Fuel Additives

[bob46320]

I am still chasing my tail on the vapour lock problem on the RN - Horizontal expansion loop in fuel pipe from scuttle tank to carb, exhaust pipe wrapped in insulating band, aluminium heat shield over the top of the exhaust pipe .  I am running out of ideas.
She is a standard engine, un-modified with the FZ22B carburettor but with a new rad and 4 blade fan.

What fuel additives are available to make this Ethanol fuel more acceptable to our 7s ??

The other day it was 39 deg C on the road, Fuel tank was 56C, carb 55C, manifold 84C and rad 76C  and the 7 didn't like that.  The engine ran with "power surges" of about 3 seconds followed by power loss of 3 seconds.  

Before it all gets hot, she runs very well.

BobH

[John Cornforth]

I'm not sure it is the Ethanol that is the problem, as I believe its boiling point is 78 degrees C whereas a fair percentage of the rest of the fuel will have an even lower boiling point.  You have tried most things but I wonder if you could reduce conducted heat from the manifold into the carb body by use of a tufnol washer ?  I would suggest at least 3 mm thickness, and stainless bolts would prevent a bridging heat path via the fasteners.  This is only based on surmise - I haven't actually tried this out but it has been standard fitment in more recent carburettor cars.

Today I went out in 30 C heat and had a few periods of hesitation and unhappy running after climbing a hill.  This is the first time I have experienced this "on the road", the only previous incidents having been due to "heat soak" when restarting on a hot day after leaving the car parked for only a few minutes.

[Steve Jones]

North Yorkshire to Derby yesterday and the return today both in extreme temperatures (modern was saying 36 degrees when I moved it on our return). SWB Saloon, bog standard with bronze updraught 22FZ carb. two blade fan and an old but serviceable radiator. Esso Super Unleaded which now contains 5% ethanol around here (it says so on the pump). Around 80 miles each way both done in just under 3 hours including Traffic Light City (Mansfield and surrounds) and the Derby Inner ring road. Car never missed a beat. Didn't over heat whilst standing in traffic, cruised along at 40/45 mph when it could, used no oil and no water. If mine can do it, yours should be able to. I'd be looking at the simple things. Ignition timing, weak mixture and the like.

We were hot though!!

Steve

[Dave Mann]

    Does your car have the plate from the body side under the exhaust as shown in the photo. One of our RNs had this plate and suffered from the fuel boiling in the float chamber,  the other one didn't have the plate and didn't have a problem so the plate was removed.

[John Mason]

Good news on the ethanol front I heard on the radio the other day that they are thinking of stopping adding it to fuel because of emissions. The bad news is we don't know what they will replace it with.

John Mason

[Reckless Rat]

Whilst I accept that the current heatwave in France is a problem, I share Bob's frustration at not being able to alleviate his fuel starvation problems particularly when others amongst us aren't experiencing the same. I suspect that it's a general build-up of underbonnet heat that is exacerbating the problem.

Bob, have you tried raising the rear edge of the bonnet to allow some of the air to escape. You might have to reverse the radiator stay so the closed end for the hinge is at the front. A small wedge under the rear edge of the bonnet should then act as an additional louvre to allow more air to escape. I was done in the "olden days" in the winter to stop the windscreen from icing up. Worth a try at least.

Is there any restriction to fuel flow at all between the tank and the carb, for example in-line filter or perhaps some restriction in the fuel tap or the filler vent? Just trying to think outside the box a bit.

If all goes well the "canicule" should be over after the weekend.

[bob46320]

Like Reckers says, the under body heat doesn't help, that and a scuttle tank brewing the fuel up !!  I wonder what precautions / changes were made for countries like India and Africa back in the day ?

In reply to Reckers, no in line fuel filter, jets all clean (Must check the hole in the filler cap though).  To get home yesterday,  I had one side of the bonnet open for the last 15km or so, but it didn't improve the situation.
Out of curiosity, during the episode, I pulled the choke out a bit whilst trundling along at 40 kph - result, engine stopped and I rolled to a stop!  After a brief pause, she started without problem.
To Dave Mann, I don't have the flitch plates installed (Plates below the exhaust pipe),  also note that your RN has the expansion loop in the vertical plane.
I guess I ought to check the float level as noted on the Cornwall A7 site ???
My local club suggested insulated flexible fuel pipe - doesn't look right, but may offer a solution.
Bob

[Mark McKibbin]

Bob,

If the car stopped after you pulled the choke out a bit, it would seem that you do not have good flow from the tank so it's running too lean or your float level is too low.  Or maybe it's something else

[Steve Jones]

That's what I meant in my post above, Mark. It's fine looking at all the complicated and obscure issues but if the mixture's weak, the float level is too low and/or the ignition is retarded you're wasting your time. Get the basics right first before thinking about the more obscure. My experience of updraught Zeniths is that a mixture that is slightly over rich and a slightly increased tickover speed makes a significant difference.

Steve

[Chris Garner]

Concur with that Steve. Exactly what I do. Was out in both my bog standard '25 and '28 Chummys yesterday in 95F and both ran without problem - in fact they seemed to go even better ( high humidity?)