The "Golden" Power/Weight Ratio

The recent “Most Overhyped/Underwhelmed Car” and “Unexpectedly Exceeded Expectations Car” threads have gotten my mind twisted around trying to figure out if there is an optimal (“golden”) power to weight ratio that makes for a fun to drive car. (As well I have been trying to find if anyone has compared a FR-S/BRZ to a 944 for some reason they seemed to be competitors to me)

I realize there is much more to a fun car than just how many pounds of weight that each horsepower is responsible for (ex: suspension, weight distribution, brakes, tires, torque / power curve, driver ergonomics and interface, etc). The numbers can be gamed as well by overcompensating horsepower in an overweight vehicle and vice versa stripping every possible ounce of weight from a mediocre powered car. Or in the case of drag racing cram as much possible power into any vehicle (everyone had a different idea of fun)

So looking at the HP/LBS ratio of stock vehicles (as provided by the internet: R&T, Wikipedia, Edmunds, etc), I put together the below chart in an effort to see how cars that are generally perceived as “Fun to Drive” compared. If there is a car that’s missing definitely let me know and I can add it to the mix!

Since curb weights often vary between sources I used the lowest or most often quoted number and then rounded. Horsepower (which is often quoted everywhere) was from the specific vehicle model. While these values aren’t cited (that’s too much work to track) please feel free to correct if something is glaringly wrong.

Anyway the data is below. So is there a “Golden Power to Weight Ratio”? Just enough power and the right amount of weight to make a fun to drive car... I would love to hear everyone’s thoughts!

Its not the power, its the delivery.

Not to detract, but I'll point out that this is Weight/Power not Power/Weight.

Looking at the list (which is basically a list of fun cars to begin with), I'd say the weight/power ratio makes little difference on the fun factor in my experience. I've driven 8 of the cars on this table in anger, and out of them I've probably had the most fun driving the NB Miata and SW21 (I've driven the SW22 also and prefer the SW21) with the S2000 being pretty close. Based on that, I'd have to say the weight to power ratio isn't that big of a factor. In fact, I'd say it's much more about the weight and much less to do with power.

I've driven a 500+ hp STS-V, C6 Z06, 400+ hp GC8 Impreza, but never had that really amazing connection to the car like in an NB, SW21 or an S2000, which is what makes it really fun for me. Those cars have fairly modest weight/power ratios but are pretty light.

The one outlier might be a locost kit car, which probably had a great ratio and was a lot of fun. It follows the low weight=fun rule too though.

This doesn't hold true all the time though, since I don't tend to like the NA or AW11 chassis cars as much as their successors.

I don't think the golden rule for making a car fun is a power/weight ratio. It's about competence vs. visceral involvement.

You should be able to hit about 6/10-8/10 of the cars performance on the street if you push it a bit, but don't get too dangerous. So, a car with low performance, you'll get to it's limits before the car starts to engage you. If it performs too competently, it won't thrill you until you're going hazardously fast.

What makes a car more fun is a more direct involvement to the road. Manual transmission and good steering feedback add a lot to involvement. Low weight adds to involvement because things are just more immediate. Bonus points for roadsters because there is just less between you and the environment.

So, this is why a Miata will be more thrilling than a Z06. There is just less between you and the road. The total performance limits are lower, so you can really flog it and keep it at about 7/10 on nice twisties. You know you're approaching the limits of it's performance, but there is enough performance buffer to never fall on its face or leave you without maneuvering ability if something unexpected happens. The Z06 is so competent, you will never hit 7/10 on the street without criminally dangerous stupidity being involved. A Locost is a winner because, even though it will outperform the Miata, there is less between you and the road, so you're more involved.

Edit: Extra bonus points for other giggle-inducing gee-whiz factors. Corvettes sound awesome. I also love the stratospheric redline of my AP1 S2000 and SWMBO's RX-8. I can pull out onto the road and run up to the top of 2nd, and just be in a giggle fit as soon as I pass 6,500 in 1st.

Too much HP is just enough.

Kenny_McCormic wrote: Its not the power, its the delivery.

It's not the power, it's the container.

I've driven boring 5lb/hp cars and extremely fun 30-35lb/hp cars.

Grtechguy wrote: Too much HP is just enough.

until you get used to it, then you'll want a little more.

Beer Baron wrote: You should be able to hit about 6/10-8/10 of the cars performance on the street if you push it a bit, but don't get too dangerous.

That's part of the fun of a low performance car. You need to approach the limits of cornering, and run hard against the limit of acceleration and top speed, just to keep up with traffic.

Coming home from a class in the Quantum earlier this year. Was being followed by a co-worker. There was an interesting downhill/uphill left-hander in an interchange that I like to rail around. The next day, co-worker asks why I slowed down. Pointed out that at no time did I release the throttle from its carpet-crushing maximum, it was just the cornering forces that pulled 10mph out of the car's speed...

It's also fascinating in seeing how different lines affect exit speed through that corner. Entry speed is always the same because the car tops out so low, and exit speed is entirely due to how much momentum you scrubbed off through a poor line.

Anything better than 20:1 is something I can live with. The car's I've been in that have 10:1 or better are all really fun.

Mark Donohue said it best ....

"If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough horsepower."

I used to 4 wheel drift a manny tranny Mercedes 240D around traffic circles. ~3600 lb with driver and fuel, 68 advertised HP. So what's that, like 53 lbs per HP?

