As you may have seen, Car and Driver did what they're supposed to do and stuck five Nissan GT-Rs on dynamometers to find out just what's up with the cars' world-beating performance. Er, I should say to find out what's up with the discrepancy between their various performances. C&D concluded that U.S. non-press cars make about 520 hp at the crank. Our man Berkowitz concluded that Nissan is feeding the buff books (and Edmunds) ringers. Regardless, does it matter? Here's a for instance… You know the Bugatti Veyron and how it makes 1,001 hp from its quad-turbo, 8.0-liter W16 motor? Well, in Europe it makes 1,020 hp. Something to do with the difference between our more accurate SAE net and the funny Euro (probably metric) whatever system. How does Bugatti explain it? The engines actually produce 1,040 hp, so who cares? And that's kinda my point. Remember when Mazda got "nailed" a few years ago for overrating the horsepower in the Miata. They said it made 155 hp, but in reality it only made 142 hp. Did it really effect the car? Or, closer to (my) home 2006 Subaru WRX had 230 hp when I bought it. Then a few months later the SAE rejiggered how they measure horsepower. Now my car makes 224 hp. Which is actually three horses less than my 2001 WRX. Do i care? Actually, I do. That really pissed me off. You?
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In the grand scheme of things, no. I’m not a road racer or anything by any stretch.
It does seem suspect when a manufacturer fudges the numbers though. Makes you wonder what else they’re misleading you on.
This was so much easier 150 years ago.
Eventually, there will come a day when you stop reading about your car and start driving it. At that point, what published numbers will change how it drives? Who cares what numbers anyone prints. Is my current car now rated at fewer horses than when I bought it? And what difference would that make in driving it?
Go take your car for a drive and stop reading numbers!
If you get a chance to drive a car hard and/or have access to reliable performance numbers, hp doesn’t matter too much. The car drives how it drives and puts up certain 0-60 and 1/4 mile numbers, regardless of rated hp
On the other hand, if I was anxiously anticipating the all-new 3rd (2nd?) generation Miata, partially because of it’s new and improved hp output, I would be very disappointed if I found out the engine was overrated after I had put down my deposit
The GT-Rs case is something else entirely. It’s not really a matter of how much hp the car has, it’s a matter of weather or not Nissan was using ringers in their press fleet.
So hp can be either entirely meaningless, or a very useful number. In any case, hp is more meaningful than hp/L, but I don’t even want to start that discussion
It depends on how much power the engine has in the first place.
Just as an example, I’ve been looking at trucks for a guide. The Ranger supposedly makes 143 hp in its four banger, Frontier 152, Tacoma 159, Colorado 185. At that level, I’d be pretty concerned if the ratings were off and the Frontier really only made the same horsepower as the Ranger, or if the Chevy only made as much as the Tacoma. The engines have enough trouble moving the weight of the vehicle around as it is at that level.
On the other end of the scale, at the 200 horsepower level, there’s more than enough power to spare, so it wouldn’t really matter if they were twenty or so horses off. Same with the Mustang’s V-8, for example. There’s already so much on tap, who cares if there’s a little discrepancy?
I care not one bit because whatever the manufacturer says the horsepower is, it simply isn’t enough.
And that’s why we have an aftermarket.
Part of me agrees with 86er, that yes, it does matter. If they fudge that, what else could they fudge. I don’t even want to get started on the ringer argument.
However, the motor is a handbuilt motor, and I’m reminded of a story about the E34 M5. It seems that, being mostly hand built in teams, test drivers could figure out which team built that specific M5. While it should be taken with a grain of salt, still, it brings up the point that in a non mass produced car with hand built motors as such, some discrepency is to be accepted.
However, I also fully believe that, at the end of the day, it doesn’t matter how much HP you have, how many lbft, hp/liter, none of it. ALl that maters is that you cross the finish line first.
quasimondo…my thoughts exactly.
Of course I care!
Manufacturers use HP numbers in all manners of advertising so they had better be as accurate as possible. As long as they know that the press and some customers actually use that published number as a basis of comparison from car to car, then isn’t playing games with the numbers simply false advertising?
