Push Rod vs. DOHC engines

[Rayme]

I have a hard time believing the "size" and "weight" argument is always valid as far as pushrods engines goes.

Considering motorcycles greatly benefit of smaller size and weight, I can't beleive one could take an inline 4, converted it to pushrod / 2 valves per cylinder, up the displacement and get a better engine still pushing almost 200 hp. It would be noisy/rattly and couldn't rev for crap.

Buell's V-twin never came close to what ducati or even the japanese did with their dohc engines.


Case in point, each technology has its ups and down, and the specific vehicle they go in is probably the most important factor about what to use.

[blur]

Originally Posted by serialk11r

an LS3 is lighter than an S65, which is already extremely light (the S54 was heavier). GM managed to make a 6.2L lighter than a 3.2L BMW engine. That is impressive.

We all know inline 6s are inherently heavier due to the block design... just look at 1JZ, 2JZ, RB20, RB25, RB26, M50, M54, S50. all very similar weight.

[ZDan]

Originally Posted by ottopilot

I have a hard time believing the "size" and "weight" argument is always valid as far as pushrods engines goes.

4.6 liter DOHC Ford mod motor vs. 5.0 liter OHV engine it replaced:


4.0 liter DOHC Toyota 1UZ V8 vs. 5.7 liter LS1 (same external dimensions as current 6.2):

Considering motorcycles greatly benefit of smaller size and weight, I can't beleive one could take an inline 4, converted it to pushrod / 2 valves per cylinder, up the displacement and get a better engine still pushing almost 200 hp. It would be noisy/rattly and couldn't rev for crap.

Benefits of OHV cam-in-block design are pretty much limited to V-engine layouts, where there's a big valley with plenty of room for a camshaft and pushrods. Inline engines definitely want to be SOHC or DOHC.

Buell's V-twin never came close to what ducati or even the japanese did with their dohc engines.

Presumably talking about the old air-cooled H-D twin and not the later Rotax mill (which was DOHC/4vpc). Suffice it to say, the very long-stroke air-cooled Harley engine was never by any stretch designed to be a performance engine. Not really a valid comparison.

LS3 vs. S65 is a MUCH more reasonable comparison.

Case in point, each technology has its ups and down, and the specific vehicle they go in is probably the most important factor about what to use.

Yup. I'm not averse to any engine architecture that gives me the power I want for as little weight as possible.
The LS V8 does lend itself to being swapped into smaller/lighter-weight cars much more readily than physically bigger DOHC V-engines.

And thanks to Camaro SS sales (nothing but donor cars to me!), there will be a good supply of LS3s and T6060 transmissions for some time to come

[ZDan]

Originally Posted by ottopilot

Buell's V-twin never came close to what ducati or even the japanese did with their dohc engines.

H-D air-cooled Vtwin not remotely a performance engine as previously noted. But it should be pointed out that the smaller/lighter H-Ds with those engines get WAY better fuel economy than similar size/weight Japanese bikes with DOHC/multivalve engines!
(and way way WAY better vs. sportbikes).

[rice_classic]

Originally Posted by ScionRacer

i can give them credit on is keeping the corvettes heritage in tact.

ScionRacer, I'm not picking on you directly but want to speak to phrases like this, "heritage".

When I hear things involving cars and car companies and terms like heritage or tradition, I kind of just check out. Usually when I'm hearing those words it's to disguise a company's lack of innovation, lack of imagination and desire to turn a profit by continually fooling the public into buying a "new thing" that's not actually new; it's just the same-ol' same-ol' wearing a new dress and new makeup. This just isn't a Pushrod vs DOHC debate, but my disappointment with American manufacturers in general.

And here's why.... Nothing by American companies gets done "just cuz" or "just for the sake of". It only gets done for profit. (Unfair and partially untrue over generalization used for making a point) Now living in America, we all think this makes sense, this is "normal". Well, it's normal to us and it also explains a lot. Other countries have a culture where things are done "just because", sometimes.

Examples:
Why is Ferrari... well... Ferrari? Because Enzo didn't make cars for profit... profit wasn't the goal. Ferrari only made street cars to fund grand prix racing and that's pretty much how their game is still played with obviously some changes but...

