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Comparison of Power

Hey there guys, fresh-faced new user here!

Thanks to an archived discussion on this site, I now know what it means when a car is described as having ‘X horsepower at Y RPM.’

So, specifically in comparing my '96 BMW 3-series with a '97 Honda Prelude I am thinking about getting:
The BMW has 190 HP @ 5300 RPM, while the Honda has 195 HP @ 7000 RPM.
How do I gauge which car is more powerful overall? Pushing the revs to the limit in a drag-type situation, I imagine the Honda would win out eventually.

Even though the BMW is practically falling apart at 235k miles, I couldn’t bring myself to replace it with a less powerful car. Just wouldn’t feel right.

HP ratings are just one of a dozen variables that affect how ‘powerful’ a car feels, which is different from how ‘fast’ it is, which is different from how ‘quick’ it is. So toss out the spec sheet and buy what you like.

Amen to Texase’s comment.

Besides, you’re considering replacing a 16 year old car with a 15 year old car and you’re worried about 5 HP published difference…at different RPMs?

The rating is how much horsepower the engine develops at a specific engine speed. Since your engine will vary from about 1200 RPM to between 5300 to 7000 or more RPM (depending on the car), it isn’t very useful. I’d drive them both and decide if the Prelude drives well enough to replace the Bimmer. Oh, and torque is another indicator of power that you missed. But still, drive them.

Remember, people buy horsepower, but they drive torque. Torque is far more important to the driving experience than horsepower.

I agree with the others. Drive the car and buy it if you like the way it drives. If you don’t like it, find something you do like.

Going from your RWD BMW to a FWD Honda will make more of a difference than a few HP. Power is only one measure – handling and braking are just as important. FWD won’t “feel right” more so than 5 HP.

You’re talking about 15 and 16 year old cars. Is this really worth it?

The fact that they have roughly the same horsepower but the BMW has it 1700 RPM sooner would lead me to believe that the BMW has more torque and might be quicker when driven sedately. A lot of factors come into play here: Vehicle weight, gearing, the whole horsepower vs. torque thing…I’ve driven cars that have unimpressive spec sheets but pretty good zip, and I’ve driven cars that look good on paper but feel sluggish. Some drivelines are just more efficient than others.

Let me add to the excellent comments that, maximum horse power at different rpms matter little in this day of variable valve timing and computer controlled combustion. Let me see the entire power curve. It really doesn’t matter how much occurs at what peak rpm as it does along the entire rpm range. That is one of the distinct advantages of newer motors. The better motors are less restricted around their peak.

Everyone can personally attest to different cars they have owned whose maximum horsepower and perhaps torque as well compare equally on paper. But, drivability is more dependent upon the performance of an internal ombustion motor being closer to the ultimate goal, the performance of an electric motor.

Thanks for all the comments, folks! Lots of helpful things to think about.

Regarding the “replacing a 16 year old with a 15 year old” thing: It may seem not that great, but money is the big issue here. The BMW is worth about 2000 as a dealer trade-in, and the Prelude owner is asking for less than 3000. The BMW needs completely new suspension, the tension straps in the roof are shot, it keeps throwing an O2 sensor code even though we just replaced them and the cats which means there’s something wrong with the electrics, the driver-side door usually will not lock (and if the window’s up it sets off the alarm), and a baker’s dozen other minor things. About the only thing that still works is the engine, and thankfully it still works really, really well. The Prelude is in excellent condition and has a full 100,000 fewer miles on it.

So no, it’s not a significant upgrade, but chances are I’ll get more future miles out of the Prelude than the Bimmer at this point.

In terms of torque, the BMW has a full 50 ft-lbs on the Prelude, and at more than 1000 RPM sooner. However it’s 320 lbs heavier. And yeah, the RWD is awesome.

Anyway, thanks again for all the helpful comments!

Performance, response, handling, comfort, reliability, even personal preference can make or break a car’s acceptance for each of us. Do the horsepower numbers mean a lot to you?

According to some stats, the Prelude is about one tenth of a second faster than the Bimmer from 0-60, and one tenth of a second faster in a quarter mile.

While fwd, the Prelude of that era was selected as ‘best handling car under $20k’ by Car and Driver, IIRC.

@ Rod Knox

More than a little, less than a lot. I do a lot of highway driving; I like being able to merge at full speed, overtake slowpokes with little effort. and not have to slow down to climb hills. I like accelerating. I don’t really do performance driving, and I don’t think I really have room for it in my life, other than driving through some scenic winding roads on my way home from university. Those are usually clogged up by slowbros anyway, preventing me from really challenging the curves.

In other words, I desire decent handling, but I value accelerating power more highly.

The “seat of the pants” power is what really matters. Drive any potential new car in conditions similar to your usual commute and see how it suits you. Your perception is much more important than the isolated figure from some chart. Did someone already say that? This question has been knocked around here several times.

The Prelude will have different gearing and likely will be running about 800+ rpm higher in top gear at 70 mph. It will still get better mpg than the BMW and similar top speed due to the higher redline on the motor. Honda’s switches and basic systems (power windows and seats, etc.) tend to hold up with much fewer problems than a similar aged BMW.

The Prelude should be as much fun to drive. Most of the stuff in the car will work. And it will need less repairs over the next 5 -10 years. I’d say go for the trade.

I think that you’re putting to much reliance into charts which may or may not be indicative of real world figures. Odds are if both cars were put on a dyno one would find that neither are producing anywhere near what is claimed.

You’re also talking about figures at RPMs which the majority of people never reach during normal driving.

holding up sign [never let go of sweet cars]

Yeah, the extra 50 ft-lbs is going to be significant. You’re probably going to think the Prelude is slow as hell at first, because most people do when moving to a 90’s-era Honda for the first time. They’re used to developing their power much lower on the tachometer, and get uncomfortable revving to the 7500RPM redline, which means they miss out on the peak power of the engine.

1997 was a good year for the Prelude, and it’s a hell of a fun car, but I wouldn’t put it up against your BMW as far as driving experience goes. Reliability-wise, on the other hand, if it’s been taken decent care of, it will cost you a LOT less money than the BMW would.

Of course, all of the assumptive comparisons are constrained by our remembering the car when it was new. Before considering any swap be sure to get the replacement vehicle checked out thoroughly (including a compression test) and test drive it thoroughly. A cars performance and character can change dramatically over the years depending on how it’s treated and maintained.

Sincere best.