LT5: If the GM LF3 were 6.2L.... 725hp!
01-05-2017, 02:06 PM
#1
Le Mans Master
Thread Starter
LT5: If the GM LF3 were 6.2L.... 725hp!
I was wondering what the LT5 might be like, and since we don't seem likely to get any news, speculation is the next best thing, so:
I figured the current GM LF3, which is 3.6L and produces 420hp is a good place to start. It's a DOHC, twin-turbo, high feature motor with a long list of impressive features. But the main one is that it produces 117hp/L with Cadillac driveability, idle, and warranty.
If you simply took that motor and scaled it out to 6.2L, our current displacement, you'd be at 725hp. And that's with no stress, stock levels of power and boost that they're running today in the Cadillac XTS.
I'm not claiming we're going to get a 6.2L DOHC twin-turbo LT5, but you can see from the numbers what's trivially possible using tech that's already a decade old...
I figured the current GM LF3, which is 3.6L and produces 420hp is a good place to start. It's a DOHC, twin-turbo, high feature motor with a long list of impressive features. But the main one is that it produces 117hp/L with Cadillac driveability, idle, and warranty.
If you simply took that motor and scaled it out to 6.2L, our current displacement, you'd be at 725hp. And that's with no stress, stock levels of power and boost that they're running today in the Cadillac XTS.
I'm not claiming we're going to get a 6.2L DOHC twin-turbo LT5, but you can see from the numbers what's trivially possible using tech that's already a decade old...
Last edited by davepl; 01-05-2017 at 02:07 PM.
01-05-2017, 02:52 PM
#2
Race Director
I was wondering what the LT5 might be like, and since we don't seem likely to get any news, speculation is the next best thing, so:
I figured the current GM LF3, which is 3.6L and produces 420hp is a good place to start. It's a DOHC, twin-turbo, high feature motor with a long list of impressive features. But the main one is that it produces 117hp/L with Cadillac driveability, idle, and warranty.
If you simply took that motor and scaled it out to 6.2L, our current displacement, you'd be at 725hp. And that's with no stress, stock levels of power and boost that they're running today in the Cadillac XTS.
I'm not claiming we're going to get a 6.2L DOHC twin-turbo LT5, but you can see from the numbers what's trivially possible using tech that's already a decade old...
I figured the current GM LF3, which is 3.6L and produces 420hp is a good place to start. It's a DOHC, twin-turbo, high feature motor with a long list of impressive features. But the main one is that it produces 117hp/L with Cadillac driveability, idle, and warranty.
If you simply took that motor and scaled it out to 6.2L, our current displacement, you'd be at 725hp. And that's with no stress, stock levels of power and boost that they're running today in the Cadillac XTS.
I'm not claiming we're going to get a 6.2L DOHC twin-turbo LT5, but you can see from the numbers what's trivially possible using tech that's already a decade old...
01-05-2017, 06:03 PM
#5
Its going to have big jugs and headers from hooker and it can only be had with a cherry picker.
The following 3 users liked this post by Bob U:
The following users liked this post:
4GS7 (01-07-2017)
01-06-2017, 11:15 AM
#12
Le Mans Master
Thread Starter
It'd still be "more than we can use" for most of the time, like the 650 is now. If it were NA power, you'd have that soggy NA bottom end for traction, but with twin turbo, it'd be linear power like the LT4.
I'm of the opinion that the ONLY way the Corvette audience will move to turbos is if they're getting something in return, like a DOHC V8. It has to be a clean break from the LSV8 platform, you can't just hang turbos off an LT4 and call it the L88 and be done with it.
I don't know why that is. But it's how I feel...
I'm of the opinion that the ONLY way the Corvette audience will move to turbos is if they're getting something in return, like a DOHC V8. It has to be a clean break from the LSV8 platform, you can't just hang turbos off an LT4 and call it the L88 and be done with it.
I don't know why that is. But it's how I feel...
Last edited by davepl; 01-06-2017 at 11:15 AM.
01-06-2017, 11:50 AM
#14
Safety Car
Member Since: Jan 2012
Location: Cin City
Posts: 4,885
Received 481 Likes
on
317 Posts
St. Jude Donor '14
I was wondering what the LT5 might be like, and since we don't seem likely to get any news, speculation is the next best thing, so:
I figured the current GM LF3, which is 3.6L and produces 420hp is a good place to start. It's a DOHC, twin-turbo, high feature motor with a long list of impressive features. But the main one is that it produces 117hp/L with Cadillac driveability, idle, and warranty.