Yet if the published HP of my car was amended today, it would not change how it drives. I made my own determination whether or not the engine power was adequate for me when I test drove it. But that doesn’t release the manufacturer from the responsibility of measuring and representing the HP truthfully.
I think what was mentioned in the other thread, and should be mentioned here, is that if the cars comming off the show room floors make the same numbers, then no big deal, all Nissan did was underrate just like most manufacturers do. If the cars coming off the show room floor are put on the rollers, and don’t hit the same numbers, then we have an issue.
Yes, I care about horsepower ratings. I’m always for having accurate metrics to explain things. Like why does my rental BMW 116i feel so pokey. (Answer: 113 HP). But if it’s in a realm where I wouldn’t be able to tell the difference, then I’m not concerned. There’s so much variance in test conditions and build tolerances that cloud the importance of horsepower ratings.
Fudging is obviously unacceptable, because as Steve-O pointed out, it is a huge advertising, selling, and comparison point. So what is the tolerance factor here? In other words, how much discrepancy is there between supposedly identical cars? 2%? If that’s the case, go ahead and post best-case numbers, but they better be 102% of the worst case.
“Eventually, there will come a day when you stop reading about your car and start driving it.”
Bravo.
If they change the way they measure horsepower, and thus the (artificial unit of measurement, remember) number goes down, and you’re actually upset…you have a maturity issue. Chances are you have aftermarket rims, non-functional hood scoops and possibly a huge rear spoiler.
The honest method from a bragging rights, truth in advertising perspective would be to have everyones cars dyno tested by an independent 3rd party like IIHS, UL, ETC etc. To guard against rigners cars would be randomly selected and tested after the initial certification.
If there are ringers in the press fleet, then it matters. If the ratings are inflated and the cars really have a lower output than advertised, it would bother me.
If they are underrating and give everyone more power than advertised, then I have no problem with it at all.
When the SAE J1349 certified horsepower standard was introduced, several manufacturers – Honda and Toyota, notably – saw reductions in their hp numbers. The Acura TL went from 270 to 258 and RL went from 300 to 290; the Accord went from 240 to 244, but was also noticeably quicker in several tests compared to the earlier model, so Honda probably tweaked the engine slightly to avoid having to admit that 240 was an overstated number (my own 2004 Accord has the 240 rating, and it slightly bothered me, but not knowing what the J1349 number is for it makes it slightly less annoying).
really don’t care. A car performs how it performs regardless of how many CRANK horsepower it makes.
And furthermore, who cares about crank horsepower ratings? What matters is what they put to the wheels, and with the wide range of drivetrain loss factors, crank horsepower isn’t really a good measuring stick. Why does a 227bhp WRX and a 200bhp GTI dyno at the same numbers at the wheels? Drivetrain loss.
Yes, but I have another question. Why extrapolate (decrapolate?) back to the crank from the wheel? The only interesting figure is WHP. If two cars weigh 3000 lbs, and have 300hp at the crank, but one has 10% drivetrain loss, while the other has 20%, why would I care that they are equal at the crank?
I don’t care. All that matters is how it makes me feel when I drive it. Throw those lame ass spec sheets out the window.
I care how many horses it has, just as I care (probably more) about foot-lbs of torque, at what RPM they become availible, and how flat that ‘curve’ remains throughout the range. I also care about accurate speedometers, fuel economy, and just about any other measurable bit of information on a car. Pretty much every automaker at one point or other has had some invalid information in one of these areas.
However, I realize there will be a slight margin of error in all of this, and a few percent seems acceptable. Comparing two cars where one has 143 hp and the other 150, HP isn’t going to be a big issue as it is too close to really feel a difference. On the other hand, looking at a car with 265 hp vs. one with 210, I am fairly sure I would be able to feel that. If all cars are measured at the crank, then fine, if all at the wheel, then that is fine too, drivetrain loss should be fairly even through similar drive-type models, just keep in mind AWD has higher losses than FWD or RWD.
Now, if Nissan was intentionally sending higher-performance versions of the car to the press and review outlets, that is an entirely different story. That is flat out fraud, and should not be tolerated under any circumstances.
