If OHC is so great then why.....

[dailydriver]

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Originally posted by Last_Z:

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Originally posted by windnsea00:

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Originally posted by greenjp:

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Originally posted by windnsea00:
... Just saying, "My LS2 6-spd gets 28mpg on the freeway" doesn't mean it is a more efficent motor in making power which I think a lot of people tend to confuse...

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I really need some help here. What efficiency, other than fuel efficiency, is relevant?

jeff

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Well for example an LS2 getting 28mpg is capable of doing so because of its low torque curve and high gear ratios. It's chugging along at 2k or less rpms. Wind that up to 3k-4k rpms and it will in no way be able to keep up in fuel mileage to a DOHC engine. Also 6.0 liters for 400hp while commonly a European brand can do that with a 4 to 5 liter engine that is DOHC. I know there is more technical info that I'm missing that hopefully someone can chime in. Generally speaking, a DOHC engine is more efficent at making energy per gallon of fuel to a pushrod design. That's why most of the world uses that setup.

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Although you are not wrong, the way you are explaining things are a bit misleading. Yes the LS1 will consume more fuel at 3-4k RPMs, but the fact is it doesn't need to be there for highway use. DOHC engines do need such RPMs because their peak torque is quite higher than OHV engines. It's an inherent OHC flaw

Yes, the European engines do produce more power from less, but I think this is due to different engine design doctrines. Americans prefer not to stress the engines, therefore going bigger. Europeans and Japanese designs do produce more HP/lt, but at the price of reliability and/or low end torque. A good example is the BMW 3.0 making 333HP (M-3)....how many owners have blown their engines?! That's 110HP/lt!
Lastly, my LS1 made 300HP and 315lb/ft of torque to the rear wheels. That's about 345/360 respectively to the flywheel....on a basically stock engine. Full exhaust and a cam swap puts these engines at over 400HP without breaking a sweat. Not bad for a 60 year old design. The fact is both engine types have their use and applications.

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BTW; we need you over on the other GM/domestic basher threads.

 

[Matt89]

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Originally posted by G-Man II:
Yeah, I should have equaled the rpms.

My point is that all things being equal, a pushrod engine is not going to produce more torque than a OHC design just because it's a pushrod engine.

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Concur

 

[windnsea00]

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Yes, the European engines do produce more power from less, but I think this is due to different engine design doctrines. Americans prefer not to stress the engines, therefore going bigger. Europeans and Japanese designs do produce more HP/lt, but at the price of reliability and/or low end torque. A good example is the BMW 3.0 making 333HP (M-3)....how many owners have blown their engines?! That's 110HP/lt!
Lastly, my LS1 made 300HP and 315lb/ft of torque to the rear wheels. That's about 345/360 respectively to the flywheel....on a basically stock engine. Full exhaust and a cam swap puts these engines at over 400HP without breaking a sweat. Not bad for a 60 year old design. The fact is both engine types have their use and applications. [/QB]

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Price of reliability? BMW motors are known to be some of the most durable motors in the world not to mention toyota and honda. The early S54 engines in the E46 M3 had bearing issues due to the supplier for the bearing material I believe at that point of time. They weren't blowing due to being a high revving engine. BMW replaced the motors in the early E46 M3's and extended the warranty and the issue went away. It would be pretty pathetic if they built a motor for the world to buy that couldn't take a good beating (especially a Motorsport engine at that) Back in the 80's Motorsport were able to get over 1,000hp out of a 1.5 liter turbo 4 cylinder for one of their race cars

 

[G-MAN]

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Originally posted by Last_Z:
Lastly, my LS1 made 300HP and 315lb/ft of torque to the rear wheels. That's about 345/360 respectively to the flywheel....on a basically stock engine. Full exhaust and a cam swap puts these engines at over 400HP without breaking a sweat. Not bad for a 60 year old design.

