924Board.org

[jacobroufa]

Happy new year! What's everyone got planned for '21?

I just got my PCA annual calendar and it looks like my first DE event will be Friday April 23rd. So I've got almost four months to get the 931 into shape. I decided that the Weissach took too much of a beating on the track last year and I'd really like to keep it as a nice weekend driver. The 931 will be much faster on the straights, which will help me a great deal at Blackhawk -- the closest track to me.

So on my must do list prior to 4-23 is:
* get 2nd gear back and reinstall transmission (currently partially disassembled in my basement)
* refresh half shafts (new CV boots and new bolts)
* refresh front suspension and get alignment (have new struts and top bushes, need to buy a-arm bushes)
* reseal waterpump -- it never stopped leaking on me last year
* sort out headlight issue (motor sticks, lights don't turn on)

If I get all that done I'll be terribly happy. My bonus list is:
* plumb in boost controller
* mount early manual mirrors

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After I've got it back to driving condition, I'm not sure what comes next.. What sort of suspension modifications will still give me decent streetability? What sort of track modifications should I look to make?

Mostly I just want to get back on a track. I know more seat time will improve my driving more than any car modification.. Really looking forward to this year.
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1980 Porsche 931
1981 Porsche 924 Weissach

[924RACR]

Good shocks and uprated swaybars will tend to improve track handling with the least impact on streetability. One of the toughest things about the stock suspension on track is how soft it is in roll.

Rear swaybar is easy to upgrade since it's the same as the 944; front is tougher, since it's not. Front race spring conversion (with adjustable perches) is kinda easier, but then you're a bit out of synch without stronger rear torsion bars. More back to that...

For shocks, I've not been impressed with the Konis on track. So I'd be inclined to stick with the Bilsteins. We have Bilstiens on the #77 car, but those are custom race units, not the same as the HD street units - which I have on my street 931, and love. But I haven't tracked the 931 much, for obvious reasons, so can't speak too much to how far you can go with them, to be honest.

Beyond that, you get into things that do start to impact street driving characteristics, and you get to decide how far you want to go with the tradeoff. Springs/torsion bars, and then also bushings.

I will say, though I'm no fan of the Konis, that to put the entire 944Cup suspension on the car will probably still be one of the most cost-effective upgrades you can do. Bushings can be a pain to do, but it WILL handle like a racecar. Though underdamped IMO, thanks to those weak Konis.

Another key point to address before you take that Turbo to Blackhawk - brakes!!! Yeah, you're gonna go faster down the straights, but you're still gonna have to slow down to the same speed for the corners till you redo the suspension and get a significant upgrade in rubber. Replace those hoses with stainless braided ones if you haven't already - Paragon has a good price on the kit - and get some KFP Gold pads too. We've used those for 20+ years on the track, and they're awesome.

Brake hoses:
https://www.paragon-products.com/Porsche-944-968-Stainless-Brake-Line-Set-p/por500.htm

For the pads, Paragon used to carry them, doesn't any more... my local guy has them, give him a call, Averill Racing Stuff (tell him I said hi ):
http://www.racing-stuff.com/
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[924RACR]

PS - on the shocks, rumor has it you can STILL get the Bilstein 924 race front strut, part numbers AK1130 and AK1131. Just gotta find a Bilstein dealer who will work with you...

Price maybe arounnd $500-600 ea - will probably require some additional hardware to install, at very least upper strut mount camber plates.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Cedric]

I don't know what they cost in the states, but i would go with the GAZ complete coil over kit as a good starting point (i have the base . Then complete with sway bars, one of them adjustable.

I really like the hawk hp+ pads, but just chose something reputable, pads are everything on track! I assume you have the 5 lugs?

Ive driven the 931 on track alot and it have worked really well, just mire stuff you need to have sorted. Never start with track driving without a check with the wideband though
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1980 924 Turbo
www.instagram.com/garagecedric/

[924RACR]

Good point, I wouldn't want to even think about tracking a 931 on the 4-bolt setup!

...and I failed to clarify in my previous post, but Blackhawk is to my understanding pretty hard on brakes. Haven't run there myself in either car - if I'm towing that long, and through Chicago, I'm headed to RA - but I've heard about it from other racers...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[jacobroufa]

Thanks for the tip on the Bilsteins -- Dan sent a set of them (HD street I believe) with the car when I bought it so that's what's going up front for now.

I already have a Lindsey 5-way adjustable bar in the back, and even with only the rear suspension in decent shape I felt a big difference after adding that last year. I'll have to learn how to tune it now I suppose, and how it handles at different adjustments.

I have a set of fresh brake hoses to put on anyway.. will stainless braided make that much of a difference?

Already did the pads last year and have a couple spares on the shelf as well. Do the KFP Gold or HP+ pads make that big a difference on the track as compared to a stock replacement? What's the difference there? More bite? Less fade?

