Runge_Kutta

OK, let's look at the two different 3V head designs that use
a single internal camshaft. I am reasonably sure that the LS3
will use a variation of what is shown in patent 6505589 but
I wonder what the valvetrain will look like. From Figs. 1
and 2 in 6505589, you can see that the head is designed
for direct injection from the top of the combustion chamber.
Patent 6505591 details an intricate way to simultaneously
actuate the exhaust valves while maintaining space for
the DI at the top of the combustion chamber. Patent
6668546, Fig. 5, shows the combustion chamber of both
the single and dual internal camshaft designs from a
ways back.

http://www.freepatentsonline.com/6505589.pdf (DI port is #68 in drawings)
http://www.freepatentsonline.com/6505591.pdf
http://www.freepatentsonline.com/6668546.pdf (Look at Figure 5)

Here's the new valvetrain. As you can see, there is no longer
any place to put the central injection DI injectors.

http://www.freepatentsonline.com/6962134.pdf

This could mean many things. First, that no 3V head will
get central injection. It could also mean that there will
be a DI version and a non DI version of the heads. Lastly,
GM could have decided to abandon low pressure, air assisted
DI for high pressure side injection.

Someone needs to spill the beans here ...

Also, DaimlerChrysler is also in the OHV 3V business

http://www.freepatentsonline.com/6895925.pdf
http://www.freepatentsonline.com/6964252.pdf

as is Ford

http://www.freepatentsonline.com/6267096.pdf

A-man930

iTrader: (2)

Friggin' sweet!...

chuntington101

i dont like the second cam! i know it would enable better inlet and exhaust setup and timing (similar to DOHCs) but adds a lot of complexity over a single cam design. stil a nice setup though

goodfind though mate

Chris.

J-Rod

Good to see you posting Runge_Kutta.

To anyone else. If you take the time to read his posts on Corvetteforum, they are pure gold. Definitely read anything this fellow posts. He has a knack for "finding" all sorts of neat info.

FieroZ34

iTrader: (1)

I know this is against everything GM stands for, but it's time. GM has taken pushrod technology to heights I never thought it could go. But, why waste the time and money on a 3v when they can just do it right already, DOHC, 4 valves per cylinder? The advantages are obvious and undeniable, the dissadvantages minimal. Cost, size, and weight. The cost is no more than developing the 3v, probably less because they've done the whole DOHC 32v thing twice before. Size is not an issue really, as the Vette and F-bodies are more than large enough to accomodate the massive heads/cam towers. So last is weight. It will weigh more than a LS1, but I wouldn't be complaining when you're getting 600hp from 5.7l, in a streetable, warrantied, package that is as civil, if not moreso, than the LS7.

Just my .02, but every few years GM takes pushrod technology one step further. But why? BMW has an engine making the same amount of power as the LS7, with 2l less! That's a lot!

hellbents10

iTrader: (10)

A lot of good points there. The BMW does make the same overall hp as the GM, but average hp and torque numbers over a givin rpm range are less. So that being said the motors physical demension is smaller, its lighter and will be faster and even get the same or even better fuel econimy. In two identical cars of coarse. Still it never hurts to move forward. I still like the pushrod motors for much the same reasons a lot of people on here do.

Its cheaper to build and cheaper for me to play with a make a lot of hp's
Its generaly lighter givin the hp level.
Its generaly smaller giving the hp level (physical outside dimensia)
Its simple and provin.

Thats why I still love GM motors, look at them in compition agianst some of the "more technilogical" motors in racing. The corvettes have been wining.

TAEnvy

iTrader: (2)

Dont forget the Bimmer is without a doubt far more expensive to build than the LS7. I mean each cylinder on the 5.0 BMW V10 has its own throttle body and not to mention it revs to like 7750rpms IIRC. The BMW also "only" makes 384ft-lbs compared to the LS7s 470 which without a doubt comes from the LS7s extra 2litres of displacement. Im sorry if some of my facts are wrong they are all from memory.

chuntington101

i think the BMW M% engine is not the best comparision to the LS series of engine!

try looking at Merc new 6.3ltr V8! a very nice piece of kit.

thanks Chris.

baldurann

iTrader: (15)

It's tough to compare an exotic, low-displacement, multiple valve DOHC motor with ITB's and one of the sickest exhaust manifolds created, to a high-displacement, single TB 2v OHV motor with a baby camshaft. Add ITB's and "better" flowing exhaust manifolds, and a different camshaft to take advantages of these additions to the larger-displacement motor, and you'll blow the BMW motor out of the water, power-wise. Displacement is displacement, and when you add a set of phenomenal flowing heads with a badass intake manifolds (although it uses only 1 TB), it will be pretty darned hard to beat, power-wise.

