Corvette C6 Topgear Track time.

[Guibo]

Originally Posted by mindgam3 I do think you're contradicting yourself though by comparing engines with HP/l and then implying its not important other than countries with displacemtn tax or racing series with strict displacement limits. People are saying HP/litre is useless for comparing engines and then here Guibo is using it to put forward an arguement....

I don't think I've contradicted anything I've said at all. What I've been saying is: hp does not rise linearly with displacement (all else being equal). You and I agree to that. Prior to that, I haven't said anything about displacement taxes and racing regs, other than to say I seriously doubt the reason why F1 has displacement limits is because the cars were getting big and heavy. I already know large displacements are penalized in other countries. But unfettered from such restrictions (ie. in a totally free market), hp/l in and of itself is not a meaningful measure. Just like a peak hp number in and of itself tells you nothing about how good (or bad) a car is. Surely, no one here argues for the opposite case?...

[mindgam3]

Originally Posted by Guibo Originally Posted by mindgam3 I do think you're contradicting yourself though by comparing engines with HP/l and then implying its not important other than countries with displacemtn tax or racing series with strict displacement limits. People are saying HP/litre is useless for comparing engines and then here Guibo is using it to put forward an arguement.... I don't think I've contradicted anything I've said at all. What I've been saying is: hp does not rise linearly with displacement (all else being equal). You and I agree to that. Prior to that, I haven't said anything about displacement taxes and racing regs, other than to say I seriously doubt the reason why F1 has displacement limits is because the cars were getting big and heavy. I already know large displacements are penalized in other countries. But unfettered from such restrictions (ie. in a totally free market), hp/l in and of itself is not a meaningful measure. Just like a peak hp number in and of itself tells you nothing about how good (or bad) a car is. Surely, no one here argues for the opposite case?...

I think i agree with you; hp/litre can give you some idea of how good an engine is, but it doesen't give you the whole picture unless you combine it with other facts.

Depends what you mean by "the opposite case". Graywolf624 (amongst others)suggests in his posts that hp/l is a completely meaningless figure, which i disagree with. On the same lines I also said Hp/l is also related to how efficient the engine is in terms of power (not neccesarily to do with the amount of fuel that burnt and emmisions)

[RC45]

HP/l is a meaningless measurement - expect to those who place value on it.

MPG or l/100km on the other hand has value - only because people want and need to know how far the vehicle will travel on a given mount of fuel.

You want to know why we say HP/l is the "ricers" last resort?

Because producing 100hp/l means nothing - when the engine is onl 1.6l in size.

You still only have 160hp - at the crank - to haul around a 2600lb+ car.

So, while the HP/l number may sound good - it only underlines the fact that the car in quesiton is an underpowered piss of shit econobox

HP/lb and lb/HP are much more telling numbers in ANY comparison of performance cars.

[fedezyl]

Well, just one question, why is it then, that most high performance car manufacturers use OHC instead of pushrods, as well as formula one and basically most racing engines? oh yeah....it must be that they are dumb and spend most of their R&D money buying marihuana and smoking it in big bongs together....
As far as you RC45, I do respect you as a person, but frankly I get somewhat tired of your post, it seems everytime someone says something that you don't agree with you just load up your flame thrower and burn whoever is in front of you, you just don't seem to be able to communicate with people, besides having some sort of fanatical behaviour on anything regarding your point of view, the same goes to Graywolf624 to a lesser extent.
In any case, back to the argument about the Corvette, none of us can really say wich design is best or worse since we are not engineers and frankly we don't know crap about them other than what we read on the internet and whatever books we read. But, and this is a BIG but, there are some facts that we cannot ignore and those are that most manufacturers use OHC for a reason, most try to squeeze out as much power from a given engine volume as they can (for sports car's engines) and as st-anger said, wich I think is the only individual here in this forum with enough knowledge and experience to say that a Porsche was and is WAAY better than a Corvette.

[RC45]

Originally Posted by fedezyl Well, just one question, why is it then, that most high performance car manufacturers use OHC instead of pushrods, as well as formula one and basically most racing engines? oh yeah....it must be that they are dumb and spend most of their R&D money buying marihuana and smoking it in big bongs together....

