ramcram

What I did to vent my 86ROW 32V and why I did it.
Adding the supercharger was the first trigger and seeing all the oil in the plenems after only about 20,000km was the next trigger.
Firstly, I don't race this car. It has done a few short circuit hill climbs and a few fun day motorkahnas but that's about it, definitely not all day track sessions. So cambox oil packing is not seen as an issue.
Secondly, I did not want to vent to atmosphere. Too easy, too messy and, well, we have come down out of the trees after all.
So I had to stop boost pressure from entering the crankcase and had to vent the crankcase during both negative and positive manifold pressure driving.
I fitted cam cover elbows to both left and right covers, using a spare pair I had. So one is restricted and one is not on each cover, just a Porsche did on the right side only. I copied the GTS, to a degree, bridging the left rear and right front cam cover's unrestricted elbows with a 16mm line to allow any balance flow that may exist.
Then the 2 restricted elbows, rear right to front left were joined with a 16mm line and an 8mm 'T' coming from the top of the filler neck.
I can say at this point that if I do this again, I would 'T' into the 16mm line and connect it to one of the filler neck's bottom larger breathers, so the cankcase gases don't have to swim upstream as it were, through the cam box oil return ports, to vent out as they do.
When the 16mm line passes the 'T' from the filler neck, it drops down passed the front of the motor and connects to the inlet of a 'Provent' air/oil separator.
The 'Provent' oil return line passes through a oneway valve and into the sump via the little steel plate used by the earlier motors oil system.
The 'Provent' outlet rises vertically with a 'T' piece. One leg of the 'T' rises to the front of the right cam box where it goes into a vacuum valve. In fact, it's a Bosch blow off valve exactly as I have for boost release. This vacuum valve then goes on to connect to the 14mm fitting in the elbow under the throttle body, where Porsche originally connected their cam box vent. More about this valve in a minute.
The other leg of the 'Provent' oulet port 'T' goes up to the pipe from the aircleaner the the supercharger inlet and connects through a PCV valve, in fact 2 PCV valves because I felt they were quite restrictive.
Under normal driving, say below about 3000 RPM, with negative manifold pressure [vacuum], the blow off valve is held open as is its twin, the vacuum vent valve, allowing crankcase gasses to be drawn through the air/oil separator into the motor and burnt up.
Under more severe driving, such as higher revs with no/low vacuum and or boost pressure, the 2 vacuum valves are forced shut by their internal spring pressure. As they are both controlled by the same manifold vacuum, they shut together. This means that as the blow off valve closes creating positive manifold pressure, the vent valve also closes preventing that pressure from blowing back into the sump and creating havoc.
In this boost state, piston blow by is likely to be higher than steady state driving, so crankcase breathing has even more need to be considered. The gasses can then vent from the air/oil separator via the 2 PCV valves and be drawn into the intake system behind the air cleaner.
I've done a few thousand km of both open highway cruising and some very steep mountain roads [18% gradient] [even three demo hill climb runs] with this system and the oil consumption is quite low, almost none and no smoking.
I have to replace the brake booster soon, so the right plenem will be off and that will give me a chance to see how much oil is getting in there.
I have the 'Provent' mounted quite low which means that oil in the pipes will naturally fall to it on intake and has to be lifted if it gets through the separator. When the engine is stopped, any oil in the pipes will run down naturally to drain back to the sump.

FUSE69

Where do you introduce fresh air into the crankcase?

I believe you will need to allow fresh filtered air in somewhere, so as to reduce the vacuum in the crankcase... Or more than likely at idle or off throttle where you have the most vacuum, you will suck in air via cam cover or sump gaskets...

Also, have you restricted the vacuum at idle so as to avoid a high idle? I think the standard setup only draws vacuum through a 3mm dia restrictor at idle... Essentially a 'designed' vacuum leak...

hacker-pschorr

I see a BEGI on the firewall so I'm assuming that is your fueling under boost solution.

What are you doing about timing under boost? Is this a standalone with custom maps or do you have access to a SharkTuner?

ramcram

The issue that compounds most of us is crankcase compression. Some deal with it by fitting a vacuum pump where the emmissions air pump was, to 'suck out' the sump. The sump is a sealed unit except for an allowance for 'blow by' to escape. Porsche vented it from 1 restricted cam cover elbow, the top bottom of the filler neck.
You are right about a designed vacuum leak. This is managed by the 'Idle Control Valve'. When the throttle butterfly is closed at idle, air enters the inlet manifold through the sump vent system and the idle control valve. the idle setting procedure sets the amount by which this will be adjusted to achieve the 680RPM.

ramcram

Yes, that does the rising rate fuel pressure. Not happy with it yet. It starts well cold, although it runs very lean during cruising until the temp gauge starts to move. The AFR needle jumps up where it should if I accellerate. Once the engine is warm it sits around the 14.7 and shoots up on accelleration. But warm, the engine sometimes needs the slightest amount of throttle to get is to stay running for the first few seconds, then it behaves perfectly. Strangely, when it wants help to start and I don't do it, it hunts, suggesting to me a rich mixture but the AFR gauge says lean. Acts as if the cold start map is not working. It only does this for a few seconds, so I'm living with it for now.
Everthing else is stock at the moment and may/may not stay like it.
I want to run it on the dyno and get the tuning correct but first want to alter the cooling and get the engine temp and volt meters to behave as they should. I fitted a 130 Amp alternator and all new engine sensors but I'm not confident in their accuracy, so some checking has to be done. 26 year old wiring connections I suspect. I have had the cluster out and sent it to an instrument shop for servicing and calibration.

hacker-pschorr

If you are running stock ignition timing under boost you just found the cause of your excessive blow-by.

