So Here is what I hear.. 6.2L V8 Only A Stop Gap Engine For C7
01-22-2013, 12:19 AM
#121
Instructor
01-22-2013, 07:56 AM
#122
Melting Slicks
Remind me to never tell you a secret.
I call BS
01-22-2013, 09:39 AM
#123
Instructor
You need to write a novel. I would buy it.
01-22-2013, 10:03 AM
#125
Le Mans Master
http://wot.motortrend.com/next-gen-l...#axzz2IiP73xdK
While about a year ago, there was alot of talk about using the smaller 5.5L engine, this, from MotorTrend makes sense. I believe that while GM looked at many options to obtain power and efficiency targets, that the 6.2 gave the best result in the end, for an N/A motor.
What's on the drawing board for the future? Who knows? But I would think that GM would like to do two things as non negotiable. One, keep the performance level of the base engine competitive, and two, maintain N/A on that base engine. Right now, cylinder deactivation is all the rage in fuel economy, and mpg is an important number.
Now, I could see a supercharged 5.5L in the future, but probably not on the base car. Maybe, if it achieved the near 600HP mark and retained near the fuel economy it could appear in a Hi-Po version? And perhaps someone more knowledgeable than myself can correct me, but I would think that AFM would be a nightmare to engineer in a boosted engine?
But again, it would seem that GM wants to keep the base engine N/A for a myriad of reasons, and the 6.2 with AFM is their best solution at the moment.
Displacement is indeed 6.2 liters, not 5.5 liters as rumored, and the RPO number is LT1, a designation well-known to the Corvette faithful. The key enabling feature of the new small block is cylinder deactivation. The Corvette was to be first with that technology, but the layout of the car was unsuited because of the rear transmission and various mounting solutions, it was an NVH nightmare in 4-cylinder mode. Those problems have been overcome now, and the system has been optimized to allow a wide operating range in the 3.1-liter V-4 mode. As it turns out, fuel economy is BETTER with a 6.2-liter engine, because smaller displacements reduce the amount of time the engine can operate in 4-cylinder mode, so bigger displacement saves more fuel. Counterintuitive, but true. Active Fuel Management applied to a performance valvetrain is unique, Chevy says. With its 6600-rpm engine speed fuel cutoff, this is the highest-speed valvetrain with cylinder deactivation. Cylinders 1, 7, 6, and 4 get deactivated.
What's on the drawing board for the future? Who knows? But I would think that GM would like to do two things as non negotiable. One, keep the performance level of the base engine competitive, and two, maintain N/A on that base engine. Right now, cylinder deactivation is all the rage in fuel economy, and mpg is an important number.
Now, I could see a supercharged 5.5L in the future, but probably not on the base car. Maybe, if it achieved the near 600HP mark and retained near the fuel economy it could appear in a Hi-Po version? And perhaps someone more knowledgeable than myself can correct me, but I would think that AFM would be a nightmare to engineer in a boosted engine?
But again, it would seem that GM wants to keep the base engine N/A for a myriad of reasons, and the 6.2 with AFM is their best solution at the moment.
01-22-2013, 11:25 AM
#126
Le Mans Master
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GM has said that they looked at a turbo V6 for the Corvette, but for their targeted power and fuel efficiency for the base car that the turbo V6 came up short versus the V8 they developed(LT1).
01-22-2013, 01:20 PM
#127
Race Director
Look to 2016 to bring the 8 speed Auto tranny with a 5.5L V8 worth some type of blower attached and around 600 ponies. This is from someone I know at GM. I was told that this is why a "boost" gage is already integrated to the configurable dash. The Gen5 6.2 will then reside in Camaro and a Tahoe/Suburban variant SUV. A 6.2 with a blower could also be online for a Z06 type car also.
CORRECTION THAT SHOULD SAY 500+ Ponies MY MISTAKE SORRY.
CORRECTION THAT SHOULD SAY 500+ Ponies MY MISTAKE SORRY.
01-22-2013, 02:00 PM
#128
Safety Car
Guys, it's right in the engineering papers. Lower displacement base engine is not gonna happen for CAFE reasons. AFM regimes were exhaustively tested and it was found that the bigger engines remained in AFM mode longer than smaller displacement, and the 6.2 gave the best result. The bigger engine gets better fuel economy. We have to change how we think about engine displacement vs power and economy.
