Whoa I leave for 1 day, and the flames are rapidly spreading. I never claimed that this would be the number in the Vette, on the contrary, I doubt that this will be it. However, this is a fair estimate for a MINIMUM number based off the gains that the new 5.3 achieved. As the 5.3 is clearly biased toward torque and not HP (most likely opposite of the Corvette, or any modern sports car for that matter), I went with HP in my calculations. For those who asked for torque, here it is: 12.65% gain (from 340lb-ft to 383), which yields 477.6235 lb-ft of torque (when using 424 for the ls3). My math is correct; math is my field of study haha.

 

It takes more than "math" to design an engine. Doing the ''math", if the 6.2L NA engine in the Mercedes has 479 lb-ft of torque, then the 7L NA engine in my Z06 should have 541 lb-ft of torque. It doesn't as it has 470 lb-ft. Do you think there might be other aspects to designing an engine besides extrapolating numbers?

 

Joe, I was simply agreeing with you on the design goals for the LT1. I wasn't saying anything at negative about the SLS, just illustrating that it is a completely different animal, with different goals, and different market altogether than the base Corvette. No, we're not specifically talking about the price of the car. However, in this case, it is a factor that should not be ignored. Especially when the car brought into the conversation is nearly 3x the price. It becomes very relevant at that point.

Whether the LT1 is a dissappointment of what one expected, it is what it is. It's a mass produced engine for a moderately priced car, to be sold to the masses. It has to meet regulation, live under warranty, and be suitable for daily use. Is it reliable? We can't know that until they're out there and have some miles on them.

As far as your history with your cars, there are C5 owners out there that have never had any problems, and there are Mercedes owners out there that have their roadside and service dept on speed dial. They're all just machines built by people, and s##t breaks.

 

They aren't similar engines though. That's why the GenV vs GenIV comparison was made.

I'll be very interested to see what the truck 6.2 makes. I don't think 430+hp is unreasonable for that engine.

 

Something doesn't make sense to me then...

If HP = torque x RPM/5252. On the LS7 that would mean max HP of 566 (425x7000/5252) but it isn't that high on the cars?

On the LT1, it would mean GM's 450HP estimate is correct... 365x6500/5252 = 452HP. Unless, max RPM is 7,000 which would then equate to 486HP.

Based on this, if it is even remotely correct, my bet is the C7 comes in around 460HP.

I'm probably WAY over simplifying but for sake of discussion, someone please correct my logic!

EDIT: are the torque numbers above at the wheels or the crank?

 

GM has not announced hp numbers so you really don't know what the LT1 s design directive is. I am sorry to hear you are waiting for your engine to blow because of a presumed engine fault that you don't have yet but have heard about. I am sure that your perceived concern has biased your opinion.

I wish you the best and I look forward to GM s actual hp,tq and most important to many of us as enthusiasts the actual performance acceleration and track times...

We each have opinions and ideas based on our perceptions and insights.

I believe an approximate ten percent increase over the 436 hp LS3 is possible with the new 6.2 liter LT1 with it's design improvements and direct injection.

 

Correct!!!! they are designed/engeineered to achive different results.

if you want to compare like engines, then compare the 327(5.3L) in my 1964. it has 360 lb-ft of torque with 300 HP. A "similar" engine, also available in the 1964 Vette has 350 lb-ft of torque. If I extrapolate then the engine with 350 HP should have 292 HP. Correct?
Both are small block Chev's, both based on the same design, yet the one with 350 lb-ft of torque has 375 HP, not 292 HP. The two engines are designed/engineered for different uses.

Just to totally confuse you, here are the 1964 Corvette torque and HP specs for the four engines offered that year.

350 lb-ft with 250 HP
360 lb-ft with 300 HP
350 lb-ft with 365 HP
350 lb-ft with 375 HP.

weird...correct? Try and extrapolate those numbers.

Now do you understand why you can't just extrapolate numbers to derive at a higher torque for a LT1 vs a LS3 of similar design. They(LT1 & LS3) are similar, but still designed differently.

 

I know you can't just extrapolate numbers but...its a good way to get somewhat of a baseline for the LT1. Better than anything we've seen thus far.

 

Well, GM has given us estimated torque and horsepower values and has also shown us a dyno graph of the LT1. I'm using that data, as supplied by GM, to reach my conclusions. What are you basing your assumptions on, besides wishful thinking?

 

OK... I still need someone correct my post #45 above. What is missing? If the torque and RPM numbers are correct, then the LT1 "should" have 450 +/- HP.

 

Joe with all due respect your assumptions on compression ratio comparisons alone are flawed due to you perceptions.

Your comparison of 7 liter ls7 11.1 compression ratio with regards to your statement that the LT1 having only a compression ratio of 11.5 is not enough of a change to add an additional 10 percent hp to the 6.2 liter..

The LS3 has a compression ratio of...10.7 so the increase in compression ratio raises by .8 versus the .4 of your earlier assumption.

Again I do not wish to insult you in anyway as I value your respected insights.

I do feel personally that a 10 percent increase in hp should be achievable with the new LT1 over the very reliable LS3.