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Where do you get it that the LS1 is a 60-year-old design? It may be a pushrod engine, but the LS1 is a thoroughly modern design that shares nothing in common with the original small block Chevy engine.

As for OHC designs, this is far from "modern technology." Duesenberg was building supercharged DOHC straight eights at their Indiana factory in the late 20s and early 30s for their SJ models.

 

[427Z06]

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Originally posted by windnsea00:
The early S54 engines in the E46 M3 had bearing issues due to the supplier for the bearing material I believe at that point of time.

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Fact is all major american manufacturers use suppliers for about %90 of the vehicles content. Not fair to only give BMW a pass on this.

 

[brianl703]

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Woe be the owner that has a $.10 o-ring fail or actuator clip break only to find out the entire lower intake has to be replaced to the tune of around $300.

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??? The only part of the 2.5L lower intake that ever breaks in my experience (and it only broke because I took it apart) is the plastic o-ring that the the rod which connects the two shutter assemblies together fits into (and which allows the rod to pull on the shutter assembly to open and close it).

Those plastic o-rings are available separately from the dealer. I think I paid about a buck a piece for them.

I think the problem might be that many dealers might not have a competent parts guy that knows how to look these parts up instead of saying, "Duh, I can't find it. How about a new lower intake for only $300?".

 

[Gurkha]

I see lots of opinions on how European and Japanese design tend to stress their engines,said and done,having owned all,US Euro and Japanese,none of the Japanese or even Euro engines I owned suffered from the so called engine design stree,OTOH,quite a few US big blocks I owned did give me nagging engine troubles,not outright block failure but oil consumption and compression loss at an early stage was few of the problems I encountered with them,the fact my highly stressed Honda Accord V6 fitted with HRC kits and raced occasionally still survives at 562000 miles is a testimonial ot how proper engine design,pushrod or OHC can go a long way.

 

[windnsea00]

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Originally posted by 427Z06:

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Originally posted by windnsea00:
The early S54 engines in the E46 M3 had bearing issues due to the supplier for the bearing material I believe at that point of time.

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Fact is all major american manufacturers use suppliers for about %90 of the vehicles content. Not fair to only give BMW a pass on this.

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Oh I def. don't give them a pass on this, it was disappointing. On the other hand they took care of the issue quickly by supplying new engines and extended warranties rather than wait it out. I was mainly trying to say though that the engines weren't blowing because of being stressed with 333hp out of 3.2 liters but because of the early build quality issue. BTW, the new MZ4 roadster/coupe are using this engine so it's still alive.

 

[road_rascal]

brianl703- the actuator clips are available (depending on how knowledgable the parts guy is), but the small o-rings/ seals where the shaft exits the manifold to the actuator are not. My 1996 went through 3 intakes due to bad o-rings (covered under warranty). The actuators and diaphragms are also pretty pricey and have their fair share of failures.
Hang out on the automotiveforums.com Windstar board and you'll see the IMRC haters

...

 

[brianl703]

Never heard of any problems with the one on the 2.5L other than that the actuator sometimes fails. So far mine hasn't in 133,000 miles. I did remove the plastic cover over the actuator box and found out later that might help the actuator last longer by keeping it cooler. I just don't like stupid, useless plastic covers covering the engine.

The 2.0L SOHC used in the Escort has a similar setup called "Split Port", never heard of any failures with that either.

 

[ebaker]

The OHC engine is able to open the valves much quicker than a pushrod motor. You can get the same high RPM Air flow/horsepower in an OHC engine with much shorter valve overlap. The shorter valve overlap/duration gives IMPROVED low end power, better mileage and lower emissions. A 4 valve engine can have even less valve overlap. Another way of looking at it is that in an OHC 4 valve engine the valves spend more time closed resulting in improved efficiency.
I think the perception that pushrod engines have more torque comes from the fact that they are generally larger piston displacement.

