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LT2, LT6, And LT7

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  • LT2, LT6, And LT7

    AUTOMOTIVE & AFTERMARKET NEWS

    What the New LT2 Mid-Engine Corvette Reveals About the Future of GM LT Engines

    https://www.onallcylinders.com/2019/...gm-lt-engines/

    Posted by Brian Nutter on April 15, 2019 at 5:00 pm
    This is reportedly a leaked CAD file image of the future LT7 5.5L DOHC engine that would hypothetically power the ZR1 version of the new mid-engined C8 Corvette. (Image/Corvette Forum)
    Editor’s Note: With the excitement surrounding the General Motors’ confirmation of the new mid-engined C8 Corvette, we asked our friends at Summit Racing to share their thoughts about what the future holds for the small block Chevy engine as it continues to evolve through its fifth generation with the new LT2 slated to power the 2020 Corvette.

    What can we expect from that engine, and from even more capable versions to be found in the Z06 and ZR1 (and/or Zora)?

    Brian Nutter, Summit’s resident expert on LS and LT engines, weighs in below.

    Engineers at General Motors Global Propulsion Systems have a history of paying reverence to their own past by rebooting engine designations. For instance, the LT1 was available in 1970-72, then again in 1992-97, and then again in 2013 as the first Gen. V small block Chevy engine.

    GM engineers also have a sense of humor, and sometimes offer little hints about their future plans. An example is GM making the pecking order of engine codes the same in the C4 and C7 Corvettes: LT1s in the base models, LT4s in the mid-range, and the LT5 serving as the top dog.

    So what hints could the new engine code LT2 give us? Reportedly leaked images of the new LT2 engine at the heart of the new 2020 C8 Corvette. (Image/Motor1.com)
    That answer might come from the introduction of the C6 Corvette in 2005.

    The engine switched from LS1 to LS2. The LS2 was an evolution of the LS6, and ushered in the Gen. IV LS engines.

    The LS2 and LS6 had things in common like the 24X reluctor crank, 3-bolt cam, and 243 casting cathedral port heads.

    The biggest difference between the two engines was the displacement, which increased from 5.7 to 6.0L. How Might GM Engineers Increase the LT2’s Displacement to Make More Power in Future Engines?


    This isn’t likely, but we guarantee it was considered. From a hot-rodder’s perspective, how about increasing the LT2’s displacement to 6.6L? Just borrow the forged steel 3.858 in. stroker crank from the new 6.6L L8T powering the 2020 Chevy Silverado and GMC Sierra to make it happen.
    What can the new LT8 Chevy/GMC truck engine, and what little we know about the new LT2 slated to power the 2020 mid-engineed C8 Chevy Corvette tell us about the future of small-block GM performance engines? (Image/GM Authority)Would fuel mileage suffer?


    Not if GM utilizes the latest-generation Dynamic Fuel Management cylinder deactivation technology. \

    DFM takes control over all 16 lifters instead of just eight as are used with AFM. (Image/GM-Techlink.com)
    An improvement over AFM, DFM has 17 different cylinder firing patterns and switches seamlessly between them to provide just the right amount of power.

    We will probably see improvements to the cylinder heads as well. There is room for improvement as shown by the new Edelbrock Gen.5 heads. What other technologies could be applied?

    People may not realize the name GM Powertrain was changed to GM Global Propulsion Systems in 2016.

    Part of the reason for the name change stems from the ongoing integration of electrified hybrids.

    Corvettes have always had good fuel efficiency and don’t get saddled with the gas-guzzler tax. To add more power and performance to future Corvettes, we could see GM engineers implement their eAssist system called BAS 3 (Belted Alternator Starter). BAS3 is a newer version of this BAS2 system used in the 2012 Buick Lacrosse. It was a mild hybrid that used a 115V lithium ion battery and 15kW motor. (Image/Media.GM.com)
    It bolts simply to the accessory drive in place of the alternator. It’s a proven technology currently used in the 2016 Silverado and improves mileage 13 percent. Although it adds another 100 pounds, it provides 13 more horsepower and 44 foot-pounds of torque.

