LS7 - What happened to 3 valves per cylinder?
02-24-2005, 09:27 PM
#21
Originally Posted by Anonymous
There are advantages and disadvantages to both two and four valve engines.
A book could be written about it.
Now I believe the 3 valve design was never intended for the LS series engine at all. I read a lot of hype about it in here but never saw proof.
The only 3 valve GM cylinder head I ever saw was in Chevy High Performance in the News section. But if you looked closely it was a new generation Big Block head. The magazine never said it was an LS series head either.
I think that is where the rumor got started.
A book could be written about it.
Now I believe the 3 valve design was never intended for the LS series engine at all. I read a lot of hype about it in here but never saw proof.
The only 3 valve GM cylinder head I ever saw was in Chevy High Performance in the News section. But if you looked closely it was a new generation Big Block head. The magazine never said it was an LS series head either.
I think that is where the rumor got started.
The 3 valve head was in an SAE News article (.pdf).
Further into the news was an article about the Electromagnetic Valves Lotus Engineering, and a couple of manufacturers, were working on. I think it was Saab or Volvo that were said to introduce them first??
Huge news - no cam!! No carb.... -> no distributor......-> no cam.
It's the future.....
.. 
02-25-2005, 07:29 AM
#22
this sounds familier to another thread on here more valves equals more flow potentcial and that meens you can get more stuff in and thus more power out! this is why bike manufactures are now moving to 5 valves per cylinder like Audi have with there engines. as said in another thread on here, if GM did go with a 3,4 or 5 valve heads it would requier a major restyle or shoving the engine way back and none are going to happen any time soon. it would be nice to see someone at GM try and have a go anyway, if only to see how viable it is. they have the tech and the undestanding as the last 2 inline 4s they have built (the XE and the newer Ecotec) have been amazing. also the current 3.0 ltr V6 is an enduracne race winner not to mention a VERY good road engine.
i think most peoples problem with multi vlave heads is they have little exsperince with them and with this people get a little scared. they are much more common over here in Europe and the culture is very much that you NEED to have 4 valves or there is somthing wrong with it! even diesels over here now have 4 valves per cylinder! i think given time people will come around to see the advantages that it offers (and unfortuntaly the dissadvantages as well). and for people interested in tuning there are sum advantages, like you dont need to buy new heads to make big power, just get a shop to "work" with them. also they let you adjust the timing of inlet and exhaust indapendently of each other. this allows more fine tunning and in the end more power. just take a look at a Honda Vtec and imagin a 7ltr V8 version. sound good to me!!!!
Thanks Chris.
more valves equals more flow potentcial and that meens you can get more stuff in and thus more power out! this is why bike manufactures are now moving to 5 valves per cylinder like Audi have with there engines. as said in another thread on here, if GM did go with a 3,4 or 5 valve heads it would requier a major restyle or shoving the engine way back and none are going to happen any time soon. it would be nice to see someone at GM try and have a go anyway, if only to see how viable it is. they have the tech and the undestanding as the last 2 inline 4s they have built (the XE and the newer Ecotec) have been amazing. also the current 3.0 ltr V6 is an enduracne race winner not to mention a VERY good road engine. i think most peoples problem with multi vlave heads is they have little exsperince with them and with this people get a little scared. they are much more common over here in Europe and the culture is very much that you NEED to have 4 valves or there is somthing wrong with it! even diesels over here now have 4 valves per cylinder! i think given time people will come around to see the advantages that it offers (and unfortuntaly the dissadvantages as well). and for people interested in tuning there are sum advantages, like you dont need to buy new heads to make big power, just get a shop to "work" with them. also they let you adjust the timing of inlet and exhaust indapendently of each other. this allows more fine tunning and in the end more power. just take a look at a Honda Vtec and imagin a 7ltr V8 version. sound good to me!!!!
Thanks Chris.
02-25-2005, 05:12 PM
#23
TECH Enthusiast
The bottom end of a Honda V8 wouldn't be that different from an LS1 or LS2. Feature by feature, the Honda 3.5L V6 has a lot in common with the LS2 already.
If you want to see what a 32V Small Block Chevy would do, look at the LT1 Arao ($6000)
heads. They're a pushrod design with ridiculous flow numbers and put down ridiculous horsepower. I find it very unlikely that a VTEC would be much better than that.
Some like to think that GM doesn't go 4V/Cylinder & DOHC because they can't. The reality is that the top end of a Honda is VERY expensive. Anyone take a look at the price of a VTEC Civic lately?
If you want to see what a 32V Small Block Chevy would do, look at the LT1 Arao ($6000)
heads. They're a pushrod design with ridiculous flow numbers and put down ridiculous horsepower. I find it very unlikely that a VTEC would be much better than that.Some like to think that GM doesn't go 4V/Cylinder & DOHC because they can't. The reality is that the top end of a Honda is VERY expensive. Anyone take a look at the price of a VTEC Civic lately?
