Originally posted by h22sparkle
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Does it have IRS?
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It's not the same without a third pedal or should it be first pedal?
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I think you all miss the point of why a push rod engine is still attractive. Weight and packaging. A push rod engine is lighter and smaller by design. That's why the Viper still uses it. That's not me just saying it because I'm a fanboy trying to defend my company. I'm saying it because I have personally spoken with the Viper engine designers and they say the extra weight and dimensions aren't worth the small gain in efficiency. The guys in SRT aren't at all about cutting corners. They push the limit on everything, so if there was a better way to make a huge V10 they probably would have moved on from a pushrod in the last 20 years.
KISS right?Comment
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I've said it before in this thread, but I'll mention it again because it applies.
My CTS-V makes a little over 400hp (crank). It is VERY difficult to actually use that power! I can't imagine how absolutely bonkers a 700+hp car must be... and how briefly I'd get to enjoy that power on public roads before I was SERIOUSLY violating the law!
Pushrod engines are "archaic"... they are an old design, though they do continue to benefit from new technology.
As H311RA151N mentioned, DOHC engines are good at higher RPM. They offer more compact valvetrains, and more precise control over valve timing.
OHC engines offer a simpler design. And while they're not made to rev to the moon (though my V revs plenty high!) they're still capable of producing plenty of power in a usable powerband.
At this point, horsepower is really just for racing and bragging rights. Most of us aren't considering a $60,000+ vehicle as a race car project. Most people that purchase these crazy cars (Hellcat, ZR1, ZL1, CTS-V, Viper, Shelby GT500) aren't going to do any serious racing in them. Therefore, the cars are for bragging rights... and .3 seconds of giggle-inducing acceleration on public roads.
Pushrod engines can do that as well as OHC engines. At this point, N/A engines can do it almost as well as forced induction!
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I'm not gonna lie, and take it as you will, but back when I was working on the Viper I had a Challenger for 3 months given to me through work. It was 470hp. Yes the 6.4 was well balanced for the platform, but after getting used to it and driving the Viper and HC I began to feel the 6.4 was under powered. I was in a company car so I never dangerously went over the speed limit, but mind you the morning commute was often going 85-90mph with traffic! That's plenty of room to enjoy the car. I also had a co worker who purposefully left for work at 5am every morning only living 6 miles from work to enjoy topping out his Porsche when the roads were empty.
The drive to and from work can make the day all that much better if you get to do a few 0-100 pulls and I always thought the Challenger could use a little more than 470hp and it can put it down (kinda lol). But unless we're talking trucks, any car over 40k is a car bought for bragging right anyway. The HC just so happens to be swinging the biggest dick at the moment haha.Comment
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Why would you want to press that amount of power on a public road. Maybe on the highway on a nice strip in a controlled environment. Then you can always take it to the track then when your done fill it up and take it home without it being on a flatbed.
Its the convenience you pay for is what a lot of people don't realize not exactly just bragging rights I can respect that. You can always turn the power down but I know a lot of folks would prolly say turn down for what? LolComment
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From a legal standpoint, I know what happens first hand at just 109mph in a 70.
I had my licence and registration in my hand ready to give to the cop when he walked up, his first words were "We're past that, please step out of the vehicle." I got out and his next words were "Your under arrest put you hands behind your back." No shit. Happened February 14th 2011 in Republic Missouri. I didn't "go to jail" but I was taken to jail and released. I got it knocked down to 72 in a 70 with an attorney, had to take an 8 hour class that cost me $150 called "Alive at 25," one year of unsupervised probation, $830 in fines and $1500 in attorney fees.
My point is with a blip of the throttle in this thing you will land your ass in hot water. 700hp doesn't really belong on the street. And $60,000 for a car you no longer have a license to drive or cannot get insurance for will suck.
Another thing to think about is how many people will you kill or hurt when you smash into someone at over 150mph. That's called involuntary manslaughter. The Hellcat might be built to protect it's passengers in the event of a wreck at high speeds but the car it hits likely isn't. Just my aspect on it.
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That's true about cars over $40k!Originally posted by domesticated View Post
And yeah, I suppose it goes hand in hand with what people always say about boost... you SAY you'll be ok with a little, but then you want more. And more . And more.
In my experience, I've only had 400ish to play with. Never more. My other cars are 200hp and 117hp... so 400 is absolutely monstrous! Put me in a 700hp car, and I might feel that the CTS-V is weak. I have nothing more to compare to, and I know that I can barely use what I have... so "more" isn't something that even registers to me. Once I have that comparison, I might be spoiled too!
