Enthusiast
There are many things to compare...Originally Posted by fpv_gtho
milage, torque curve, redline, peak HP, thermal efficeincy (rated in lbs/hp/hr or kg/kWh)
Also a neat fact the S2000 engine actually makes more power when you kill the VTEC system... loses low rpm hp and gets even peakier but has a higher peak hp.
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Fanatic
A car with 657nm is gonna be easier to drive around town than one with 220nm
Faster, faster, faster, until the thrill of speed overcomes the fear of death...
– Hunter Thompson
Enthusiast
Actually you wouldn't know anything about how well they drive around town until you know the weight of the car the gearing and the shape of the torque curves and the peak hp...
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Fanatic
Let's see, Wouter said he'd prefer an LS7-powered car (where I got 657nm from), so that's only a Z06 at the moment. Check out the Top Gear ep where Clarkson drives that. He moves off in 5th no problems at all with very little revs. That basically means around town you could chuck it in say 3rd and just leave it there. No shifting up and down all the time as you'd need to in an S2000, (220nm) which every review I've read says you need to.
Faster, faster, faster, until the thrill of speed overcomes the fear of death...
– Hunter Thompson
Enthusiast
60 degrees ... tell me when the hell do you ever need to phase the camshaft 60 degrees
as for valvetronic, you forgot to mention that its only acting on the intake vales, as it's primary purpose is to control the amount of air being let into the engine and gives no benefit to the exhaust side which on a vtec engine does change the cam profile to allow quicker evacuation of exhaust gasses.
taken from the autozine technical school website
"Now you might think about Honda's VTEC. Can Valvetronic use its variable lift to increase power like VTEC ? Sadly, Valvetronic is actually less efficient at high rev than conventional engines, let alone VTEC. As you can see, the camshaft drives the long intermediate rocker arms, in turn drive finger followers, this generates quite a lot of friction. Therefore the efficiency and refinement of Valvetronic engines drop rapidly at over 6,000 rpm. No wonder in the foreseeing future BMW will not equip its M-power engines with Valvetronic."
and i trust this dude alot more then i trust you, n believe me, 99% of this forum feels the same way as me
Enthusiast
friction losses when as rpm goes up, alot more then conventional systems, you can use low friction linings and what not but that doesnt change the fact it has an inherent flaw in the system
Enthusiast
Does the S2000 have a super heavy clutch? No... Is it prone to stalling? No... When cruising at 60mph in 5th will you be topping 5-6000rpm.. Yes.
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Enthusiast
60 degrees total (so +/- 30) and that is pretty much as far as you want to go.
That is because the valvetronic system is still very young and because the standard lift is good on it's own and only needs the timing change of the VANOS system to be effective.
Yeah I read that too and I can tell you two things 1: that is old info Valvetronic can already run at a sustained 7200rpm in cars that BMW makes now and 2: whoever wrote that article missed something because the whole point of valvetronic is to increase milage AND power. Also he doesn't give any sort of data at all to show the increased "friction" and that it is worse than a normal static lift system. It looks like he heard that valvetronic doesn't work over 6000rpm and guessed that it was mostly because of friction from the pictures. In reality it has to do with many things like the added inertia of the (as of yet) large parts, the fact that the original leverage arms and force angles were not optimum (most of the 1200rpm increase came from changing these) and also the fact that higher rpms require stronger valve springs which put too much stress on the system. Friction is actually quite low in the Valvetronic system (everything is on ballbearings and rollers). Now as I said before this system is still young and as it changes will soon be able to sustain 9000rpm operation and it will be used on both intake and exhaust sides.
I don't want you to just trust me I want you to read what I write and make your own descision. If you think there is a hole in my explanations then discuss it. You have shown in other threads that you are capable of maintaining a good discussion even with me.
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Enthusiast
MY post went completely over your head... (and btw I would like to know what 4 cylinders you were talking about)
IF and only IF the 3L block MUST have the exact ratio of displacement to siez as the 2L, then it would be bigger.
Im talking about STREET CARS, there is no displacement classes on the street. And your looking at just small numbers again, chances are the 4L engine is going to have a much better powerband(and probably better acceleratoin because of it), and be under a lot less strain.
I never said ultimate power is the only thing that matters, obveously thats wrong. For starters were talking about performance cars, so drop the whole "dodge lineup" argument, most of those are are family commuter cars and arnt after power. Manufacturers use whats available and cost efficient for the car.
