Quote:
Originally Posted by comptiger5000
Keep in mind, he's not using this for city driving. On the highway, auto with TCC locked vs manual doesn't make much difference, it's the overall gearing that counts.
As far as lugging it down to 1000 rpm, that's too low to have enough power to do much with in stock form. Plus, it may actually put him below the good part of the BSFC curve. To even think of playing down there, engine mods to increase low end torque are likely needed. In my Jeep, it starts dropping off pretty hard below about 1100 rpm, and my engine is a good bit bigger than his (5.9 liters).
I'd say he should shoot for somewhere in the 1300 - 1400 rpm range, 1500 was the absolute max. After a little research and math, with his stock AODE transmission, stock 215/70R15 or equivalent (26.8" tall) tires, and a 2.73 rear end gear, he will turn 1375 rpm at 60mph. That and aeromods could quite possibly get him very close to 40mpg.
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1000 rpm should be OK for BSFC, at least if Ford designs a decent engine. The closest on the wiki is a Toyota V6 that's at ~250g/kWh at 1000rpm and high load. Obviously if the Ford engine can't handle it then it's a moot point.
Anyway, according to the power calculator here an aeromodded crown vic w/ LRR tires would need ~17hp at 65mph. It makes ~225hp at 4800rpm, so at 1500 rpm it would make ~70hp assuming a fairly flat torque curve, so it would be at 1/4 load in that case. There's no engine that's anywhere near a decent level of efficiency at 1/4 load. Even at 1000rpm it would only be at ~1/3rd load, and to see decent efficiency we would need at least ~1/2 load IME.
I'm in complete agreement about there being a negligible difference between a locked up auto and a manual on the highway, but after LRR tires and aeromods I don't see any way to get the load high enough on a 4.6L engine so that it's operating relatively efficiently and can hit 40mpg, and w/o LRR tires/aero mods there's no way the car will hit 40mpg anyway.