02-25-2005, 09:07 PM
#24
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Originally Posted by LTSpeed
Some like to think that GM doesn't go 4V/Cylinder & DOHC because they can't. The reality is that the top end of a Honda is VERY expensive. Anyone take a look at the price of a VTEC Civic lately?
02-26-2005, 12:09 PM
#25
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Even with the 'vette money is a big issue. A lot of people seem to think they're GM's ultimate vehicle. They are not building a McClaren F1 where cost is no factor. While a Z06 is expensive, it's price is kept way below other supercars by sharing parts with other vehicles. Profit on the corvette offsets losses on a large number of low margin vehicles--just like in most big car companies.
No one doubts they can build a 4V engine. And there's nothing stopping them from V10's or V12's either. But if they were doing these sorts of things, I doubt the car would end up in a price range where average folks like us would even be here discussing them.
No one doubts they can build a 4V engine. And there's nothing stopping them from V10's or V12's either. But if they were doing these sorts of things, I doubt the car would end up in a price range where average folks like us would even be here discussing them.
02-26-2005, 03:01 PM
#26
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Fwiw gm can do over head cam setup, just look at the trailblazer. 4.2l 275hp and this motor has been out for a while now, and is also a truck motor. I'm sure it could make even more if it were tuned for performance.
02-26-2005, 05:52 PM
#27
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Exactly. They just need to do it once. Then just transfer the technology and most of the parts from platform to platform. Then the cost gets spread out over more vehicles and they make a better product. Not that I think GM really gives a crap about making a better product. Heck...with how ugly these new crap-boxes are, I don't think they give a crap at all about what people want. "Just make a bunch of vehicles that look a little different, stick a GM symbol on 'em, and toss 'em out the door.", that should be their new motto.
02-26-2005, 06:10 PM
#28
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What was the advantage of multi valves?
It wasn't always flow, because the smaller valves have problems with
friction on the air, two valves that have diameter of 1" do not flow the same
as a 2" valve, its just like exhaust systems.
One of the advantages was the smaller ports providing the same flow would
allow for high velocities. Means the TQ curve SHOULD stretch further.
Other advantage was dual smaller valves have a light weight, means they should not float or take a very high rpm to float.
OHC had advantage of less valvetrain mass. Had advantage of cam phasing trix like VTEC which will allow you to simulate different cam profiles at different rpm...
OHC has huge disadvantage in increased complexity, packaging space that
couldve been used for cubic inches used for valve train.
Example, the 5.4L ford can prolly go to 5.7L. This thing has physical
dimensions larger than that of a LS1 and competing with that of a big block. The LS1 in comparison can go to about 7.3L...
The valve train tricks that might get you another 5% in power couldve been used for cubic inches instead.
The 3 valve looked to me that it wouldnt support high rpm, too much chit to work on, too much chit to break.
The packaging on the new LS7 head can support 420 or so CFM, so with
as long as the heads can support the meat to be ported out that far, you will
have way more head than you need, unless you need 1000 or more HP N/A.
If this head can get to the 420CFM, I'm talking about this is good for 900 or more HP all N/A....
GM was smart for TI on the intake side only, exhaust valve is smaller and light by nature. These valves can prolly support 9000 RPM all by themself.
It wasn't always flow, because the smaller valves have problems with
friction on the air, two valves that have diameter of 1" do not flow the same
as a 2" valve, its just like exhaust systems.
One of the advantages was the smaller ports providing the same flow would
allow for high velocities. Means the TQ curve SHOULD stretch further.
Other advantage was dual smaller valves have a light weight, means they should not float or take a very high rpm to float.
OHC had advantage of less valvetrain mass. Had advantage of cam phasing trix like VTEC which will allow you to simulate different cam profiles at different rpm...
OHC has huge disadvantage in increased complexity, packaging space that
couldve been used for cubic inches used for valve train.
Example, the 5.4L ford can prolly go to 5.7L. This thing has physical
dimensions larger than that of a LS1 and competing with that of a big block. The LS1 in comparison can go to about 7.3L...
The valve train tricks that might get you another 5% in power couldve been used for cubic inches instead.
The 3 valve looked to me that it wouldnt support high rpm, too much chit to work on, too much chit to break.
The packaging on the new LS7 head can support 420 or so CFM, so with
as long as the heads can support the meat to be ported out that far, you will
have way more head than you need, unless you need 1000 or more HP N/A.
If this head can get to the 420CFM, I'm talking about this is good for 900 or more HP all N/A....
GM was smart for TI on the intake side only, exhaust valve is smaller and light by nature. These valves can prolly support 9000 RPM all by themself.
02-26-2005, 08:45 PM
#29
TECH Enthusiast
GM already has OHC know-how. They don't need to develop something.
One other disadvantage of OHC setups is the height of the engine and size of the heads. This is a very serious real-world constraint and has been a packaging problem for years. It's one of the major reasons OHC engines keep moving further back up under the windshield in newer cars. (Trucks usually don't have that problem). It's hard to get a decent aero shape with a massive tall hunk of metal way out front.
