M/S62 build ruminations

[mattmartindrift]

The I6 should be considerably easier to push to the higher RPM ranges due to the neutral balance of the crankshaft, considerably reduced mass and rotational moment(forgive the incorrect terminology, too tired to research the correct term) of the crank, 7 main bearings(compared to 5 on the V8) and the let-in design of the bearing caps.

I6 crank


V8 Crank



All that said pushing ANY engine beyond about 8k requires significant work and strengthening, its just the way it is.

Any engine, aren't there OEM Honda engines that turn 9k out of the box?

Toyota 1jz spin 8k all day long, with bursts above.

Nissan SR20s have spun 9k for races with only solid lash adjusters in the valve train.

[xatlas0]

The I6 should be considerably easier to push to the higher RPM ranges due to the neutral balance of the crankshaft, considerably reduced mass and rotational moment(forgive the incorrect terminology, too tired to research the correct term) of the crank, 7 main bearings(compared to 5 on the V8) and the let-in design of the bearing caps.

I6 crank


V8 Crank



All that said pushing ANY engine beyond about 8k requires significant work and strengthening, its just the way it is.

Actually, the longer crank puts more stress on the front and rear journal bearings due to the longer moment arm from the front and rear pistons. The V8 and straight 6 are both naturally harmonically balanced, so that isn't a big deal either. The additional rotating mass is mitigated by the reduced crank length, to a degree.

Overall, I would say there is no inherent issue with trying to rev the crud out of a V8 over a straight 6, given the disadvantages the 6 has in terms of packaging and moment arms. This is part of the reason why the E34 S38B38 had major journal bearing issues. Similarly, the early S54 had journal bearing issues relating to high-RPM operation and crank moments. This issue is one of the main reasons you don't see many ultra-high revving large displacement straight 6s, while there are quite a few similarly-displaced V8s revving to 8k+ from several manufacturers.

[bmw chris]

Overall, I would say there is no inherent issue with trying to rev the crud out of a V8 over a straight 6, given the disadvantages the 6 has in terms of packaging and moment arms. This is part of the reason why the E34 S38B38 had major journal bearing issues. Similarly, the early S54 had journal bearing issues relating to high-RPM operation and crank moments. This issue is one of the main reasons you don't see many ultra-high revving large displacement straight 6s, while there are quite a few similarly-displaced V8s revving to 8k+ from several manufacturers.

You also dont see many manufacturers running I6 for anything but diesels. And you are correct as far as design basics. I still agree with NNY528 that in this case it would be easier to get the I6 to spin that fast as opposed to the V8. Personally I think it would be pretty cool to see a BMW V8 with an 8K redline, but I dont think it very practical.

[e39dream]

something about an inline 6 screaming at 8k RPM just sounds heavenly.

Look at 2:40 in this video, that is an M54 in this e36.
[ame]http://www.youtube.com/watch?v=OzfUTE1ekjs[/ame]

If you want low down torque stick with the v8. If you want to hear it sing at high rpm mod an I6.

[nighttowl]

i dont see why 8k plus rpm on an m62 would not be attainable. small block chevy guys know that the 350 4 bolt main blocks have held to 9500+ rpm on the track. the m62 has 4 bolt mains, with the outer bolts spayed for strength, which is a costly mod for the chevy guys, standard on bmw. obviously, the crank and flywheel assembly would need to be professionally balanced, with higher quality rods used. the only issue with this is where you would find some moster cams, solid lifters, high rpm intake and large diameter headers to support them? obviously cu$tom.

although im not an inline 6 fan, you could build a seriously bad assed one for that kind of cash, or it would most likely be cheaper to buy the 12k dinan supercharger package.

[BimmerBreaker]

Any engine, aren't there OEM Honda engines that turn 9k out of the box?

Toyota 1jz spin 8k all day long, with bursts above.

Nissan SR20s have spun 9k for races with only solid lash adjusters in the valve train.

Yeah but all those engines require SIGNIFICANT work to get there. The honda is a FOUR cylinder engine, and yeah it comes from the factory that way but its not like it didnt require a lot of work and design. Supras and other engines spinning that high also require a lot of work, its not as easy as just adding this or adding that.