I do have the 5 lug setup on the 931. Only have 4 lug on the 924 and it ran fine around last year with no brake fade whatsoever and stock pads. Afterward it felt only like I had gone a couple weeks without a drum adjustment; still worked, held the car w/ ebrake, but just needed the stars turned in a bit.

Worth thinking about a 951 brake upgrade or updating the X pattern to front-rear split of the brake lines?

Regarding a coilover kit, if I get one up front is it a simpler matter to do what some of the 944 racers do and cut a torsion change hole in the sill forward of my rear tire, and trim off the cap of the tube on each side? I understand that reindexing is pretty simple with this setup and there's a fair amount of documentation floating around. It seems a) more cost effective and b) less invasive than retrofitting a coilover setup in the rear. Have any of you run with this setup before or does everyone swap to coilovers in the rear eventually? I also understand there are class implications with this if I ever do wheel-to-wheel.

What does the wideband offer Cedric? I have not gotten into tuning this car yet -- only trying to work out the kinks so far and getting it running well. After last year just prior to my transmission kicking 2nd gear it seemed to be running very well. What will I be able to do with one that makes it a useful track-day companion? I see that a lot of 931 folks run one, I just have not gone that far down that particular rabbit hole yet.

Regarding bushings.. since I have to purchase my front a-arm bushings still and apparently at the very least need to order some stainless brake hoses... is it worthwhile getting the delrin or poly bushings that are available for the a-arms? What sort of drawbacks are there to using them? Or should I hold off until I'm more confident in the car and my driving before upgrading bushings? Or is it better to skip the plastics and go right to a spherical bearing setup?

The last thing I want to do though is to upgrade a bunch of stuff and not understand what it's doing for me, so I'm inclined to just wait for more upgrades. Like when a stock bushing bites the dust for me this year, _then_ upgrade it but not before.. Then again I've been driving my 924 for several years now and have a good base comparison so maybe upgraded bushes make sense now.. I think I also understand how this logic doesn't necessarily apply to upgrades like stainless brake lines and will just take some advice there.
_________________
1980 Porsche 931
1981 Porsche 924 Weissach

[924RACR]

The braided brake hoses will give a firmer pedal, but if you've recently put in the stock hoses, maybe just be sure to flush the fluid over to fresh ATE Typ200 (same as SuperBlue but still legal in the states) at the beginning of the season.

I would NEVER trust a stock pad on track. Not on something I cared enough about not putting in the wall, unless you're talking a modern sports car that is designed and tested for track work (as most of the ones I've worked on are).

Stock type pads will fade with the high heat, then you're not stopping and just boiling fluid as they give up.

Hawk pads tend to have a lot of initial bite, which (along with their marketing) makes a lot of people like them. They also tend to eat rotors, which is ugly when they're not so cheap or easy to get as for our cars.

KFP Golds don't have quite the same initial bite, perhaps, but they have better modulation IMO, last forever, and are incredibly nice on rotors. Worth the extra money and effort to get. We put them on Day 1, and have never looked back. Never been able to get the KFPs to fade. I run them on my prototype too, I love 'em so much.

I wouldn't rush into a brake system change like 951; run it first, maybe add some cooling ducts if you want (we don't even run those), but that seems like overkill. If you really find yourself running out of brake, get some better tires, then you won't have to slow down so much. Seriously.

I can't speak to cutting up the body or rear coilovers; we still run only torsion bars in the rear. More of a PITA to install and set up first time, which is why I always tell everyone to go as stiff as you possibly could want to first time: you're NOT gonna want to do it twice. So I'd say go full stiff 30mm if you're gonna do any significant component of tracking; as long as you're not driving around Chicago city roads, you'll like it.

The other big pain of the rear end is setup - alignment and corner balance. But running coilovers instead of big t-bars doesn't seem to me to make that any easier; if anything, it's more of a pain, because now you have two sets of springs in parallel to adjust, vs. just the single set of t-bars. And alignment adjustment is unchanged.

Getting the rear dialed in is a big deal, makes these cars work or not; it's a pain, you want to get it set and forget it, but the effort and long hours are worth it.

I would expect poly (or delrin) should be just fine for tracking. Will be noisy in ride and harsh on impacts on the street, but sufficient for getting the crisp response out of the car, without the pain and expense of full spherical.

But it won't hurt you too much to run with the stock bushings for a year, especially as soft as the rest is. It's amazing how much it wakes the car up. When we switched the #77 from stock (directly) to sphericals, I spent an entire weekend driving the car into curbs; all my turn-in points were way too early, because I'd learned the laggy response of the stock setup, and now the car turned INSTANTLY. Took some time to relearn, but boy was it a nice improvement.