Another example is found from Toyota in this article:
http://wot.motortrend.com/toyota-gt86-engineer-upbeat-about-potential-supra-and-mr2-successors-291229.html

“So this is a new business model,” Tada said to AsiaOne.com. “When customers buy a car, it creates a new bond between the manufacturer and the owner – we do not just profit from selling the car.”

and

Tada claims the Supra and MR2 mark the automaker’s renewed focus beyond selling cars simply for volume and profit.

Show me an American car company with the fiscal balls to put anything like that in print!


So anyway, back to pushrods... at this point the types of technology than can be utilized in cars today is outstanding and Godbless GM for trying with the VOLT (and thank you taxpayers) but when it comes to the Charger, the Vette, the Mustang and the Camaro... It's all just selling the consumer.. "heritage" and "tradition" without ever having to really innovate, cuz what's more 'Mericun than Pushrods!

[Rayme]

Originally Posted by ZDan

H-D air-cooled Vtwin not remotely a performance engine as previously noted. But it should be pointed out that the smaller/lighter H-Ds with those engines get WAY better fuel economy than similar size/weight Japanese bikes with DOHC/multivalve engines!
(and way way WAY better vs. sportbikes).

I have a SV650s sports bike V-twin that averages almost 50 MPG. Are harleys THAT much better?

The best I ever heard of a Harley getting good economy was with the half engined Buell Blast which got crazy MPG.

http://www.fuelly.com/driver/noteczuki/sv650s
http://www.fuelly.com/motorcycle/buell/blast

[serialk11r]

Originally Posted by ZDan

Benefits of OHV cam-in-block design are pretty much limited to V-engine layouts, where there's a big valley with plenty of room for a camshaft and pushrods. Inline engines definitely want to be SOHC or DOHC.

Wait a minute, so there are definitely packaging advantages for OHV V engines, but what about weight? I was under the impression that these OHV engines have a single camshaft driving all the cylinders? In that case I guess a more fair comparison would be SOHC vs. OHV I guess? Neither has cam phasing ability that way.

[serialk11r]

Originally Posted by ottopilot

I have a hard time believing the "size" and "weight" argument is always valid as far as pushrods engines goes.

Considering motorcycles greatly benefit of smaller size and weight, I can't beleive one could take an inline 4, converted it to pushrod / 2 valves per cylinder, up the displacement and get a better engine still pushing almost 200 hp. It would be noisy/rattly and couldn't rev for crap.

Buell's V-twin never came close to what ducati or even the japanese did with their dohc engines.


Case in point, each technology has its ups and down, and the specific vehicle they go in is probably the most important factor about what to use.

I think perhaps the issue is that the benefits that DOHC has for higher revs is wasted on engines that don't rev any higher than pushrod engines.

[Dimman]

Cam phasing is way more limited on single cam motors (OHC or cam in block) since there is no overlap/LSA control.

It's something to note that for all GM's continuous work on the SBC, they don't use it in small motors.

[rice_classic]

Originally Posted by LSxJunkie

This idea (which, unfortunately, isn't completely untrue) that many American cars are sold on heritage and tradition does a great disservice to the actual capabilities of those respective cars. It suggests that those companies are simply resting on their laurels. They're not.

The Boss 302 is faster than an e92 M3 at Laguna Seca.
The Z06/Z07 went 7:22 at the Nurburgring.

If they were ONLY about heritage and tradition, neither of those cars would even exist. The Corvette would come in one body and feature lots of chrome accents and the Boss 302 would be a sticker and wheel package.

Lap times are not a measurement of manufacturers culture of innovation. You don't really need a great deal of innovation to go around Laguna or the Ring very fast. Neither of those lap times by either car suggests anything "innovative" in their design.

I also don't think they're necessarily resting on their laurels. I said they were "selling heritage" which is different.
So yeah, I don't think they just sit back and never change but I do feel they often rehash the same ingredients, slap on a familiar label and sell it as "Now you can own this iconic piece of history in this new 2013 model!" Bleh.