I haven't driven the CB7 since I bought the CTS-V (well, no more than just around the block...) I wonder if it will seem slow to me. The H22 seemed respectably quick the last time I drove it (and that was after my Grand Prix GTP... but regardless of the brutish power, that 4 speed automatic made the car seem slow.)
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Well on my way to work I often pass cops doing 85 in a 70, because everyone else on the left is doing the same speed. Also a Fiat 500 base can go over 110. People are all about not breaking the law and being smug about it, but when there's nobody else around it's only your ass and your choice. It's pretty rare I drive faster than traffic, I don't have much of a need to. I never went faster than traffic in a company vehicle. But my personal car? If it's 5am and there isn't a car in sight, I might hit triple digits and then back off. You say a blip on the throttle and you're in trouble, I don't see anyone complaining about an Ariel Atom which runs low 11s or sport bikes for that matter. It's about how you drive. When I was younger I got tickets all the time, lost my license, all that good stuff. But the last time I had a ticket was 3-4 years ago and it had been a few years before that. The worst ticket I had was 140 in a 70 when I was a teenager. In Montana, not a car in sight. The cops laser had a further range than my eye sight lol. And lastly, with traction control and stability management, as long as you don't turn that stuff off on public roads you won't pull a Mustang and you won't crash unless you are being reckless.Comment
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As far as that comment, My Honda is way more fun to drive than my Charger. It may be slower, but it feels faster because it's way less refined. Loud noises, shake, and torque steer make the WOT runs much more pleasurable. It's all about perception. I found myself doing 100 in a Highlander one day coming home from work cause there was no traffic around for me to relate my speed to and the thing was so quiet and smooth in a straight line. I was like "Oh shit!" Slowed down in a hurry.Originally posted by deevergote View Post
Fast cars seem slower when they're more refined and the HC is an L car so it's very quiet with the windows up and the stereo on.Comment
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As for a blip on the throttle landing you in trouble, 1JZ/R154 S13 will do it in a heart beat. Been there and done it.
Last edited by H311RA151N; 08-04-2014, 07:23 PM.
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OHC engines have better VE (volumetric efficiency) and usually better TE (thermal efficiency).Originally posted by deevergote View Post
Typically, an OHC multivalve engine will have more valve curtain area, resulting in more flow for a given lift. In order to do it, push rod engines need huge valves which increases valve train mass significantly. Also, the mass of the valve head makes it harder to stabilize as the valve gets larger, limiting RPM.
Valve train mass on a well designed OHC design is significantly less because the parts are smaller, there are no pushrods, etc.
Further, you have more freedom in port and combustion chamber design with OHC designs, which improves efficiency more.
Finally, things like cam phasing and variable valve systems are more effective on OHC designs.Comment
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I would hardly call a10-15%+ gain in specific output "minor." Consider the 120+ HP per liter Ferrari's latest engines are producing, and suddenly that "small"increase in power puts the STOCK Viper at or above 900HP. So Dodge could make the engine smaller, saving a fair bit of the weight gain in the process, as well as the size lost to bigger heads. Hence Ferrari being able to belt 600+ HP out of a 6.0 liter NA V12 vs an 8.3 liter V10 or 6.2L supercharged V8.Originally posted by domesticated View Post
I understand the specific advantage of an OHV engine being more compact, but I think it was proven long ago that is a relatively weak support for it. What it really comes down to is cost. Pushrods are cheap. Cars like the LFA and pretty much every front engine Ferrari have proven that DOHC, high tech engines and low hood lines aren't mutually exclusive, nor is light weight. But they are expensive. Also, with the size of modern cars and all the other safety mandated BS, I just don't think the engine size holds that much weight in most cases. In the Vette or Viper, maybe. Challenger? Not a chance (although I get why they used it). In the Hellcat, it is fundamentally a cost saving reason, as well as appealing to the "die-hard" muscle guys.Comment
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Those V12 Ferrari's are extremely heavy. Like 700-800 pounds heavier than the Viper. How much is in the powertrain, I have no idea. And it's not like they have astoundingly more features now that the new Viper has been refined. But the lower revving 8.4L has way more torque, and because of American fuels the Viper runs about 2 points lower compression than most Ferrari's. Two points of compression on an 8.4L will add quite a bit of power. I'm not trying to hype up the pushrod issue, but I'm telling you directly from the engine designers they said going away from pushrods was simply not beneficial. An OHC 8.4L would be huge. And the trade off peak horsepower for usable torque was well worth it.Comment
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That challenger has to be heavy approximately 4,162lbs 1,892kg. If the parents own the car and they lend it out to their kids the red key fob stays with the parents and the black key fob which reduces power goes to the child unless they hack it.Originally posted by owequitit View PostComment
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They aren't heavy. The F12 Berlinetta is about 50lbs heavier than the Viper, despite being over 7" longer and an inch taller. Cars like the 458 are the lightest in their class.Originally posted by domesticated View Post
Since the F12 is the most similar car Ferrari has to the Viper, we'll talk about them for a second.
