Lightweight or Horsepower?

In reply to Keith Tanner :

I constantly toy with ways to cut drag on the Datsun but the real issue is the motor. The 1200cc motor is 20hp less then the 1500cc motor but the difference in top speed is only about 8mph. I also figured out that the aero mods I can make under the rules aren't worth the effort given how mildly tuned both motors are. Even with the bigger motor it does all of 106.

Gearing the snot out of it would do more.

Tom1200 said:

In reply to Keith Tanner :

I constantly toy with ways to cut drag on the Datsun but the real issue is the motor. The 1200cc motor is 20hp less then the 1500cc motor but the difference in top speed is only about 8mph. I also figured out that the aero mods I can make under the rules aren't worth they effort given how mildly tuned both motors are. Even with the bigger motor it does all of 106.

Gearing the snot out of it would do more.

Even though the top speed isn't that much higher,, would get it to the 1200cc top speed more quickly enough (that's awkward) to make it worthwhile? 

There is no such thing as insufficient power, only excessive weight.

OTOH my opinion is also that if handling over 60mph is a problem, the course is too fast and should be tighter.

Tom1200 said:

So the two fastest cars (lap time wise) I've ever driven were 94" (D-sports) &  99" (Formula Super Vee) wheelbase. Power was 175hp and 225hp respectively. Both cars were a little over 1000lbs and both cars had a decent amount of downforce.

The fastest non downforce car light I've driven was a turbo NB Miata (I think it was a MSM with mild tweeks). That was still fun but much more than that on a  short wheelbase might not be fun.

I think the wheelbase may be the key to why I'm not crazy about much more then 200hp in these cars. They start getting up to speeds where the don't feel near as settled. My Formula 500 is on a 73" wheelbase; I can tell you it's not near as planted as the D-sports racer was in a 120mph corner. I think that's a combination of  no downforce and short wheelbase.  

Also touched on here is the fact that it's much easier to do hooligan things when your only doing 85 versus 135. 

 

Lap times mean almost nothing unless you're racing with identical cars. 
        The dice, wheel to wheel, the chess game of racing.  Where to make your move. What move to make.   How to time the move so there is no counter  to it.  
       
    Finally wheelbase?   The Black Jack had an 88" wheelbase and a 50" track.  Add a locked rear end  and the slipperiest body ever designed by an aero engineer. 183 mph down the Mulsane straight with only 250 horsepower in 1955. 
   That is fun!!  Really serious fun.  A full face helmet turned sideways  would change the direction of travel without moving the steering wheel. 

My belief is that 300hp and 300ft lb @ 5500 rpm in a car that weights 3000 lbs or less is a sweet spot for a street driven car. Drivable with " set you back in the seat " performance on pump gas with no need of power-adders.

Going much above this takes you into thrill-ride mode. Its fun, but only for short time periods at great expense with a lot of waiting in between rides.

In reply to NOHOME :

Not necessarily, unless you're assuming boost is a requirement to go beyond your specs. We found our LS V8 customers would happily rack up tens of thousands of happy miles without contacting us. But beyond your line you're definitely at a point where you have to respect the machine or handicap the bejeebus out of it electronically. 

In reply to Keith Tanner :

Somebody needs to start selling nd miata ls conversions................waiting 

I kinda like medium. Long wheelbase ~3000lbs with up to 300HP is where I like to be. I'm not a good enough driver for lightweight and SWB cars. Haven't spent enough time on track to learn to learn that quick of reflexes. When the TR8 started to spin it took a lot more mental effort than when my SKlasse starts to spin. And with more HP that margin of error gets smaller with my untrained gas foot.

z31maniac said:

Even though the top speed isn't that much higher,, would get it to the 1200cc top speed more quickly enough (that's awkward) to make it worthwhile? 

With the 1500cc motor it definitely gets up to speed faster. The big difference is the 1200cc motor really hits the aero-wall at 90mph whereas the 1500 pushes through that to around 102 before it really slows down. 

I'll assume you are referring to race cars. With mine being the Fiat 850 I already have light weight, usually weighed in around 1500 lbs. and can go lighter with some labor and materials. Pardon the following rant.

Horsepower is another matter altogether. Back when I was running I had the modified stock head and modified little carb. The actual hp was so minimal I don't recall the number. However, after all 12 of the 850s that ran H-Prod quit because we were put up against cars with 1200cc motors and not allowed anything to compensate theeennn SCCA gave us what had been asking for - an aftermarket head with DCOEs. But I and others were gone by then and f-n SCCA dropped the 850 off the PCS.

Forward to around 2005 or so and I heard that the cylinder head had eventually  been allowed. I then found one in . . . Las Vegas. I then got the 850 reinstated by SCCA. Then had a motor done just in time for the 2008 real estate issue. I am told the motor at 8500 rpm is go0d for a RELIABLE over 100 horse.

