General auto horsepower question

[axxeman01]

Greetings,

My car is getting a bit long in the tooth, and while I'm at least a year out from making a purchase, I want to get an idea of what I need to look for. I mean the raw numbers, I want something that is at a minimum as quick and fast as my current car, but a little more modern.

I wasn't sure what performance specs to look at other than horsepower and curb weight, is there something I should specifically focus on? I enjoy more the speed off the line than a blazing top end (I never drive above 85 for any length of time). Again, not looking for specific models per say, rather the specs I should look at (as far as models, I'm looking at the base Porsche cayenne, but based on the HP vs weight, I'm not sure it's much better).

Here's my current car:

1994 BMW 530i SEDAN

Engine Type V-8, dohc - 32 valve, smpfi* M60B30
Engine Size 3.0 liter/183 cid
Horsepower 215 @ 5800
Torque (ft/lbs) 214 @ 4500
Wheelbase/Length 109"/186"
Curb Weight 3650
Pounds per Horsepower 17
Drive Train front engine/rear drive

* smpfi - sequential multiport fuel injection

PERFORMANCE

EPA Economy - miles per gallon,
city/highway/observed 16/23/19.6
0 to 60 mp 7.5 sec
1/4 mi (E.T.) 15.2 sec
Coefficient of Drag (Cd) .32

Thank you - Chris

[cosimo]

Torque is the biggie, hp is only important as it pertains to weight. Torque is what gets you off the start at redline.

[beerformeplz]

Originally Posted by cosimo

Torque is what gets you off the start at redline.

+1 Also you can always chage the rear gearing. Thats the first thing I do when i buy a new mustang is new gears. Feels like 100 extra horses and awsome from stop light to stop light.

[JBat]

Originally Posted by cosimo

Torque is the biggie, hp is only important as it pertains to weight. Torque is what gets you off the start at redline.

x3. Torque is what will give you the good acceleration.

[sparky_magoo]

Consider a Dodge Charger Daytona. 350 HP stock. Mine has 400+ with minor modifications and now get 18 mpg around town and 25 mpg hiway. Only 1650are made a year.

Best in class interior and above average reliability. It's perfectly balanced and has superb handling. It comfortably carries four adults and a Labrador.

Now, I have to talk the wife into allowing me to buy a Rolex Daytona to match!

[beerformeplz]

Originally Posted by sparky_magoo

Consider a Dodge Charger Daytona. 350 HP stock. Mine has 400+ with minor modifications and now get 18 mpg around town and 25 mpg hiway. Only 1650are made a year.

Best in class interior and above average reliability. It's perfectly balanced and has superb handling. It comfortably carries four adults and a Labrador.

Now, I have to talk the wife into allowing me to buy a Rolex Daytona to match!

Yea but the weight offsets the hp rating.

The Cadillac cts-v has a 3.9 0-60 according to jalopnik


http://jalopnik.com/5043650/2009-cad...+v-first-drive

[Army_Doc]

check out the dyno results for your prospective cars...you'd be surprised how much horsepower/torque some cars loose from the engine to the wheels (example: Mazda Rx8's rotary: 232 Hp engine, but 170-ish at the wheels). Horsepower and torque aren't everything (weight matters), but they mean a whole lot more at the wheels than at the engine.

To look up dyno results, just google the car plus dyno.

[rainman_16]

Originally Posted by Army_Doc

check out the dyno results for your prospective cars...you'd be surprised how much horsepower/torque some cars loose from the engine to the wheels (example: Mazda Rx8's rotary: 232 Hp engine, but 170-ish at the wheels). Horsepower and torque aren't everything (weight matters), but they mean a whole lot more at the wheels than at the engine.

To look up dyno results, just google the car plus dyno.

True - often you'll find a 10-15% parasitic loss through the drive train to the wheels. It also depends what sort of dyno is used. If comparing car dyno plots, make sure your comparisons use the same sort of dyno for apples to apples consistency (i.e. Mustang dyno, Dynojet, etc.).

[TattooedGQ]

+1000 on the torque, weight, and gearing. That's how you accelerate. If you really want to go nuts, and still have a highway driver check the transmission ratios. that will give you a good idea of how you're going to pull from a stop.

