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931 Track / DE Car Reliability
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L Cubed  



Joined: 01 Dec 2013
Posts: 11
Location: AL/GA border

PostPosted: Tue Dec 10, 2013 1:21 pm    Post subject: 931 Track / DE Car Reliability Reply with quote

Hi Guys,

I recently have been doing a lot of reading on the board and other places to help find a car for my wife and I to continue learning and practicing race driving at autocrosses, track days, DE events and maybe even some time trials. I spent 6 years in college working on a Formula SAE car (its a college student built mini F1).



Anyway, working on designing, building and racing these cars was awesome and I'm addicted to racing now! Since I'm no longer at college I need a car I can fiddle with to engineer and also enjoy driving/racing on weekends.

Following Ideola's Project Planning Guide I want to list my goals so that your collective wisdom can help me find the right car

Competitive: I'd like a car that won't be last, I don't need a class dominating car, but I'd like to have a car that with focused good driving might be a threat on a regional/local autocross level.
Reliable: I don't to have to fix the car after every track session. I don't mind doing preventative maintenance and car setup but I would like to have a car that could run a full year of autocross and not need more than oil change, fuel, tires, filters and maybe pads. Be able to drive to and from all events, but it won't be a daily driver.
Fast: I'm thinking 200-250hp with about 2200-2400 lbs vehicle weight. Fat tires for lots of grip >1 lateral G capable.
Mod Potential: I like to engineer and tinker with stuff. I like making slow things faster This car would a learning opportunity as well, such as stand alone engine management and race car setup.
Unique: I like the idea of having a car that's a little bit different.
Cost: I would like to pick up a car that is in decent mechanical shape for less than $2500, preferably under $2000 (there are 2 82 931s near me right now for that price)

So with these goals in mind I think a 931 would be a great fit with the turbo motor and 5-lug suspension, but my research has found conflicting information on the track reliability. Some Lemons racers say they are terrible while some articles here say they are great track cars. So those that race their 924 or 931 can you help me straighten this out?

If you think the 931 doesn't fit my requirements, what would you recommend, a 924 NA or possibly a 944 or maybe something other than a Porsche? (no Miatas though)

Thanks a bunch,

-Luther
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2001 VW Jetta TDI
2013 VW Golf TDI
Looking for a 924...


Last edited by L Cubed on Tue Dec 10, 2013 11:18 pm; edited 1 time in total
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11378
Location: PacNW

PostPosted: Tue Dec 10, 2013 3:03 pm    Post subject: Reply with quote

250 HP is somewhat high strung for a 931 (cue Raceboy. . .he can do it easily), and 2200 pounds is very optimistic for a caged 924.

Thought about a Miata?
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L Cubed  



Joined: 01 Dec 2013
Posts: 11
Location: AL/GA border

PostPosted: Tue Dec 10, 2013 3:14 pm    Post subject: Reply with quote

I have thought about a Miata because I respect them as a very capable car, but I'd rather drive something more unique. I'm not a big fan of convertibles.

I'm not set on a particular power or weight, I just threw out some numbers that I thought were reasonable from what I had read before. Coming from my VW TDI (140hp 3000lbs) cars 200hp at 2500 lbs will still be fast to me and I'm sure good for practicing/learning.
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CÚdric  



Joined: 27 Aug 2004
Posts: 1975
Location: Sweden

PostPosted: Tue Dec 10, 2013 5:43 pm    Post subject: Reply with quote

I think this question is aimed at me , cant resist:)

I started track run my 924 n/a back in 2004 and my 931 a couple of years later, have been on so many track days up to today. But I have never had any big problems (had a wheel bearing go on the n/a once..). Especially with the 931 that I could go through more extensively.

If your 931 is unreliable on track it says more about you as a mechanic than it says about the car . That's how I sum it up after all these years, I have a friend who have had a very reliable track 931 aswell.

My motto is, "do it correctly, do it once". Which had worked perfectly. It sure is a lot more things to keep after than a n/a, which is incredibly easy to get realiable on track. Things on the 931 has to be in much better shape, or else you risk blowing up things, not a surprise since its turbocharged.

What I have done in general:

Engine has had new gaskets everywhere, new heat resistant screws and nuts, cleaned and painted, new hoses and new clutch. Changed the turbo aswell.

