S4/GTS Intake Manifolds wearing out!
 

Air wear...watch the video and opine...

No one has noticed this wear pattern? This I fear is a significant issue.

Are you seeing this pattern on all S4, GT, and GTS intakes? Or just GTs? Or...?

If you're the only one who's seen this, then perhaps someone took a grinder to it earlier.

That makes the most sense.

I think its just a gentler tool usage in this case - probably not original - but possible if it shows up on many intakes. The external grinding was solely cosmetic (gross casting swarf removal). The internal is related to smooth airflow (in this case at a port junction) - so makes sense it would be more carefully implemented. Normal air flow cannot wear things like that unless it is high pressure (not) and laden with some kind of cutting media - in which case the engine would already be scrap.

Alan

Somebody was trying to port match. Poorly. Hate to think what the head looked like.

I've media blasted about 12 of these S4/GTS intakes now, and every single one has irregular, violent, wear patterns. I may indeed be the only one seeing this as I see them all gooey and gross and clean them up right before my eyes these wear patterns appear. Notice how I already ran the issue down of possibly being manually ground down in some method with a possible objective of porting, etc. I don't think this is the issue. It is clear to me this is air turbulence, especially on this one port I focus in on in this video. Given this issue. there is remedies. I may now buy the aforementioned Cold - Spray system to render such repairs in the future if requested after consulting with the owner. This port in question will be immediately subjected to direct air and subsequent air-wear. I'll have to make Roger aware of this.

I recall hearing that the factory crudely port matched by hand some of the intakes and heads to make the German standards for claimed peak power, could be that. I think that some casting revisions also have patterns that replicate a hand grinding, but someone else will have to confirm that.

"Air wear"? Really? Millimeter amounts of metal removed by the airflow? Only in the aluminum intake runner but not the aluminum head? I'm going to go with prior grinding work to remove casting flash or attempts at port matching.

Come on guys, this is very well known - every single GT intake was portmatched by the factory. Have the same "wear" on my 1990 MY GT. Tuomo is correct - it was done in order for Porsche to make the claimed 330hp minimum from the GT engine. The late - 1990 and 1991 S4 also received the same manifolds and I some of them were used on GTS engines too - my 1993 MY 5spd GTS has the same grinding marks.

Hope this settles it

During High School & Engineering School, I worked every step of casting manufacturing (mold making, assembling, pouring, knock-out, cleaning, grinding, sand blasting, etc. - what a hot, dirty, smelly business!) at my family owned aluminum foundry. We did primarily plaster mold castings, but also made sand castings, like this magnesium intake manifold (the intake covers and cam cover are die castings). To my eye, the lightened areas are just sanding marks from finishing. We used air powered "grinders" with sanding discs or, in this case, rolled cylinders of sand paper, we called "Tootsie Rolls".

The intake runners are a separate mold (core). Any flaw in the mold (crack, or chunk of material missing) will lead to a metal protrusion of the same shape, that would need to be removed by hand finishing. This would be prior to heat treating and machining, so the casting is softer and the injector holes and other machined features are not even there at the time to use as reference. It is very easy to get over-zealous with the grinder, and we're not talking rocket scientist, either. I suspect that what is being seen I just poor workmanship at the casting house.

I just took a look at my '87 intake manifold (130K miles) that I have on the shelf and see no erosion like this. The manifold in the video has a late '88 date code, if that means anything.

Please let us know how that goes. :D

Hence my question to which there was no answer.

I agree with Cheburator. The filing on the manifold is a mechanical action that looks consistently hand induced and not by the action of in air particles driven. This is in line with 4R manifolds. Otherwise (and as Alan said), the block would have been long gone.