SCCAForums.com

Say you have two cars, they have an extremely similar suspension setup and are on the same tires, one has 70whp and weighs 2000 pounds, one has 120whp and weighs 2300 pounds. They are both FWD open diff and the lighter car also has a 2 inch shorter wheel base.

 

How much of a difference will there be in the performance? 

323 vs. EGT?

---

Erik B.
Wisconsin Autocrossers, Inc
www.waiautox.org ___/\___/\___/\___/\___/\___
2007 Mazda6
2000 "Fozda" ZX2 S/R--STS Anti-Civic

When you say same tires... same compound, or same size?

 I look at it this way... the Civics that dominate STS are dog slow in a straight line.  But they only weigh 2000lbs.
 

---

-Travis Finlay
1997 Saturn SC2
2002 Subaru 2.5RS
1995 YZF 600R

atechnica:

Say you have two cars, they have an extremely similar suspension setup and are on the same tires, one has 70whp and weighs 2000 pounds, one has 120whp and weighs 2300 pounds. They are both FWD open diff and the lighter car also has a 2 inch shorter wheel base.

 

How much of a difference will there be in the performance? 

They both get slaughtered by the cars on those same tires, that have even better suspensions, make 120whp, and only weigh 2000 pounds.

 STS Civics are not that slow in a straight line, at least in comparison to other STS cars.

---

--Jason Rhoades

i would say go for the lightest car you can...as long as they have close power/weight ratios.  in the example you provided, though...you have a power to weight ratio of  19.16 on the 120hp car and 28.57 on the 70hp car.  if the ratios were a bit closer...say a 100hp weighing 2000 lbs, i would go for it.  lower power to weight is good for acceleration...but you can also throw a lighter car around a corner faster..and conserve momentum easier because you won't be into the brakes as hard...or early.

---

Considering the amount of time spent turning/transitioning versus the amount of time spent at full throttle in autox, most would agree that given equal tires, weight is more important.

---

VW R32
32 STX

Weight is definitely more important, to a point. You have to have some power though. And a good suspension design. It's a mix for sure. If weight completely dominated the other factors, you'd see 1600 or 1700 lb cars on top of STS, not 2000 lb cars.

---

Brian Davis, 89 Civic Si, 158 STS

turbohappy:

Weight is definitely more important, to a point. You have to have some power though. And a good suspension design. It's a mix for sure. If weight completely dominated the other factors, you'd see 1600 or 1700 lb cars on top of STS, not 2000 lb cars.

 

We had a nearly stock old old old style civic with 50hp play in STS here and it did SURPRISINGLY well. It kinda makes me wonder.

 

I can't really think of anything that's better than the 89 civic, but I got a 323 for $200 so I was considering trying it once or twice just to see what would happen.
 

turbohappy:

Weight is definitely more important, to a point. You have to have some power though. And a good suspension design. It's a mix for sure. If weight completely dominated the other factors, you'd see 1600 or 1700 lb cars on top of STS, not 2000 lb cars.

Go for the lighter one. Just add a little more power to it and the good suspension design turbohappy suggested. :)

 

 

 

_____________________________
Perfect trucks, perfect truck parts.

 

It all depends.

Land speed racing - its all about power and drag

Drag racing - its all power to weight

Autocross - is more about weight, because lightweight makes you accelerate faster in ALL directions (better braking, cornering, and straight line acceleration)

Road racing - is a mix between Autocross and drag racing

 

And of course, a really light car on skinny tires will often be beat by a heavier car with wide tires.  So think tire to weight too.
 

---

Bruce Funderburg
'02 CMC 7 - DM
'04 Subaru WRX STi - STU

It will be of little avail ... if the laws [or rules] be so voluminous that they cannot be read, or so incoherent that they cannot be understood...
Alexander Hamilton

ProDarwin:

I look at it this way... the Civics that dominate STS are dog slow in a straight line.  But they only weigh 2000lbs.

 

 

I have to agree with Jason here, a fully prepped STS civic is pretty darn fast in a straight line. I was amazed when I first drove one with a healthy motor.  

---

00' 328Ci
01' Tahoe LT
98' Camaro Z28 - dead
95' 325is - STX 182

Grintch:

Drag racing - its all power to weight

Autocross - is more about weight, because lightweight makes you accelerate faster in ALL directions (better braking, cornering, and straight line acceleration)

Road racing - is a mix between Autocross and drag racing

Basic physics suggests otherwise, and has been proven in many different classes in drag racing, i.e. Bill Jenkins small block Vega vs. Sox & Martin Hemi Cuda.  Given equal power to weight ratios, the lighter car will be quicker due to the forces of inertia. "An object at rest tends to stay at rest." It is easier to get the lighter vehicle moving. Henceforth, it it also easier to get it to slow down or change direction. "An object in motion tends to stay in motion."

