Carl Fausett

We have just got in our first batch of 32v intake manifold spacers, (photos below). I am having them cut from 6061 aluminum by a CNC-controlled water-jet. The bolt holes are chamfered, and the kit will come with the 15 bolts you need and gasket sealer as shown. I plan to go to market at $139 for the complete kit.

The function of the intake manifold spacer is to a) enlarge the plenum thereby improving HP at WOT, and b) move the side walls of the plenum out and away from the runner bell mouths so that the individual runners can get more air, more equally, at WOT.

We know they work. What we do not know is how MUCH they work. I have read threads reporting gains up to 50 HP on built-out engines, but never seen a dyno chart to support those claims.

I would prefer to have actual dyno charts to show what the improvements are on a SC-equipped and a stock 928. I can get the dyno charts of the SC car (the car in the pics below is my Stage 2-equipped 504 HP 928) but I do not have a NA 928 for the stock dyno test.

Would any one of you with a stock 1987-1995 928 want to participate? I need a stock 928 in good running condition, preferably with an attractive engine bay for the before-and-after photographs. I will pay for the dyno sessions - there will need to be 2 of them (before-and-after) unless you want to install the spacers while the car is strapped down to the dyno - which certainly could be done.

These spacers are maxed out... we made them just as big as we could for maximum HP gain without requiring modification or relocation of the stock fuel rails. The fuel rails do have to be removed to get the side covers off and the spacers on. I installed these in 1.5 hours, taking breaks to take pictures.

Let me know.

oz928s4

When is some one going to cut a set of phenolic spacers to isolate heat from the intake.
This stuff is amazing...I have used it on an application and it made like 35 degress cel difference from block to intake.
Thats gotta be worth giggies at least 20
Sorry Carl I was in the right street wrong house...I thought we were talking about intake to head...my bad

Z

You mean like these?

Lizard928

Z I dont really see the point of phenolic for that location.

he was refering to between the head and intake manifold.

Z

I agree that there's no real performance benefit to having it be phenolic instead of aluminum there. I used phenolic because it was cheaper, still had the same thermal expansion characteristics as aluminum, and it was also easier for me to make them from the phenolic material than it would have been with aluminum.

oz928s4

Yep thats the business...between intake and head...the stuff really rocks and is a cheap HP> that being said the phenolic is not cheap but worth every cent

mark kibort

I might be game for a try Carl. Ive always wanted to see what those spacers could do. I was able to do a mock up of the dual throttle body set that used plates like these and was able to get them on without moving the fuel rails. Is it possible to get these on without movng the fuel rails or is it a must?

How do you know they work? I'm asking because i think Devek tried them and didnt see any gains, but they might had other things going with their dyno runs.
I think they will too!

Mark

mark kibort

There is already a very thick rubber gasket separating the intake to the heads. It doesnt matter, when idling around without air flow to the intake, its going to heat up. Under WOT conditions, you would be amazed how cool the intake is even though the oil is at 250F! the transient time is very short for the air in the intake under WOT conditions.

oz928s4

Mark
rubber still absorbs heat and as such transmits heat...phenoleum actually repels heat..it is to dense to even absorb heat. The results of cooling an intake tract by installing phenolic spacers is irrefutable.
You guys running blowers should be all over this ....seriously. Water injection is another excellent means of reducing intake heat while adding to the intake charge...this technology has been around since they had to introduce water injection to the supercharged WW11 spitfires to stop them "falling" over at bigger RPMs. Altitude and less oxygen played their part to boot but primarily it was to cool the intake charge down and add HP

ROG100

Carl,
Awesome product as always. You saved us from having to make some.
How wide are they? Will they allow the use of the stock injection covers?
Either answer will do.
Best,
Roger

Carl Fausett

On the topic of intake manifold spacers from the heads - you seem to be forgetting it is a 90 degree aluminum V8, and as it heat cycles, the heads move away from each other. The OEM rubber intake gaskets are thick and beaded to allow the engine to move independantly from the intake manifold, as required.

I would be concerned that your non-elastic phenolic spacers would fail in this application.

Carl Fausett

Back to the topic at hand:

Roger: the stock fuel rail covers could go back on with only 2 small notches cut into the inside edge to permit the cover to slide over the allen-headed screws. I almost did it myself before I took these photos. Fortunately for us, the fuel rail covers are already offset to the outside - in the direction we need.

Mark K: how do I know it will work? I'm just an old hot rodder at heart. We know carburator spacers work and throttle body spacers work all for the same reason(s) that larger plenums increase the available plenum load and also increase the air density caused by slowing the air flow down in a larger chamber.

I expect them to work even better on the 928 as, on the Left side, cylinders 5 and 8 have the intake runner bell-mouths too close to the sides to draw air smoothly from the entire circumference of the bell mouth. On the Right side, cylinders 1 and 4 are the most pronounced, but not so close as on the left side. However, they are located inside the other intake runners, for cylinders 6 and 7 and I believe they will compete with and restrict the available air for 6 and 7.

But still, even with throttle spacers and such on my side (proven to work) it's all hypothetical until I get before-and-after dyno charts. So I'd rather have that than guess.

Even if they only post a 10 HP gain.... look at the return per dollar and time. There are few places you can spend $100 and get 10 HP in about 1 hour.

dprantl

Carl, do you know why Porsche would redesign the intake to make it so narrow when they had ample space on either side to make the boxes longer (like the early 32v)?

Dan
'91 928GT S/C 475hp/460lb.ft

Carl Fausett

Dan - now your into the stuff of conjecture and legend.
Some engineers that have since retired and were part of Projekt 928 development suggested that orders came down from above to de-tune the 928 so that some 911 derivative would always remain top-dog in the Porsche line up.

There are several times the 928 out-shown the 911 (the Al Holbert Land Speed record for a production automobile comes to mind, and the 928 GTS, and the 1987 S4, and...) and we are told that the 911 community (which paid the bills at Porsche in those years) were none to happy about it.

Some believe this legend - it does seem to explain a few things that are otherwise unexplanable. The lousy camshaft profiles on the GTS camshafts, these intake plates being too close to the runners, and others.

Whether you beleive this or not - the marketing figures do confirm that they deliberately kept the 6 cyl 911 producing more HP than the 928 year after year. And frankly, it would take a conscious effort to keep a 8 cyl motor down in output below a 6.

Jadz928

That's interesting. BTW, nice piece Carl. Give me phenolic and I'm all over it.