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Re: Create a Porsche 934 replica in 4 steps

Posted: Mon May 01, 2023 11:29 pm
by XLR8
The new motor is very heavy and changed the car's balance (understeer on corner exit) but I was able to bring it back a little closer to neutral by decreasing rear toe angle from 2 to 1 degree. I like the handling with the new motor but now I'm searching for a bit more speed. After 30 minutes, the motor was only slightly warm so I'm gearing up from 7.28:1 to 6.15:1 FDR.

I also noticed a wear pattern on the rear tires that suggests that it needs more camber angle so I've fitted 1 shim (a washer, actually) to each lower radius rod. The lengthened rod kicks the bottom of the tire out by about 1-1/2 degrees.

I'm back to the tennis courts in the morning. The weather here is shaping up nicely so hopefully I can run the car each day this week.

Big smiles from me; the car responds well to tuning and is tons of fun to drive. :D

Re: Create a Porsche 934 replica in 4 steps

Posted: Tue May 02, 2023 8:42 am
by MarkyDents
Wow what a sharp looking piece you’ve put together here, very very nicely done 8)

Re: Create a Porsche 934 replica in 4 steps

Posted: Tue May 02, 2023 9:17 am
by juicedcoupe
If you like the extra torque and weight of a 550, I have one of these in my Torment.

https://www.integy.com/st_prod.html?p_prodid=39764&p_catid=518&gclid=Cj0KCQjw6cKiBhD5ARIsAKXUdyaVLcm8dBJ6zBlbcY2XA2To2U_ZYrq2iWr5-2KKN6nGwWBwtO3h0fQaApXCEALw_wcB

It has no problem putting a heavy SC truck on it's bumper (or roof).

I bought mine on Amazon but availability is hit and miss.

Re: Create a Porsche 934 replica in 4 steps

Posted: Tue May 02, 2023 5:20 pm
by XLR8
I’m using 4000mah batteries and after a 30 - 35 minute run, the motor is still only slightly warm. The taller pinion gear installed yesterday has yielded an increase in speed but I think there’s more left in that motor - maybe much more. It just needs more gear.

I’ve been running the largest 32dp pinion I have (22t) with a 52t spur for a 6.15:1 FDR. After rummaging through some boxes, I found a 38t 48dp pinion so I’ve paired that with a 78t spur for a 5.34:1 FDR.
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FWIW, that is the largest motor pinion I've ever held in my hands. :shock:
Anyway, I’ll run the car again in the morning. Fortunately, the tennis courts are empty on weekday mornings.
It’s very windy again today and that makes it difficult to tune the car. Tomorrow’s forecast is for sunny skies and calm.

Re: Create a Porsche 934 replica in 4 steps

Posted: Sat May 06, 2023 4:11 pm
by XLR8
The tennis courts were very dusty and slippy - probably a result of the high winds over the past several days. Anyway, the car was faster but much harder to drive on that dusty surface.

It handled the curves fine but the tires would suddenly break loose in a straight section -- the tire spin was completely random.
I had been lucky so far -- not hitting anything -- but eventually the car spun and I was unable to stop before it backed into one of the support posts for the nets.
A wheel is broken, the motor plate is bent and even the chassis plate is bent. :( I’ll order another set of wheels and straighten the bent plates.
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Fortunately, the printed trailing arm has survived the impact. MFJ nylon is very tough.

The bunnies are okay as well. :wink:
im okay.jpg

Re: Create a Porsche 934 replica in 4 steps

Posted: Sat May 06, 2023 5:14 pm
by Frankentruck
Sounds like it drives like a vintage 911 should, on the hairy edge of out of control!

Re: Create a Porsche 934 replica in 4 steps

Posted: Sun May 07, 2023 11:14 am
by XLR8
Frankentruck wrote: Sat May 06, 2023 5:14 pm Sounds like it drives like a vintage 911 should, on the hairy edge of out of control!
Haha… I had the same thought. Although I’ve never driven an actual Porsche, I can imagine how much fun that would be.

I live about an hour from Barber Motorsports Park near Birmingham Alabama. By the way, if you’re ever in the area, you owe it to yourself to visit the park with its world class museum -- you won’t be disappointed. Anyway, Barber hosts the Porsche Track Experience driving school. It’s not cheap (a 2-day class starts at $3,900) but the experience of driving a fast Porsche around that epic track is something I’d never forget. :D

https://www.porschedriving.com/track-experience
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Re: Create a Porsche 934 replica in 4 steps

Posted: Sun May 07, 2023 10:45 pm
by XLR8
The bent plates have been straightened, the wheels re-aligned and it's ready to go again.

I can run those heavy aluminum wheels until the replacement plastic Tamiya wheels arrive.
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Bugs is happy. :D
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