M30 - low efficiency; why?

[Jeff N.]

Anyone have an answer as to why the M30 is so much less efficient (or so it seems) than other engines?

Maybe it's just me...as I think about it.

E34's that tend to get better mileage:

M60 - 3 liter; smaller engine
M52 - 2.5 liter; smaller engine
M20 - 2.5 liter; smaller engine

E34's that tend to get similar or worse mileage

M60 - 4 liter; bigger engine

Of course, a M30 car tends to be heavier than the smaller engine E34s. That counts for something.

A M30 car also is running older technology than most with 2 valves per cylinder, static cam timing and an older style fuel management system. What does that cost you in efficiency?

Just curious as to the real reasons that the beloved 3.5L engine seems to be such the gas hog. Or...maybe it's just perception.

[Jay 535i]

I think you answered your own question: older technology and simpler mechanics.

The M30 doesn't have all the fancy stuff the newer engines have to squeeze the most out of every gallon of fuel. It makes up for that in displacement, but that means poor economy.

[ryan roopnarine]

Of course, a M30 car tends to be heavier than the smaller engine E34s. That counts for something.

.

a m50 engine weighs about 194 kg, a m60 engine weighs about 215kg. i doubt that the inline engine that is the m30 would weigh more than the m60 with two banks of cylinders....the m20 engined e34 has basically the same autotrans. diffs, trunk, doors, some driveshafts can be swapped between some. im curious as to why you'd feel the m30 would be heavier than the 3l m60....im sure you'd need a lot of wood trim and backseat refridgerators to make a difference

[Bill R.]

The v8 has a aluminum block, the m30 has an iron block,hence its long life
Some of the reasons Jeff, are that the v8 has a 5 main bearing crank in the 3.0 versus a 7 main bearing crank in the m30, some more drag there with the 7 main, not much but every penny counts here... 2 valve motors can be just as fuel conserving as 4 valve so you can't always go by that. The v8 is at least a point higher on the compression ration which makes a big difference, it has a much better motronic too which allows the timing to advance as much as possible at all times which also helps mileage alot. It has true sequential injection which makes a difference too, Short skirt pistons make a difference in friction, smaller valve stems improve flow in the ports along with a different head design. Lower friction ring designs, Better exhaust design with the factory tubing headers. The intake manifold being plastic and a much smoother internal design makes a difference too i'm sure.
Even with all that I don't see that much difference in the 3.0 and the m30 s.5 considering how much more technology went into it.. The m30's compare fuel mileage wise to most of the maxima's i work on and they are quite a bit lighter with variable cam timing, knock sensors etc..

a m50 engine weighs about 194 kg, a m60 engine weighs about 215kg. i doubt that the inline engine that is the m30 would weigh more than the m60 with two banks of cylinders....the m20 engined e34 has basically the same autotrans. diffs, trunk, doors, some driveshafts can be swapped between some. im curious as to why you'd feel the m30 would be heavier than the 3l m60....im sure you'd need a lot of wood trim and backseat refridgerators to make a difference

[Dan in NZ]

What is the difference in the output between M60 3.0 and M30 3.5? I would imagine they would be about the same? Mabe even a touch more? If so, you're getting a lot more bang for your fuel bucks. Gotta be a good thing now that it's costing upwards of $120 to fill the tank!

[winfred]

i think the 3l m60 is rated around 20 more then the 3.5l m30 but my 535 will chew up and spit out a 530, done it a few times and still pulling away at 100

What is the difference in the output between M60 3.0 and M30 3.5? I would imagine they would be about the same? Mabe even a touch more? If so, you're getting a lot more bang for your fuel bucks. Gotta be a good thing now that it's costing upwards of $120 to fill the tank!

[Derek A.]

7 more horsepower - but the m30 makes more torque than the m62 3.0

[Bill R.]

535 but torque is higher on the 535 and the torque peak on the 535 is at 4000 rpm which means more grunt on the bottom versus the 4500 rpm torque peak on the 530, I can't find my hp torque curve for the m30 but i remember that is was much flatter than the m60

i think the 3l m60 is rated around 20 more then the 3.5l m30 but my 535 will chew up and spit out a 530, done it a few times and still pulling away at 100

[winfred]

hmmm torque, how bout 440 ft lb in my new old cummins (shame the truck is around 3 tons however a 7-8000 lb 4wd juiced up with about $1000 in power mods will do 13 seconds in the 1/4 ) if for no other reason i like it is the noise at idle, the new HPCR 600 motor is too quiet

535 but torque is higher on the 535 and the torque peak on the 535 is at 4000 rpm which means more grunt on the bottom versus the 4500 rpm torque peak on the 530, I can't find my hp torque curve for the m30 but i remember that is was much flatter than the m60

[Zeuk in Oz]

if for no other reason i like it is the noise at idle

Amen to that !
My F250 7.3 litre powerstroke's idle should be sold on CD it is so nice !
Ah.......the simple things in life.