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Where's that horespower going?

10/12/2006 9:04 AM

I just test drove a car last night and it got me thinking...

Over the last 20 years 4-cylinder engines have been grown impressively in horse power, often exceeding 150 hp without turbo charging. Why is it that the first two cars I owned; a 78 Saab EMS with 115 hp (4 speed) and an 85 VW Jetta with 85 hp (5 speed) seemed every bit as lively as current models with 50 percent more power? Is it weight? Torque? Gearing? Emissions equipment?

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#1

Re: Where's that horespower going?

10/12/2006 9:24 AM

Look up the curb weight of those older vehicles and calculate the power to weight ratio. Compare that number with the same calculation of today's car. Today's cars are a bit of a porker, eh?

I would not be surprised if the gear ratios have something to do with it too. Again, you can do the research and get the answer.

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#2

Re: Where's that horespower going?

10/12/2006 9:57 AM

In addition to the power to weight ratio two other large contributors are also fuel/oxygen control systems and emission systems.

Older and, in my opinion - superior, cars were tuned for performance with less of a regard for fuel efficiency. Additionally, they were more easily adjustable by the owner to run richer or leaner, as preferred... how I long for the days where I could "tune-up" my own car with a screwdriver and a wrench to run the way I wanted it. But, the drawback was being able to actually watch your fuel gage when the other two barrels kicked in Now I need to hook up my computer and change the shift points, the oxygen intake values, etc. Making sure to not forget and change them back to the factory defaults before I take it in for any needed service

As for emissions, a minor contributor, but one none the less... the more crap you put on the exhaust pipe the more back pressure the engine sees and the less efficient it is. My '05 F-150's air in-take and exhaust has just been redone and I've gained noticeable improvement in getty-up... plus it sounds a whole hell of a lot meaner.

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#3

Re: Where's that horespower going?

10/12/2006 10:58 PM

You will find that post number 2 hits the nail on the head. Cars have progressively packed in more features, and with them weight. So you will find that the additional power gained from improved engines is used in motivating all that extra bulk around. Having said that, even though one might think that a lighter car will handle relatively better than a heavier car, advances in suspension componentry, and structural rigidity have seen cars improve in this respect. Increasing pressure to make cars more fuel efficient has influenced car makers to install cars with higher gearing. Sportier versions of mainstream cars tend to have gearboxes with shorter ratios, differentials with lower ratios, or both. If you pick up a car mag, you will notice that when reviewing a newly released car, attention is paid to the weight increase, if any, and how the manufacturer compensated for this, if at all. The usual fix is more power, but occasionally a shorter final drive ratio is selected.

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Anonymous Poster
#4

Re: Where's that horespower going?

10/13/2006 12:49 AM

You need to also realize that the HP figures on auto ads are more often the creation of the marketing departments than the engineering departments. I'm not saying that advertisers would lie but in years past it was common practise to rate engine hp based on the engine performance on an engine dyno and not as installed... Are mfrrs more "honest" now????

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#11
In reply to #4

Re: Where's that horespower going?

10/13/2006 11:50 AM

Manufacturers are actually much better now re HP reporting: The figures are measured consistently from manufacturer to manufacturer, much unlike the old days. SAE net figures are used to better represent an engine with an actual exhaust system, turning a water pump and alternator, etc. In the mid and late sixties, HP was routinely overstated, and speedometers were always optimistic.

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Anonymous Poster
#5

Re: Where's that horespower going?

10/13/2006 3:20 AM

Although all the comments about weight, emissions etc are surely true, I think the real explanation is down to the the number of valves. The older engines were generally two valves per cylinder producing a decent amount of torque at low revs. The new units are invariably multivalve, which combined with all the emission strangulation reduces the torque levs at low revs. However they can run to much higher rpm. Power = torque x speed ( revs ) so 150 bhp @ 8000 revs sounds more, but in normal driving it's the torque that counts.

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#6
In reply to #5

Re: Where's that horespower going?

10/13/2006 6:15 AM

I've been building engines for over 20 years and every thing has improved, from combustion chambers, piston design, materials, induction systems and control systems. Everything goes to make the engine more efficient, and the more efficient an engine is the more power you get. By efficiency I mean the ability to burn the maximum amount of fuel in the combustion chamber, and to exploit ALL the power possible. Race engines cheat by having an overlap in the valve timing that allows un-burnt fuel mixture to force out as much combustion product as possible, allowing more fuel in (scavenging). Don't use this on the road as un-burnt fuel then ignites in the exhaust system! I've found that given the similarity of multi-valve engine design these days, one of the biggest factors that reduce power is friction loss. Some designs, such as Honda, have tremendous lubrication systems that allow for imaginative bearing design!

But in answer to your question, power to weight ratio rules…

P.S. My track day car is a 30 year old Ford, and I embarrass modern car drivers frequently.

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#7

Re: Where's that horespower going?