I’d like to think that I’m getting my [hard earned] money’s worth of advertised horsepower when I write that check. I remember a recent SVT Mustang fiasco when the car didn’t perform as advertised because Ford overestimated the V8’s power figures and how owners were outraged (I believe it was the late 90’s SVT Mustang….I dunno, I don’t like Mustangs very much so I could be wrong). I think if you plunk down money for a 480hp car, then 480hp you should get and if the car actually makes more, call it a bonus. If it makes less, call your lawyer.
Don’t need to measure my johnson to know I’m a man. Don’t need an arbitrary number to tell me how a car performs….I prefer to judge by how it feels where it matters….in the drivers seat.
I dyno test a certain automaker’s V6 for a living. In the several hundred we’ve tested, the variance is pretty small. All are within 10 hp or so of each other.
One question about this handbuilt thing… I assume that only means assembly… not machining. The machining is where your variance really comes into play. Do they hand machine parts of the GT-R engine? I saw a program about Ferrari’s engine building process, and I could see a large amount of potential variance in that process. There is just so much that is done as basically a one-off on those.
Like Supaman, i paid for 507 of the little suckers and i want them all. however, it’s really the performance numbers that we should focus on, but HP ratings do need to be consistent and accurate if we are to effectively compare one car to another.
I care because you need some objective measurement to compare cars, and crank horsepower ratings should be fairly consistent. However, the manufacturers do sandbag.
Case in point: if Lieberman dynoed both his 2001 and 2006 WRXs (assuming they are still stock), he’d see a world of difference despite the similar claimed outputs. The 2006 2.5s made way more hp and tq than the old 2.0s.
“I care because you need some objective measurement to compare cars, and crank horsepower ratings should be fairly consistent. ”
So what about BMEP then?
Personally I think we should return to RAC horsepower ratings.
With a car you own, it makes no difference. It drives like it drives no matter what the numbers are. But, when you are bragging to your posse about your ride., while why not lie.
Maybe they should not advertise hp, but advertise 0-60 & 1/4 mile times…
hp doesn’t matter if you have a lardass car
hp doesn’t matter if the gearing is craptastic
Where the most useable horsepower (and torque) is made in the rev range is more important than how much peak is made.
The HP and Torque curves should be accurate, and readily available for customers to see.
Do I care that my new GTI’s motor makes 200 hp? Not really, however, I do care that peak torque comes around 1800 RPM and stays until about 5000 RPM. That matters more.
-ted
Only so far as I care about whether a car manufacturer is intentionally mistating power numbers to drive up sales. However, if I drive a car and like it, I couldn’t care less what its horsepower or torque numbers are.
Personally, I think people are making a mountain out af a mole hill on this one. Nissan has stated that the car has 480 hp. C&D tested 5 GTRs and found that the 3 strongest ones had 520 hp. From the C&D article: Though we didn’t get a chance to dyno-test the two slower GT-Rs, three of the five were so close in performance that we believe they accurately represent the GT-R’s capability. Clearly, Nissan is delivering more than the advertised 480 horsepower. And the most likely figure is about 520, which is yet another reason to bow to the best performance value since the Corvette Z06.
So what’s the problem? Nobody knows what, if anything, was wrong with the 2 slow cars because C&D didn’t conduct the same tests on them that they did on the “ringers”. Perhaps they had a wonky turbo. If C&D had tested everything and found that the cars all had the claimed 480 hp, would people still be saying that these cars were “ringers” and that customer cars will ship with less? And further, who’s to say that C&D didn’t cock up their testing? That’s just as valid a possibility.
People should wait utnil they see actual dyno #’s from a customer car (I’m sure there’ll be plenty of videos on youtube soon enough), before they take Nissan to task over this one.
