Activ8

[Trevor Lyons]

In case you haven't delved into the Activ8 website too deeply, some test results are here: http://www.simplan.co.uk/testresults/testresults.html

[Andrew Leak]

Hmmm, it's about time we had a decent debate about the costs of aero engines and related paraphinalia Trevor!

Your Quote.. "As I said, fine for mopeds. But when an aero-engine costs more than a family runabout, surely the buyer is entitled to something that is efficient, modern and not potentially lethal. My Midwest wankel engine was originally fitted with simple Tillotson "lawn-mower" carbs that never worked properly. Now it has a relatively simple fuel-injection system (based, I'm told, on a Triumph TR7 unit); and it's excellent - smooth throughout the range, economical, and with no carb-heat or mixture nonsense."

Like I said, anything aviation is costly. No matter how hard you try to compare the manufacture of motor vehicle engines and the relatively average cost, in comparison to aero engines, you are never going to win as manufacturers don't produce millions of aircraft engines every year and thus the costs are higher. It's like anything, if it hasn't had an even modest production run and the spares aren't in every high street stockist, then you ARE going to pay a premium. Take some of the older vintage cars (let's say a 1950 Ford Prefect - my C90 is about that vintage) do you think that all standard motor parts stockists are going to have a head gasket set on the shelf now? Only by special order or from enthusiasts clubs (in the case of aircraft, LAS or AircraftSpruce). The technology today is different, I admit, and cars are more complicated, but motor manufacturers have us at a disadvantage as consumers purely because the cars we drive have the ability to stop when then break down, often inconveniently, but they don't have to land in a field/water and risk life and limb. They are then towed away and fixed - you can't have that niggle of slight technological unreliability with an aircraft it would be too dangerous for all concerned.

Yes, you are right. We should be getting better engines for our money, but you are only likely to achieve this if the bureaucracy around the licensing and certification was reduced and as I am using what is basically the same engine that would appear on a certified aircraft, all the development and paperwork has been done to a 'higher level' than I need but we have to pay the same. So do we put up with it or not? If I wanted to replace my C90 with a similar auto engine then I would have to jump through an incalculable amount of hoops and probably across several bureaucratic 'minefields' to get what I want (if I could - even with LAA support).

On the subject of 'carb heat' it is simple to apply to most aircraft with an electrical system with a thermostatic heater control, if only we are 'allowed' to make these simple 'mods' without the hassle of having to prepare an analysis that would satisfy NASA scientists to let you to even test it on your aircraft, then all the better. I am not holding my breath.

Your original quote intrigued me:
" First. a number of cars (eg Alfa Romeo Twin-Spark) and bikes (eg Honda VT500) DO use twin plugs, but still surprisingly few. It's neither that difficult nor that expensive; especially as a single coil (albeit a higher spec one) can be used for both plugs in one cylinder. This is done by having the first plug "earth" to the head, with the current returning across the second plug cap and back up the lead. I predict that the advantages in performance, economy and emissions will make twin-spark engines increasingly common. "

I disagree, no manufacturer to date has your enthusiasm for twin spark plug applications. Yes there is a slight increase in performance but when you have a computer and VVT that can work out the optimum performance of an engine with its ECU, you don't need more trouble with sparking plugs. Bill is right about the space issue - most manufacturers want to maximise space and keep the vehicle production costs down. Mercedes went from a 2 plug per cylinder system in their M272 engine to single plug as VVT sorted the power issue out. Just for my own amusement, when I have the need to look under the bonnet of a car I can't see a darn thing, plastic covers and the way the engine is fitted (normally inserted underneath) and the way any work including cam belts can mean an engine out job - this is to cheapen the production process and keep the line of the car lower as well.

As for the lawn mower size carbs, when I was 19 I had a mini cooper 'S' (original) 1968 mk2 with those horrible 1 1/4 inch twin carbs. I threw them away and fitted some 2 inch Jaguar carbs (re-jetted and new manifold of course) this solved the issue. You have got to realise manufacturers have an obligation to the system that lets them sell cars, environmental issues, power and speed restrictions etc etc. If you have watched 'Top Gear' they often drive super cars that have been 'limited' to some silly 150 mph + speeds. Thats what you can do with the technology, get ever more power out of the basic substrate - people have been doing it for years, with engine re-mapping or building a serious and more powerful engine to name a couple. But we don't have that luxury with aircraft, we have put up with what my aero engineer says is 'tractor technology' and an engine that is so heavy yet functionally simple, it is untrue. The costs do not support this!

