Point/Counterpoint: DOHC v OHV

[edram454]

It is certainly not personal with me. I call it as I see it. I will not defend a lousy lt4 car. Its a good car, not a super car. All those vehicles are direct comparisons in specific cases. The ls platform is good no question. i just think chevy fell short on the lt4. what about the ones that just blow up after 10 miles?? I have heard of a couple of those. I just feel no way in hell can a lt4 run 24 hours and average 176mph or complete the 200 hour durability test the lt5 had to endure and survive. 200 hours of flooring the beast time after time again and live. some of these lt4's cant even survive 10 miles of parking lot driving. any way it is just my opinion. by the way the nurburgring vette was involved in a crash so the time was not reported. dont take anything personal it is just my opinion. I have had 7 corvettes but have not bought a new c7 even though it is a nice car and the interior is best improvement. I would wait for the next rendition of the lt4 to see if the improvement made warrants super car status. All corvettes are nice but just a little critical of the so called top vette. long live dohc cars. At least Ford got it right with the coyote!

ed ramos #3028

[KILLSHOTS]

Originally Posted by XfireZ51

Guys,

The idea of the thread was to offer viewpoints re: the engine architectures. Let not take things in a personal direction.
Also, I don't think there has been any indication that a Z06 has gone anywhere near sub 7min at the Ring.

You are correct about the lap time. I had scanned the story but had not read it completely. Although there are reports of the 2015 Z06 with Z07 package having run a 7:08, a 7:06 and a 6:59, GM will not confirm these reports and on closer examination, I haven't been able to find any confirmed time for the car. Apparently, the Nurburgring has placed a temporary ban on "official" lap times for some reason, so the car is probably running these times, but GM is playing by the 'Ring rules and not sanctioning them. On a speculative basis, a 7-minute lap doesn't seem out of the question to me, since a C6 Z06 ran a 7:22.

[Paul Workman]

Perhaps a more objective analysis could be attained by considering dyno results; in particular "power under the curve".

That said, it is worth mentioning an analysis of results would show the (FBI) ZR-1s produced the fastest 3-car team aggregate 5* out of 6 attempts at the local Crown Point Corvette Club's annual Corvette Shootouts*. The event is made up of Chicago area Corvette clubs, and has been flooded with LSx's, and last fall a couple new LTx's. Various videos showed time and time again the lighter LSx cars jumping out front off the line, but at the 1/8 point the ZR-1s had reeled them in and beating them at the "top end".

*The Team Trophy was not awarded to the ZR-1 team on two occasions; one year the ZR-1s were not registered for trophy runs (but time slips showed they would have won had they been registered), and (for one year only) the trophy was tied into bracket racing rules instead of the aggregate speed of the top 3 club cars.

Analysis of the last two WANNA GO FAST events in Chicago clearly shows two things: 1) Forced induction dominated the 264 cars participating in the (2014) event, and the top 45 out of 264 speeds were all forced induction (with one possible exception), and a good number of them used the DOHC architecture. (See list below)

WANNAGOFAST Monee, IL 6-21,22, 2014:

