993 Rear Suspension Conversion Revisited

[RX-78 Gundam]

After looking through some threads on here and Rennlist about the 993 rear multi-link suspension conversion for the older cars, I'd like to revisit the topic for my personal car.

Seems the sentiment was that it wasn't worth the price/trouble or it would be difficult to set up correctly + more expensive to maintain. Saw a few people posting about how much better their cars handled after the conversion, but it always came back to how expensive the conversion was.

There's a fabricator local to me that has done three of these conversions for race cars and has one more set of 993 suspension available. He is offering a pretty good price ($10k parts and labor) for the conversion.

This will be for my weekend track toy 911 that I bought already as a mish-mash of different eras (1976 chassis w/original 915 transmission, 1987 3.2 engine, steel turbo flares along with box rockers). I intend to have it still be streetable, but would like it to be more track-focused (HPDEs, time attack, etc).

A couple of concerns I have is:

1) He stated that the car needs to have a G50 transmission because the axles on the 915 are too small. Would like to keep the 915 for now if there's a way to make it work.

2) He doesn't do it on a jig, but says he takes a lot of measurements. I understand this is probably a one-shot deal with fabricating, and feel like it might be risky.

3) While I'm sure my skill levels may never reach the levels to fully take advantage of something like a multi-link rear suspension, I do want to see where I can push the envelope on this project as I'm leaving my other 911 pretty much stock in the suspension department.

Any advice and personal experiences relating to this dilemma would be much appreciated.

[Elombard]

I would just go 935 rear suspension. Its bolt on except for reinforcing the shock towers. Most of the benefit - way less hassle. Also a more desirable car for long term re-sale in the end.

With your flares you can run big tires and with the high end shocks and tires available now you can get it dialed in with all of the info available. You can have a very high grip rear with a reasonably compliant street ride.

If you were running super high horsepower the equation might change but with just a 3.2 its not an issue IMHO

[RX-78 Gundam]

Thanks Erik! That sounds like a great option without the fear of messing things up permanently or creating even more headaches in the future.

What would you say is the number for super high horsepower? I do want to eventually turbo the 3.2 when rebuild time comes (after suspension, brakes, and everything else is sorted out). With the street car in mind, I'm thinking the upper limit would be 400 whp - and that's a very optimistic number in mind, I'm sure (for a street car).

[75 911s]

Plus one for 935 suspension, or you might look into coilover setups like the KW system or Elephant. The 993 conversion sounds like a really bad idea. Also, your guy who's done 3 of them is recommending a g50, which means more tub work. These seem like options better suited for a race tub, not a street car.

I looked into Turbo-ing my 3.2. It's certainly an option, but you have to factor in everything beyond the motor. Especially the trans. From my understanding, you would need to reinforce the 915 or just really baby it with a turbo, lest you grenade it.

You mentioned suspension upgrades so you are already factoring those in. Brake upgrades might be a good idea too. The turbo seems to open up additional slippery slopes to fall down. :-)

[Elombard]

For me the air cooled motors are too rare and special to do aftermarket turbo stuff with. For the investment you will have maybe just buy a turbo 911? The Porsche engineers designed the NA motors to work a certain way and I like to maximize what they did by removing some of the compromises they had to build in for fuel efficiency, emissions and noise for a mass market. Nice thing about air cooled Porsches is you can see what these compromises were by looking at the race cars from the period and copying them.

A light weight, car with a nice suspension and a 3.2 with headers is a very fast fun car that is pretty reliable and fairly easy to maintain. If I wanted to go nuts with horsepower and chassis mods I would pick a newer and more common platform.

[Tremelune]

Originally Posted by Elombard

For me the air cooled motors are too rare and special to do aftermarket turbo stuff with. For the investment you will have maybe just buy a turbo 911?

This is getting off topic, but there are people getting over 300hp with a twin-scroll turbo at half bar for $3k in parts:

adding turbos to a 3.2

[RX-78 Gundam]

Appreciate the feedback, gentlemen. I'll do some more digging into those suspension routes.

As for the engine, hopefully it'll be another year (fingers crossed the engine doesn't have any major issues) before I get to rebuilding/modifying it.

Tremelune - subscribed to that thread! Thanks for the heads up.