The reason they pursue this avenue is two fold:

First, engineers like to try new stuff - just to see what can be done - with no regard for cost or complexity.

Secondly, the manufacturers are able to sell their products for the outrageous prices they need to recoupe the costs. This limits access to these technological "marvels" to an elite few.

Witness the fact that econ-car engines are multi-valve OHC designs - but unable to reach the peak horsepower numbers needed as they are build on a budget.

Originally Posted by fedezyl As far as you RC45, I do respect you as a person, but frankly I get somewhat tired of your post, it seems everytime someone says something that you don't agree with you just load up your flame thrower and burn whoever is in front of you, you just don't seem to be able to communicate with people, besides having some sort of fanatical behaviour on anything regarding your point of view, the same goes to Graywolf624 to a lesser extent.

Nope - I just felt dumber after reading that tripe.

Originally Posted by fedezyl In any case, back to the argument about the Corvette, none of us can really say wich design is best or worse since we are not engineers and frankly we don't know crap about them other than what we read on the internet and whatever books we read.

That is another stupid statement.

This is like saying because we are not doctors human health is total mystery and what ever doctors say is like the Word of God...

Not being an engineer actually allows you as a consumer to fairly evaluate the crap they build and tell them how it really is.

Originally Posted by fedezyl But, and this is a BIG but, there are some facts that we cannot ignore and those are that most manufacturers use OHC for a reason, most try to squeeze out as much power from a given engine volume as they can (for sports car's engines)

With unlimited budgets and products absurdly over priced to recoup costs - sure it's the way to go.

The opposite is of course that all the OHC econo-engines are just that - cheap econo-engines.

Originally Posted by fedezyl and as st-anger said, wich I think is the only individual here in this forum with enough knowledge and experience to say that a Porsche was and is WAAY better than a Corvette.

Based on what? Because he works for Porsche?

Being that the Corvette is the longest running sinlge car model in history - I would say that the Corvette enthusiasts the world over would disagree.

[T-Bird]

they use OHC engines in racing because you can have more valves and they are a little bit easier to tune but you guys are saying that pushrod engines suck and are heavier/larger engines which is far from the truth, how can something that has less Camshafts,chains/belts, valves, etc... weigh more?

they do have those world winning Porsche beating Pushrod running cars out on the tracks now-a-days but I forgot their names could you by chance enlighten me on it again...

Also how do we know that St. Anger has the authority to say that a Porsche is better than a Corvette? because he is biased since he is employed by Porsceh? Do we have proof that he has thrown a Z06 or C6 through it's paces against a Porsche himself?

[PaulGT2164]

i dont like to participate in arguments that are held by passionately biased people but oh well

OHC motors are easier to tune especially DOHC motors, and maintian then pushrob motors,

pushrod motors are still around cause the age old mantra "dont fix it if it isnt broke" pushrod motors still get the job done, so why change that

by simlpe logic a OHC motor will mostly be heavier than a pushrod motor, like T-Bird said

i dont think this is mentioned on here, but also the center of gravity on a pushrod motor is lower than that of a OHC motor, which is important in a race car, or a sports car

st-anger is passionately porsche biased, so of course he will say a porsche is better
rc45 is passionately vette biased, so he likes vettes
i personally like making high hp econo boxes, which rc45 hates
none of us are wrong, we are just biased and somewhat close minded

this is a pointless argument, no ones minds will be changed lol

each type of engine has its advantages
and on some days a ohc motor will win, some days a pushrod engine will, who cars

ohc or pushrod who cares, if it delivers it delivers
this remindes me of a forced induction vs NA argument i was once in....

[graywolf624]

Im still waiting on a correlation here.

You just admited that pushrods are generally smaller and lighter then regular engines.
You also admited that mpg is not correlated to liters of engine.

What do you have to fall back on now.. Still hp/liter has no meaning in the real world. It doesnt mean the engine will be lighter, it doesnt mean the engine will be more economical, it doesnt mean the engine revs higher, it doesnt mean the engine is smaller in size.

