oicw

You're exactly right, which is why I added a very important bit after my statement:

"Of course for such a condition to occur, the engine must electronically or physically "rev out" before 5252."

So if we imagine that ZR1 had a rev limiter at 4500rpm, then it'll make 450hp and 520 lb-ft of torque. But then after thinking twice, like you mentioned yourself, any engine has to make more torque than hp if it doesn't rev to 5252.

DoctorV8

I remember it well, and actually did reference it in post #15.

The evolution of the L98/LT1/LT4/LT5/LS1/LS6/LS2/LS3/LS7 clearly illustrates my point of how improvements in airflow, and therefore peak power, have gradually moved peak torque up the RPM scale, with peak HP eventually exceeding peak TQ in the LS motors, and moving up the RPM scale.

stevebz06

Sorry I missed your post, but I was just trying to make a point to the folks who apparently do not believe it is possible to have an engine that peak hp is less than peak torque. I think that there is a misconception (which should be dispelled by this thread's readers by now) that there is a disconnect between hp and torque. The reality is that horsepower is simply derived from measuring torque and then applying a simple formula.

The increase in useable rpm range in the Chevrolet V8 performance engines has not been a constant over the years. They had performance engines that revved to 7,000 rpm in the 60's. I think that maybe the switch to tuned port injection had more to do with the fall off than the ability to make engines that rev.

The thing about OHV design that is limiting is its' ability to produce high revs and still maintain valve train control. 7,000 seems to be about the limit for street engines and about 9,000 for the all-out race OHV NASCAR engines. F1 would be over 20,000 if the rules allowed it. This means that about the only ways to increase power meaningfully is to go bigger displacement, improve volumetric efficiency, or go forced induction. Or any combination of the three.

DoctorV8

Yeah, the long runner TPI intakes looked exotic and made great low end torque, but that's where the show ended. I'll never forget my first drive in a 1990 ZR-1, with its 11 throttle plates and 16 injectors. It was a true revelation to a kid who had been raised on 80s pushrod V8s. Life changing.

It still amazes me that the 9 year old LS7 revs so freely for a regular production OHV motor....the head flow #s actually blow away a number of DOHC setups, including the old LT5 and many Ford modulars. Sure would be nice to see another all out n/a motor with DI and a 12.5:1 or higher CR...call it the LT7 and watch people line up with checkbooks in hand.

H82BFST

Yep, it would likely make 550hp, but my guess is that Chevy knew even this amount of HP wouldn't overcome the weight increase and beat the C6-Z so they said hell with it, since we need 620hp to get there, we'll have to use a blower instead.

I hope I'm wrong and will be pleasantly surprised and the C7-Z weights less than the C6-Z and comes with this HP. Somehow, I'm not holding my breathe.

DoctorV8

Yeah, I'd just be happy if it's no heavier than a C6 ZR1. C6 Z06 weights are a pipe dream. The LT1 weighs more than an LS7, and with the blower/intercooler, etc, the LT4 will probably out weigh the LS9. The base car already has an AL frame and a fair bit of CF, so the low hanging fruit we plucked in 2006 are no longer there. Don't know where they can shave much weight, aside from maybe a CF torque tube and lighter flywheel, if they ditch the active fuel management. Hopefully CC brakes and maybe magnesium or CF wheels may help a bit, but again, my guess is 3400+.

JerriVette

The z06 news embargo lifts at 12.01 tonight and it smokes a Zr1

stevebz06

The C7 seats alone weigh 80 pounds apiece, almost twice as much as the previous seats. Most of the weight increase comes from luxury and entertainment oriented equipment that have nothing to do with the operation of the car and could be eliminated and it would be like adding 50 hp or more to the car.

Suaveat69

The C7 seats weigh 62 lbs. and the C6 seats weigh 55 lbs. according to GM.

boost2na

The most recent Cobalt SS, Solstice, and HHR with the 4 banger turbo are perfect examples. GM released a factory turbo upgrade: 280 hp, 320 ft-lbs (crank). Dyno (lines still intersect at 5250):

RJ-92

A lot of the newer DI motors, particularly pnes w FI seem to have a lower TQ peak. I wonder what affect DI has on VE compared to pprt ingection if any...

oicw

Hell, look at turbo diesels - most of them have HP less than half their torque. Heavy truck diesels have a 1:4 hp to torque ratio.

Nothing magical about the hp vs torque ratios; simply depends on how high you want an engine to rev.

GrantG

Direct Injection's main purpose is to raise Volumentric Efficiency (allows higher compression ratio without detonation). Normally aspirated motors of equal displacement should have a higher torque peak with DI.

The new turbo motors with DI that make more torque than hp is due to the turbocharger being kept small for better throttle response (less lag) and less stress on the engine internals, but this means they run out of steam a little near redline. The little turbochargers can't hold max boost much past torque peak rpm - gives them strong midrange performance which is where many people drive them (but I find them frustrating at the track, where you drive in the high rpms most of the time).