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dvderlm

dergo air filters

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dvderlm

Anyone come across Dergo filters before?

 

I can only find a few images for Fiat 1100 twin choke carb filters, but no company history or other information. 

 

The filter element looks like scrunched up wire wool. I'm sure it flows better than paper element.  I can imagine it stopping insects and dandelion seeds but not being as effective as K&N oiled cloth or polymer coated Ramair foam

to keep roadspray suspended rock-salt, grit, tyre rubber, diesel soot and pothole dirt out. 

 

I want a filter that covers the DHLA idle circuit, which trumpets plus foam socks do not. And found some Dergo for Alfa twin carb filters.

imageproxy.php?img=&key=a31c107f08879a83imageproxy.php?img=&key=a31c107f08879a83dergo-filters.thumb.jpg.960694e27ae88e0f50b581c64889e12f.jpgdergo-filters-open.thumb.jpg.df41bf9673ed798d14012ece329c77b9.jpg

 

In a bit of a mess...

 

This is the wire wool construction

WIN_20181204_18_31_39_Pro.jpg.8de6606f0bb880b1e8d8141c9785f8a7.jpg

 

 

You can see I'm pushing it out from below with a sheet of Ramair foam.

 

WIN_20181204_18_44_42_Pro.jpg.70dda25cf36e64d670d48f8b1db0f7ff.jpg

 

 

 

 

Fitted longer m5 spacers and new m6 studs and nuts.

 

WIN_20190103_19_56_16_Pro.jpg.0193a89cc925d3fb5cbe20b9eda41cd4.jpg

 

Clean up the cases

 

WIN_20190103_19_56_52_Pro.jpg.7269c063672dfc4ee8b039de95336142.jpg

 

Should keep carbs clean and shortens the inlet.

 

Can't decide about the vacuum and breather ports.

Blank them or use with Y-piece from the breather pod on block? 

WIN_20190103_19_56_35_Pro.jpg

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dvderlm

Looks like they were black

See the source image

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dvderlm

on a weber 32iba … with some ingenuity!

s-l1600.jpgs-l1600.jpg

Edited by dvderlm
  • Like 1

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LR5V

Ram-air material looks like a good upgrade  - I can see you have spaced them out the cover from the base plate - how much space have you given between trumpet & cover?

The recommended minimum is 25mm

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dvderlm

I'll have to measure. My existing trumpets are 45mm, and there's 27mm to bulkhead for tightest fit.

There's no trumpets inside the filters (yet).

Trying for very short inlet tract. Wondering about ITG stubbies, or some half donuts of nitrile or viton with 40mm internal diameter.

 

Might chop some old bike carb trumpets or get creative with fibreglass,

 

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dvderlm

Proximity of trumpet to firewall has worried me.

One has 27mm gap.

 

Each Dergo now measures 38mm from front to back inside faces. And entire filter is 69mm at deepest point.

Mostly it is 50mm deep and nuts are 5mm so there should be clearance to attach them 🙂

 

I think I have 72mm from back of the carbs to the firewall at thinnest section, so it might 

need to some "percussive adjustment" if things are too close for engine rock, if I cannot simply

turn the rear plates upside down to mind the gap.

 

With no trumpets inside I reckon I'm just adding 5mm to inlet tract which I think is

92+65+112+5 to give 274mm which matches 3rd harmonic Helmholtz at 6400rpm

with ~270 duration cam

according to 

https://exx.se/techinfo/runners/runners.html

 

or 3rd Helmholtz at 7000rpm using Daipipes which reckons I only get weaker 5th Harmonic with 311mm

inlet that existing 45mm trumpets provide.

 

Alfa Romeo did not have trumpets inside the Dergos and were only ~26mm deep front to back inside faces. 

(I'm pretty sure I added 12mm spacers)

 

Edited by dvderlm

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dvderlm

Going to try chopping four of these down to size.

41fjHz4THxL._SL1001_.jpg

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dvderlm

Chopped the toy trumpets (after checking petrol and heat does not dissolve them)... a bit too deep, but adjustment possible.

WIN_20190505_14_14_29_Pro.thumb.jpg.b652fd0369d51e42952e88671071554a.jpg

 

I decided to cap the random breather and inlet holes for now.

WIN_20190505_14_09_00_Pro.thumb.jpg.c241f80e5e9b203c49183ea0b52b445e.jpg 

 

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dvderlm

Test fit... won't go over the inlet studs without severe bulkhead bashing.

2116297584_WIN_20190527_15_08_39_Pro(2).jpg.e8e9c9c55d7f58bfccebfa390a84c0b4.jpg

 

I've seen some studs with inner hex fitment  before so could maybe fit through carb holes against the manifold facings.

Misab plates will be awkward

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dvderlm

Volksbolts do the inner hex m8 studs - currently out of stock. But I usually fit trumpets once carbs in place - so tried with Dergo partially disassembled a few spacers removed.

WIN_20190527_16_45_13_Pro.thumb.jpg.8189ec2225f81c324590c1e944f8dac8.jpg

 

That works on the spacious side of the bay. It could work on the tighter section too. Right, in with the 31mm chokes. Don't want to do this too often.

Rain clouds approaching. 

 

 

 

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dvderlm

Don't think there's anyway I can get the trumpets in and fit / remove spacers.

I'm using an 8mm ratchet spanner whose head would be obscured from sight and have only limited movement.

The red trumpets are probably too close to rear of filter wall at current depth in any case, so I can take my time shortening them.

 

Nothing for it, got to break the cardinal rule of carb experimentation.

  • Change one thing at a time

So shorter inlet tract, maybe larger filter surface area, no trumpets - in fact a hard step from 45mm to 40mm, 32mm chokes but with a laminar-flow destroying liner tube making for 31mm- ish chokes.

 

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dvderlm

Lost a nut while trying to fit the most awkward one. Searched with a magnet and found the crinkle washer in a crevice, but the nut is brass... 

Chopped down a spare spacer instead and fitted to the car.

 

One misab plate was annoying. And I can't use a long straight 1/4" drive on the carb to inlet manifold stud nuts because the filter front plate gets in the way.

WIN_20190602_17_07_46_Pro.thumb.jpg.3502c7f3420dbf5ed5bedb38ab8822ed.jpg

Not re-started or driven yet. Should be quieter than the trumpet + socks.

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dvderlm

Found 2 spare nuts like the one I lost. Can't decide whether it is worth the pain to fit it to be like the rest.

  • on the negative side - might lose it too
  • on the plus side - be easier at next removal

Described as black stainless steel cap nut, but my magnet that can lift cutlery does not attract it.

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dvderlm

Gave up trying to swap it. I can get better  access by removing a grommet in bulkhead AND raising that carb, which means undoing 4 stud nuts and unsealing the Misab plates.

 

Edited by dvderlm

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dvderlm

Found some other trumpets that could be cut to size.

Only 38x more expensive than the toy ones.

https://www.youtube.com/watch?v=YNamh_4MwVI

Nice colours though, and golf ball surface.

They like non-laminar flow.

 

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dvderlm

Today 84% humidity + 10deg C dew point at 13deg C ambient equals carb icing.

Going to put the warmed air intake back on.

In June, where's the gulf stream? Climate catastrophe.

 

Engine losing power running rough then stall after high vacuum. Sit for 3 minutes and it would restart.

It's icing or the Hall sender. 

Edited by dvderlm

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dvderlm

Warm air tube from exhaust manifold to the Dergo's helped a lot.

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dvderlm

Not the Hall sender. No stumbles at all with warm air tube. Icing or condensing fuel on bottom of an inlet runner.

They are quieter than trumpets but not much at full throttle.

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