Well, it’s best to use kW to measure the “horse power” :) Metric system rulz :P
Mechanical horsepower ≡ 33,000 ft·lbf/min
= 550 ft·lbf/s
= 745.6999 W
Metric horsepower ≡ 75 kgf·m/s
= 735.49875 W (exactly)
Electrical horsepower ≡746 W
Boiler horsepower ≡ 33,475 Btu/h
=9809.5 W
Hydraulic horsepower =Flow Rate(US gal/min) * Pressure(psi) / 1714
The Model A perspective –
Recently a freind gave me a ride around town in his Ford Model A – 1931 Vintage. He said the engine made 37 horsepower. Most published figures I’ve seen rate it at 40. I’m not going to quibble. What impressed me is that for the most part, the A is quite capable of keeping up with city traffic. Sure, starting off from a stop is a bit slow – you can’t shift real fast, you need to hesitate a bit or it’ll grind. But as far as HP goes, 40 is all that is needed for city driving.
40 of course wouldn’t do it on the highway. I wouldn’t want to merge onto the interstate in a Model A. But adding another 100 HP, as in my Ranger, is more than enough. I therefore can’t get real exicited about the difference between 137 and 152, for example. Both are more than adequate for a compact car or compact PU. That’s assuming that one has outgrown the hotrodder/boy racer phase of life.
I’ve no objection to people buying more HP, if that’s what they want, but the reality is that most American iron is overpowered, considering the actual use it’s put to.
That said, if something is worth doing, it’s worth doing accurately. HP measures should be accurate.
Nah the ratings don’t mean much to me. I had a 2006 Forester XT with the same engine Johnny….it was rated at 230 HP for 2006 & then was revised to 224 for 2007….it still went like stink so who cares?
I care about truth, or at least as much as existentialism allows. Especially truth in advertising.
In absolute numbers, no, for comparative purposes yes. Unlike the pre 1972 models that used SAE Gross figures, that were more often than not SAE “paper” figures, I would like to see strict adherence to the current SAE Net standard, again, for comparative puposes.
I would also like to see strict adherence to torque standard measurements and probably find that measurement more meaningful, in absolute terms, than horsepower stats since torque is what gets you moving from a standstill and provides low end pull.
I’m reminded of how Rolls-Royce published horsepower ratings up until fairly recently. The normally aspirated engine’s horsepower was advertised as “adequate,” and the turbo’s as “more than adequate.”
I don’t pay too much attention to 25 hp here and there, because as others have stated, there are too many other variables in vehicle weight, gearing, aerodynamics and frontal area. Not to mention that there are variables from engine to engine (as Quentin pointed out earlier from his findings), vehicle maintenance issues (clean air filter, condition of plugs, etc.), ambient temperature and so forth.
So it’s not something I obsess over…to a point, I tend to recall my many previous vehicles in 25 hp increments: my ’84 944 had “around 150 hp” and my ’96 Maxima had “about 200 hp,” but the Corolla I drove in college had “less than 100 hp.” Ah, yes…the Corolla. Drove that thing more aggressively than the highest hp cars I’ve owned, and it kept coming back for more. Of course I was invincible back then…
Detroit-Iron:
Thats all well and good for performance enthusiasts like yourself and myself. However, 90% of the market doesn’t give a rats ass about WHP, BHP, drivetrain loss, etc. All they know is what the marketing gurus put in the adds. Put this way, my girlfriend doesn’t know crap about cars. All she knows is she likes Ferraris more than Lambos, BMWs more than MB, GM more than Ford, and Nissan more than Toyota. She likes fast cars, but has no clue on God’s green earth how they do what they do or why they are fast. One time, I tried to explain (in very simple terms) the difference between whp and crank hp. after about tne minutes, she looked at me and said:
“You mean there is more than one type of horsepower?”
As far as I’m concerned, underrating the cars tends to add to their mystique. This is happening with the GT-R and recently also with the BMW 335i. That’s a good thing.
If the underrating wasn’t already known on every car forum, then you’d basically have the equivalent of a “sleeper” where you’re really pushing 50H more than everyone thinks.
If I spent the money on a Mustang Cobra a few years ago, and discovered that it was down by 30 HP because of casting flash inside the intake manifold, I’d be pissed. On the flip side, if I discovered later that it was actually UNDER-rated by 50HP, then I’d be happy as heck because now my car has that “sleeper” advantage.