I've owned a lot of Miata's, a few German cars, and a lot of V8 pony cars and two Subarus.  I like driving them all and for different reasons.  Each requires different techniques and feels different behind the wheel.  All are good.  A lightweight car does provide feedback to driver inputs better in most cases.  My ideal car would weight 2500 lbs have full independent suspension, be RWD or AWD and have 300-400 hp.  It'd also be awesome on pavement and capable of rallycross too.  

Spoiled after years on the track with a 900# car with 155 HP.  Yee Haw.  Of course a Formula Continental has fairly good aero to add to the formula.

The Outlaw Bug at 1500# and 200 HP, is a fun toy.    Who needs two tons to motivate one person in a fun way?

In reply to Purple Frog (Forum Supporter) :

I've often joked about running a cheater FC with a moderately tuned 2.0 pinto putting out around 185hp as an Atlantic in vintage. 

I know the Pro F2000 cars ran similar lap times to our DSR so an outlaw FC would be loads of fun.

NOHOME said:

My belief is that 300hp and 300ft lb @ 5500 rpm in a car that weights 3000 lbs or less is a sweet spot for a street driven car. Drivable with " set you back in the seat " performance on pump gas with no need of power-adders.

 

Going much above this takes you into thrill-ride mode. Its fun, but only for short time periods at great expense with a lot of waiting in between rides.

 You need 300 horsepower not because you actually use that much on a street car. But because the 300 ft pounds of torque (+ or - )  comes on at 4800 rpm.  Torque of an electric is at zero so Acceleration starts instantly.  
   Even with heavy battery pack.  It just feels fun. 
   

Depends on where I am driving, and things are changing as I get older. 
 

My MINI Cooper S JCW is a hoot to drive on the twisties.  But I recently had to spend a few weeks driving it long distances daily (3+ hours at a time). It was miserable on the interstate.  I'm thrilled to be back in a 5000 lb full sized truck with 400 hp. 
 

It's also changing as I get older. My reaction time simply isn't what it used to be, and my eyesight isn't as sharp. I wouldn't be able to handle a 2400 lb 500 hp car. My number is about 300 hp 2400 lb.

Age also has me appreciating some creature comforts a bit. Most of them come with a few lbs.

frenchyd said:

NOHOME said:

My belief is that 300hp and 300ft lb @ 5500 rpm in a car that weights 3000 lbs or less is a sweet spot for a street driven car. Drivable with " set you back in the seat " performance on pump gas with no need of power-adders.

 

Going much above this takes you into thrill-ride mode. Its fun, but only for short time periods at great expense with a lot of waiting in between rides.

 You need 300 horsepower not because you actually use that much on a street car. But because the 300 ft pounds of torque (+ or - )  comes on at 4800 rpm.  Torque of an electric is at zero so Acceleration starts instantly.  
   Even with heavy battery pack.  It just feels fun. 
   

In my mind, the 300hp isn't needed at low speeds in a street car.  With good gearing and a good powerband (or electric) you've got plenty of punch at lower speeds.  As an example, my E38 feels plenty punchy at low speeds (good gearing, ~285hp, 4100 lbs).  It's passing on fast 2 lanes, highways, etc. particularly with hills involved where raw hp comes in.  And in that later situation, I wouldn't find the E38 overpowered with an extra 100hp even though I'd never get my foot down all the way at low speeds on the street. 

Great discussion and points made.  I have a soft spot for both ends of the spectrum.
 

 My chubby girl CTS-v at 3700lbs and 474whp is a hoot but absolutely chews up consumables.  Thr thrust of hp/tq/sound is really something I'll miss when she sells this week.

The 1850lb Rabbit GTI on the other hand can be driven 10/10ths all the time and tires and brakes  last more than a season.  Super engaging to drive despite the 100whp from the relatively built motor.  It is a ball to run at Mid Ohio with all the twisty bits where it outruns lots of legit fast cars.  It is depressing to enter the main straight and exit it at the same top speed though...

84FSP said

The 1850lb Rabbit GTI on the other hand can be driven 10/10ths all the time and tires and brakes  last more than a season.  Super engaging to drive despite the 100whp from the relatively built motor.  It is a ball to run at Mid Ohio with all the twisty bits where it outruns lots of legit fast cars.  It is depressing to enter the main straight and exit it at the same top speed though...

My Datsun; we had an event at SMMR where there was a wicked 20 mph headwind up the front straight.  The game then became seeing if I could enter turn one without braking. I got to the point where I could slide it in catch it and quickly get back on the gas............it was a bit sketchy but at 83 mph it was silly fun. 

84FSP said:

Great discussion and points made.  I have a soft spot for both ends of the spectrum.
 

 My chubby girl CTS-v at 3700lbs and 474whp is a hoot but absolutely chews up consumables.  Thr thrust of hp/tq/sound is really something I'll miss when she sells this week.

