Engine Tech

What do you prefer?

S/C'd 6.2L OHV V8. 6500rpm redline
10:1 compression
755 HP @ 6300rpm
715 lb-ft @ 4400rpm. 600 lb-ft available from 2200 to redline
14 psi boost from 2.65l Eaton TVS
2HP per cu in

S/C'd 5.2L DOHC V8. 7500rpm redline
9.5:1 compression
760HP @ 7300rpm
625lb-ft @ 3000 to redline
12 psi boost from 2.65l Eaton TVS
2.4HP per cu in

I'll take option 2. lower boost and rpm left on the table... just a tune away. You dont need tons of torque to go fast, give me the HP.

I wonder what power the 6.2l would make stock if revved to 7300 rpm.

Also wonder what the blower speed is at redline for both motors...

First. More hp/tq down low and given I know what the car is, it’s significantly lighter weight.

This wasnt a car comparison.. just engines themselves.

The ford dohc is pretty damn efficient mill (which we've known)

Blower speed for the LT5 is 15,860rpm at red line.

R2650 is rated for 18k max rpm.

WOW!

There's much, much more to the discussion and I'm aware of that but it is interesting the engine with more displacement, more compression, and more boost makes the same power. You could say the LT5 has more untapped potential then, but considering 93 octane is the level playing field, idk...

Now, if we really want to nerd out, we'd probably need to discuss what the cam looks like on the LT5. You need more static compression with a fat cam because the overlap is going to bleed a lot of that compression off. The Voodoo motor, with Ti-VCT, doesn't have this problem since the cam overlap can be modified. I think that's where the fun part of this discussion lies, the rest of it is pretty trivial.

Not trivial to me!

I'm guessing the LT5 with even a 7300rpm redline alone would make very close to 800hp right out of the box.

Would have to look at some dyno charts to see what hp curve looks like

Cam does play big role but 14psi boost is 14psi boost.

The LT5 Cam is also variable but done differently (I'm not up to date on how it's done, haven't read up on the specifics).

It would be interesting if u could spin that LT5 up to 8k but it is a pushrod setup unless it's built like a NASCAR engine it's not revving up there.

I'm biased, and I'm picking the LT5 as my ZR1 should get to my dealer sometime next week.

Tony

Cman01 said:

The LT5 Cam is also variable but done differently (I'm not up to date on how it's done, haven't read up on the specifics).

It would be interesting if u could spin that LT5 up to 8k but it is a pushrod setup unless it's built like a NASCAR engine it's not revving up there.

I'm biased, and I'm picking the LT5 as my ZR1 should get to my dealer sometime next week.

Tony

Click to expand...

It is variable, but the whole cam has to be advanced or retarded, right? I wouldn't think you could advance / retard intake and exhaust independent of each other on a pushrod cam.

Like I said, I know it has variable cam timing but how it does it I'm not sure.

Once I get my car and a SM I'll look it up and get back to u.

Voltwings said:

It is variable, but the whole cam has to be advanced or retarded, right? I wouldn't think you could advance / retard intake and exhaust independent of each other on a pushrod cam.

Click to expand...

This is correct as it pertains to GM, however Dodge uses a cam-in-cam design that allowed independent exhaust and intake valve adjustment.

Here, I found this article describing all the stuff on the ZR1 LT5 engine. There's a little blurp about the cam and how it does the variable thing.

Know the enemy as they say:

755hp from the inside out, supercharged C7 ZR1 LT5

Easily option 2 for me.
Add 4psi and rev it out to 8200rpm and you’ll see 900hp.
Plus forget pump gas, but less compression and more rpm better for detonation.
The engine with the better flowing heads but more importantly VCT will win this.
-J

Hope that DCT lives after u pulley down, and no need to rev up to the sky with the torque the LT5 puts out and that engine can make those #'s and more easily and proven done already in a lighter and better aero package.

Well moving forward it looks like top GM and Ford Performance vehicle will be DCT only, and Tremec is throwing their reputation and future into the DCT so we will see, but I’m confident.
Higher RPM is always best for performance, especially boost. Not like we’re not towing here.
Not sure why you’d think the LT5 has more potential than the Predator 5.2 with the same blower. Even stock the 5.2 is making more power on less boost. The DOHC, 32V and VCT just too tough to beat.
-J

We don't know what the predator can make yet till it comes out and people start tinkering, tinkering has already begun a year ago on LT5 and they can make BIG power and torque without needing the revs to do it (if you build the engines it probably could rev higher...…….not predator high but it doesn't need to go up there but I'm sure you could get it to spin to 7k no problem over the stock 6500rpm redline).

There's not that much difference in the power stock between both engines (5hp more than LT5 with only 2 lbs. less boost but there's a whopping 90lbs/ft more torque in the 5 over the 5.2).

True, it is very interesting how close both engine outputs are stock, despite the different design.
I really like the LT5 and the LS family, so this is not just fan boy talk. I’m just saying which I prefer and which has more potential with the same supercharger.
BTW I absolutely love the ZR1 you have coming. One of the few cars I’d trade my GT500 for.
-J