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Small Displacement High RPM Engines

  1. Aug 17, 2014 #1
    I'm looking into buying an E34 530i with a smaller 3 liter V8 compared the the 540 4.4 liter V8. A lot of people online say buying a 530 is pointless when you can get the same car with more displacement and more power. I think that's ridiculous since displacement is only 1 of many ways to make power. Volumetric, Mechanical and thermal efficiency all have a factor. Port geometry and mechanical timing as well. Look at formula 1 or a company like ferrari and you always see a high revved small displacement engine. My Kawasaki ZX6R has 600cc's of displacement and it makes 107hp at 14k rpms. So bring the rpm's up. Make sure you have oil pressure to bearings and friction surfaces and adjust your valve timing to make power at a higher rpm. What else is possible trying to go this route? Also what are the benefits and draw backs of going a route like this?
     
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  3. Aug 18, 2014 #2
    The point of your post isn't completely clear. Why are you buying the 530 over the 540?

    It's comes across like you are thinking that you'll buy the smaller engine then do 'something' to it to make the same power. It won't, not without a considerable injection of cash. As in buy an M5 it'd be much cheaper type of cash.
     
    Last edited: Aug 18, 2014
  4. Aug 18, 2014 #3

    Ranger Mike

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    there is no substitute for cubic inches.
    "If some is good, and more's better, then too much is just enuff!" Stoker Mcgurk 1950
     
  5. Aug 18, 2014 #4
    It's pointless because the 540i comes out of the box with 286bhp and 300lbft. The 530i barely makes any more power than the 525i, yet it barely drinks any less than the big V8.

    Sure, you could probably tune it up to the same power output, but you'd spend 10x the amount that you could buy a 540 for, it wouldn't be reliable, it would have a fair whack less torque and it wouldn't be as nice to drive as result.

    There is literally no pro's to this idea at all. Not a single one.

    Consider this, you can get 200bhp out of a 1199cc Ducati engine, which would be enough to pull the big 5 series along at a reasonable pace. Would you want to drive this car though?
     
  6. Aug 18, 2014 #5

    rcgldr

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    Generally a smaller powerband. Since you mentioned motorcycles as an example, compare a 1 liter race replica like a Suzuki GSXR 1000, versus a 1.35 liter hyperbike like a ZX14. The 1 liter race replicas make most of their power in the upper 1/3rd of their rpm range, and feel like 600cc bikes when out of the powerband. Peak power on the 1.35 liter hyperbikes is about the same, but those bikes get 80% or more of their peak torque in the upper 2/3rds of their rpm range, like from 3500 rpm to 10500 rpm.

    For a sports car comparison, the 2006 - 2013 Corvette Z06 uses a 7.0 liter engine, making 505 hp, and it's lighter than the Porche 911 3.6 liter turbo charged engine which makes from 480 hp to 520 hp (depends on model and year). The Z06 manages to get reasonable highway milage (25 to 26 mpg) since the engine is running at 1500 rpm at 70 mph == 112 kph.
     
  7. Aug 18, 2014 #6
    The cylinder head's are the same. The cams are the same. It seems ridiculous to say don't ever tune or modify a 530 because a M60B40 has 1000cc's more displacement.Your pretty much saying leave a 540 alone as well. I'm more interested in why formula 1 and other company's prefer the high rpm small displacement engines to make the same power as a bigger engine. Fabricating a set of headers to mount a twin entry centrifugal compressor and using a DTA standalone would be a piece of cake. I'm not concerned about that. I respect everyone's opinions and input.
     
  8. Aug 18, 2014 #7
    First things first: Power comes from how much fuel you can burn in a given amount of time, by extension the most important thing is how much air you can flow. bolded the important bit.

    You do this 3 ways.
    1. More displacement (more air per cycle)
    2. Forced induction (more air per cycle)
    3. Higher revs (more cycles)

    F1 have their displacement and configuration fixed by the rules. As they used to N/A they couldn't use method 1 or 2, so had to use method 3.