I have been running a stock 931 s2 engine (std is 177hp) with slightly larger 2664 turbo from an s1 (early 931), and I let the 0.7 bar spring in the WG instead of the S2 0.65.


All suspension has been down, blasted, painted upgraded to stiffer springs and adjustable ARB from weltmeister. New joints, repacked rack.

Brakes, blasted and painted, Motul RBF600, HAWK HP+ Pads, steel lines. (five lugs, std on ROW cars.) I always keep them the sliding parts lubed and cleaned. New wheel bearing aswell. Have always run on sticky tyres when on track-

New fuel pump, took down the tank and cleaned and painted it, new fuel hoses. wasn't all necessary, but nice to do).

Lots of small things, everything put back on the car is cleaned and painted, new hoses, new rubber isolators, new body seals, lots of small details etc etc. But its not a track car only, so I want it in good shape

And most importantly, keep your tune, I run with Innovate wide band AFR meter to check the full load mixture. Otherwise std CIS injection system and std DITC ignition system.

Have done lots of other stuff, mosty because I want to, not beacause I need to, like a minor gear box rebuild

lots of interior work to make it look nice. And some work on the exterior to keep it decent aswell (need more work there)

You can have a look here, not completely updated though..
http://www.garaget.org/?car=160275


My car was awful when I bought it, it had been standing for 12 years, mostly outside.



For over 200hp I would invest in a larger radiatior and a larger oil cooler. Otherwise you should be fine. 250 would probably need more work. Probably install an LSD and some more tyres. 225s all around on 8" wheels.


Disclaimer, extra emission stuff like on the us cars is not into the calculation. I haven't dealed with that yet, and I never will
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L Cubed  



Joined: 01 Dec 2013
Posts: 11
Location: AL/GA border

PostPosted: Tue Dec 10, 2013 11:16 pm    Post subject: Reply with quote

Thanks Cedric, that is the kind of information I was having a hard time finding. I totally agree with the "Do It Right the First Time" mentality.

One thing I forgot to put in the first post, I need to be able to drive to and from the events but don't need it for daily driver duty. Cedric do you drive your 931 to and from the track?
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CÚdric  



Joined: 27 Aug 2004
Posts: 1975
Location: Sweden

PostPosted: Wed Dec 11, 2013 4:42 am    Post subject: Reply with quote

L Cubed wrote:
Thanks Cedric, that is the kind of information I was having a hard time finding. I totally agree with the "Do It Right the First Time" mentality.

One thing I forgot to put in the first post, I need to be able to drive to and from the events but don't need it for daily driver duty. Cedric do you drive your 931 to and from the track?


Yes i do, thats why i have all the matts and insulation left..as long as its not to hot outside its a pretty ok ride..

Most tracks are within 200 to 400 km away, furthest ive been is 600km away from home for a track day. For the NŘrburgring I put the car on a truck ...

Check out my YouTube channel if you want to see some 931 driving
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Grenadiers  



Joined: 20 Feb 2007
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Location: Nelson, WI & Prescott, AZ

PostPosted: Wed Dec 11, 2013 6:50 am    Post subject: Reply with quote

http://www.youtube.com/watch?v=4TqVkuua4zw
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fiat22turbo  



Joined: 18 Jan 2006
Posts: 4040
Location: Portland, OR

PostPosted: Wed Dec 11, 2013 7:25 am    Post subject: Reply with quote

To be honest. I'd look at picking up a 924S and eventually swapping it over to a 951 powertrain. This way you'd have better parts and service support.

If you've been handed a 924 Turbo for free (which happens from time to time), then I'd look at performing an engine swap before spending a lot of money on the iron lump in the engine bay.

That said, I've dumped a bunch of time and money into the engine bay of my 924 and it has been a fun adventure. However, it isn't something I'd recommend to anyone unless they enjoy tinkering and have a spare car to drive.
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MikeDanger  



Joined: 21 Nov 2002
Posts: 490
Location: Denver

PostPosted: Wed Dec 11, 2013 10:44 am    Post subject: Reply with quote

fiat22turbo wrote:

That said, I've dumped a bunch of time and money into the engine bay of my 924 and it has been a fun adventure. However, it isn't something I'd recommend to anyone unless they enjoy tinkering and have a spare car to drive.


