5,000, the magic number?

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Boz Mon

Boz Mon

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I read a lot of car magazines with road tests and dyno sheets and such. Lately I have been noticing that most cars make peak power at around 5000-5300RPMS. For example: Honda VTEC crossover is at 5200RPMS and some of the V-8s I have seen is Hotrod Magazine make power at 5200RPMS. Is there some sort of explanation for this or is it just a coincidence?
 
I'm sure physics would elaborate on this more than I can, but at the molecular level an engine moving at ~5000RPM is a lot of metal moving REALLY fast generating a LOT of heat. May have something to do with that.

But 'peak power at 5k' is not what you've got in most of your examples, and your examples are flawed anyway. I'm not really up on the American engines, other than they actually deliver power earlier than 5k. But the VTEC comment is purely wrong. You make it sound like it's generic and all Honda VTEC engines function the same. They infact do not. Some are gradual stepped VTEC, and others are hard cut-overs. The S2000 actually engages at 6k, my Civic I believe engages at 4k. I'm sure some engage closer to 5k, but they obviously are not all the same. And VTEC engagement is far seperate from peak power output. The S2000 actually delivers peak power at 7200 or 8900, depending on the engine / year of the car.

So basically your 'discovery' of a magic number isn't even a discovery. It's an innaccurate observation.

(:
 
Well I know some V8's that go up to 10,000RPM. They sound quite nice.
 
Ok in the last 5 minutes I've been doing some research and some of the cars go over my original thought of 5300RPMs but they are all less than 6 grand

Source Car and Driver June 2005:

Audi A4 2.0T Quattoro 197Hp@5100RPM
Chevrolet Colorado LS 220Hp@5600RPM
Dodge Dakota SLT 250Hp@5200RPM
Honda Ridgeline (with SOHC VTEC) 255Hp@5750RPM
Nissan Frontier LE 265Hp@5600RPM
Mercedes-Benz SLK55 AMG 355Hp@5750RPM
Ford Mustang GT 300Hp@5750RPM

Chevy High Performance Magazine July 2005 (they build most engines for performance and drivability)

LT-1 Small Block 391Hp@5400RPM


edit: ok scratch the VTEC thing

04 S2000 240Hp@7800RPM
97 Prelude 195Hp@7000RPM
97 Integra GSR or Type-R I dont know which one? 195@8000
thats all I got for now, I'm just trying to make myself look like less of an idiot. I'm gonna go do some VTEC research now......
 
There's nothing special or magical about the 5,000 RPM range. What you are observing is a logical engineering conclusion that most mass-production car manufactuers come to: that most production engines have horsepower curves that peak shortly before the the redline, and that many engines have redlines in the 6,000 RPM range.

I would bet that if you look up the redline for all the engines on your list, you will notice that it will be peak power + 500-800 RPM.

The reason 6-6.5k redlines are common is because most modern over-head cam designs with 4 valves per cylinder flow fairly efficiently in that range.

Take a high reving motor that breathes really well like the S2000, M3, 911 GT3 or any recent Ferrari engine and their horsepower peaks are in the 7,000+ range.

Take an older pushrod motor like one from a 5.0 Mustang and you'll see the horsepower peak is much lower.

It's just engineering, economics and marketing at work.


M
 
I've got an older pushrod motor that puts out peak power around 7000rpm... I guess an old 500cc Honda VTwin isn't your average pushrod motor though :)
 
Power (hp) = Torque (lbft) x Current rpm/5252rpm

Draw your own conclusions.
 
Well my question is do the engineers for most consumer vehicles' engines conciously decide to make the maximum horsepower and torque numbers same/close to each other, therefore the engines need to be making them around 5252RPM?
 
Famine
Power (hp) = Torque (lbft) x Current rpm/5252rpm

Draw your own conclusions.
Click to expand...

