Posted Saturday, August 13, 2011 @ 05:36 PM  

Yesterday I started my engine with it's new barrels and pistons, slightly apprehensive about what would happen. Would it overheat, would it seize, would it even start? I ran through Eugenio's test protocol recording RPM, CHT, oil temp and oil pressure at one minute intervals, though I broke the protocol into 3 sections to allow the engine to cool and to 'feel' how the engine was when turned over by hand. Maximum CHT recorded during the entire set was 145°C during the full throttle 2 minute run at the end, though most of my recorded numbers are in the 125°C - 130°C range. Eugenio's numbers gave an anticipated CHT of 180°C with a 'Do Not Exceed' of 220°C, so I was comfortably within those. Oil temperature peaked at 62°C. Running was initially a little 'rough' but evened out some as the test progressed.

Afterwards I went over the engine looking for and tightening anything that had loosened, the sump cover nuts being the most obvious slackers.

This morning while it was cold I reset the valve rocker screws, added a couple of little baffle extras and checked the oil. This afternoon I had two flights totalling 90 minutes, mostly flown at 3000 RPM, where I saw and recorded CHT and oil temperatures broadly similar to the ground test figures. One very noticeable result of the change is that the engine now runs very much smoother so I suppose my motor has being deteriorating for years but so slowly as not to be noticed.

Having flown it, next task when it's cold is to re-torque the head studs before continuing the break in, but I'm pleased with how it seems to be going and with the results so far.

Posted Sunday, August 14, 2011 @ 03:29 AM  

One of the prompts for doing the work was that one side of my engine had become smokey. At first I thought it was a mixture problem or maybe an induction bias, though why that should develop I could not figure. Latterly, as well as light smoke staining I'd been seeing evidence on the starboard fuselage side and wing root of tiny oil smuts leading me to the conclusion it was oil getting past the rings and ejected through the exhausts. The old piston crowns show a markedly blacker top on the right side than the left with the front right being the blackest and oiliest. Based on plug condition and exhaust staining that pot was the prime suspect as source of the smuts.

Based on very scant evidence there are tentative signs that fuel burn might have reduced. This is not a firm conclusion but I'll monitor that as well and see what conclusions I can come to. I suppose if volumetric efficiency has been restored it should be better but it will be useful to quantify. Spreadsheets are great tools for tabulating and analysing this stuff.

I must see if I can figure out how to post pictures on this board. I think I have to upload them somewhere first and I haven't yet figured out how to do that other than to Picasa.

Donald

Posted Monday, August 15, 2011 @ 03:09 AM  

I know how to insert the URL into a post but it was the business of getting the pictures uploaded that I was struggling with. I'm feeling my way with the wiles of FTP.

Also, I've been through and through my carburettor in the past and I'm confident it's as good as it can be given its age. I've also taken care to align the induction manifold joins to eliminate any possibility of user induced induction bias, but it was the appearance of the smuts that persuaded me I had oil getting past the rings.

OK, here is a picture of my old pots. They are in the same order as when on the plane, top of the picture is the front of the engine and left is left. Front right was the oily one:

New pistons and cylinders on the left:

Typical clamping to measure the deck height:

New pistons and cylinders on the right:

All copiously slathered in oil.

Posted Tuesday, August 16, 2011 @ 03:06 AM  

The old pistons look horrific, don't they, although it appears to be surface deposits rather than erosion of the crowns. The strange thing is, though, that even like that the engine ran rather well. My only observation about its output is that the Fournier's cruise speed has been less that it used to be though the climb seemed as good as ever, but my prop has been slowly deteriorating too. Everything counts and I'm in the process of either getting a new one or having the old refurbished. Awaiting quotes.

I'm rather hoping that having posted the photo of the old pistons someone with more knowledge than I will diagnose the cause. In particular I'd like to understand the right/left imbalance. An obvious suspect would be a left-side induction manifold leak leaning the mixture on that side, but I've been over that in the past and I don't believe it's the cause.

Posted Tuesday, August 16, 2011 @ 05:23 AM  

Well done! And very meticulously accomplished, as you apparently do everything.

A couple of possible tips:

In general --

Wet black pistons/heads/plugs = high oil consumption.

Dry black pistons/heads/plugs = excessively rich mixture.

To me, your pistons seem quite dry.
Over-rich mixture on one side of the engine would also explain those slightly increased vibrations.

If there are no leaks in the left induction system, maybe there was a small obstruction somewhere on the right side, like an ill-fitting gasket, or a flap of rubber cut out of the rubber tubing by the metal tubing as it is inserted?

Or, of course, it could simply be 'just one of those things'.

Propellers:
We are getting Rupert Wasey of Hercules propellers to make us a custom RF3/4 1400 propeller.
He thinks he can provide us with even more performance than we get from our special Australian ones.
We will do some very specific test flying with a prototype or two before the final version is cast in CNC.
If you can wait a couple of months, that might be your best option.
They cost around £750.

As to posting photos on this forum, see http://sbeaver.com/cgi-bin/fournier/cutecast.pl?session=iWFbaxinVPrj2RUndKyjJ6i8pu&forum=18&thread=455

Good luck.

Yours, Bob

Posted Thursday, August 18, 2011 @ 03:28 PM  

PS. if you swap yours over from right to left there will be less chance of rain entering and pooling in the mufflers.