If you simply took that motor and scaled it out to 6.2L, our current displacement, you'd be at 725hp. And that's with no stress, stock levels of power and boost that they're running today in the Cadillac XTS.
I'm not claiming we're going to get a 6.2L DOHC twin-turbo LT5, but you can see from the numbers what's trivially possible using tech that's already a decade old...
I figured the current GM LF3, which is 3.6L and produces 420hp is a good place to start. It's a DOHC, twin-turbo, high feature motor with a long list of impressive features. But the main one is that it produces 117hp/L with Cadillac driveability, idle, and warranty.
If you simply took that motor and scaled it out to 6.2L, our current displacement, you'd be at 725hp. And that's with no stress, stock levels of power and boost that they're running today in the Cadillac XTS.
I'm not claiming we're going to get a 6.2L DOHC twin-turbo LT5, but you can see from the numbers what's trivially possible using tech that's already a decade old...
The heads only flow 205cfm, my cylinder head port on them flows 280cfm for an insane 39% increase.
The car sees about 14-15psi at 1000' and I ran a 12.3 in stock form, 12.1 with drag radials on the stock tune. I was first into the 10s at 127mph at the quarter mile with our intake filters, our catless exhaust, and a tune at 20psi with drag radials.
Last edited by Ben@WeaponX; 01-06-2017 at 01:22 PM.
The following users liked this post:
houdini13 (01-06-2017)
01-06-2017, 12:29 PM
#16
It'd still be "more than we can use" for most of the time, like the 650 is now. If it were NA power, you'd have that soggy NA bottom end for traction, but with twin turbo, it'd be linear power like the LT4.
I'm of the opinion that the ONLY way the Corvette audience will move to turbos is if they're getting something in return, like a DOHC V8. It has to be a clean break from the LSV8 platform, you can't just hang turbos off an LT4 and call it the L88 and be done with it.
I don't know why that is. But it's how I feel...
I'm of the opinion that the ONLY way the Corvette audience will move to turbos is if they're getting something in return, like a DOHC V8. It has to be a clean break from the LSV8 platform, you can't just hang turbos off an LT4 and call it the L88 and be done with it.
I don't know why that is. But it's how I feel...
01-06-2017, 01:17 PM
#17
Le Mans Master
Member Since: Dec 2005
Location: Port Arthur, Texas 77642
Posts: 8,475
Received 331 Likes
on
241 Posts
I am extremely excited about the 4 valve future, yes the heads, valves, and cam swaps will be a lot more, but the potential is huge! The LF4 like in my ATS V would be a better comparison IMO. It has titanium Pankyl rods like the ZR1 and better turbos. It is rated to 464hp, but they mostly dyno around 425whp on a dyno jet, which seems closer to 500bhp.
The LF4 is a higher-performance variant of the LF3 for use in the Cadillac ATS-V. Changes to the LF3 include:
Turbochargers with low-inertia titanium-aluminide turbines and vacuum-actuated wastegates for more responsive torque production
Compressors matched for peak efficiency at peak power levels, for optimal track performance
Patent-pending low-volume charge-cooling system that optimizes packaging efficiency and maximizes boost pressure
Lightweight titanium connecting rods that reduce inertia of the rotating assembly, complementing the quick-spooling turbochargers.
Peak boost increased to 18 PSI (from 12 PSI)
Higher-flow fuel injectors
Oil pan baffling for better oil flow at high cornering speeds.
01-06-2017, 01:29 PM
#18
If the leaked VIN card that showed the LT5 is to be believed, it would suggest the LT5 is naturally aspirated, since all the other listed engines mentioned power adders if they had them. Matching the LGX 3.6L N/A engine's HP/L results in ~577 HP.
If the engine ends up being Gen V based and they use the 92mm stroke to hit 6.2L then that might have piston speeds limit the RPM rather than head flow with 4VPC.
If the engine ends up being Gen V based and they use the 92mm stroke to hit 6.2L then that might have piston speeds limit the RPM rather than head flow with 4VPC.
01-06-2017, 01:48 PM
#19
Tech Contributor
Member Since: Oct 1999
Location: Charlotte, NC (formerly Endicott, NY)
Posts: 40,096
Received 8,930 Likes
on
5,334 Posts
Why 8K rpm? It doesn't necessarily need to rev that high. Especially if GM continues to follow the high torque at lower rpm philosophy which seems to work well on the track. That is one of the reasons the Vette can get by without a DCT. Why have a DCT with super fast shifts if the need to shift is cut in half or more?
Bill
Bill
01-06-2017, 08:05 PM
#20