Well, I cared about the fact that due to some Canadian suing Hyundai over the 2002 Sonata V6 actually have 170hp instead of 181, Hyundai sent me a “selection of benefits” to choose from – and I chose the 72,000 mile warrantee. So, when the no-start problem kept occurring and was finally pinpointed to the master computer (what would that have cost me? $1000? $1500?) Hyundai put one in for free, at 71,000 miles! The local dealer didn’t give up, finally found the problem, which I appreciated more than the fact that there was a problem in the first place, if that makes sense.
In fact, the car was just as fast when I thought it had 181 hp as it was when it was determined that US/Canadian de-tuned for emissions cars had 170 hp.
The 2002 Sonata was so much better overall than Detroit junque, I decided to go for a 2007 Sonata and it’s been a far better car than virtually any others we’ve ever owned. As have our Prius’s.
This incident has nothing to do with HP in the car. It has to do with integrity of the automaker.
Try as everyone might to slam GM. This speaks of integrity.
Here is a case where GM told Nissan to ,”Grab the Pebble from my Hand, Grasshopper.”
And they showed up with a doctored pebble.
The U.S. has strict guidlelines that the Big 2.8 have to go by. The Imports don’t.
I always figured power ratings were ballpark figures. Manufacturing variability, gasoline variability, temperature/humidity/barometric pressure all play a part, however small, in the power output of an engine. Haven’t you ever gotten a bad tank of gas that just makes your car feel a bit sluggish? Or, you notice the difference when your gas stations switch over from summer to winter gas? What’s really important is that there isn’t so much variation among cars of the same model that I have to test drive 8 different Malibus with the same powertrain, for eg., to find the one that moves the best. As long as any single copy of a given car model is representative of the others, actually driving the car – as opposed to reading about it – will tell me what I need to know.
YES, I am a powertrain engineer. This shit is important. So many people heavily consider the number when purchasing and comparing cars.
HP ratings are not directly measured. Torque curves are measured on the dynamometer (usually an electric brake) over a wide range of RPMs and then HP is mathematically derived. The automaker can choose any HP rating from that derived curve as they see fit for their marketing needs.
If the automakers are selling a small car, then they’ll generally advertise the maximum HP from that curve. If they’re pushing a musclecar, it may not necessarily be in their best interests to publish max HP; rather they may list an accurate HP rating taken from their derived curve at a lower than maximum number at a lower RPM. It’s still accurate from the curve, just not maximum. But then no regulating authority has ever stated that HP ratings have to be advertised as maximum, just accurate. This was sometimes done with late 60s – early 70s musclecars to keep insurance rates lower and therefore avoid scaring away potential customers.
And yes, as an earlier post described, prior to 1972, Gross BHP was the standard. This was when an automaker tested their engines with no accessories, open exhaust, open air intake, and tuned to optimum performance. From 1972 to the present, Net BHP is the standard, as engines are tested with full operating accessories, stock exhaust w/ cats and mufflers and stock air cleaner with filter and cold air hoses. Before and after 1972, engine brake measurements are taken at the flywheel.
All measurements are corrected to standard atmospheric conditions to a barometric pressure setting of 29.92 inches of mercury and 15 degrees Celsius. In the real world, especially on a hot day and a higher elevation, the density altitude will be higher than actual (pilot terminology) and a normally aspirated engine will generate less power than “normal”. On a cold day at sea level (colder than 15 degrees C) and a high barometric pressure (say 30.52″), the same engine will produce more HP than “normal” (at WOT and a high RPM).
I agree that drive wheel HP ratings are the most accurate and reflect real world conditions. As long as every automaker followed the same standards in measuring power, then it would certainly make things easier on the consumer. But because European and Asian companies are allowed to do things their own way…
dastanley. You are dead on. I always wondered how HP is measured. I once read somewhere in this forum that “HP sells cars, Torque wins races”.
I understand the mathematical relation of the two but can someone explain the difference of HP and Torque when it comes to the driving experience?
All I know is a low-end torque motor gives great accleration, pull loads, climbs hills. What does HP do exactly?
