Torque differences between the LS-6 and the LT-5

[Hog]

Originally Posted by George Maz

I'm confused, my dyno sheet shows 365 max torque for a modified '90 ported heads, intake, headers, exhaust, cams, tune, etc. ...so I'm making less torque than stock?...how can that be with 434rwhp?

The numbers I posted are from stock engine ratings from the manufacturer in SAE net at the crank, not the wheels. OEMs use ratings measured at the crankshaft.

I will note that the rev limiter for the GEN 3 LS6 is set at 6600rpm, and the LT5s kicks in at 7200rpm

[Vette73]

Yes, figures on the dyno are at the wheel.....So 365 x.15 is around 410 at the wheels....Respectable numbers....

Curious to see how a supercharged C-5 Z06 feels like.....Anybody ever drive one with a supercharger? If so, is it power throughout the rev range? Or top end power.....You see a lot advertised with over 500 horse and torque in a relatively light weight car...

[wprice]

Yes I drive a SC c5 Z06, it doesn't get interesting until above 4k RPMs. I agree Apples and Oranges but still love the feel and sound of my ZR-1 it never gets old!

Wayne

[Vette73]

When you say apples to oranges, what exactly does that mean? I figured with a boosted car the RPMs have to be somewhat up there to start really feeling the power..

Agree the whole cockpit feel is different when you compare the two...That's as far as I have gotten in a Z06-sitting in one..

[BigJohn]

Hi Wyane, I have a supercharged LS7 and the power comes on from the get go.
The turbocharged cars need to spool up with RPMs; turbo lag.

[Hog]

It all depends on what type of forced induction you use and what exactly the system is designed to do. You can make a turbo boost hard at low rpm, or a supercharger only pull boost at higher rpm. There are centrifugal, Roots and Screw superchargers, the centrifugals tend on average to require more rpm to make the same boost that a comparable roots/screw type would make off idle or at low rpm, again it all depends on how the system is set up.

[Paul Workman]

I came across this dyno graph comparison...



A couple of note worthy comments:

The graphs cut off at ~ 6400 RPM, whereas the LT5 makes usable power to 7000+ rpm - way past the 6600 rpm cut-off of the LS6.

The difference between an LS1 and an LS6 is by any other name (description), a factory "hot rodded" LS1 (similar to the LT1/LT4 scenario...) In the case of the LS6, there were bigger heads, bigger intake manifold, higher compression (10.5 vs. 10.1 for the LS1) and a bigger cam, among other tweaks boosting the LS1 to the LS6 specs.

Apples to Oranges? Yes.

(Referring to the graph above) Think of the stock LT5 torque curve (below) as being pretty close to that of the LS6, except for the last 600 rpm! The comparison of relatively the same mods to the LT5 compared to the LS6 with approximately the same general modifications (and equal streetability) is pretty striking...and explains a LOT at the track!



And, even if limited to DIY porting, Dominic's top-end porting w/o head work or cams made 392 to the wheels certainly speaks to the performance left on the table by GM, far as the LT5 goes.

Showing ~ 392 at the wheels is ~ 461+ hp at the crank...for comparison.



The graphs tell the story. It's easy to get swayed by "PEAK" numbers - as every salesman knows! It's power under the curve, and torque to the wheels x speed is that what is really important. That LT5 is a BEAST just itching to be let out!

[Hog]

For everyones info, the above LT5 vs LS6 vs LS1 compares the 1990-92 GEN 1 LT5 and the 2001 LS6 and the 2000 LS1 only. Note that in 2001 all GEN 3 SBCs used in the Vette and F bodies got the newer 2001 LS6 intake manifold. That was used for one of Hibs articles and was supplied by GM.

And a personal quote from Hib "The LS6 eclipsed the LT5 in just about every category except three: rev limit, number of camshafts and visual appeal."

The LT5 also has a small displacement advantage with its 3.90" bore and 3.66" stroke for 350 cubes
LS1/6 is 3.90" bore and 3.622 stroke for 346 cubes

2001 LS6 rated at 385hp@ 6000rpm/385lb/ft torque @ 4800rpm
http://www.netmotive.net/articles/hib/ls6/INDEX.HTM

2002-2004 LS6 rated at 405hp @ 6000rpm/400lb/ft torque @ 4800rpm
http://www.netmotive.net/articles/hib/02ls6/index.htm

375 SAE net hp @ 6000 rpm and 370 lbs/ft torque @ 4800 rpm.
405 SAE net hp @ 5800rpm/385lb/ft torque @ 4800rpm
Too be fair, there is "useable" power above the 6000rpm power peak and the 6600rpm redline of the LS6 as well, GM simply had to shut it down in order to meet the durability of hundreds of thousands of miles. That illustrates the valve liiting action of using 2 larger valves over 4 smaller ones. The GEN 1 LT5 had a power peak of 6000rpm, as did the 2001 LS6. The LT5 allowed for another 1200rpm above the power peak, while the 2001 LS6 only allowed 600 rpm. The valves would float in the 6800-7000tpm area. It should be noted that the later GEN 4 SBC LS7 had a rev limit of 7100rpm while originally making 500hp@6300rpm and 435 lb/ft torque @ 4800rpm after the SAE got a hold of it and used its brand new spec of engine output measurement the LS7 was the 1st engine to use the new SAE CERTIFIED POWER using J1349/J1995 the LS7 made 505hp/470 lb/ft of SAE CERTIFIED horsepower.

I like this part of the article "Further testing during the winter of ’98/’99 proved oil was being trapped in the valve covers then sucked into the engine through the PCV system. The solution, which took the first half of ’99 to perfect, was new PCV hardware. Taking a page out of the decade-old, LT5 book, LS6 uses a valley-mounted oil separator assembly rather than the rocker-cover units of the LS1. This significantly reduces oil aeration and oil consumption and simplifies the system"

"At a ripe old age of 11, the ZR1’s only remaining title is "Fastest Production Corvette" at 180 miles per hour."
The LT5 is a wonder of 1980 technology, its ECM was a major evolution for part throttle and WOT fueling. There were great solutions for attempting to deliver high rpm power AND lower rpm torque AND some semblance of fuel economy. The ECM selecting either 8 or 16 injectors coupled with the mechanical closing off and opening of the Port Throttles accomplished this to great effect.

The 3rd GEN for OBD2 usage in 1996 would have been amazing. I'm glad the that Mr Behan and LPE got one all together for testing. I so wish that Chevrolet went with the GEN 3 LT5 and the redesigned C5 Corvette and the Lotus designed "powerbulged" hood. Sure it was a bit heavier, but damn it would fly. But alas GM wanted the GEN 3 SBC to power all of its GMT-800 pickup trucks, Camaros/Firebirds and Corvettes and even FWD Impalas.
GM chose lifters over cam followers.

[5ABI VT]

Imo there's one very good reason why the ls6 matches the LT5 in power and beats in in torque ...

[Hog]

The 2001 ZO6/LS6 is saddled with 4 cats, 1 pup-cat and 1 regular catalytic per engine bank.

Magnaflow quad cat


I'm pretty sure the pup cats were eliminated for the second 405hp version of the GEN 3 LS6.

And yes, SABI-VT, those are great manifolds.