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Peter's 931 Intercooler Installation
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Peter  



Joined: 04 Nov 2002
Posts: 379
Location: New York, NY

PostPosted: Fri Jun 02, 2006 2:38 pm    Post subject: Peter's 931 Intercooler Installation Reply with quote

Hi All,
I just got around to uploading some pics of my intercooler installation. The pics are pretty self explanatory. I just mounted an intercooler into the battery-box location and relocated the battery to the rear passenger-side seat.
I used 2/0 muli-strand copper welding cable for power and ground.
The intercooler inlet pipes are steel.
The intercooler outlet pipes are the charge tube, which I reversed, and drilled and taped fittings for all the original equipment.
I also installed a remote disconnect (this is my track car).
I also installed a Ford remote starter solenoid switch.
Hope you enjoy the pics. After I shoot the primer (I am in the process of painting the car) I will install the hood scoop and post more pics.

BTW, I have an extra intercooler. I purchased two, one for practice and one to get it right. Suprise, I got it right the first time. If anyone wants to try to do a similar setup, I will sell the intercooler for $30 (good used condition) + shipping( about $15 in continental USA). It should go without being said, but you must do your own fabrication, the intercooler does not come as a "931 bolt-on"!







Last edited by Peter on Fri Jun 02, 2006 11:53 pm; edited 1 time in total
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Joes924Racer  



Joined: 03 Nov 2002
Posts: 11960
Location: Oregon, Denver Colorado native!

PostPosted: Fri Jun 02, 2006 2:59 pm    Post subject: Reply with quote

awesome dude. I like it. looks like your
working on paint too.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.
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sequential  



Joined: 18 Nov 2005
Posts: 500
Location: BANNED

PostPosted: Sat Jun 03, 2006 1:07 am    Post subject: Reply with quote

Dude , that is the highest temperature point in the engine compart ,WHY WOULD YOU PUT THAT INTERCOOLER THERE , you are going to kill that engine with excessive intake temps
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endwrench  



Joined: 07 Dec 2002
Posts: 1629
Location: Victor, Montana

PostPosted: Sat Jun 03, 2006 2:11 am    Post subject: Reply with quote

It's probably not the most ideal spot for a cooler but with a scoop, some seals and some sort of "exit stratigy" it should work fine. The execution of the project is pretty nice!

Todd
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'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....
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Peter  



Joined: 04 Nov 2002
Posts: 379
Location: New York, NY

PostPosted: Sat Jun 03, 2006 9:56 am    Post subject: Reply with quote

Yeah Joe, I am in the process of painting it. Hopefully, time permitting, by the end of June I will have two coats of epoxy on it. Then I will mount the hood scoop.

I initially though of mounting the IC over the engine, like the factory did, but I assumed that all the cold air generated by the engine would freeze the IC. So I mounted it in the “hot” battery box, and to make things worse, I am installing a hood scoop that will draw in high pressure “hot” air from the outside, through the IC, and into the “cold” engine bay.

Seriously, although the engine compartment isn’t the “best” location for an IC, for a 931, its really only one of two locations (either inside the engine or in front of the radiator). The “best” course of action would be to buy a 951. There are no 931 experts on IC location on this Board, other than the factory technicians, who don’t seem to frequent this Board. So experiment with your 931.

For my own education, how is the battery box location the “highest temperature point in the engine compartment?” Isn’t the hottest part the engine itself? In all seriousness, I would like to learn something so please explain.

Todd mentioned an exit strategy. According to one of my reference books (Aerodynamics for Racing and Performance Cars by Forbes Aird, published by HP Books), the base of the windshield/hood area is an area of highest pressure air. The hood scoop will draw in this cold air over the IC. I have two choices for post-IC air exit: (1) vent air into the engine compartment; or (2) seal off the IC area from the engine and vent the air out behind the rear of the hood. I prefer the first choice. According to Up-Fixin der Porsche, (a series of PCA publications that cover all Porsche technical and factory information from 1956 to the present), the 931 duct was installed to route cool air to the wastegate, not the turbo or exhaust manifold. The flow of cold air enters the side, traveling around the front of the battery box and behind the engine to the wastegate and exiting under the car. By venting post-IC air into the engine compartment, it will aide in cooling these components. Furthermore, the engine air, although hot, is of low pressure, and will not block the venting of post-IC air (see below) Second, if I vent post-IC air behind the rear of the hood, I am concerned that higher pressure air at the base of the windshield/hood area will push the venting air back into the IC, resulting in blockage. I have not found any satisfactory info that will contradict this hypothesis. Thus, option (1) for me.