Thanks qa. You know, I’ve always been unsure of that myself. My ’94 Ford Explorer with the pushrod 4.0 V6 was limited to a low rpm but had fairly high torque and a short rear end. It pulled great at low rpms, but when I would push it towards redline, it didn’t seem to accelerate much more. At that point it only vibrated and made noise more than anything else. But considering the small air intake opening and the small single exhaust, the intake pressure drop and exhaust back pressure probably had alot to do with that as well.
Apparently, the torque curve for that engine peaked out at a low RPM and then dropped off abruptly (unless I had a maintenance problem with that vehicle). It was rated at 155 BHP (CA version) and I forgot the max rated torque and associated RPM.
One of our work vehicles is a Chevy Suburban that we carry medical equipment around in to get to the airport and hospital, etc. That vehicle, as opposed to the Explorer, seems to have a broad torque curve (power band) as it pulls strongly all the way up from idle to redline.
Perhaps we never even “feel” HP at all. We’re just feeling the torque curve/power band all along and use “Horsepower” as a term because we can relate to it as something tangible in our mind (horses) rather than something arbritrary like “foot-pounds”.
Anyone else know?
qa
Horsepower is a function of torque and rpm. It’s roughly torque * rpm / 5,252 (which means that power and torque are equal at around 5,250 rpm).
Let’s compare two hypothetical engines: a high-revving, DOHC 1.8 L turbocharged four (something like the engine in many VW and Audi products) and a slow-revving, OHV, 4.0 L V6 (something like the engine in older Ford Rangers). Let’s say the four has 180 hp @ 6,000 rpm and 170 lb-ft of torque @ 4,500 rpm, and the V6 has 160 hp @ 4,000 rpm and 220 lb-ft of torque @ 2,400 rpm. Let’s also assume that the turbo four, like many modern turbos, has been tuned to provide most of its torque through a broad rpm range (say, 1,800 to 5,500).
Trundling along around town, turning 2,400 rpm in fourth gear, what do we find? Let’s say the turbo four is producing 95% of its peak torque at this speed, 166 lb-ft. The V6 is at its torque peak at this speed, 220 lb-ft. At this speed, then, the V6 is making about 100 horsepower. The four is producing only about 76 horsepower.
The V6 makes more horsepower up through 4,000 rpm (its power peak). At that speed, its torque has started to drop off a little, but it’s still about 210 lb-ft, and it’s making 160 hp. The turbo four is still making about 166 lb-ft of torque at this speed (thanks to that flat torque curve), and around 126 horsepower.
Now, here’s the trick. Above 4,000 rpm, all of the design elements that give the V6 its strong torque at lower speeds start to work against it (this is mostly a matter of air flow). Its torque starts to drop off rapidly (if it didn’t, its peak horsepower would be higher). The turbo four’s torque is starting to drop off, too, but not as much, and raising its rpm still adds more power than the diminishing torque subtracts. At 6,000 rpm, the four is still making 158 lb-ft of torque, and its peak horsepower, 180 hp. Assuming the V6 can even rev to 6,000 rpm (and it might not be able to), it’s now making less torque and less power than the four. (Even if it’s still producing its peak 160 hp at this speed — unlikely — its torque would have dropped to about 140 lb-ft!)
What does this mean in the real world? If you installed these two engines in otherwise identical vehicles with the same gearing, tires, and overall weight and put them on a drag strip, the V6 would take the four off the line, and stay out in front until a moderate speed — maybe 35-40 mph, depending on the gearing — because at low speeds it has more power. Above that speed, the turbo four would start to pull ahead, and it would win the race with a noticeably higher trap speed.
The peak value for torque, as you may have gathered, is not that useful unless you also have a sense of the engine’s torque curve — how much torque it puts out at different engine speeds. Ideally, you want an engine that produces most of its maximum torque at all engine speeds (a very flat torque curve), but with internal combustion engines, you can only approximate that.
dastanley:
You are exactly right (and it’s funny that I just used the Ford 4.0L engine as a point of comparison). The Ranger/Explorer 4.0L V6 was tuned for strong low-end torque — its torque peak was only 2,400 rpm — but it was all done above about 4,500 rpm. There (probably) wasn’t anything wrong with it, it was just designed that way.