You can get any engine to spin to 9K but if you want reliability you will need a full build

[NNY528I]

Actually, the longer crank puts more stress on the front and rear journal bearings due to the longer moment arm from the front and rear pistons. The V8 and straight 6 are both naturally harmonically balanced, so that isn't a big deal either. The additional rotating mass is mitigated by the reduced crank length, to a degree.

Overall, I would say there is no inherent issue with trying to rev the crud out of a V8 over a straight 6, given the disadvantages the 6 has in terms of packaging and moment arms. This is part of the reason why the E34 S38B38 had major journal bearing issues. Similarly, the early S54 had journal bearing issues relating to high-RPM operation and crank moments. This issue is one of the main reasons you don't see many ultra-high revving large displacement straight 6s, while there are quite a few similarly-displaced V8s revving to 8k+ from several manufacturers.

The only Naturally or neutrally balanced engines(primary and secondary balance) in practical use are I6 Flat 6 and V12 engines all others including V8s have inherent design balance issues. For V8s it is a heavy offset crank assembly which increases rotational mass and can exacerbate any balance issues. All engines are balanced otherwise they would shake themselves to pieces, but I6 is neutral out of the box and does not experience the destructive vibrational forces at high RPMS that a V8 does. While High RPMs in an I6 have issues with the torsional flex that is a relatively small issue for this discussion, the reason you see more V8s has little to do with design issues and more to do with packaging and preference, V8s are far more common than I6s and I6s tend to be used in lower RPM higher torque applications, BMW is one of very few manufacturers who still produce performance I6 engines. Almost all applications of either engine tend to top out in the mid 8000 rpm range while some 4 cylinders push on into the 9000 rpm range, once you pass these points though you enter an entirely new world of forces requiring bigger and heavier or more severely constructed components(ever see the crank out of a top fuel dragster).

[xatlas0]

The only Naturally or neutrally balanced engines(primary and secondary balance) in practical use are I6 Flat 6 and V12 engines all others including V8s have inherent design balance issues. For V8s it is a heavy offset crank assembly which increases rotational mass and can exacerbate any balance issues. All engines are balanced otherwise they would shake themselves to pieces, but I6 is neutral out of the box and does not experience the destructive vibrational forces at high RPMS that a V8 does. While High RPMs in an I6 have issues with the torsional flex that is a relatively small issue for this discussion, the reason you see more V8s has little to do with design issues and more to do with packaging and preference, V8s are far more common than I6s and I6s tend to be used in lower RPM higher torque applications, BMW is one of very few manufacturers who still produce performance I6 engines. Almost all applications of either engine tend to top out in the mid 8000 rpm range while some 4 cylinders push on into the 9000 rpm range, once you pass these points though you enter an entirely new world of forces requiring bigger and heavier or more severely constructed components(ever see the crank out of a top fuel dragster).

Ah, but you are forgetting that the M60/62/S62 is a crossplane V8, making it, in fact, a naturally balanced engine, with the same harmonic properties as a straight 3, 6, or V12. (The Internal-combustion Engine in Theory and Practice, Taylor Vol.2) Almost all modern V8s are crossplane V8s for this very reason.

You see few large-displacement, high-revving straight 6s due to the large, non-axial moments introduced by the longer crank. These forces cause highly uneven bearing force distribution on the journal bearings.

Also, once you go to higher RPMs, the name of the game is reducing mass while maintaining strength, as the forces are directly linked to the masses. (Can't escape Newton, unless you are the planet Mercury!) This is partially why you can have a motorcycle engine rev so high; the internal components weigh so little that the forces involved are significantly reduced. You can see it plainly in F1 engines; they build these engines for 14k RPMs not by making them larger, but by reducing the part masses. This leads to a fairly limited lifespan due to fatigue properties, but the lighter mass, and therefore reduced forces, let them live as long as they do.

[BimmerBreaker]

Yes but in an interesting twist the higher-revving more powerful Ferrari engines are largely flat crank V8s! Sound better, more power output, at the expense of being inherently unbalanced.

Just goes to show power isnt ALWAYS in the inherint balance of the engine, but more so in the design to get there. Any engine can spin to any RPM (some will just explode at lower RPMS!) but it takes a lot of mods to make more power past a certain point.