You should fix that before trying to fine tune the air / oil separator system.

ramcram

So far I haven't seen any indication that the blow by is excessive. I did all this as the supercharger was being fitted as a part of the installation.
Of course it's early days and I've not seen inside yet, so I might get a nasty shock but so far the Provent seems to be doing its job.
I'm about to remove the supercharger to alter the way we have achieved the belt alignment and that will tell me if my boost breathing path is acceptable or the impellar is getting oiled.
Otherwise I'm pleased with it.

hacker-pschorr

Really?

I would say you do, fix that first.

Rule of thumb, boost + stock ignition timing (and / or poorly tuned ignition map) = detonation.

Detonation = excessive blow-by

If you say "I cannot hear it knock" you are correct.

The S4 and later cars can get away with this because they have knock sensors. Still not perfect but at least something to dial back the timing when the engine starts to knock. You engine and mine do not have such protections.

You have a nice looking setup, small tweaks will be the difference between enjoying it for years to come and looking for engine parts.

Just my advice, most ignore it.

What brains are in your car? LH 2.2 and EZF?

Imo000

So retarding the timing under boost will remove most of the blowby?

hacker-pschorr

I don't play guessing games when it comes to tuning an engine. That is what measuring instruments are for called dyno's (be it engine or chassis). If you don't know how to properly tune an engine on a dyno to find the detonation threshold (without making it detonate) then pay someone who does.

What I do know is stock ignition timing + boost is a horrible idea. So if nothing else, start there.

His blow-by is excessive and his timing it too high. He could have other issues going on but you have to start somewhere.

ramcram

And very good advice it is Hacker.

The reason I fitted the vacuum valve was to prevent boost from 'back flowing' into the sump and it is working.

I agree with you on detonation. When I had my 94 GTS and the filler neck 'O' ring shrunk, it put oil over the knock sensors and the difference was amazing on a stock car.
Porken suggests a 'KnockLite' but I've not been able to source one yet.

I should have explained myself a bit better but the crankcase vent changes were done BEFORE the blower was fitted, in preparation for it. I actually ran the car a bit in this config before the blower was hooked up, to check for breathing issues. Also did a heap of other service stuff in preparation, like, O2 sensor, injectors, water pump, timing belt, iridiun cooler plugs, plug leads etc.

yes the stock brains are still there although I did change the chips a few years ago. I can't remember who made them but they came with plenty of promises??? I have a spare set of the 2 brains, so I fitted the new chips to the spare set, went to the dyno, ran it stock, swapped out the stock for the modified and dynoed it again. As suspected, the results didn't match the claims but at least they weren't worse.
I left it with the modified chips because although they didn't raise the tq or hp, they do level out the flat spot in the middle, giving a constant hp curve.

I'm keen to find out if Porken's modified chips would give any advantages to this setup?

It's still very much a 'work in porgress' and I'm by no means stopping where I am. Hence my keeness to get this kind of valued feedback.

Imo000

You didn't aswer my question and I was actually serious.

ramcram

It is quite possible that my engine timing is not optimal because we have not been there yet and I'm waiting on the various Porken options, [I now have his timing belt tensioner and it's great] but I have no reason to think that the engine blow by is out of the ordinary. On the contrary, monitoring to date says the current venting system is working well and as planned.
As I said earlier, the 'proof of the pudding' will be when the plenems and the blower are removed in a week or 2 for other work and we'll be able to see how well the Provent has handled the normally oily 32V motor.
My whole idea of altering the breathing was not to address any issues that this engine had specifically, I should have been clearer about that but I tend to rattle on assumig poeple know what I'm thinking. My plan was to address the known and well documented manifold oiling issues these engines are famous for.
Secondly, the mechanics of forced induction mean that normal, healthy and acceptable blow by, that piston clearance and rings with gaps can't stop, WILL increase as boost increases. So I set out to make a plan for this BEFORE it became an issue, by devising a breathing path that did not vent to atmosphere and did have a system that would attempt to remove/reduce the oil in the crankase vapour. So far I'm happy with the results but as I'm only a short way down this path, I'm well prepared to be further educated. These machines are good at educating?

rad_951

Are you sure the one way valve to the sump is needed? The OBs have a tube from the oil filler to the sump without a one way valve. I think the oil filler is open to the top of the crank case in the OB, so I think Porsche wasn't worried about oil blowing back up the tube. A supercharged engine may be different.

Cosmo Kramer

Have you installed the chip I gave you yet?