Question for all the HWFM Racing Pros.....

I do not have plans to track the car.......yet.

However, I am interested in how much weight I would need to shed in order to "feel" more seat of the pants power during hard street driving.

What would do it ? 50lbs, 75lbs, 100lbs ??????

What would be the best way to shed the weight without drastically altering the car ??? I know...I know....ambiguous question at best.

Thanking all in advance !!!!!!

 

It's all about power to weight ratio

If you lose 5% of the car's weight, your P:W goes up 5%

The same ratio increase could be achieved by adding 5% power.

So either lose ~70kg (154lbs) or increase power by 13hp

Of course, choosing the lightweight approach has the advantages of improved handling and braking too.

Choosing the additional power route means higher potential top speed.

I suggest doing both

Whether 5% is the right figure for you to make a noticeable difference is a subjective thing.

 

As for seat-of-the-pants feel, imagine driving your p-car solo and realizing you need to make a quick stop because the light suddenly changed at an upcoming intersection. Phew! Close call, right? Now imagine the same emergency maneuver with a passenger. Now add a few more people in the back seat. Each person you add requires you to apply more brake force to stop the car--that's what extra weight feels like at the track.

The difference is that you'll be travelling at much higher speeds at the track and even the addition of a single passenger will affect the way in which you brake. Also acceleration and cornering speeds would be impeded but those changes are more subtle.

Around town, it's difficult to feel the impact of removing 50-100 lbs unless you are really pushing it. Knock off 200 lbs and maybe you'll start to feel a little more pep.

0.02

 

There is a general forumla, for this...
and that is how G-Tech calculates hp.

given vehicle weight, g-force and speed (by analyzing g-forces) in a timeframe. it calculate Pwer(hp)

Power = acceleration * speed / mass
Torque = power / rpm

So some derivatives and calculus will get you the answer you need

[edits] more formula I found off the web
force = crank_torque * gear_ratio * FD_ratio / wheel_radius

 

I think you'd need to lose about 200lbs in a 993 to notice a significant difference. Lighter cars are more easily improved with weight loss, but since the 993 starts off fairly heavy, it takes a good bit to make a significant difference (percentage wise, I guess). Question: How much difference can you feel with a passenger? That should answer your question (assuming you're not too shy to ask the weight of your passenger )

 

re weight saving...i was thinking the same thing ...starting with seats....recaro seats come in at approx 6.5kg (14.5 pds?)....does anyone know how much the standard electric seats weigh??...ie switching to 2 recaro's how much weight wud u save...as a guess??

 

I did a search for the thread where I thought it said 1HP=20#. In any case for those numbers, I am not willing to forego comfort to put myself or my car on a diet.

 

Just do a search for posts from poorb0yw .
He is the resident expert on weight loss since his car stands now at a scant 2500lbs....
He has a couple of posts where he lists exactly the weight of the parts he removed.

 

sorry...found it in search...standard seats weigh 62lbs...cheers

 

Each of my stock 4-way power seats weighed 47.5 lbs according to the post office scale. I guess if you have the fully optioned 8-way powered seats they might weigh about 60.

 

A standard 993 has a power to weight ratio of 3100lbs/282hp = 11lbs/1hp

Loose 200lbs and it changes to 2900/282 = 10.28lbs/hp. A significant change but not earthshattering...

You could add about 18hp to the stock weight and get roughly the same increase.

My suggestion is to loose the weight AND do the RS gear ratios/LWF. Your car will feel like it has gained 40hp.

 

i have my Speedster at 1100 Kilos (about 2350 lbs i think ),and with 993 Motor/trans ( G50/21) .It is a total different Car and it feels like a RS ,maybe a little faster . The handling is amazing ,and the Standard Brakes (C4 set up ) are as good as the Big Reds in my 993 TT .
To me the Weight loss thing is the best way to make your 993/964 feel like
a Porsche .
harald

 

Did I hear someone say the muffler by-pass looses 60+ lbs, AND adds 20+ hp?

If so, gotta be the BEST bang for the buck.

CP

 

I remember driving my dad's 1969 Lotus Elan. 115hp, 1500 lbs.

You could feel a difference when you filled the gas tank.

Lovely car.

 

I've taken almost 300 lbs off and that I can easily feel.
I thing you feel it more in braking and cornering than accelerating (it does accelerate better too, just that the cornering change was more significant, or maybe I'm just biased more in cornering than accelerating).

I'd say about 200 lbs is something you'll definitely feel; you can "test" it easily, have someone sit next to you at track during session and then leave him to the pits in midway of the session and feel the difference...