[mattmartindrift]

Yeah but all those engines require SIGNIFICANT work to get there. The honda is a FOUR cylinder engine, and yeah it comes from the factory that way but its not like it didnt require a lot of work and design. Supras and other engines spinning that high also require a lot of work, its not as easy as just adding this or adding that.

You can get any engine to spin to 9K but if you want reliability you will need a full build

no, they don't. toyota 1jz will spin 8k+ out of the box, I owned one, I did it - stock internals.

stop arguing for the sake of arguing.

[NNY528I]

Ah, but you are forgetting that the M60/62/S62 is a crossplane V8, making it, in fact, a naturally balanced engine, with the same harmonic properties as a straight 3, 6, or V12. (The Internal-combustion Engine in Theory and Practice, Taylor Vol.2) Almost all modern V8s are crossplane V8s for this very reason.

You see few large-displacement, high-revving straight 6s due to the large, non-axial moments introduced by the longer crank. These forces cause highly uneven bearing force distribution on the journal bearings.

Also, once you go to higher RPMs, the name of the game is reducing mass while maintaining strength, as the forces are directly linked to the masses. (Can't escape Newton, unless you are the planet Mercury!) This is partially why you can have a motorcycle engine rev so high; the internal components weigh so little that the forces involved are significantly reduced. You can see it plainly in F1 engines; they build these engines for 14k RPMs not by making them larger, but by reducing the part masses. This leads to a fairly limited lifespan due to fatigue properties, but the lighter mass, and therefore reduced forces, let them live as long as they do.

in order to maintain balance crossplane V8s require very large heavy counterweights in the crank(which is why flatplanes are the prefered setup for really high strung engines as the have a reduced mass in the crank allowing faster acceleration but ar more complex due to the required addition of balance shafts)

The point being is that both designs have inherent issues limiting them if pushed beyond about 8k rpms, since the i6 is already able to achieve 7k without mods and the M motors exceed 8000 I suspect for a mild build that it would be less technically and costly to bring the I6 to that level as opposed to trying to destroke, overbore and forge crank a V8 in order to get it up to that range.

[E39bmw]

Yes but in an interesting twist the higher-revving more powerful Ferrari engines are largely flat crank V8s! Sound better, more power output, at the expense of being inherently unbalanced.

Just goes to show power isnt ALWAYS in the inherint balance of the engine, but more so in the design to get there. Any engine can spin to any RPM (some will just explode at lower RPMS!) but it takes a lot of mods to make more power past a certain point.

I used to have 2000 civic with one of the worst designed Honda engines in history(D16Y8) and I kept it at 7.5K RPM all night long on GMR and Wilson. The engine was BONE STOCK.

[moroza]

Well, glad we got a good discussion going after all. I'm convinced to not bother with this simply due to the large number of unknowns that could turn into expensive issues if I guess wrong. On a hunch, would an S62 with an upgraded valvetrain and minor bottom end work spin to 8-8.5 safely? Probably. Do I want to take the 4, 5-figure risk of finding out otherwise? No. Would I ultimately gain any power by spinning a destroked and tuned S62 another 1k revs? Jury's still out but in any case, it seems far more effort and risk than is worth it.

I now have this idea in my head of finding an E34 530i and experimenting with that. B30's are next to worthless these days, so shooting a rod out the block or whatnot would be a relatively inexpensive learning experience. Plus they have nearly the same valvetrain as the B40 - same cams, lifters, chain, aso. Just smaller valves.

Regarding the crankshafts, they're all forged except the M60B30 and possibly the (irrelevant anyway) M62B35. The counterweights are substantial, but they aren't reciprocating mass; sure, it still stresses the bearings and rest of the assembly more than lighter ones, but I would imagine to a much lesser extent than piston/rod mass and speed, and with less exacerbation at higher RPM's?

Looking at the various engine configurations and their rev limits, it seems that in practice, rotating mass has more to do with it than balance - I4's and flatplane V8's spin higher than I6's and crossplane V8's. AFAIK the Ferrari engine does not have balance shafts, and it's indeed a pretty rough-feeling engine (went for a few laps in a 360 Challenge Stradale once, on Laguna Seca ). That one spins to 8500 and the owner seemed to think it was fine doing 8000+ sustained, upwards of 9 in bursts. Besides its regular exhaust noise, right before redline it starts making this beautiful rushing wail; I admit that this experience has something to do with the idea of a high-RPM M62, apples to oranges though it may be.

