Trakrat

Hi All,
I've been searching the threads here and haven't really found a specific answer to my question. So thought I'd post it here.
I'm looking at converting a Carrera 3.2 into a steetable track/auto-x car.
In previous production cars I've owned... reducing weight was always an easy way to get better power to weight ratio.


Nonetheless, adding power may be a quicker method to get better performance from the car.


So my question is... is it worth spending money on getting lighter seats, smaller batter, replacing body panels with aluminum or carbon fiber and taking out all the unnecessary weight (spare tire, etc..)
Or should I focus on adding power and better suspension and not worry about the weight difference?
Reducing weight AND adding power and agility is the ultimate goal... but I want to start with one thing at a time to evaluate the changes to methodically approach the ultimate goal whil also gradually raising my driver skills as I raise the limits of the car.


Suggestions to start off with? weight reduction or power mods?

JonSnow83

Do not remove the spare on a 911! Essential to the front crush zone.

r911

That's an old rumor - but is it true??

Weight reduction enhances every aspect of performance, including acceleration, braking, cornering, and more. Power only affects the first.

I'd put fiberglass on the rear for sure, and remove all luxo stuff you don't need or want.

73911

It sounds as if you want to spend money.

The best return on your money would be a driving coach and a data logger. Ask around about who might be the best coach in your area and then buy a data logger that he recommends.



Data loggers 101

Richard Newton
Historic Racing Images

Trakrat

Thanks for the replies.
Driving coach is not needed... trust me on that one.
Just trying to get a little more responsiveness out of a 30 yr. old car. I've seen some threads where the owner was able to remove ~400lbs. from the car. That's pretty impressive. I don't want to gut the car completely to race trim... but I plan taking out things that I won't use.
I'm not too familiar with power mods.. but getting rid of weight first sounds like the best plan... then moving to suspension mods next.
I've read that ALOT of owners get the 911 chip put in... I might do that as well as a bypass muffler w/ cat delete.

JonSnow83

True! Just search on Pelican for some reading fun. Weight in the back makes a bigger difference anyways. I'd rather never have to find out, especially the hard way.

r911

hollow torsion bars can help, esp. if you plan to move to a different spring rate anyway

911Dave

Lightening is far easier, cheaper, and faster than modifying the engine for more power. And, as stated above, improves every aspect of performance instead of just acceleration or top speed.

When lightening, you'll find that most of the opportunities for lightening are to be found in the front half of the car....which is the WORST place to lighten, because you'll make the rear weight bias even worse if you start removing heavy things from the trunk, fitting fiberglass hood and fenders, moving the battery to the smuggler's box, etc. The only thing I would do to the front is replace the front bumper with a fiberglass one, which will improve steering responsiveness a bit due to reduced polar inertia. Concentrate on reducing weight in the rear, which will help with the balance of the car and improve handling. Replace the rear bumper and deck lid with fiberglass, remove the rear seats, rear panel and sound deadening material. Do whatever else you can to remove weight BEHIND the center of gravity, and don't forget about getting some light track wheels and tires to reduce unsprung weight, which is the most heinous weight of all.

r911

Here is what the experts think:

Light Weight Quotes

"The lighter you make the car, the less weight there is to brake for a corner, to take around the corner, and to accelerate from the corner.”
- Ferdinand Piech, speaking to Michael Cotton, in Classic Porsche, 1991, p. 10.

“A small, light efficient car to surpass the performance of large, powerful cars attracted us.”
- Ferry Porsche on the genesis of the firm, quoted in Road & Track 25(12): 102 (August 1974), 25 YEARS OF PORSCHE by Ron Wakefield.

“a small car with abundant power and adequate brakes not only can accelerate very rapidly but also has stopping ability to match its performance. The result is a high evasive capability....”
- Ferry Porsche, 1976, We At Porsche, p. 236.


"Weight saving should be by design and not a post process. Weight is the car designer's biggest enemy. It works against you in every single aspect of vehicle dynamics."

"Achieving a good power-to-weight figure by applying huge horsepower to a heavy car is in no way the same thing as achieving the same ratio with a light car."

"For me, car design _is_ packaging. To create something truly forward-thinking, a designer has to challenge the accepted major component placement in an automobile."

"I have a "real-world" checklist when designing road cars:
1. size or perceived size; is the car intimidating to drive?
2. ergonomics; primary and secondary controls, pedals
3. luggage capacity, cabin storage
4. drivability, slow traffic engine characteristics, overtaking
5. ride and handling
6. ease of parking"

Gordon Murray -- ?? R&T article
Road & Track, January 2005, p. 65

RaceDevelopments

You can kill 2 birds with 1 stone with the exhaust system....more power, less weight. Just don't go too big on the piping.

Next, spend money on brakes and tires. Then suspension.

I would focus on taking weight out of the rear end first, worry about a lightweight battery and carbon panels last. The return on investment just isn't there.

Amber Gramps

I turned a lowly cab into a demon over the course of the last 10 years. The pictures that are on my desktop tell some of the story, but not all.... I'll try to take a few more after my visit to the Porsche Experience tomorrow.

Spring Rate Is 21/28 or perhaps a bit more in the back.

I'll try to remember my list of "Delete" then give you a list of things I replaced the deletes with.

Deleted:

Rockers
Rear Skirt
Muffler
Bumperettes
Tail Lights
Steel Decklid
Plastic Grill
AC Condensers, Hoses, Etc..
AC Pump, Accumulator, Etc..
Heater Blower
Footwell Blowers, Covers
Fresh Air Box, controls
Auto-Heat Control & Flapper Boxes
Center Console
Central Locking
Door Cards, Pockets, Etc...
Sport Seats
Back Seats
Carpet
Water Bottle, pump
Clock
Steering Wheel
Engine Sound Pad

Now I'll attempt to give you a list of things bolted on in place of parts removed and try to do it in the order of the list above and give you the name of my source.