The 1850lb Rabbit GTI on the other hand can be driven 10/10ths all the time and tires and brakes  last more than a season.  Super engaging to drive despite the 100whp from the relatively built motor.  It is a ball to run at Mid Ohio with all the twisty bits where it outruns lots of legit fast cars.  It is depressing to enter the main straight and exit it at the same top speed though...

Makin' me miss my Golf, you are.

My Quantum was even less powerful, corner exit was usually the slowest part because maintenance throttle for basically anything over 35mph or so was WOT.

But I tell ya, if you want to find the most efficient line and driving style, it's the best way to learn, because improvements are easily measured and mistakes are ruthlessly punished.

SV reX said:

Depends on where I am driving, and things are changing as I get older. 
 

My MINI Cooper S JCW is a hoot to drive on the twisties.  But I recently had to spend a few weeks driving it long distances daily (3+ hours at a time). It was miserable on the interstate.  I'm thrilled to be back in a 5000 lb full sized truck with 400 hp. 
 

It's also changing as I get older. My reaction time simply isn't what it used to be, and my eyesight isn't as sharp. I wouldn't be able to handle a 2400 lb 500 hp car. My number is about 300 hp 2400 lb.

Age also has me appreciating some creature comforts a bit. Most of them come with a few lbs.

You make good points that I happen to agree with. For the road and long trips I'll take my pickup. 
  Yet toys?   Give me cheap old grandpa's reward car.   I don't care if it's a Mercedes Benz 450  BMW, Audi,  or Jaguar XJS.  You can find them for $500  and for less than $2000 turn them  into a tire smoking  source of fun.  
          500+ horsepower. Less than 3000 pounds. 
     Yes they are obsolete!!!  15 inch wheels?   Mostly automatics.  ( typically  that can be changed)   But still real fun.  
      OK a lot of newer cars with a fraction of the power will go faster.   But not as cheaply.  It costs next to nothing  to strip them of 1000 or more pounds of weight.   If the paint will buff out then decals will make it look racy.  Cheap entry fees ? HODE and autocross.    Wheels and tires ?  Every thing from stockish to NASCAR  take offs can be used. 
     You'll need to spend $135 for an Amazon Turbo. (2 if it's a V engine  ) And $50  ($100x2) for a waste gate.  Stock manifolds. A little welding of exhaust tubing  and Bob's your uncle.  
     Then toss that stock ECU  and use an aftermarket Megasquirt or Maxx.  Add a $40 inline fuel sensor  so you won't need to pull the engine apart. And are using E85.   I realize you don't have any near  you but you can get it delivered in either 5 gallon cans or 55 gallon drums.   It won't be any more expensive than premium and a lot cheaper than Racing gasoline.  
      Leave the license plate on if it's got one and you live in a state without inspections.  
 Save the need for a trailer and tow vehicle.  

Keith Tanner said:

In reply to NOHOME :

Not necessarily, unless you're assuming boost is a requirement to go beyond your specs. We found our LS V8 customers would happily rack up tens of thousands of happy miles without contacting us. But beyond your line you're definitely at a point where you have to respect the machine or handicap the bejeebus out of it electronically. 

Beyond this point is where I would not hand the keys to the wife or to an unexperienced friend.

At 300 hp the car goes " hang on, we are going to go fast and quick wheeee!" Over 300 its more like "holy E36 M3 are we ever going fast, I need new underwear". 

Build quality does blur the line to some extent if it keeps things linear and the chassis is built to match.

For lightweight cars there is another factor that I haven't mentioned.

With bigger higher horsepower cars the processing time is going to get shorter and shorter between tasks. As your timing degrades, so do lap times and potential for disaster.

I find it's easier for people to bring the car back from the brink in a lighter car (regardless of power output).

What a timely topic!.. I'm prepping my light/ low HP car for autocross and track days this spring/summer (2023), and being quite new to these events (despite my advancing age, I've only done one of each), I'm really looking forward to learning what the car will or will not do..  This car is right at 1000# (1959 Berkeley) with a little V4 bike lump (about 110hp).. It's close to 9.5:1, and I've just fitted it with 100tw tires.. I don't have much to add to the topic, other than to say that the short 70" wheelbase seems to be a limiting factor as to how crazy I'll allow myself to get.. maybe I'll grow to love the feeling of being on the edge of certain disaster?   Anything over 100 mph is more scary than fun..  Great topic.. I do love the high HP stuff, but I truly love the experience of low-powered cars driven in anger  

Neither (for lap times).

Given all else, I want grip.

I've done track days in everything from a 110hp FB RX7 to a 500hp GTO and everything in between. Light is fun, power is intoxicating, and both are slow af without grip. I'd rather lap all day in a penalty box with all the cornering Gs in the world than a substantially better car with worse tires/suspension. 

With a lighter car there is less kinetic energy when you hit something.   So... I try not to hit anything anyway.