 

[Last_Z]

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Originally posted by G-Man II:

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Originally posted by Last_Z:
Lastly, my LS1 made 300HP and 315lb/ft of torque to the rear wheels. That's about 345/360 respectively to the flywheel....on a basically stock engine. Full exhaust and a cam swap puts these engines at over 400HP without breaking a sweat. Not bad for a 60 year old design.

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Where do you get it that the LS1 is a 60-year-old design? It may be a pushrod engine, but the LS1 is a thoroughly modern design that shares nothing in common with the original small block Chevy engine.

As for OHC designs, this is far from "modern technology." Duesenberg was building supercharged DOHC straight eights at their Indiana factory in the late 20s and early 30s for their SJ models.

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Not the LS1, but the small block Chevy. Yes, the LS1 is "different" from the traditional small block Chevy, but really how much? Except for a few dimensions here and there, the basic architecture is the same.

 

[Last_Z]

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Originally posted by windnsea00:

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Yes, the European engines do produce more power from less, but I think this is due to different engine design doctrines. Americans prefer not to stress the engines, therefore going bigger. Europeans and Japanese designs do produce more HP/lt, but at the price of reliability and/or low end torque. A good example is the BMW 3.0 making 333HP (M-3)....how many owners have blown their engines?! That's 110HP/lt!
Lastly, my LS1 made 300HP and 315lb/ft of torque to the rear wheels. That's about 345/360 respectively to the flywheel....on a basically stock engine. Full exhaust and a cam swap puts these engines at over 400HP without breaking a sweat. Not bad for a 60 year old design. The fact is both engine types have their use and applications.

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Back in the 80's Motorsport were able to get over 1,000hp out of a 1.5 liter turbo 4 cylinder for one of their race cars

[/QB]

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Hmmmm....a piece of junk, "push rod" Top Fuel engine makes over 7000 horsepower.

 

[windnsea00]

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Originally posted by Last_Z:

quote:

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Originally posted by windnsea00:

quote:

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Yes, the European engines do produce more power from less, but I think this is due to different engine design doctrines. Americans prefer not to stress the engines, therefore going bigger. Europeans and Japanese designs do produce more HP/lt, but at the price of reliability and/or low end torque. A good example is the BMW 3.0 making 333HP (M-3)....how many owners have blown their engines?! That's 110HP/lt!
Lastly, my LS1 made 300HP and 315lb/ft of torque to the rear wheels. That's about 345/360 respectively to the flywheel....on a basically stock engine. Full exhaust and a cam swap puts these engines at over 400HP without breaking a sweat. Not bad for a 60 year old design. The fact is both engine types have their use and applications.

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Back in the 80's Motorsport were able to get over 1,000hp out of a 1.5 liter turbo 4 cylinder for one of their race cars

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Hmmmm....a piece of junk, "push rod" Top Fuel engine makes over 7000 horsepower.

[/QB]

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Yes but they are using up to 500 cubic inch V8's which is up to 8.2 liters. So they would be making less horsepower per liter while using nitromethane instead of gasoline

 

[mechtech]

Like GMan said, you can't compare two differently sized engines, and attribute the greater power of the larger engine to being a pushrod design!
My goodness!

 

[dailydriver]

quote:

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Originally posted by windnsea00:

quote:

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Originally posted by Last_Z:

quote:

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Originally posted by windnsea00:

quote:

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Yes, the European engines do produce more power from less, but I think this is due to different engine design doctrines. Americans prefer not to stress the engines, therefore going bigger. Europeans and Japanese designs do produce more HP/lt, but at the price of reliability and/or low end torque. A good example is the BMW 3.0 making 333HP (M-3)....how many owners have blown their engines?! That's 110HP/lt!
Lastly, my LS1 made 300HP and 315lb/ft of torque to the rear wheels. That's about 345/360 respectively to the flywheel....on a basically stock engine. Full exhaust and a cam swap puts these engines at over 400HP without breaking a sweat. Not bad for a 60 year old design. The fact is both engine types have their use and applications.