The reason a '03 and newer Accord has lower power than an Odyssey, though they basically have the same engine, is that the Accord doesn't have the space above the engine to put in an efficient intake. The Odyssey (and new Ridgeline) have huge intakes.
One other disadvantage of OHC setups is the height of the engine and size of the heads. This is a very serious real-world constraint and has been a packaging problem for years. It's one of the major reasons OHC engines keep moving further back up under the windshield in newer cars. (Trucks usually don't have that problem). It's hard to get a decent aero shape with a massive tall hunk of metal way out front.
The reason a '03 and newer Accord has lower power than an Odyssey, though they basically have the same engine, is that the Accord doesn't have the space above the engine to put in an efficient intake. The Odyssey (and new Ridgeline) have huge intakes.
02-26-2005, 09:31 PM
#30
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Originally Posted by LTSpeed
GM already has OHC know-how. They don't need to develop something.
One other disadvantage of OHC setups is the height of the engine and size of the heads. This is a very serious real-world constraint and has been a packaging problem for years. It's one of the major reasons OHC engines keep moving further back up under the windshield in newer cars. (Trucks usually don't have that problem). It's hard to get a decent aero shape with a massive tall hunk of metal way out front.
The reason a '03 and newer Accord has lower power than an Odyssey, though they basically have the same engine, is that the Accord doesn't have the space above the engine to put in an efficient intake. The Odyssey (and new Ridgeline) have huge intakes.
One other disadvantage of OHC setups is the height of the engine and size of the heads. This is a very serious real-world constraint and has been a packaging problem for years. It's one of the major reasons OHC engines keep moving further back up under the windshield in newer cars. (Trucks usually don't have that problem). It's hard to get a decent aero shape with a massive tall hunk of metal way out front.
The reason a '03 and newer Accord has lower power than an Odyssey, though they basically have the same engine, is that the Accord doesn't have the space above the engine to put in an efficient intake. The Odyssey (and new Ridgeline) have huge intakes.
True OHC engines all taller than OHV engines. FYI the Odyssey and Ridgeline are 3.5L and the Accord is a 3.0L. For peak power there is nothing better than a 4 valve head.
Example on a 2.0L
Thats on a T3 (61MM) not a T4 and the turbo isn't even maxed out yet. The is head stock Honda casting
which isn't even ported. It is using aftermarket springs, retainers, and keepers so it can rev past 8K. Cams are stock Honda cams. 
02-26-2005, 10:09 PM
#32
Originally Posted by TightSS
who can drive at 8000 rpm on the street?
There is nothing wrong with revs. And yes, there is a displacement vs OHC trade off in packaging.
But 4-valves breath better because there is more CURTAIN area. While a 2" valve will have the same curtain area as 2 1" valves, the reality is the trade off is between 1 2" valve and 2 1.3" valves. That is 30% more curtain area.
And OHC designs mean no pushrods are in the way of the ports...so better flow is nearly always the case.
DOHC allows variable valve timing, which can broaden the torque range and eliminate EGR.
Most OHC have lower valvetrain mass. Direct-action DOHC (I guess you could also have a direct action flat-head) has a lot less mass. And virtually all race engines are direct action DOHC. Not every street DOHC is direct action since that recludes hydraulic lifters.
David
02-26-2005, 10:12 PM
#33
Chevy tried multivalves with the ZR1. I had one, it was great. But the LS is definitely holding down cost. My 91 ZR1 listed at $65,000. The new LS7 car is $75K...15 years later!!! and faster. That really says it all. Chevy HAS been there, and wisely decided it wasn't worth the money. We all voted with dollars. The ZR1 never really caught on ...too much more money!
02-26-2005, 10:25 PM
#34
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Originally Posted by TightSS
Chevy tried multivalves with the ZR1. I had one, it was great. But the LS is definitely holding down cost. My 91 ZR1 listed at $65,000. The new LS7 car is $75K...15 years later!!! and faster. That really says it all. Chevy HAS been there, and wisely decided it wasn't worth the money. We all voted with dollars. The ZR1 never really caught on ...too much more money!
That LT5 was NOT produced by Chevy, talk to Lotus on that one hence the cost.
The 8K is what that engine spins stock so that wouldn't be a problem. Now when putting FI or some bigger cams then it would need to rev higher to take advantage of it thats why the better valvetrain is needed.The stock bottom end can rev easily to 8500-9000.
02-26-2005, 11:14 PM
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Originally Posted by DavidNJ
Don't even go that far. Go to TEA's site and look at their numbers for the Mustang 4v head.
I don't know what you are getting at.
A link would be very usefull.
02-27-2005, 12:13 AM
#38
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Originally Posted by DavidNJ
Anyone who has an S2000 (including me, all the time, that think lacks LS1 grunt!), BMW M3s (and new M5s), many Ferraris, Mazda RXs (most of which need to be rev'd to get anything out of them), Toyota VVT-i TCs in Celicas, Elises, etc...
02-27-2005, 12:16 AM
#39
Originally Posted by regorih is gay =)
I don't know what you are getting at.
A link would be very usefull.
A link would be very usefull.