10/13/2006 7:33 AM

One other thing to bear in mind is that this is your "perception" and as we all know perception can be very different from reality. An example I owned a '92 Olds Achieva that was rated at 180 HP @ 6200 RPM (160 @ 5200 Ft./Lbs of torque) and was a DOHC motor. That car felt faster then my 99 Pontiac Grand Prix GTP which has 240 HP @ 3400 (or so) (280 Ft./Lbs @ 2800) and is a Supercharged OHV motor. How can this be? Well it may have felt faster but it was really no where near as fast. Magazine quarter mile times for the Achieva were around 15.4 seconds or so. I never raced the Achieva but I'm sure mine was not significantly faster. I have raced the Grand Prix and my best time with that is 13.9 in the quarter so obviously the Grand Prix is actually much faster. What I took out of that is that seat of the pants feel is not a good measure of the power of a car. I think that the reason the Achieva "feels" faster is that the Grand Prix makes consistent power across the rev band where the Achieva had a noticeable spike around 5K RPM's which almost made it feel like it was a turbocharged car. So with one it's a fairly steady push back in the seat with the other it was varied and I think therefore more noticeabe and interpreted as speed.

1/4 mile times and 0-60 times have been decreasing stedily for quite a while. Cars that were considered fast cars in the late 80's (LT-1 Camaros) are slower then new V-6 Accords, so while cars may not feel like that have extra horsepower they certainly do.

Shawn

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#12
In reply to #7

Re: Where's that horespower going?

10/13/2006 11:59 AM

Well put: The original GTO from the sixties, with it's 389 cu in engine had quarter mile times about the same as your current GTP. The old GTO was heavier, had slipperier tires, and marketing-department-derived HP figures. Put the two cars on a road course (where you'd have to use brakes and handling) and the difference would be even greater.

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Anonymous Poster
#8

Re: Where's that horespower going?

10/13/2006 9:24 AM

Actually, the horsepower rating is raw (engine only). What your actually getting after Transmission gearing, rearend (or just transmission if it's front wheel), tiresize is rear wheel horsepower (or front wheel for the front wheel drives). What your getting at the wheels may be about the same even though engine hp may be different. One factor that is changed is the fact that most of todays cars are geared for higher speed driving which mean higher gear ratios in the transmission which is a reason for increasing engine horsepower and torque.

That will be $.02 please :D

_Lloyd_

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#10
In reply to #8

Re: Where's that horespower going?

10/13/2006 10:10 AM

That's one thing I didn't originally metion - The Saab could maybe hit 100; the fastest I think I personally went was 80 -85. I think 85 was the top speed of the Jetta before it just couldn't overcome resistance and drag...

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Anonymous Poster
#9

Re: Where's that horespower going?

10/13/2006 10:00 AM

Oh yeah, not to mention the "feel" differences due to how the vehicle transfers weight.

$.00 that one is free

_Lloyd_

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#13

Re: Where's that horespower going?

10/13/2006 12:54 PM

In ordinary driving, cars use a fraction of the available horsepower. Generally, at 60 mph the figure is about 15 hp, or even less for an aerodynamically efficient car. HP required goes up roughly with the cube of speed, plus a little. (Aero drag goes up with the square, so if you double speed you need four times the tractive effort at the wheels. Having doubled the speed, the four times greater torque has to be delivered twice as fast, so you're using 8 times the HP. Rolling resistance, mechanical losses, etc are a small part of the total at highway speeds and above.) Therefore, using a lot of the available HP requires going fast -- something which modern cars a very adept at doing. My run-of-the-mill four cylinder Accord has 160 hp and is electronically limited to 130 mph. (Without the limiter, it would only do another mph or two faster.) My first Accord (1976) had 76 HP, and could not top 100.

Being able to go fast (and keeping emissions and fuel usage low) also means that the gearing is tall, so at highway speeds, rear wheel torque is lower than it would be with a modern engine but the gearing of older small cars. My old Accord with its old gearing (and much lower weight) and my new engine would be a rocket up to it's lower top speed.

The other thing that enters in, aside from the physics, is perception. I thought my 40 HP VW of many years ago was adequate. My "peppy" Triumph TR4 sports car of around the same time could be blown into the weeds by a Honda Civic econcar of today, in every respect: acceleration, cornering, braking, and top speed. My first Honda Accord performed well in every respect. But my current Accord does everything better. (With the exception of fuel economy)

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#14

Re: Where's that horespower going?

10/13/2006 1:33 PM

Nobody that owns a modern sport motorcycle will ask that question. Every year without fail the weights go down and the ponies go up. Remember the bikes of the 70's and 80's? Man those RZs, Gammas and Nortons etc. were fast! But were they really? They felt fast because the tires and suspension wern't up to the power they put out. Get on a new CBR600RR or a Ducati 999R and hang on! Thats power and handling that match.

I think a lot of it is nostalgia or at least the fact that back then we were young, less wealthy and so, bought used cars. I had a few sports cars back in the day and they were all purchased used. I remember them as being fast, but my 2005 Ford F150, as heavy and full of bells and whistles as it is, would out perform them.

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