New GM LS9 Supercharged Vette ZR1 engine
Moderators: The Dark Side of Will, Series8217
I still maintain that the DOHC high-revving nature is in fact an illusion. DOHC setups are generally used on engines that are inherently high-strung - low strokes and large bores, due to the abilitly of the valvetrain to reliably handle higher RPM's.
With a DOHC cylinder head and appropriate geometry on a high-stroke engine, I suggest that the result would be an even MORE flat torque curve due to better cylinder filling. I agree with Will, the largest differences between the two are cost and complexity.
Just look at Porsche's recent flat sixes...DOHC 3.6 liters with a torque curve that looks like this ________________
With a DOHC cylinder head and appropriate geometry on a high-stroke engine, I suggest that the result would be an even MORE flat torque curve due to better cylinder filling. I agree with Will, the largest differences between the two are cost and complexity.
Just look at Porsche's recent flat sixes...DOHC 3.6 liters with a torque curve that looks like this ________________
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Exactly. Please don't confuse camming/tuning with valvegear.Indy wrote:I still maintain that the DOHC high-revving nature is in fact an illusion. DOHC setups are generally used on engines that are inherently high-strung - low strokes and large bores, due to the abilitly of the valvetrain to reliably handle higher RPM's.
With a DOHC cylinder head and appropriate geometry on a high-stroke engine, I suggest that the result would be an even MORE flat torque curve due to better cylinder filling. I agree with Will, the largest differences between the two are cost and complexity.
Just look at Porsche's recent flat sixes...DOHC 3.6 liters with a torque curve that looks like this ________________
Look at Toyota's truck engines... DOHC V8's with power curves essentially the same shape as GM's pushrod truck engines.
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crzyone wrote:I would love to see an oversquare LSX with DOHC heads. Let is rev to 10-11000rpm. Thats what DOHC is meant for, not putting the heads on a conventional bottom end and not seing the gains that you could.
DOHC starts where pushrods end.
Except that emissions regulations level the playing field. I would freaking love for a Lotus Elise to have a 2 litre engine that made 350 HP N/A at 14,000 RPM, but even with the best variable cam phasing available, it would still be too dirty for the EPA to bless.
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At 14,000 RPM you have to consider where this air and fuel is going. Just because you're making 350 HP DOESN'T mean that your only putting in 350 horsies-worth of air and fuel.
A camshaft that's going to be able to support that kind of speed will have likely have a lot of overlap and other extreme features, a good portion of what's going in will never be burned...
A camshaft that's going to be able to support that kind of speed will have likely have a lot of overlap and other extreme features, a good portion of what's going in will never be burned...
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I know but what i said was 350hp worth will be burned, not consumed. But still.Indy wrote:At 14,000 RPM you have to consider where this air and fuel is going. Just because you're making 350 HP DOESN'T mean that your only putting in 350 horsies-worth of air and fuel.
A camshaft that's going to be able to support that kind of speed will have likely have a lot of overlap and other extreme features, a good portion of what's going in will never be burned...
I realy apreciated the level of engineering GM is doing on thier LS series engine, I think the torque curves is very good, and not typical of past sbc designs from gm.
car.
I don't think the EPA much cares about how clean the car is at WOT, at redline. Hell all of the high output foreign cars I've driven smoked pretty good (Diesel like), at WOT because the factory runs them on the rich side.
But with the cam profiles needed to sustain 14,000rpm, let alone make climbing power to those levels, the idle and part throttle, low RPM emissions are what takes a big hit. And as Will said, even with the new VVT and phasing, 500 lift is 500 lift, there's no getting around that. So the cams may do better than your SBC cams, but getting them to pass new car emissions is still a chore.
And after all that time and development, you're left with a motor that not many people will appreciate (Look at the S2000).
How do today's sportbikes pass emissions with their wild, high RPM engines? I don't think the EPA is the only reason for cars not having 14,000rpm engines. I think a lot of it is durability. Your 200hp/l sportbike engines aren't made to last 200,000 miles, half of that under warranty. They're made to last 20,000, if that. And change your oil all you want, 16,000rpm does not make for a long lasting engine at the technology we have, and can afford at the still mass-produced levels sportbikes are.
But with the cam profiles needed to sustain 14,000rpm, let alone make climbing power to those levels, the idle and part throttle, low RPM emissions are what takes a big hit. And as Will said, even with the new VVT and phasing, 500 lift is 500 lift, there's no getting around that. So the cams may do better than your SBC cams, but getting them to pass new car emissions is still a chore.
And after all that time and development, you're left with a motor that not many people will appreciate (Look at the S2000).
How do today's sportbikes pass emissions with their wild, high RPM engines? I don't think the EPA is the only reason for cars not having 14,000rpm engines. I think a lot of it is durability. Your 200hp/l sportbike engines aren't made to last 200,000 miles, half of that under warranty. They're made to last 20,000, if that. And change your oil all you want, 16,000rpm does not make for a long lasting engine at the technology we have, and can afford at the still mass-produced levels sportbikes are.
88GT 3.4 DOHC Turbo
Gooch wrote:Way to go douche. You are like a one-man, fiero-destroying machine.
