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Much myth and misinformation has been put about regarding different injectors being used to boost performance. The whole thing is quite complicated which is why people get away with talking so much garbage about the subject.
There are 2 sorts of injector fitted to the L series in the MG/Rover range. I think the freelander may have a different type again but I’ve been unable to verify this yet.
The earlier VP37 pump on the 2/4/600 Di’s uses 200bar injectors with a nozzle code of DSLA 145 P 446. The later VP30 pumps use a 210bar injector with a nozzle code of DSLA 145 P 870
Fitting injectors from a VP37 pumped car into a VP30 pump will give an immediate increase in power (and smoke!). Remapping the VP30 can reduce the smoke to tolerable levels and still retain a hefty performance increase. Be warned that most of the performance increase out of the box so to speak will come int he form of lots more low to mid range torque. This can over stress the clutch in some cases as it simply isn’t designed to handle that much torque and can give a fairly peaky torque curve, however most people regard the performance increase as worthwhile as it is so cheap to do.
Ok so what is the difference between the two injectors?
Well the first is the break pressure. Ok what is break pressure? Well it is the pressure at which the first stage of the fuel injection starts at. “First stage?” I hear you cry. Yes our old mechanical injection pumps have two stages of fuel injection. Think of it like this: The first (primary) injection stage lights the fire, and controls diesel knock. The second (secondary) stage gives most of the power. The ECU only knows when the primary stage opens (via the wire on number 1 injector), and so essentially the lower the break pressure the more retarded the injection timing becomes. It is very complicated to explain so please just take my word for it on this fact for now. This is one of the reasons that fitting the 200bar injectors to the later cars results in smoke.
The second and very important factor is that the nozzle holes in the VP37 injectors are larger and so flow more fuel through them than the VP30 injectors. This is why you get a big performance hike when fitting them to a later VP30 car, and also part of the reason you get smoke too, (bigger nozzles atomise the fuel less well and so give more smoke).
Ok so what about these “wingy” injectors I’ve heard about. Well they actually come from someone else (Diesel Bob). Details on these are very sketchy at the moment as he keeps them a closely guarded secret. However they work in the same way. They have bigger holes in the nozzle and so give more poke and more smoke!