If you're able to produce the same torque at a higher rpm you produce more horsepower. Car manufacturors want a completely flat torque line extending as far up in the rpm range as possible. A car with decent torque can produce great hp if the rpms are high enough (enzo).

I don't think efficiency of aspiration is the limiting factor (as I believe someone said) but rather reliability. With a normal set of internals the engine's life will be reduced greatly if it's spinning at 10,000rpm all day. Lighter valve trains using titanium and sodium filled valves reduce the forces on the internals. Overhead cams reduce the number of parts compared to pushrod engines (no pushrods or rockers). It's harder for a pushrod engine to attain high rpm, not impossible.
 
Yes, xcsti is right, there is more to it than airflow, but also a balancing act between weight, complexity and cost to manufactuer.

All I'm saying is there is no strict scientific reason why many production engines these days make peak power in the 5000-6000 range. The reasons are largely economic in nature.

If everyone suddenly decided tommarrow that they wanted small displacement, high reving engines that have peaky power curves like the S2000, then that's what automakers would make.


M
 
Boz Mon
Wow I feel like an idiot now :dunce:
Click to expand...

You shouldn't - except the VTEC thing your observation is correct. Here's peak power for cars that I've randomly flipped to in ConsumerGuide:

Dodge Stratus RT coupe: 200@5500
Honda Accord 2.4: 160@5500
Jaguar XJ8: 294@6000
Lincoln Mark LT: 300@5000
Mini Cooper: 115@6000
Mitsubishi Endeavor: 225@5000
Pontiac G6: 200@4800
Porsche 911 Turbo S: 444@5700
Saab 9-2X 2.5i: 165@5500
Saturn Ion: 140@5800
 
M5Power
You shouldn't - except the VTEC thing your observation is correct. Here's peak power for cars that I've randomly flipped to in ConsumerGuide:

Dodge Stratus RT coupe: 200@5500
Honda Accord 2.4: 160@5500
Jaguar XJ8: 294@6000
Lincoln Mark LT: 300@5000
Mini Cooper: 115@6000
Mitsubishi Endeavor: 225@5000
Pontiac G6: 200@4800
Porsche 911 Turbo S: 444@5700
Saab 9-2X 2.5i: 165@5500
Saturn Ion: 140@5800
Click to expand...

That's not 5 grand. With the exception of three it's consistently well over. The average max power RPM for this group is 5480. That's nearly 10% over his observation. With the three missing it comes to 5714. That's no where near 5000.

But I guess if you're talking in terms of baseball batting averages, he's batting a 0.300. Hey not bad! Sign him up! If you're talking in terms of any other kind of performance rating, he's got a 30%. Uber shat.

Thanks for fueling the fire.
 
I don't know what is the big deal here???....................5000rpm or 10000rpm
Who gives a damn??
Most cars can be pused beyond their redlines,cause redlines are set as a safety measure by the makers,to make sure that the motors would last a bit longer,so to say that there is a thing for the 5000rpm is just moronic.
 
///M-Spec
If everyone suddenly decided tommarrow that they wanted small displacement, high reving engines that have peaky power curves like the S2000, then that's what automakers would make.


M
Click to expand...

Exactly.
 
Yeah, I would say it has more to do with trends than anything. But I would imagine there's something in physics that has to do with a certain range. Heat / friction / velocity ... perhaps the metals and lubrication we use for engine building works best at those speeds.

EMERGENCY! Is there an engineer int he house?!?
 
There's nothing special about 5000rpm, thats just what's common.

It has nothing to do with the 5252 in the horsepower equation that's posted above, that's just a coincidence.
 
LoudMusic
That's not 5 grand. With the exception of three it's consistently well over. The average max power RPM for this group is 5480. That's nearly 10% over his observation. With the three missing it comes to 5714. That's no where near 5000.
Click to expand...