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The S2K has a cult like following, much like the fiero. You won't see people trading in their camaros for one but they are a wicked car.Aaron wrote:
And after all that time and development, you're left with a motor that not many people will appreciate (Look at the S2000).
I find the cars with the highest rpm are the most fun to drive. 8k in my GTR is just wicked.
the v-tec system with dual cam lobes would be the easiest to maximize both fuel economy/emissions and high end power. the low end lobes can be ground to maximize the emissions during the rpm range that most daily commuting and highway cruising would be done at , and the second lobe could be ground to maximize potential power.
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Well... within its powerband, it will obviously have good cylinder sealing and a clean exhaust, it's only outside the powerband that it has problems with cylinder sealing and blowing mixture out the exhaust.Indy wrote:At 14,000 RPM you have to consider where this air and fuel is going. Just because you're making 350 HP DOESN'T mean that your only putting in 350 horsies-worth of air and fuel.
A camshaft that's going to be able to support that kind of speed will have likely have a lot of overlap and other extreme features, a good portion of what's going in will never be burned...
Direct injection can work miracles in this area, though... DI should be as much better for making a wild engine streetable as port injection is better than a carb.
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The EPA testing, I believe includes some WOT exercises, but I don't know the exact extent of that portion of the test, or how much it's weighted.Aaron wrote:I don't think the EPA much cares about how clean the car is at WOT, at redline. Hell all of the high output foreign cars I've driven smoked pretty good (Diesel like), at WOT because the factory runs them on the rich side.
But with the cam profiles needed to sustain 14,000rpm, let alone make climbing power to those levels, the idle and part throttle, low RPM emissions are what takes a big hit. And as Will said, even with the new VVT and phasing, 500 lift is 500 lift, there's no getting around that. So the cams may do better than your SBC cams, but getting them to pass new car emissions is still a chore.
And after all that time and development, you're left with a motor that not many people will appreciate (Look at the S2000).
How do today's sportbikes pass emissions with their wild, high RPM engines? I don't think the EPA is the only reason for cars not having 14,000rpm engines. I think a lot of it is durability. Your 200hp/l sportbike engines aren't made to last 200,000 miles, half of that under warranty. They're made to last 20,000, if that. And change your oil all you want, 16,000rpm does not make for a long lasting engine at the technology we have, and can afford at the still mass-produced levels sportbikes are.
Also, I don't think the EPA regulates motorcycles... YET. Ever seen a crotch rocket with a catalyst?
Also, if the EPA were to assign the same emissions standards to cars as to bikes, the bikes could still get away with some really radical engines, as pollutants are measured in mass emitted per vehicle mile... a 1.3 litre 'Busa would get the same allowance as a 7 litre 'Vette or 8 litre Viper.
actually most of the new sportbikes do have cats. haven't seen any harleys with em though.The Dark Side of Will wrote:Also, I don't think the EPA regulates motorcycles... YET. Ever seen a crotch rocket with a catalyst?
Also, if the EPA were to assign the same emissions standards to cars as to bikes, the bikes could still get away with some really radical engines, as pollutants are measured in mass emitted per vehicle mile... a 1.3 litre 'Busa would get the same allowance as a 7 litre 'Vette or 8 litre Viper.
here is a pic of where one guy cut the honeycomb out of his 2005 636 header.
http://www.kawasakiforums.com/upfiles/2 ... 829CD9.jpg
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MY GOD look at that power curve. I want one.
Amazing what RPM can do, the 3.4l DOHC actually makes just about the same amount of peak torque stock, but that NSX motor simply destroys the 3.4. A stock 3.4l DOHC for comparison. The graphs actually look very similar--until 5,000rpm. Even cammed to hell, the NSX still has a better torque curve. I love it. The NSX is down on displacement some, but its compression is probably much higher than the 9.25 of the 3.4.
By the way, is the NSX motor aluminum block?
I have sudden, and very strong, inclination to build a GM 3.6l DOHC. And build as in like $10,000 build. Full ITB setup (I got those laying around...), equal length headers, 12:1 compression, cam it to high heaven, titanium rods, lightweight valvetrain, the works. A nice 400hp 9,000rpm beast would be a fucking blast. Throw it into a nice custom made tube frame car, maybe 1500lbs worth, and go have some fun in the single digits.
Amazing what RPM can do, the 3.4l DOHC actually makes just about the same amount of peak torque stock, but that NSX motor simply destroys the 3.4. A stock 3.4l DOHC for comparison. The graphs actually look very similar--until 5,000rpm. Even cammed to hell, the NSX still has a better torque curve. I love it. The NSX is down on displacement some, but its compression is probably much higher than the 9.25 of the 3.4.
By the way, is the NSX motor aluminum block?
I have sudden, and very strong, inclination to build a GM 3.6l DOHC. And build as in like $10,000 build. Full ITB setup (I got those laying around...), equal length headers, 12:1 compression, cam it to high heaven, titanium rods, lightweight valvetrain, the works. A nice 400hp 9,000rpm beast would be a fucking blast. Throw it into a nice custom made tube frame car, maybe 1500lbs worth, and go have some fun in the single digits.
88GT 3.4 DOHC Turbo
Gooch wrote:Way to go douche. You are like a one-man, fiero-destroying machine.
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