Although the engine generates hot air, the air is of lower pressure than the cold high-pressure air entering the hood scoop. Simple test. Test #1, drive down the highway with your hand sticking outside the open car window, palm open and perpendicular to the flow of air. You will feel a great deal of resistance pushing your hand back. This is high pressure cold air. Test #2, run your engine to get it very hot. Open the hood. The air is hot, but it doesn’t push you back. This is low pressure hot air.

Lastly, the IC core above measures 4” * 6” * 8”. The core sits about 3-4” above the base of battery box. Only the IC intake and exhaust tubes stretch into the engine compartment. The hood scoop opening is larger than the 6” * 8” rectangular opening of the IC, so a “funnel” will be fabricated to direct the air into the IC. The contact point between the “funnel” and the underside of the hood will have window channel weather stripping to prevent the incoming fresh air from bypassing the IC. I initially purchased this IC in 2001, with the intention of fabricating a Holbert style IC, and based my purchase decision on flow test results that showed that of several of the ICs on the market (both OEM & aftermarket), only the Spearco IC out flowed the IC used above. I will post the site’s URL with the flow test results when I find it (must be one of my bookmarks).

Just as an aside, I am a novice, with some basic tools, so my fabrication ability is quite limited. Never-the-less, I always try to do the best job I can and any hints from the professionals are always greatly appreciated. The 931 will replace my 924 track car, which is used primarily for PCA DE events. This should also give you information as to how the car will be used and my feasible choices for an IC.

Thanks,
Peter
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endwrench  



Joined: 07 Dec 2002
Posts: 1629
Location: Victor, Montana

PostPosted: Sat Jun 03, 2006 5:40 pm    Post subject: Reply with quote

Peter,
I think your thinking is pretty sound in theory. Only trial and error will tell for sure now. You may want to play with some different sheilding and ducting techniques. I would be sure to use a belly pan of some sort to help create a nice low pressure area in the engine compartment. This will also help engine cooling.

I am not so sure option 2 would not be viable though. I was always of the understanding that the cowl area of most cars is actually a low pressure area. I believe this is why most muscle cars used "cowl induction" rather than scoops. Scoops usually are not of much use until relatively high speeds are achieved wich may work well in your application.

Todd
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Cédric  



Joined: 27 Aug 2004
Posts: 1930
Location: Sweden

PostPosted: Sun Jun 04, 2006 1:30 am    Post subject: Reply with quote

Nice ic installation. But that scoop will be placed in a low presure are. Take a look at this picture, you can clearly se how the pressure is variying along the body. "Underdruck" is low pressure and "Uberdruck" is high pressure.



I´ll be following your progress, it would be nice if you reported back after trying it on the track. I have similar plans for my 931. I just cant descide where to place the ic..
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sequential  



Joined: 18 Nov 2005
Posts: 500
Location: BANNED

PostPosted: Sun Jun 04, 2006 1:55 am    Post subject: Reply with quote

IT IS AMAZING AT THE SPEED OF WHICH INSANTY SPREADS.....

Peter ,

You are going to destroy your engine , the intercooler cannot work where and how you have it ...

The only way to salvage what you have done is ,

1. Invert the IC to standing position .
2. make a naca duct of the hood to feed the face of the intercooler , sealed straight to it ..

3. the other side ( exit side ) will face thewindshield where the low pressure here will help to evacuate the IC...

4. this is the only way to salvage your setup , you should also insulate the ic from the engine compartment including pipes..

What is WRONG ?
1. you have the ic and pipes mounted on the hottest side of the engine compartment .
2. the heat soaking to ic pipe and the intercooler will lead to you destroying your engine ..
3. on rainy days you will not be able to see out of that half of the windshield ..


It is just plain wrong and you better secure your battery better by placing it on the floor or that thing could wack you in the head in a rollover.....

which could be bad , i think .... unless you are one of those guys that wear a helmet to protect the car ....


