Engine Comparison Chart

1) Introduction

One of the things that really gets to me is the attitude in the Modelling Press that all engines perform the same, and that if they don't, they soon are a thing of the past. Shades of the MDS.48.

Woe betide the poor purchaser in that case !     --------         I would not like to be the one to tell him !

This does not help a beginner at all. Also,which ones do you use for Combat where you need more speed to be competitive, and power to overcome the drag of a streamer.

Engines are definately different, depending on their porting and carburrettors. Granted, well tuned two strokes will perform similarly, but which ones do and which don't ? The figures and comments presented here are from my own tests and other owners at the field.

The parameters the average modeller is interested in are ;

1) Ease of starting.

2) Power.

3) Ease of tuning (carburation).

4) General ease of use.

5) Fuel required.

I've deliberately concentrated on the two stroke .40 to .48 class of engines as these are the most popular for Combat.............................

So that each can be evaluated fairly, the following needs to be standardised ;

a)  Same propellor size and spinner used.

b)  10x6 for .40 size engines and 11x6 for .46 - .48 size.

c)  Starting qualities.

d) Fuel type and how fussy about Nitro.

e) Spare Parts availability.

f) Without access to proper bhp measuring equipment, revs.will give an indication of available power.

g) Plug Preferences.

Any Club Members wishing to contribute are most welcome - email to ianscottowi@wingers.co.uk

2) Engine Performance Figures

3) Users Comments (not necessarily mine)

4) Plug Performance (2 stroke)

5) Recommendations for Beginners (so far)

Irvine .40 or .46     (pricey but quality performing product)

ASP .40 or .46        (cheaper but all-round power and performance as good as the Irvine)

Super Tigre .45     (pricey but quality performing product)

6) Replacement Carburettors

7) 2 Stroke Fuels (Manufacturer's Recommendations)

A) Aero Engines

Having used Irvine Sport 5 or Moglo 5 for around 4 years without problems, I don't think this is as critical as on Helis, due mainly to ;

a) More cooling air available from the larger area propellor.

b) Engine is not at maximum revs. most of the time.

c) Both Fuels contain a minimum of 18 or 20% oil including 2% castor.

b) Helicopter Engines

This is becoming more critical on Model Helicopters due to the many known (to me) cases of rear bearing failure. The cause of this is unproven as yet, however ;

1) The heat generated is high , especially when hovering.

2) The revs. required to Hover or fly Circuits is constantly high, unlike an Aero engine.

2) The small fan employed cannot move the same volume of air, compared to a propellor.

3) Cowls/canopies are not ventilated properly, if at all.

4) Oil content becomes more critical the hotter an engine gets. The oil acts as both a coolant and a lubricator.

5) Fuel manufacturers tend not to publish the oil content of their fuels.

6) The more Nitro used in a Fuel, the more heat is generated, requiring more oil to cool it.

7) Setting an engine lean will increase the head temperature and the chances of failure.

8) The only way to set up an engine correctly (assuming the correct fuel) is via head-loaders.

One can conclude from the above recomendations that Aero engines can generally get away with 18% minimum oil content as long as it includes 2% castor and only 5-10% Nitro. In fact (Model Technics) Irvine Sport 5 has only 18% synthetic oil (Klotz) and works fine as tested by me.

However, Helicopter engines produce a lot more heat due to a lack of airflow over the engine, tend to be run harder at constant revs.  and need more cooling. They need 20% minimum oil with 2% included castor with 5-10% Nitro.

Increasing the Nitro content above 10% will need a corresponding increase in the oil %.

A general summary of aggregated Fuel Manufacturer's Recomendations for Helicopters follows ;

Fuel Manufacturers who do not state their nitro / oil contents should be treated with suspicion.

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