Efficient Modern Engine Design? | FerrariChat

Efficient Modern Engine Design?

Discussion in 'General Automotive Discussion' started by lashss, Sep 1, 2015.

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  1. lashss

    lashss F1 Rookie

    Nov 26, 2003
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    LSJ
  2. opencollector

    opencollector Formula Junior

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    OHC on street cars is primarily an artifact of tax shelters and design aesthetics.
     
  3. GordonC

    GordonC F1 Rookie
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  4. lashss

    lashss F1 Rookie

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    Gordon, you are right. However, wisdom has been present for even longer...back to the Can Am era. I have an article in my library by a UK writer commenting on the efficiency advantages of OHV architecture vs the Ferrari and Porsche OHC designs in Can Am cars.

    So, yes an 11yr old article, but the question still remains.

    Replace the date with August 31, 2015 or August 31, 1965.

    Will the general public ever "get" the engineering?

    Probably not...

    We can enjoy the real facts and discussion here while regular people believe the HP/Liter fallacy in the magazine ads from the last five decades.

    LS
     
  5. INTMD8

    INTMD8 F1 Veteran
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    Jun 10, 2007
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    LS is a great engine, I work with them every day. What is the HP/Liter fallacy however?

    That isn't the end all but certainly tells you something about the engine. There are arguments for packaging size vs hp, fuel economy vs hp, weight vs hp and I get all that, but hp per liter tells you something about the rpm range and dynamics.

    For instance, an F355 and a C5 Corvette may have similar performance in a straight line but the driving characteristics are of course vastly different. (and what power would an F355 make with a 2 valve pushrod head)
     
  6. bobzdar

    bobzdar F1 Veteran

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    Everything is a compromise (except when it isn't). Corvettes have a cost target, pushrod is a good compromise.

    Look at the bugatti veyron or laferrari, fairly no compromise vehicles and no real argument for pushrods.
     
  7. PerKr

    PerKr Formula Junior

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    they also have conservative customers whom they have convinced that pushrod is better in every way.

    Pushrod designs have a few advantages (size and COG mainly from what I've read) but also some disadvantages. Most car manufacturers do not really suffer from having to find a way to fit a rather large engine into a rather small car but claiming so is a great excuse to keep the pushrods.
     
  8. solofast

    solofast Formula 3

    Oct 8, 2007
    1,773
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    There are four figures of merit for engines. One is power to weight ratio, the second is power to volume, the third is fuel consumption and the final one is cost. The pushrod V8 beats the heck all of the other configurations on three out of the four and can be about the same on fuel consumption (or a bit better due to less internal friction). If you want the best performance and there are no rules the pushrod V8 is superior.

    As the article noted, to make power you have to move air. You can move more air more efficiently with a larger displacement but more simple engine or you can increase the complexity and spin the engine faster. If you limit displacement (per European tax regulations or racing rules) then there is a case to be made for more complex valve trains. But these limitations are arbitrary. If you don't have arbitrary limits on displacement, a larger displacement lighter configuration is the superior way to make power.

    The pushrod LS series of engines has about the same weight as the Porsche flat 6, and is superior in every figure of merit making a lot more power, having better low end torque, better fuel efficiency and is a lot less expensive to produce.
     
  9. lashss

    lashss F1 Rookie

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    "What is the HP/Liter fallacy however? "

    You could argue that any measure of efficiency would be represented as unit of output per unit of precious resource.

    HP/weight, HP/MPG, etc.

    Engine displacement (liters) is not precious because it doesn't correlate directly with mass or fuel efficiency (two very precious things). As mentioned earlier in this thread, HP/liter is an outdated ratio.

    An engine like the LS is actually very efficient by the more important measures. It wouldn't matter if it was 2.0 liters or 12.5 liters. It is still relatively small, light and fuel efficient for the output.

    Pushrod engines with their single cam and 2 valves/cyl have inherit design advantages by being smaller and lighter than OHC.

