S65 engine weight - and some surprises!

[CanAutM3]

Originally Posted by xfirer1guy

So Pressure = Force/Area. Rearranged F = PA => Force is directly PROPORTIONAL to area, or pi*(Bore/2)^2.

And your point is ?

That is pretty much what I said in my previous post...

[the_road_less_traveled]

Originally Posted by CanAutM3

And your point is ?

That is pretty much what I said in my previous post...

Ummmm... I'm confused. You realize you wrote an equation agreeing with my agrument, but you disagree?!

F=PA is all you need to understand to settle this argument. How do you not understand that A in the equation is BORE? Bore is indeed a parameter used to determine engine torque.

[CanAutM3]

Originally Posted by xfirer1guy

Ummmm... I'm confused. You realize you wrote an equation agreeing with my agrument, but you disagree?!

F=PA is all you need to understand to settle this argument. How do you not understand that A in the equation is BORE? Bore is indeed a parameter used to determine engine torque.

I'm also not following you. Let me attempt to re-explain my point:

If you increase stroke only, you increase torque. In the same manner, if you increase bore only, you also increase torque.

Both of these are the resultant of an increased displacement. So yes, a bigger engine is able to produce more torque, no rocket science here.

However, for a given displacement, altering the bore and stroke relationship has no geometrical effect on the torque produced.

[Someone?]

Are you two^ serious? What the Hell? you going to have 10 pages of this BS?

[CanAutM3]

Originally Posted by ibmike

Are you two^ serious? What the Hell? you going to have 10 pages of this BS?

Why is this BS?

This is the technical section of the forum, no?

If you are not interested, move on to a DCT vs 6MT thread

[the_road_less_traveled]

Originally Posted by ibmike

Are you two^ serious? What the Hell? you going to have 10 pages of this BS?

prob, but maybe more.

[CanAutM3]

Originally Posted by xfirer1guy

prob, but maybe more.

[the_road_less_traveled]

Originally Posted by CanAutM3

Why is this BS?

This is the technical section of the forum, no?

If you are not interested, move on to a DCT vs 6MT thread

I actually think most would enjoy reading the discussion since there is relatively little technical content on this Site, but some enjoy reading the nonsense posts i suppose.

[Billj747]

So how would you explain a 991 GT3's 3.8L with 29lb ft more torque than the S65 and 200cc less with 750rpm higher redline (9,000rpm)?


DCT is faster

[catpat8000]

Originally Posted by Billj747

So how would you explain a 991 GT3's 3.8L with 29lb ft more torque than the S65 and 200cc less with 750rpm higher redline (9,000rpm)?

DCT is faster

The GT3 has a higher compression ratio (12.9:1), a better induction system, freer flowing exhaust, direct injection, and different cam timing. That's how it manages slightly higher torque out of slightly less displacement than the S65.

The redline is higher is because it has more exotic materials used in the valvetrain and in the bottom end - stuff like forged titanium connecting rods to reduce the mass of the reciprocating assembly - and because it has an oversquare bore x stroke (102 x 77.5 mm).

By comparison, the S65 also has an oversquare bore x stroke of 92 x 75.2 mm but the GT3 has significantly more potential valve area due to the larger bore, to enable better breathing at higher rpm. The S65 also uses steel con rods and "only" has 12:1 compression ratio.

[US///M3]

Originally Posted by ibmike

Are you two^ serious? What the Hell? you going to have 10 pages of this BS?

It's interesting...

[US///M3]

Originally Posted by CanAutM3

I'm also not following you. Let me attempt to re-explain my point:

If you increase stroke only, you increase torque. In the same manner, if you increase bore only, you also increase torque.

Both of these are the resultant of an increased displacement. So yes, a bigger engine is able to produce more torque, no rocket science here.

However, for a given displacement, altering the bore and stroke relationship has no geometrical effect on the torque produced.

+1

I saw this on Jalopnik.

5,608,310 lb-ft of torque and up to 108,920 BHP.

You need displacement to get that kind of torque.

[CanAutM3]

Originally Posted by US///M3

+1

I saw this on Jalopnik.

5,608,310 lb-ft of torque and up to 108,920 BHP.

You need displacement to get that kind of torque.

Good example

What the hell is that thing?

[CanAutM3]

Originally Posted by Billj747

So how would you explain a 991 GT3's 3.8L with 29lb ft more torque than the S65 and 200cc less with 750rpm higher redline (9,000rpm)?


DCT is faster

By increasing cylinder pressure with better overall efficiciency.

The GT3 engine flows better (volumetric efficiency), better utilises the intake charge (direct injection) and probably has less friction losses.