Nissan GT-R Alpha 16 (Twin Turbo)
2006 Dodge Viper (Nth Moto) (Twin Turbo)
Nissan GT-R Alpha 16 (Twin Turbo)
Nissan GT-R Alpha Omega (Twin Turbo)
2011 Lamborghini Gallardo Superleggera (Twin Turbo)
Nissan GT-R (Twin Turbo)
Nissan GT-R (Twin Turbo)
Mercedes-Benz E63 AMG (Twin Turbo)
2012 Nissan GT-R (Twin Turbo)
1994 Toyota Supra (Turbo)
Nissan GT-R Alpha (Twin Turbo)
2008 Porsche 997 Turbo (Twin Turbo)
2006 Dodge Viper (Twin Turbo)
2009 Nissan GT-R (Twin Turbo)
Toyota Supra (Turbo)
Toyota Supra (Turbo)
2000 Pontiac Trans-Am (Turbo)
Mitsubishi Evo 2 (Turbo)
2010 Nissan GT-R (Twin Turbo)
1997 Toyota Supra (Sound Performance) (Turbo)
2013 Nissan GT-R Black Edition (Alpha) (Twin Turbo)
1985 Oldsmobile Cutlass (Turbo)
2011 Cadillac CTS-V (Vengeance) (S/C)
2006 Lamborghini Gallardo (Heffner/Nth Moto) (Twin Turbo)
2006 Chevrolet Cobalt SS (Turbo)
C5 Corvette (N/A)
2012 Nissan GT-R (Twin Turbo)
2012 Chevrolet Corvette ZR-1 (S/C)
2004 Lamborghini Gallardo Heffner (Twin Turbo)
2010 Corvette ZR-1 (S/C)
2009 Chevrolet Corvette (S/C)
Mercedes-Benz SLS AMG Black Series (F/I)
2009 Chevrolet Corvette ZR-1 (S/C)
2006 Dodge Viper (Twin Turbo)
1993 Mitsubishi 3000GT VR-4 (Turbo)
Nissan GT-R (Twin Turbo)
1998 Chevrolet Corvette (Tigershark) (Turbo)
Dodge Viper (S/C)
2006 Dodge Viper (Twin Turbo)
Nissan GT-R (Twin Turbo)
Nissan 300ZX (Turbo RB26)
2000 Honda S2000 (Turbo)
2003 Chevrolet Corvette (S/C)
2008 Porsche 911 Turbo (Twin Turbo)
1993 Toyota Supra (Turbo)

There's little doubt the 4-valve DOHC architecture has significant advantages over OHV (pushrods), at least in some venues.

Car and Driver article: DOHC vs. OHC:

http://www.caranddriver.com/columns/...mg-slug-it-out

But that said, where the DOHC architecture has a performance advantage, equally evident is the $/hp advantage of the OHV approach.

Mitigating factors?

Kevin makes a good point regarding technological advances. But, his insinuating that (peak?) hp/$ is the quintessential approach to analysis dismisses other virtues that other architectures (DOHC) have, e.g., power under the curve (for one!). How about durability or driveability?

And, so it goes...

[Mystic ZR-1]

Indy 1994
Roger Penske found a loop hole in the Indy rules and
with Mercedes/Illmor built a 209 cubic inch turbo OHV, 2 valve per cylinder, V8
running 1.86 bars abs of boost (that's about 12.6 pounds, not really a big number
in the serious turbo world, a pure race motor, not a stock block...)
that knocked it out of the park! Pole and race win.
Some estimates were over 1100 hp in qualifying trim!
That's about 5hp/cu in!
Rules allowed a little more boost and a few more cubes for OHV motors.
OHV/DOHC???

[Kevin]

Originally Posted by edram454

It is certainly not personal with me. I call it as I see it. I will not defend a lousy lt4 car. Its a good car, not a super car. All those vehicles are direct comparisons in specific cases. The ls platform is good no question. i just think chevy fell short on the lt4. what about the ones that just blow up after 10 miles?? I have heard of a couple of those. I just feel no way in hell can a lt4 run 24 hours and average 176mph or complete the 200 hour durability test the lt5 had to endure and survive. 200 hours of flooring the beast time after time again and live. some of these lt4's cant even survive 10 miles of parking lot driving. any way it is just my opinion. by the way the nurburgring vette was involved in a crash so the time was not reported. dont take anything personal it is just my opinion. I have had 7 corvettes but have not bought a new c7 even though it is a nice car and the interior is best improvement. I would wait for the next rendition of the lt4 to see if the improvement made warrants super car status. All corvettes are nice but just a little critical of the so called top vette. long live dohc cars. At least Ford got it right with the coyote!

ed ramos #3028

lt5's were popping in the BG parking lot. No company is perfect and the lt5 is far from it. Is GM worse then most others, I tend to say yes. There's a reason I didn't even look at a gm for my last two daily drivers. I'd still buy a c6z06 tomorrow if I could.

