New engine

[Paul1954]

Hi Sven,

For my interest, can you give details of your engine fit?
What carb?
Which ignition fit?
Electric starter?
Backplate fitted or not?

On the last point, if fitted, did you have to modify the standard mounting?

Thanks.

[svenolivier]

Hi Paul

Certainly
The engine is a 2.1 Aerovee
The original Zenith KLP
Dual ignition - top spark plugs fire on the Surefire electronic ignition which is fitted on the distributor drive shaft; the bottom plugs on a Le Burg (single) system
(Tom Heaslip at the time of fitting the electronic ignition could not get a dual Le Burg system and fitted the above combination. - I flew the previous engine for 40 hours on the Le Burg only - as the replacement heads were single ignition)
No starter motor - I start on the Le Burg - reasonably easy to hand prop
An altenator fitted, but no back plate.
Mounting is standard
I hope this shed some light

Kind regards and thanks again for all the information and assistance - it is greatly appreciated.

Sven

[Paul1954]

Thanks Sven. Is the carb up-top or below stairs?

[svenolivier]

Hi Paul

The carb is on top.

The oil feed to the manifold is also from the top, whilst the oil cooler feed is from the pump at the front (prop hub-side) of the engine.

It seems to me that I should be able to link the inverted system (Chirsten valve) to the in-flow side of the pump (can i do it by way of a T-link to the hose running in from the oil cooler or should i take the oil cooler inflow to the top of the engine?

Kind regards

Sven

[Paul1954]

Sven,

I am reluctant to answer that question as it may depend upon the overall arrangement.

[Paul1954]

Sven,

Let me add a few thoughts to the last post I made.

The object of modifying the oil system is to supply oil under pressure to the engine in any attitude. A 3-way valve is fitted to facilitate this. When in unusual attitudes the oil migrates to parts of the engine and has to be returned to the sump. On the way air gets mixed into the oil and requires removal (oil/air separator). Not to use an oil/air separator will introduce frothing, and that will cause low oil pressure.

From experience it was discovered that when in unusual attitudes the VW engine oil migrates to the rocker covers. Note the position on the Acro of the oil filler. That was moved to facilitate the oil take-off for the pressure oil feed. ISTR, (it is a long time ago) that the oil pump is a later VW item that moved more oil than a standard item. It is a simple mod to use the redundant hole for the distributor as the oil filler point. Note also the additional sump on the Acro and the plumbing from the 3-way valve.

How you plumb all that will depend upon fitting the various pieces under cowling. From what I have seen, you are starting with a clean and tidy engine arrangement. I would say that if you fit the throttle body under the engine you may find yourself restricted on the diameter of the intake pipe you use as there is only so much space available between firewall and rear of the engine. That is all because of the length of the standard mounting trundles.

One picture I don’t have is of the modified fuel tank vent pipe and it’s positioning on the lower starboard side of the removable fuselage under tray.

[svenolivier]

Dear Niel and Paul

I have now ordered the Raven (Christen valve), new harness, flop tube, fuel tank fittings for the proposed conversion.

I have been receiving assistance from Dave, a VW racing specialist at https://flatfourracing.co.za. Dave proposes a solution which I would like to test with you: to connect the oil pickup inside the sump directly to the Christen valve - this is to be engineered as a fitting which forms part of the sump plate and will have double O-rings. Two additional fittings to the sump plate will serve as the oilfeed via the Christen valve in normal flight and as the breather pipe to the oil-air separator in inverted flight.

Do you think this is a viable solution?

Dave can also modify the rocker covers and engineer a new breather pipe / oil filler fitting (i cannot use the distributor hole as this houses the Surefire ignition unit).

I think this may be the most economical way forward - weight and engineering wise?

I am still trying to get my head around venting the fuel tank in normal and inverted flight

Kind regards

Sven

[svenolivier]

Dear Paul and Niel
Another question - do I interconnect the breather pipe and the oil air separator with the rocker covers and the Christen valve (as it seems the Christen manual suggests) or do i keep separate the oil breather hose and oil/air separator from the rocker cover - Christen valve connection?
Apologies for these questions on matters which would be self-evident to you guys.

regards

Sven

[Paul1954]

Hi Sven,

Can I suggest that you try and make contact with the owner of a Nipper fitted with an Acro engine. They should have a copy of the Acro engine info sheet.It contains schematics of both the fuel and oil system.

It is NOT recommended you try contacting Barry Smith who owned Acro. His health is not the best.

[svenolivier]

Hi Paul and Niel

The rocker covers and sump plate are now at engineering
I have a Revflow carburettor will have to source the fittings and then see if i can get it to run
Still waiting for the parts from Aircraft Spruce.

Thanks to both of you for the help - it is greatly appreciated.

kind regards

Sven

[svenolivier]

Rocker cover converted, sump plate modified for oil pick; oil fill cover, and oil breather box

[svenolivier]

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slowly getting all the bits together

[svenolivier]

Oil valve fitted

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oil breather box

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sump plate

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[svenolivier]

Running into a bit of roadblock with the carburettor - the Aerocarb is tooo big

[Paul1954]

Hi Sven,

When the engine is inverted there will be an immediate requirement for oil to be supplied to it. Are you fitting a small reservoir tank to the existing sump drain point?

Re carb; fitting on top or below? If below, you will encounter the small matter of feeding inlet pipes between engine and firewall. The correct diameter pipes will be too large. If fitting above… many have been there and found the only solution is to modify the cowling.