If you want the real deal pushrod versus ohc then there are advantages and disadvantages.

The push rod is cheaper to tune.
The dohc has a higher rev potential.
The pushrod is cheaper to produce
the dohc is less subject to energy loss through inertia(pistons).
These are all known things, but that still leads to a situation where the type depends on the usage.

[RC45]

Originally Posted by PaulGT2164 st-anger is passionately porsche biased, so of course he will say a porsche is better rc45 is passionately vette biased, so he likes vettes i personally like making high hp econo boxes, which rc45 hates none of us are wrong, we are just biased and somewhat close minded

Correct

Originally Posted by PaulGT2164 ohc or pushrod who cares, if it delivers it delivers this remindes me of a forced induction vs NA argument i was once in....

On RacignFlix?

[Guibo]

Originally Posted by fedezyl Well, just one question, why is it then, that most high performance car manufacturers use OHC instead of pushrods, as well as formula one and basically most racing engines?

Formula One, as the name implies, deals with racing that adheres to a strict code of regulations. They could have made it a free-for-all, but do you really want to see the effect of Can-Am era displacements combined with insufficient chassis development and track safety? Might as well ask why they banned driver's aids (traction control, ABS, active suspension, etc) back in the '90s. Because it makes a car worse? No, that does not follow.
And since the current formula calls for a 3-liter limit, the best way to maximize hp is through increased revs. And DOHC allows for outright breathing capabilities. No one is disputing that. What's in dispute is: how relevant is that to street car applications? Do you really want a 3-liter Formula One car engine for the road? It may sound like a sexy idea, but it'd be stupid, totally impractical. Just because most people want cars that are "high-tech" (despite the fact that Duesenbergs had DOHC in the '20s, as well as Renault even in the early 1900's) doesn't mean that that's the best way to go for all applications.
So DOHC works for Porsche, that's fine. So GM wants to use pushrods, more power to 'em. The point is, Porsche, with its 3.6-liter engine, really has no choice but to go with DOHC if it wants the breathing capability to wring out 380-ish hp, without going to forced induction. GM can already do that with its pushrod V8, all the while tacking on an additional 25-odd horses, with the engine still not stressed to its max. They're giving people the performance of a Porsche, but at a substantial savings. And for this...they should be slagged off? Remember, GM already had a DOHC for its Corvette, the ZR-1. The marketplace basically said "Thanks, but no thanks." So it was dropped. Totally different companies, totally different philosophies. It's sorta useless to say that one company should adopt the philosophy of another, particularly when things are going well enough.

[mindgam3]

Originally Posted by graywolf624 Im still waiting on a correlation here. You just admited that pushrods are generally smaller and lighter then regular engines. You also admited that mpg is not correlated to liters of engine. What do you have to fall back on now.. Still hp/liter has no meaning in the real world. It doesnt mean the engine will be lighter, it doesnt mean the engine will be more economical, it doesnt mean the engine revs higher, it doesnt mean the engine is smaller in size.

Waiting for a correlation between what?

You say I admitted that pushrod engines are gnerally smaller and lighter than regular engines like i disagreed with you. I didnt disagree with you, i misunderstood you in the first place and then I agreed with you.....

I didnt admit mpg is not correlated to liters of engine - i havent compared them.... They are however correlated, negatively. GENERALLY as displacement increase, mpg decreases.

HP/litre is useful as other members have said.
It is related to the efficiency of the engine as i've said many times - as in how much power you get out of the engine compared to the air/fuel mixture you put in. It takes revs into account because the figure you use for HP is when the engine is at maximum revs.

The 3 basic principles of engines:

:arrow: Mechanical efficiency - Basically, the less friction, the more HP

:arrow: Volumetric Efficiency - The more air/fuel mixture you can get into the combustion chamber, the more HP you will create. The maximum is the size of the combustion chamber (for an NA engine), but in practice this is very hard to accomplish

:arrow: Thermal Efficiency - This is how efficiently the engine burns fuel. It is calculated as a percentage of how much horsepower is produced compared to how much stored energy was in the fuel that was combusted in the engine.

