924Board.org

[bnoon]

I know about the distributor being half electronic on my 80 vs fully electronic controlled in 81+, but are the rest of the sensors/etc the same? Would there be anything that would work from an 81 to repair my bad 80 parts? Mass air, injectors, etc?
_________________
'80 924 Turbo - SOLD!
1986 Porsche 944 Turbo - SOLD!
Porscheless

[BReyes]

Read this morning a description 'half vacuum, half digital in 80 to all digital in 81'. Yours an early or a late 80 US or Euro?

regards,
_________________
Bernard

[bnoon]

I'm unsure, I didn't know about the mid year change over. How do I know for sure? If it's a late version, then the 81 is a direct swap right?
_________________
'80 924 Turbo - SOLD!
1986 Porsche 944 Turbo - SOLD!
Porscheless

[emoore924]

Ok folks,

Long block = motor bottom end (block, crank, pistons, mains, rods, oil pump) up to and including head.

Short block = motor bottom end not including head.

No accessories included in either -- no alternator, sensors, a/c, manifolds, throttle bodies, fuel system, ignition or fuel dizzy.

Now that we have that straight, carry on...

[ideola]

Not sure this is comprehensive, but it's a start (S1 feature listed first, followed by S2 feature):

• Intake manifold: ovoid vs. round throttle body opening
  
• Throttle body: ovoid dual butterfly vs. round single butterfly
  
• Upper charge tube: ovoid with rubber connector vs. round solid connection
  
• Lower charge tube: slight differences, but should still be interchangeable
  
• Multiple microswitches vs. single TPS
  
• Hall effect & CD-based ignition vs. DITC (this encompasses the ignitor, the DITC box itself, and the ignition distributor, none of which are interchangeable)
  
• S2 has an intake air temp sensor to the DITC box
  
• S2 has a boost reference line to the DITC box
  
• S2 has a crank position sensor
  
• Breather update. This one is much trickier to track down to S1 vs. S2. I believe there were at least 3 variations of the head breather configuration, and I've seen late 1980 models that already had the S2 setup. Some of these may have been retrofitted due to service bulletins, dealer maintenance, or a savvy P.O.
  
• Turbo oil drain line. This is documented elsewhere, if I can find the reference material, I'll link to it, but there are three iterations of the drain line, and like the breather update, are not necessarily delineated by S1/S2 or model year. Some of these may have been retrofitted due to service bulletins, dealer maintenance, or a savvy P.O.
  
• 7.5:1 vs. 8:1 compression ratio on the pistons, and the dish configuration is also different.
  
• Unreinforced vs. Reinforced exhaust manifold. There are a couple of decent threads on this topic as well that you should be able to dig up with some creative searching.
  
• There are some variations on the hotside and coldside configurations of the K26 turbos. Search for -nick's "all you want to know" thread on the K26 for details.
  
• S2 Wastegate has a bleed line attached to the top that doesn't exist (but can be easily retrofitted) on the S1 wastegate
  
• WURs are different
  
• AAVs are different
  
• Fuel distributors are different
  
• AFMs are different
  
• Vac limiters are different
  
• There are two different configs on the dipsticks, one that has a guide tube and one that doesn't. PET is not illustrative; the topic has come up before, but I'm not sure that we've ever reached a conclusion as to whether it was an S1/S2 difference, a model year difference, a market difference or what. But I know that I have an S1 without a guide tube, an S1 with a guide tube, and an S2 with a guide tube.
  

PET is your friend. If you really want an exhaustive list, you'll need to carefully and studiously consult PET.

Now, the tougher part of the question is what is interchangeable. I'll take a crack at getting us started on that discussion too...this should be fairly accurate, but it would be wise to get others' opinions and validation.

• Pretty much everything on the head can be freely interchangeable.
  
• Several S2 updates are desirable to add to an S1, including the breather update, the turbo drain line update, and the exhaust manifold.
  
• Personally, I would not recommend upgrading to DITC due to the difficulty in finding good operational parts at reasonable cost. In fact, in some cases, retrograding an S2 to the earlier, simpler, more primitive but easier to maintain S1 ignition setup is a worthwhile consideration.
  
• The entire S2 intake tract is a desirable upgrade for an S1, including the upper charge tube, throttle body (& TPS), and manifold (leave the IAT in the S2 manifold and don't worry about connecting it).
  
• You could conceivably swap the later higher compression pistons over, although without bringing the DITC over as well, careful AFR monitoring would be highly advisable due to the higher likelihood of detonation. But with proper fuel management, as well as intercooling, there's no reason you couldn't run the higher compression pistons in an S1 long block.
  
