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Porsche 924 Racecar Build Thread (AAN Conversion)
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11723
Location: PacNW

PostPosted: Thu Apr 15, 2021 6:43 am    Post subject: Reply with quote

Unreal, I had no idea you were such a serious fabricator.

What would it take to get some seat time in this beast? I neither crash nor break stuff and am a good and cheerful mechanic.




James
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  • WeiBe (1987 924S 2.5t) - 931 S3
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924RACR  



Joined: 29 Jul 2001
Posts: 8794
Location: Royal Oak, MI, USA

PostPosted: Thu Apr 15, 2021 8:51 pm    Post subject: Reply with quote

Nice work on that splitter - saw some composite building pics on FB, looked like you were up to some fun stuff!
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Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype
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running_cold924  



Joined: 27 Dec 2005
Posts: 65
Location: Bedford Pennsylvania

PostPosted: Wed May 05, 2021 11:57 pm    Post subject: Reply with quote

seriously good work. I contemplate this swap myself...as I will have access to a good running (full rs2 spec) AAN here in a few months.
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1979 Porsche 924 n/a with dual Mikuni's(sold)
1987 Porsche 944S, chipped (traded)
1986 Porsche 951, Vitesse MAF, 83lb injectors, 3 inch exhaust, Garrett turbo (sold)
1892 Porsche 931, sport seats, mostly original but not running
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Britain  



Joined: 26 Nov 2013
Posts: 285
Location: Cornelius, OR

PostPosted: Wed Aug 18, 2021 6:55 am    Post subject: Reply with quote

The year has gone by quickly and I just now realized that I haven't posted any updates in a while...and let me tell you there have been several small and huge updates.

First off is the new front suspension. We were running '86 turbo front spindle modified to lower the roll center (ball-joint spacer) and an adaptor for a set of custom rotors and 996 calipers. This set-up worked great, but was a bit fragile with wheel to wheel contact or wheel to tire barrier contact, and the parts are getting a bit harder to come by.



Therefore I decided to embark on adapting a set of 996 front uprights to the car. These are stronger, hold a much larger wheel bearing, and we could mount the calipers right up. Amazingly, the majority of the critical measurements were the same or within the ball-park of the '86 turbo spindles. The 996 is rear steer so they had to be flipped side to side, but everything else could be accommodated to work.

This is the '86 spindle sitting over the 996 upright for reference:



I had to modify my control arms for a larger ball joint bearing and mount it at a slight angle to match the 996 control arm.



Here is the upright mounted to the control arm:



I was able to use the same shock set-up from Ground Control, but I had to get a new set of strut tubes and modify them to fit the new set-up.



Here is the set-up mounted to the car. You can also see here the drop-link needed for the toe-link to get the bump-steer dialed in.





We couldn't be happier with this new set-up. I was able to get 4degs of caster dialed in and over 3degs of camber with adjustment of both the control arm heim joints and the upper camber plates. The steering feels solid, the turn-in is great, and the brake feel is tremendously improved. This also gives me ABS rings on the front for future addition of ABS to the car.
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Britain  



Joined: 26 Nov 2013
Posts: 285
Location: Cornelius, OR

PostPosted: Wed Aug 18, 2021 7:07 am    Post subject: Reply with quote

Another big focus this year has been on aero. The previous set-up worked ok, but as we started making changes we saw our top-end speed decrease slightly, but our overall laptime drop significantly. We also improved tire wear and drivability with more cornering grip.

I am not completely done with the changes I want to make, but I first started with the splitter.

First step was to get the main element sized up on the car. I used a piece of 1" closed-cell insulation foam for the core. I am sure some people have various opinions, but I think it works great.



I also planned to add some tunnels to the front splitter so I built a buck for those out of foam as well.





Lots of sanding, paint and a little vacuum bag action later, we had tunnels ready to go.







Up next was the resin infusion of the splitter core.





And then mounting of the tunnels and supports.



Mounted to the car...which was actually done for the first time in the garage at Sonoma since I finished it only hours before we left for the race.

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Britain  



Joined: 26 Nov 2013
Posts: 285
Location: Cornelius, OR

PostPosted: Wed Aug 18, 2021 7:14 am    Post subject: Reply with quote

During testing at Pacific Raceways, the car had a little bump in the wall which bent the rear wing upright and tweaked the rear bumper. I had always wanted to build a fiberglass version to knock off some weight and also give me a mold to make more if needed...so it was time to get it done.

I should of made it a two-piece mold to make it easier to demold...but whatever it worked and saved over 10lbs if I recall.



Mounted to the car.



And slotted for the trans cooler air outlet and toe-hook. Still need to paint it.
tra
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Britain  



Joined: 26 Nov 2013
Posts: 285
Location: Cornelius, OR

PostPosted: Wed Aug 18, 2021 7:19 am    Post subject: Reply with quote

Couple of cool shots of the car from racing this year.







