:

I presume he has plenty of room as he talks of using foam until he makes air box.

If you are asking me? We aren't allowed airboxes in FIA spec.

Peter

Was asking the OP.

IMO any form of trumpet socks are always a last resort, especially ones that sit close to the actual air inlet/bellmouth inside the filter.

[reggid]

im doing runner length testing so wanted a way to be able to add a simple filter. once i know the length and taper etc i will make a plenum to suit. its not possible for me have a plenum and adjustable length runners space is at a premium.

i have cleaned them about 4 times to try get rid of the oil and most is gone and it is definitely better but will try kerosene to get the last bit out.

[packman10_4]

Years ago i use to have a RS 2000 with a pinto in there. Its was running 168 hp with the aid of big valve
head and a gp1 cam and a brace of 48 dellorto carbs. I had 90mm trumpets on there , with the filter socks
on it gave 112 hp at the wheels and wouldn't rev and 137 hp at the wheels without them and 6700rpm... and
that was with the ends braced with gauze so it didn't suck them in ....

[PeterBurgess]

Did you try without the gauze? we tend to find that is restrictive to flow too, has a detrimental effect way above the area of the mesh. 18 bhp on V8 MGB with mesh on carbs ( about 4x4mm gaps in mesh)made 200 whp without the mesh and 182 with mesh

Peter

[Kokkolanpoika]

When i choose my filters.. I contact my local Jenvey dealer where i bought my ITB setup.. He recon 1 big air filters, or some kind plenum setup.. Those foam socks will eat your horse power up to 70hp.. They have got dynamometer and some race opel omega 4000 (stroked from 3000) give +60hp more with ITG air filters than socks..

You have to use this type filters.. 4-1type
http://ramair-filters.co.uk/rt-carb-filters/caterh...

And Our Jenvey dealer recon that at least 50mm clearance between air horn and filter roof..

I dynotuned my RV8 with filters, didin´t realise to take them off..

[reggid]

well only kerosene was able to get the oil out completely, the air filter cleaner and K&N stuff only did half the job

seat of the pants says its much much better when dry and as good as it is going to get. next time im at the rolling road testing i will retest with and without the filter i expect maybe 5-10% loss

[PeterBurgess]

If your RV8 had the original K&N air filter it should have been ok and not lost power.
Many years ago Rover borrowed, for evaluation, an injected MGB Roadster belonging to Rog Parker (now MGOC technical expert. Rog and I had worked hard on the conversion it had modded heads and K&N filter and lots of work to get the plenum to fit cleanly under the standard bonnet line. Rover liked it so much they even copied the air filter arrangement, sadly they didnt want modded heads as they thought the chassis wouldn't take it

Peter

[VinceFox]

I've never oiled any performance filter i've cleaned on any vehicle i've run. For normal road/tarmac track use i've always thought of that as overkill tbh.

[Steve_D]

Side question.
Do foam filters clean up if you put them in the washing machine.
Pop them in with your work overalls and jeans...job done.

Steve

[Mr2Mike]

VinceFox said:

I've never oiled any performance filter i've cleaned on any vehicle i've run. For normal road/tarmac track use i've always thought of that as overkill tbh.

The filtering ability of a foam or cotton gauze filter used without oil is hugely reduced. The OP's problem is not the oil, it's simply that sock filters are inherently crap and should be avoided at all costs.

[reggid]

well ran the dry foam socks up and result was 8rwkw loss with filters vs without which is better than 33rwkw with the oiled ones.....