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

[Vette73]

They say torque moves cars, horsepower sells them..

With both motors being the same displacement (350),why do I see such a huge
difference in torque figures between modified motors?

Most C-5 Z06s which are modified put down pretty impressive torque numbers--430-440,sometimes over 500 Ft.lbs supercharged..

Most ZR-1s modded put down a lot less....Is it the double overhead cam as opposed to the single cam LS-6...? Shouldn't both be similar since the displacement is the same?

[Billy Mild]

It is mostly the DOHC vs. OHV motor design. Our motors were designed for HIGH RPM power. This usually translates to lower torque numbers.

[WARP TEN]

My 2016 Z06 is 650 HP/650 TQ. Revs to around 6800-7000. Pushrods and a supercharger. My 95 LT5 was about 500 HP and 430 TQ. I loved the ZR-1 and with its Haibeck 510 package it was very powerful, but the Z06 is most impressive.--Bob

[Paul Workman]

They say torque moves cars, horsepower sells them..

With both motors being the same displacement (350),why do I see such a huge
difference in torque figures between modified motors?

Most C-5 Z06s which are modified put down pretty impressive torque numbers--430-440,sometimes over 500 Ft.lbs supercharged..

Most ZR-1s modded put down a lot less....Is it the double overhead cam as opposed to the single cam LS-6...? Shouldn't both be similar since the displacement is the same?

Apples n oranges: Comparing any two cars needs to be (in this case) measured the same way, i.e., at the crank or at the wheels. Be careful when comparing results the data was collected the same way. For example, 377 pound-feet at the wheels on an inertia dyno ≈ 433 pound-feet at the crank; most factory #s are at the crank. (Comparing my "modded" LT5 wheel to crank PEAK torque.) N/A vs. FI...How is that relevant to any meaningful comparison?

Peak vs. average: Peak (horsepower especially) sells cars, average torque at the wheels is what wins races. Case in point: The L98 develops more peak torque that either the LT1 or the LT4. But, average torque of these motors trumps the peak torque of the L98s in a 1/4 mile contest. Don't get too enamored with "PEAK" numbers...

Define "modified". Without some baseline for "modified", how can a comparison be made, except on a random sampling? For what it is worth, the LS6 is by any definition a factory "hot-rodded" LS1. So, Pete Polatsidis' modified, NA stock bottom (350) LT5 qualifies as "modified" (by your criteria) and develops ≈ 488 pounds-feet torque and over 550 hp at the crank. That car has clicked off the quarter in 11.06 seconds at 129+ mph and is a street driven car.

Speaking of street driven! Engineering-wise, the 4-valve, DOHC architecture has some definite advantages over single cam, 2-valve OHV architecture in just about any application. But, add $$ to the equation, and then add rarity of a particular motor (LT5 in particular), and HP/$ is undeniably in favor of the pushrod solution.

As our former semi-professional drag racer, Bob Gillig puts it (speaking of single cam 2-OHV motors of equal displacement vs. the "LT5"); "Just about the time things get interesting, you have to shift. But, the LT5 continues to make power way past that point. That's why the LT5 will often win, even if the other guy has a PEAK 25 hp advantage".

And, the bench racing goes on...and on...:cheers:

[Vette73]

I've often pondered the thought of selling my ZR-1 for a C-5 Z06....What stops me basically is the condition of my Z.....It's been very well taken care of and looks great from that standpoint......Do like the rarity of the ZR-1 compared to the Z0-6..

My car has the basic mods and if I decide to keep it ( which I probably will) would like to port the heads to match the plenum and I/Hs....Heard many good things of people who have the 510 package on there cars..

[XfireZ51]

I don't think the LS-6 torque peaked at 5300rpm.

[Hog]

2001 LS6 ZO6 Corvette
385hp@6000rpm/385lb/ft torque@4800rpm

2002-2004 LS6 ZO6 Corvette
405hp@ 6000 rpm Torque: 400 lb-ft @ 4800 rpm

GEN 1 LT5 ZR-1 90-92
375hp@ 6000 rpm and 370 lbs/ft torque at 4800 rpm

GEN 2 LT5 ZR-1 93-95
405hp@5800rpm/385lb/ft torque@4800rpm

1992-1996 Corvette
LT1 300hp@5000rpm/330lb/ft torque@4000rpm

1996 LT4 Corvette
330hp@5800rpm/340lb/ft torque@4500rpm

[XfireZ51]

As Paul Workman says, it's the area under the curve. My dyno sheets, even pre-camshafts had torque peaks at 5300rpm. Most other ones I have seen are similar peaks.

[George Maz]

GEN 1 LT5 ZR-1 90-92
375hp@ 6000 rpm and 370 lbs/ft torque at 4800 rpm
GEN 2 LT5 ZR-1 93-95
405hp@5800rpm/385lb/ft torque@4800rpm

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?

[edram454]

george, those numbers are at the crank. your numbers are at the wheels. 434 horse at the wheels is lots of power.. over 500 at the crank. i guarantee those other cars wont make anything close to the advertised numbers at the wheels. Maybe a stock 1990 makes 330 hp at the wheels or a stock c5 z06 makes around the same but advertised 405 by GM.

ed ramos #3028

[Hog]

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...

http://i185.photobucket.com/albums/x220/6PPC_bucket/Dyno%20graphs/LT590-92amp93-95vsLS1vsLS6dyno-1.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/Dyno%20graphs/LT590-92amp93-95vsLS1vsLS6dyno-1.jpg.html)

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!

http://i185.photobucket.com/albums/x220/6PPC_bucket/Dyno%20graphs/Dynographs_zps723fdad7.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/Dyno%20graphs/Dynographs_zps723fdad7.jpg.html)

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.

http://i185.photobucket.com/albums/x220/6PPC_bucket/Dyno%20graphs/AzzuroFinalDynowithstockheadsandcams.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/Dyno%20graphs/AzzuroFinalDynowithstockheadsandcams.jpg.html)

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! :dancing

[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 ...

http://i1207.photobucket.com/albums/bb463/Emm3Speed/B6%20Passat%20Wagon%20Makeover/E790BF05-B1AF-47D0-A90D-EDE66F16E51A_zpsviqe2crs.png (http://s1207.photobucket.com/user/Emm3Speed/media/B6%20Passat%20Wagon%20Makeover/E790BF05-B1AF-47D0-A90D-EDE66F16E51A_zpsviqe2crs.png.html)

[Hog]

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

Magnaflow quad cat
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/Headers/catalyticmagnaflow2001vette_zpsve54zggi.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/Headers/catalyticmagnaflow2001vette_zpsve54zggi.jpg.html)

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.

[Hog]

01 LS6 vs 02-04 LS6

http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/Engine/Dyno%20Graph/powertorqueoutput2001vs200204LS6_zpsvjwd0lzh.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/Engine/Dyno%20Graph/powertorqueoutput2001vs200204LS6_zpsvjwd0lzh.jpg.h tml)