The more likely reason the engines ended up a 6.2L is power, not economy. Think about. How powerful would the 5.5L be? 10% less torque everywhere would net an estimated power output of 405hp. The C7 would then be heavier and less powerful than the outgoing C6. Try to sell that.
I'm sure the racing team would like a 5.5L as would GM to develop at the same time, but powerterrain team failed to meet spec with a 5.5L.
That is way more likely the reason vs. efficiency. AFM works in low load situations right? So if you are cruising with a 2.7L V4 instead of a 3.1L V4 do you really think the torque is not plenty? Still over 200lb/ft! Plenty to maintain speed. Then whenever high load would be needed a smaller 5.5L V8 would come to life, again saving fuel.
Or you can believe the GM marketing that 3.1L is the ideal size... What is more likely? My story or the one you were given?
01-22-2013, 03:59 PM
#129
I'm not buying it. Displacement vs. power is as it always has been, the optimization is dynamic. Depending on thrust needed there is an ideal engine size to obtain optimum efficiency. If bigger is more fuel efficient then why drop to V4 in the first place?
The more likely reason the engines ended up a 6.2L is power, not economy. Think about. How powerful would the 5.5L be? 10% less torque everywhere would net an estimated power output of 405hp. The C7 would then be heavier and less powerful than the outgoing C6. Try to sell that.
I'm sure the racing team would like a 5.5L as would GM to develop at the same time, but powerterrain team failed to meet spec with a 5.5L.
That is way more likely the reason vs. efficiency. AFM works in low load situations right? So if you are cruising with a 2.7L V4 instead of a 3.1L V4 do you really think the torque is not plenty? Still over 200lb/ft! Plenty to maintain speed. Then whenever high load would be needed a smaller 5.5L V8 would come to life, again saving fuel.
Or you can believe the GM marketing that 3.1L is the ideal size... What is more likely? My story or the one you were given?
The more likely reason the engines ended up a 6.2L is power, not economy. Think about. How powerful would the 5.5L be? 10% less torque everywhere would net an estimated power output of 405hp. The C7 would then be heavier and less powerful than the outgoing C6. Try to sell that.
I'm sure the racing team would like a 5.5L as would GM to develop at the same time, but powerterrain team failed to meet spec with a 5.5L.
That is way more likely the reason vs. efficiency. AFM works in low load situations right? So if you are cruising with a 2.7L V4 instead of a 3.1L V4 do you really think the torque is not plenty? Still over 200lb/ft! Plenty to maintain speed. Then whenever high load would be needed a smaller 5.5L V8 would come to life, again saving fuel.
Or you can believe the GM marketing that 3.1L is the ideal size... What is more likely? My story or the one you were given?
But it seems consistent enough with what the engineers at GM are saying.
We also all know the 6.2 is alot more torquey down stairs than the LS1/LS6 engines are. A 5.5 would have even less down stairs than that.
01-22-2013, 04:27 PM
#130
Safety Car
No doubt the 5.5 V8 would come online more often but that doesn't mean 6.2L is optimal. How much more often? The Monte Carlo is a heavier car, the 5.3L is smaller than 5.5L and the 5.3L does not have the technology the new LT1 engines have.
And yes, I think it's how the AFM was set up that overwhelmed other variables. I bet the new ones are way more intrusive.
A 5.5L build like the LT1 would also have VVT and therefor the massive amount of torque down below.
GM offered no proof that the 6.2L is more economical. People say "engineering papers", what papers? I don't see no publication ready research. Whenever engineers addressed themselves to us they did so in a PRish setting. Big picture, easy to digest info is all we got. I think it's very likely a smaller V8 is more economical. But knowing what we know about the LT1 output you can bet the "estimated" output on a 5.5L would be around 400hp which is not acceptable.
And yes, I think it's how the AFM was set up that overwhelmed other variables. I bet the new ones are way more intrusive.
A 5.5L build like the LT1 would also have VVT and therefor the massive amount of torque down below.
GM offered no proof that the 6.2L is more economical. People say "engineering papers", what papers? I don't see no publication ready research. Whenever engineers addressed themselves to us they did so in a PRish setting. Big picture, easy to digest info is all we got. I think it's very likely a smaller V8 is more economical. But knowing what we know about the LT1 output you can bet the "estimated" output on a 5.5L would be around 400hp which is not acceptable.