Why? To a large extent, all of the things that benefit power at low speeds will restrict it at higher speeds, and vice versa. Blame it on Bernoulli’s Principle. An engine set up for high-rpm power (with short intake runners, big valves, high valve lift and long duration) will tend to hurt low-rpm grunt because all of those elements reduce intake velocity at lower speeds. An engine set up to produce high intake velocities at low speeds (long, narrow intake runners, small valves, low lift, short duration) is too restrictive at higher speeds — at high rpm, the engine can’t get enough air.
Modern engines can cheat to some extent with variable valve timing, variable intake runners, and other tricks, but any engine design is still basically a compromise — it works best in one particular speed range, not as well at others.
Torque answers the question “Can it happen?” Horsepower answers the question, “How fast will it happen?”
I suppose a better question would be
Do you care about horsepower ratings?
My answer would be no.
argentla – thanks so much for taking the time to answer my question. Makes things much clearer.
Following your example then, if the V6 were tuned to deliver peak torque of 220 ft-lbs at 4,295 RPM with similar curve characteristics (using multi-ports and variable valve lift) as the Turbo Four, they would perform about the same on the drag strip correct?
argentla – If your 160Hp V6 were coupled to a transmission that keeps it spinning at its torque curve 2,400-4,000 rpm, it should outrun the I4 turbo. Yes? Again exactly identical cars with equal weights.
I think modern HP ratings are too often taken out of context by advertising departments. They fail to mention how heavy the vehicle is, what RPM the HP is reached at, and what the cruising RPM is b/c the HP or max torque is at the wrong RPM.
A good example is my 9 year old CR-V. It has an advertised 146 HP and I feel confident that it has it all but the driver has to run the engine right up the red line to get it. Max Torque is close to the highway engine speeds but the torque feels low compared to alot of other cars I’ve driven. That said we’ve been quite satisfied with it for 162K miles now though a sixth gear for it’s five speed manual tranny would have been welcome. Use that sixth gear to drop the rpms another 350-450 rpm. Leave the other gears where they are now.
I numbers I am interested in are:
rpm of max hp
rpm of max torque
hp per lb
vehicle weight (to which I’d add the weight of our family, a full tank of gasoline, and a full load of luggage).
# Dynamic88 : The Model A perspective –
Recently a friend gave me a ride around town in his Ford Model A – 1931 Vintage. He said the engine made 37 horsepower. Most published figures I’ve seen rate it at 40. I’m not going to quibble. What impressed me is that for the most part, the A is quite capable of keeping up with city traffic. Sure, starting off from a stop is a bit slow – you can’t shift real fast, you need to hesitate a bit or it’ll grind. But as far as HP goes, 40 is all that is needed for city driving.
Yeah I like Model-As. I want to own one someday.
I owned and drove a 40HP Super Beetle (~2000 lbs) for several years in Italy. It was my daily driver. It was fine for 80% of my needs. It was too slow on the steep mountain roads though. 3rd gear all the way up if I was carrying three or four people. A proper five speed would have prob fixed that – same low gear and same high gear with more gears in between. I drove it from the northern Italian border to Sicily a few times and even out on the autostrada it was fine up to about 70 mph. A higher gear would have been nice but with four speeds there wasn’t enough torque to take advantage of it. We experimented with that. My roomate’s US Spec Beetle had the 3.88 gearbox that the Karmann-Ghias came with and 40 HP wasn’t enough umph paired with that gearbox. The 65 HP engine could do something with it however. The higher gear was nicer on the open highway though.
The “perfect” power to weight ratio for me was my ’84 Rabbit ‘vert. 90HP from 1800cc and still relatively lightweight (~2300 lbs). 120 mph top end and plenty of power for around town.
My ideal target HP to weight is around 100HP with a 2300 lb vehicle and five or six manually selected gears. If I could do it with a 1.4L then I’d be satisfied. Instead of making each generation of vehicle heavier, make each generation the same power and with the same weight and let the fuel mileage increase through tech advancement.