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Water-to-air intercooler installation - 81 931
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jacobroufa  



Joined: 18 Nov 2016
Posts: 310
Location: Rockford, IL

PostPosted: Sun Dec 20, 2020 7:24 am    Post subject: Reply with quote

Chuck this is awesome. I've been watching this -- wanting one of these coolers for my own 931 project for the same reason of the simplicity of install. I'm glad your first impressions are so good! I'm curious to hear what you think after you've run it for awhile, especially in the summer heat.

Put that controller in the cabin already too!
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2130
Location: MI

PostPosted: Sun Dec 20, 2020 10:07 am    Post subject: Reply with quote

You boost control line to your wg is before your intercooler.. Mine is after..
So I still make the same intake boost even through my ic while yours makes the same boost before your ic, therefore you are loosing actual boost pressure..

Part of the reason you are loosing boost pressure across your intercooler isn’t all just it being a restriction.. It is also because the air is being cooled and therefore loosing pressure as it gets denser..

Is Your boost gauge a vac/boost gauge on the vac side of your manifold?

I think you are fine at 13-14psi (or even like 17-1 as long as your AFR stays under about 11.5 in boost and your intake air temp stays below about 150F..

You don’t have to run mid 10s AFR in boost anymore now that you have an intercooler.. I’m pretty convinced that anything under 12.0 AFR is fine in boost if you think your injectors are very equal, or 11.5 to give some room for injector differences..
Between about 10.5 and 11.5 is good.. Under 10.5 gets slower fast..

What is your head gasket situation?
If you are running an old original hg on original studs you might pop it just from it being old..
Check for bubbling in your coolant tank often and for pressurizing before the engine warms up..

New HG and ARP studs will have it taking everything your fuel system can keep up with..
In my experience the standard fuel system acts just fine up to 15psi and probably more..
Can probably be pushed to 20psi just by controlling your frequency valve..

As long as your iats and afrs are good you are good basically, imo..


Also be weary of your iat readings..
Even open element GM iat sensors heat soak like crazy in whatever they are screwed in to..
So if you screw an iat sensor into your ic, even though your ic stays cold, the air in there may be much hotter than your readings..

I put my iat sensor in its own small section of boost pipe to solve this..


Speaking of this.. @carrerarsr where is your iat sensor mounted?
With you reporting such low post ic iats, are you sure your gauge is all that accurately reading your air and not just reading whatever you have it screwed into?? ...

What kind of iat sensors are you guys using?
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chuck21401  



Joined: 20 Feb 2005
Posts: 322
Location: Annapolis, MD

PostPosted: Sun Dec 20, 2020 12:55 pm    Post subject: Reply with quote

Fasteddie313 wrote:

Is Your boost gauge a vac/boost gauge on the vac side of your manifold?


It's connected here.



Quote:

What is your head gasket situation?
If you are running an old original hg on original studs you might pop it just from it being old..
Check for bubbling in your coolant tank often and for pressurizing before the engine warms up...
New HG and ARP studs will have it taking everything your fuel system can keep up with..


Good tip on checking the coolant tank periodically. The previous owner rebuilt the engine in the fall of 2016. Looking back at the for sale post, it said:

"VIN is a 1981, but she has '80 running gear, harness, and engine
- Engine completely rebuilt (new main and rod bearing, new rings, everything cleaned and checked at machine shop)
- Turbo completely rebuilt (by me, but new bearings and seals)"

Here are some pics from the for sale thread from May 2019. I don't know if the head studs were replaced but could check with previous owner. There is an ARP sticker on the air cleaner. Maybe that's a good sign?









Quote:
I think you are fine at 13-14psi (or even like 17-18 ) as long as your AFR stays under about 11.5 in boost and your intake air temp stays below about 150F..


I'm going to run it between 10-12psi for a couple of months and see if everything holds together. If the car gets much faster I'll want to upgrade the brakes.
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Last edited by chuck21401 on Sun Dec 20, 2020 1:11 pm; edited 1 time in total
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chuck21401  



Joined: 20 Feb 2005
Posts: 322
Location: Annapolis, MD

PostPosted: Sun Dec 20, 2020 1:05 pm    Post subject: Reply with quote

jacobroufa wrote:
Chuck this is awesome. I've been watching this -- wanting one of these coolers for my own 931 project for the same reason of the simplicity of install. I'm glad your first impressions are so good! I'm curious to hear what you think after you've run it for awhile, especially in the summer heat.

