[Bunkei]

I guess the reason I'm asking this question is because the success GM (and Chrysler to a certain extent) have had with their designs. GM's small block LS-series V8 have been shoehorned to every car you can think of--foreign and domestic. Despite the 'simple' technology, you can't argue with the results. For about $2K you can have a fire breathing LSx V8 producing 500 rwhp. No wonder it's featured in so many project cars including BMWs!

Even compared to BMW's 4.0 V8 in the current M3, the LS2 is physically smaller, makes more power and torque, and better fuel economy. Don't misunderstand. I'm not slamming BMW; heck I own one. But given the recent issues with HPFP and so forth, it makes me wonder why no manufacturers except GM and Chrysler are using OHV design. There were so many myths; like 'archaic', when OHC engines got started near the turn of the 20th century whereas OHV engines didn't show up until the 1950's on american soils. Another myth that 'it doesn't rev' I'm no motor expert, but even this sounds shaky to start with. The LS7's redline is 7000 RPM, although there's nothing to be had by going to redline in terms of power.

In this age, where everything's becoming needlessly complicated, maybe it's time to embrace the 'less is more' philosophy. What do you motorheads think?

[328i M-Sport]

As someone who tuned a lot GM LTx/LSx engines I already posted a reply in another thread.

"In short, OHV engines have a heavier valvetrain and only 2 valves. That makes it difficult to make the engine to make the engine make power at high rpms without being expensive and requiring frequent maintenance such as valve adjustments (for mechanical roller lifters). And peak hp is what sells the vehicles from the marketing perspective.

OHV engines have their benefits. They are more compact and make more torque down low. But newer technologies in the modern OHC engines such as variable valve timing and the use of turbochargers make up for it."

I have another car, Mazda RX7 with an LS6 engine (custom cam, ported heads, etc). The car makes 418 rwhp and runs mid 11s in the 1/4 all year. It revs to 6800 rpms.

The interesting thing is it's fuel milege is 28-30 mpg in mixed driving while my 328 only does 23-24 mpg. However, the car is about 500 lbs lighter and has 2 overdrive gears (T56 manual transmission) vs. 1 overdrive gear (BMW manual 6-speed). The engine weighs only 95 lbs more considering that it has almost twice the displacement and a mechanical waterpump with a housing.

[Bunkei]

Yeah it seems that perception and marketing led to the demise of the OHV more than anything else. The modern LS3 is an excellent example; compared to the original LS1, it makes way more power, using less gas, while weighing less. With the hollow stems, peak horsepower is at a DOHC-like 5900 RPM, with the limit at 6600 RPM. All of this with no need for the owner to do valve adjustments.

Every design has limitations, but GM is showing that with enough R & D, those limitations can be mitigated to a degree if not eliminated. That's why I'm surprised given the simplicity of OHV design, with the compactness, and efficiency that it never gained popularity that I think it deserves. I'm excited to see the Gen V small block, as it's supposed to be quite a departure from the previous generations.

[328i M-Sport]

LSx engines use heads with a 15* valve angle that is basically a race car technology that was made to work on regular cars. They flow about twice as much as air the first generation small block heads. Also, valve to cylinder bore has been improved so bigger valves can be used without being shrouded.

This design works great on big displacement engines that does not need super high rpms to make a lot of power. Also LSx engines are much more boost friendly compared to the previous 2 generations. That is why we are seeing cars like Cadillac CTS-V and Corvette ZR1.

But making a cheap OHV 4-banger that revs to 8500 rpms is a lot more difficult than using the OHC technology. And with all the EPA restrictions, car manufacturers would rather invest in smaller engines.

[O-cha]

Don't assume that because the engine is cheaper to get more power from that that means it's better. There is just SO MUCH development that has been but into the ls motors that everything is cheap.

Measurement of how "good" a motor is is usually power per liter, and LS motors are some of the worst out there for that.

[328i M-Sport]

Originally Posted by O-cha

Measurement of how "good" a motor is is usually power per liter, and LS motors are some of the worst out there for that.

I never understood that metric. You can compensate for a lack of displacement with moving the powerband higher into the rpm range.

Also, why is it a problem for an engine to have a bigger displacement if it is compact and has good fuel mileage?

Also a 328i makes 230 peak hp from a 3L engine. LS3 makes 436 hp from a 6.2L... not a big difference in my book. If you compare the whole power curve area, LS3 has a bit of an advantage.

[Q4P]

Great question... the GS C6, Z06 and Zr1 are arguably primitive designs by many yet still tend to whoop up on the competition with their much simpler, less technological designs. At the same time; they are all very large motors and don't particularly rev high nor do they make a particularly large amount of hp/liter... so is it correct to assume that this technology wouldn't work too well in smaller motors for more fuel efficient cars?

At the same time how is Ferrari able to make 570 hp out of a 4.5L V8 and how is Porsche able to make 500 hp out of a flat 6? I understand that this has something to do with the advanced valve design but I would like if some engine expert could chime in and explain.

[Bunkei]

But I think people are mislead by large displacement. They're thinking that more displacement = bigger engine, when it has nothing to do with the actual size of the engine. In fact, that's one of the advantages of the OHV layout is the fact that the engine is smaller in size and weight compared to similar output DOHC V8s.

The displacement is just the measurement of the area from the very top to the very bottom that a piston covers inside a cylinder.

[Bunkei]

Originally Posted by 328i M-Sport

LSx engines use heads with a 15* valve angle that is basically a race car technology that was made to work on regular cars. They flow about twice as much as air the first generation small block heads. Also, valve to cylinder bore has been improved so bigger valves can be used without being shrouded.

This design works great on big displacement engines that does not need super high rpms to make a lot of power. Also LSx engines are much more boost friendly compared to the previous 2 generations. That is why we are seeing cars like Cadillac CTS-V and Corvette ZR1.

But making a cheap OHV 4-banger that revs to 8500 rpms is a lot more difficult than using the OHC technology. And with all the EPA restrictions, car manufacturers would rather invest in smaller engines.

Yeah I think the OHV design is best used in 8 cylinder applications or more from what I've read. I don't see much advantage in a 4 cylinder. 6 cylinders are debatable. I remember GM showing a 3-valve N/A 3 liter OHV engine in concept form several years ago that made 270+ hp. However, that's a moot point because the 3.6 DOHC V6 engines that were being used in Cadillac and now has spread into the FWD cars seems to do the job just fine.

[Bunkei]

Originally Posted by Questforpower

Great question... the GS C6, Z06 and Zr1 are arguably primitive designs by many yet still tend to whoop up on the competition with their much simpler, less technological designs. At the same time; they are all very large motors and don't particularly rev high nor do they make a particularly large amount of hp/liter... so is it correct to assume that this technology wouldn't work too well in smaller motors for more fuel efficient cars?

At the same time how is Ferrari able to make 570 hp out of a 4.5L V8 and how is Porsche able to make 500 hp out of a flat 6? I understand that this has something to do with the advanced valve design but I would like if some engine expert could chime in and explain.

But it's really not primitive. OHC engine design is quite a bit older than OHV. OHC has been around since the turn of the 20th century. The first OHV production engine was introduced by Oldsmobile back in 1949. Plus, hp/liter is marketing hype and doesn't speak to the efficiency of the engine as is lead to believe. As for Ferrari and Porsche, no idea. Although you certainly could achieve similar figures with an OHV design, but with less cost to build, and certainly a lot cheaper for the owner to repair.