Documents Indicate LT5 = 6.2L NA DOHC V8 --- Bottom of Page 5
12-25-2016, 08:10 PM
#121
Le Mans Master
Lots of Laughs!?
That particular C4 ZR-1/LT5 were seriously modified in order to run that long at that speed. For example... transmission/differential coolers. Lower differential ratio as well. Car was lowered beyond stock and ran with no side mirrors etc etc.... No anti roll bars as well. When someone goes and modifies a stock car then all bets are off. In the case of a bone stock C4 ZR-1 and a bone stock C7Z.. I know which one I'll pick for a 24 hour endurance race.
http://jalopnik.com/252795/jalopnik-fantasy-garage-chevrolet-corvette-zr-1
12-25-2016, 10:39 PM
#122
Le Mans Master
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All true when compared to GM V8's, however with that being said the pros outweigh the cons. To achieve 650 HP currently the GEN V has a supercharger which has all the characteristics you describe above.
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johnglenntwo (12-25-2016)
12-25-2016, 11:02 PM
#123
Le Mans Master
Hence their similar but different ZR-1 and ZR1!
(MR handled now!) I remember reading about this back in 1990 and disliking it, and I didn't SC my C5 because of this, BUT, MR!)
But maybe not with the ZR1 and ZR-1stuff:
http://www.corvetteblogger.com/2008/...-Corvette-ZR1/
(Extra street racer performance stuff concessions.)
Last edited by johnglenntwo; 12-26-2016 at 12:12 AM.
12-26-2016, 12:26 AM
#124
12-26-2016, 01:07 AM
#125
Le Mans Master
Right-on! Jalopnik above said it was stock and its records stand!
Unfortunately, this situation is a 'Ball Buster' for some!
Unfortunately, this situation is a 'Ball Buster' for some!
Last edited by johnglenntwo; 12-26-2016 at 05:30 AM.
12-26-2016, 05:23 AM
#126
12-26-2016, 05:32 AM
#127
A few corrections are in order and then some clarifications.
First and foremost, the LT5 had zero modifications done to it...none, zip, nada. In fact, it was an engine rejected for production use because it had a very slight imbalance problem. The Mercury Marine specification for engine balance for the LT5 was a very low number, so low they could balance a nickel on end at idle.
The car had no side mirrors but only the front was lowered. The front air dam was extended about one inch lower...that was the extent of the aero mods done, there was no "etc, etc". The front was lowered to compensate for the rear of the car sitting down due to the extra 500 pounds of weight the car was carrying. There was a full roll cage, fire extinguishing system, telemetry data system, and FIA rules require all repair parts/tools to be carried in the car...over 300 pounds of suitcases with parts/tools were strapped down in the rear hatch area. A fuel cell was used which required the rear anti-roll bar to be removed to make room for it, the front anti-roll bar was retained. Yes, it had transmission and differential coolers and the rear end ratio was changed from the stock 3.45 to 3.07...there were no performance gains from any of those changes, the rear end ratio put the engine at the ~5500 RPM they wanted to run at ~182 MPH to average 175+ MPH (remember the 45 seconds to one minute long pit stops were counted in the 24 hours). The coolers had been added previously in the life of the car because it was used in endurance testing of the LT5 during development, they added no performance to the engine. Yes, I'm trying to refocus on the bone stock engine.
All the modifications done were allowed under the FIA rules for the stock class, I wouldn't say the car was "seriously modified" by any stretch of the imagination. With all the extra weight, it would be more realistic to say the car was seriously handicapped.
Let's not make this into a C7 Z06 vs C4 ZR-1 battle, I never compared the two cars as that would be ridiculous. The point of my post was to show how the broad power range of a DOHC engine makes it adaptable to many performance venues...it doesn't have to be at full throttle/7000+ RPM to make its HP, it can make the same HP at 5500 RPM. The power band doesn't vary more than 20-30 HP from peak HP throughout an almost 2000 RPM range. A 620 HP DOHC NA engine with a 2000 RPM flat power band that doesn't drop below 600 HP with no heat soak/overheating issues vs no power band for the LT4 (it has an increasing straight line up to 6500 RPM/650 HP)...which would you pick?
I am curious how you'll get around the bone stock C7 Z06 overheating after two laps in a 24 hour endurance race...not saying I'd pick the C4, I'm just curious how you would make a record run in a bone stock configuration. The overheating issues are well known and even earned a "sticky status" at the top of the forum, I don't know anybody who would mention "bone stock C7 Z06" and "24 hour endurance race" in the same sentence. The FIA stock class rules will allow extra coolers, I would love to see the stock record bumped up by the C7 Z06.
First and foremost, the LT5 had zero modifications done to it...none, zip, nada. In fact, it was an engine rejected for production use because it had a very slight imbalance problem. The Mercury Marine specification for engine balance for the LT5 was a very low number, so low they could balance a nickel on end at idle.