Put that controller in the cabin already too!


Hey thanks. I'm glad that Dan offered to make another run of intercoolers around this time last year.

I appreciate the collective wisdom of the 924Board. I think I've read every 931 intercooler thread three times.
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Cdric  



Joined: 27 Aug 2004
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PostPosted: Sun Dec 20, 2020 6:50 pm    Post subject: Reply with quote

Is the standard temp sensor for the Ditc connected?

10psi is still stock boost, should be safe , my car felt massively faster with just the intercooler and turbo mods, a big part of it is the huge increase in ignition timing advance by the ditc. The logs agree with the but dyno

You should really have an afr guage if you aren't already have one, or borrow one.
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Carrera RSR  



Joined: 08 Jan 2010
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Location: Somerset, UK

PostPosted: Sun Dec 20, 2020 7:01 pm    Post subject: Reply with quote

Fasteddie313 wrote:


Speaking of this.. @carrerarsr where is your iat sensor mounted?
With you reporting such low post ic iats, are you sure your gauge is all that accurately reading your air and not just reading whatever you have it screwed into?? ...

What kind of iat sensors are you guys using?



I have one post turbo, pre IC and one post IC in the stock position of the throttle body. Post turbo at 1.1bar was up to 125degC with 2660 turbine, now circa 100degC K27 turbine. Post IC can be as low as +6-8degC of ambient air temps on the street boosting. Being in the TB, it can heat soak from the intake manifold when TB is closed and stationary. Soon cools when moving again. Both sensors are standard aftermarket tuning IAT sensors via the Zeitronix logger
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2130
Location: MI

PostPosted: Mon Dec 21, 2020 1:20 am    Post subject: Reply with quote

Carrera RSR wrote:
Fasteddie313 wrote:


Speaking of this.. @carrerarsr where is your iat sensor mounted?
With you reporting such low post ic iats, are you sure your gauge is all that accurately reading your air and not just reading whatever you have it screwed into?? ...

What kind of iat sensors are you guys using?



I have one post turbo, pre IC and one post IC in the stock position of the throttle body. Post turbo at 1.1bar was up to 125degC with 2660 turbine, now circa 100degC K27 turbine. Post IC can be as low as +6-8degC of ambient air temps on the street boosting. Being in the TB, it can heat soak from the intake manifold when TB is closed and stationary. Soon cools when moving again. Both sensors are standard aftermarket tuning IAT sensors via the Zeitronix logger


Yep..
I would suggest that IAT sensors don’t work for crap when mounted into heat banks.. They seem to measure the heat of the host they are mounted in just as much if not more than the air they are supposed to be measuring.. Like putting a giant capacitor getting rid of their effectiveness to read fast changes/swings..

After putting mine in a small section of boost pipe it reads changes much faster and with much greater amplitude..

I think like this would be best, even better than in a small section of hard pipe like mine is currently but pretty close..


CRSR you could put one of those between your IC and upper charge tube and put your IAT sensor in there for much more accuracy..

Not sure where would be good to put one with this water cooler..


Sounds good Chuck..
I just pop my hood all the time and check everything, check my coolant like I said, oil, and always looking for leaks..
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Mike9311  



Joined: 14 Dec 2004
Posts: 983
Location: Chicago-ish

PostPosted: Mon Dec 21, 2020 2:44 am    Post subject: Reply with quote

C�dric wrote:
Is the standard temp sensor for the Ditc connected?

10psi is still stock boost, should be safe , my car felt massively faster with just the intercooler and turbo mods, a big part of it is the huge increase in ignition timing advance by the ditc. The logs agree with the but dyno

.


You have mentioned this twice now and I will keep an eye on this for my own stuff. The first time I read your post on the DITC sensor it lit my sensor in my head as in "hmm that could be a problem" in the wrong location

Chucks car is interesting. ...Chuck do you have a box on the tunnel under the dash in line with the center console ? Like under the heater but back farther? It says '81 but I want to confirm a DITC

Those pistons are 1980 S1 all day long...which is good as far as having lower compression.
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1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
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1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2130
Location: MI

PostPosted: Mon Dec 21, 2020 2:57 am    Post subject: Reply with quote

He said it has an 80 harness and engine, so I’m guessing no DITC..
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Carrera RSR  



Joined: 08 Jan 2010
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PostPosted: Mon Dec 21, 2020 2:59 am    Post subject: Reply with quote

When I say heat soak, when the throttle body is closed there is no air flow, so the air inside the intake manifold will slowly heat up
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chuck21401  



Joined: 20 Feb 2005
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Location: Annapolis, MD

PostPosted: Mon Dec 21, 2020 3:32 am    Post subject: Reply with quote

Fasteddie313 wrote:
He said it has an 80 harness and engine, so I’m guessing no DITC..


