S1 vs S2 Debate (SPLIT FROM INTERCOOLER THREAD)
 

2.97. But you're forgetting the S1 is more of a low-end torquer than the S2.

I don't rev as high, I don't shift as high, and my hp and tq peaks are at lower rpm's than yours.

In a nutshell, this is why I need the biggest jump to the 1/8 mile I can get to keep my lead by the 1/4 when racing S2's.

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GM used to have both graphs on their drivetrain site, but I haven't seen them in awhile. I do recall very vividly how much flatter the Tq curve is on the S1 though. And for good reason.

The M62 rotors are much smaller in diameter. Same length, 3 lobes, 60° helical twist, but smaller in diameter and lighter. This means they spin up quicker. Anyone that's driven both cars stock for stock or similar mods knows how quickly the S1 SNAPS into full boost. There's a profound difference. This gets the S1 into boost and it's tq peak at a much lower RPM:

92/93 = 260 @ 2600
94/95 = 275 @ 3200
96-03 = 280 @ 3600

Now imagine how this plays out at the track. The S1 will get off the line quicker, but then the S2 hits it's tq peak, pulls, then gets into the hp peak at a higher rpm, making more out of each gear with nearly identical gearing. Holding a gear longer at higher rpm's is a function of lighter rotating internals in the motor design (very much different than the S1). Another odd factor that most people don't know about is the 94/95 L67 actually has a SLIGHTLY larger throttle plate when compared to the Series 2 L67.

This is why the 94/95 L67's will typically match or slightly edge the S2 L67 in stock form (particularly the heavier 2000's). Into the boost and tq quicker but with almost the same torque peak (only 5ft/lbs off between the two, but the S1 is into the peak 400 rpm's sooner), and still producing 225hp in stock form. Only a 15hp difference, but they got the jump off the line due to the tq. Nearly equal on the quarter, S1 advantage at the 1/8, and the race would be owned by the S2 if it went to the half mile. Trap speeds would be killer too. ;)

The long and short of it is the two motors were designed very differently for two different effects. The differences are PRIMARILY the mass of the rotating internals and the mass of the rotors in the SC. They both produce the same CFM at a given RPM, but only because the 62 is spinning faster to do it. But the 62 requires less hp to drive the smaller 'charger.

The M62 robs 8hp at 4000 rpm's to produce 10psi, and about 5hp to produce 5psi at 4000 rpm's.

The M90 takes an even 10hp (2 more) to produce 10psi at 4000 rpm's, and about 6hp (1 more) to produce 5psi at 4000 rpm's.

Taking it out farther, the M90 requires 42hp to spin 12000 rpm's at 10psi, where the M62 only requires 35 to do the same.

What's the difference? Both were intended for our displacement. They just overlap for the application. The M62 was designed for 2.0-4.0 liter displacement engines, where the M90 was designed for 3.0-5.7 liters. Both work, you just pulley them differently.

The M62 makes it's boost without using as much hp to drive the supercharger as the M90, but at a cost. It's smaller, spins faster, and produces more heat in doing so, causing efficiency to drop off at the top end a little quicker.

I could go on for another hour here, but I think I'd lose the audience. These are just some explanations for why the Series 1 performs so well at the bottom end, and the Series 2 is a little better from mid-trap.

Please explain.

Last time I checked, increasing rocker ratio shifts the peak up, but not the rpm delivered. It takes a cam (in general) to shift the powerband itself.

Here's a different way of looking at my sermon a couple posts up:

Attachment 33669

Aren't we getting off topic?

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Why is this becoming a S1 S2 discussion?

S1 stock dynos are gonna be damn near impossible to find, so we gotta go by vehicle performance.

Bill didn't say the SC's produce the same PSI at 12000 rpm.

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