    With an automatic, it serves as the starter motor for low-speed start/stop and take-off. (Image/Porsche)Another benefit to going mid-engine?


    With the front of the car freed up, an electric motor could drive the front wheels when added forward grip is required (like Porsche did in the 918). Incorporating a variant of the 200-hp Chevy Bolt electric motor up front would give the ultimate Corvette a cool 1,000 hp when mated with a twin-turbo LT9.

    Not only does it add grip in a straight line, it would use an e-diff to meter power independently to each of the front tires to help them pull the car through a corner. What about the 5.5L DOHC engine variants that’s been rumored to power the Z06 and ZR1/Zora?


    These variants will become the Gen. 6 small block.

    GM has already shown a willingness to supercharge both the Z06 and ZR1, although they did receive different sized superchargers. Mostly likely, the DOHC 5.5L used in the Z06 will get turbos.

    Before getting into the tech of a turbocharged DOHC, let’s dream a little dream here for a high-revving naturally aspirated motor for the Z06. These would likely get the LT6 or LT7 designation. How would GM do it if they decided to go that direction?

    First, it would have to have a clear advantage over the LT2.

    We think it would take another 100 hp. Is 600 hp possible naturally aspirated? Well, the 5.2L Shelby GT350 makes 526 hp and 429 ft.-lbs, the 4.5L found in the Ferrari 458 makes a reputed 562 hp.

    The closest would be the 4.6L found in the Porsche 918. It makes 600 hp at 8500 rpm. In theory, the Z06’s larger 5.5L could make 600 hp at 8000 rpm and do it more reliably.

    How would it do this? Taking a cue from the aftermarket, they may run tubular headers and a twin-throttle body intake similar to the Edelbrock Cross-Ram LS3 intake.

    What are some other considerations? The Corvette program has always valued packaging efficiency in their engines.

    DOHC engines are wider than a pushrod engine, so deck height needs to be shorter for packaging. That said, GM always likes a little wiggle room for added displacement down the line.

    Purely speculation, but what are several ways 5.5L could be achieved?
    Show 102550100 entries
    Search:
    Original LT5 3.898 3.661 5.740 1.440 9.026 349 c.i.d./5.7L
    Destroked LT5 3.898 3.504 5.740 1.181 8.673 335 c.i.d./5.5L
    Current 4V trends 3.838 3.622 5.787 1.181 8.780 335 c.i.d./5.5L
    Showing 1 to 3 of 3 entries
    PreviousNext


    Based on current 4-valve trends, a deck height of 8.780 would narrow the engine block. With smaller bore spacing (4.252?) than the pushrod LT1, the length of the engine would be shorter too. Although the cam covers will be significantly wider than the pushrod engine, every bit helps. What kind of tech would be found in the boosted LT8/LT9 version?


    First, by going mid-engine, Chevrolet gave themselves more room for a pair of turbos. This wasn’t easily done in the front-engine C7, so the 2650 Eaton supercharger was a logical choice. We could also take cues on its technology from Cadillac’s new Blackwing engine.

    That 4.2L twin turbo V8 makes about 550 horsepower and 627 ft.-lbs.

    It’s possible the Z06 would get smaller turbos than the ZR1, but maybe not. What would set the ZR1 apart in terms of grip and acceleration would be the before mentioned electrification of the front wheels. This would also play into the weight savings and track focus a Z06 has traditionally versus a ZR1.

    Note in the top image of this article that the turbos are feeding the intake manifold directly. This points to the use of air/water intercooler bricks inside each of the dual plenums similar to what is used in the LT4 and LT5 today.

