924Board.org

[Mike9311]

I actually think the 45deg pipe does have the beads depending on when it was sourced (?? in the original kit I mean) but a good point along with the heat softening idea.

Is the little bit of oil present making the sealing less effective? Its possible the oil is affecting the silicon over time? (in that some silicon hoses are not as good with oil)
_________________
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

[Cedric]

[lildude4life]

I had a similar issue with the 45 degree hose off the turbo.

Ended up finding a (memory is fuzzy) a 2" to 2.25" reducer 45 degree elbow.

We obviously don't have the same turbo, but I had slippage issues too and what solved is was a better sized elbow going to the turbo that was naturally a tighter fit.
_________________
"931 EFR" 81 931 S2 w/ EFR 6258 turbo, EFI, Haltech Elite ECU, 240whp

[chuck21401]

re: Maybe you need to try to heat insulate the silicone hose

That might be a good idea. Temps in that area measured with a laser thermometer are high. The hose and hose clamp measured over 200F after a run yesterday.

Re: Measuring water temp at least before the intercooler would tell you alot about the capacity of the system, and how/if it stabilizes water temperature relative to ambient temperature.

I installed the water temp sensor after the intercooler pump, but before the intercooler. Water temps were generally 5 -10 degrees over ambient air temps....but quickly climbed when sitting still...maybe +15 - 20 degrees.

Edit: And then the high temp fan kicks in and cools things down again. Maybe 10 degrees over ambient. Need to be cruising to see 5 degrees over ambient air temp.

Re: Whats the state of the turbocharger, when was it rebuilt last time?

Turbo was rebuilt by previous owner in 2017. I'd say maybe 12K miles on it at the most.

Re: You need a proper lip on the metal tubes that the silicone will be clamped on.

That would help but not sure how I could get that done.
_________________
1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

[chuck21401]

re: I actually think the 45deg pipe does have the beads depending on when it was sourced (?? in the original kit I mean) but a good point along with the heat softening idea.

I didn't buy the kit but followed the parts list.
Source: https://web.archive.org/web/20160620120908/http://garage.ideola.com/prod-BoostSolutions.html

2 45 degree silicone pipes and one 90 degree aluminum elbow. The elbow has lips on either end....as does the intercooler inlet.

Is the little bit of oil present making the sealing less effective? Its possible the oil is affecting the silicon over time? (in that some silicon hoses are not as good with oil)

I don't know for sure that heat and oil caused the problem, but it didn't help.

The replacement silicone hose was much firmer. I also replaced the orange o ring (99970147340) at the turbo. That was soft; the new one was firm.

I put everything back together; so far so good. I turned the boost down to 10PSI.
_________________
1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

[chuck21401]

[chuck21401]

[chuck21401]

re: So I'm trying to figure out what is going on. I noticed oil in the hoses as well as the intercooler. I've seen this before and the car does NOT smoke. But it makes me wonder if somehow the intercooler has become clogged? I'm going to drain the antifreeze, remove the intercooler and take a look.

I found some oil in the intercooler but not as much as I feared and it wasn't clogged. I cleaned it out with carb cleaner and pushed some air through it with my shop vac using it as a blower.

I opened the throttle body....no oil present there.

I also figured out why I had a problem getting the intercooler to fit to the throttle body...note that the lip is dented. I sanded the area *slightly* and now it fits just fine. No wonder it kept cutting the big orange O ring...and the seal wasn't perfect. Luckily I had an extra big O ring on hand.




_________________
1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

[chuck21401]

[chuck21401]

[chuck21401]

I installed the new gauge to measure intake air temps before and after the intercooler. I've mounted it temporarily under the passenger shelf; I'd like to find a better home for both temp gauges.

The first sensor is mounted in the silicon boost pipe before the intercooler.



The second sensor is mounted in place of the original S2 intake air temperature sensor.



Here is a close up the K type thermocouple.



Here is what the test set up looks like. The gauge labeled intercooler temp measures the water temperature after the front mounted heat exchanger but before the intercooler.



These video clips are not the best but they give you an idea of the intake temps and how well the intercooler is working. At 22 seconds into the longer video, the intake temp after the turbo hits 238F while the intake temp at the throttle body is just over 100F. And that was with around 12-13psi of boost. It's interesting to see how quick the temps rise on boost...and I'll be curious to see what the readings will be at 15psi of boost.

Short clip (6 seconds)
https://youtube.com/shorts/Fw75xMZcszs

Longer video (30 seconds)
https://youtu.be/PbmZWOYmJhI
_________________
1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

[Cedric]

Great that the setup is up and running. Will be interesting to see how it behaves after some repeated accelerations down a twisty road and after some high speed driving.

I think its positive that the boost temp responds quickly, the boost air itself should be pretty much instantly follow the boost pressure. At least out of the compressor, in the intake there is of course the inertia of the IC itself.

I did a theoretical plot of the calculated boost temps, I only do metric though Mind the X axis, its absolute, so Ambient pressure+boost pressure. But its a rough guide on what to expect, it shouldnt deviate wildly from the theoretical numbers, or something is off.

Boost outlet temp with 20 degree inlet temp, and 65% efficiency (which is low so probably at the end of the rev range). I dont remember which compressor you have on there? You would probably end up at the 250-260F range at full boost then


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

[chuck21401]

The numbers on the turbo are K26 2664 G 4.10

I believe that is the larger S1 compressor. I was running 15psi but the boost hose kept popping off the turbo. Will run 12-13psi for awhile.

I’m a bit surprised by intake temps before the intercooler at modest boost but also impressed to see the temps at the throttle body are 100+ degrees less.

The short videos don’t cover the recovery after hitting the boost hard, things cool down quicker than I expected. The heat exchanger is working well but still thinking about mounting a bigger one.


_________________
1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

[Mike9311]

What is the thread size on that thermo? I like what you did there and maybe that could be into the billet pipe as a threaded boss

On the '82 I welded a boss at the rear to improve my connection the the wastegate hose. Suppose that is an option but nobody really wants to weld on the $$ intercooler
_________________
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

[chuck21401]