6k rpm isn't a limit for OHV in any universe I know of. I spin my old design small block Mopar to 6100 and that's with 5/16" pushrods and pedestal rockers. There are tons of better valvetrain parts I could put into the thing, at which point 7500+ would be no problem without valve float or the valvetrain coming apart.
Yes, it's easier to make OHC rev stupidly high, but OHV isn't at some huge disadvantage there.
Let your friend actually work at an engineering job, the larger the company the better, for a few years, then revisit this and ask him again how optimal he really thinks a design at a large manufacturer could be 
In reply to markwemple :
Yes, berkeley your pushrods! In fact, berkeley valves entirely! Step into the future:
If only they didn't burn massive amounts of oil and got such crappy mpg. Remember my racer is an RX7.
In reply to alfadriver :
Wonderful arrogance. And BTW OHC is not 100, more like 90, with the Bugatti, when the flat head in the US was just coming along. So you're argument is that, since Europe developed advanced tech way before us, then it's older and older is inferior?? Corvettes had FI over 50 years ago, but that FI has nothing to do with today's FI. Again, pushrods are cheap and, tell me when the last, good GM OHC was. Ford is still working on the development of the OHC (with teething problems). Since you're an engineering genius, how would you build a 4 or 5 valve OHV engine? You know, to maximize head flow? (More in and out creates more power)
In reply to markwemple :
I think what they're saying, is that the pushrod, 2 valve designs coming out of GM and FCA are making power and torque that is comparable to, or exceeds OHC designs from other competitors (and doing it with a smaller physical package too) so there's not much motivation to switch to a configuration with more valves.
In reply to markwemple :
Actually more like 100+ for OHC (EDIT: wiki says the configuration first appeared in 1902, so 115), and DOHC at that. And it wasn't Bugatti http://revsinstitute.org/the-collection/1913-peugeot/
BTW, the ECOTEC series of 4 cylinders from GM are considered to be pretty good. So is the LFX 3.6 V6.. Engine and powertrain is usually one of GM's strengths, not just HVAC..
STM317 said:In reply to markwemple :
I think what they're saying, is that the pushrod, 2 valve designs coming out of GM and FCA are making power and torque that is comparable to, or exceeds OHC designs from other competitors (and doing it with a smaller physical package too) so there's not much motivation to switch to a configuration with more valves.
Exactly this. They haven't hit the limits of pushrods yet, so going to overhead cams adds size and complexity (and probably weight), but not much real benefit.
In reply to markwemple :
I think perhaps someone needs to educate you in terms of what Alfa does for a living and who his employer is.
Didn't you already hijack a thread like this a while back to do the anti-pushrod rant? We're pretty over it. Maximum HP potential using the least fuel in the smallest package. It's hard to argue with the current crop of GM V8s in this regard, and arguing with a shotgun, as you've been doing, is just making you look foolish. Ford has been doing pretty well with it's OHC designs, so perhaps, just perhaps, and I am speaking from an engineers standpoint here, there is more way to solve this problem.
markwemple said:In reply to alfadriver :
Wonderful arrogance. And BTW OHC is not 100, more like 90, with the Bugatti, when the flat head in the US was just coming along. So you're argument is that, since Europe developed advanced tech way before us, then it's older and older is inferior?? Corvettes had FI over 50 years ago, but that FI has nothing to do with today's FI. Again, pushrods are cheap and, tell me when the last, good GM OHC was. Ford is still working on the development of the OHC (with teething problems). Since you're an engineering genius, how would you build a 4 or 5 valve OHV engine? You know, to maximize head flow? (More in and out creates more power)
I'm ok with being arrogant when faced with such obvious wrong opinions that it needs to be called out.
Not once did I claim to be anything, just pointing out holes in your argument. YOU claimed modern, I'm saying it's not. That's no a judgement of which is better or worse- just how old the technology is.
"More Power" is not better, it's just more power. That needs to be put into the context of how the engine is used. If power is the #1 item for the engine, then a high speed, air valve, 4 V engine like in F1 is going to be the layout. But that kind of engine isn't what real production cars use, since peak power is barely ever used in the real world. GM's LS motor has it's advantages, just like our DOHC engines have their advantages- both have drawbacks, too. At the moment, I can't really tell you that there is one ideal way of valve control.
BTW, you should check out diesel engines- they have some very creative valvetrains that are 4V pushrods, with valves in locations that are really interesting. Oh, and some OHC engines do use pushrods. The Alfa V6 is one that I'm more familiar with. And many OHC engines have some very complex rocker systems that have their issues, too. But that is a trade off to get advantages over direct bucket systems.
One other thing, 1912 was 105 years ago. Not 90. Which is less modern than fuel injection, less modern than forced induction, less modern than computers, etc. It's not modern. I guess that in the context of valvetrain, it can be called more modern than OHV, but that's because one is 102 years old vs. closer to 150. Big deal.
In reply to markwemple :
You seem to be confusing text books with the real world. In the real world, the LS engine series is incredible and achieves things (weight vs power, size vs power, efficiency vs power) that DOHC engines would only dream of. You've let the inner nerd take over the practical side and decided that theory is more important than actual performance.
GM has had a ton of very good DOHC engines. Even now they make a v6 that puts out 400hp and 400lb-ft of torque in a high line application. But because they realize "technology" (which we've already established isn't even new tech) isn't worth using for it's own sake you've decided they're incapable of a good DOHC design. That's just false. And! They now have direct injection and variable valve timing with push rods. Tell me why push rods are holding them back? It's certainly not for power output, weight, efficiency, or even technology reasons.
tuna55 said:In reply to markwemple :
I think perhaps someone needs to educate you in terms of what Alfa does for a living and who his employer is.