Last edited by SBC_and_a_stick; 01-22-2013 at 04:29 PM.
01-22-2013, 04:33 PM
#131
Le Mans Master
I'm not buying it. Displacement vs. power is as it always has been, the optimization is dynamic. Depending on thrust needed there is an ideal engine size to obtain optimum efficiency. If bigger is more fuel efficient then why drop to V4 in the first place?
It's not that "bigger is more fuel efficient" is that the larger displacement allows for the AFM to kick in and stay in V4 mode longer, thus saving more fuel in low load cruising.
The more likely reason the engines ended up a 6.2L is power, not economy. Think about. How powerful would the 5.5L be? 10% less torque everywhere would net an estimated power output of 405hp. The C7 would then be heavier and less powerful than the outgoing C6. Try to sell that.
Well, yes power targets had to be met. They were not about to release the C7 with less power than the C6. Now they could have very well engineered a 5.5 to hit the 450+ mark but they would've probably had to do it without AFM. Now that 5.5 may have been a little better than the 6.2 on mpg, when the 6.2 is in full 8 mode. But it would've still fallen short of the desired mpg mark. The 6.2 allowed them to hit both the power and mpg marks, they got their cake and ate it too. Also to mention that to get the 5.5 to hit the power mark, may have compromised durability, driveability of the car.
I'm sure the racing team would like a 5.5L as would GM to develop at the same time, but powerterrain team failed to meet spec with a 5.5L.
That is way more likely the reason vs. efficiency. AFM works in low load situations right? So if you are cruising with a 2.7L V4 instead of a 3.1L V4 do you really think the torque is not plenty? Still over 200lb/ft! Plenty to maintain speed. Then whenever high load would be needed a smaller 5.5L V8 would come to life, again saving fuel.
The major obstacle in AFM is the NVH, I believe in one of the interviews this discussed that they had tested smaller displacement but they could not overcome the noise vibration levels satisfactorily, but the 6.2 provided acceptable results.
Or you can believe the GM marketing that 3.1L is the ideal size... What is more likely? My story or the one you were given?
It's not that "bigger is more fuel efficient" is that the larger displacement allows for the AFM to kick in and stay in V4 mode longer, thus saving more fuel in low load cruising.
The more likely reason the engines ended up a 6.2L is power, not economy. Think about. How powerful would the 5.5L be? 10% less torque everywhere would net an estimated power output of 405hp. The C7 would then be heavier and less powerful than the outgoing C6. Try to sell that.
Well, yes power targets had to be met. They were not about to release the C7 with less power than the C6. Now they could have very well engineered a 5.5 to hit the 450+ mark but they would've probably had to do it without AFM. Now that 5.5 may have been a little better than the 6.2 on mpg, when the 6.2 is in full 8 mode. But it would've still fallen short of the desired mpg mark. The 6.2 allowed them to hit both the power and mpg marks, they got their cake and ate it too. Also to mention that to get the 5.5 to hit the power mark, may have compromised durability, driveability of the car.
I'm sure the racing team would like a 5.5L as would GM to develop at the same time, but powerterrain team failed to meet spec with a 5.5L.
That is way more likely the reason vs. efficiency. AFM works in low load situations right? So if you are cruising with a 2.7L V4 instead of a 3.1L V4 do you really think the torque is not plenty? Still over 200lb/ft! Plenty to maintain speed. Then whenever high load would be needed a smaller 5.5L V8 would come to life, again saving fuel.
The major obstacle in AFM is the NVH, I believe in one of the interviews this discussed that they had tested smaller displacement but they could not overcome the noise vibration levels satisfactorily, but the 6.2 provided acceptable results.
Or you can believe the GM marketing that 3.1L is the ideal size... What is more likely? My story or the one you were given?
01-22-2013, 04:46 PM
#132
Melting Slicks
But the 5.5 would have to come online much more often than the 6.2. That's why the Monte Carlo's 5.3 with AFM didn't make it over to the Fatmaro, because it hardly got to work itself into Fuel Sipping mode too often. The story I got from an owner of one I got was that the 5.3 pretty much everytime he used anything more than bare minimum throttle the AFM would have to bring up all 8 cylinders again. Whether that's a symptom of the engine being smaller than a 6.2 or the AFM system I dunno.