Correct. 1980 engine and G31 transmission but S2 throttle body.
The number on the turbo is K26 2664G4.10.

No DITC...S1 ignition. I set the ignition timing to spec awhile back. I think it was 20 degrees before TDC at 2000 rpms with the vacuum hoses off.

And the DITC box is no longer under the dash; I checked.
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chuck21401  



Joined: 20 Feb 2005
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PostPosted: Mon Dec 21, 2020 4:57 am    Post subject: Reply with quote

C�dric wrote:
Is the standard temp sensor for the Ditc connected?


Well that's a good point....I could pull a reading from the standard temp sensor....it's just sitting there unused.

Quote:
You should really have an afr guage if you aren't already have one, or borrow one.


Check.


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Cdric  



Joined: 27 Aug 2004
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PostPosted: Mon Dec 21, 2020 5:39 am    Post subject: Reply with quote

Yeah ive probably pointed it out before, i can't remember my ol posts

If you don't have ditc then just let it sit there, if its unplugged on a ditc car it runs like a dog, massive power loss. You could most like run much more timing advance to get the full benefits of the ic. But run it first to see how stable those iats are before you change anything.

The 2664 compressor is suitable for alot of fun, 1 bar of boost without overspeeding it or running it at low efficiency.
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Mike9311  



Joined: 14 Dec 2004
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PostPosted: Tue Dec 22, 2020 1:54 am    Post subject: Reply with quote

C�dric wrote:
Yeah ive probably pointed it out before, i can't remember my ol posts

If you don't have ditc then just let it sit there, if its unplugged on a ditc car it runs like a dog, massive power loss. You could most like run much more timing advance to get the full benefits of the ic. But run it first to see how stable those iats are before you change anything.

The 2664 compressor is suitable for alot of fun, 1 bar of boost without overspeeding it or running it at low efficiency.


I never had the luxury of a IC on my 80 w/2664 but I remember a distinct test. Mind you this was a longggg time ago.

If I ran more advance the car felt great off the line but like total crap on boost. Of course it was the total opposite if I would retard. I settled on a retarded setting since I could always turn up boost and I liked feeling the 2664 come on unlike any 82 w/2660. On cool days I would push to 15 but ran 10-12/13 alot. With all that said today I would do exactly what you are saying and be careful
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Cdric  



Joined: 27 Aug 2004
Posts: 2076
Location: Sweden

PostPosted: Tue Dec 22, 2020 2:44 am    Post subject: Reply with quote

Mike9311 wrote:
C�dric wrote:
Yeah ive probably pointed it out before, i can't remember my ol posts

If you don't have ditc then just let it sit there, if its unplugged on a ditc car it runs like a dog, massive power loss. You could most like run much more timing advance to get the full benefits of the ic. But run it first to see how stable those iats are before you change anything.

The 2664 compressor is suitable for alot of fun, 1 bar of boost without overspeeding it or running it at low efficiency.


I never had the luxury of a IC on my 80 w/2664 but I remember a distinct test. Mind you this was a longggg time ago.

If I ran more advance the car felt great off the line but like total crap on boost. Of course it was the total opposite if I would retard. I settled on a retarded setting since I could always turn up boost and I liked feeling the 2664 come on unlike any 82 w/2660. On cool days I would push to 15 but ran 10-12/13 alot. With all that said today I would do exactly what you are saying and be careful


Sounds a bit odd, the ignition is pretty retarded in standard condition (at least on the ROW ones im used to) due to the lack of IC, so there is alot of punch to be gained there. A programmable unit would of course be better, or if you are a distributor tinkerer you could open it up an limit/control the boost retard by changing springs etc. If I pull the plug that retards 7 degrees it makes a noticable difference of and on boost when you are used to the full juice

I also like the 2664 better on my car, definitely worse for driveability, but more punch in the top end (it made 168hp at the hubs @ 0,7bar on a stock s2 engine with 2664 no IC), so it was definitely running well) and more distinct when it came on boost. especially noticeable on track where the 2660 went soft with all the heat after many laps. Sometimes fun goes first
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