Replaced with:

Pulse Chamber - Bisimoto
Welded bumper - Craigslist
69R Tail Lights - TRE, Rallylights Dotcom
Fiberglass Ducktail - Dude in Colorado
Mesh Grill - Ebay
Heat Blower Bypass - Pelican
Footwell Blower Bypass Ducting - Aircraft Spruce
Manual Heat Pulls - Einmalig
Manual Flapper Boxes - Craigslist
R/RSR Door Cards - AppBiz
Sparco Evo III - Einmalig, Sparco, Local Leather Upholstery
Perlon Felt Carpet - AppBiz
Turbo Water Bottle - Rennlister
Clock Alternator Light - TRE
Prototipo - Pelican

Other Cool Stuff:

Strut Brace - TRE
930 Brakes - Einmalig, Partsgeek
Front Hats, Rear Caliper Mod - Rebel S
Rear Coilovers - Rebel S, Bilstein, Falkner
Cebie Bi-Oscar Lights - Craigslist
Yellow and Rainbow Zinc Plating - Einmalig
Turbo Tie Rods / Adjustable Droplinks - Pelican
H4 Headlights, Relays, Euro-bulbs - Rennsport Systems
R Compound Tires - Tire Rack
Bump Steer Kit - Pelican
Multi-Board Chip -


Every part that came plated that I've touched in the last many years has been replaced with a freshly plated part from Einmalig. From spring plates to fuel rails they've all been swapped out at Einmalig for identical parts that have fresh plating....I've saved a fortune...literally.

Yes, I did say coilovers. I was quoted $800 and a six month wait for new 28MM Sanders T-bars....screw that. I took a set of old worn Bilstein Sports I picked up for cheap and took them to Bilstein in Poway and had them rebuild them to match 28MM to 29MM T-bars and gave them the weight and purpose of the car and they are perfect. So in addition to my stock T-bars I have a 150#, 80#, and 4# coilover set up in the back.

Up front I replaced the Boge struts with Bilstein struts with matching re-valved inserts... Again everything from camber plates to control arm hardware is all freshly plated and all rubber was replaced with stock rubber from Elephant Racing...

I've done all the work myself. EVERYTHING. Yes, I painted the ducktail and the bumper myself. I even went so far as to weld up my own string jig so I can do my own wheel alignments.

....and for all the guys that get butt hurt over my car.....KISS ME!!!! You obviously have not gone for a ride in it. To get an idea of what it's like to drive my car just think back to the first time you did your favorite thing...then multiply that by 11.

In short, this is that car that weighs 400 pounds less than the sticker in it's door jam says it weighs.

https://www.instagram.com/p/BFSRl5Yv...bisimoto&hl=en

mjonzo911

This is an old list and I'm down to 1056kg now but this gives you a good idea of how much weight can be taken out of the car. My car feels night and day different to how it did when I first got it, losing weight makes so much difference to the car on track and road in handling, acceleration and braking, well worth it in my opinion. The car feels so much more alive, like a proper sports car.

My Car starting weight = 1220kg (official calibrated weighbridge)

Weight loss so far:-

Spare wheel - 15kg (replaced with tyre inflator can)
Jack & tool roll - 7kg
Rear wiper & motor - 2kg
Rear seat uprights -7kg
S/steel TT exhaust replacing stock - 10kg
Front Recaro seats replacing stock electric - 32kg
Dust shields on brakes - 2kg
Rear f/g ducktail replacing stock whaletail - 14kg
Rear firewall soundpad - 5kg
Front carpet mats - 2kg
Rear bumper/muffler heatshield - 1.5kg
Stock 'Bosch silver' battery(18kg) replaced with Oddyssey(7kg) = -11kg
rear seat belts - 1kg
Rear seat-base soundpad - 7kg
Front door trim with pockets & arm rests - 5kg (for the pair)
Old carpet and rear trim = 11.75kg? (new RS carpet weighs +3.5kg)
16" wheels replaced by 15" = -4kg (R Rubber equalised weight more than expected, with road tyres would be bigger saving).
Bumpers replaced by f/g =
Ali front bumper minus all trim = 7kg Fibre glass replacement = 1.6kg
Rear blade minus trim = 8kg, Rubber over-riders = 2kg Fibre glass = 1.2 kg
Total saving 14.2 kg

= 147.75kg lost leaving 1072kg as car was 1220kg to start.(weighbridge weight)

Yet to be taken off total:-

Flag mirrors swapped for Vitaloni Sebrings = 4-5kg
Side sills removed - 4.5 to 6.5kg

73911

I love Bilstein in Poway. They're great people and they're also very reasonable.

Richard Newton
911 Tie Rod Ends

NineMeister

In order of priority:
1. Weight reduction (as mentioned above, increases all of below)
2. Lateral g - think cornering grip
3. Braking performance
4. Acceleration

Note that item 2 is most influenced by the height of the centre of gravity, hence why eliminating the sunroof and fitting lightweight thin glass (or plexiglass) is top on every race car build list.
Note also that I have used the term acceleration, not power as there exists many powerful dyno engines that do not accelerate quickly. It is very important to consider the drive train as a whole when considering how to increase acceleration.

Trakrat

Thanks so much for all of your replies!!!

What do you all think of switching out the rotors/brakes and wheels for additional weight savings?
Does anyone make carbon ceramic brakes for these cars?
Anyone researched which wheels would reduce weight as well? I'd like to move to 17" wheels, but basically just need more meat on the car. However, if staying with 16" shows HUGE weight savings, then I would probably stay at 245/205 wheel combo.