Help!
GENERAL
E10 fuel concerns
Q With this E10 fuel now for sale, problems may arise with classic cars – I run a 2003 MG TF and a 1981 Triumph TR7. My local garage only do E10, so to get E5, would need to travel about eight miles each way, which defeats the purpose. There are a number of additives available, which will need to be used and comments are positive. The only problem is in the coming winter, I like many, will lay-up cars.
We are told the need to drain, fuel completely, which to be honest is a bit of a faff, none of my tanks have a drain. And obviously floats in my SU6 carbs on my TR7 may be affected. I usually start the engines once a week in storage, so do you think additive added to E10 would suffice? If not, it’s going to cause problems.
Ray Dullick
A The E10 fuel situation is causing as much concern as when the lead was removed from petrol. It will only affect the owners of older vehicles. Even though it’s an eight mile journey it would be best to fill the tank with the still available E5. All Super Unleaded is E5 and although this is a little more expensive, it should give a better fuel economy. One other side effect of the new E10 fuel that many will notice is that although better for the environment, the mpg figures will decrease and more fuel will be used.
The problems with E10 fuel are that the ethanol in the fuel is hygroscopic, and is a solvent that can seriously affect fuel lines and cause corrosion in the system. On a classic vehicle with a tin float in the carburettor it will eat into the solder and cause the float to fail. Additives are good to a point, but as they do not remove the ethanol. They cannot off put the effects of the fuel totally. Whilst many fuel additive’s do address the hygroscopic properties and to some extent prevent the moisture retention, they will not address the problems of the solvent.
When storing a vehicle, the tank should either be filled to the brim or totally drained – this should address the issue of moisture retention. As you say draining the tank is not an easy option, and in any case the fuel would still need to be stored, or used in another vehicle. Filling the tank and sealing the cap will negate the opportunity of moisture in the air, seeping into the fuel.
I will also add that magic pellets added into the tank will not be a cure for the situation, and I would dismiss any such claims, as to date I have seen no such evidence that a tin pellet would be of any benefit.
So to sum up, keep your tank topped-up with fuel and you will unfortunately need to obtain the E5 fuel to protect your vehicles, and additives such as this one www.sta-bil.co.uk will help. I would still recommend avoiding the extra ethanol fuel if possible, and continue using the E5.
GENERAL
LED trailer lights
Q I have recently purchased a trailer fitted with LED lights. These work fine but do not activate the dash warning light when the indicators are on. I have other trailers with a lighting board (filament bulbs) and it works OK with these. I have fitting 6 ohm/50 watt load resistors to the trailer indicator lights. This makes the dash warning lamp work but the indicators on the trailer do not work. The towing vehicle is a 2002 Hyundai Santa Fe with normal filament bulbs.
I have two questions:
► Is it a legal requirement to have a dash warning (visual or audible)?
► What size load resistor should I fit? Ohms law works out at 6.8 ohms for a 21 watt bulb. Do I need a 25 watt 6 ohm resistor?
Nick Lett
A The construction and use regulations specify that there should be some form of alert to let the driver know trailer indicators are working correctly such as a buzzer or light. Either is acceptable and many bypass systems rely on a buzzer in the rear of the vehicle which allows for easier wiring in of the trailer socket. The formula to work out the resistor required will need to consider the LED voltage and LED forward current. The forward current is the voltage required to make the LED light and this varies according to the colour of the LED. White and blue are typically 3.4V, whilst the red, green and orange LEDs have a forward voltage of 2V.
It will also need to include the number of LEDs connected – if the trailer board has multiple LEDs in the circuit this will affect the calculation. The formula is Resistor = (Battery Voltage – LED voltage)/desired LED current.
Using the 12V power supply and the desired LED current of 10mA, the formula for a red LED would be: Resistor = (12-2)/0.010 – this makes the resistor value 1000 ohms. The wattage rating would also need to be calculated and the formula for this is to multiply the voltage drop through the resistor by the current flowing into it. So the above would be: (12-2) x 010 = 0.1 using the next available resistance wattage of a quarter.
These calculations are for ensuring the LED operates when connected to a 12V supply, not to ensure it gives the correct load to allow the vehicle on-board systems to sense the presence of the trailer board. This calculation can be tricky without knowing all the specifications but the calculations have been done by various companies and a unit is available which is a 12V 6 ohm load resistor with a maximum power consumption of 50W.
Owners have found that when wiring a resistor directly into the circuit of the trailer board the recommended resistor is 120 ohm 1W (5% tolerance) – this is colour-coded brown, red, brown, gold.
