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The new LT4, while being supercharged like the ZR1's LS9, is "crushing the LS9's benchmarks." And, catch this, 29 MPG highway!!!


Wards Auto said:
LT4 Puts ‘Brutal’ Power Behind Corvette Z06: Supercharger Key Component!

Jordan Lee, Chief Engineer for the small-block V-8 at GM, says the LT4 crushes the performance benchmark set by the LS9. “The LT4 makes the ZR1 feel sluggish,” he says.

With several months of engineering work remaining on the ’15 Chevrolet Corvette Z06, the sports car already owns the fastest lap at the General Motors Proving Ground. In the coming weeks, more records are expected to fall when it travels to Germany’s fabled Nurburgring for testing.

The supercharged, 638-hp Corvette ZR1 owns GM’s quickest turn of “The ’Ring,” posting a 7:19.63 in 2012. That’s about 3.5 seconds ahead of the previous-generation Z06, which still commands a top-15 time at the track from 2011.

But the redesigned ’15 Z06 boasts an all-new 650-hp 6.2L LT4 V-8, which like the ZR1 with its 6.2L LS9 V-8 uses an Eaton Roots-type blower for added power over base-model Corvettes.

Jordan Lee, chief engineer and program manager for the small-block V-8 at GM, says the LT4 crushes the performance benchmark set by the LS9.

“The LT4 makes the ZR1 feel sluggish,” Lee says during a recent backgrounder on the engine here. “It’s brutal in a raw sense, but a thrill.”

The LT4’s calling card is maximum power almost instantly. The engine, based on the fifth-generation small-block LT1 6.2L V-8 architecture powering the ’14 Corvette Stingray, makes 457 lb.-ft. (619 Nm) of torque just off idle, Lee says, and 625 lb.-ft. (847 Nm) at a scant 2,800 rpm.

The LT4 also maintains 90% of its peak torque, or 592 lb.-ft. (802 Nm), from 2,500 to 5,400 rpm. The full brunt of the LT4’s 650 lb.-ft. (881 Nm) of thrust comes at 3,600 rpm and gives it nearly 8% greater peak grunt than the ZR1.

GM has not published a top speed for the Z06, but given the power output it would almost certainly exceed the 205 mph (330 km/h) of the ZR1. GM has said the ’15 Z06 with its new 8-speed automatic will do 0-60 mph (97 km/h) in 3.7 seconds and cover the quarter-mile (0.4 km) in 11.9 seconds, clear evidence this engine indeed is loaded with low-end torque.

The rubber-shredding numbers of the LT4 are made possible largely on the strength of updates to the LS9’s supercharger.

The new R1740 TVS 1.7L supercharger atop the LT4 spins at up to 20,150 rpm, according to GM. That’s 5,000 rpm more than the 2.3L LS9 blower. Like its predecessor, the LT4 supercharger contains a pair of 4-lobe rotors, but they are shorter in length and smaller in diameter, which makes them capable of higher rpm to deliver more boost earlier.

The new supercharger is more efficient, too, thanks to a more direct discharge port that creates less turbulence, which reduces heat and speeds airflow into the engine, GM says. The supercharger’s charge-cooling system also gains more efficiency, offering 10% greater heat rejection through 23% reduced volume compared with the LS9, the automaker says.

GM shrunk the overall size of the supercharger and intercooler assembly to retain a low hood profile and still meet pedestrian-protection regulations globally.

It lost 20 lbs. (9 kg) off the LS9’s supercharger, while adding a negligible 1 in. (25.4 mm) to the height of the LT4 compared with the naturally aspirated LT1 found in the Corvette Stingray.

The supercharged LT4 uses many of the same components making up the LT1, although a few technical changes were made to accommodate forced induction.

The LT4 direct-injection fuel system, which was a first for the small-block on the LT1, receives a higher-flow fuel pump; higher-flow fuel injectors with a unique spray to optimize combustion under boost; and a higher-capacity rail to handle the capacities of the new pump and injectors.

Rotocast A356-T6 aluminum cylinder heads are added to the LT4 because they are stronger and handle heat better than conventionally cast aluminum heads.

Combustion chambers are bigger on the LT4 than the LT1, and lightweight, solid titanium intake valves replace hollow units for greater strength and resistance to heat.

The LT4 also swaps in lighter, stainless steel exhaust manifolds compared with the iron manifolds of the LT1.