I rather pay LESS money for a MORE powerful V8 (compared to the puny 240hp F20C) thats hardly larger or heavier(and has much more potential). hp/l is not "technology", hp/WEIGHT and SIZE are, because that actually matters in the REAL WORLD.
I cant even imagine what you were thinking when you wrote:
"as opposed to a small engine which costs just a bit more and has had hundreds of engineers work on it"
You are implying that the V8 in this matter hasnt had hundreds of engineers working on it, which is a (bad) assumption. Its not always about extracting the most amount of power from the engine at hand, but the right amount of power for that car.
Enthusiast
No, what he said was correct, it was a quote from Carroll Shelby. Your car accelerates on your torque curve exactly, if your making 300ft.lbs at 2000RPMs and 300ft.lbs at 4000RPMs you will be making double the hp, but wont be pulling any harder in the same gear.
Peak hp is irrelivent in many cases, lets take the infamous "dyno queen" Supras for example. They are known as dyno queens because they make OMG 1000hp!$!@@#$@#, but end up only being able to run 11s or so in the 1/4 mile. Why? Because they are only making that 1000hp for like 200RPMs, the torque curve looks like: ______^
Fanatic
Does a heavy clutch worry me? No, I drive a truck at work. I like a heavy clutch, it's easier to modulate. And if you don't have to change gear all the time because it's got lots of torque, it's not going to matter that muchStalling is not the cars fault, it's your fault for not knowing how to drive the car properly and stalling.
And that's a good thing? You could stick a Z06 in 6th at 100kmh and be only turning over at ~1500rpm, and have adeqaute grunt to move off.
Faster, faster, faster, until the thrill of speed overcomes the fear of death...
– Hunter Thompson
Enthusiast
it does have 6 gears ...
Enthusiast
the vanos might have the highest range at 60 degrees but since the gains from merely phasing the camshaft are so small, that those extra 10 or so degrees (i have no clue what other systems are capable of but i assume it's in the 40-50 degree range) wont make much of a difference
as for the valvetronic, that is pretty much the only info ive had other then bmw press shit but claims from manufacturers are often heavily inflated.
if the system hasnt changed it still seems like the valvetronic system is less "direct then that used in regular heads, tho it is a clever system i admit, there are to me better ones out there, like ferrari's 3d profile camshafts. the valvetronic however can benefit from nearly infinite cam lift profiles as it's controlled by an electric motor which is probably controlled by the ECU where as the ferrari's is still dictated by the camshaft itself
if they have been able to refine the system to the specs you provided then yes i would have to admit that you're right bout this one, and bmw's would be better, maybe my innate hatred of bmws that has taken over me or something
tho there are systems out there which are better then vtec, vtec was still the first (or one of the first w/e) to be put in mass production cars and started the whole trend, and has remained one of the best and most affordable systems out there till even now, which is why i think it deserves some respect and less knocking, even with the insane fanboys with their lil civics who's vtecs are geared for economy and not performance ..
Enthusiast
you forget that torque is changed by gear ratios, just because a car has 500ft-lbs of torque doesnt neccesarily mean it will accelerate faster, gear ratios can easily mask the peakyness of an engine, and ultimately power is what matters at the top end, there are hundreds of variables to take into account, but you're right a fatter torque curve IS better then a tiny one, but also take this into consideration
let's say we have an engine which has a rather fat torque curve and let's arbitrarly set the redline rpm to 7000, if you shorten the stroke and widen the bore, the engine will make less low rpm torque but alot more high rpm power, now you can use the gear ratios to make up for the lower torque at the low end, but extra power you get at the top end will more then make up for that
this isnt going to be true in all cases and ultimately you will run into a barrier you just cant pass
you're also right about the fact that cars arnt ranked on a displacement scale in real life, but most cars in the same class do have similarly sized engines, you're not going to find an 8L engined car in a class of economobiles for example
ive completely lost track of what i wanted to say so i'm jsut gonna stop now and make another post later that's more on topic
Enthusiast
one last thing, a really fat torque curve isnt always a good thing, say ur torque curve is really fat and lasts 6000rpm, you only stay in each gear for 2 or 3000 rpm so in essence you're wasting another 3-4 thousand rpm, but say you destroked the engine and bored it out, your torque curve is smaller but your gear ratios match it alot better, you'd also have more power and be able to go just as fast so long as you remain in the right gear
i'm not saying this is the best thing to do, since you dont always wanna shift when in everyday traffic, but when you're buying a $30,000+ sports car ... is performance in traffic the most important quality to u ??
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