What Is the Dividing Line That Makes a Car Fast?

On the GRM forum we are constantly talking about driving a slow car fast or momentum cars and or preferring fast cars.

That's all fine and good but we don't ever really seem to define what we consider a fast car. It's often said that all cars are momentum cars if you are driving on the limit but that doesn't really help define it either.

Then we have the wrinkle of my much loved single seaters; many of these cars are turning similar lap times as high horsepower cars.  For example at Laguna Seca Randy Pobst turned a 127 in a McLaren Senna, meanwhile the SCCA P2 and Formula Continental records are in the 125s.  A P2 is fast but it doesn't drive like a 700hp car.

So for me I've always defined a fast car (from a production car standpoint) as something that will do 0-60 in under 4 seconds and run a sub 12 1/4 mile. For a Formula car the dividing line is a Formula Atlantic (1200lb car with 300hp) 

Additionally for any car whether it's a single seater or a production car; if it can spin the tires coming off medium speed corners. I define medium speed as 75-80mph. Also when I say spin the tires, I mean leave distinct black marks on the tarmac level wheel spin.

So I am curious to see what your definition is.

I feel like 10 pounds per horsepower is a pretty good dividing line. That's going to get you under 13 seconds in the quarter, and more than enough to have fun on the street.

Tom_Spangler (Forum Supporter) said:

I feel like 10 pounds per horsepower is a pretty good dividing line. That's going to get you under 13 seconds in the quarter, and more than enough to have fun on the street.

That sounds about right to me even though some modern cars blow that number out of the water. 

Thinking about it in a track context, I would say it's more than just power to weight -- it's (power to weight) to GRIP.

To make up some numbers to illustrate a point, let's say that a car that corners at 0.8 gees needs 12 lbs per hp to be a "fast" car.  If you take the same car and make a bunch of suspension/tire/downforce/etc changes to it so that it now corners at 1.2 gees, then 12 lbs/hp might fall back into the range of a "momentum" car, and perhaps you need get it up to 8 or 9 lbs/hp to get back to being "fast".

This is less relevant on the street, I think.

In reply to codrus (Forum Supporter) :

I should clarify; I meant this to be in context of on track.

Lack of grip can make a car feel fast; a 300hp car on skinny tires feels a lot faster than it actually is (think old muscle cars).

I don't think I have enough real-world experience to quantify an answer, but I'm interested in this discussion nonetheless.

For production cars I think 10lb/hp is a good start on the street. Much slower and i wouldnt ever say fast.
 

On track I think you need more. Closer to 8lb/hp. Mine is about 9 and i wouldnt say its fast. my last car was about 8 and probably closer to what id think of fast. 

I think the 10lb per 1 hp is pretty good. My '13 Mustang GT track pack was I think ~3500lbs with 420 hp. But it came with tiny 255 wide Pirelli's and the shorter final drive (3.73 vs 3.31) made it a riot, but never got a chance to track it. My '13 135i was about the same weight with 300/300, but with the DCT and ALL THE TORQUE from basically idle to 5400 rpm, it was plenty quick to get in trouble on the street as well.

Now I don't see the point of that much power on the street. You can't use it unless you're being a jackass. Although I did want a new Mustang GT before ordering the BRZ back in 2022, just couldn't justify the price for how little I drive. 

My first "fast" vehicle was my 2004 Yamaha R6. Graves velocity stacks, Akrapovic exhaust and dyno tune had it around 109 whp and rev'd to around 15k. My best time at the strip was 11.21 @122. And that was carrying the front wheel all the way through 2nd. 

Tom_Spangler (Forum Supporter) said:

I feel like 10 pounds per horsepower is a pretty good dividing line. That's going to get you under 13 seconds in the quarter, and more than enough to have fun on the street.

This is my line for fast. IE something like a 2700lb 240hp S2000 is just above 10lb/hp and I see them as Quick. Anything is in the 6-9 range is more then anyone needs on the street but for track is just about perfect IMO. One the street anything that is faster then your vision which is really anything Miata speed is overkill but still fun. 

My V4SP with me on it, in gear, weights 570lb/s and 220hp dyno confirmed and I have not come up with a term for that one. Ludicrous speed maybe. 

If you get into the really light cars like my 550 which is around 4.9lb/hp your not driving it, your just along for the ride and your skill is keeping it off the wall not running a good line. This is not fun. 

I wont declare the line, but I do like the test that Car and Driver did since it covers a variety of transient events for some pretty sporty cars. https://www.caranddriver.com/reviews/a45765297/0-150-0-mph-speed-test-2023/

ANY of the cars qualify for my needs!

I started driving in the 1970's, so anything under 9 seconds 0-60, or under 16 seconds in the 1/4 mile.

LOL.

Only slightly joking.  Okay, so under 5 seconds 0-60, which was supercar fast back then, like Porsche 930 Turbo fast. 

My Mazda CX-9 feels fast to me.  The Shelby GT-350?  Pure insanity.

