power to weight ?

Could anyone tell me the ratio for power to weight with a 1,500 lbs car and a 145 hp engine?

I've seen the automatic calculators, but the results don't make sense and don't match up with the posted figures for other cars.

Wondering if a 145 hp, 1,500 lbs car would make for something fun and fast?

Thanks a lot !

TC

That's Miata NB type power and 800 pounds lighter. That should be lots of fun. Almost 200 HP per ton.

Ugh... okay...

Power to weight Power = 145 hp Weight = 1500 lbs

145 / 1500 is your power to weight ratio, though no one states it that way. It's always lbs per hp, or in this case, 1500 / 145. For simplicity sake, lets assume your engine is perky and producing 150 hp, hence, your "power to weight" is 10 lbs/hp. Pretty good but not great.

Or, as said above, someone decided it has to be "hp / ton", so in that case it would be (2000 / 1500) * 145 hp, or 193 hp/ton

Now if you have 400+ hp and 1600 lbs, THEN you're talking... like the car in my sig :P

1500/145=10.34 pounds per HP.

A Corvette is about 6.2:1

A Miata is in the 20:1 range.

And don't forget that when figuring out this number, everyone lies and pretends that the car is racing itself, with no driver and likely no gas nor coolant. The light weight provides for impressive imaginary results.

Your "10 lbs per hp" is likely more like 12.4 lbs in the real world.

Power to weight is expressed either in units of "hp/lb" or "lb/hp", depending on how small the ratio winds up (if its real small in hp/lb, use lb/hp, and vise versa). For the numbers you provided, you'd have 145hp/1500lb or .097hp/lb, OR 1500lb/145hp or 10.34lb/hp.

According to wiki, that puts you a little ahead of a stock S2000, a little behind a Lotus Elise SC.

Toyman01 wrote: 1500/145=10.34 pounds per HP. A Corvette is about 6.2:1 A Miata is in the 20:1 range.

Depends on the Miata Mine's at about 4.3.

1500 lbs and 145 hp is definitely a lot of fun.

Keith Tanner wrote: 1500 lbs and 145 hp is definitely a lot of fun.

My Firefly turbo is in that territory. It is a lot of fun.

The Abomination is probably pretty close to that as well. It would qualify as fun.

The Samurai is in the 27:1 range. It makes molasses look like a speed demon.

Thanks guys ! ! !

As a comparison for APPROXIMATELY what the resulting performance might be like (acceleration/driving NOT handling) could anyone/someone post a few examples of cars with a 10-to-1 power to weight ratio?

I think that I might be able to pull another couple of hundred pounds out of the car just to make room for me in the equation.

Any help would be terrific. Just to keep my enthusiasm up there through the Winter, you know?

Thanks!

1500 lbs and 145 hp is definitely a lot of fun.

Truth!!!

How about a video of the Abomination.

https://www.youtube.com/watch?v=ggaD4nC8wec

The Manic Miata runs about 10 lbs/rwhp. It's not scary fast, but it is plenty entertaining.

My Locost is about 120hp and 1440lbs with me in it. It is a LOT of fun, but now that I am used to it, I could be quite happy with 200hp. Until I get used to that.

Keith Tanner wrote:

Toyman01 wrote: 1500/145=10.34 pounds per HP. A Corvette is about 6.2:1 A Miata is in the 20:1 range.

Depends on the Miata Mine's at about 4.3. 1500 lbs and 145 hp is definitely a lot of fun.

4.3!!!!!

That is better then my last modified viper. That has got to be one very brisk Miata.

wearymicrobe wrote:

Keith Tanner wrote:

Toyman01 wrote: A Miata is in the 20:1 range.

Mine's at about 4.3.

4.3!!!!! That is better then my last modified viper.

Naked raccoon > snake

arrgh, typed up a long reply with lists of hp/lb rates of cars last night and then lost it

You should be pretty close to a c5 vette category, which for "normal" people is very fast. You have a pretty skewed group giving answers here.

Toyman - what is the abomination? from the video I'm guessing some old british something with a v8?

my toy is at 1650 with me in it and should be around 220 hp or so. It's way faster than i need especially with my bad driving and crazy heavy rear end.

I guess my P71 with the 5.4 swap weighs about 4000 lbs and makes around 275-ish hp. Lots of fun to throw around. I think it's mainly the torque though. Prolly around 350 ft lbs if I were to guess. Never dyno'd it with the new engine. The old 4.6 made 190hp at the tires on the dyno we had at the old shop, and the 5.4 is a VAST improvement. That puts me at 14.55 lbs per hp.

OP, what kind of car is it that at 1500 lbs you can potentially remove a couple hundred more?!? That's CRAZY light.

Toyman01 wrote: A C6 Corvette Z06 without driver is about 6.2:1

FTFY

Advertised "curb weight" does include all fluids and a full tank of fuel, but most people neglect driver weight when talking power to weight ratio. This can be a significant oversight, since 200 lb added to a 1500 lb car changes the power to weight ratio by appreciably more than 200 lb added to a 3500 lb car...But at the same time, most drivers are also obviously not of the same weight either.

Just to confuse the matter further, while factory advertised hp is always at the crank, when discussing aftermarket modified cars people are also too often not clear whether they are talking about 'wheel' or 'crank' hp...Which can have a pretty dramatic impact on the results as well.

FYI, my numbers were a wet weight (without driver) and an advertised crank rating for my engine.

I also am interested in a 1500 lb car that could lose a couple of hundred pounds. That's a pretty significant difference.

My scratch built bike engine car was 150+ hp and about 1200lbs on track and it was fun for sure,not mind blowing in any stretch.Tq from a small turbo set-up combined with the close ratio bike gearbox and I'm sure it would be just about the right balance of power to weight.

Here's a comparison: My 1994 C4 Vette is rated at 300 hp and 3300 lbs, for a wt/pwr ratio of 11.0. Motor Trend road tests of that year list 0-60 in 4.9 sec, quarter mile in around 13.6@107 mph (working from memory here), and those usually are pretty well tied to wt/power. Top speed isn't, because gearing, aero, etc enter into the picture heavily over 100 mph. So I'd guess that your car will do 0 - 60 somewhere around 4.5 - 5.0 sec, depending on how well it comes off the line. I believe Keith's Locost is around that wt/power (or used to be, I think it's faster now), so Keith, does this sound about right?

Something I put together and posted a few months ago:

The Locost is about 1250 lbs (wet, no driver) and 175 flywheel. When C&D tested it, they got 4.7 for 0-60 and a 13.8 at 97 mph in the quarter. The car was suffering incredibly from drag in the latter test, I've seen the data and it took about as long to get from 80-95 as it took to go from 0-80. I could have taken a lot of time off by simply unbolting the windshield, but we tested it in road form.

Which illustrates a big difference between a high power car and a light car with the same power/weight. The feeling of a big engine simply shrugging off drag is hard to beat, although the light car has those brakes and those reflexes. I love the way the high power Miata hits hard when I slot into 4th gear. My Locost might not have been the fastest car to 60 mph, but it beat every production car out there at the time with a 141' 70-0 distance.

If you're running on small tracks, the street or autox, 1500 lbs and 145 hp will be quite entertaining.