[LSxJunkie]

Originally Posted by Dimman

Cam phasing is way more limited on single cam motors (OHC or cam in block) since there is no overlap/LSA control.

It's something to note that for all GM's continuous work on the SBC, they don't use it in small motors.

Chrysler did OHV cam phasing differently. In the Viper V10, there is a camshaft inside of a camshaft, allowing the intake and exhaust lobes to move independently of each other, allowing the computer to adjust LSA.

Originally Posted by rice_classic

Lap times are not a measurement of manufacturers culture of innovation. You don't really need a great deal of innovation to go around Laguna or the Ring very fast. Neither of those lap times by either car suggests anything "innovative" in their design.

I also don't think they're necessarily resting on their laurels. I said they were "selling heritage" which is different.
So yeah, I don't think they just sit back and never change but I do feel they often rehash the same ingredients, slap on a familiar label and sell it as "Now you can own this iconic piece of history in this new 2013 model!" Bleh.

Innovation vs. Cost vs. Reliability vs. Results. You don't need the first to achieve the three latter, and it's just as innovative to be able to do more with less instead of throwing money at innovation for the sake of innovation.

And it's not like GM doesn't do innovation. GM invented magnetorheological dampers in the late 90s and were first seen on the Cadillac STS, followed by the C5 Corvette. Since then, GM has licensed magnetic shocks to pretty much everyone, including Ferrari. They were also the first to sell a car with a Heads Up Display(1988) and automatically dimming high-beams (Autronic Eye, 1952).


Also, lest everyone forget, GM also had a line of DOHC small displacement V8s. Anyone remember these?


Those two cars had 4.4L DOHC motors with roots blowers (because torque.) The STS-V made 469/439, but only wound out to 6700rpm. The XLR-V made 443/414. This line of motors was killed because the take rate was low, the cost to continue development was high, and nobody wants a DOHC Corvette because they're a bitch to make cheap power with.

That brings me to another point.

How much money does it cost to take a BMW S65 and make a safe 540hp that you can hammer during 30 minute sessions? Somewhere around $20k, if I recall correctly.

In an LS3, that's a cam, headers, valve springs, and a tune. All told, $5k with labor. And there is no need to run aftermarket piggyback fuel management because GM Powertrain Control Modules (PCMs) are completely unlocked. All you need is a cable and EFI Live or HP Tuners (plus credits) and you have complete access to fuel maps, spark tables, timing tables, and everything else in the PCM. If you want to make relatively cheap, reliable power, there is no other way to do it.

[serialk11r]

Originally Posted by LSxJunkie

How much money does it cost to take a BMW S65 and make a safe 540hp that you can hammer during 30 minute sessions? Somewhere around $20k, if I recall correctly.

In an LS3, that's a cam, headers, valve springs, and a tune. All told, $5k with labor. And there is no need to run aftermarket piggyback fuel management because GM Powertrain Control Modules (PCMs) are completely unlocked. All you need is a cable and EFI Live or HP Tuners (plus credits) and you have complete access to fuel maps, spark tables, timing tables, and everything else in the PCM. If you want to make relatively cheap, reliable power, there is no other way to do it.

Well to be fair, the S65's ITBs are probably very difficult to control, but it's not like you can argue ITB=worse for that reason. If they wanted they could've made it simpler, but then it wouldn't be as neat of an engine. The cheapest method of adding power is always bigger displacement, but just doing that doesn't get us anywhere in terms of technology.

Also, the weight you quoted for the S65 might be a start stop equipped S65, which adds like 10 pounds or something, and I think start stop motors are considered part of the engine at least for quoting service weight.

If Germans were more liberal about adding displacement (well rather, if BMW were, since Mercedes doesn't seem to have a problem with sticking 6+ liter engines into cars) I think the S65 could be a close to 500hp stock engine.

[dorifuto]

Gm dosent liscence magnetic suspention to anybody. Delphi the gm division responsible for the technology was sold to the damn red Chinese.

[rice_classic]

Originally Posted by dorifuto

Gm dosent liscence magnetic suspention to anybody. Delphi the gm division responsible for the technology was sold to the damn red Chinese.

Oh Snap!