Of course, it would have been MUCH more entertaining with a small pushrod V8 up front...

wbjones wrote: Mark Donohue said it best .... "If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough horsepower."

I am going to steal that quote.

I don't think the weight:power number is the defining characteristic, although it is a factor. Anything under 10:1 is fun from a purely 'holy crap' acceleration point of view, but may not be a great drivers car.

Maybe you should throw some other cars in that are generally agreed to miss the mark. Where do the 350/370Z, the SS Camaro, the Challenger SRT, the Camry, and a late-model full size pickup fall? If you're investigating a phenomenon, you need to test both sides of the equation

FWIW I find that I really like a car to be slightly more competant at acceleration than it is at handling - it gives you a car that's a little bit of a handful to drive hard - and I find that fun. Did I mention I drive a Mustang?

Thanks for the responses so far, I updated the sheet to include the Camaro, Mustang and Challenger as well as the recent Z cars and Wranglers just to see what that looks like. A bit surprised at both how much the muscle cars and jeeps weigh and how the 400+hp really brings down the weight per each hp

I agree with the comments that fun cant simply be boiled down to a single metric and there are many different factors (gearing, driver interaction, where/how power is made, etc)

Concerning there's never enough HP, I think its fun in the right situation but often its too much or you're left yearning for more, never satisfied and therefore no longer having fun.

Slow/low power car being pushed fast can be fun too but at a certain point you cant always be pushing it and it has to feel like its just dragging on.

Quick side not concerning the cars that surprisingly exceeded expectations. I'm surprised so many people like the V6 4th Gen F-bodies. I'll probably have to add that in !

FWIW, Mark's actual quote from The Unfair Advantage is (speaking to Porsche engineers about the 917-30 Can-Am car): "it will never have enough power until I can spin the wheels at the end of the straightaway in high gear." Another variation from the book is (after increasing power to 1190 bhp): Porsche engineers: "Now does it have enough?" to which mark replied "I still can't spin the wheels all the way down the straightaway."

We tend to remember Mark as the cool, engineer-driver, but he was a DRIVER, and a RACER, one of the best ever.

This is going to vary wildly per person.

If i HAD to attach a number to it (even though i don't think a number defines it), i'd have to look at my own stable, and the one that entertains me the most is the MX6. I don't REALLY think that a 6.3lb/hp ratio is required for me to have fun, but it can certainly help.

Numbers are based on WHP, not crank/fly numbers.

2004 Mazdaspeed Miata: 9.3
1990 MX6 GT: 6.3 (Estimated)
1993 Escort GT: 6.5 (Estimated upon insertion of new motor)
1993 Miata: 5. (That's the minimum goal.)

Looking at these numbers... i'm starting to fear for my life, now...

I would think something close to 1:1 would be just fine.

IMO, things that are fun to autocross are fun to drive.

Andy Hollis has posted a pretty simple formula for this before. Its something to the effect of (Power/Weight + (Tirewidth/weight) x 2) x (drivetrain layout modifier). I think its probably more advanced than that - power/weight is probably averaged over 10mph-60mph before factored into the previous equation.

The correct amount of grip is infinity.

The correct amount of power is enough to overwhelm grip at any speed.

It's a factor of power-to-weight, but I mentally class street cars in terms of 0-60 times:

7.x seconds = fun
6.x seconds = quick
5.x seconds = fast
4.x seconds = damn fast
sub-4 seconds = supercar

I don't find cars that are slower than 8 sec. to 60 to be particularly entertaining to drive until I try to see how fhard I can pitch them into corners.

Beer Baron wrote: You should be able to hit about 6/10-8/10 of the cars performance on the street if you push it a bit, but don't get too dangerous. So, a car with low performance, you'll get to it's limits before the car starts to engage you. If it performs too competently, it won't thrill you until you're going hazardously fast.

I agree with this as well and it was one of the big reasons why the other half sold her M3 a year or so after buying her MCS in 2003. The MINI was simply so much more engaging and fun to drive, she had to literally force herself to drive the BMW to work every couple of weeks. Well, that and it seemed like every-other time she drove the M3 one of fault lights would come on...

My analogy has always been: screw up in the MCS - oops... understeered a bit... screw up in the M3 - they're picking your bits out of a tree... (keeping in mind, her cars are soley for street driving - no interest in autox or track events).

As far as the "magic" lb/hp? It seems 10lb/hp has been a nice, round number for some time.

While the Fiero V6 has a worse power to weight ratio vs. the 944, I never lost to one in several years of autocrossing. The 944 handles well, but feels slow.

There is a tipping point at least for street cars.

My Shelby had a 2.75/1 lb/hp ration and was UN-drivable on the best days and actively trying to kill me on the worst.

My current viper is I think 5.15/1 give or take, easy to drive around town but still not a lot of fun because you can go maybe 2/10th before you are breaking every law in the book. I think I can double the freeway speed out here in second gear sub 7 seconds.

S2000 don;t know the ration off hand was a ton of fun and if I had to guess around 12 lb/hp and that was perfect.

I'm perfectly happy with the 12.1 of my Focus. and if I want more I can always clean out the trunk and get 11.6.

I still tend to equate the power/weight ratio with driving my Fox body Saleen.

225hp/3200lbs (roughly) = cool...but could've used 3:55's instead of the 3:08's.

Now, I think that the new Morgan 3 wheeler with the S&S engine would totally make me forget about the ratio...and concentrate on having some fun.