Taking the inside of Turn2 at Sonoma.



And battling Randy Pobst in his Civic at Sonoma. He is always fun to run against.

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morghen  



Joined: 21 Jan 2005
Posts: 8868
Location: Romania

PostPosted: Wed Aug 18, 2021 4:21 pm    Post subject: Reply with quote

Amazing, thank you for sharing!
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Britain  



Joined: 26 Nov 2013
Posts: 285
Location: Cornelius, OR

PostPosted: Sun Jan 02, 2022 4:46 pm    Post subject: Reply with quote

With the 2021 season now over, it is time to get caught up on the build thread. It was a long season that saw a few DNF's, a couple of overall victories, and definitely a lot of changes to the car to address those pesky little issues that can end your race early.

We have had a handful of coil-pack failures over the years, mostly due to heat. During a race at ORP, we had the v-band for the exhaust fail and cook a couple of coil-packs. Instead of continuing to stock up on the Audi R8 coils, we decided to do a conversion to LS coils mounted remotely.

The coils are mounted where the battery used to go and we used 964 spark-plug ends to fit down inside the valve cover. We also built a retainer that bolts down and keeps the spark plug wires from popping off.







Going further down the path of removing parts that are unobtainable, obsolete, or just plain 40 years old...we had to address the rear wheel hubs. We were running '86 turbo (one year only) hubs and they have failed in a couple of occasions. The flange is super thin and they crack along the stepped edge. Now converted to BoxsterS/996 rear hubs which are much better design. These paired with 996 rear rotors puts us on stock 996 rotors all around. Had to modify the caliper mount to accommodate the different rotor offset (printed on 3d printer to check measurements) and had to modify the fenders as these kicked the wheels out 12mm on both sides.







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Britain  



Joined: 26 Nov 2013
Posts: 285
Location: Cornelius, OR

PostPosted: Sun Jan 02, 2022 4:57 pm    Post subject: Reply with quote

In between all of the other work to the car...I started working on some serious aero updates in April and it wasn't till November that I had them done.

The first step was to create some functional side skirts. I mocked these up with 2x4, some purple foam, and bondo on both sides of the car. The goal here was to basically shield the rear tire. I then got them painted and sanding smooth I could pull a mold off each side.









With the side skirts made in carbon, I now needed to figure out how to jack up the car during a race without damaging the carbon fiber bits. Basically there is a 1.25" DOM tube running thru the body and welded to the frame rail. I also added some triangulation to the cage on all four corners to prevent deflection. These DOM tubing receivers use some rally style jack stands that I built.











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Britain  



Joined: 26 Nov 2013
Posts: 285
Location: Cornelius, OR

PostPosted: Sun Jan 02, 2022 5:04 pm    Post subject: Reply with quote

With the side skirts done, we needed to redo the diffuser to fit the master plan. The previous diffuser was out of aluminum and while it was not too heavy...it was not light either. The new diffuser is out of carbon with a 1/4 foam core across the top. It also hugs the G31 transmission nice and extends all the way forward to the torsion bar tube.

We started with foam and built up the shape out of a lot of bondo. It was primed, painted with some spare paint I had, laid up with carbon, foam core, and some mount plates, and then resin infused carbon.













The final result was impressively light and fit perfectly.



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Britain  



Joined: 26 Nov 2013
Posts: 285
Location: Cornelius, OR

PostPosted: Sun Jan 02, 2022 5:13 pm    Post subject: Reply with quote

With the main portion of the diffuser done, I wanted to continue it forward with a separate panel so we could access the transmission if needed. Same process, although much quicker, to make this panel and finish it off.









To ensure I wouldn't have to do this again, I made a mold off the diffuser just in case something gets damaged. I was also able to use this same mold to make the strakes for the diffuser.





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Britain  



Joined: 26 Nov 2013
Posts: 285
Location: Cornelius, OR

PostPosted: Sun Jan 02, 2022 5:17 pm    Post subject: Reply with quote

The final step to finish off the aero upgrades was to finish off the flat floor. I laid this out in four panels, both the make them easier to lay-up and to make it so they could be replaced in case of damage. I made template out of lightweight foam, translated that to divyncell foam core, and resin infused carbon. Each panel is about 2lbs and hang from the floor from simple brackets.









And here is the final race ready package.





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924RACR  



Joined: 29 Jul 2001
Posts: 8794
Location: Royal Oak, MI, USA

PostPosted: Sun Jan 02, 2022 10:53 pm    Post subject: Reply with quote

Wow, very nice work!! That is some serious aero, you'll be liking it!
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Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype
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peterld  



Joined: 10 Dec 2006
Posts: 946
Location: Noosa Heads QLD Australia

PostPosted: Sun Jan 02, 2022 11:43 pm    Post subject: Reply with quote

Wow!!!
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