PCCI is a variation on the multiple-event direct-injection diesel concept, with the most significant attribute being a substantial injection event that precedes the actual desired ignition event (some modern diesel use a small "pilot" injection event prior to TDC, but this doesn't achieve quite the same effect). You don't get the homogeneous charge that is the hallmark of the HCCI process, but the partially-stratified charge does tend to minimize the NOx and particulate emissions while being perhaps somewhat easier to control than the HCCI process.

The disadvantage is that this all still pretty much requires a diesel-like engine, with the brick-sh*thouse bottom-end and expensive high-pressure injection system. I believe that it also still would require diesel fuel, which for the foreseeable future will remain our most-demanded liquid fuel (one advantage of HCCI is that it could run on a variety of lighter distillates, included gaseous fuels). PCCI does show some promise in reducing the amount of exhaust aftertreatment, however, and that alone is significant enough to make it interesting for all those applications that will require diesel-like fuel economy and performance (including, at least, trucks of all sizes).

 

BMW?

Aside from building the 6.0L V12 that was used in the McLaren F1 and a couple other very low production speciality cars, I'm pretty sure that BMW engines have only ever been found in BMWs.

 

They are taller and wider, but they're not as long (bore spacing is 11mm smaller, which is one reason why mod motors max out under 6 liters, while LSx has room for 7 liters and beyond). They also have less bulk between the cylinder banks, because there's no cam or associated hardware in there.

A DOHC 4.6 isn't significantly lighter than an LS3. It's like a ten pound advantage, which doesn't even come close to being worthwhile considering the LS3's lower cost, better packaging, better fuel economy, and better power. In fact, I haven't seen conclusive evidence that it's lighter at all, with all indications being that the LS3 weighs in around 440, while the all-aluminum DOHC 4.6 weighs in around 470.

I could see this argument being valid if the 4.6 was 100+ pounds lighter, but that's simply not even close to the case.

Details? I'm assuming you're not referring to the 6.1L Hemi in the SRT cars...

I don't see transmissions as a commodity item. In fact, the transmission's characteristics are just as critical to me as the engine's with respect to a car's "personality".

True, but the OHC motor also takes up more space, which usually means it will be of smaller displacement. Example -- Ford went from a 5.0 pushrod motor to a 4.6 OHC, and there was a lot of extra room in the engine bay with the 5.0 that isn't there with the 4.6.

Also, peak power isn't the only thing that counts. I'm not talking about power under the curve, either (OHC engines typically beat pushrod engines across the board) -- I'm talking about reliability, complexity, maintainability, cost....

 

can you back that up?

 

This is pretty basic - for a given displacement, the advantage goes to the engine that can spin higher. And for most automotive engines (that it, engines with a displacement of less than ~7L), pushrods will limit the engine's speed before mean piston speed becomes an issue. Or at least that's the case if you're engineering things for 100,000 miles

Having said that, most passenger car engines never go over 6000 RPM, and controlling a pushrod valvetrain at that speed seems to be a fairly well-understood science (although it's probably soon progressing to the "lost art" category).

 

The overhead cam 4.6s are in a ton a vehicles and I can select quite a few different models to pick parts off from. I could throw the timing cover and top end off a 03/04 Cobra on my car if I really wanted to.

The way they limited the cost was to spread the engine over a large market of vehicles such as the F-150, Marauder, Aviator, Navigator, Cobra, Mustang, Thunderbird, and Crown Vic.

If you are producing the same basic block for each of the vehicles it becomes much cheaper.

I do agree that my motor would most likely dwarf even any big block engine, lol. I have to start comparing the actual dimensions to cruise liner motors.

 

Nicely written.

And 6000 rpm and 100,000 miles is a long way from the 9000 rpm and 500 miles that the NASCAR engines need to endure.

 

Yea and you took a familair position on things as well.... not to call the kettle black or anything.

All in good fun.

 

So is the argument that because piston speed can be higher on a OHC motor it has to make more power? The 4.6 sucks Ford themselves were looking to replace it and return to a pushrod design a few years ago but then they ran out of money. Ford should have improved on the 5.0 design like GM did with the LS1.

 

Really? Care to back that up?
I'm always open to learn something new.

 

I think sups is still under the impression that the 'Hurricane' motors were OHV, as many thought for a long time. I could be wrong though.

 

No, the argument is that for an engine of a given displacement, I need to spin it as fast as possible to make the most horsepower. Ultimately, this maximum usable engine speed will be limited by airflow, or by piston speed, or by valvetrain stability. OHC leads to better valvetrain stability, so it addresses at least one of those three.

Of course, OHV vs. OHC means nothing if the engine is airflow limited, or if the desired operating range never brings the engine past the point where valve control becomes an issue. Frankly, most consumers never rev their engines to the point where OHC is required, but then again, most car buyer decisions have little to do with "need"

 

Since the LS1's inception in 1997, LS engines have been available as either standard or optional engines in the following cars:

Chevy
Camaro
Corvette
Impala
Monte Carlo
SSR
Trailblazer
Tahoe
Suburban
Silverado
Express

Pontiac
Grand Prix
GTO
G8 (soon)

Buick
LaCrosse

Saab
9-7X

Cadillac
CTS
Escalade (including EXT)

GMC
Envoy
Sierra
Yukon (including XL)
Savana

Hummer
H2 (including SUT)
H3

That's 23 (or 26, depending on how you count it) models, and I didn't even include any of GM's non-North American brands (Opel, Vauxhall, Holden, Daewoo). I might have even missed some north american cars, I'm not sure.

Saturn is GMNA's only brand that doesn't offer an LS engine.

Some of the models I listed are available with a number of different LS engine options.

My point? The fact that Ford spreads the mod motor across several vehicles is not unique or special. In today's market, such a practice is practically mandatory!

The other advantage to OHC (and in particular DOHC) is that it greatly simplifies the engineering involved in variable valve timing and lift systems. Variable timing can be done with a pushrod motor, but it's only available on the market with the newest-generation Viper, so I can only assume that it's difficult, expensive, unreliable, or a combination thereof. I have yet to see a variable lift system on a pushrod motor of any kind.

 

GM's 6.0L, and 6.2L truck engines.

GMPowertrain

I'd still agree that it's easier on OHC setups...

 

GM's had VVT on their V6 and V8 pushrod motors for a few years, and the Hemi also has it now.

The thing that's special about the Viper is that it can vary the intake and exhaust timing independent of each other. GM's system simply phases the whole camshaft so intake and exhaust get the same timing change. Supposedly that's good for about 80% of the benefits of an independent VVT system.