I just can't believe , the encouragement being given to you about this, as the guys here should know better...
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928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2
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Bullet924  



Joined: 02 Jun 2006
Posts: 14
Location: MetroWest, FL

PostPosted: Sun Jun 04, 2006 2:56 am    Post subject: Reply with quote

I found this when I was looking for various intercooler installs. Might be kind of cool with a fan on it. But is still in the engine bay.

_________________
McQueen had his Mustang I have my Bullet 924.
Getting rid of the Turbo for a supercharger and body kit are just a begining...
Carrera GT Flares, Custom Fiberwerks Front..
Hood Scoop - Like the CGT but...

Thanks West & HBM
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Cédric  



Joined: 27 Aug 2004
Posts: 1930
Location: Sweden

PostPosted: Sun Jun 04, 2006 4:03 am    Post subject: Reply with quote

Bullet924 wrote:
I found this when I was looking for various intercooler installs. Might be kind of cool with a fan on it. But is still in the engine bay.


Haven´t seen that solution. It could work pretty good with some bonnet modifications. Like this 931, he cut holes at the high pressure area in the front for better air flow. And it did work.


This is another solution i´ve been looking at, maybe to much bends and tiny tubing.

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Peter  



Joined: 04 Nov 2002
Posts: 379
Location: New York, NY

PostPosted: Sun Jun 04, 2006 6:24 am    Post subject: Reply with quote

Hi All,
Thanks for the comments: I will definitely take them under advisement.

Cedric, I have a printout of the ORIGNIAL Porsche 924 poster of the aerodynamics of the 924/931, from which your car diagram and chart came from. Here is link to an online source to purchase it http://www.adaholic.com/AdDetail.asp?Id=1494. It’s hard to read, but you can use your mouse to zoom-in on the chart. Someone on this board has it scanned into their website, if they could post a full-size link that would be great. Anyway, your diagram is correct. Your chart is some what off. However, your conclusion is wrong. The number 15 spot on the car diagram is LOW pressure, and as you progress, you get to the number 20 spot on the car diagram that is HIGH pressure. Your chart shows 18 to 23 as HIGH pressure. Uberdruck in your own words is high pressure. This is where the hood scoop is to be mounted. Side note, the highest pressure area is at #3, where the oil coolers are mounted.

Sequential, thanks for your explanations. I now understand what you mean.
Points 1 & 2 are a no go. I don’t have the time, desire or abilities to mount the IC vertically.
Point 3. I disagree. The base of the windshield/hood (# 20 area) is an area of HIGH pressure. See Cedric’s diagram and the link provided above. Venting the post-IC air into this high pressure area will cause the air to be pushed back into the IC. If you disagree, please expand on this point.
Point 4. The post-IC high pressure cold air will vent into the engine compartment, competing with the low pressure hot engine air. The air will take the path of least resistance and flow behind th e engine and under the car. Remember, the factory IC sits on top of the engine, and still manages to work.

What’s wrong?
Point 1. I agree. Buy me a 951. Seriously, I do the best I can with what I have.
Point 2. Some what agree. Vented post-IC high pressure cold will exit over the pipes cooling pipes. Will add shielding under IC pipes to redirect hot air back down into engine.
Point 3. Glad you asked. My theory for cracked #4 side exhaust manifolds is that the water from the battery box drains directly onto the HOT exhaust manifold. Simple test: With a cool engine, run water from a hose into the battery compartment and watch the water flow through the battery drain, onto the motor mount then onto the exhaust manifold. Anyway, to fix this problem, I attached a rubber hose (3/4”) to the battery drain, allowing the water to exit without hitting the HOT exhaust manifold.
Battery location: Metal plate welded to seat. Primary hold-down mechanism (1) Battery box BOLTED to metal plate (using grade 5 SAE bolts and large washers to distribute the load). Additional hold-down mechanisms include (2) box secured by threaded rods and hold-down bar, and (3) black battery hold-down strap. Safety is a primary concern for me, and this box is going no where.