[chenx15]

M5, 335I, or Audi S4

[AWATCH]

This will help regardless what you drive

[ParisDakarBmw]

Put the nitro kit in! That will restore the pickup you so desire!

Great idea Awatch! Surely that isn't your truck. GA has laws against such crimes

[AWATCH]

Originally Posted by ParisDakarBmw

Put the nitro kit in! That will restore the pickup you so desire!

Great idea Awatch! Surely that isn't your truck. GA has laws against such crimes

Well it is, but don't tell the law.......

[openwheelracing]

Actually horsepower is derived from torque, the biggest difference:

Horsepower is the actual work. Horsepower is KING, people.

[2005rivers]

Originally Posted by openwheelracing

Actually horsepower is derived from torque, the biggest difference:

Horsepower is the actual work. Horsepower is KING, people.

Yes, hp is derived from torque. but in terms of hp and torque, you "feel" torque when you step on the pedal, not hp. torque plants you back in the seat

[tjs3023]

My Viper has plenty of torque. 500+hp,525+torque. Leaves lights in a cloud of tire smoke. Lots of fun.

[scottschoe]

The base Cayenne is one slow dog, so I'm not sure if you'll really enjoy scooting around in that. You should really narrow down type of vehicle before jumping into specs - there are a million and one combinations of hp/torque/weight dist/curb weight/fwdrwdawd4wd/transmission/seating/etc, so it's a bit difficult to make recommendations like this.

Well, since we're recommending random cars, E36 M3 on a diet?

[CL65AMG]

More is better...

[axxeman01]

CL65AMG - Haha. Simple enough. Moderation in all things except moderation and horsepower then :)

[2005rivers]

No replacement for displacement!!

[Mrdi]

Drive a new 5 series.

[SeamasterGMT]

1. There is no way your BMW still has 215 bhp after 16 years. Probably more like 150.

2. I nicked this off piston heads forum.


"What really matters most of all is the tractive effort (force) delivered where the driven wheels touch the ground. Your gearbox, diff and wheel diameter change the alter the rotational speed and torque. rotational speed is reduced by a total ratio factor, and torque (and therefore force) is increased by the same ratio (let's ignore frictional losses in the drivetrain for now). Using a shorter ratio (lower gear) increases this ratio compared to a higher gear. Therefore there is more tractive effort in the lower gear. Therefore it will accelerate quicker. If the ratio for first is half (or twice, depending on how you look at it) that of 4th, then acceleration in 1st would be twice that in 4th. As:
Final speed = Initial speed + (acceleration x time)
your 30-70 time would halve.

Now, since power is torque x rotational speed, you will quickly spot that Power In = Power Out. If you had an engine that produced constant power through the rev range, then you WOULD see identical acceleration figures.

So I suspect you might have your assumptions the wrong way around. A few things to remember:
- Power means nothing without knowing weight (anyone who disagrees with this can try to explain why my 140bhp car does 60-100 in 2.5 secs)
- Torque means nothing without knowing gearing (anyone who disagrees with this can try to explain why my 70Nm car can....etc.)
- Power in = power out (so power at the engine = power at the wheels). Not strictly true because of losses, but a good mnemonic when you remember...
- Torque in does not equal torque out. It is always factored by the gearing.
- so, correct gearing is crucial.
- Where power and torque appear is almost as important as what figures you actually get.
- For foot-to-the floor motoring, power tells you more than torque.
- Torque gives you more flexibility, whether that is when you are not using full throttle, running outside the normal rev range (like stump pulling), or in transient variations (whether that means kickdown, or running over a cat's eye)
- If all you know is the max power and max torque, max power tells you more. However, it's like trying to estimate the contents insurance of a house by looking through the letterbox or keyhole (ie not very)

Now to prove that you've understood it all, another practical question:
You have four identical swimming pools that need draining. You have four similar pumps:
Pump A gives 1hp power, 1lbft torque
Pump B gives 1hp power, 2lbft torque
Pump C gives 2hp power, 1lbft torque
Pump D gives 2hp power, 2lbft torque

Pump A takes exactly 12 hours to drain its pool
Estimate how long each of the other pumps take, and justify your estimates.

Your homework is due by Friday afternoon."

[Andad]

The pumps will run dry before they drain the pool.

oops.

[Andad]

How long would these take to drain the pool?

[Gagebuilder]

393 hp, nice! You still have that?