    The Chevy engineers will want to make more than the current LT5 engine, so you could expect it to make something around 775-800 hp. (Image/Detroit News)
    Whatever happens, the C8 will go toe-to-toe with the world’s most exotic supercars and do so at a fraction of the price. The tech found in the Gen. 6 engine will be transferred to other cars, and even trucks. To the fine folks at GM Propulsion, have fun with this one and keep up the good work!

    Tags: 2020 Corvette, C8, Corvette, mid-engine Corvette
    Author: Brian NutterAfter a stint in the U.S. Air Force, Brian Nutter studied at the Houston, TX-based School of Automotive Machinists in 1997. The early part of his automotive career included working for engine builders Scott Shafiroff and C.J. Batten, followed by several years developing performance pistons at Wiseco Piston Co. Today, Brian develops performance parts for Summit Racing Equipment and is a regular OnAllCylinders contributor. For fun, he runs his 427-powered C5 Z06 in ECTA land-speed racing, at OPTIMA® street car events, and at a mix of autocross, drag racing, and track days.Designed by WPZOOMCopyright © 2019 — OnAllCylinders. All Rights Reserved.



















    Last edited by John; 05-13-2019, 07:58 PM. Reason: Outstanding find SheepDog; tiny edits for easier viewing. Thank you very much.

  • #2
    VERY INTERESTING.......thanks for posting.
    The least we can do is wave to each other

    Comment


    • #3
      Outstanding thread post SheepDog. Got to cut the last of my fields right now (days of raining forecasted), so I will double back and re-read it much more slowly. Thank you so much for adding really good content!
      Excited owners of a 2015 Z06. Lifetime, annual contributors, and 20 year members of NCM. Our 2020 ME C8 Corvette is next.

      Comment


      • #4
        great info!!! Thanks so much SheepDog👍

        Comment


        • #5
          Understanding Engine Measurements

          Piston Math

          Jake Amatisto Oct 29, 2013
          Share
          Full Gallery

          As gearheads, we love to remember numbers. Many can probably rattle off all sorts of specs from various cars and engines. Cubic inches, rearend ratios, and camshaft lift specs are a lot of the common numbers that come up in car guy conversations everywhere. Although most, us included, get lazy and round up or down (for example, our "383" small-block actually displaces 384.5686 ci), for the most part, the hot rodding crowd is obsessed with numbers. But when we ordered a set of custom pistons recently we realized there are a lot of dimensions of the small- and big-block Chevy that we weren't that familiar with, at least not as exact as we should be. Deck heights, piston dome volume, head gasket volume figures, and the following are not all that solid in our memories, even the term used. Knowing the details of your engine is useful to have, even if you're not building it; and as Chevy fans, we have really only three engine types to keep track of, the LS and the small- and big-block families. Becoming familiar with important numbers in our hobby is something we feel helps it thrive. After all, knowledge is power.

          Deck Height
          The deck height of a block is the measurement from the center of the crank to the top of the cylinder head mounting surface. Common deck heights for small-block Chevys are 9.025-inch for the 302, 305, 327, and 350ci engines, however the aftermarket also offers a tall deck small-block Chevy block that measures 9.325 inches, which is a dimension that comes from the rare GM Rocket block design. The late-model small-blocks, such as the LS and LQ engines, have a 9.240-inch deck height, while big-block Chevy engines measure 9.800 inches pretty much across the board (except for some tall deck truck engines, such as the 427); however, tall 10.2-inch deck big-blocks are also available in the aftermarket and are used for larger cubic-inches engines, such as the massive 632 and larger engines used in drag racing. This measurement of the block will ultimately determine what rod length, stroke, and piston design you'll need for a target compression ratio.