My 3.6 liter DI v6 in my fe2 AWD CTS can make up to 323 hp in the camaro or 318 in the Cadillac. With port injection this 3.6 liter engine without vvt achieved 258 hp I believe which shows MORE THAN 10% increase in hp..once direct injection and vvt is combined...(edit) the compression ratio shift from port injection to vvt with direct injection went from 10.2 to 11.5 for a 64 hp increase on a260 hp base number or over a 20 % increase in power...and dam close to 25% improvement..I'm just suggesting 10 % on the ls3 to lt1 upgrade as possible

The gas mileage increase is impressive but more to this discussion.....the hp went up ~ 60 hp recently with a starting point of ~260.

I'd suggest my assumption of an additional 10 % or 43 hp for the ls3 to LT1 is logical and easily achievable.

Thanks for the discussion and of course no disrespect intended.

Just good fun

 

Horsepower at higher RPM's depends on the engine getting enough good air and exhausting the bad air.

The Lt1 gets plenty of air at lower RPM's and the VVT advances the cam to increase the torque at the lower RPM. But, when the LT1 starts hitting the upper RPM's it doesn't have enough cam to breath and it has smaller intake valves and a smaller throttle body then the LS3. GM hasn't released the info on port size or intake manifold runner size/length, but I suspect they are also slightly smaller then the LS3.

Every one keeps wanting to see the 6.2L LT1 to have the same(or nearly the same) HP as the LS7. Well the LS7 has 51 more cu in and it has a hotter cam(breathes better at higher RPM)and much larger intake ports and valves that allows it to have 500 RPM higher redline. The LS7 is designed for horsepower at high RPM's where the LS3 and the LT1 is designed for lower HP at lower RPM's.

People bring up the greater size of the LT1's exhaust vs the LS3. Well, it's 2.75" diameter where the LS7 is 3". Yet people expect the LT1's exhaust to move the same volume of air as the LS7's. Remember that you have to get the air out also, and the LT1's exhaust can't get as much air out as the larger LS7's exhaust, yet people expect the LT1 to match (or nearly match) the LS7's torque and horsepower.


The LS3 was not designed to pull the C6 along on 4 cylinders at low RPM's. The LT1 is designed to pull the C7 along on 4 cylinders. That means the LT1 needs greater torque at low RPMs where the LS3 didn't.

As I've tried to point out, you can design an engine to have higher torque at lower RPMs, but normally you sacrifice higher horsepower at higher RPMs. That's why you can't just extrapolate numbers as the LT1 and the LS3 are really designed differently, even though they have the same displacement.

 

Makes sense... my personal prediction for C7 is now 460HP. Yes, I know that means most folks will see it as an "epic fail" but as I have always contended, HP is but one measure of a car.

 

I enjoy a good discussion. After all, none of us are experts on engine designing. We are just expressing our views as we understand them. I don't believe any of us are totally wrong or totally correct in our posts.

Wouldn't it be great if the guys at GM powertrain(the experts) would just explain what their designs mean, to us laymen. I don't believe they would be giving away "secret" information as I suspect the "experts" at the other auto companies also know how to design an engine.

I believe that most of us would be able to understand what they would be saying and it sure would clear up incorrect beliefs.

 

With or without the optional performance exhaust?

 

Makes perfect sense. So basically, the LT1 is gonna be sacrificing some top end in favor of some more low end torque to allow the car to get better mileage and stay in 4 cylinder mode longer?

 

To play devils advocate...the 6.2 liter L99 does put out 400hp...I would hope the direct injection and other LT1 innovations would allow a 1 0 percent increase over the LS3 and not the L99.

I have some insights to BG and the story goes that the power under peak production does not resemble traditional curves and that this paradym shift is what is transformative with regards to the LT1 acceleration capabilities....

So the final hp numbers may not be what we are guessing them at but that the performance will Be more than we expect given the peak numbers advertised...Specifically because of the power production throughout the curve..

That's the best I have for playing devils advocate.....

 

Yep. While some people believe the relatively low volume of the Corvette has no effect on GM's CAFE, it does. GM can't afford to have their CAFE lowered by even .1MPG because of the Corvette. Below 2,000 RPM, the LT1 has greater torque then the LS7. Cruising down the highway in 7th gear at 1200 RPM at 65 MPH means you need some torque to keep the car in 4 cylinder mode.

MPG is the name of the game at GM and that is what drove the LT1's design. Could the LT1 have been designed to have 500+ horsepower? Sure it could, but with the bulk of the C7's production being built with the basic LT1, it was designed to achieve great gas mileage . Now, later on, when low volume engine options might become available, there most likely will be a trade off to gain some horsepower at the expense of some gas mileage, just as the ZR1 with it's 20 MPG highway isn't as great as the LS3's 26 MPG highway. If you don't believe gas mileage isn't important to GM, then explain why GM spent the money to change the ZR1's gear ratios in the later model's transmission to gain 1 MPG on the highway. Very low volume model, yet they made a change in design to gain 1 MPG on the highway.

I seriously doubt that they made the transmission change because potential ZR1 purchasers were demanding 21 MPG on the highway vs 20.

 

The short & sweet version - this is probably going to be one hell of an interesting dyno curve huh?

 

Gonna be completely honest.... this doesn't sound very appealing to me. It would be nice if they had 2 versions of this, like the Z51 package doesn't come with these shortcomings in high end in favor of low end torque and better mileage. I don't plan on buying a Corvette for it's fuel economy, that's for sure. If it gets great mileage, that's fine, but definitely don't want it at the expense of performance.