    The downside was the all low engine power was scarified for top end power. So much so that the 2.4L V8's didn't idle below 6000rpm. This is fine if you are racing an engine, and will only ever spend your time in the top of the power band. Not so good if you need to drive round town.


    As a very rough 1st approximation we can apply this to the M60.
    B30 - 3.0 displacement 215HP @ 5800rpm
    B40 - 4.0 displacement 285HP @ 5800 rpm
    The B40 has an extra 33% displacement, and near as damn it 33% more power.

    Also, if my memory serves me correctly, the cylinder heads of the B30 and B40 are not the same, hell they had a different bore. The 530i also produced less low end power than the 535i it replaced as it is highly over square. To get to a similar power output you'd need to rev the 3.0 to 7800rpm and have it flow the same amount per cycle and keep it N/A.

    The point is not that you shouldn't buy one or that you shouldn't tune it. If you want a 5 series with about 220hp, then the 530i is right up your street. If you want something more powerful why would you deliberately buy the less powerful engine and then alter it when the 540i is available.


    It's like going to the shop and buying a pair of trousers that a too large in the waist and too short in the leg. You may be a whiz with the sewing machine, but buying the pair that fits in the first place is a great deal less hassle.
     
  9. Aug 18, 2014 #8

    cjl

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    2 things:

    1) They can't make as much power with a small engine as they could with a similarly high-strung big engine.
    2) They don't prefer tiny engines. They're required to use tiny engines by the rules of their racing series.

    For an extreme example, the most powerful engines in car racing today are 500 cubic inch nitromethane V8s. They put out about 10x as much power as a formula 1 car (with admittedly much lower reliability requirements).
     
  10. Aug 18, 2014 #9
    I think buying a 530 is about the dumbest thing you can do if performance is a consideration. That has to be the heaviest 3.0 liter engine I have ever seen, why wouldn't you get a slightly newer E39 4.4 or 4.6L 540 that has much better suspension, and way more power than you'll ever make by throwing tons of money at a M60b30.

    The only reason anyone ever uses a smaller displacement engine is if they are required to by rules, or they can save weight by doing so. That 3L v8 weighs just as much as it's bigger brothers(the 4.0-4.6L M60s), and I don't know of any racing class that a e34 530i would be competitive in.

    Oh, and if you are really looking at the E34 530 because it's initial price looks good. You better consider the maintenance and repair costs are the reason these cars are so cheap now. You could actually save a lot of money in the long run by buying a newer BMW, or something that is not a BMW.

    You would be a lot better off with a 6 cylinder E39 530 or 528. it would actually be quicker than the e34 530, and get better fuel mileage and be a lot more reliable. With the E34 530 you get the worst of both engines: the low power of a 6 cylinder and the low reliability and high weight of the V8.
     
    Last edited: Aug 18, 2014
  11. Aug 18, 2014 #10
    Why don't you start pulling those headers off the m60 before you say it's a piece of cake. There's barely room for the stock headers, which are double wall by the way. It is double wall to keep from melting everything in the area since it's in there so tight.

    Even if you are capable of doing everything yourself, you could get a 535i with a twin turbo or twin scroll single turbo 3.0L six for a lot less than what you'd spend on parts for the 530 turbo project.
     
  12. Aug 18, 2014 #11

    rcgldr

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    They don't. The rules for Formula 1 restrict the engine size. This year they're using turbo charged 1.6 liter V6 engines (in 2013, it was naturally aspirated 2.4 liter V8's). Compounding matters for 2014 is fuel is limited to 100kg per race (it wasn't limited before, but typically around 160kg per race), and although the 2014 rules allow up to 15,000 rpm, the engines are tuned to produce peak (and less) power at around 11,000 rpm (with redline less than 12,000 rpm) in order to meet the fuel usage requirements.

