Posted Friday, March 16, 2012 @ 02:30 AM  

I have simply drilled out my original 1.25mm jets.

British Fournicators can order a 1.32mm drill bit (or 1.30mm, or whatever) from Drill Service Horley, 01293 774911, give them your credit card number and it will arrive in the mail the following morning. Price last time I bought one? Not much more than one pound, including postage.

If you inadvertently drill the hole oversize, simply heat up the jet with a mini-blowtorch and run some solder down the hole and then re-drill.

Just be very, very careful to clean out all the swarf.

It doesn't take much to block even a 1.32mm main jet!

Yours, Bob

Posted Friday, March 16, 2012 @ 03:54 AM  

Yours, Bob

Posted Sunday, March 18, 2012 @ 08:47 AM  

I am certain that those jet sizes I stated are correct for my engines -- 1.32mm for a 1400cc engine breathing warm lower cowling air, 1.40mm for a 1400cc breathing cold air and 1.42 for a 1750/1776cc Rectimo breathing warm lower cowling air.

And of course, the first thing I did was to buy a third Zenith 28RXZ carburettor before I started experimenting. Last time I was there, Ken Ballington had several, although I think he wanted #100 for them.

Oh and PS, I think what you're reading on that pdf is a computer translation I cleaned up for Eugenio, after which I believe he has added (in his opinion) those jet sizes. I don't think you'll find they were in the original, nor are they official, just his opinion.

If you visit http://www.fournieruk.com/ and click on Technical, then on Manuals and then click on Zenith 28RXZ carburettor (French/German) you'll find the original document, which does not include Eugenio's spurious data.

The official figure I've got for one of the biggger aviation VWs (can't now remember which one -- maybe the 1700 Limbach with the 28RXZ) used a massive 1.50 main jet and I think also a bigger mixer tube (emulsion tube or main discharge nozzle). But of course that had a carb heat system, so it was effectively a 1700 (1.42 jet on my 1750) with the cold air intake (1.40 jet on my 1400). So in that case a 1.50 jet would seem pretty correct.

Yours, Bob

[Edit by Bob Grimstead on Sunday, March 18, 2012 @ 08:57 AM]

Posted Tuesday, March 20, 2012 @ 09:47 PM  

That is very interesting -- if a little strange!

All I can say is that with my Zenith carburettors and on my 1400 and 1750/1776 engines, these are the correct jets.

Also, I know of three engine failures (two in 1400s and one in a 1500) caused by these bigger engines running too lean.

Yours, Bob

Posted Thursday, March 22, 2012 @ 09:39 PM  

I did not know that about the jets being stepped internally.

When I made my 1400cc conversion on my Australian Fournier, rather than drill out the original main jet, I got a friend to make me two spare main jets, and I have opened and closed those over the years while investigating mixtures.

The Australian Fournier is now operating with a 1400cc engine and the locally manufactured jet at 1.32mm, the British one now has a 1776 engine with an original jet, bored out to 1.42mm, while Matthew's 1400cc WEK engine again uses a 1.32mm jet bored out from the original. Those sizes works well for us in all three cases, and last time I checked, all the float levels were to specification.
We have flown about 180 hours on the British engines and about 350 on the Australian 1400 with no problems.

All these engines use the original carburettor, intake manifold, single-port heads and standard valves and rockers, although I think my 1776 heads (also based on 1600s) may have slightly bigger valves, and it has 32mm exhaust pipes.

It is fascinating that you and I use such very different jet sizes in our engines, but of course, as you say, there are other variables.

The most important thing is that none of our Fournier friends should have lean mixtures and high combustion temperatures, because that will lead to engine failures. Provided everybody is certain that they are flying with the correct mixture, they will be safe.

Another topic...
When flying formation cross-countries with Matthew, who cruises at 3,050rpm in his 1400cc RF4D, burning 10 litres per hour, I seem to burn about 11 litres per hour cruising with my 1776cc engine, using 2,800rpm with the same propeller as his, and cruising around 90-95 mph (145-150 kph). I would expect my consumption to be at least 10% higher than Matthew's, but it would be good to confirm this. Do you get similar consumption?

Thanks, and I look forward to meeting again at Husbands Bosworth this summer, if you are coming over again.

Yours, Bob

Posted Friday, March 23, 2012 @ 04:11 AM  

See http://sbeaver.com/cgi-bin/fournier/cutecast.pl?session=xBT5CTDiFxbpKRLO7KcVdHRU61&forum=13&thread=406&page=2 for my 1400 fuel consumption averaged over 30 hours.

Yes, I follow Matthew -- he predominantly does the navigating and I mainly keep a lookout -- although of course we both do both in reality.

We have the same airframes, same props etc, only difference is the engine capacity.
A larger capacity engine will always use more fuel than a smaller one in identical circumstances (provided both are running with the correct mixture of course).

I have not been running the 1776 for long enough to get an accurate fuel burn increase, but it seems like about 10 per cent, rising from the old 10 lph to about 11 lph (same distance, same speed, identical other conditions). I just wondered what Eugenio averages with his 1776?

Since we've had enquiries from Italy, France, Belgium, Germany and Sweden (although nothing is definite yet) we may soon get a good opportunity (or two) to check the 1776 consumption over an extended period.

Yours, Bob

Posted Sunday, April 8, 2012 @ 06:48 AM  

You are right and I am wrong.

One of my problems is that the Australian Fournier has the original tachometric tacho, but the British one has a Westach electronic one, which reads 300 rpm when the engine is not running.
I assumed the error was just that I had to subtract 300 rpm from all readings, but it is clearly wrong at other rpm too.

Yours, Bob