200 hp @ 2000 lbs. vs. 400 hp @ 4000 lbs. ... my money is on the lighter car.

Jim 

 

Basic physics is F=m*a (force = mass x acceleration) or a = F / m.  Where HP is related to the force availible.

 The Vega & Cuda probably both mounted the same size rear tires, so the Vega had the superior tire to weight ratio.

 

So if you have the choice of sending $1000 to reduce the weight by 10% or increase the power by 10%,

for top speed increase power

for drag racing it is close to a wash (with fixed tire sizes, reducing weight will be slightly better)

for autocross or road racing reduce the weight

 

Of course in real life the choice is never that easy, too many other factors (like what the rules allow), and the comparative cost and results usually aren't known ahead of time.
 

---

Bruce Funderburg
'02 CMC 7 - DM
'04 Subaru WRX STi - STU

It will be of little avail ... if the laws [or rules] be so voluminous that they cannot be read, or so incoherent that they cannot be understood...
Alexander Hamilton

Mooobunnny:

ProDarwin:

I look at it this way... the Civics that dominate STS are dog slow in a straight line.  But they only weigh 2000lbs.

 

 

I have to agree with Jason here, a fully prepped STS civic is pretty darn fast in a straight line. I was amazed when I first drove one with a healthy motor.  

They should at least be mid 15 second 1/4 mile cars if fully built for STS.  I wouldn't call that extremely fast, but that certainly isn't dog slow, either.

---

Todd
Too many ST cars

"Restricted Area Racing"

tkm:

Mooobunnny:

ProDarwin:

I look at it this way... the Civics that dominate STS are dog slow in a straight line.  But they only weigh 2000lbs.

 

 

I have to agree with Jason here, a fully prepped STS civic is pretty darn fast in a straight line. I was amazed when I first drove one with a healthy motor.  

They should at least be mid 15 second 1/4 mile cars if fully built for STS.  I wouldn't call that extremely fast, but that certainly isn't dog slow, either.

 

I wouldn't be surprised if they were faster than mid 15's, my STS car (the 120+?whp 2300lb one) runs even with low 15 second cars from a roll, but then it does have more torque than a civic.

FWIW: We've run 14.60's with our STS Neon ACR.

Jim

SeniorPBA2B:

FWIW: We've run 14.60's with our STS Neon ACR.

Jim

That's impressive, what was your power/weight and tires? 

 

EDIT: actually this is interesting enough to make a thread out of :cool: 

The motor was 128 hp at the wheels on last year's DNO Dyno Day. With 1/4 tank of gas, it weighed 2,347 lbs. at the Toledo Pro Solo, plus my 145 lb. driver. We last ran the car on the strip in June or July of '06, so I honestly don't remember if the 14.60's were on Victoracers or Azenis.

Jim

ya..
I foolishly thought my old 97 GTI VR6 would be the fastest STS car in a straight line with 150hp and 160lb-ft to the wheels (at mile high elevation), though it was 2700lbs and not fully prepped or lightened at that.

At the 2006 Denver ProSolo I went up against many well-prepped Civic Si's and I had nothing on them. After the first corner it was all downhill of course.. especially as I was using the same 205/50-15 Azenis 615's that they were. Good times.
http://naufana.com/autox/20060722diaprosolo (videos)

---

-Kelly
Rocky Mountain Region Solo / Time Trials - 94 Integra SM.
Apex RacingGroup.com

gtitronic:

ya..
I foolishly thought my old 97 GTI VR6 would be the fastest STS car in a straight line with 150hp and 160lb-ft to the wheels (at mile high elevation), though it was 2700lbs and not fully prepped or lightened at that.

At the 2006 Denver ProSolo I went up against many well-prepped Civic Si's and I had nothing on them. After the first corner it was all downhill of course.. especially as I was using the same 205/50-15 Azenis 615's that they were. Good times.
http://naufana.com/autox/20060722diaprosolo (videos)

I foolishly thought the same thing this year.  My tC pushes about 163hp at the wheels and weighs about 2800lbs.  Needless to say, I'm finding I need to do a lot of suspension work so I can handle all the weight I'm throwing around the track.  Weight definitely has the advantage over the power, unless you're running on a course with straights long enough to where you can utilize all that power.

---

#12 STS 2007 Scion tC
#24 ITS/DSP 1991 Nissan 240SX