RazMan
|
| posted on 26/11/10 at 12:13 AM |
|
|
Air filter design for trumpets
Is there any design spec I should be working to when it comes to making my own air filters for my V6?
As I understand it, I can probably put a baseplate practically anywhere but how much clearance should I have from the end of the trumpets so as not to
affect the airflow?
As always any tips will be appreciated.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
|
|
LBMEFM
|
| posted on 26/11/10 at 05:48 AM |
|
|
How about s foam sock over the end of each trumpet
|
|
|
MikeCapon
|
| posted on 26/11/10 at 08:30 AM |
|
|
Making airboxes the rule was a minimum of 1.5 X choke size. I suspect that with a filter you can go to a good bit less as the filter opposite the
trumpet will be flowing air as opposed to the airbox where all the air has to pass between the trumpet and the airbow wall.
If you've got room for 1.5 X choke then you are sure to be OK.
HTH
Cheers,
Mike
|
|
|
RazMan
|
| posted on 26/11/10 at 08:54 AM |
|
|
My trumpets are a bit unique as they are 'siamesed' on a twin port V6, so any filter will have to be quite a strange shape.
Image deleted by owner
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
MikeCapon
|
| posted on 26/11/10 at 09:00 AM |
|
|
Good grief you're going to have some fun making those trumpets. Have you not considered offsetting the pairs in a V to enable using a full
trumpet on each port? Could be easier and probably better for flow?
|
|
|
RazMan
|
| posted on 26/11/10 at 09:09 AM |
|
|
They're already made - here's a pic of the finished version. The siamesed design was unavoidable due to the positioning of the ports and
length of the trumpets (they would otherwise have to be very short)
 
Components
They are on their way from Thailand as we speak ... er type  and are made in a 'layer cake' construction so a baseplate can be sandwiched
between two layers (three in the trumpet part)
So I am thinking of having a foam filter on each bank something like this ..
[Edited on 26-11-10 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
mcerd1
|
| posted on 26/11/10 at 10:35 AM |
|
|
Looks like your on the right track to me, I've always been told that trumpet socks arn't that good anyway... (too close to the tumpets I
guess)
1.5x the choke sounds like over kill for a foam filter to me, I was going to leave about 1" on mine from the end of the trumpet to the inside of
the filter - someone tell me if this isn't enough !
Piper say 19mm min on there site....
I went for an ITG one for mine (had a lot of recommendations) and they come in more sizes than the piper ones too:
http://www.merlinmotorsport.com/Technical/pdfs/itgmf1.pdf
[Edited on 26/11/2010 by mcerd1]
-
|
|
|
RazMan
|
| posted on 26/11/10 at 01:19 PM |
|
|
Just had a (possibly silly) thought - what if I was to sandwich some fine mesh between the layers? I realise it wouldn't be as effective as a
'proper' air filter but it might stop anything falling into the inlets.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
RazMan
|
| posted on 2/12/10 at 12:13 AM |
|
|
Just had another silly thought - I have my moments 
Is there any way that a sort of 'trumpet plug' could be incorporated? I mean something like a cone shaped foam filter which partially fills
the trumpet and is retained by some coarse mesh in some way.
Image deleted by owner
The reason I ask is that space above the trumpets is going to be very tight and any filter which is mounted on top of the trumpets (like the socks)
might give me clearance issues and I would rather not take a cutting wheel to my bodywork unless I really have to.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
rick q
|
| posted on 2/12/10 at 03:42 AM |
|
|
I made my own filter box and filter using scrap aluminium and filter foam from a local supplier.
Flat panel filters appear to be designed for a face velocity of around 1.75 metres per second. Work out how much air you car will draw in at full
revs in cubic metres per second and divide it by 1.75 - that'll give you the filter area you need. [There's 1000litres in a cubic metre,
by the way]
The foam I found is the same as that used in Unifilters, which is similar to the ITG's you have over there. The foam is restrained along two
sides by aluminium angles and is supported across the width of the filter by threaded rods [about 100mm apart] The whole thing was cheap as chips,
including the $Aus10.00 piece of foam.
Looks like this [crappy phone photo] :- 
and this with the filter in place :- 
Don't put anything near the trumpets. Even fine mesh will only be about 85% openings [the rest is the wire] and it will severely restrict
airflow, and create turbulence.
|
|
|
MikeRJ
|
| posted on 2/12/10 at 08:31 AM |
|
|
quote:
Originally posted by RazMan
Just had another silly thought - I have my moments
Is there any way that a sort of 'trumpet plug' could be incorporated? I mean something like a cone shaped foam filter which partially
fills the trumpet and is retained by some coarse mesh in some way.
No, it would be hugely restrictive, even if it was just some coarse wire mesh (which wouldn't do any useful filtering anyway).
Even filter socks can be significantly restrictive simply because they offer such a small surface area of filter material per choke.
With a sausage type filter (Pipercross etc.) you can get the trumpets surprisingly close to the filter before it starts to significantly affect
airflow since the majority of the airflow comes from the sides into the intake (which is why a flared trumpet improved airflow so much); Pipercross
themselves recommend no less than 19mm, and my friends Mi16 engined tarmac rally car is running about this much clearance and producing ~280bhp from a
2.0 normally aspirated engine.
I believe the 1.5 choke diameter rule is for solid airboxes/plenums where a very close surface to the inlet can cause problems with standing waves and
will be more restrictive than filter material anyway.
[Edited on 2/12/10 by MikeRJ]
|
|
|
RazMan
|
| posted on 13/12/10 at 11:53 PM |
|
|
Thanks for the ideas guys 
Space above my trumpets is very tight so I need to make a very low profile filter, but keep it unrestricted. So if I made a foam sandwich around / on
top of my trumpets like this ....
 
