That's really the issue - what are you supposed to use when you measure those smaller diameters, like pin diameter on the piston and valve guide ID (head and the actual guide). I feel like I am in the dark on this.

Have to look up something called "pin fitting"

 

Won't there be less combustion chamber pressure too?

 

On this point I'm not really saying that - I'm just saying the absolute pressure in the crankcase will be lower there, and therefore the oiling behaviour (wrt lubrication) there will be like a vacuum pump (5"Hg) car in Phoenix.

I think Denver will have a benefit for consumption - but the reason I don't have hardly any oil consumption now is not because of the vacuum (though that does have more value as a stand alone item than I expected) but because my evacuation path is now separate from the intake - so I have more control over the level and can make my separation path longer to be more effective without just boosting crank pressure through a more restrictive separator... with this step the oil separation effectiveness is much much better. I still have an oil cloud and oil in the blowby - so I'd expect continued consumption unless you have a way to strip it out & recycle it with a much better separator.

I do actually still ingest the net blowby evacuation gasses via the CAI (not via the throttle body) but its really really clean now and that connection really doesn't affect the flow rate.

Alan

 

Obviously I've been saying this. I don't think you need to massively port though and normal conditions can be quite like this. The crankcase is pretty open to atmosphere already - the dual throttle body ports are probably a total of approx a 1" vent. One is a mild eductor that will work at high flow to create some suction on the oil fill neck port - but this is primarily a crank flush mechanism because the outer ring is always open - to the cam cover (via a slightly restricted port). Only when blowbly overwhelms this vacuum flushing does the outer port also flow out of the crank - under blow-by pressure. There is also a very restricted intake port on the other side of the filler neck - its doubtfull this flows much but it will help to do some flushing at idle too.

I'd expect pretty much local atmospheric pressure in the crank under many conditions - except when blowby is enough to pressurize it. Given a dirty air filter I could also imagine the engine creating its own little mild intake vacuum at the throttle body port at high flow levels.

Alan

 

My only observation at this point is that Alan likes to type his name at the end of every post, while others prefer to include their name in the signature section.

I may be on to something there...

 

It just looks better that way... above the line...

Alan

 

Your caliper will tell you nothing. Need a micrometer and a bore gauge.

I can loan you a bore gauge that measures the pin bore. I have three different ones, depending on the size of the hole. No one that is serious about building engines can be without these tools.

Porsche uses a very tight wrist pin, which is completely counter to what you need with a dry sumped or vacuum equipped engine. Like I've been saying, builders of those engines run much looser pins to compensate for the reduction of oil that the negative crankcase pressure causes. They also increase the endplay of the pin, to allow more oil to get into this area.

 

Rob - what was the story on this engine? do you know much about how it was run before the catastrophe? mileage, racing use, home altitude? etc. Question relates to whether the engine was pushed hard or just run typically (whatever that really means...?).

From what Greg says if other GTS cars have blued pins then it may mean Porsche didn't design it well enough even for routine typical use OR perhaps just that some specific forms of usage create this issue.

That aside - I still don't really see any reason why lubrication would be clearly worse under a mild vacuum. The whole environment is subject to the same pressure with pulse variations the same as (or likely smaller than) in the stock case. Certainly can see no rational for splashed oil being sucked from anywhere we care about here - it doesn't work like that without differential pressures to create flow.

I believe the extent and mobility of the oil cloud must be reduced with vacuum (from observed results) which would suggest less mist and more liquid oil to fling about. However I don't pretend to know what exactly is happening in there.

But everything I've seen tells me it isn't very much different - to its mildly better, and IMO certainly no worse than living somewhere really high up in the mountains.

If wrist pins are routinely blue in most cars then its an issue for all GTS owners to worry about since these blue pins almost certainly weren't in vacuum pumped cars... Seems strange then that we don't see issues of massive little end wear reported as a major concern - do these just soldier on forever on the edge? If its only in some cars then what causes it to be for just those cases?

Alan

 

I have a "very good" dial bore gauge, but its not for the pin bore sizes. I can obviously do the OD with the micrometer.

How do you measure the ID of the valve guides?

 

Alan-

1993-2001- First 70,000 miles in metro NY/NJ/CT area.
2001-2003- 7000 miles in Florida
2003-2009- 78334 to 99673 - Portland, OR

The OR owner did track it, and he took part in the 150 mph class in the 2004 Pony Express.