Didn't you already hijack a thread like this a while back to do the anti-pushrod rant? We're pretty over it. Maximum HP potential using the least fuel in the smallest package. It's hard to argue with the current crop of GM V8s in this regard, and arguing with a shotgun, as you've been doing, is just making you look foolish. Ford has been doing pretty well with it's OHC designs, so perhaps, just perhaps, and I am speaking from an engineers standpoint here, there is more way to solve this problem.
And honestly, there are some major issues with the OHC engines that makes me wish that we just solved the justified reason for tanking the 5.0 and 5.8l families. The #1 issue with those engines was claimed to be deformation of the cylinders. Which is actually an easy problem to solve that does not require a head design that introduced some HUGE air and fuel flow compromises....
Nothing is perfect.
[CHESNOKOV]
WHY YOU WANT OHC FOR ENGINE? IS NOT GOOD ENOUGH AS PROCURED FROM GENERAL MOTORS? YOU THINK NEEDS IMPROVEMENT? THEN MAYBE YOU FIND JOB WITH COMPANY OF DETROIT! YOU HAVE DRINKS WITH MARK REUSS, TRADE STORY OF MANY ENGINES DESIGNED AND DETAILS OF SCHOOL FOR ENGINEERING!
OR MAYBE YOU NOT DO THIS. PROBABLY IS BECAUSE YOU NEVER DESIGN ENGINE IN WHOLE LIFE. YOU LOOK AT FINE AMERICAN ENGINE, THINK IT NEED CRAZY E36 M3 STICK ON ALL SIDES OF HEADS. YOU HAVE DISEASE OF AMERICAN CAPITALIST, CHANGE THING THAT IS FINE FOR NO REASON EXCEPT TO LOOK DIFFERENT FROM COMRADE. YOU PUT CHEAP TURBOCHARGER OF CHINESE SLAVE FACTORY ON ONE SIDE, YOU PUT BAD SUPERCHARGER OF AMERICAN MIDDLE WEST ON OTHER SIDE, YOU PUT SHAFTS OF CAM ON TOP SO YOU ARE LIKE AMERICAN MOVIE GUY PAUL WALKER.
ENGINE IS FINE. YOU berkeley IT, IT ONLY GET GIGANTIC AND YOU STILL NO PASS LARGEST CAR OF HPDE. GO TO RACE TRACK, PRACTICE WITH MANY TANK OF FUEL. THEN YOU NOT NEED DUMB E36 M3 PUT ON TOP OF CYLINDER HEAD.
[/CHESNOKOV]
Internal combustion....HA! Steam is where it's at.
I'm sure there was a serious discussion happening, but I'm no longer capable of forming a serious thought on the matter thanks to the artist formerly known as nonack. (Somehow I couldn't even copy/paste right today.)
Each design has its own advantages and disadvantages. For the street a long flat torque curve is desirable as it lets the driver accelerate from any speed. F1 race engines with high rpm and a narrow torque band would be very impractical as the driver would have to shift every time acceleration was needed. There is not a single engine design that will work for all situations. Racing is about all out power and the driver must adapt to the engine. Driving on the street for most people(not most of the ones reading this) is about ease and comfort. To see how impractical an F1 engine would be for the street go back several years and look at Richard Hammond from Top Gear try to drive an F1 car. It took him several tries just to get it moving then only hit full throttle for less than a second.
To answer the original question you first have to define better. Better at what? What are the design targets and constraints?
Pretty much everything in engineering is a compromise and/or a balancing act. The simplified old line about "Fast, cheap or Good. Pick two" is pretty accurate.
The other thing to keep in mind is that marketing has a huge input into what gets built. While I don't like that, it's the way it should be. If that weren't the case we engineers would only be building things that engineers want to buy. I tell my guys that our job is to design what marketing wants, no matter how stupid it is.
Harley Davidson spend millions of dollars in R&D and uses a ton of advanced technology to design traditional motorcycles that appear low tech. If you take the time to understand the design goals and constraints a modern Harley Davidson is impressively engineered. The same is true of a NASCAR cup engine and the LS series of GM engines. In all three of those cases it's not the the companies involved aren't capable of designing and building something more sophisticated or modern. It's that the marketing folks want products with traditional elements.
As an aside. I think that it's really cool that this site has folks that are so passionate bout engine design that they're arguing about it in ways that push the limits of acceptable forum etiquette. Take a deep breath guys.
Tyler H said:Internal combustion....HA! Steam is where it's at.
In the Stanley Museum in Kingfield, Maine (Link) there's a copy of a letter from one of the Stanley brothers to someone (I can't remember who) that describes all the ways that steam is inferior to an internal combustion engine for automobiles. It goes on to say that they pretty much wasted all of the time and effort that they spend on developing the steam powered automobile.
markwemple said:If only they didn't burn massive amounts of oil and got such crappy mpg.
But these are only problems in the real world. Based on all of your other arguments* here, apparently you only judge engines based on theory...So why should such realities prevent you from promoting the universal superiority of the Wankel engine design?
*All of which basically just boil down to the same hp/l argument of grossly overstated importance.
Clearly the answer is not the Bugatti or the LSX.
The answer is EMD 645. Power to shame both. This SOB really does pull like a freight train.
APEowner, the HD thing slays me. The engine sound is patented and is due to poor engineering in the timing. But, since it's popular, they stuck with it. IMO, HD builds the worst things, period. I think the 4.99 toaster at Walmart is better built. Not just based upon my experience but also on everyone I know that is not HD brainwashed. But, that is another can or worms, like which oil is better.
Oh, and I own an LS powered vehicle. A truck. Where that anchor, I mean simple, rugged design, is an appropriate tool for the job.
In reply to Appleseed :
Is it bad that I recognized the punching guy as being from office space?
Nope, great movie.
That's why I picked it.
Michael Bolton? Like the singer?
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