My AX GT !
I've spiced it up with a dash of lens-flare.
Under the bonnet a bunch of treats awaits unsuspecting eyes…..
Interesting details I'm sure…..and how to make your car go even faster.
It's almost impossible to get hold of jets for the Solex Z2 carb, and this is because it's been found that the carb gasket face warps with heat. This causes poor carburation, as air is drawn in through the gap in the flange rather than through your venturis. This problem is easily rectified using some abrasive paper, a nice flat block of metal and a feeler guage. The problem of getting bits for the carb remains. One way is to get hold of a second hand carb (mine cost about £60), and use it for spares. It will usually look like a dog has emptied it's bowels in it.
Widening out jets
The fuel jet constricts the flow of fuel which enters the air stream. The greater the pressure difference across the jet, the more fuel flows, and carburettors meter fuel volumetrically. Hence all the arguments about the weather and cold air etc. The greatest demand for fuel will usually be when your foot is flat on the floor, waving in your rear view mirror at a knackered out Ford XR2i blowing smoke all over the road. In my opinion, the best mixture for optimum power output is between 13:1 and 12:1 air:fuel, and this can be achieved by progressively widening out the jets. The problem is then, that under part load conditions the mixture will invariably be too rich. Try opening up an air corrector jet, or if you're brave start drilling holes near the top of your emulsion tube.
The whole point of re-jetting a carb is usually to get more power out of your engine. You've thrown away your crappy paper air filter, and your stupid exhaust manifold, and the increased air throughput means you're now running too weak (nearly always). So you want to widen out your fuel jets. Figure 1 shows the cross section of a typical fuel jet. The two ways of increasing the flow of fuel throught the jet are either to get a fine drill (ie. For drilling holes in PCBs) and try to drill out the constriction in the jet (a). Alternatively use a fine reamer. The other way of doing it is to reduce the length of the constriction (b) using a larger drill bit. This way is much easier but has less effect. If you go too far, you can either invest in another second hand carb, or solder it up and try again.
Figure 1. Cross section of typical fuel jet.
The volume of fuel flowing though a jet per unit time can be expressed using Poiseuille's law:
where r and l are the radius and length of the restriction respectively, and DP is the pressure difference across the jet. This could probably be worked out somehow, but I haven't thought about it yet. The viscosity h of the fuel would vary with temperature, which is yet another reason why carburettors work differently when they get too hot/cold For Octane and Benzene for example, h is about 0.5Pa.s at room temperature, and drops to around 0.3 at 80C.
It's easy to see though that opening up the restriction in the jet is tricky because V is proportional to r4, and a small mistake will radically change your mixture so be careful !. Go here to see a bit of probably really dodgy maths to predict fuel jet size.
Removing the choke
The choke flap in a Solex Z2 sits on a 1/4" spindle right across the primary venturi. It is slightly offset, to minimize the disturbance of air into the auxiliary venturi where the fuel is picked up. However, you don't need a choke, not really. So take it out. Just unscrew the butterfly from the spindle (don't drop the screws down the inlet manifold, unless you want to take the head off), slide it out, and take out the choke spindle. Now you're left with two gaping holes in the side of your carb. Get some 1/4" plastic hole plugs to fill them up. You should now find you're running a bit leaner, which means you can add yet more fuel. If your accelerator pump works (if it doesn't, best fix it) then starting from cold, even in snow is no problem. Leaving the fast idle cam in position will allow you to stop the engine from stalling when it's cold with the choke.
ICE
Why bother weighing your car down with a load of junk electronics in an acoustically flawed environment ? Just think how much money you could have saved if you didn't buy all that stuff. Just think what you could have bought with it to make your car go even faster. The sweetest music of all is the sound of your beautiful engine screaming it's nuts off in your ear holes.
and I couldn't even be bothered to wash it !
Disclaimer.
The author assumes no responsibilty whatsoever for any damage, intentional or otherwise, incurred on any motor vehicle, resulting from the material contained herein.
(If you break your car, it's your fault. Not mine.)
