Let this be a lesson GM. Dump superchargers and TURBO
08-03-2018, 07:23 PM
#21
Pro Mechanic
Pro Mechanic
I have no aversion to turbos at all. With ball bearing center section over standard journal reduces lag significantly, among other advancements. Didn't GM learn anything from their own Buick Grand National?
Oh yeah, now I remember all the macho gold chain wearing fellas were put off by it being a little V6 (231c.i. / 3.8 liter)....that would crush their lopey V8's...so many butts got hurt, the looks of confusion at the following stop light of how could that quiet car just handed me my ***?
Oh yeah, now I remember all the macho gold chain wearing fellas were put off by it being a little V6 (231c.i. / 3.8 liter)....that would crush their lopey V8's...so many butts got hurt, the looks of confusion at the following stop light of how could that quiet car just handed me my ***?
08-03-2018, 07:29 PM
#22
Burning Brakes
08-03-2018, 09:17 PM
#23
Le Mans Master
Member Since: Oct 2005
Location: Metro Detroit Michigan
Posts: 7,078
Received 1,817 Likes
on
1,085 Posts
08-03-2018, 09:31 PM
#24
Le Mans Master
Member Since: Oct 2005
Location: Metro Detroit Michigan
Posts: 7,078
Received 1,817 Likes
on
1,085 Posts
The notion that a turbo is driven without consuming any power is kind of a myth.
Last edited by Warp Factor; 08-03-2018 at 09:31 PM.
08-03-2018, 11:13 PM
#25
For an upcoming article in Corvette Magazine, near the end of last year, I was in Michigan and interviewed the three key people on the team at Global Propulsion Systems which developed the LT5.
One of the questions I asked them was if a DOHC TTV8 was ever considered for the C7 ZR1.
It was not–for a number of reasons.
1) Packaging. Doing a four cam, twin-turbo engine under the hood of a C7 would have been very difficult.
2) Performance. The 4.2L DOHC TTV8 wouldn't have come close to 708-hp which was the minimum goal for the LT5 and, thanks to the LT5's BAS*, it made 750–and with the GM Performance Parts air box, it's more like 765. Replace the second set of cats with a good aftermarket X-pipe and I bet you'd be at 780
3) The LT5 program was done with a limited budget. Money for an all new engine wasn't there, so they had to leverage what was learned in developing the LT4 as well as many LT4 parts.
4) The cost of integrating DOHC TTV8 into the C7 platform, as well as, certifying it (crash testing, emissions, etc) would have wayyyyy outside the budget the Corvette Team had for the ZR1.
5) Doing a DOHC TTV8 in the final uplevel performance C7 would have been a bad marketing move ahead of the 2020 mid-engine car which will use that engine configuration.
Some say the C7 ZR1 is the best Corvette ever. I'll add this caveat "...for now."
I think it's better to say that the 4Gen ZR1 will be the last great front engine Corvette. That said, the car has some weaknesses: 1) the 8L90 automatic can't shift as responsively as a dual-clutch trans, but then, the easy way around that is to leave the car in drive, put PTM in mode-5 and let computers make you quick around the track and 2) some road tests by mainstream automotive press indicate that, given consistent driving skill and the same tires (PS Cup 2s), a ZR1/ZTK is no quicker 0-60 than a ZO6/ZO7 and, in some situations, doesn't get though turns any quicker. That said, my understanding is the ZR1's suspension tuning is a little towards the understeer end of the spectrum. In the GM C7 parts bin there are different stabilizer bar mounts that, when substituted for the "stock" ZR1/ZTK mounts, will take some of the steady state understeer out of the car. and make it a little quicker in the turns–depending on who's driving, of course.
The problem with a 750-hp Corvette is the same one a 650-hp Corvette has only worse. Short of putting real racing slicks on a ZR1, we've reached the limit of a rear-drive chassis. Future uplevel, high-performance Corvettes must have all-wheel-drive.
Obviously, that's one important reason why the "C8" is a mid-engine car. My guess is the up-level, performance C8 won't come until '21 or '22 and will have a 550-600-hp V8TT driving the rear wheels and 300 or 400-hp worth of electric motors driving the front wheels but only on "demand".
*Big-*** Supercharger
One of the questions I asked them was if a DOHC TTV8 was ever considered for the C7 ZR1.
It was not–for a number of reasons.
1) Packaging. Doing a four cam, twin-turbo engine under the hood of a C7 would have been very difficult.
2) Performance. The 4.2L DOHC TTV8 wouldn't have come close to 708-hp which was the minimum goal for the LT5 and, thanks to the LT5's BAS*, it made 750–and with the GM Performance Parts air box, it's more like 765. Replace the second set of cats with a good aftermarket X-pipe and I bet you'd be at 780
3) The LT5 program was done with a limited budget. Money for an all new engine wasn't there, so they had to leverage what was learned in developing the LT4 as well as many LT4 parts.