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Back in the 80's Motorsport were able to get over 1,000hp out of a 1.5 liter turbo 4 cylinder for one of their race cars

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Hmmmm....a piece of junk, "push rod" Top Fuel engine makes over 7000 horsepower.

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Yes but they are using up to 500 cubic inch V8's which is up to 8.2 liters. So they would be making less horsepower per liter while using nitromethane instead of gasoline

[/QB]

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First of all, most, if not all of the Formula 1 teams of that spec/era were getting that much power out of their engines, NOT just BMW! Second I would not call the fuel they were using to make that power at those boost levels "gasoline". Third, hp/liter is one of the most laughable, ridiculous, stats ever thought up by anyone. It is the first thing spewed out by f@rt-piped import punks when they lose to faster machinery.
The performance of the vehicle is the ONLY stat that should matter!!

 

[windnsea00]

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Third, hp/liter is one of the most laughable, ridiculous, stats ever thought up by anyone. It is the first thing spewed out by f@rt-piped import punks when they lose to faster machinery.
The performance of the vehicle is the ONLY stat that should matter!!

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Funny how the rest of the world uses hp per liter as an important measurement except US, hmm. The fact is that it can demonstrate the efficiency of the motor by how much power it can use from its size. Obviously it's much easier/cheaper to get 330hp out of 5.7 liter V8 then a 3.2 liter I6.

 

[Last_Z]

-2002 Camaro Z28, LS1 6-speed
-All stock except for filter box lid (even down to the smallish 245/50/16 radials)
~3400 w/o driver

[email protected]

A few thousand miles after that, added a Hooker catback and ran a [email protected]. The cluth was already fried. Bring me a $135,000 Ferrari 355 and I'll smoke it!

I don't care how it's done.....get me there FAST and CHEAP!

Compare the 92 Corvette ZR1 (DOHC) to the new C5 and C6 (OHV) Vettes....that should settle some of the argument.

EDIT: Someone said something about the high RPM potential of OHC engines......NASCAR's 355 push rod engines wind up to 10k.

 

[greenjp]

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Originally posted by windnsea00:

Funny how the rest of the world uses hp per liter as an important measurement except US, hmm. The fact is that it can demonstrate the efficiency of the motor by how much power it can use from its size. Obviously it's much easier/cheaper to get 330hp out of 5.7 liter V8 then a 3.2 liter I6.

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The only time when hp/liter is relevant is if you're in a situation where displacement is limited, by rule or regulation or tax or something. For the US market, it's meaningless outside of being a technical curiosity for some.

The other "efficiency" we've heard people tout is power per unit of fuel. Generally in the context of OHC engines being "more efficient" at producing power (not the same as fuel efficiency). The only time this is relevant is if you're running an engine in a steady state, such as a generator or something similar. In an automobile, which is operating well below max power output the vast majority of the time, this sort of efficiency definition is also irrelevant.

Everyone should stop talking about hp/liter or efficiency with respect to power/unit of fuel. They have very little meaning to a discussion about our cars.

jeff

 

[Ryan00TJ]

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A good example is the BMW 3.0 making 333HP (M-3)

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The I6 in the M3 is a wonderful engine but one must remember it is at the peak of power capability as well as the mentioned Honda S2000 engine. The LS1 was rated at 325-350HP depending on which vehicle you ordered. It's very detuned from the factory with a small cam etc.... I have basic bolt ons, larger cam and better heads on mine. Results 420rwhp from 5.7L or 475HP at the flywheel. It still drives 98% like it did off the showroom floor and gets 26 MPG on the freeway.

My point is take the LSX engines and gear them to the limit and you will see power that will knock your socks off with reliability to boot.

The 7.0L LS7 has thrown down 665rwhp or over 700flywheel HP with a little tweaking. It's rated at 500 flywheel HP. This alone shows how detuned the motor is in factory form.