J-Rod

You've glossed over so many facts here it isn't even funny. I would encourage you to do a bit more reading and educate yourself before making such generalizations, especially those that are patently wrong.


First off the whole cost/size/weight. Gm just did a fire sale on it remaining stock of LT5's they were still over $12K for a crate motor, and this was a discounted price. My buddy has one going in a street rod (they bought 3 of them). Trust me when I say they are a miracle of packaging, but they are still bigger and heavier than an LS1, and the intake will just barely clear the hood of the Corvette, where an LS1 fits fine.

Yes, if you develop a package you can spread over multiple product lines, the costs can come down. But with the large szie constraints brought on by a multi-cam multi-valve head, you eliminate certain cars by default.

The Vette and the F-Body in FACT do not have room for a multi-valve/multicam motor. This has been documented NUMEROUS times by GM. There are advantages to multi-cam multi-vlave motors. But there are also advantages to OHV motors. You might even want to look in a few thread in this section where those two points have been discussed.

Its not that GM is against DOHC motors. They built the LT5. They currently run the Northstar. They built the Ecotec. But, I was around when the LT5 was new, and the first GenIII mules were roaming the street. GM was able to make the target power levels with a motor that was lighter and cheaper to build. It also could use that motor across other lines (Like trucks) to spread that cost. It doesn't take a rocket scientist to see which way that is going to go.

Anyway, this has been covered ad nauseum. Do some reading...

hammertime

iTrader: (1)

Not that DI isn't noteworthy, but I think figure 2 & 3 are the most important points here. What an innovative way to get most of the benefits of DOHC, without the added complexity of the massive dual chain drives, four camshafts, twice as many components required for Variable Cam Phasing, etc.

This also appears to get rid of the mass of the linked rockers, best shown in the first link in figure 5.

So it's still a pushrod motor - it obviously shows that GM has not run out of improvements for this architecture. By and large, the majority of these would end up in trucks and SUV's, so we need not worry about what benefits true DOHC might offer at higher engine speeds.

FieroZ34

iTrader: (1)

It is a pet peeve of mine when people say that DOHC 4 valve motors are only good at higher RPM. What a completely ignorant statement.

hammertime

iTrader: (1)

I assume you're going to tell me how much better off we'd be with DOHC 4 valve LS3's, despite the added cost, complexity, and lack of space for it in passenger cars. If GM followed Ford's lead and did away with OHV engines, you can bet we'd never have the Grand Prix GXP, Impala SS or Trailblazer SS.

If its that 'simple' to get 600hp from a totally streetable DOHC 4 valve V8, why is Ford using superchargers on the GT and Shelby GT and still falling short?

hammertime

iTrader: (1)

Wikipedia on DOHC
Datsun.com tech on 2V vs. 4V
Fortunately, I'm not the only one to ignorantly believe that DOHC 4 valve engines make more power at higher rpms...
My original statement only mentioned its advantage at higher RPM's, never said it had no advantages.

redfulcrum

DOHC is a rip off. I totally disagree with comparing the m5's motor to the LS7. LS7 beats it hands down. M5's powerband doesn't compare to the LS7s. Have you seen how massive BMW motors are? DOHC always calls for added weight. Look at the Mustang DOHC engine, it's got huge heads and I still haven't seen flow sheets that are any better than LS1. What's the point of having 4 valves and still can't outbreath a pushrod engine. That's another thing, what's up with all these 4v motors that can't go over 6500rpm. What is the point of having it? It's just wasted bragging rights technology. Foreign cars use less liters because of taxes in foreign countries, they're forced to try to make more power from smaller displacement. You can make all the horsepower in the world by revving, but it's going to cost alot of money. That's why GM stuck with OHV, money to power ratio is better. It's expensive to mass produce an engine that revs to 8000rpm, and have it go in SUVs and Trucks. It might be easy to rev that high in little honda motors, but pushing a huge motor to do that with a stroke around 4.00 is going to be really tough and expensive for OEM. Powerband is another thing. That's why you see so many S2000s at Carmax. When people first heard of the s2000, they were impressed with 240hp. This was an era when high revving oem cars were a new thing. I guess they were expecting it to have some low end torque. They were really disappointed with the peaky engine and traded them in. There is no other way to get low end torque without displacement or force induction. You definately don't need high revving trucks. It's useless for the majority of drivers. Don't forget about the general population. If I were GM, I would focus more on force induction rather than high revving motors. Another thing is fuel economy, I don't think there are any V8s that get better fuel economy than gen III and gen IV motors. They always claim that DOHC gets better fuel economy, but to me it seems worse when there are 4 cams and more valves to turn. There's only two ways to increase CFM naturally aspirated, either you increase in displacement or rev higher. Displacement will always have a better powerband over high rpm engines. It will have more torque. The loads are going to be less. Requires less manpower to design and make. I could go on, and on, and on. You can't just go out and say this 5L motor makes 500hp and this 7L motor makes 500hp also. There are clearly more variables here than just peak power. Does anyone else agree with me?