WBO2 sensor: to make sure you're not running lean. You'll need it anyway if you're doing a boost controller, and IC as well (which you'll end up needing on the track with higher boost). Then you can get into fun topics like EFI conversions...

I should mention I've been very happy with the Innovate MTX-L WBO2 kit, now have it on both my racecars (#77 '79 924 NA ITB car and #25 GSXR1000-powered P2 Prototype) and my street 931 (now with Microsquirt EFI conversion, MBC and 951 IC):
https://www.summitracing.com/parts/inn-3918

Quite inexpensive and good quality. Do a lot of tuning with these things now.

For sure, #1 priority is safety; make sure you and the car come back in one piece. Make sure the engine is in a happy state of tune, as Cedric pointed out, and make sure you can stop all day long. You may still run into issues, but they won't be the game-enders of a holed piston or brake fade into gravel trap and wall.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[jacobroufa]

Awesome, thanks Vaughan!

I haven't yet installed the stock hoses; have them on the shelf though. I'll grab a set of the braided stainless.

Appreciate the candor on the pads. I saw the prices listed on the KFP and that seemed obscene compared to everything else. As I want to use this car primarily for track and only some street driving, this seems like a no brainer then..

Seems like coilovers (and therefore any sort of t-bar change and adjustment) are probably not in the cards this year. Good to hear confirmation of the setup though.

I might try poly or delrin for the a-arms then.. I don't mind a bit of noise when I drive.. Can't be as bad as any of the air-cooled VWs anyhow!

I'm surprised you say things like "soft" and "laggy" for the stock suspension. I know it's just a matter of perspective. I'm still pretty shocked though at how a 40yr old car kept up with moderns from my first DE day, and I'm sure once I experience the difference I'll understand.

Thanks for the tip on the WBO2! I'm not sure what IC setup I want to go with -- there have been lots of discussions around that lately. The car's not quite ready for that yet though. I was thinking of having the boost controller for cooler days only at first, as recommended by some folks here 10lbs is safe in most conditions.

Regarding safety... at what point should I be looking into a cage or harness bar, harness, etc?
_________________
1980 Porsche 931
1981 Porsche 924 Weissach

[924RACR]

[Cedric]

Im always promoting to acutallly use the car first, and then feel your way forward with changes, to understand an learn on the way aswell, not just opening upp the wallet, maybe you dont even want all the upgrades, everyone doesnt enjoy the same stuff . Just get brake pads and fluid sorted, good tyres and more negative camber is strongly recommended. I drove my na completely standard apart from r-comp tyres and pads for several seasons, and it was great fun, even though it rolled a bit in the corners, the balance was great.

Chagning the T-bars wasnt that big of a job, and with the excel file available it was easy to get the height correct on the first shot. I only did a rough alignment for the rear (front is fairly easy to diy), it was well worth 150 dollars or whatever it costed me to get the full rear alignment done by a near by shop to my wished specs.
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1980 924 Turbo
www.instagram.com/garagecedric/

[Carrera RSR]

[MikeJinCO]

I would put good poly bushing in the front suspension, To make the delrin front bushing work I had to enlarge the holes in the front cross member in order to set the caster. Ruins the cross member for normal use.

I have a GAZ Gold race system and the ride on a normal road is basic stagecoach. Fine on the track.

For DE work II would find a seat with a bit more support than the stock ones, I had a Corbeau Forza which was quite comfortable, but a bit too wide for me and quickly found myself working hard to stay in the seat on corners that I couldn't concentrate on I now have a Kirkey and 6 point belts which is much harder to get into and out of, but works much better so you can concentrate more on driving than staying located driving.

The Hawk HP+ are fine for DE stuff and half the price of KFP or Porterfield R4. They are also VERY dusty. Wheel scrubbing required after every track visit.
_________________
Mike


'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

[jacobroufa]

Vaughan: understood re safety. I do not have a rollbar yet and as I intend to dive deep into this territory I'll make that, a proper harness and HANS at the top of my list.

Cedric and Steve: I appreciate this advice a lot. I am _clearly_ just overexcited and want to do all the cool things I see other folks doing with this car. You're right I need to take a breath and let the experience tell me what comes next. It's all just such a rabbit hole, especially looking at cars like yours where then I get it in my head I have to compete or keep up somehow. Thanks for the recommendation to take a step back and think things through.

Mike: understand. I think I am going w/ stock suspension at the moment per other suggestions but I appreciate the input! I have the sport seats in the 931 and they hold a lot better than the non-sport seats. Of course this will change with a harness too huh...

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Thanks all for the input! It's very affirming and exciting to have input from so much experience here. I can definitely tend to get ahead of myself so it's nice to have a reality check too.
_________________
1980 Porsche 931
1981 Porsche 924 Weissach