Description
.... would that work? The backplate would be just below the trumpet flares and there would be about 20mm of 'free air' above them, with a
foam 'roof'. In theory air should come in from all sides and the top (although very close to the bodywork)
A couple of questions - what is normally used to stiffen the foam, stopping it from collapsing into the trumpets? Is it a coarse mesh cage of some
sort? I assume the cage is secured to the backplate?
[Edited on 14-12-10 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
mcerd1
|
| posted on 14/12/10 at 08:33 AM |
|
|
looks ok to me (not that I'm an expert), maybe leave a bit more room round the sides if you ca get it....
but isn't that just the same as a couple of low profile versions of these:
(they do very shallow versions
[Edited on 14/12/2010 by mcerd1]
[Edited on 14/12/2010 by mcerd1]
[Edited on 14/12/2010 by mcerd1]
-
|
|
|
radom
|
| posted on 14/12/10 at 10:51 AM |
|
|
that's how I did it
i glued the foam on the edges and it works ok, foam is stiff enough and doesnt collapse
|
|
|
coyoteboy
|
| posted on 14/12/10 at 11:16 AM |
|
|
For limited milage I'd be fairly happy running without a filter at all, I did it for ~4 years on a daily driver (not a performance car!) and saw
no change in compression/performance in that time. I'm slightly more cagey with my turbo but still considering it despite it being against
conventional wisdom!
|
|
|
RazMan
|
| posted on 14/12/10 at 12:59 PM |
|
|
Radom - That's a neat job but I notice you havent left any free space in front of the trumpets. Consensus suggests that at least 20mm is needed
to prevent any power loss. Definitely a Locost solution though
coyoteboy - I did consider running without a filter until one day I picked out a 15mm dia pebble that was lodged in the fuel rail (my trumpets are
pointing skyward) I hate to think what damage would have been done if it went in one of the trumpets!  I have even considered tea strainers as a
temporary 'debris filter' until I sort out a proper filter.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
radom
|
| posted on 14/12/10 at 01:59 PM |
|
|
quote:
Originally posted by RazMan
Radom - That's a neat job but I notice you havent left any free space in front of the trumpets. Consensus suggests that at least 20mm is needed
to prevent any power loss. Definitely a Locost solution though
coyoteboy - I did consider running without a filter until one day I picked out a 15mm dia pebble that was lodged in the fuel rail (my trumpets are
pointing skyward) I hate to think what damage would have been done if it went in one of the trumpets! I have even considered tea strainers as a
temporary 'debris filter' until I sort out a proper filter.
yeah I know pipercross/itg suggests 20mm but I doubt if my foam takes any hp. It's really low-density foam, it doesnt do much of filtering but
just catching bigger objects 
although there would be no problem in using thicker layer of foam and leaving free space in front of the trumpets
|
|
|
mcerd1
|
| posted on 14/12/10 at 02:25 PM |
|
|
RazMan - have you got the dimensions of your setup worked out ?
-
|
|
|
RazMan
|
| posted on 14/12/10 at 03:13 PM |
|
|
quote:
Originally posted by mcerd1
RazMan - have you got the dimensions of your setup worked out ?
Until this afternoon I thought I had everything sorted, but now that the bodywork is refitted there is almost no clearance between trumpets and body
It now looks like another plan is in order ....
Plan B would be to reduce the length of the trumpets by about 30mm by removing a layer of the assembly. I am not sure how this will affect the torque
until I can get to a dyno.
 
