Alternator bypass & engine preheater mod

[paulgato]

View of plug and socket next...

Now I know what you're going to say: how can I possibly use a bright blue mains cable with a black car? What was I thinking!? Well the pre-heater came with a blue cable. I am going to make up a black cable, and use that on the driveway. The blue cable I shall keep in the car, together with an extension lead and an RCD adapter, so I can plug in if I'm away from home.

[paulgato]

Next, under-the-bonnet views...

The front junction box is loosely tucked in between the headlight and the washer reservoir. It doesn't move about and it's of lightweight plastic construction with rounded corners so it won't damage anything. The cables in that viscinity are not clipped to anything so the box can be lifted well clear for access.

I used waterproof (IP67) electrical junction boxes and cable glands. They were quite cheap. As a temporary measure, I fitted an ON/OFF rocker switch to the side of the rear junction box above the pre-heater. This means I have to go out an hour before driving off and lift the bonnet to switch on the pre-heater. That's not really hard work, but I do intend to replace that switch with a remote switching device that comes with a key-fob actuator, so I can switch the pre-heater on from inside the house. That rear junction box MAY be JUST big enough to accomodate the remote switching unit, but I'll probably have to find a slightly larger one.

The rear junction box is attached to an existing bracket on the bulkhead/firewall, as is the support bracket for the heater itself. (And yes, I made that support bracket from a length of 22mm copper pipe, beaten flat, bent and drilled! It works well!) The pump is light and is supported solely by the hoses themselves. The pump is a 12v one and came with a little mains adapter, which is tucked in behind, below and to the right of the rear junction box. There is a green/yellow mains earth connection between the pre-heater can and a ring connector bolted to the bracket on the firewall.

One would normally fit the pump and pre-heater can on the return from the car's heater matrix, but the layout of the hoses would not permit that as the return stub on the engine was pointing upwards, which would have resulted in a 'high loop' of hose, where an airlock could potentially have formed. Consequently, the pump and pre-heater are on the flow hose to the heater matrix, and everything runs smoothly uphill away from the pre-heater can, both back through the pump to the engine and forwards on to the matrix. Hopefully this will ensure that air is always going to be released out of the pre-heater can.

The pre-heater can is angled slightly backwards so the inlet and outlet hose connectors are pointing slightly upwards away from the pre-heater. (A 2kw heater element will burn out pretty quickly if exposed to air! The main thing you can get wrong when installing a coolant heater is to allow an airlock or a vapour lock to occur. This was one reason for choosing the 2kw model instead of the more usual 3kw model: to allow a bit more margin for error!)

Getting that heater can and pump fitted correctly was by far the hardest part of this installation. It took me a full day and a fair bit of trial and error before I had it securely fitted where the pipes and hoses ran correctly and nothing was interfering with anything else back there. (No cables, hoses or anything else at risk of chafing or overheating on anything.)

By the way the pre-heater is made by a UK company called Kenlowe. Very helpful people. Not cheap though. Their web site is truly awful, way out of date, and only shows their older heaters. But for what it's worth, here's the URL...

KENLOWE

As you can see, the battery charger is tucked in beside the washer reservoir and cable-tied in position. The charger is a CTEK MXS 10. It has no fan and is waterproof to IP65 standard, so I am not worried about it getting splashed when I'm filling the reservoir. Likewise with the junction box - that's totally waterproof. The charger has a specific AGM setting, and a remote temperature sensor, so alters its voltage according to the temperature in the viscinity of the battery. Without the temperature compensation there would be a risk that the battery could be undercharged in winter, and worse, that it could be drastically overcharged in the summer if the sun is beating down on the bonnet.

[Oh, ha ha - in this first photo you can just see the little red bullet connector behind the alternator, which is where I disconnect/reconnect my alternator field wire. Eventually I will run a pair of wires from these connectors to a switch on the dash.]

[paulgato]

That volt meter is backlit, but is not as bright as it looks in the photo. At present it is just connected via the cigarette lighter socket. At some point I'll wire it in permanently. It is large enough that I can read it clearly through the rear window, which turns out to be useful, as I can tell from the voltage roughly what the state of charge is (whether it is trickle charging or whether it is still bulk charging.)

You will notice the spare charged battery in the passenger foot well. I'll carry that around for a while yet, until I'm fully confident of how deeply I can discharge the main battery. The main battery is a 90Ah AGM battery by the way. It is heavy, and was the biggest I could fit in the existing battery tray. AGM batteries can be safely discharged and recharged by at least 50% daily without ill effect. The battery came with a no-quibble 4 year warranty. I was quite up-front with the seller about what I was going to do with the battery and he said, "Yup, that's a 4-year no-quibble warranty. If it fails within 4 years we'll collect the old one and give you a new one at no charge."

