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Old 17th January 2019, 08:51
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Mister Towed Mister Towed is offline
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That's a great article, Mick, thanks for sharing it. It explains exactly why I fitted it - to allow the Vitesse engine, designed to take 100 octane (5-star) fuel, to run on 95 Octane modern unleaded without running in to detonation issues (pinking, for those old enough to remember that).

I tried various ratios of water to methanol and settled on a 10% methanol solution. The positive effects mostly come from the water anyway, so you could run 100% water injection, but some methanol still really needs to be added as it stops bacteria growing in the water and clogging up the pipes and nozzles.

The simplest form of water injection is just a water tank located above the exhaust downpipe but below the intake manifold, with a gravity fed copper capillary tube running from the water tank wound a dozen or so times around the exhaust downpipe. That is then connected to the air intake tract on the throttle side of any filters.

With the engine running, once the exhaust heats up, the water in the capillary that's wound round it boils. The steam created can't go back towards the tank because of the flow of cold water, so it exits the capillary into the intake tract, where it is sucked into the engine along with the incoming air.

As the wikipedia article explains, that has the effect of cooling the inlet charge and increasing its density, which can give around a 30% increase in power on a highly tuned engine (less so on a standard engine). Steam has been proven to have exactly the same effect as cold water in doing this, btw, and there are a host of side-benefits with no down-side.

My original plan on fitting it to my Spyder was to modify the engine, raising the compression ratio and fitting a wild cam to make best use of the benefits of water injection, but, in reality, around 100hp was quite enough to enjoy a very light car on the road anyway.

I can't say exactly how much extra power the system gave my mk1 Vitesse engine as the day I put it on the dyno to check was the day the system decided to clog itself up and stop working for the first time. That was ultimately down to the very fine nozzle needed on a low powered engine - I'd run the calculations to get the correct volume of water in the inlet charge and too much can cause a hydraulic lock in the engine which is likely to either bend the con rod, smash the crank out through the sump or blow the cylinder head off.

Anyway, that really sums up the joy of self-build cars - building and fitting a methanol/water injection system not because it needed it but just because I could.

Last edited by Mister Towed; 17th January 2019 at 08:54..
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