• Regarding the CIS, the best thing would be to bring the entire system over (fuel dizzy, AFM, WUR, AAV, & vac limiter) as a matched set, rather than trying to mix and match S1 and S2 components. CIS is hard enough to troubleshoot as it is, no point making it more difficult by having ill-matched components.

_________________
erstwhile owner of just about every 924 variant ever made

[peterld]

Great post Dan. However I'm now somewhat intrigued by your comment re the dipstick guide tubes. I have 4 various 931 sumps at my disposal - none have usable dipstick guide tubes left as all were damaged at some stage. I have been trying unsuccessfully for quite some time to get a replacement with no luck. NLA from the factory and no one seems to have a spare anywhere. I'd love to see a photo of the dipstick-in-block scenario. The dipstick for this application must be a short little bugger! And what holds it in? Is it possible that someone else broke a dipstick guide tube and thus removed it and consequently shortened the dipstick itself? Does the shorter dipstick have oil level markings on it? Does it look factory?
I would actually prefer the short version - compact and out of the way.

All this and more shall be revealed in the next episode of 'Toofah Tumult' brought to you by Ideola New Media.
_________________
80/81 932/8 ROW

[ideola]

It certainly is possible that the shortened version is not factory. It's on my 941, which is actually a modified S2 long block, with many aspects retrograded to S1. I have no idea what pistons are in the block.

As for the dipstick, it is indeed shorter, but it does appear to have the same factory end and markings on it. At the top where the pull handle attaches there is a rubber grommet type deal that helps to hold it snugly in place in the block.

The 941 is at the painter's right now and I won't be able to get access to it for a few weeks. I'll try to remember to photograph the dipstick when I get it back and compare it to the tube-style versions.
_________________
erstwhile owner of just about every 924 variant ever made

[peterld]

Thanks Dan. Cheers.
_________________
80/81 932/8 ROW

[bnoon]

[ideola]

Actually there's a lot of stuff that can be changed over, particularly in the direction you're going. To keep it simple, here are my feelings:

• S2 ignition onto an S1? Why bother??? If you REALLY need upgraded ignition that badly, you'd be better off going with something like MegaJolt.
  
• S2 CIS onto S1? If your S1 CIS is shot, this might be worthwhile, but I would do it as a complete system as described above, rather than mixing and matching parts. And btw, since I neglected to mention it earlier, the injectors are interchangeable.
  
• Everything else is all goodness (pistons, intake, exhaust, breather update, turbo oil drain, etc.). Obviously some things like the intake tract need to be done as a complete unit.

In short, hang onto your S2 stuff for spares. Anything you can't use you should sell to fund other stuff you'll undoubtedly need to purchase.
_________________
erstwhile owner of just about every 924 variant ever made

[tuurbo]

[ideola]

The S2 pistons raise your CR by half a point, so you'd have to do some math to figure out the static + dynamic pressure depending on what boost level you intend to run. Once you have that, you should be able to get an idea of the recommended octane rating. The big thing that the complete S2 setup offers over the S1 is the rudimentary ability to detect knock-inducing conditions and retard timing accordingly, therefore allowing a bit more aggressive tune on the ignition side of things. So DITC is really a safeguard more than anything else. With S1 ignition, you don't have this safeguard in place.

It seems to me that a safe place to start would be to dial back your boost to stock US level and keep the water injection system in place. The static compression increase will help a little (theoretically) with some low-end torque and should make up for some of the boost you're giving up. All in all, it should be a safer arrangement since you'll not be compressing as much at the turbo and therefore should be reducing the overall IAT. Just remember, the static compression increase will add some heat to the charge air, but running your turbo at a lower boost level should decrease the IAT by more than the increase caused by the static CR (due to non-linear relationship of total compression to heat gain, as well as the efficiency range of your K26 compressor).

Everything else being equal, if you came up with a total compression setup with the higher static CR pistons and reduced boost level that equated what your current setup provides, it should result in a lower total IAT. The calculations should help you figure out the temp differential between the different combos, i.e. 7.5:1 static + 12 PSI = X+ambient while 8.0:1 static + 6 PSI = Y+ambient. There are ways to figure this out, I think the Corky Bell book has some or most of it, and I know Hartman's Turbocharging Performance Handbook has an entire section dedicated to all of these types of formulas.
_________________
erstwhile owner of just about every 924 variant ever made

[ideola]

Here's another thread on swapping an S2 intake setup onto an S1 car:
Intake manifold, upgrading to S2
_________________
erstwhile owner of just about every 924 variant ever made

[tuurbo]

Thanks Dan I should look through Corky Bell and see what I can do - excellent news!
_________________
1980 924 turbo, MSD, Meth. Inj, otherwise stock.

[Paul]

Spike (S1) has 8.5 pistons, going strong the last I heard....
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.