4) The cost of integrating DOHC TTV8 into the C7 platform, as well as, certifying it (crash testing, emissions, etc) would have wayyyyy outside the budget the Corvette Team had for the ZR1.
5) Doing a DOHC TTV8 in the final uplevel performance C7 would have been a bad marketing move ahead of the 2020 mid-engine car which will use that engine configuration.
Some say the C7 ZR1 is the best Corvette ever. I'll add this caveat "...for now."
I think it's better to say that the 4Gen ZR1 will be the last great front engine Corvette. That said, the car has some weaknesses: 1) the 8L90 automatic can't shift as responsively as a dual-clutch trans, but then, the easy way around that is to leave the car in drive, put PTM in mode-5 and let computers make you quick around the track and 2) some road tests by mainstream automotive press indicate that, given consistent driving skill and the same tires (PS Cup 2s), a ZR1/ZTK is no quicker 0-60 than a ZO6/ZO7 and, in some situations, doesn't get though turns any quicker. That said, my understanding is the ZR1's suspension tuning is a little towards the understeer end of the spectrum. In the GM C7 parts bin there are different stabilizer bar mounts that, when substituted for the "stock" ZR1/ZTK mounts, will take some of the steady state understeer out of the car. and make it a little quicker in the turns–depending on who's driving, of course.
The problem with a 750-hp Corvette is the same one a 650-hp Corvette has only worse. Short of putting real racing slicks on a ZR1, we've reached the limit of a rear-drive chassis. Future uplevel, high-performance Corvettes must have all-wheel-drive.
Obviously, that's one important reason why the "C8" is a mid-engine car. My guess is the up-level, performance C8 won't come until '21 or '22 and will have a 550-600-hp V8TT driving the rear wheels and 300 or 400-hp worth of electric motors driving the front wheels but only on "demand".
*Big-*** Supercharger
08-04-2018, 06:10 AM
#26
Le Mans Master
Member Since: Oct 2005
Location: Metro Detroit Michigan
Posts: 7,078
Received 1,817 Likes
on
1,085 Posts
Sounds plausible. Mid-rear engine should give more room for height (overhead cams), and width (turbo packaging), since they don't need to leave room for the rear wheels to steer. With turbos, they'd also be able to reduce the size of the mufflers. Might also leave enough room for electric motors in the front, motors which GM may already have on the shelf, used in their other hybrid cars.. Might be a rather heavy car with the batteries, we'll see what happens with battery technology.
Last edited by Warp Factor; 08-06-2018 at 05:04 AM.
The following users liked this post:
C7rob (08-04-2018)
08-04-2018, 09:17 PM
#29
Pro Mechanic
Pro Mechanic
I think there's a couple of facts we need to think about with respect to vehicle weight.
First...batteries. When we think about batteries and electric motors, let's not consider our imaginary C8 high-performance variant in the same way we think about hybrids (ie: Prius, Volt, etc) or EVs (Tesla, Chevy Bolt, etc). The electric motors which might power the front of a C8 "ZO6" would only operate when the vehicle's full drive torque is required, ie: say ⅞-ths throttle and above nor would they be capable of moving the car on their own. They would be acting only as a "power adder".
Second...AWD hardware. Yeah, batteries don't have very good power density and, thus, weigh a lot for the energy stored, but, since the electric motors in a C8 "ZO6" would only need enough battery power for, say, 40 seconds of operation and would be, at least partially, recharged by regenerative braking, they might weigh less than you think. The other way to do AWD–mechanically–would also make a big contribution to vehicle weight via a driveline from the engine in the back to the front wheels, a front drive axle (like in a 4WD truck) and axle shafts with CVs.
Lastly, this is a lot of speculation on my part.
First...batteries. When we think about batteries and electric motors, let's not consider our imaginary C8 high-performance variant in the same way we think about hybrids (ie: Prius, Volt, etc) or EVs (Tesla, Chevy Bolt, etc). The electric motors which might power the front of a C8 "ZO6" would only operate when the vehicle's full drive torque is required, ie: say ⅞-ths throttle and above nor would they be capable of moving the car on their own. They would be acting only as a "power adder".
Second...AWD hardware. Yeah, batteries don't have very good power density and, thus, weigh a lot for the energy stored, but, since the electric motors in a C8 "ZO6" would only need enough battery power for, say, 40 seconds of operation and would be, at least partially, recharged by regenerative braking, they might weigh less than you think. The other way to do AWD–mechanically–would also make a big contribution to vehicle weight via a driveline from the engine in the back to the front wheels, a front drive axle (like in a 4WD truck) and axle shafts with CVs.
