924Board.org

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Hey folks,
Just wanted to share the progress. The pics below show where the IC will sit. The IC inlet is going to get cut off from the stock location then welded onto the side with the inlet angled down toward the turbo. Obviously the stock inlet location won't work as it aims directly into the cam sprocket! Moving the inlet to the side will give a straight shot out of the turbo to the IC.

The IC outlet is angled perfectly toward where the big Mustang throttle body will sit off the intake manifold. Very short plumbing on both sides!

I'm going to make a sheet metal shroud that will direct air from the vented nose panel directly into the IC. It's actually pretty simple.

Enjoy!
nick

Picture the IC outlet mated up to this TB position:

924RACR · Posted: Fri Jun 10, 2005 11:13 pm Post subject:

Cool! Changing those end-tanks should give much better flow, resulting in improved efficiency of the IC. Even though it lines up well, I'd suggest you consider replacing the end tank going to the TB as well. You've got more room to work with than the stock 951 setup. You can see how badly that end is shrouded by doubleing back - just open up the radius.
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Webmeister
'79 924 #77 SCCA H Prod racecar
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-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

I'm trying to keep this from getting too rediculous at the moment. It will be easy to experiment later on with the outlet tank. I know it's a big restriction stock. From what I've heard, the 951 IC has a 2psi drop across it, which isn't too bad. I think I can spin the K26 up to 15psi (efficiently) to get 13psi at the manifold.

nick

simsport · Joined: 06 Nov 2002 Posts: 573 Location: UK Warrington

Hi Nick,looks good, a few thoughts if I may...

The position of the IC. Is there a reason why you have chosen to mount it inboard as against in roughly the original 951 position?
The reason I mention this is because the ability of the badge panel and inlet to 'ram' the air is a real advantage, also in the position you have it now heat soak could be an issue.

The other observation is that your throttle is mounted at a tight angle to the first inlet port. I did this with my first inlet manifold and ended up reversing the flow direction becasue that cylinder was getting noticably less flow than the others.

Just observations these and however you choose to do it in the end I'm sure it will go great.

Cheers
Simon
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J1NX3D · Joined: 06 Feb 2003 Posts: 1333 Location: New Zealand

might be of some interest to you Nick i just found these pics

theres no info though
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'86 944

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Hey guys,
Thanks for the interest. Those pics are very interesting- I've never seen them before. Simsport, do you have any more info on the starving port with a TB in this setup. The thought had crossed my mind. My TB will be in the same orientation as J1NX3D 's pics, although it will be closer to the manifold.

I chose the inboard mounting IC because 1) I've got all that extra space in front of the motor, 2) I don't want to drill out the welds to pull the front panel off(!), and 3) with ducting/shroud, the IC will get just as much fresh air as in the 951 mounting space. Heat soak shouldn't be a problem as the IC will sit right on top of the radiator and the rad doesn't radiate much heat.

I appreciate the feedback! This is new territory, so there are bound to be things to come up.

nick

Racing · Joined: 27 Apr 2004 Posts: 374

DO NOT!
I repeat,DO NOT...
Weld an intake elbow to the OEM plenum like showed there.
That is a SUREFIRE way to get pressurewaves and distribution probs further up the road.
If you need to alter the OEM plenum and need to have it installed the way in the later pics Nick,do so by introducing the boost into the plenum by cutting that 3" pipe(or whatever)at an angle and weld it to the OEM plenum alongside the underside of the plenum.
Another idea to consider,doing so,would be to make the opening SMALLER in diameter at the entry(which...as i said should be a long slit)as long as its area(the slits that is) is larger then the TB.
This cut slit will then work as a pressure diffusor,keeping pressure waves within the plenum to a minimum at least.

Nick.
I read the part about not getting out of hand,but welding up a plenum to fit of your own aint all THAT much work then using the OEM per description.
If you´re worried about flanges against the head just cut them off an old OEM and be done with it.
In all honesty,per todays knowledge the OEM plenum is to small in volume.
For the 931 engine count on something like 2,5 liters total.
If you need runners...check these guys out;http://g-e-t.biz/
Take a look at what i´m talking about;http://g-e-t.biz/bilder/runner02.jpg
Cost?
An estimate to your doorstep would be 150$ for all fours.
They´re made by putting pressure to aluminium tube in a lathe.
Just connect them as i did by 4 rubber hoses and some clamps.
Work wonders.

I´ll be sure to put up some pics of the one i´m putting together for the mec asap to give you an idea of how it´s done broh.

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Hey Racing,
Thanks for the feedback. Obviously the extra length of pipe on the above intake is going to do all sorts of strange things to pressure waves, top end response, etc. But, is there anything wrong with positioning the TB off that end of the intake (i.e., cut a hole in the end of fab up a mount for the TB right off of it)? Pressure waves are still bouncing around the same as stock, the inlet air just comes from a different direction. Thinking about it, I don't even believe the #1 cylinder will get starved since it's drawing off the plenum, not the TB.

The venturi's in your link look like art and I'm sure they would improve the VE of the engine. But, I'm not going for absolute limits, just shooting for a solid 250hp at the crank. Which shouldn't be much trouble with EFI/programmable ignition, and an intercooler alone.

nick

Racing · Joined: 27 Apr 2004 Posts: 374

nick.
Have in mind-with all th respect in the world-that the 931 is a bastard built in haste by Porsche outta a lot of stuff that was left over in the pts bin.
That,coupled with the fact that 25yrs has passed and that we´ve learned a lot...
If you´re to use that approach by all means make sure that you fab the whole deal in such a manner that where the tube comes to connect to the OEM plenum you design a diffusor in.
Ie; make an opening SMALLER than the tube u use and LARGER in area then the TB u use.

macBdog · Posted: Wed Jun 15, 2005 9:20 am Post subject:

Racing, do you have any details/plans for the plenum/tb setup on your car? I saw some pics the other day, it looks great.
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Racing · Joined: 27 Apr 2004 Posts: 374

yeah.i guess i could start takin some pics of the install as its progressed far enough to make any sense to anyone interested.
Will do so,and post at first chance.

special-tool · Joined: 08 Jul 2005 Posts: 64 Location: Bethel, Ct.

There is a myth perpetuated by vendors who sell upgraded 951 intercoolers (vendors who have never seen the power out of a 951 that I have) that the 951 cooler is sub-par. I can tell you that the STOCK, 100% unaltered 951 cooler is more than up to the job of 575-600 HP.
If you breech that with a 2 valve 2 liter 931, I will kiss your feet.
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-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Agreed, although the endtanks can definitely stand for some smoothing, which I believe is what the aftermarket 951 IC more or less go to. Just allows for less pressure drop and better turbo performance all around.

nick