So we have an Eaton on the 4.2? Someone told me it was a Lysholm? I guess either way they are both positive displacement (roots) type blowers. If it is a Heaton, and it's 1.87L, then its a variation of the M112, which is what Ford used in their Terminator (just sold mine ). This would make sense since Ford owned Jag at the time. That being said, the M112 can take upwards of 16-17 lbs of boost before it starts to get maxed out and it becomes law of diminishing returns. At that point, most people who want more power go to a bigger displacement blower (Whipple, for example). This is why I say there is power left on the table running 10-11 psi stock. Even more if you want to port the blower and get bigger injectors, a bigger heat exchanger, yada, yada, yada...remember, LR has to protect their engines so they go way, way conservative. I bet the stock a/f curve goes pig rich over 4k to keep everything cool when in fact 11.5 start to finish is perfectly fine and actually maximizes efficiency.Originally Posted by avos
And I understand about blower efficiency and overspinning it...I'm saying for THIS specific application there there is more power to be had in the blown 4.2 because its making 400 hp which is NOT a lot for that displacement with a 1.87L roots blower on it @ 10-11 lbs. My 4.6 DOHC with the Eaton M112 (1.8L) blower, a 2.95" pulley and tune was upwards of 520 crank hp, and there was another 20 or so HP but I didn't want to bump the timing any more. That stock Eaton spins at ~12k in stock form, but with my setup it was close to 17k with no drop or diminished performance.
I do agree that a smaller pulley won't ALWAYS result in increased power, BUT...that is only if you're maxed out on the stock setup, which these RRS S/C's are nowhere near.