The car had no side mirrors but only the front was lowered. The front air dam was extended about one inch lower...that was the extent of the aero mods done, there was no "etc, etc". The front was lowered to compensate for the rear of the car sitting down due to the extra 500 pounds of weight the car was carrying. There was a full roll cage, fire extinguishing system, telemetry data system, and FIA rules require all repair parts/tools to be carried in the car...over 300 pounds of suitcases with parts/tools were strapped down in the rear hatch area. A fuel cell was used which required the rear anti-roll bar to be removed to make room for it, the front anti-roll bar was retained. Yes, it had transmission and differential coolers and the rear end ratio was changed from the stock 3.45 to 3.07...there were no performance gains from any of those changes, the rear end ratio put the engine at the ~5500 RPM they wanted to run at ~182 MPH to average 175+ MPH (remember the 45 seconds to one minute long pit stops were counted in the 24 hours). The coolers had been added previously in the life of the car because it was used in endurance testing of the LT5 during development, they added no performance to the engine. Yes, I'm trying to refocus on the bone stock engine.
All the modifications done were allowed under the FIA rules for the stock class, I wouldn't say the car was "seriously modified" by any stretch of the imagination. With all the extra weight, it would be more realistic to say the car was seriously handicapped.
Let's not make this into a C7 Z06 vs C4 ZR-1 battle, I never compared the two cars as that would be ridiculous. The point of my post was to show how the broad power range of a DOHC engine makes it adaptable to many performance venues...it doesn't have to be at full throttle/7000+ RPM to make its HP, it can make the same HP at 5500 RPM. The power band doesn't vary more than 20-30 HP from peak HP throughout an almost 2000 RPM range. A 620 HP DOHC NA engine with a 2000 RPM flat power band that doesn't drop below 600 HP with no heat soak/overheating issues vs no power band for the LT4 (it has an increasing straight line up to 6500 RPM/650 HP)...which would you pick?
I am curious how you'll get around the bone stock C7 Z06 overheating after two laps in a 24 hour endurance race...not saying I'd pick the C4, I'm just curious how you would make a record run in a bone stock configuration. The overheating issues are well known and even earned a "sticky status" at the top of the forum, I don't know anybody who would mention "bone stock C7 Z06" and "24 hour endurance race" in the same sentence. The FIA stock class rules will allow extra coolers, I would love to see the stock record bumped up by the C7 Z06.
As for the C7Z overheating.. what about it? There is a whole bunch of people on this forum that has never suffered from it. Yet they posted some outstanding lap times on various tracks around the USA in over 90degree F weather. Most of the Zs having over heating issues are automatics. Yet there were forum members with A8 Zs that had no issues either.
I'm not comparing the C4 ZR-1 to the C7Z or any other Corvette for that matter either. I was too young to enjoy my Dads C4 ZR-1 back in 1991. I was exactly 4 years old when he brought it home. When my new house is finished I'll be looking to add a Yellow C4 so it can at the very least remind me of my Dad.
12-26-2016, 05:38 AM
#128
Le Mans Master
That's Technically Not Stock!
That 100 octane new Z06 GM tune bump missing! EPA? Drama! Ring time!?
This ain't over!
Last edited by johnglenntwo; 12-26-2016 at 05:48 AM.
12-26-2016, 08:22 AM
#129
I believe this engine will wind up in the 2018 ZR1 and a 2019 Z28, based on the Nurburgring videos of the camo'd car. Both would be ultimate track version of the respective models, and for the Corvette, phase in a new engine type for a completely new architecture (i.e. Mid-engine).
It makes sense for the Z28 battling the GT350 with its Voodoo V8, and while the ZR1 might not have the highest horsepower among Corvettes, it will still be King of the Hill in performance.
I've rrreally been hoping for a mid engine Corvette with a DOHC V8. Fingers crossed.
It makes sense for the Z28 battling the GT350 with its Voodoo V8, and while the ZR1 might not have the highest horsepower among Corvettes, it will still be King of the Hill in performance.
I've rrreally been hoping for a mid engine Corvette with a DOHC V8. Fingers crossed.
Last edited by Latterlon; 12-26-2016 at 08:44 AM.
12-26-2016, 09:34 AM
#130
Le Mans Master
I believe this engine will wind up in the 2018 ZR1 and a 2019 Z28, based on the Nurburgring videos of the camo'd car. Both would be ultimate track version of the respective models, and for the Corvette, phase in a new engine type for a completely new architecture (i.e. Mid-engine).
It makes sense for the Z28 battling the GT350 with its Voodoo V8, and while the ZR1 might not have the highest horsepower among Corvettes, it will still be King of the Hill in performance.
I've rrreally been hoping for a mid engine Corvette with a DOHC V8. Fingers crossed.
It makes sense for the Z28 battling the GT350 with its Voodoo V8, and while the ZR1 might not have the highest horsepower among Corvettes, it will still be King of the Hill in performance.