???? isn't that the whole point of the 931????

the 931 is like a bicycle, if you make it 50 miles, turn around and go home, to make sure you get home. if it breaks down, "it was fun while it lasted!"
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CÚdric  



Joined: 27 Aug 2004
Posts: 1975
Location: Sweden

PostPosted: Wed Dec 11, 2013 4:29 pm    Post subject: Reply with quote

Cant really see the reason for going for an engine swap in this case. For 200-250 HP it wont me much of a hassle to run a pretty much std engine.

Engine swap, regardless of engine is a massive amount of work. Havent seen any swap going quick and easy. And you will never be able to put it through the MOT (or maybe you don't have it where you live ), at least not here . But gobs of power is available if you chose wisely.

But for me a big part of the fun is to run a unique car, especially that looks pretty stock. The guys at the Porsche club DE this summer were pretty confused when I lined up after them in the fastest group, behind a row of 964rs, 997GT3rs etc, haha, always fun
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morghen  



Joined: 21 Jan 2005
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Location: Romania

PostPosted: Wed Dec 11, 2013 5:58 pm    Post subject: Reply with quote

fiat22turbo wrote:
I've dumped a bunch of time and money into the engine bay of my 924...


CÚdric wrote:
...chose wisely.


So...dont dump your time and money into a 931 because its not worth it. Instead...choose wisely and you'll have a fast and reliable car.

No dissrespect meant...each and every one of us does their car projects as we know and choose.
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Raceboy  



Joined: 01 Mar 2004
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PostPosted: Wed Dec 11, 2013 6:53 pm    Post subject: Reply with quote

Rasta Monsta wrote:
250 HP is somewhat high strung for a 931 (cue Raceboy. . .he can do it easily)


I have done it on several cars and while it is not the same as changing tires, it is certainly not something to be considered as extremely difficult.
But I have never done it with CIS, perhaps it is really difficult with it.

Perhaps you need to know what and how to do, then it would not look so difficult, or even impossible?

Also, are you referring to DutchPug also? Seems that he also did not struggle too much getting good power out of 924 NA (!), but rather how to get the clutch to hold up.

Rasta, prick as usual.
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CÚdric  



Joined: 27 Aug 2004
Posts: 1975
Location: Sweden

PostPosted: Wed Dec 11, 2013 9:10 pm    Post subject: Reply with quote

When you look at 931 car projects make sure you compare apples and apples. Driving around the streets with occasional full throttle bursts and skids is not the same as driving full throttle on track (espesially not if you are a fast driver, and two persons sharing the car on the track days (which I do with my wife)), including the reliability you need to be able to drive 300km back home. Its demanding for any car, especially with a higher tune. Some of us here do some track work, some dont

I think in the nurburging vid above Im about 45 seconds or something at full power up the hill after bergwerk. Kind of hard to do around town
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Carrera RSR  



Joined: 08 Jan 2010
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PostPosted: Wed Dec 11, 2013 10:16 pm    Post subject: Reply with quote

Rasta Monsta wrote:
250 HP is somewhat high strung for a 931 (cue Raceboy. . .he can do it easily), and 2200 pounds is very optimistic for a caged 924.


Mine is circa 220-240bhp and 1100kgs/2400lbs. Yes highly strung!! Yes expensive to get to this end. Yes could be a touch lighter, but it is what it is. Lots of fun on fast road runs or occasional track use
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Then www.924board.org/viewtopic.php?t=31252
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morghen  



Joined: 21 Jan 2005
Posts: 8164
Location: Romania

PostPosted: Thu Dec 12, 2013 12:12 am    Post subject: Reply with quote

I really need to dyno mine...
The K27 at 1.1bar and AFR12 should make some power i guess.


Carrera RSR wrote:
Rasta Monsta wrote:
250 HP is somewhat high strung for a 931 (cue Raceboy. . .he can do it easily), and 2200 pounds is very optimistic for a caged 924.


Mine is circa 220-240bhp and 1100kgs/2400lbs. Yes highly strung!! Yes expensive to get to this end. Yes could be a touch lighter, but it is what it is. Lots of fun on fast road runs or occasional track use

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