There are some receipts for a new front bumper cover and soft parts for the front end from late 2005, as well as receipts for the Koni Reds, Eibachs, Ott links, and corner balancing. The car was completely repainted in 2006.

So I know it was tracked some during Tom's ownership , but not sure how much. We're way beyond any statute of limitations, if any of the PacNW guys or Tom know more about how much the car got tracked. It's all good at this point.

 

Not sure on how much it got tracked...but I bought the track rims and hoosier tires from Tom....they weren't too worn out... (but they are now..).. If I recall...it was sold with the note that it was consuming oil (about spec for a GTS..1 liter per 600ish miles)...hence the bargain price..

 

Yep, the other Tom was very forthcoming about the oil consumption issues. Ironically it didn't use any measurable amount in the 650 miles I put on it the day I drove from Portland to San Francisco and stopped in at Jim Morton's place. I don't think I checked it at any time between SF and the top of the Grapevine, where it blew chunks.

Looking at the Grapevine on Google Earth, from the time I downshifted and started up the hill in 4th gear,(~4000 rpm, maybe 75 mph) I think I went about 7-8 miles before I noticed the oil pressure dropping and backed out of it. Should have turned it off at that point but who wants to be stranded on an uphill grade on the 5 on a Sunday afternoon?

 

I've attached a couple of emails that Tom posted when he was selling his car..looking back at some of his other posts...I gather he did some PCA DE type events..and not real racing ..... and of course the Pony Express event you mentioned earlier.. (perhaps most of the damage started with that run...oil ingestion pounding the bearings).

-------------------------------------------------
Been a while since I've spoken with most of you. I've decided that
it's time to sell my GTS. The short story on the car:

$32,000.00
'93 5-spd
approx. $98k miles
midnight blue metallic w/ light grey interior
recent very nice paint (about 2 yrs. ago at Roth & Miller in Portland)
-at this time i had them do a side molding and rear wiper delete
(looks very clean)
12 way heated seats
Alpine stereo w/ ipod adaptor and custom subwoofer in spare tire
Koni/Eibach external adjustables
Louie's drop links
Carbon fiber x brace
timing belt changed about 4.5 yrs ago at $75K miles (when I bought
the car)
maintained at Stuttgart Autotech in Lake Oswego since I purchased

comes with original factory wheels

negotiable:
18" HRE 545's w/ Pilot Sport 2's 295's in the rear and 235's up front
(in very good condition)
17" Kinesis track wheels w/ 315 & 275 Hoosier's


known issues:
driver side rear wheel liner needs replacement
oil leak around oil pan gasket
passenger side seat heater not working
leak in a/c system (won't hold a charge for long)
--------------------------------------------------------------------

I'm throwing this out to the group before it goes to the mass market.

Many of you know that I have had my GTS for sale. I took it in to
Stuttgart Autotech here in Lake Oswego to have them take a look and
analyze the oil consumption issue. Bottom line is that at some point
in the not too distant future, a rebuild of at least the upper engine
will need to be done to replace valve stem seals, etc. They said if
they have to go in and rebuild the entire engine, labor could go as
high as $7,500 and the parts could end up being just as much. I am
looking to sell it in the low $20k range if anyone is interested.
The car is absolutely beautiful inside and out, and has extras. It
will make someone a very proud owner. I'll be happy to answer any
questions and send out pics as well.
-------------------------------------------------------------------------------------
I have the following track goodies for sale:

AutoPower roll bar that has been mounted in car once and then in
storage for the last four years. $375
5 pt. G-Force camlock harnesses -red In perfect shape, approx. 5
years old $75
AutoPower video camera mount for rollbar $75
2 Sparco Evo 2 race seats (black) perfect shape $550 each or $1000/pair
Kinesis K5 wheels in 17x10 & 17x11 w/ 275 & 315 Hoosiers $1750

 

Hah! - that's pretty normal consumption for the oily ones..

To Greg - how different are the shape of the big ends between rod types? - are all GTS rods ends shaped like Robs? They seem really chunky & blocky like they would churn the oil quite a bit.

I seem to recall your Carillo rods had very smooth low profile big ends...

Alan