Eventually, I will run an extra cable through a grommet in the firewall in the passenger footwell and fit a mains socket there, so I can plug in a 1kw fan heater to run in parallel with the pre-heater to defrost windscreens on cold mornings.

[NachtRitter]

Very nice; thank you for the pics. Your estate looks to be in pretty good shape for its age.

[paulgato]

I just installed the radio-controlled switch unit. I won't bother posting a pic as it's dark now, and anyway the installation is a bit temporary as I want to install the receiver unit in a waterproof box when I can get one the right size. But the connection method will remain the same, so if you refer to the above pictures, the remote switch unit is connected to the rear junction box, in place of the temporary rocker switch, via a short 3-core cable and waterproof gland seal. The three cores needed are 240v live and neutral to run the unit, and a switched live return to the existing junction box to fire up the pre-heater and whatever else I eventually switch on at the same time (e.g. a socket in the cabin for a fan heater to defrost the windscreen, and/or perhaps a 250w oil pan heater.)

Anyway, it works. I now don't need to open the bonnet every time I switch the pre-heater on or off, and I can switch it on from inside the house. The remote fob seems to work in most places in the house, and certainly anywhere near a window I can guarantee it will switch the pre-heater on or off. The remote has two buttons, rather like a car key fob, so one button for ON and another button for OFF. It would nice to have a loud BEEEP from the car to confirm it has switched on, but it seems to be pretty reliable. And yes my friends, I can indeed switch on the engine preheater from the comfort of my bed (he he!) and by the time I've got up and got myself ready for work, the car is ready too. :-)

The remote was quite cheap. It's this unit here...

http://www.amazon.co.uk/Channel-Wire...=safari+drives

That's it. The mod is done essentially. Winter is almost over it seems (17 degrees C today! Very unusual for early March) so I won't bother arranging the cabin fan heater until later in the year, as that is only of use in the frost.

Now I'll see how this all improves mpg. I'm fairly convinced that for the purposes of improving mpg I only need to run the preheater for 30 minutes or so - to get the coolant temperature to 50 degrees or so. It will be worth doing that even in the summer. At 25 or 30 degrees ambient it will only take 10 or 15 minutes at 2kw to get up to 50 degrees C, but starting the engine and driving off at 50C rather than 25C will make a big difference in mpg over the first few miles.

I will know more the next time I fill up the tank, but since I did the 'alternator delete' mod and now the pre-heater mod, my overall average mpg, as shown by the (7% optimistic?) VW dash display has gone up considerably. I topped up the tank and zeroed the mpg display just after installing the battery charger and unplugging the alternator, and I have done 500 miles since then: all short journies in the local area, about half for work and half not. The overall average is showing as 91.5mpg Imperial and it's still rising. A month ago I was struggling to maintain an overall displayed average of 75mpg. Even in the heat of last summer when my mpg peaked, I was bragging about averaging a displayed 83mpg. 91.5mpg in winter, albeit a rather mild and wet winter, is encouraging. I shall wait to see what the filling station pump tells me, although I may be waiting a while as the fuel gauge is still showing more than 3/4 full!

[Update: I finally got the remote control receiver/relay unit fitted into another of those exact same waterproof junction boxes and the box tucked away just nicely behind the air filter housing. Putting the receiver in a box enabled me to stretch out its little coiled arial so it is now about 3 inches long rather than half an inch long. The remotes now work MUCH more reliably from inside the house, and I don't have to worry about being near a window. I have one remote by my bed and one on my keyring. Great geek-toys these radio-controlled switches!]

[focus1.6uk]

I'm following your thread with interest- my diesel takes a long time to get up to temperature on cold days too.

Am I right in thinking the silver canister is the preheater and the black component (with the Kenlowe sticker) the circulating pump?

Also, how much was the Kenlowe kit, roughly?

Thanks!

[paulgato]

Yes, focus1.6uk, the silver cannister is the heater and the small black thing is the pump.

Ah yes, the cost. It was expensive. About £300. The Kenlowe unit is good, and I appreciate having tech support from people just down the road, but to be honest it cost too much and if I were doing it again I would look at using a stick-on oil sump heater instead. As I say, the mpg hit of a cold engine seems to me to apply mainly to temperatures below about 50 degrees C, and a sump heater should lift the temperature out of that very inefficient zone OK, and with less power consumed.

[focus1.6uk]

Thanks for the reply, that does seem expensive! I think I'll go down the oil pan heater route when I get some free time.

Ian

[fearone]

Thinking out aloud here...

How about using a cloth iron as a budget, powerful, adjustable temp, sump heater?

After all, this is what ecomodding is all about!

[redpoint5]

I feel like I'm on dial-up whenever I visit this thread and the pictures begin loading line by line.