    It is entertaining to discuss but I am worried that all manufacturers will eventually just give in to marketing (like most have) and move to the less clever engine architecture to sell cars.

    LS
     
  10. zudnic

    zudnic Formula 3

    Nov 13, 2014
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    Auto makers need to look at the high performance marine industry. In particular Mercury Racing, they have V8's up to 1550 hp. Their 1350 V8 runs on regular pump gas 91 octane. They even have a warranty.

    1350 | Mercury Racing
     
  11. malex

    malex Formula 3
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    You do realize that that engine weighs over 1700 lbs, right?

    Impressive power nonetheless from a 9L turbo engine - though less impressive from a power to weight standpoint.

    I'm not sure the auto makers need to look elsewhere. E.g., GM seems to have it figured out with engines like the Corvette's LT4, which delivers 650 hp from an engine that weighs around 530 lbs including the supercharger. Yes, the Merc engine delivers a lot more power per liter, but that's really a matter of the high boost that it runs (and the presumably heavy block and cylinder head castings needed to withstand that much power).
     
  12. lashss

    lashss F1 Rookie

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    Nice output from the Mercury engines but if they do weigh 1700 lbs, it is not very good from a packaging standpoint.

    Here's a very reputable builder:

    Nelson Racing Engines - 454 LSX Intercooled Twin Turbo

    1175hp on 91 octane from a tiny LSX block with one camshaft and 16 valves. 1650hp on race gas?

    This looks impressive to me considering how small and light this engine is even with the twin turbos.

    LS
     
  13. INTMD8

    INTMD8 F1 Veteran
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    I recently did a twin turbo 427 LSX that made 1350 to the tires. Sooo, you could say I'm a fan, I just think hp/liter is still relevant.
     
  14. cptndon

    cptndon Formula Junior
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    just a note: the weight quoted includes the trans and drive
     
  15. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Mercury road going version is 699 lbs with all it's ancillaries, not 1700.
     
  16. bobzdar

    bobzdar F1 Veteran

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    Those are racing motors, not warrantied production motors. The highest output production lsx in na form is 505hp. To get more, they put sc's on them that increases the weight quite a bit. Compare the 505hp ls7 at 454lbs to some of the higher output na motors out there and their weights for a more apples to apples comparison- 458s makes 597hp from 460lbs (209kg), LaF makes 790hp from 500lbs (without hybrid) both na. They make more power per weight than the highest output na production lsx by a good amount. If you want to compare to the SC motors, The 488 v8 weighs less than the 4.5 in the 458 (but more than the 458s motor, so between 460 and 480lbs) including turbos, which makes it significantly less than the ls9's 529lbs, and makes the same power.

    So the pushrod motors compete well on cost and efficiency, but not on power/liter or power/weight, at least not for production motors - as I said, a compromise. A Vette is 1/4 the price and gets almost 10mpg better, so not a bad compromise - but a large part of that efficiency gain is gearing. Vette's are geared for mpg, Ferraris for acceleration. compare the final drive ratio 7th gear on both of them, it's not all (or even mostly) due to the engine.

    These racing motors are neither here nor there, might as well compare to an f1 v10 from the mid 2000's that were making 1000hp from a small na 3 liter engine that weighed only 200lbs!
     
  17. leead1

    leead1 F1 Rookie

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    Modern Push rod engines are so refined like the Corvette.

    If you drive Push rod and OHC cars you notice several things

    OHC engines have higher rev limits, 458 is 9500 RPMs, most push rods are much less than that. RPM is one way to gain HP with a smaller engine.

    Most push rod motors do not rev up as spirited or as quickly as Over head cam motors.

    having said that most modern engines are so well engineered it really does not matter. both designs can be in fun cars that are powerful.

    The new C7 Corvette is a world class drivers car. It is my favorite. I think the 458 Ferrari is not as fun. Great sound tho and a work of art to the eye.

    best

    Lee
     

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