Any additional comments, suggestions, or civil criticisms welcome.
Thanks,
-Peter

EDIT: For some reason the link does not open to the Porsche 924 Aero poster. Follow the links on the site to Porsche, and then scan down to the available posters. Its called consumer orientation No. 5. Double clicking it will open to the diagram and chart.
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sequential  



Joined: 18 Nov 2005
Posts: 500
Location: BANNED

PostPosted: Sun Jun 04, 2006 7:29 am    Post subject: Reply with quote

Peter ,
Hey look at the hood carefully , you see how it curls just before the windshield , Ok this helps to create a sweeter low pressure area behind it , the high pressure point is just before and the area between the hood and the windshield there is no air flow there. the next high pressure point is mid way up the windshield to the top of the roof and from the tip of the roof to 6 -7 inchs back .....
I don't care what druck , buck , stuck or crock S****, your diagam says that point is low pressure ......\

you guys are reading the chart backwards, the higher numbers represent
lift , negative pressure , the lower numbers from the waistline down is the high pressure . on any car the highest pressure point is the snout. this confusement has allowed you to destroy your car peter ...

If you look at the the highest number on the chart it is under the rear bumper this is where the pressure point is highest hence create a suction ( low pressure) but the air has the highest speed.. the front bumper ( the point of slowest air movement ) has the lowest because it is where the air pressure is highest showing a constanant closes't to naught , hence the numbers around here are the lowest on this chart....

so on the low numbers drag is highest but downforce is allso the highest , on the high numbers lift is highest hence the area under the bumber is to react against the lift figures above... by this i mean george , that if the area under the bumber had a lower number that the rear hatch you would go for a ride backwards as the rear would have a tendency to lift .

As you can see from the car profile it looks like a wing .. go look at how a plane wing produces lift and you will see where the pressure points are acting against .... i believe the numbes should have had a minus in front of them ....
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928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2
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Peter  



Joined: 04 Nov 2002
Posts: 379
Location: New York, NY

PostPosted: Sun Jun 04, 2006 7:54 am    Post subject: Reply with quote

Sequential, I appreciate your comments.
Based upon all that was said throughout this post, I will do the following:

(1) Install a sheet metal barrier between the valve cover and strut tower, running below the IC charge pipes, from the turbo to the battery box. This will help prevent heat soak in the IC tubes.
(2) Install sheet metal barrier in front of IC, sealing the battery box, except for cutouts for the IC charge pipes.

Two questions for Sequential:
(1) Why do you recommend a duct rather than a hood scoop for my set-up? Disregarding any issues of drag.
(2) Does post IC venting require any hood cutouts, snorkel, etc, or will the air naturally take the path under the hood and out by the windshield?

All comments welcome.
Thanks,
-Peter
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sequential  



Joined: 18 Nov 2005
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PostPosted: Sun Jun 04, 2006 9:15 am    Post subject: Reply with quote

because there is low pressure at that location on the hood , you will be better off using the boundry layer to feed the IC. make a naca duct to feed air to the IC , it will only be effective if you stand the ic upright so it can escape thru the windshield section, The position you have it in ,the air is limited to how much can get sucked out , of course you could use a fan ..
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928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2
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Peter  



Joined: 04 Nov 2002
Posts: 379
Location: New York, NY

PostPosted: Mon Jun 05, 2006 3:42 am    Post subject: Reply with quote

This is from an excerpt from a private conversation I am having with a Board member and though it would shed some light. I am willing to hear any advice about using a fan to push air into the IC or about battery mounting.
“I will follow the advice given about using a heat shield under the IC pipes. I will also isolate the battery box from the engine compartment. The air flow issue is what I am unsure of, and I am thinking of just adding a 6.5 ” Spal fan under the hood scoop to push air through the IC. http://www.slickcar.com/productdetails.asp?ProductID=414
I chose an air/air setup rather than an air/water setup because this is a track car only. My runs are 35”- 45” minutes long, and then the car is parked for 1 hour or so. With an air/water setup, I don’t believe that sitting in the pits will cool the liquid sufficiently; whereas, with a top mounted IC I would, as I normally do for my 924, leave the hood open to cool the engine (and now IC for the 931) while I check tire pressures, get a cold drink, chat with friends, etc.
Battery location: A metal plate is welded to the seat. The box is bolted to the plate. Then threaded rods are bolted to the plate, with a metal hold-down bracket. Finally, a strap is also wrapped around the battery. All the installation kits I have seen only use threaded rods with a hold-down bracket. As I am using three devices, I think it should be fine, but please feel free to offer any suggestions. Maybe metal aircraft cable wrapped around the box and bolted to the metal plate? Also, I am running two clear plastic tubes as vents to the underside of the car.”

Thanks,
Peter
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