924Board.org

[Cedric]

Due to lots of questions on forums, FB etc i hereby will make a thread on my intercooler setup, one that I can refer to when i get questions about it 🙂

So I ran my 931 non intercooled for many years, it was pulling strong with 168hp at the hubs on the dyno with some slight tweaks(s2 engine at 0,7bar with slightly larger 2664 compressor). But after a while the urge to try running intercooled was to big. This was planned for a long time, i observed many many installations over the years, and started to design a version based on removing the cast boost pipe as others had done, but didnt like the ugly looks of it, but the one that made me really interested was the one by fasteddie (https://www.924board.org/viewtopic.php?t=42444&highlight=fasteddie). This made it possible to get around the biggest issue with almost all intercooler setups, they make the engine bay look very homebrewed. I think the engine looks really good as it is with the cast boost pipe and metal air box, I like my car tidy and fairly period correct in general so thats why i chose the way I did. Even though it created a few extra challenges.

I also did a bunch of engine simulations (it used to be my job) to evaluate all sorts of turbo sizes to accommodate my power goal, while still running the turbo in an efficient way to keep the engine running healthy even when its hard on track. But thats a different story..


My idea:
-Stealthy from above, should look standard.
-Minimise any cutting of the body.
-Larger turbo, ideally suited for the target boost of 1bar and still running efficiently. It would need a change anyway to get a compressor housing suitable for rotating, and easy integration to the IC system.
-Good thermal capacity, ready for track use
-Possible to make the setup with the available tools I had, which evolved a bit over time.

So when my clutch plate exploded i finally took the chance to start the work while the engine was out, I had previously aquired the intercooler from Joakim.S (with the 445hp 931) who had swapped for a thicker core one. I was planning to use a generic one, but when this got available i went with it instead since i knew it would fit. The end tanks looks pretty bad from a flow perspective, but they are what the are for now. The IC itself is very big and robust, as big as you can fit in the front pretty much. Its based on a Volvo truck intercooler thats been cut and welded. Some very slight piece of body metal had to be cut out at the bottom of the sheet metal to get access to the IC end tanks.



Radiator:
While i was there i changed to a aluminum rad to cut some weight and hopefully improve the cooling a little bit since it would have an IC in front of it, the old one was a a dirty after all these years.I used a generic 944 rad from ebay, welded by monkeys and very thin fins that easily gets damaged. But its survived so far, including a leaking head gasket which pressurised the cooling system quite severely. Brackets were temporary brackets quickly threwn together (they are still there). Fan is a Spal fan screwed to the small brackets in the rad.





Hoses had to me modified a slight bit, so i went to the local car store and bought some hoses to cut and fit the different connectors on the 944 rad, not that difficult, but an extra step.

With v1.0 boost piping




I could route the piping as fasteddies, but it just didnt fit. It gets very tight down there where all the hoses meet at the same spot, and silicone hoses are quite thick walled which eats up space. One thing that also has to be done is to change the oil cooler, which makes the space for the end tanks of the intercooler much better. So i changed to a Setrab oil cooler, and the local hydraulic shop cut of the old soft part of the oil lines and pressed on new teflon hose. I did some diy brackets in my vice to fit the oil cooler in the oem position, it has bajos on the side to make it take up as little space as possible. Not optimal but it seems to work.





Here is the basic layout (version 1,5), the compressor outlet is angled out towards the wheel to get this to fit. I already had change the long horizontal pipe from 2,5 to 2” piping to gain some ground clearance, since the piping was the lowest part of the engine. The IC connectors are 2,5” though which makes it slightly challenging. In the next version 2.0 i changed out the two pipes to the left (turbo inlet and IC to engine). This area I wasnt very happy with, it was very tight, pipes had to be hammered and were still chafing. You can also see the blow of valve placement, though its now painted satin black for a more stealthy look.







V1.0 with the 2,5” piping, but it at least shows the layout



The v1,5 setup, smaller diameter alu piping instead of 2,5” silicone.



The turbo, now with #6 cm2 turbine housing and center section from 931 s1, and K2670 compressor from 944 Turbo (250hp) upgraded with billet wheel. Gives way more space down there compared to the original compressor, and alot more flexibility on the inlet and outlet. It would also produce an easy 245hp at 1bar according to the simulations while still being very efficient with headroom to spare.