But it seems consistent enough with what the engineers at GM are saying.
We also all know the 6.2 is alot more torquey down stairs than the LS1/LS6 engines are. A 5.5 would have even less down stairs than that.
But it seems consistent enough with what the engineers at GM are saying.
We also all know the 6.2 is alot more torquey down stairs than the LS1/LS6 engines are. A 5.5 would have even less down stairs than that.
And the AFM in my 6.0L L76 2007 GMC Sierra was completely worthless. Only time it ever engaged was either while coasting or on the freeway that was level or downhill and under 65 MPH. In fact, one time I set the cruise at 60 mph on a flat freeway and it went into V4 mode...I then turned on the AC and it kicked into V8 mode. Seriously.
I noticed ZERO difference in long-term fuel efficiency after having it disabled.
01-22-2013, 05:11 PM
#133
I thought the Camaro's equipped with the 6.2L and auto tranny had AFM? Pretty sure they do.
And the AFM in my 6.0L L76 2007 GMC Sierra was completely worthless. Only time it ever engaged was either while coasting or on the freeway that was level or downhill and under 65 MPH. In fact, one time I set the cruise at 60 mph on a flat freeway and it went into V4 mode...I then turned on the AC and it kicked into V8 mode. Seriously.
I noticed ZERO difference in long-term fuel efficiency after having it disabled.
And the AFM in my 6.0L L76 2007 GMC Sierra was completely worthless. Only time it ever engaged was either while coasting or on the freeway that was level or downhill and under 65 MPH. In fact, one time I set the cruise at 60 mph on a flat freeway and it went into V4 mode...I then turned on the AC and it kicked into V8 mode. Seriously.
I noticed ZERO difference in long-term fuel efficiency after having it disabled.
01-22-2013, 07:06 PM
#134
Safety Car
Aftermarket AFM-everything delete and monster cam FTW!
01-22-2013, 08:35 PM
#136
Le Mans Master
I wondered about this the other day!
Gee, I kind of made this calculation 7-years ago!
01-22-2013, 10:01 PM
#138
Safety Car
No way a 5.5L V8 supercharged engine will be base. V8 is premium enough for a base car and it keeps the price low. A C7 supercharged will have costs near the C6 ZR1 and look how affordable that one is.
01-22-2013, 10:21 PM
#139
Instructor
I was not comparing the base corvette to the viper...I said they would have to come out with an engine and car to compete with the Viper as it is the only real competition in America I see for a true all around GT Sports car. I was not agreeing that a 5.5L engine was coming...but rather that something making over 600hp was coming and needed.
Maybe you need to concentrate on reading comprehension instead of being judgmental on every posts you disagree or read
Last edited by Brock63; 01-22-2013 at 10:33 PM.
01-22-2013, 10:25 PM
#140
Instructor
Not sure I get the gist of your statement. 
I was referring to Brock63's comparing a 600 HP $100,000 Viper to a 450 HP $55,000 car as he was dissing (I believe) the Corvette as inadequate. My comment was that Corvette has a peer to the Viper in the (take your pick) Z06 or ZR1.
I agree with you that I'll take the base C7 Z51, run close enough to the Viper to be satisfying, if in fact I could not beat it. And contrary to his comment, I would be living in a refined car, which the Viper isn't.
I was referring to Brock63's comparing a 600 HP $100,000 Viper to a 450 HP $55,000 car as he was dissing (I believe) the Corvette as inadequate. My comment was that Corvette has a peer to the Viper in the (take your pick) Z06 or ZR1.
I agree with you that I'll take the base C7 Z51, run close enough to the Viper to be satisfying, if in fact I could not beat it. And contrary to his comment, I would be living in a refined car, which the Viper isn't.
The Viper...whether a fan or not...and I am not...stepped up their game this year....more leather all around that is sewn and wrapped on everything, steering wheel mounted controls, performance designed seats by Sabelt, launch control, stability control...
My entire intent that you missed is that corvette will need to evolve and continue to improve their offerings if they want to keep up with Viper in sales.....Viper is 600+ horsepower so until a new C7 is released to compete...people will be wanting more. No matter how much you argue power to weight ratios...handling...etc....majority of people only look at horsepower and then maybe torgue and then appearance of vehicle for buying decision.
Last edited by Brock63; 01-22-2013 at 10:34 PM.