The GT3 engine example proves my point about the bore and stroke relationship. It has a much bigger bore vs stroke relationship (102/77.5) compared to the S65 (92/75.2). This bigger bore allows for a bigger head surface area and for bigger valves, which in turn improves volumetric efficiency. So oversquare engine don't produce less torque, myth busted .

[US///M3]

Originally Posted by CanAutM3

Good example

What the hell is that thing?

It's used on container ships...

http://jalopnik.com/the-largest-pist...loo-1480385814

[CanAutM3]

Originally Posted by US///M3

It's used on container ships...

http://jalopnik.com/the-largest-pist...loo-1480385814

That is what I thought, marine application...

What a monster

[Obioban]

Originally Posted by xfirer1guy

Its a trade off. Longer stroke = more torque => lower revs. It comes down to mean piston speed. It all conforms to that thing called physics and metallurgical limits.

I expect you to come back with some S54 specs next, but 7900 redline is not an 8750 redline. The S65 revs over 10% higher than the S54.

Lolwut?
S54 stock redline: 8000 rpm
S65 stock redline: 8400 rpm
That's 5% higher, not >10% higher

Comparing modded to stock makes no sense. And, for that matter, my S54 had a 8700 rpm redline for a bit (albeit by mistake, but no damage was done to the engine).

Stock vs stock (aka, with stock redlines), the S54 has high piston speed and a longer stroke, too

[the_road_less_traveled]

Originally Posted by CanAutM3

By increasing cylinder pressure with better overall efficiciency.

The GT3 engine flows better (volumetric efficiency), better utilises the intake charge (direct injection) and probably has less friction losses.

The GT3 engine example proves my point about the bore and stroke relationship. It has a much bigger bore vs stroke relationship (102/77.5) compared to the S65 (92/75.2). This bigger bore allows for a bigger head surface area and for bigger valves, which in turn improves volumetric efficiency. So oversquare engine don't produce less torque, myth busted .

The slightly higher compression contributes to the higher net work also.

[CanAutM3]

Originally Posted by xfirer1guy

The slightly higher compression contributes to the higher net work also.

Agreed

[325rider]

Originally Posted by bigjae1976

I'm sure there is a little more chassis rigidity but the E9X used more aluminum, the fenders are plastic, more FRP aka CF...we're not even talking about the DCT. Oh and lighter suspension components.

Just an observation rather than a complaint...more lightweight materials but heavier curb weight. The fact is the M3 is just about the lightest 4 seat sports sedan that you can ACTUALLY fit 4 adults in.

While this is true, I have a legitimate "civic" M3 with test pipes, AE mufflers, and Advan RS wheels. The weight is about 3500lbs probably (see photo), and maybe even 3,4xx lbs. with light fuel I think thats damn good for a sedan and will be closer to the actual F80 M3 weight than ppl think.

I am curious to see what the F80 M3 will weigh on car scales, because I on the record am going to state that the "average" F80 M3 being driven on the road will not weigh below 3400lbs on scales.

MY argument here is simply that IF you care about weight in your car, the e9x is still a viable platform if you forego options and go with light exhaust/wheels… It is annoying that people with electric seats, moon roofs, and 19" wheels are using weight as the "selling point" of the new M3/M4. Yes, the new car will be faster, but enthusiasts and car lovers who have SPECIFIC tastes and goals (feel/experience vs. a fact sheet) may more often than not prefer a stripped car w/ s65 V8 and less electronic nannies and gimmicks to the new "lighter" but MORE optioned F30/F80. I think BOTH cars have a case and logical reason to be owned by all types of people, but to say that the "new M3/M4" are lighter and to use that as a selling point is ///MARKETING. This statement will be pretty much null/irrelevant if a handful of F80s start weighing in at 3,3xx lbs on scales. BUT, Im calling BS on that…. They will all be 3,4xx on scales, thus, resulting in a weight loss of 100lbs. Woopty dooooo

That said, a stripped F80 M3 stock w/ CF roof + CFRP driveshaft and light weight redux (3,2xx lbs on scales) will probably be sickeningly fast and walk a loaded e90 M3

Haters gonna hate.


this example is of a car with the following specs…
-19" wheels
-M-DCT
-EDC
-Nav (Tech. Package)

1/4 tank of fuel.

[regular guy]

Originally Posted by ibmike

Are you two^ serious? What the Hell? you going to have 10 pages of this BS?

I thought you were going to say "10 pages of this BS...like the bearing Wiki thread?"

But seriously, this is something I've always been told and wondered about it. So I'm definitely reading and learning here. I'm interested.

[the_road_less_traveled]

I've got 4 pages of Otto Cycle thermodynamic equations, graphs and diagrams I'll try to load tonight. It's in pdf format so it'll take some trickery to load. It's solid engineering on engine Net Work (torque if you will) and efficiency. Stay tuned!