          Compression Ratio and Compression Height
          The compression ratio is a more commonly remembered number in the gearhead community; it determines what fuel you can run and how much horsepower you can make. The ratio is a figure that comes from the volume of a cylinder with the crank at bottom dead center (BDC) compared to the cylinder at top dead center (TDC). Case in point, if you measured a small-block with a cylinder volume of 80 ci at BDC and a cylinder volume of 7.5 ci at TDC, you take those two numbers and divide them you get around 10.6:1 compression. The farther apart these numbers are, the more compression you will have. The higher the ratio, the more likely detonation will occur and, in turn, higher octane fuel is needed. We've seen that 10.5:1 seems to be the agreed amount for naturally aspirated engines on pump gas, however some brave souls choose to push it.

          The compression height is the distance from the piston pin to the top of the piston and this is figured out once the builder knows a couple factors; the deck height, rod length, and the stroke length (see chart). The compression height of your pistons isn't the most important number to remember, but if you familiarize yourself with a general idea of what's considered tall and short compression heights, it makes you more informed when you're researching parts for your next build. For example, our 10.5:1 compression, 385ci SBC has flat-top pistons with a compression height of 1.125 inch.
          /10

          How Compression Height is Calculated:
          Compression height = block height - rod length - (0.5 × stroke)



          Example:
          block height = 11.685 inches
          rod length = 7.500 inches
          stroke = 5.500 inches


          Compression height = block height - rod length - (0.5 × stroke)
          Compression height = 11.685 - 7.500 - (0.5 × 5.500)
          Compression height = 1.435 inches


          Piston Dome Volume
          There are three choices when it comes to piston types: domed, flat-top, and inverted dome. Generally, for pump fuel, the flat-top is an ideal choice, with the inverted dome being great for low-compression supercharged engines, and the domed piston being more for racing engines. We were recently stumped when we were asked how many cc's the dish was in the pistons we are running, and had to look up what we ordered from Mahle. This also inspired us to look up some other more common piston dome/dish cc's for our own knowledge. If you see a small-block piston with a -5cc dish, for example, it's likely a flat-top with two valve reliefs, whereas a -31cc is more of an inverted dome. Because of the arrangement of the valves, big-block pistons with a -3cc dish is a flat-top with a single valve relief.
          4/10
          5/10

          An example of two domed pistons shows the volume differences in the domes. The piston on the left is a 8cc dome while the piston on the right has a slightly less raised dome, at 4 cc. These two pieces typically determine if you’ll be running pump gas or race gas in your engine.

          Combustion Chamber and Head Gaskets
          The combustion chamber volumes of the three Chevy engines can vary quite a bit depending on manufacturer, or, if you're dealing with stock heads, the year they were cast. Skilled engine builders check this by using a CC Kit like the one pictured from Powerhouse (PN POW351150), which is a 100cc x 2cc graduated cylinder and stand that can accurately determine volumes. Some sizes we've seen from the aftermarket are advertised from 64cc chambers up to 80 cc for some race heads, so it's important to measure this. To do so, you flip the cylinder head so the chamber faces up, then, once you grease up the area around the chamber, place a piece of clear plastic sheeting with a small hole over the chamber, completely covering it. Then, with the graduated cylinder filled with colored liquid, you open the valve and record how much fluid it takes to fill the void in the chamber.

          Head gasket thicknesses can range anywhere from 0.012 to as thick as 0.080, but the common size for small-blocks is 0.040. This, too, must be factored into your piston math, so it's a good idea to measure this using the CC kit, keeping in mind that it will cinch down by 0.002.

          Understanding Airflow
          If you really want to get into the algebra that engine builders use to figure out all your engine's parameters, HP Books published an informative book called Engine Airflow by Harold Bettes that features every equation you could want. Whether you want to figure out your intake port's cross-sectional area, or you just want to have access to the basic equations, like figuring cubic inch and compression, this book can help you delve into all the numbers needed to assemble a high-performance engine correctly.6/10
          7/10

          Skilled engine builders use a graduated cylinder and stand to accurately measure the combustion chamber size of a cylinder head. Sources

          Mahle Motorsports
          Fletcher, NC
          888-255-1942
          http://www.mahlemotorsports.com

          Powerhouse Products
          Memphis, TN 38118
          800-872-7223
          http://www.powerhouseproducts.com

          L&R Engines
          Santa Fe Springs, CA 90670
          562-802-0443
          www.lnrengine.com/
          Lunati Camshafts
          Olive Branch, MS
          662-892-1500
          www.lunatipower.com

          Comment


          • #6
            I wonder in July, if GM will tell us what models are planned (Z06 and Zr1) and what engine will go into them.

