Sold my Vitesse radiator on ebay yesterday for £65, which means my reconditioned straight 6, gearbox and chassis (rotten though it is) have cost me the grand total of thirty three quid, and if I get four pounds each for the Spitfire wheels it came with it'll have cost me just over a tenner.
I had a lovely chat about all things engineering with the chap who collected it, as you do. He was particularly interested in the water injection system that I'm adding to the engine and has asked me to provide him with some more information, so, I thought why not share it with the madabout Sammio community as well?
But why do I want to add water injection? The answer is because I want to run an old engine on modern fuel. I have a 2 litre Vitesse lump going into my Sammio, and here's what the Vitesse handbook says about fuel:
The Vitesse 2-litre engine is designed to operate on fuels having a minimum octane of 100 (RON). Using fuel of this, or higher rating, the static ignition timing should be 13 degrees B.T.D.C.
Where such fuels are not available and if, therefore, it becomes necessary to operate on fuels of lower or unknown rating, the static ignition timing must be retarded just suficiently to prevent audible detonation (pinking) under all operating conditions. Failure to do so may result in serious damage to the engine.
Using fuel having a minimum rating of 97 (RON), the static ignition timing should be retarded to 7 degrees B.T.D.C. Because loss of engine power and efficiency will result from retarding the ignition, it is strongly recommended that fuel having a minimum octane rating of 100 (RON) is used whenever available and that the static ignition timing is set accordingly.
Now, standard unleaded is 95 (RON) and super unleaded is 97 (and mightily expensive) meaning that even with super unleaded the ignition will have to be retarded by 6 degrees or risk having it detonate itself to destruction.
And if anyone is unfamiliar with what the octane rating means, the higher the number the more resistant it is to compression ignition allowing a higher compression ratio and more aggressive ignition advance giving more power at faster crank speeds with better economy across the board, a win-win situation.
By introducing a fine mist of water into the intake charge you effectively increase the octane rating of the fuel/air mix. For a more detailed technical description follow link the here:
http://www.turbomirage.com/water.html
Now, although these days the focus for water injection is on the highly tuned turbo brigade it still works wonders on a normally aspirated engine and the setup described in that web site is pretty much what mine will have:
A water tank; a high pressure pump; a vacuum actuated switch (sited outside the throttle butterflies so it's triggered when the engine is under load); a solenoid valve; and a fogger nozzle, all linked together with high pressure pipe. I've sourced all the parts I need from the internet for a total of less than £120.
A simpler setup is possible, however, which consists solely of a water tank and some copper capillary tube: The water tank needs to be sited below the level of the carburettor(s) (so the water doesn't gravity feed into the intake) but higher than the exhaust down-pipe, while the capillary tube is routed from the underneath of the tank, around the exhaust down-pipe a dozen or so times and then up into the bottom of the air filter housing inboard of the filter. As soon as the exhaust gets hot, the water in the capillary boils and the steam is forced up into the air filter where it is drawn into the intake charge. Nobody knows why, but steam works just as well as a fine mist of water giving significant gains in power and economy. Simple.
With any water injection system it's important to use distilled water so it doesn't fur up and with the pump and nozzle system it's also wise to add some methanol, both to stop the water freezing and to inhibit bacteria growth. I'm planning to run about a 5 to 1 mix. It's also worth mentioning that this won't allow you to run a leaded cylinder head on unleaded as the valve seats will still wear out if they're not the hardened type.
Et voila! Or, as they say in France, there you 'ave eet. DIY water injection for beginners, if you dare...