I know you race car guys have real world experiece with this stuff. I have a 73 1.7, and I want to add a half-cage and A/c, so I would have to pick up about 20 hp or drop 200 lbs to do this, to keep performance similar to where it is currently- is this possible in a street driven car? can lightweight panels and some removal of non essentials accomplish this? any input very welcome

I don't have the direct answer to your question, but I can tell you that a 200# passenger costs us at least one full second on a one minute a/x course.

Can I find 200#'s of unneeded weight in my car? I don't think so.


KT

Depends on how you define needed! You'd be suprized at how much weight is still left on your car.

OK whats the list again? Remove floor tar, remove heavy pads from inside the engine compartment and behind the back pad inside the car, remove backpad and use lightweight carpet, replace heat exchanges with headers and lieghtweight muffler, remove muffler shield, replace all hoods, bumpers, valances rocker panels with lightweight fiberglass, pull bottom piece of dashboard out, install lieghtweight battery, look for unused equipment, etc.

I wrote this up in my blog....

This question has been asked several times recently so I thought I would post all the things you could do so I can just cut/paste when it is asked again.

First you need to realize that making some of thse changes will change what class you run in at your local autocross. And if it is a street car, these will effect the safety of the car. Steel saves lives- fiberglass saves weight.

1. Change the hoods, bumpers, and valances to fiberglass.
2. Switch to a lightweight fiberglass targa top.
3. Change the glass to polycarbonate
4. Remove the carpet, backpad, pass. seat, sun visors, console,
5. Remove the sound pad from the engine compartment
6. When you change the hood to f/g remove the springs and hardware.
7. Remove the fresh air fan from under the front hood.
8. Replace the heater boxes with a header.
9. Remove the windshield washer system
10. Remove the headlight motors and assocated stuff
11. Remove the arm rests from the door panels
12. Change to early doors w/o the steel beam
13. Remove the door windows and cranks.
14. Remove the heat shield which is over the muffler
15. Remove the sound deading material and any undercoating
16. Remove the seam sealer that cover the welds in the trunks
17. Some think f/g rocker panels save weight over the stock ones. It is true they are lighter but not by much.
18. Aluminum wheels.
19. Racing slicks are at least half the weight of a street tire.
20. Install a racing battery. Saves 15-20 pounds easy.
21. About half the wiring can be cut out.
22. Remove the cover plates from the back side of the brake rotors.
23. Grind/cut off all the brackets/bolts/tabs/ etc that are everywhere on the car.
24. Remove glove box and door.
25. Install f/g door skins

I street drive my car for now

But I run in a class that allows weight cutting up to 100 lbs, below factory listed weight for the car. Nobody really challenges me yet on this one. So What I do is balance it out. I add something, I take another item out. It is sort of a catch 22 thou. Why you ask, I have no windshield washer fluid so if I blast through a bunch of muck, I have to stop and clean the windshield. Maybe I need tear-offs for the windshield. Next round inner log reinforcements means I might remove head light motors. So I will have a couple gas struts, pop them up, and a latch on a string to keep them down. But you know I use head lights more than heat, blowers, hell I never touch that crap.

BTW, you forgot the loses that the AC system will place on your motor also. You might want to add a switch to disengage the AC pulley when you reach a certain throttle position. If it is one of the original 914 AC kits you will notice it. Heck I notice it on my Jetta TDI, and it has a lot more HP and torque than what you are running. You could upgrade the compressor to a roatary style unit, much less parasitic drag. You will still notice it thou.....

Adding a cage will improve handling even with its added weight, as the entire car gets stiffer.

After that follow ury's instructions

As to your original question, I would say pretty close but only for acceleration. Cornering is another matter as is braking where stopping the extra weight will cause much added heat depending on the weight of the car. Lotus cars come to mind, less is better!