            Comment


            • #7
              I was pleased to see those turbos off to the side of the engine, and not between the heads in a "hot vee" configuration.

              To me, "hot vee" is just too hot and leads to reliability issues.

              Comment


              • #8
                Sorry , but no. We will not learn one fact about what model nor one component that is not visible at the reveal (exception maybe a minor, minor option that will be offered on the model(s) they have at the reveal.. They have never told us a single thing about might be coming down the line. If there is no HT hardtop at the reveal (we do not know either way now), and if someone in the media were to ask, “what about an upcoming Spyder model,” these identical words will again be heard from Tadge or Harlan, “we do not discuss potential future product.”

                Again sorry, but that is the way it has been and will be with GM.
                Excited owners of a 2015 Z06. Lifetime, annual contributors, and 20 year members of NCM. Our 2020 ME C8 Corvette is next.

                Comment


                • #9
                  What do you think the redline will be with the new LT2 engine?

                  Comment


                  • #10
                    We saw a CarScoops picture of the interior, and while the main dash instrument was partially blocked, by extrapolating someone figured out that IMO, it is 7,000.
                    Excited owners of a 2015 Z06. Lifetime, annual contributors, and 20 year members of NCM. Our 2020 ME C8 Corvette is next.

                    Comment


                    • #11
                      Originally posted by John View Post
                      Sorry , but no. We will not learn one fact about what model nor one component that is not visible at the reveal (exception maybe a minor, minor option that will be offered on the model(s) they have at the reveal.. They have never told us a single thing about might be coming down the line. If there is no HT hardtop at the reveal (we do not know either way now), and if someone in the media were to ask, “what about an upcoming Spyder model,” these identical words will again be heard from Tadge or Harlan, “we do not discuss potential future product.”

                      Again sorry, but that is the way it has been and will be with GM.
                      They may do what they will, however if there is no HT Vert. at the reveal or no mention of when it may be coming down the pipeline - They will lose my interest, as we have seen proof of a HT Vert in some of the spy photos. I honestly believe they will at least let the USA Made Sportscar Enthusiast know what is planned as competition is fierce and there are many other options. Patience has run thin with most of us and I would rather purchase an American made product, however if they would leave us wondering what may become available without any definitive information- well it may not work out well in their favor. The American public needs to stick together. We will hang in there but if our patience is tested for too long anyone would stray and not really care as they may feel there is no loyalty between the company and their customers. Sorry for the rant but I for one will be over it. Just my Honest Opinion.
                      Last edited by Frenzy36; 05-14-2019, 02:42 AM.
                      Rocket City Florida

                      Comment


                      • #12
                        Originally posted by John View Post
                        We saw a CarScoops picture of the interior, and while the main dash instrument was partially blocked, by extrapolating someone figured out that IMO, it is 7,000.
                        I'm sure that a reliable 7,000 RPM is achievable, even with 6.2 - 6.5 L and push rods, and I really hope that redline turns out to be true.

                        I expect the Z06/ZR-1/ZORA to have flat plane crank engines, with redlines in excess of 8,000 RPM.