[bmw chris]

Read this, will give you a much better understanding of the forces involved.

http://www.autozine.org/technical_sc...ne/smooth1.htm

[mattmartindrift]

Talk to Dinan about their S62s. They build them for handful of Grand Am race cars. Under the most extreme circumstances, those motors have to take sustained high revs for 24+ hours.

[lsvtecwill]

I like this thread. I my self have a e34 530i that i switched to the 4.0 m60. The biggest problem I see is camshaft design and availability of aftermarket cams. I use to own a 9k+ rpm honda engine (8.3k out of the box with mods), and on those bad boys you can swap out cams in like an hour and a half. Now I can tell you if you up the red-line the cams wont keep making power they will still drop torque at around 5.5~6k. So the main problem I see is where are you going to get the cams to run above 7k? custom grind?

[moroza]

I like this thread. I my self have a e34 530i that i switched to the 4.0 m60. The biggest problem I see is camshaft design and availability of aftermarket cams. I use to own a 9k+ rpm honda engine (8.3k out of the box with mods), and on those bad boys you can swap out cams in like an hour and a half. Now I can tell you if you up the red-line the cams wont keep making power they will still drop torque at around 5.5~6k. So the main problem I see is where are you going to get the cams to run above 7k? custom grind?

Custom cams, probably. There are at least two companies making cams for this engine - Catcams and... I forget who else. To an extent, some relatively minor power gains can be had by messing with static cam timing, though I probably wouldn't go there for a few reasons.

A more immediately feasible goal than building an all-out firebreathing V8 is to get one to spin to, say, 7k sustained, 7.5k burst; the rotating assembly and oiling system can probably take that (and playing with an otherwise worthless B30 would be a great way to find out), the only trick then is to make power, since it's already falling off by 6. Could probably be done relatively cheaply - shorten the intake runners, for one.

[2cants]

i dont see why 8k plus rpm on an m62 would not be attainable. small block chevy guys know that the 350 4 bolt main blocks have held to 9500+ rpm on the track. the m62 has 4 bolt mains, with the outer bolts spayed for strength, which is a costly mod for the chevy guys, standard on bmw. obviously, the crank and flywheel assembly would need to be professionally balanced, with higher quality rods used. the only issue with this is where you would find some moster cams, solid lifters, high rpm intake and large diameter headers to support them? obviously cu$tom.

although im not an inline 6 fan, you could build a seriously bad assed one for that kind of cash, or it would most likely be cheaper to buy the 12k dinan supercharger package.

8000rpm 100% achievable.
https://youtu.be/WiWc4F5v1tc
I also race an Euro E36, check out my channel.

The engine was 4.5L darton sleeved with CP pistons and Carrillo rods. Revved hard to over 8000. 515HP on crank.
unfortunately I blew this up when I miss-shifted the dog box from 3 to 2nd by mistake (should have been 4th) and hit 9600rpm. The cranks broke in half and we found a broken journal bolt support in the engine. The pistons/rods and darton sleeves were fine. I decided not to reuse them i the rebuild.

My next engine was 4.4L with Alusil compatible high compression pistons. This revved to 7200 easily. I made custom carbon fibre I intake and trumpets for the S62 ITB. Yes you read that right, my M62 has S62 ITB’s which bolt straight onto the ported M62 heads running racing cam shafts with solid lifter followers. 494 HP at crank.
That engine blew to bits at 7600rpm while I was testing the new CF plenum and shorter trumpets (velocity stacks). Cylinder #2 conrod broke, putting pieces into space. Either the rods where over tightened during the build opened/or low oil pressure (80psi at 7000 rpm but 18psi at 1200 idle).

I am in the process rebuilding new M62 with Molnar rods (come with asymmetric ARP2000 rod bolts), CP Alusil pistons and ACL race bearings. I will retain the heads but use race valves. The new engine builder will out 3 angles into the valves.
The M62 crank is forged at factory and is run in a custom dry sump with Peterson pump. Straight exhaust with x pipe in middle with side expedited behind passenger door. 6 speed Holinger H6S with geartronics GCU.
Bosch M5 ABS protects the Michelin 18”x10 rims.
awesome car to drive but still needs the KW competition 2-way shocks and springs setup.