Description
 
Description
Plan C - 12 tea strainers ........ no really, I'm serious I might be able to squeeze a 60mm tea strainer over each trumpet with a bit
of creative cutting & shutting to get the right shape but you get the idea...
 
Description
Plan D, I could sandwich some mesh under the flared section of the trumpet 'layer cake' (see my 3rd post). Hmmm I am not sure which would be
the better option as far as airflow is concerned. I realise that filtration will not be very good but at least it should stop any debris doing
serious damage.
[Edited on 14-12-10 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
mcerd1
|
| posted on 14/12/10 at 04:10 PM |
|
|
so your going for the cossie DFV look then
I take it plan E (cut a hole in the bodywork) isn't an option on your car them....
[Edited on 14/12/2010 by mcerd1]
-
|
|
|
RazMan
|
| posted on 14/12/10 at 04:52 PM |
|
|
quote:
Originally posted by mcerd1
I take it plan E (cut a hole in the bodywork) isn't an option on your car them....
Sadly not yet - I was hoping to radically modify the body over the winter but finances dictate otherwise
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
rick q
|
| posted on 15/12/10 at 03:48 AM |
|
|
Trumpets work by letting the air flow in from all sides around the radius at the mouth and then into the tubular part. Ideally, the air accelerates
gradually and smoothly from stationary [away from the trumpet] to the maximum at the throttle blade.
While the tea strainer idea is pretty natty, it defeats the purpose of the trumpet lip - if you have to go that way [with mesh], do it like the cossie
above.
Do the sums on the free area of the mesh too [that's the actual area of the holes compared to the total area of the mesh] - in many cases it can
be down to 50% i.e. for a square inch of mesh, you only get half a square inch of holes for the air to flow through.
The trick is to keep the velocity through the mesh as low as possible ..... as the resistance to airflow is proportional to the velocity squared.
More resistance = less power.
|
|
|
RazMan
|
| posted on 15/12/10 at 08:52 AM |
|
|
You are absolutely right there Rick so the tea strainers are in the bin now
I'm just weighing up the pros and cons of going for either ....
- longer trumpets with Cossie style mesh
- shorter trumpets with proper foam filter
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
mcerd1
|
| posted on 15/12/10 at 11:12 AM |
|
|
how much time can you afford to play around with it on the rollers....
-
|
|
|
coyoteboy
|
| posted on 15/12/10 at 04:23 PM |
|
|
quote:
coyoteboy - I did consider running without a filter until one day I picked out a 15mm dia pebble that was lodged in the fuel rail (my trumpets
are pointing skyward) I hate to think what damage would have been done if it went in one of the trumpets! I have even considered tea strainers as a
temporary 'debris filter' until I sort out a proper filter.
Hmm if your trumpets are exposted to the world rather than in a bay of some sort I too would be more cautious
|
|
|
