Here's a thought I had today while driving home for lunch. Why donesn't anyone make large displacement (6-7 liter), super-long stroke, turbocharged in-line 6 cyl gas engine that's cammed & designed to run in the 1000-3000rpms range (i.e. similar to a diesel). It could have compression in the 8:1 range to handle 10-15lbs of boost and still run comfortable on mid-grade pump gas. In my logical theory, having a long stroke and high displacement, it would produce lots of torque right where you need it for towing, and having a diesel-like cam profile, revving that much rotating mass with that must stroke shouldn't be a concern. The ONLY real difference between a gas engine built like that, and a comparable diesel (i.e. Cummins) would be simply the compression ratio difference. Everyone always says gas engines just don't have the torque down low, you gotta rev them to get the power. Well yeah, thats true, becuase they're built to make peak torque and power in the 3000-5500rpm range. The V10 idea Ford has and Dodge had is along the same lines as mine, but only using 10 "smaller" cyls instead of 6 larger ones to get the displacement. It's just me thinking outloud.. what do all of you think?
Mack made a gas powered rig NA not turbo'd that used the same I-6 block as their I-6 Maxidyne diesel engine in the late '60s/ early '70s. I don't remeber the specs but think it was in the 670 CI range. In the '50s-'60s there were big inch gas rigs that competed with diesels but lousy fuel mileage killed them off. But back then a 300+ hp diesel in a big rig was a big deal. Now with stock 600hp/ 2000+ torque big rig diesels there's no way a gas rig could compete.
Large displacement gassers have been done, and just didnt cut it. GM used to make a 478 cid V-6, and also a 702 cid "Twin 6" V-12. While these were workhorses no doubt, they just couldnt compete with the diesels, and were fased out.
That's the answer. Diesel is simply a much more efficient IC engine. More power per unit fuel is where it's at.
High CR is one of the main reasons for the higher efficiency, and the open intake certainly can be a plus, particularly for turbo. But "much bigger factors" relative to what?
Ahh, I see I wasn't clear. Yes, the BTU potential is higher, but when I said "Diesel is simply a much more efficient IC engine", I meant the over all package (as an IC engine) including the engine design itself (compression firing and all) along with it's ability to run the fuel. The "power per unit fuel" I guess is what caused the confusion though. But I was not really talking about BTUs in the fuel, but rather that the Diesel engine produces more power per unit of fuel. Sorry for the confusion.
These are all very good points, and it now makes sense to me why they don't make them any more. Thanks for the answers
Probably cause they had the tall block V8's! Now I would like to see what a tall block would do if it was built. Most people write them off as boat ancors but thats cause they have never used them or they think they should turn higher RPM's like a small block.