I've rrreally been hoping for a mid engine Corvette with a DOHC V8. Fingers crossed.
Not slated for 2018!
https://www.corvetteforum.com/forums...post1593731663
12-26-2016, 10:27 AM
#131
12-26-2016, 10:50 AM
#132
Drifting
GT3RS, Viper ACR have stomped mud holes in the C7Z06. This would be a great option for those wanting a track monster with more useable power.
It definitely makes sense in the Z28, whatever edition of vette sees it first will be interesting.
This camo vette running around weather that is a ZR1 or a Z06 with a refresh .. Im still saying that camo vette is running FI.
It definitely makes sense in the Z28, whatever edition of vette sees it first will be interesting.
This camo vette running around weather that is a ZR1 or a Z06 with a refresh .. Im still saying that camo vette is running FI.
12-26-2016, 11:37 AM
#134
The ME will be a 2019 model (see below).
12-26-2016, 01:23 PM
#135
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We usually see Corvette Racing racing adopt a technology 2 years before it comes to production however they've been running DOHC V6 in the Caddy at least two years.
The new Caddy DPi-V.R LMP2 variant is running laps at Daytona now with at least 3 teams. No word of overhead cams although they mention V8 6.2L 600 HP engines....
The new Caddy DPi-V.R LMP2 variant is running laps at Daytona now with at least 3 teams. No word of overhead cams although they mention V8 6.2L 600 HP engines....
12-26-2016, 01:30 PM
#136
Le Mans Master
In all seriousness, does not GM sometimes introduce a powertrain in advance of a bodystyle? Like didn't the infamous Crossfire debut in the last year of the C3 before being picked up in the C4? It's not commonly done, but there is some precedent. I would not expect it here though as there's no hurry to get rid of the LT series.
Last edited by davepl; 12-26-2016 at 01:31 PM.
12-26-2016, 01:34 PM
#137
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http://www.racer.com/imsa/item/13716...ett_1213__693a
Definitely no DOHC in the Caddy however it looks better than the Corvette DP of last year. Plenty of pictures in link above. RPM limited to 7600.
Definitely no DOHC in the Caddy however it looks better than the Corvette DP of last year. Plenty of pictures in link above. RPM limited to 7600.
12-26-2016, 01:47 PM
#138
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Yeah, because -that's- where low end torque comes from. The pushrods.
In all seriousness, does not GM sometimes introduce a powertrain in advance of a bodystyle? Like didn't the infamous Crossfire debut in the last year of the C3 before being picked up in the C4? It's not commonly done, but there is some precedent. I would not expect it here though as there's no hurry to get rid of the LT series.
In all seriousness, does not GM sometimes introduce a powertrain in advance of a bodystyle? Like didn't the infamous Crossfire debut in the last year of the C3 before being picked up in the C4? It's not commonly done, but there is some precedent. I would not expect it here though as there's no hurry to get rid of the LT series.
12-26-2016, 02:14 PM
#139
Le Mans Master
^^^ That's what they said in 1990, which was 26 years ago, and that only lasted a little while. When pushrod V8s crank out 650/650 I won't be standing in any lines to get rid of my pushrods.
DOHC also puts a bunch of the mass on TOP of the engine rather than inside it. Just because it was new in the 1950s doesn't make it the hot ticket.
When DOHC solves a problem I'm having, I'll want it. I just can't think of one. GM has had OHC since the 60s, it's not rocket science. And they've built a bajillion Northstars and high-feature V6s, so it's not like it's beyond their capacity.
But let's face it, if you built a DOHC motor that's 5-6 litres you're still going to need a supercharger for these power levels, or exotic materials to rev it to 8500rpm, so you've already lost the battle.
Now a sweet 8-litre DOHC V12 naturally aspirated I'd be down for, but it's not going to happen. So give me my blower and put the pushrods wherever they fit best.
DOHC also puts a bunch of the mass on TOP of the engine rather than inside it. Just because it was new in the 1950s doesn't make it the hot ticket.
When DOHC solves a problem I'm having, I'll want it. I just can't think of one. GM has had OHC since the 60s, it's not rocket science. And they've built a bajillion Northstars and high-feature V6s, so it's not like it's beyond their capacity.
But let's face it, if you built a DOHC motor that's 5-6 litres you're still going to need a supercharger for these power levels, or exotic materials to rev it to 8500rpm, so you've already lost the battle.
Now a sweet 8-litre DOHC V12 naturally aspirated I'd be down for, but it's not going to happen. So give me my blower and put the pushrods wherever they fit best.
Last edited by davepl; 12-26-2016 at 02:17 PM.
12-26-2016, 02:17 PM
#140
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If GM goes to DOHC in a top level car it would seem that a flat plane crank may be considered as well. With all the positive reviews the Voodoo has received it would be hard not to listen.