I can tell you what it's not. It doesn't seem to be 3,200 pounds, 200 horsepower, and all-wheel drive. It doesn't seem to be that no matter how hard I flog the thing.

In reply to confuZion3 :

Imagine what it was like for rally drivers in 1987 when they stopped driving sub-2000lb, 300-500hp cars and started driving 2400-2600lb, 250hp cars!

Oh and no more 5 day long events with only one, maybe two overnight rest halts.

That's when you started to see the drivers wringing 110% from the cars.  They were slower and the drivers actually got to sleep sometimes so they weren't constantly exhausted.

Many many years ago I drove a 400hp Quattro and today's cars with the same amount of horsepower are so much faster.

In reply to Tom1200 :

Audis were the worst at Group B... the later ones had 6:1 compression in a 2.1l engine, and the turbos were sized to make a reliable 500hp which means hotsides sized so they didn't even get full boost until the far right side of the tach.  You had to drive them very intently to wring performance from them.

When the cars were limited in power after the Group B era, they HAD to focus on response and drivability.  It wasn't but a few years before the power limited cars were actually faster than the unlimited ones.

I dimly recall a magazine test of one of the last of the Group A Imprezas.  They didn't make more than 300hp because of the restrictor.  But the cars could do an 11 or 12 second quarter mile... on gravel.  They may have made 300hp but they made it everywhere

0-60 in seven seconds is quick.

0-60 in six seconds is fast.

0-60 in less than six seconds is wasted on the street.

OK, ok, I know, but I started reading car magazines in 1985 and I haven't updated my standards.

However, when I was using a 125cc shifter kart for training, EVERYTHING ELSE was slow.  Even today, a C8 Corvette is still slow.  So any distinction is arbitrary, and my rules above are my arbitrary rules.  :-)

Power to weight is a figure you can use as a ballpark, however you have to factor in how that power makes it to the pavement.  Give me an 800hp 2500lb car with a 2 speed Powerglide transmission and 2.73 rear end, I may not feel it's all that fast.  Lots of factors to consider.

Of course this is a very subjective question.  I was a teenager in the 80s so I thought an IROC-Z was fast.  A modern Accord could smoke it.  I also now spend a lot of time behind the wheel of some powerful and expensive cars, so my perspective has changed a lot.  "Fast" for me is purely seat of the pants feel.

In reply to SKJSS (formerly Klayfish) :

IROC Zs had soft suspension and sketchy brakes so, yeah, they felt fast.

I feel like the perception of fast has shifted over time, especially for production cars. 

Power has gone up and up, additionally, as eluded to above, peak numbers are deceptive. They have also gotten better about exploiting "area under the curve" with flatter power bands and transmissions with more gears to better utilize them. Additionally automatics that shift faster, or cvt tech beginning to come into it's own play a role. 

Now, curb weight has been climbing too, but the above is offsetting a lot of it.

That covers acceleration mostly.

Cornering - wider tires, better geometries, better damping. Sheer road holding is way better than it used to be. 

Take my 97 Mustang Cobra. Fast in it's day, but by the 10lb/hp measure, it's just out of being fast. 3200lb/305hp (how expensive are supercharger kits after all this inflation?)

On the other hand, for track. I've been obsessed in the formula car realm lately. 

Formula Vee - 1025lb/75hp -13.7

Formula 600 800lb/105hp- 7.6

Formula Ford 925lb/110hp - 8.4

Formula Continental 1200lb/150hp - 8

(Bit of a misnomer, because with equal drivers, that FV is gonna be way faster than my F6)

So, the only "not fast" formula car is the Vee. I mean I guess it tracks?

Apexcarver said:

Take my 97 Mustang Cobra. Fast in it's day, but by the 10lb/hp measure, it's just out of being fast. 3200lb/305hp (how expensive are supercharger kits after all this inflation?)

On the other hand, for track. I've been obsessed in the formula car realm lately. 

Formula Vee - 1025lb/75hp -13.7

Formula 600 800lb/105hp- 7.6

Formula Ford 925lb/110hp - 8.4

Formula Continental 1200lb/150hp - 8

(Bit of a misnomer, because with equal drivers, that FV is gonna be way faster than my F6)

So, the only "not fast" formula car is the Vee. I mean I guess it tracks?

 

 

 

I have a self professed single seater obsession; I remind myself weekly I promised the wife I would stay out of them (they've always scared her but she finally admitted it when I sold the F500). I've done Formula Vee, Formula Ford, D-Sports Racer and F500.

Single seat cars offer so much performance for not a lot of money.

The current SCCA P2 cars are 1200lbs and 200hp. My cousin holds the class lap record at Laguna Seca; he's turning the same lap time as the Czinger 21 hypercar. His Stohr definitely didn't cost $2 million; 40K will be a good one 55-60K will buy a RunOffs Winner. 

A local guy like me can find a solid sports racer for around 20-25K, which will give me access to a lot of track days as well as vintage or SCCA.