He said 5000 but he amended it during the post to say 5000-5300. And 5480 is pretty close to 5300, if you ask me. Oh, and for the record:

Vehicles that peak at 5300rpm or less
Audi A3 2.0T: 200@5100
Audi A4 2.0T: 200@5100
Buick LeSabre: 205@5200
Buick Park Avenue: 205@5200
Buick Park Avenue Ultra: 240@5200
Buick Rainier V8: 300@5200
Buick Rendezvous: 185@5200
Buick Terraza: 200@5200
Cadillac Escalade: 345@5200
Chevrolet Avalanche 1500: 295@5200
Chevrolet Avalanche 2500: 320@4200
Chevrolet Equinox: 185@5200
Chevrolet Impala: 180@5200
Chevrolet Impala LS: 200@5200
Chevrolet Impala SS: 240@5200
Chevrolet Monte Carlo LS: 180@5200
Chevrolet Monte Carlo LT: 200@5200
Chevrolet Monte Carlo Supercharged SS: 240@5200
Chevrolet Silverado V6: 195@4600
Chevrolet Silverado 4.8: 285@5200
Chevrolet Silverado 5.3: 295@5200
Chevrolet Silverado SS: 345@5200
Chevrolet Suburban 1500: 295@5200
Chevrolet Suburban 2500: 325@5000
Chevrolet Suburban 8.1: 320@4200
Chevrolet Tahoe: 295@5200
Chevrolet Trailblazer EXT V8: 300@5200
Chevrolet Uplander: 200@5200
Chrysler 300C: 340@5000
Chrysler Pacifica: 215@5000
Chrysler PT Cruiser: 150@5100
Chrysler PT Cruiser Turbo: 180@5200
Chrysler PT Cruiser GT: 220@5100
Chrysler Town & Country 3.3: 180@5000
Chrysler Town & Country 3.8: 207@5000
Dodge Caravan 2.4: 150@5200
Dodge Caravan 3.3: 180@5000
Dodge Grand Caravan: 207@5000
Dodge Dakota 3.7: 210@5200
Dodge Dakota 4.7: 230@4600
Dodge Durango 3.7: 210@5200
Dodge Durango 4.7: 230@4600
Dodge Durango 5.7: 335@5200
Dodge Magnum 5.7: 340@5000
Dodge Neon SRT-4: 230@5300
Dodge Ram V6: 215@5200
Dodge Ram 4.7: 235@4800
Ford Crown Victoria: 224@4800
Ford Crown Victoria LX HP: 239@4900
Ford Excursion: 255@4500
Ford Excursion V10: 310@4250
Ford Excursion TDI: 325@3300
Ford Expedition: 300@5000
Ford Explorer V6: 210@5100
Ford Explorer V8: 239@4000
Ford F-150 V6: 202@4350
Ford F-150 4.6: 231@4750
Ford F-150 5.4: 300@5000
Ford Freestar 3.9: 193@4500
Ford Freestar 4.2: 201@4250
Ford Mustang V6: 210@5250
Ford Ranger 2.3: 148@5250
Ford Ranger 3.0: 148@4900
Ford Ranger 4.0: 207@5250
GMC Envoy XL/XUV V8: 300@5200
GMC Sierra V6: 195@4600
GMC Sierra 4.8: 285@5200
GMC Sierra 5.3: 295@5200
GMC Sierra Denali: 345@5200
GMC Yukon 5.3: 295@5200
GMC Yukon Denali: 335@5200
GMC Yukon XL 2500: 320@4200
Hummer H2: 325@5200
Infiniti QX56: 315@4900
Isuzu Ascender 7-passenger V8: 300@5200
Jeep Grand Cherokee V6: 210@5200
Jeep Grand Cherokee 4.7: 230@4700
Jeep Grand Cherokee 5.7: 325@5100
Jeep Liberty 2.4: 150@5200
Jeep Liberty 3.7: 210@5200
Jeep Liberty TD: 160@3800
Jeep Wrangler 2.4: 147@5200
Jeep Wrangler 4.0: 190@4600
Lexus LX470: 235@4800
Lincoln Mark LT: 300@5000
Lincoln Navigator: 300@5000
Lincoln Town Car: 239@4900
Mazda B2300: 143@5250
Mazda B3000: 154@5200
Mazda B4000: 207@5250
Mercedes E320 CDI: 201@4200
Mercedes CL600: 493@5000
Mercedes S600: 493@5000
Mercedes SL600: 493@5000
Mercury Grand Marquis: 224@4800
Mercury Grand Marquis LSE: 239@4900
Mercury Monterey: 201@4250
Mercury Mountaineer V6: 210@5100
Mercury Mountaineer V8: 239@4000
Mitsubishi Endeavor: 225@5000
Mitsubishi Galant V6: 230@5250
Nissan Armada: 305@4900
Nissan Frontier 2.5: 154@5200
Nissan Titan: 305@4900
Pontiac Aztek: 185@5200
Pontiac Bonneville: 205@5200
Pontiac G6: 200@4800
Pontiac Grand Prix: 200@5200
Pontiac GTO: 400@5200
Pontiac Montana SV6: 200@5200
Saab 9-3 2.0HT: 210@5300
Saab 9-5 Aero: 250@5300
Saab 9-7X V8: 300@5200
Saturn Relay: 200@5200
Toyota 4Runner V6: 245@5200
Toyota Land Cruiser: 235@4800
Toyota Prius: 76@4500
Toyota Tacoma 2.7: 164@5200
Toyota Tacoma 4.0: 245@5200
Toyota Tundra V6: 245@5200
Volkswagen Jetta 2.5: 150@5000
Volkswagen Jetta TDI: 100@4000
Volkswagen Golf: 115@5200
Volkswagen Golf TDI: 100@4000
Volkswagen New Beetle: 115@5200
Volkswagen New Beetle TDI: 100@4000
Volkswagen Passat TDI: 134@4000
Volkswagen Touareg TDI: 310@3750
Volvo S40/V50 T5: 218@5000
Volvo S60/V70 2.5T: 208@5000
Volvo S80 2.5T: 208@5000
Volvo S80 T6: 268@5200
Volvo XC90 2.5T: 208@5000
Volvo XC90 T6: 268@5200

