Rich9928p

A friend of mine who is a member of the Porsche Club 928 Germany passed on an interesting German language Porsche AG document regarding upgrading any S4 and GT (and early GTS) to the 1993 GTS improved crankcase ventilation system. It provides the part numbers and procedures with pictures. The benefit of this upgrade is improved crankcase airflow at high rpms.

I have a two page translation of the document (thanks to Nicole for some tricky language sanity checking) that I can share. Just drop a note to info@electronikrepair and I'll email it. It is about 900 Kbytes in size.

To clarify the diagrams, the left side is what pre-93 GTS systems have and the right side is what later 93 GTSs have. One very clear item is the left and right banks are interconnected, so pressure is more constant in both intakes ... this means that air doesn't have to flow down around and under.

Why did the factory do this? I don't know but you can assume they had their reasons. However, they did do it for the GTS.

DR

Hi Rich,

Great info! We have been selling "informal" kits for this upgrade for a few years. Greg Schickel just did one on his 93 GTS a few weeks ago (even some of the earlier 93 GTS's did not have this upgrade). It is easy to do and not very expensive, especially if done when removing the Intake for maint. or coating.

I will have a detailed KIT for this upgrade on the website in a few days.

heinrich

Sucking oil off the rear of the passenger's head straight into the intake is not IMHO a good idea. How would it be to connect both covers across, and just vent the filler neck to the intake? That way:

1. Pressure is released into the intake but little oil will get out at the filler, at least less than from a head and
2. If an American drives Anti-clockwise around an American track, oil will undoubtedly dam under the passenger's rear breather outlet, which will simply be circulated onto the driver's side and sucked down by the crank, creating a draught through the crankcase and across the heads.

Why would this not work?

Adam C

I saw this in the workshop manual. What are the benfits of this system?

928ntslow

I think someone (may have been Louie Ott) came up with a way to improve upon this and relieve the "oil well" that collects in the bottom of the throttle body. I just can't remember right now where I had seen this.

mark kibort

i have no breather changes on the holbert car and regularly spend time at near redline on most all straights at the track i visit, as well as near redline off throttle decells. (lots of them at Road america) no problems with oil being pumped into the intake, intake system has very little oil residue.
think its a non issue guys. seen more problems with folks trying to get creative here than those that just leave the design alone. however, there could be a need for those with 7k redlines and even higher vacuum on decel like those with strokers.

mk

heinrich

"works for me" right Mark?

Oil ingestion via intake off cam cover is a MAJOR problem. Not for everyone but many. It was for me. And it is for some supercharged engines I know of. As well as some strokers and at least a few GTS's.

928ntslow

My GTS collects oil in the bottom of the throttle body. I noticed this upon removal. Enough to where you can pour it out, not just residue. I found the write up I was referring to in my last post. It is worth a read and is in conjuction with this conversation.

Oil Control and Breather

mark kibort

maybe im injesting more than i know! Ill have to follow it a little more closely.

wonder if the baffles on the breather tubes are different on my car's engine.

mk

mark kibort

great pics on OTTs 928 site.

CMW

The premium set up for Andy K's Supermodel twinscrew set up has a similar system in place.
As of right now it just vents, eventualy for "smog purposes" it is going to be rerouted... I believe through the exhaust not the crankcase.

The advantages are increased HP and reduced detonation issues for my setup as I understand them.

blau928

Has anyone tried replacing the smog pump with a crankcase evac pump..? It seems that this would solve the issue and promote better ring sealing anyway...

Tube on Oil fill to A/O separator, to Evac Pump, then to the tailpipe post cat, or even a tube to the rear of the car... The intake covers could then just have filters to breathe fresh air...


Crankcase gods..... : Bad Idea...?

Nicole

It might be helpful to give us an approximate cost for the parts. Maybe you want to create a "kit" for this in your online store.

PorKen

I'm fixin' to try one of these one day (GZ Motorsports Vacuum Pumps), $199 for their basic pump.

(If I ever dig myself out of the custom parts hole I've dug for myself. )

blau928

PK,

Interesting... I also saw some Moroso units at Summitt... I will be trying a similar setup if the partial dry sump thing is not realized...

Oh, Don't worry about the parts hole. We all have a community spares section in our homes...!