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I recently picked up an 87 S4 and am planning on pulling a mold for the rear bumper to reproduce in carbon fiber and possibly a rear hatch. I currently have a mold that I made for my 78 that I used to make a CF front bumper for as well as a hood.I'm also looking at making a replacement "sunroof delete" panel which would glue on top of the existing roof. (To clarify, it would cover the whole roof and require minimal body work ) I'm looking at producing some parts for the 928 and want to see what the interest might be before I jump in feet first. Anyone have any specific interest in any carbon parts specifically? Not looking for commitments of any kind, just if this would be even worth considering. Pix are of the CF front bumper.
Last edited by Danny Humphreys; 08-16-2018 at 06:14 PM.
Having felt in my hands all the body parts, I suppose the front bumper is heavier than it needs to be. There is more weight to save on the surrounding support structure. Modern cars do not use as much metal as this car does in the bumper bar.
The hatch is steel. It is not light. The sunroof delete roof is not that bad but it could be a 1-2 with removing the sunroof itself and using CF.
Doors are fine. Hood is actually okay, though I do have a CF hood and it is clearly a weight savings.
I would love to see an S4+ CF rear wing. Price dependent of course. Ditto on the kudos for the CF front bumper from your race car. I've always loved that car.
Having felt in my hands all the body parts, I suppose the front bumper is heavier than it needs to be. There is more weight to save on the surrounding support structure. Modern cars do not use as much metal as this car does in the bumper bar.
The hatch is steel. It is not light. The sunroof delete roof is not that bad but it could be a 1-2 with removing the sunroof itself and using CF.
Doors are fine. Hood is actually okay, though I do have a CF hood and it is clearly a weight savings.
Keep in mind everyone, these cars are nose heavy already, removing more weight from the rear (essentially shifting it to the front), could hurt handing.
Just removing overall weight is only part of the equation.
50/50 weight distribution is a marketing gimmick. The best handling cars are tail heavy on purpose.
The modern car most people like to associate to the 928 is the Mercedes AMG GT.
3,600lbs
47%Front - 53% rear
IMO any project to shave weight from a 928 should also focus on keeping the nose as light as possible.
Twin Turbo Todd contributes the speed his car is able to make to proper weight distribution, power is very much secondary. Before he started shifting weight to the rear, his car was nearly impossible to drive at speed, he almost scrapped the project.
See weights here: https://rennlist.com/forums/928-foru...win-turbo.html
His car has 57% of the weight on the rear, similar to many mid-engine cars. This is very much on purpose. He has spent more man hours shaving weight off the front of his car then the engine build, install, and tuning combined.
By comparison, my stock 87 carries 50.6% on the front.
Todd would argue you could possibly improve the handing of an otherwise stock 928 by simply increasing weight in the rear.
Carbon fiber hatch, spoiler, smaller battery.....with nothing done to the front could upset the handling of the car.
Keep in mind everyone, these cars are nose heavy already, removing more weight from the rear (essentially shifting it to the front), could hurt handing.
IMO any project to shave weight from a 928 should also focus on keeping the nose as light as possible.
Carbon fiber hatch, spoiler, smaller battery.....with nothing done to the front could upset the handling of the car.
This —^
There is no ‘should’ or ‘could’ about this. Removing non-trivial weight from the rear only *will* upset the handling. Ask any competent track driver that started with a stock car and then ‘stripped’ it to make dedicated track car. (Obviously, there are mitigations.)
I recently picked up an 87 S4 and am planning on pulling a mold for the rear bumper to reproduce in carbon fiber and possibly a rear hatch. I currently have a mold that I made for my 78 that I used to make a CF front bumper for as well as a hood.I'm also looking at making a replacement "sunroof delete" panel which would glue on top of the existing roof. (To clarify, it would cover the whole roof and require minimal body work ) I'm looking at producing some parts for the 928 and want to see what the interest might be before I jump in feet first. Anyone have any specific interest in any carbon parts specifically? Not looking for commitments of any kind, just if this would be even worth considering. Pix are of the CF front bumper.
"Real" vaccum bagged carbon fiber that requires 2 drill bits to make one hole or carbon fiber cloth with fiberglass resin?
Fair Enough.
Fenders are already light as can be and common. Hood saves about 10 pounds from my CF hood weight compare.
Bumper shocks are heavy. Early Euro has a pipe welded together. Saves a certain amount of pounds.
Aluminum bumper bar is a few pounds saved with holes.
S4 bumper, as mentioned, seems a bit heavy.
Headlight motor
Headlight bar.
An aluminum rad is heavier than a plastic/aluminum one
Fans are heavier than what is made now.
If you consider the center line of the car approx where you sit, then the HVAC stuff adds up (Todd removed that as I recall).
The wiring, for a race car, could be thinned.
Originally Posted by Hacker-Pschorr
Keep in mind everyone, these cars are nose heavy already, removing more weight from the rear (essentially shifting it to the front), could hurt handing.
Just removing overall weight is only part of the equation.
50/50 weight distribution is a marketing gimmick. The best handling cars are tail heavy on purpose.
The modern car most people like to associate to the 928 is the Mercedes AMG GT.
3,600lbs
47%Front - 53% rear
IMO any project to shave weight from a 928 should also focus on keeping the nose as light as possible.
Twin Turbo Todd contributes the speed his car is able to make to proper weight distribution, power is very much secondary. Before he started shifting weight to the rear, his car was nearly impossible to drive at speed, he almost scrapped the project.
See weights here: https://rennlist.com/forums/928-foru...win-turbo.html
His car has 57% of the weight on the rear, similar to many mid-engine cars. This is very much on purpose. He has spent more man hours shaving weight off the front of his car then the engine build, install, and tuning combined.
By comparison, my stock 87 carries 50.6% on the front.
Todd would argue you could possibly improve the handing of an otherwise stock 928 by simply increasing weight in the rear.
Carbon fiber hatch, spoiler, smaller battery.....with nothing done to the front could upset the handling of the car.
08-16-2018, 03:56 PM
Gauging interest in carbon fiber parts
