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Discussion in '2010 Hennessey Venom GT' started by CitroenSM, Nov 19, 2007.
aye pushrods are stoneage
Pushrods are used in with greater success in lower revving engines not so in supercars.
An 8.3L normally aspirated engine can surely produce much power than 600BHP, the M5 engine for eg. produce 510 bhp. For the same cylinder cross section 4 valves provide much better volumetric efficiency than 2, hence DOUBLE overhead camshafts are required for high performance in high revving engines.
ferrari are using 5 valves per cylinder for more responsive engines & for this its impossible to use PUSHRODS. With OHC you can extract much more power eg. the V-TEC, VVTI engines from toyota and honda engines when tuned properly produce around 130 bhp per litre. The s2000 has 109 hp/L and the viper 59 hp/L.
"but there's no denying pushrods are obsolete"
Name a car that puts out over 500hp below 6500rpm, and achieves a combined average of more than 20mpg.
Hint: It's got a 7.0L pushrod V8 and costs less than half as much as most vehicles that can touch it.
Well, a GT2, for example. Several Brabus and AMG things too, Continental GT, Several RUF's and other such as Gemballas, etc., Da Maybach, An S or a CL 600....
And who cares about the RPM anyway? Or the fuel consumption when talking about supercars? And don't hit me with that Corvette crap again- it's been gone trough in hundreds of threads named "this vs Z06". You can go post there.
Putting more valves in a cylinder costs about half a pence and adds a negligible weight. Combustion process becomes more optimal, which results in a better output and reduced fuel consumption. And this was figured out about about 50 years ago. Of course, if you put an engine that's big enough in a vehicle that's light enough, it'll go fast. But if it had a more advanced engine of same displacement it'd go faster. But Americans don't just bother.
"And who cares about the RPM anyway? Or the fuel consumption when talking about supercars?"
"...which results in a better output and reduced fuel consumption"
Where exactly were you headed with this one? Also, I've yet to see your point proven. Allow me...
2008 911 GT2: 3.6L Flat-6 (Twin-turbo, I might add): 530hp @6500RPM, 22mpg. (Source: Theautochannel.com)
2008 Continental GT: 6.0L V12 (TT again): 552hp @6100RPM, 17mpg. (Source: continentalgt.co.uk)
2008 Maybach 57 S: 6.0L V12: 450hp @4800RPM, 16.4mpg. (Source: maybach-manufaktur.com)
2008 Z06: 7.0L V8: 505hp @6200RPM, 21mpg (Source: Chevrolet.com, supercars.net)
How many V-Tec motors won LeMans GT1? Didn't pushrods pretty much dominate the Dayton Prototype class? And, I am still waiting to see that DOHC engine that is pushing 8000HP like the OHV NHRA dragsters.
The only argument I'm hearing in favor of DOHC motors is higher revs. Woohoo! The Ferrari screams because of the Vette's growl! I don't get how this is a favorable argument.
Higher revs means your engine is working harder to produce the same amount of power. That's all there is to it. Saying that an engine is more efficient when it has to turn harder and get worse fuel consumption to produce an equal amount of power at a higher price is kind of a useless point, is it not?
Look, DOHC or pushrod, it doesn't matter. The point is that 500 hp from an 8.4 L engine is pathetic! Most car companies can get 500 hp from a pencil sharpener these days!
ok. notice the porsche makes peak power at 8000rpm. the viper makes it at 5600. if the viper v10 was spun to 8000 rpm it would make a lot more than 605 hp. the '08 viper makes 600 hp at 6100rpm, which is really good. even my stupid intrepid makes power at around 6000-6500. the viper engine is not weak, it's just lazy. and reserved. plus the '03-'07 viper your referencing makes 100 more lb-ft of torque, and at 1150 rpm lower. the '08 viper's 560 lb-ft is even better.
not only do big displacement pushrod motors not have have to work as hard by revving higher, but they also make a hell of a lot more torque than a dohc motor of the same hp. more torque equals better driveability and more get-up at lower rpm.
If I am not mistaken, this was to be powered by a viper V-10 at one point in its conception...
Lol, then going along the same lines, you're basically saying a diesel (lower revs) that produces the same power as a gasoline engine (higher revs) is better.
It's all about the power band. Not how high or hard an engine has to work to produce power. if i can make 1000hp at 1500 rpm, that's great. but on a track where i'm going to be going a lot faster than engine speeds that low, the power is irrelevant.
just my two cents...
It's interesting that you should openly put stats showing OHV's put out higher Torque than DOHC but then bash the OHV.
Are you unaware of the fact that Torque, not HP, is what matters? It's how much lbs/ft the engine can apply to the asphalt that moves the car not how much energy it expends doing it.
I respect the venom gt...
I'm sorry. I actually had to sign up after I read this guys rant about pushrod engines. After I said, "What?!" outloud and laughed quietly to myself I realised this fellow clearly was not properly educated on the dynamics and evolution of engine performance. Clearly over looking the fact that this "ancient" engine is MAKING 1200 HORSEPOWER. I don't care what the hell sort of valvetrain it has, that kind of power is fantastic. I mean honestly, why are you #%!@ing about the valvetrain of ALL things. Maybe I'm the crazy one, but I seem to recall top fuel dragsters making 10, 000 hp with ohv hemi-style engines...which were first designed in 1901. I suppose they are laughable too huh?