[Paul Workman]

Originally Posted by Kevin

lt5's were popping in the BG parking lot.

WHAT are you talking about, Kevin

[edram454]

Kevin is probably referring to the time a young lady in charge of starting the zr-1's and parking them after assembly, would start them in the freezing cold and rev them up big time without warming up the car and thus caused damage with the cam chains etc... they stopped lt5 production for a while until they found out what was being done. The young lady said that is the way she started up her car in the morning so she did the same with these brand new zr1 lt5 dohc cars. These motors were tested in practically every condition except the ultra high revving in the freezing cold. That was the only episode a lt5 blew up in the parking lot. No other v8 had to endure the 200 hour durability test in order for it to be installed and sold in gm cars. I really dont think many lsX engines can withstand 200 continual hours of floorings...I would bet on that. lt5's are not perfect but they are durable and they do make power and they dont really on power adders to make power.

As far as the z06, I like them very much. Unfortunately I have seen recently quite a few having major engine failure. I have talked to very knowledgeable people in the corvette world and they say they are not surprised. It happens more than people know. I love the ls7 427 but now I would be hesitant to buy one. Maybe its there owners abusing them or not maintaining them properly?? who knows.. What I do know is that they are not as durable as an LT5. I am a big fan of the ls7, very big fan and it has been depressing to see some of them lose engine oil pressure. I like thels7 better than the lt4 because of its torque and its natural power.

ed ramos #3028

[XfireZ51]

If anyone has any doubt, I would take a C7Z in a New York second. The car is a technological tour de force. It's amazing what GM has done chassis wise to rival much more expensive hardware. Stuff like the E-Diff is awesome.
I'd love to speculate on what's going in back of the rumored mid-engine tho.

[KILLSHOTS]

Originally Posted by edram454

Kevin is probably referring to the time a young lady in charge of starting the zr-1's and parking them after assembly, would start them in the freezing cold and rev them up big time without warming up the car and thus caused damage with the cam chains etc... they stopped lt5 production for a while until they found out what was being done. The young lady said that is the way she started up her car in the morning so she did the same with these brand new zr1 lt5 dohc cars. These motors were tested in practically every condition except the ultra high revving in the freezing cold. That was the only episode a lt5 blew up in the parking lot. No other v8 had to endure the 200 hour durability test in order for it to be installed and sold in gm cars. I really dont think many lsX engines can withstand 200 continual hours of floorings...I would bet on that. lt5's are not perfect but they are durable and they do make power and they dont really on power adders to make power.

As far as the z06, I like them very much. Unfortunately I have seen recently quite a few having major engine failure. I have talked to very knowledgeable people in the corvette world and they say they are not surprised. It happens more than people know. I love the ls7 427 but now I would be hesitant to buy one. Maybe its there owners abusing them or not maintaining them properly?? who knows.. What I do know is that they are not as durable as an LT5. I am a big fan of the ls7, very big fan and it has been depressing to see some of them lose engine oil pressure. I like thels7 better than the lt4 because of its torque and its natural power.

ed ramos #3028

The difference is the internet. We've heard about an isolated number (3, maybe?) of LT4 failures because those of us who pay attention to these things have instantaneous access to such info now due to the existence of the worldwide web. The reason we didn't hear about it back then was because we lacked the instant access to EVERYTHING that we have today, but even the nearly-bulletproof LT5 had its share of failures when new. Because of this, I have decided to FEEL that the LT5 could not withstand a 200-hour durability test, and I have also decided to FEEL that there's no way it could have run 24 hours straight at nearly 176 MPH.

[Mystic ZR-1]

Originally Posted by KILLSHOTS

.......EVERYTHING that we have today, but even the nearly-bulletproof LT5 had its share of failures when new. Because of this, I have decided to FEEL that the LT5 could not withstand a 200-hour durability test, and I have also decided to FEEL that there's no way it could have run 24 hours straight at nearly 176 MPH.

And I suppose you FEEL Elvis and Hitler are still alive?