Posted Tuesday, August 30, 2011 @ 10:59 AM  

A small point about exhaust cracks.

My experience has been that the rear pipes (the short, straight ones) crack much more frequently than the front ones, and Bobby Warren the Skyhawks engineer confirms that.

Yours, Bob

Posted Saturday, September 10, 2011 @ 01:55 PM  

I've flown about 6 hours since changing my barrels and pistons and my fuel consumption seems to be down to under 8 litres/hour. OK none of that has been at maximum continuous cruise but it's not been just loitering about either. Compare that to my fuel consumption to and from the CFI Husbands Bosworth meet in July when I averaged around 9.5 l/hr.

Posted Tuesday, September 13, 2011 @ 02:20 PM  

Yes but remember I have not just increased my engine to 1400cc. It's been that capacity since 1989. What I've done is maintenance not a modification.

Posted Monday, February 13, 2012 @ 00:03 AM  

To give you some idea of what fuel a 1400cc VW should consume in an RF4D, here are the figures for my Nordic tour:

2073nm in 29:25hrs at various power settings used 257.7 litres of fuel, giving 8.75 litres per hour (consumption 8.04nm per litre) and 70.5kt or 81mph groundspeed.
That's the whole round trip, but when I was flying downwind I throttled right back to let the wind blow me along.

Coming home all the way at high speed cruise (3,000 rpm with my propeller) took 15:20, and I burned 147.2 litres, which I make 9.6 litres per hour.
This gave me 69 knots ground speed in a variety of different winds.

I would suggest that if you are burning much less than 9.5 litres per hour you are running lean, and if you use less than 8 litres per hour you are running dangerously lean.

In the past couple of years we have had several RF4 1400cc and 1600cc engine failures immediately after take-off in very cold but dry weather because they have been using the original carburettor with the original standard main jet and needle valve, and without checking the fuel flow at the main jet or the fuel consumption to ensure they are running rich enough.

The problem is that some pilots (glider pilots especially) think that a low fuel consumption is a great thing.
But it is not. Much of the fuel you burn in an air-cooled engine is used to cool the valves and cylinder heads. All air-cooled engines should run slightly rich at full throttle or you're going to have trouble.

The engine may run fine in the summer, when the air is warm and thin, because the mixture has just enough fuel in it to provide continuous combustion.
This is the same as flying high. Your engine will run richer when the air is thinner.

But on a cold day in winter, when the air gets more dense, if you're running with the original carb & jets there may just not be enough fuel to sustain combustion.
You're OK at first, while the engine is not fully warm, but once it gets warm there just ain't enough gas to keep it going, and the engine fails at 100 or 200 feet.

If you can get past that barrier and climb to 1,500 feet say, then you'll be OK, because the air there is thinner.
But then what happens when you need to go-around after going back down to low level?

To me this is just bleedin' obvious. If you've increased the engine's capacity by 17% and its compression ratio from 7:1 to 8.2:1 (which is precisely what you do with the 1400cc conversion) you will increase power output by perhaps 25%.
And you do notice a huge difference in performance.

But you should also see 20% to 25% increase in fuel consumption, to give you that extra power.

If you don't see that fuel consumption increase, you're running lean, and that means higher internal head temperatures, a short engine life, and a high likelihood of having a valve head snap off (and then you DO have problems).

Another symptom is a loss of compression and the need to grind the valves more frequently that at 1,000-hour intervals.
If you're having to remove the heads and grind the valves because of a loss of compression after as little as 200 hours, then you're running lean.

I've said enough.
Don't blame me you lean-running guys if you have an engine failure after take-off, but if you smash up your Fournier in the process, you can expect visits from lots of angry Fournicators.

Yours, Bob

Posted Monday, February 13, 2012 @ 08:30 PM  

I think if you've opened out your needle valve to 2.5 mm and the main jet to around 1.3mm you will be fine.

When I get a spare half-day I shall run my 1400cc engine with the NGK AFX lambda sensor to get readings to confirm those figures, but I've been using the blue one with those jets for seven years and have had no problems.

Loitering at 2200 rpm should cause no problems at all. The engine will be nice and cool, even in the low cooling airflow of low thermalling airspeeds, because the throttle will be nearly closed. Also you are presumably fairly high, and of course the higher we go with a fixed jet carburettor, the more rich the mixture becomes. It's the sea level take-off on a cold dry day that causes most problems with a lean running engine.

PS I have submitted my Nordic trip article to Philip Whiteman at Pilot magazine and Francois Besse at Pilotes. Both say they will probbly use it 'one day'.
Christina Lindberg at Flygrevyn does not want to use it because 'it was so long ago'.

Thank you very much for your praise of my Fournier air test article. You're very kind, but I think the joint one we submitted to the on-line EAA magazine was better, partly because it was longer, so there was more information in it, but also because it was the work of several people, so had a broader information base.

I did enjoy taking the inverted photos for the Pilot article though!

Very soon Pilot should be running my more recent (but more quickly written) account of my golf course landing.
I have also submitted that to Flygrevyn (together with my piece on learning formation aerobatics).
We shall just have to wait to see whether Christina wants to use them.

Meanwhile, enjoy your ice-sailing, and let us hope that all of Europe and America have a summer of good weather this year.

Yours, Bob