1) The Ferrari makes about 14% less peak torque with 33% less displacement. Yes, it is less torque, but it has HIGHER specific torque output than the V10 in the Viper. It also makes about 90 more horsepower, over a much broader powerband, with that same 33% smaller engine. It isn't a dig on the Viper. It is fact that being able to optimize the engine to breath more efficiently, under more conditions is largely due to the DOHC design, which allows better port geometry, broader powerbands, more optimized valve angles, CC designs, and makes it easier to implement things like cam phasing (independent cam phasing on the exhaust is worth about 4-5% in its own right, something you can't do with an OHV engine without an extremely complex multi-piece cam).
Further, the Ferrari is able to better optimize this geometry all the way up to 8700RPM. Since we both know that HP is a function of torque and RPM, being able to maintain the torque curve to higher RPM automatically=more power.
I haven't looked up the Viper's dyno yet, but the Ferrari makes 80+% of peak torque from 2000RPM to about 8,000RPM, and slowly tapers off to 8700RPM. The Ferrari's workable powerband is bigger than the TOTAL powerband on the Viper! So while it would appear that the Ferrari is a lot "less driveable" by virtue of a torque peak 1,000RPM higher, it just isn't true with modern technology. Of course you can compare dyno plots from old engines like the F22, H22, B18C, B16 etc versus new engines like the K series and J series. What you will find is much flatter torque curves on modern OHC engines with curves that just don't drop off as quickly as engines that can't optimize the valve timing. The old misconception of "peaky" power delivery from high revving engines, is just that: a misconception. Modern high revving engines are making their torque all over the place. It is often less total torque by virtue of engine size, but IMO, they are also more drivable and flexible than bigger OHV engines.
IMO, the J series epitomizes the term "flat torque curve" with the curve rising almost vertically to 2K RPM and then staying within 10% of peak until about 6K. Engines like in the F12 are even better, as are the K series (when the VTEC dip is removed with tuning). They aren't quite as flat, but as for % available at any given RPM, they are better overall.
2) The other thing to consider is that Viper's engineering team has a bit of a problem with going to DOHC, because the Viper has ALWAYS had a honking OHV V10. Loyalists would bitch to no end if they used a smaller DOHC engine. One thing I have learned about loyal American Muscle enthusiasts is A) they want pushrods and B) they want to 'prove' that "American Muscle" (read: large displacement OHV engines) are just as good based on how much power they are making. The fact that the engine is 30-40% larger to do it is beside the point for these guys, who always brag about torque to begin with.
3) As to the Viper's Specific output, yes a bump in compression would provide some increases. But, we also both know that the curve of improvement from increasing compression is not linear. So a bump from 10:1 to 11:1 will not provide as much improvement as the bump from 9:1 to 10:1 did. Even a huge bump in compression on the V10 isn't going to improve specific output from 76 hp/L to 115 hp/L. Just to provide a touch of relative perspective to this specific output, the current SOHC, non-cam phasing (I know the Viper does have cam phasing) J35 in the Accord is sitting at 80HP/L with the ability to run on 87 octane (relatively low compression).
In comparison, the LT1 in the Vette is slightly lower than the Viper at 73 hp/L, despite also being a bleeding edge OHV tech engine.
As for assertions on a DOHC 8.4L V10, it would be big. But, they would have been able to shrink it about 15-30% and still ended up with the same result. With engineering, they could have gotten such an engine into the same space. But again, it would have cost more money.
4) I feel like part of it is that it would be bad for Chevy and SRT to say "we are using OHV engines derived from volume motors to save costs." That is not as true with the Viper as it used to be (no more production V10, even though it is still based on the original 1991 engine), but it is still very true with the Vette. Instead, GM got smart and said, well "it has better packaging advantages than a DOHC engine." This was a good way to not make buyers feel that they were getting a lower tech engine for money's sake. Consider that the C4 was able to fit a 5.7L DOHC V8 in the same exact space that they fit the LT1 into. The main differences were that the DOHC Lotus V8 version made 75-105 more HP from the same displacement (without any of today's common technology), and was significantly more expensive.
5) I wasn't saying anything against OHV engines. But the pure science of it is that higher tech, OHC designs are more efficient at turning unit of volume into HP. It is just the way it is. To be honest, my favorite car on the market right now is a 5.0 Mustang (that's an engine to die for), and a close second as far as sports cars are concerned is the new 'Vette. I lament that there are no plans to keep the LS7 around after the Camaro Z/28.
But, the science is the science.Comment
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