Thanks for fueling the fire.
Click to expand...

:rolleyes: Get over yourself.
 
retsmah
There's nothing special about 5000rpm, thats just what's common.

It has nothing to do with the 5252 in the horsepower equation that's posted above, that's just a coincidence.
Click to expand...

Hence "Draw your own conclusions".

Screwing with people's heads is one of my hobbies... :D
 
M spec and xcsti are bang on. Uncle george in his nice family car doesn't want a screaming 12000 rpm motor, he wants accessible easy low range power and a wide torque curve. As well as a million cup holders and a comfy seat. Dave in his S2000 wants a howling redline, so that's what he gets.

The reason some cars rev higher is due to their piston geometry. A wider bore and short stroke will give an engine a low torque output, as the short stroke crankpins have a small lever effect about the crankshaft centre. However, the mean piston speed is lower for a given RPM, so you can push the revs higher, generating more power, while keeping a safe mean piston speed.

Mean piston speed can be calculated at a given RPM by taking the stroke (in metres) say 0.1 for a 100mm stroke, doubling it to 0.2 (one up and down revolution) multiplying it by the rpm e.g. 5000, giving 1000, then dividing it by 60 (as in "per minute") giving (0.1x2x5000)/60 = 16.67m/sec.

The maximum value for this figure is wide open to interpretation, but typically anything over 20 is working really hard, and approaching 25 is courting a major failure. The mass of the piston and strength of the rod also impacts on this but it's a reasonable basic calc method.

The rev limit for most cars is determined more usually by the valve gear; valve float and bounce can be a limiting factor more quickly than piston speed. Springs are notoriously bad for this, many manufacturers have tried Desmodromic drive in the past, it uses cams but no springs or air pressure.

cheers,


Kurtis.
 

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