    In the older FIA GT1 race class, restricter plates were used to limit power, but there was no restriction on engine size. From 2005 to 2009 Corvette C6.R GT1 class cars used 7.0 liter pushrod V8's (590 hp) because they could produce more torque. Aston Marton used 6.0 liter DOHC 48 valve V12s (600 hp) in their DBR9 GT1 cars.
     
    Last edited: Aug 18, 2014
  13. Aug 19, 2014 #12
    Nobody said that. Regardless of whether you just want more power, or want to go through the whole process of tuning to get that power, the 540 is a better base. It has more to start with, and would end up with more if you applied the same tuning to it.

    You obviously have a vested interest in justifying it over the equivalent 540, but there is no sound reason why it's a better choice because it just isn't.

    Also, I can tell you now that a 2.4 litre F1 engine in a 5 series would be horrendous. It'd work, sure, it would be bloody fast too on a track, but it would be absolutely awful to drive at anything less than flat out.
     
  14. Aug 19, 2014 #13
    I'd absolutely never want a F1 engine in a 5 series. I was more interested in some insight into the smaller displacement high revved engines and everyone just ran with the 530/40 comment.
     
  15. Aug 19, 2014 #14
    Personally, being a fan of Honda VTEC engines, I do get them. You can make 250bhp out of both the 1.6 and 1.8 litre engines found in the mid 90s Civics and Integras, though if you're going for power, nobody takes the harder route of the 1.6 as the 1.8 is a much better base to start from, even though the power cap is the same.

    The 540/530 is the same, sure the limit might be the same (as long as the bore size is the same) but why start with a handicap if you're not forced to by the rules?
     
  16. Aug 19, 2014 #15
    OP, why don't you try chucking the specs for both in on this engine performance calculator, you can vary a lot of inputs and you can see what the differences between the two engines would be and what you'd need to do to tune them.

    http://blackartdynamics.com/Engine/EngineThermodynamics.php

    I just looked up the specs for both engines and found bore x stroke of 84x67.6mm for the 3.0 and 89x80mm for the 4.0. Straight off the bat, the 4.0 has a higher power cap due to the bigger bore, the 3.0 will be limited to around 550bhp where the 4.0 could theoretically manage around 620bhp.

    The 3.0 could rev up to 11,000rpm owing to the short stroke, but to get that to happen would require a crazy amount of work. Even if you did it, it would make the low speed performance so dire that it would be undriveable on the street.

    Obviously, forced induction is another matter, but again you could apply the same gains + 33% to the 4.0 for basically the same cost.
     
    Last edited: Aug 19, 2014
  17. Aug 19, 2014 #16
    I understand that OP isn't after specifics regarding the 530 and 540 and that's kind of the way this has gone. OP I'm just interestesd as to why you would willingly pick a 530 over a 540, or even a 535? Also if you have any other, specific questions.


    Now! Disregarding that we don't want to be specific. ;)

    For forced induction the 4.0 would be better again as it has a lower compression due to the head and it has forged components. So you apply MOAR boost without running into detonation or stress issues.


    EDIT: It's kind of like the E90 325 or 330.
    The 330 has miles more power, more drivability, yet no worse economy in the real world and are just as reliable. I own a 325... because they are really cheap because no one wants them.
     
    Last edited: Aug 19, 2014
  18. Aug 19, 2014 #17
    Well i have a b5 S4, an 86 951 and a 93 525i; All turbocharged and tuned by myself. I initially just looked into the possibility of bringing the rpm's up and trying to get some more power out of it. Nothing was absolute in my mind. My second thought was to use a compressor and go the route that ford is using with the ecoboost. Small displacement for economy and the power on top end with the compressor spooled up. Big power wasn't really the main goal. I guess this same debate on the 540/30 could be the same as a E36 318i vs a 325, 335 etc
     
  19. Aug 20, 2014 #18
    Adding a compressor would be far easier, but again you'd still be better off with the 540i as a starting point. It's got a lower compression ratio for one, would make even more power and won't use any more fuel as 3 litre V8 is just a plain inefficient engine.
     
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