Rotating assembly parts are unique to the LT4 to support higher cylinder pressures of the boosted engine, as well its lower compression ratio of 10:0.1 versus 11:5.1 on the LT1.

The oiling system of the LT4 remains essentially the same as the LT1, but it receives a larger oil tank and a larger oil cooler as well as unique Dexos 5W30 lubricant.

And while GM builds the LT1 in Tonawanda, NY, the LT4 gets assembled at the automaker’s Performance Build Center, which recently moved to the Corvette’s Bowling Green, KY, assembly plant from a skunk-works facility in Wixom, MI.

Despite all the power, the LT4 achieves an EPA-estimated 29 mpg (8.1 L/100 km) on the highway. Much of that is owed to cylinder deactivation and variable-valve timing technologies.

LT4 Puts ?Brutal? Power Behind Corvette Z06 | Vehicles & Technology content from WardsAuto
 

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Great article John, and thank you. It's kind of humorous in that I witnessed all kinds of arguments, just a couple of months ago when members of "Other" forums were arguing over how this new LT4 engine is inferior to the fabled LS9 found in the ZR1, which was argued was/is by far superior because of the larger 2.3L supercharger.... Kinda goes to show bigger ain't necessarily better.. The entire time I thought smaller superchargers aren't a bad thing because of the fact of spinning them a little faster causes them to come in quicker than the larger blowers. Based on this article, I was VERY happy to see GM finally got rid of those crappy hollow stem titanium valves for much stronger and more reliable solid stem titanium units. I understood what GM was thinking with the valves with the knowledge of what Ford went through back in the 60's with their hollow stem sodium filled valves and all the failures they experienced. GM has made quite a few internal modifications to the 6.2L LS1 engine for the added boost of the LT4, which is a necessity for supercharging an engine. While many may add superchargers or turbochargers to the LT1 out there, which they will continue to argue the fact and blow them up because the engines aren't actually equipped to handle the extra boost, GM has done it right with the LT4. And just think....... it gets 29MPG and has a five year/one hundred thousand mile warranty on top of it all. Life is GOOD.....
 

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0-60 in 3.7 and 1/4 mile in 11.9 wtf I hope that's not right
Not to worry Madmav, as usual, those numbers are conservative and subject to change through the efforts of Corvette's loyal customers..... Stay tuned in the coming months for those numbers to be obliterated. While I might seem a bit optimistic, I'm also aware of the potential of what 650 HP and 650 TQ is capable of in a 3500 lb car. Particularly considering the horsepower and torque curves of this new engine. It'll just be a matter of hooking the car up and putting it to the ground.
 

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Discussion Starter · #5 ·
0-60 in 3.7 and 1/4 mile in 11.9 wtf I hope that's not right
That is not right, as Chief Engineer Tadge Juechter already stated, later repeated, that "the Z06 will do 0 to 60 in UNDER 3.4 seconds."[/]. Tadge is the master of understatement until the final testing is done. I am expecting 3.15 seconds for the 8-speed, 3.25 seconds for the 7-speed manual trans.

Most are betting no more than 10.9 seconds, maybe better for the quarter.
 

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Odds are it will also be the 2016 CTS-V engine. The AFM should allow avoidance of the Gas Guzzler tax (@ $3.000) that applies to the current CTS-V.
 

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3.7 is what folks are saying the Stingray with the 8 speed will do and I seem to recall Tadge saying they had a number of test cars running 3.5 to 3.6 as well and 3.7 is the comfortable number. I'll look around some more for the article. So hopefully the Z is very low threes - hooking up the tires will be huge.
 

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One more amazing engine from the folks at GM.

I'll be following the Z06 threads to understand if the engine is living up to its promise - I very much hope it does.
 
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John, I wonder how that LT4 supercharged would do in my 1970 Camaro, of course straight line only! My ole HotRod doesn't like road courses.

SF
Rick
 
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John, I wonder how that LT4 supercharged would do in my 1970 Camaro, of course straight line only! My ole HotRod doesn't like road courses.
Funny you mention that, because I was wondering if GM might offer an LT4 crate engine that I could drop into my '68. :)
 
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John, I wonder how that LT4 supercharged would do in my 1970 Camaro, of course straight line only! My ole HotRod doesn't like road courses.

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Rick
I saw a '68 Camaro at a car show that had a ZR1 LS9 in it. It was gorgeous. Unfortunately, the owner was not there when I went by, to talk to.
 
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