26-12-2012, 09:02 PM
Maybe I'm on the blob, but it's gotten boring hearing the same stuff...
There's multiple reasons why you might want an 11mm OVER a 9mm pump...
With injection pumps there's essentially TWO ways of increasing the injection amount, lengthen the injection duratiion (i.e. open the collar more...) or inject more fuel in a given duration... When you get to the point where you're spinning the engine at 5000rpm, a 9mm plunger simply cannot provide SHORT injection lengths, an 11mm pump will do this MUCH better, reducing exhaust gas temperatures and the engine will rev and respond MUCH better etc... The biggest disadvantage is the fact that it does play havoc with the timing system...
HOWEVER, keeping a 9mm pump also means that you are massively restricted by the amount of fuel you can run due to other parts inside the pump, you cannot just assume you can keep winding the max fuel screw further and further, because at the end of the day, the amount the throttle moves will only allow for so much fuel, even if you carry on winding the max fuel screw, since a certain part of the pump doesn't move enough... I'll leave you figure out what it is, but it's not easy to simply change this part for a "better" one, it's trial and error OR modifying said part...
People just seem to think there's NO thought gone into why we fit 11mm heads and it's just an easy option and it blows chronic coal etc... It's simply not the case, go have a look at my dyno video and there's NO smoke whatsoever at 175HP+...
There's multiple reasons why you might want an 11mm OVER a 9mm pump...
With injection pumps there's essentially TWO ways of increasing the injection amount, lengthen the injection duratiion (i.e. open the collar more...) or inject more fuel in a given duration... When you get to the point where you're spinning the engine at 5000rpm, a 9mm plunger simply cannot provide SHORT injection lengths, an 11mm pump will do this MUCH better, reducing exhaust gas temperatures and the engine will rev and respond MUCH better etc... The biggest disadvantage is the fact that it does play havoc with the timing system...
HOWEVER, keeping a 9mm pump also means that you are massively restricted by the amount of fuel you can run due to other parts inside the pump, you cannot just assume you can keep winding the max fuel screw further and further, because at the end of the day, the amount the throttle moves will only allow for so much fuel, even if you carry on winding the max fuel screw, since a certain part of the pump doesn't move enough... I'll leave you figure out what it is, but it's not easy to simply change this part for a "better" one, it's trial and error OR modifying said part...
People just seem to think there's NO thought gone into why we fit 11mm heads and it's just an easy option and it blows chronic coal etc... It's simply not the case, go have a look at my dyno video and there's NO smoke whatsoever at 175HP+...