Well that's about all I can add, I will get back in my box now.

regards,

Andrew

[Brian Hope]

An interesting discussion which raises a number of points. the twin spark issue for instance. Whilst its use on large bore engines has the benefit of producing more power, on smaller bore higher revving engines I suspect the advantages are considerably minimised and the space better taken up with the likes of four valves per cylinder.
I'm not an advocate of the 'agricultural is bad' philosophy. Big bore slow running air/oil-cooled simplicity works well for me. I'd also rather a carb than a complex injection system with its very high pressure pump and hoses, and the simplicity and non battery reliance of magnetos takes some beating. I'll admit that a similar stand alone electronic system can improve performance but once you have to have a battery and charging system to provide the sparks you are once again heading down that road to complexity and more chance of something going wrong.
The oft used argument for change is efficiency, but on a recent trip in an RV9 we were throttled well back and leaned out on a 150hp Lycoming and showing 110kts for 17 litres per hour. 130kts showed 22 lph. Some of the wizzy Jab and Rotax powered machines can match that, and a few can beat it but not by much.
The question I have re oil additives is that if the additive is so exceptional, why isn't the oil manufacturer putting it in himself? There have been a variety of jollops available over the years, most falling by the wayside as their promised properties have failed to come good. This new one may well prove to be quite wonderful, but I for one would not use it in an aero engine until somebody had carried out some meaningful tests with it.
Makes me sound a bit of a Luddite I guess, and really I am not, but reliability has to be the number one factor with an aircaft engine, and for that simplicity and a very good reason to fix what isn't broke are primary considerations.

[Trevor Lyons]

You are never going to win as manufacturers don't produce millions of aircraft engines every year and thus the costs are higher.

Up to a point, Lord Copper! But if, like Jabiru, you are producing engines in tens rather than tens of thousands, you adopt low-output manufacturing techniques. That is what Jabiru and others do, using CNC machining. But the Jabiru is now being overtaken by a Belgian clone, the UL260i, that uses fuel-injection. Given the choice, I'd take the Belgian engine anyday

And although this is a subject that divides opinion, I would also like to see both the Jabiru and the UL260i with a gearbox. A simple 3:2 reduction using a Kevlar toothed belt would do the job. Then these engines could run up to their maximum output @ 3,300rpm, while an efficient large-diameter prop turned lazily at no more than 2,200 rpm. As it is, these motors can never manage more than about 2,700rpm, driving pathetically small props!

[Bill McCarthy]

About 23 million VWs have been built and there must be several thousand quite happily purring away doing the job in homebuilt aircraft. I suppose they would benefit from a drink of this new stuff, however, STP oil treatment stuff has been going for yonks but I never hear of anyone who has used it in this application. One product I know worked was the Red X stuff that you added to your petrol tank at a squirt per gallon at a ha'penny a shot at filling stations. I had nothing better to do on a weekend and did a cylinder head inspection after about 40,000 miles (from new) just to have a look see. There was not one spot of carbon in the head or on the valves and everything had a copper colour to it.

[Rob Swain]

... you are never going to win as manufacturers don't produce millions of aircraft engines every year and thus the costs are higher.

If we are discussing the costs of engine design etc, the basic Lycoming and Continental designs have been in production for decades (with only minor modifications once in a while - and often to cut costs), and with what has to be a massive profit margin on the price of the engine they must have recouped the design and tooling costs by now.

It's also interesting to note that when these engines were designed they had some relatively radical technologies for small engines such as the layout of a flat four/six, and hydraulic tappets which didn't really reach normal cars for another twenty or thirty years.
Let's be honest - to all intents and purposes they are museum exhibits now though. So what went wrong?

I quite like the Jabiru engine just for it's simplicity and affordability and respect the Rotax 91X series for its power and reliability (but hate the plumbing and gearbox), but I can't help thinking that the UL260 looks like the way forward.
If they made the UL260 with a small Continental (A-65 thru O-200) compatible mount (and prop boss?) then I reckon they'd get a lot of interest from people with tired Continentals in homebuilts. Might be worth looking into a similar situation for small Lycosaurs as well although my experience of them is somewhat limited.

[Trevor Lyons]

I ... respect the Rotax 91X series for its power and reliability (but hate the ... gearbox).

If one acknowledges that the Lycosaurus should be in a museum, then surely it is time to embrace the reduction gearbox. Ships have them, turboprops have them; and so should GA aero-engines. A reduction gearbox is a simple and reliable means to allow BOTH engine and prop to turn at optimum revs. Engines like to turn fast, props like to turn slow; so an aero-engine without a reduction gearbox is either turning too slow, and/or the prop (that will have a smaller diameter than is ideal) is turning too fast. QED!

[Rob Swain]

I'm not against gearboxes - just the Rotax 91X one. When the engine stops it sounds like it has seized, often followed by a rather unpleasant rattle!

It also looks like a horrible add on. It's not what one would regard as being a sleek and elegant solution to putting a gearbox on the front of a flat four engine. I assume the approach used is to accommodate the prop being mounted above or below the engine, being a throwback to its microlight roots.