These are the 3 main, basic principles you have to tak into consideration when building an engine. HP/litre shows us as a general figure a combination of these 3, and therefore an idea of how efficient an engine is.

Its by no means the only thing that can and should be used but is a good figure.

[graywolf624]

I didnt admit mpg is not correlated to liters of engine - i havent compared them.... They are however correlated, negatively. GENERALLY as displacement increase, mpg decreases.

bullshit. The corvette gets 28 mpg. I can show you many much smaller v6s that dont achieve that number. I can show you a ferrari 360 that gets worse gas mileage.

It is related to the efficiency of the engine as i've said many times - as in how much power you get out of the engine compared to the air/fuel mixture you put in. It takes revs into account because the figure you use for HP is when the engine is at maximum revs.

first off.. the figure you use for hp isnt when the engine is at maximum revs.. thats false.
That depends on the car.
2nd it doesnt deal with rpms in any way shape or form.. air/fuel is a function over time. as determined by rpm. Thus mpg in a hp/liter car still may be horrid and often is. Hp/liter has no effect on the real world. None.

Its by no means the only thing that can and should be used but is a good figure.

It useless. You just admited it means nothing and is correlated to nothing in the real world. ITs at best a purely academic point.. at worst its pure rice.

[graywolf624]

Lets put it this way.. Im joe schmoe. I don't bother to care to understand how an engine works beyond do a little work on it. Now you tell me any area that hp/liter will effect me. In fact.. you tell me any area that hp/liter is even correlated enough with something that will effect me. Youll find there is no consistant correlation with anything that would effect the engines performance or efficiency beyond the words you want to say. If we were looking at a single cycle it would, but when was last time you ran an engine for one cycle of the engine?

Your not getting more energy per liter of gas. Your not getting more power per pound of engine weight. Your not getting more power per space the engine takes up. So just tell me one benefit in the real world.. Your still skirting the issue.

[mindgam3]

Originally Posted by graywolf624 I didnt admit mpg is not correlated to liters of engine - i havent compared them.... They are however correlated, negatively. GENERALLY as displacement increase, mpg decreases. bullshit. The corvette gets 28 mpg. I can show you many much smaller v6s that dont achieve that number. I can show you a ferrari 360 that gets worse gas mileage. It is related to the efficiency of the engine as i've said many times - as in how much power you get out of the engine compared to the air/fuel mixture you put in. It takes revs into account because the figure you use for HP is when the engine is at maximum revs. first off.. the figure you use for hp isnt when the engine is at maximum revs.. thats false. That depends on the car. 2nd it doesnt deal with rpms in any way shape or form.. air/fuel is a function over time. as determined by rpm. Thus mpg in a hp/liter car still may be horrid and often is. Hp/liter has no effect on the real world. None. Its by no means the only thing that can and should be used but is a good figure. It useless. You just admited it means nothing and is correlated to nothing in the real world. ITs at best a purely academic point.. at worst its pure rice.

did i not write GENERALLY in big enough letters for you?? If you were to compare every single car on the market, GENERALLY the bigger the displacement, the lower the mpg....

RPM is a function over time, but you can take any point that an engine is spinning and say that it is rotating at a certain rpm. Just as you can say at any moment in time a car is traveeling at say 50mph - mph is still a measure over time.

HP = (torque x 2(pie) x RPM)/33000

We can say at one point in a particular engines cycle it is rotating at its maximum revs and we have a HP figure that is relative to this for that particular engine. What im saying is HP is calculated from amongst other things RPM. So if HP takes into RPM, so does HP/litre.

lol, when did i ever admit it means nothing, I jus explained how its related to the 3 basic fundamental principles of engine design..... how can that mean nothing??

You're never going to agree with me and i don't expect you to understand, but HP/litre is relative - by what amount is arguable but it is.

It may not be relative to Joe schmoe, but its relative to me and many others. You define the real world please. Why should the real world be joe schmoes world?

[mindgam3]

And you are getting MORE energy out per litre of gas if you have a higher hp/l figure. You put one litre of fuel in an F1 engine and you'll get more energy out than one litre of fuel that you put in your vette