                        The new magneto rheological fluid engine mounts should keep engine vibration under control for these flat plane motors.
                        Current Vettes:
                        '68 Lemans Blue 327/350 Convertible
                        '91 Turquoise Convertible w/hardtop
                        '14 Lime Rock Green 2LT Convertible, Black Top, Kalahari, 7-Speed, Performance Exhaust - Ordered on 4-1-2014, 2000 Status on 4-10-2014, TPW 5-12-2014, Built on 5-16-2014, Picked-up at dealership on 5-30-2014
                        "Delta t = 23"

                        Comment


                        • #13
                          Originally posted by Frenzy36 View Post

                          They may do what they will, however if there is no HT Vert. at the reveal or no mention of when it may be coming down the pipeline - They will lose my interest, as we have seen proof of a HT Vert in some of the spy photos. I honestly believe they will at least let the USA Made Sportscar Enthusiast know what is planned as competition is fierce and there are many other options. Patience has run thin with most of us and I would rather purchase an American made product, however if they would leave us wondering what may become available without any definitive information- well it may not work out well in their favor. The American public needs to stick together. We will hang in there but if our patience is tested for too long anyone would stray and not really care as they may feel there is no loyalty between the company and their customers. Sorry for the rant but I for one will be over it. Just my Honest Opinion.
                          That's one perspective. I'm also waiting for the C8 hard-top Roadster, but I'm patient. Also have no interest in another brand for my next sports car, just the C8.

                          So, GM, take your time and get the C8 Roadster right, and I'll be at the dealership with my cash in hand when it's ready.

                          Meanwhile, I'll be tearing-up asphalt in my C7 through the remainder of 2019.
                          Current Vettes:
                          '68 Lemans Blue 327/350 Convertible
                          '91 Turquoise Convertible w/hardtop
                          '14 Lime Rock Green 2LT Convertible, Black Top, Kalahari, 7-Speed, Performance Exhaust - Ordered on 4-1-2014, 2000 Status on 4-10-2014, TPW 5-12-2014, Built on 5-16-2014, Picked-up at dealership on 5-30-2014
                          "Delta t = 23"

                          Comment


                          • #14
                            I used the word if the HT is not at the reveal, for even the birdies are not whispering. Additionally, if the coupe knocks socks off, and if specs are exciting, I doubt that after waiting such a long time for the ME to appear, that 98% would not chose to wait a couple of, or even three months longer. Hell, there will be those who are at small dealers (with lesser allocations), who might not be getting theirs for that long due to constraints alone. So, so many variables that we do not know.

                            All we I know is that in 65 more days, we will be delighted (I know that and some others do also). We “know” that because this is the same design team who delighted us with our C7’s, the same engineering and design teams who brought forth on 1.13.13 our current generation Corvette which won 21 major automotive awards in the first year after its reveal (the most of any vehicle before then or still to this day).

                            I have confidence in the Corvette team. The C8 will be a stunner! And if a handful peel off, and choose to buy a used McLaren or A8 or similar in the week after 7.18.19, my personal bet it that they 98% will double back and get their C8 Z06 around then.
                            Excited owners of a 2015 Z06. Lifetime, annual contributors, and 20 year members of NCM. Our 2020 ME C8 Corvette is next.

                            Comment


                            • #15
                              Originally posted by John View Post
                              We saw a CarScoops picture of the interior, and while the main dash instrument was partially blocked, by extrapolating someone figured out that IMO, it is 7,000.
                              The guage reads to 7000, but typically the last 500rpm are in red, above redline. So probably a 6500rpm redline, same as the LT1, which is expected for a pushrod valvetrain.

                              Click image for larger version  Name:	C8 Instrument Panel.jpeg Views:	16 Size:	478.7 KB ID:	36193

                              Edit: figured I'd better check out the C7's tach and it appears I was wrong, the LT1's tach goes to 7500rpm, for 1000rpm over redline. But remove the gear indicator on the lower right, and the tach's scale can spread out enough to put 3500 rpms at top dead center with a max of 7500 rpm, 1000rpm over redline.

                              Click image for larger version  Name:	101613_5.jpg Views:	0 Size:	101.3 KB ID:	36201
                              Last edited by electroVette; 05-14-2019, 10:14 AM.

                              Comment

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