mini zr-1? 4 cam 24 valve 300 hp

[BOB HDZ]

has any one seen the new mini?

[Aurora40]

Are you talking about the GM corporate "high feature" OHC V6? I don't think it has any real relationship to the ZR-1.

[BOB HDZ]

yea there putting these in the new camaro base car. and cadillac

[Paul Workman]

Originally Posted by Aurora40

Are you talking about the GM corporate "high feature" OHC V6? I don't think it has any real relationship to the ZR-1.

Yeah, but I think Bob's point was the DOHC approach, and not so much the LT5 specifically, yes? W/ the new fuel economy regs on the horizon, it seems apparent that GM was going to have to consider a return to a 4-valve DOHC config to get any kind of performance from small displacement/efficient motors. Whenever doing a side-by-side comparison, the multi-valve, OHC config kicks butt. I drove a little Aveo for a bit; had a 4 banger w/ a DOHC/16 valve in it - damn thing surprised the hell outta me - would really scoot!

I'm betting we'll see more OHCs or DOHCs in the future from GM and others. Ford (for one) has really pushed that OHC concept out quite a bit - even pick-up trucks have 'em. When a N/A 4.6L Mustang makes ppl at an "all Corvette" drag event sweat bullets where none of the Vettes are packin' less than 5.7L pushrod motor, or Pete rubbin' shoulders with 10 seconds using a N/A 350 LT5, it seems to the casual observer that the only way to get comparable power from a 2-valve pushrod is to go to the cubic inches well again.

I'm not making a point except to say that it seems like stubborn tenacity to look a better technology in the face and continue to "drive a square peg in a round hole" (so to speak) with push-rod motors - especially in their flagship car; the Corvette. Ponder what 6.2L Northstar motor might make...for example

Just rambling.

P.

[tomtom72]

I was watching one of the episodes of that Ultimate Factory series over the weekend and almost fell over when they showed the new base V6 for the camaro.

Watching them build the motor; I thought I saw some genetic connections to our LT5's. I could be wrong.

Made me think what would direct injection do for an LT5?

To Paul's point of the square peg in the round hole....looks like hind sight may be 20/20 in the "it's to expensive to mass produce " vein. Where would the GM DOHC development be by now if a different decision was taken back in the late 80's.....they beat Ford to the punch and then gave up.

[scholtmj]

I don't think it'll be too long before GM creates a direct injection V8 with DOHC and cam phasing. Everything is already made, they just have to put it together and package a lightweight car around it. C7 Vette?

[BOB HDZ]

i think that will happen to !!!

[Aurora40]

Originally Posted by scholtmj

I don't think it'll be too long before GM creates a direct injection V8 with DOHC and cam phasing. Everything is already made, they just have to put it together and package a lightweight car around it. C7 Vette?

GM has already dropped this idea. They had the opportunity to redesign the Northstar and decided not to. The current Northstar will likely fade away soon too, as soon as they drop or replace the STS and DTS.

I guess I'm not following the point of the thread. GM had DOHC motors before the ZR-1. Oldsmobile's Quad 4 came out in the 1980's. They've had DOHC V6's since about 1991 with the 3.4L "Dual Twincam" and then the shortstar Olds V6. There was also a euro DOHC V6 which I believe the current "high feature" engine was derived from. The latest 300hp version is just an evolution of that.

It's not some huge change in direction for GM, unless you mean installing it outside of a Cadillac. That might be more a factor of there being no other decent V6 anymore. GM killed the Buick pushrod motor, so what else would you put in a car as heavy as a Camaro or G8? That crappy narrow-angle pushrod V6 wouldn't cut it power-wise. Nor cost-wise when you consider a base Camaro still stickers for 23 large. By comparison with previous gen Camaro, you could just about buy a stripper Z28 for that much.

[Aurora40]

Originally Posted by Paul Workman

I'm not making a point except to say that it seems like stubborn tenacity to look a better technology in the face and continue to "drive a square peg in a round hole" (so to speak) with push-rod motors - especially in their flagship car; the Corvette. Ponder what 6.2L Northstar motor might make...for example

Just curious, why do you use the quantifier "better"? A large displacement LS motor is physically smaller than a small-displacement Northstar.

And in the Corvette vs XLR, the base 'vette motor makes 430hp to the XLR's 330hp. The XLR gets worse economy at 15/24 EPA vs 15/25 EPA for the automatic 'vette.

The Northstar block was initially designed for a max displacement of 5.4L (I recall reading this ages ago, I can't back it up with the actual article). If you did the math, that would put it at roughly 390hp. Still a lot less than the 'vette, and presumably fuel economy would drop further.

I fail to see how it's "better" simply because it is OHC or because it uses less "displacement". What is the downside associated with displacement?

[Paul Workman]

Originally Posted by Aurora40

Just curious, why do you use the quantifier "better"? A large displacement LS motor is physically smaller than a small-displacement Northstar.

And in the Corvette vs XLR, the base 'vette motor makes 430hp to the XLR's 330hp. The XLR gets worse economy at 15/24 EPA vs 15/25 EPA for the automatic 'vette.

The Northstar block was initially designed for a max displacement of 5.4L (I recall reading this ages ago, I can't back it up with the actual article). If you did the math, that would put it at roughly 390hp. Still a lot less than the 'vette, and presumably fuel economy would drop further.

I fail to see how it's "better" simply because it is OHC or because it uses less "displacement". What is the downside associated with displacement?

You're playing "devils advocate" ain't cha Bob? OK...I'll play along

Isolated anecdotes aside, generally...

• the flow thru of a 4-valve design is superior to the (practical) two-valve
• OHV means less valve train weight, allowing for reduced spring tension which relates to less wear for any target peak rpm.
• The burn characteristics of the pent-roof chamber in the DOHC (e.g. LT5) allows for very fast burn rates which allows compression ratios of 11:1 on 87 octane, and higher (12:1) ratios on 93 octane. Higher compression ratio = better power and efficiency (apparently).
• Intake and exhaust cam phasing (DOHC) can be independently and dynamically controlled "on the fly" to optimize output/efficiency for any load/rpm circumstances
• Sustained high rpm operation (again due to simplicity of the valve train) favors the OHC/DOHC in actual practice (but you already know that).

So, from a cubic inch to cubic inch, or hp/volume, or a dynamic load capability point of view, it is hard to argue the virtues of a single cam, push-rod approach as being anything but a little archaic in comparison.

After the 2-valve flow has been optimized, the only door available to the daily-driver, push-rod motor to keep up the horsepower is displacement.

If I give you physical size in favor of the push-rod as a "given", I really don't have to explain further why the OHC/DOHC is a better design, do I? (Jess pullin yer tail a little, Bob )

P.