Money is the biggest factor, I don't doubt GM's ability to build an engine. When the Gen III motors came out, who dominated the 24 hrs of Le Mans?

Kenova

iTrader: (4)

Ah yes, the old OHC vs. Pushrod debate. For me, size does matter. The Northstar and Ford Mod motors are just too f*****g huge for the amount of torque and horsepower they produce. But hey, that's just my uneducated opinion. If I can get more displacement and/or power out of a smaller package, I'll take it in a heart beat.
Trying to get back on track with the original post, these three valve designs look like they would be easy work on and modify. The extra mass of an extra rocker and pushrod may be a concern at higher revs however, but I'm sure someone will find a way to overcome any problems.
I believe the one thing that will have the most influence on which design is chosen will be Direct Injection. GM already has a four cylinder running DI, and with good results. It is only a matter of time before this technology is applied across their entire engine lineup.
Bring it on.
Ken

Ari G

iTrader: (25)

The V10 5L BMW motor is not making such increadlible power as everyone is thinking

They:
Spin higher,have variable valve timing(Vamos),4v per cyllender,Tb for each runner ect..

ok,they make 100hp/L but the LS6 makes 405hp at 6000rpm,allmost 2000rpm lower with pushrods,now that´s not bad at all

Now put tuned runner length.Vamos,4v per cyllender,Tb for each runner and a matched low bacpressure exhaust with headers on the LS6

machinistone

Aside from the fact that the mod motors are large and complex, they do make good power per cubic inch in stock form, they just don't respond well to simple upgrades like cams and ported heads like the GenIII/IV chevy's do. 305hp from the early 4.6L 4V and 350hp from the Corvette LS1 is the same power per cube. The blown cobra motors make more per cubic inch than the LS7 at 1.4hp/inch vs 1.2hp/inch. They are making up for a lack of cylinder displacement with forced induction, and those little 4.6L motors love boost, 650rwhp from 281 cubic inches on a stock motor is not something to laugh at...

That being said, I would prefer to see chevy jump past the 3 valve thing and just go straight to 4v OHC, spend the money to engineer a nice efficient, compact package rather than following the way of all the import motors and just being 10 years behind them in the process to a 4v setup. Just look at the generations of honda motors through the years and you will see that this all looks very similar, just late in the game.

redfulcrum

You can't compare FI engines to NA engines. I wasn't saying the cobra's motor was bad, I'm just saying there's not much of an advantage going DOHC and having small liters as opposed to going with bigger liters and using 2 valves. If you had 2 engines making the same peak power with the same PRESSURE RATIO, but differs in displacement, the bigger engine would be the better deal. I would rather stroke my engine and keep the same rpm rather than trying to rev 1500 rpm higher with a crazy radical cam that i need to baby all the time, change valve springs every couple of months, drive only on weekends and such.

I don't think 650hp from a 281 is impressive anyways, especially if the manifold pressure is increased. I've seen turbo kits for the LS1 under 2bar making more power.

What about costs? Do you prefer to buy 32 valves and 4 camshafts when you're upgrading? OMG, don't even think of buying 8 throttle bodies. You could probably buy a built long block for that kind of money. That's just nuts. No wonder GM stuck with OHV for so long. All that crap sounds good when you're racing professionally and you need to stick to small displacement rules. But for the streets, there's a better way to get more CFMs, especially in the US, either big inches or forced induction. Why do people always want to NUKE things? GM knows what they're doing, even though people are getting laid off. It's just plain old economics.

machinistone

Agreed.