Modern Fuel Injection for the pre-electronic era! Brilliant!


Or… a drip tap into a venturi controlled by a butterfly…that had occasional conflagration issues? Not so brilliant.

Which is it? You be the judge.

Walter Hartley ‘Wal’ Phillips was born in Tottenham England in 1908 and became a professional Speedway racer, appearing in the very first Speedway World Final in 1936 (placing an unlucky 13th) the same year his racing career was ended by a broken leg.

Phillips’ uncle was a development engineer for JAP (renowned for their Speedway engines), and Wal learned plenty from him and also from his own experiments in power and speed. He spent some years developing this mechanical fuel injector, and yes it is truly an injector since the fuel flow is delivered by pressure (gravity) rather than vacuum. Of course, being AHRMA racers with mechanical brains, you’re saying to yourself “but without a pump, the pressure would be regulated by the vertical distance between the tank and injector and the amount of fuel in the tank, and the volume decreases constantly.” Which is why the most efficient use of the Wal-Phillips incorporates a float that is mounted below the tank and above the injector. Of course, if there’s not much space between the bottom of the tank and the injector, you’ll lose pressure, which means a lean mixture or big huge fuel droplets that won’t effectively combust. And of course since it’s gravity fed and gravity has a bad habit of continuing operation after you’ve shut off the bike, you needed to either fit a vacuum-type petcock or unfailingly remember to turn the fuel off every time you shut the bike down – or that whole nasty conflagration thing may occur upon restart.

Seems like fitting a fuel pump would have been the first order of business, but hey, I’m just a blonde chick who still grabs a 12mm socket when the bolt is an 8, so what do I know.

Strangely, the Wal Phillips injector unit was quickly adapted for use on scooters and became quite a popular modification back in the day. Here’s a quick excerpt from Scooter World 1966 “Something for nothing – that’s what everybody would like – a couple of magic words and suddenly your bike develops another ten brake horse power! This never happens and so you have to look around and decide just where your money is best spent. The answer is to improve the engine, but this usually means buying very expensive parts and also spending long weekends in stripdowns and testing. But we have found an item that you can buy and bolt on which will give a reasonable increase in performance, and that is a Wal Phillips fuel injector… We had a pair of Lambrettas on test this month and this was an opportunity to try out a new injector designed specially for scooters. ”

Results did show some nice increases, 1.1 seconds faster from 0-30, and 2.5 seconds faster at 0-50 with a maximum speed gain of 9mph (I must say, 70mph has to feel darned fast on a Lambretta).

If you’re interested in more reading on the subject or maybe trying a Wal Phillips on your own little mod scooter, here’s a few good sources:…/walphillips.html