Anyone converting a car from a carburettor to fuel injection (EFI) might well find the need for a surge tank to prevent fuel starvation when running at a low fuel level or under hard cornering. Stock fuel tanks in older cars don’t have any kind of in built design to prevent this situation other than simple baffles, but how does it occur and what’s so different with fuel injection? The fuel pump in a car equipped with a carburettor pumps the fuel at quite low pressure and at a relatively slow speed from the tank to the carb. Should the fuel ever slosh away from the pickup pipe inside the tank uncovering it and allowing air to be drawn in by the pump, the engine will happily continue running regardless as a carburettor has it’s own in built reservoir of fuel in the float chamber. By contrast, an EFI pump runs at very high pressure and the fuel is circulated to the fuel rail and back very rapidly, so should the pickup become uncovered momentarily the pump could literally draw in so much air that it would purge all of the fuel from the entire system in a moment. Suddenly the injectors would be getting no fuel and the engine could even cut out. This is particularly risky with a turbo engine. A sudden lean mixture condition at speed could result in serious engine damage. So having established that a fuel surge tank is a good idea, how does the system work and how do we go about making and installing one? Read on….
When I got my Sunny Truck, it’s stock ride height was seriously sky high… much higher that any B110 saloon or coupe I have seen. Having been built in South Africa and intended for use on some of the countries rough terrain and unmade roads, this came as no surprise but for my purposes it was no good. I want it low! So far, the only thing I had done is to get the rear leaf springs de-cambered (flattened). This dropped the rear by around 50mm but didn’t really make it low so I plan to drop it further using some 50mm lowering blocks. Up front the stock suspension is like regular B110’s only sporting drum brakes in place of the more common discs. I needed a brake upgrade but nothing wild so I figured I’d just swap in B310 Sunny front struts which have larger discs than B110 saloons and coupes. To get it as low as I wanted but whilst retaining some ride quality, I decided to build some extra short struts. I chopped about 65mm out of the legs and converted them to adjustable coil-overs. I’m using some 185lb/in springs initially as I just happened to have a set already. These may be suitable but if not, at least they’ll give me some idea what poundage to go for. After having these parts sat around for the last 18 months, I’ve finally got them installed….
Here in the UK our F10’s are cursed with having a mere 988cc to pull them about (unless you own the “big block” 1171cc coupe). Why Datsun decided that Europe only needed an A10 when the US got A14’s I cannot begin to imagine. Maybe smog gear on US spec cars require the extra capacity to make up for the power loss?
My daily work horse is an F10 wagon (because nobody will steal it) which I decided was painfully slow, especially when loaded up with engines (no, I’m not joking) I decided to fit an A12 for a bit more go, but what I really wanted was an A14. The only source for a proper front wheel drive A14 was an N10 Cherry coupe (sold as a 310 in the US) which aren’t exactly common so I figured I’d try a RWD engine from a B310 Sunny (that’s a 210 in the US).