Lastly, this is a lot of speculation on my part.
Last edited by Hib Halverson; 08-04-2018 at 09:17 PM.
08-04-2018, 09:32 PM
#30
Race Director
Would it be possible to utilize small lithium ion battery packs in the front trunk to spool the turbos to minimize lag and optimize performance?
maybe that’s what we will see in the years to come?
maybe that’s what we will see in the years to come?
08-05-2018, 10:50 PM
#31
Safety Car
With Turbos I don't think you will ever get that instant low rpm grunt the LT4 has. The LT4 and LT5 both have ridiculous amounts of torque at 1000 rpm and I suspect getting the same result from a Turbo setup would be challenging at best. The chief advantage of the Turbo always has been it is more efficient. It uses waste engine heat to produce more power while the supercharger consumes crankshaft power to make more power. However, at low just off idle rpms the waste heat isn't sufficient to drive as much boost as the supercharger can at those rpms. Maybe GM will provide an electrically driven Turbo that will bring the blower up to speed at low engine rpms and phase out as engine rpms increase to where it can be driven by exhaust gases.
Bill
Bill
08-06-2018, 06:00 AM
#32
Race Director
Supercharging for the c7 was done for packaging.
as the c8 goes rear mid engine the packaging requirement changes and more easily accomodates turbo technology.
the hot v layout on dohc engines was a gm initial design that didnt get the green liht for years.
mercedes and others successfully utilize the hot v layout as their engines are dohc.
why the c7 didnt utilize turbos with the LT1 derived powerplant in the front engine c7 z06 or zr1 is simply packaging.
the c8 resolves the packaging constraint so we will see twin turbos on the upmaeket model of the c8
as the c8 goes rear mid engine the packaging requirement changes and more easily accomodates turbo technology.
the hot v layout on dohc engines was a gm initial design that didnt get the green liht for years.
mercedes and others successfully utilize the hot v layout as their engines are dohc.
why the c7 didnt utilize turbos with the LT1 derived powerplant in the front engine c7 z06 or zr1 is simply packaging.
the c8 resolves the packaging constraint so we will see twin turbos on the upmaeket model of the c8
08-06-2018, 06:46 AM
#33
Le Mans Master
Member Since: Oct 2005
Location: Metro Detroit Michigan
Posts: 7,078
Received 1,817 Likes
on
1,085 Posts
That said, my buddy's twin turbo 911 was able to make 16 lbs boost at 2000 rpm when I checked, so that's pretty impressive for a turbo.
Last edited by Warp Factor; 08-06-2018 at 06:46 AM.
08-10-2018, 06:00 AM
#34
Le Mans Master
not the right place to save a buck, they learned than on the lt4 but haven't seemed to step up the size here.
hopefully they are really efficeint, I don't like to blow through a small straw, they look restrictive to me and undersized for the task at hand
let the caddy guys keep it and put some real intercoolers on it!!
08-10-2018, 06:35 AM
#35
Le Mans Master
Member Since: Oct 2005
Location: Metro Detroit Michigan
Posts: 7,078
Received 1,817 Likes
on
1,085 Posts
the air/water intercoolers are nicely integrated but dinky and look like they will suffer accordingly
not the right place to save a buck, they learned than on the lt4 but haven't seemed to step up the size here.
hopefully they are really efficeint, I don't like to blow through a small straw, they look restrictive to me and undersized for the task at hand
let the caddy guys keep it and put some real intercoolers on it!!
not the right place to save a buck, they learned than on the lt4 but haven't seemed to step up the size here.
hopefully they are really efficeint, I don't like to blow through a small straw, they look restrictive to me and undersized for the task at hand
let the caddy guys keep it and put some real intercoolers on it!!
08-10-2018, 07:08 AM
#37
Did someone say we reached the limits of RWD chassis?
What about McLaren making same power levels? Or GT2RS?
We in that statement is we in corvette not we in the general sense of all RWD cars.
Come on guys, what we have reached is the limits of what a Corvette is capable of doing given its price point and development budget.
What about McLaren making same power levels? Or GT2RS?
We in that statement is we in corvette not we in the general sense of all RWD cars.
Come on guys, what we have reached is the limits of what a Corvette is capable of doing given its price point and development budget.
08-10-2018, 07:15 AM
#38
Originally Posted by JerriVette
Would it be possible to utilize small lithium ion battery packs in the front trunk to spool the turbos to minimize lag and optimize performance?
maybe that’s what we will see in the years to come?
maybe that’s what we will see in the years to come?
08-10-2018, 09:43 AM
#39
Race Director