Look at the size difference!








V2.0

The final change was to sort out the tightest part of the install that i wasnt happy with, where oil cooler lines, turbo inlet, IC-engine pipe and my weltmeister anti roll bar bracket all fights in the same space.

What I did was to downsize to 2” piping here aswell, which made it possible to run the pipe inside the cast original boost pipe and avoid the large step in area when a hose is connected to it, which causes some pressure drop according to my flow testing. So i 3D printed this sleeve and ported the internal to get a perfect smooth passage.


Some flow testing on different variants and sections of the boost piping, to see where the pressure drops sits, how diameter affects the flow etc.









I also 3D scanned my old bodge of hoses and pipe pieces and 3d printed this clean intake instead, which took up way less real estate down there. The IC to engine pipe were also downsized, a friend helped weld a thing together with the correct angles. Im happy with the outcome, the pipes arent squeezed together anymore and arent chafing.



3D scanned the old turbo intake, as a base for the new 3D printed version




These ugly freaks were out





And are replaced with these (alu pipe prepared for temp measurement later on). Here the oil hose routing is also visible.






So from the top it looks just as it ever had, the performance is absolutely awesome. Even at std 0.7bar boost with the greatly added ignition advance and turbo+IC it is significantly faster than what it was before, with more low end boost aswell. At 1bar boost its very rapid, and the data logs shows it aswell, so far very happy with the performance of this setup, and the Kjet can keep up. It surely needs more track time to prove the durability of the hose routing, clamping etc, and some stuff revisited like the radiator brackets. I hope it can give you some inspiration to take on something similar, or a completely new version of the 931 IC install, theres as many version as there is 931s with IC, everyone prioritises different aspects on the setup, this was made with my thoughts behind it, and it might not be the best for everyone




Or a more recent pic with the bar and new suspension installed


_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[Cedric]

Sorry that the pics are very mixed quality, i hope it gives some idea of what ive done.
_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[scoper]

Thanks for the post and pics! What are the IC dimensions?
Does this car have A/C?
If not, any thoughts on a FMIC on a car with A/C?
_________________
Scott
'81 931 "Mini"
'78 928 "Orlo"
'01 986S "Viola"
'03 540iT/6 DD

[Cedric]

[Mike9311]

Love the write up, the detail, and the engineering

I think the AC cars would need to go more back to FastEddie's way with the IC down low. You could fit something up front but that that point there is a considerable sandwich of heat exchangers up front

Kind of going through this with the '82 and the heat exchanger for the Liquid to Air IC. Making sure its down low and out of the way of the other two while trying to find anything that fits width wise.

Cedric, your set up reminds me of a Buick GN or F150 Ecoboost IC
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Mike9311]

Oh wow, FastEddie's thread is decimated as far photos go. Need upload my dump of his pics I downloaded. At least I have them. Jacob is doing something like this too....never mind he knew this and posted a link to Rennlist. See second one below

No matter what anyone decides there are some rules-of-thumb to be taken from Cedric here like his "pipe inside a pipe" rule depending on flow direction

this is the FastEddie Thread

https://www.924board.org/viewtopic.php?t=41250&start=90

Pics here
https://rennlist.com/forums/924-931-944-951-968-forum/876941-hybrid-turbo-and-fmic-on-931-a.html
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Beartooth]

That's a very cool IC setup! It's almost worth doing that way just for the stealthiness, but should be pretty efficient too. I keep kicking around IC ideas for my car, but I need to rebuild the engine and transmission first and work from there... I'm thinking more towards top-mount, but who knows, and I completely agree about priorities; there are at least four different setups, any of which could be ideal depending on what you're looking to get out of it. There's no golden path to adding an IC to a 931, just several paths with trade-offs. Anyway, I hope you'll keep us updated - it'd be good to see how much more power you get if you can get it on the dyno!
_________________
1980 931 diamond in the rough

[Cedric]

[Mike9311]

I love all this

What is also interesting by now is all the data from others you can look at for your sims. You know the actual dyno numbers from a few builds now. CarerraRSR and LiLDude gave us a lot to look at. With different builds and IC's they were still within 8-10HP of each other half way around the planet! I wish we knew the numbers from FastEddie with his high boost craziness. Then there is Joakim
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car