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Backstory: I rebuilt my engine (2002 C4S) with a 3.8L from LN with Nickies and JE pistons. Car has stock airbox, stock ECU, but X-pipe with 200-cel cats, using UAOS. Followed all the recommendations (new injectors, MAF, break-in oil, etc..) for rebuild from LN. Addressed a few vacuum leaks, found via a pressurized smoke machine, but nothing major - the crankcase is not leaking smoke. My issues are my tailpipes are sooty, my oil is darker than it should be (showing carbon in it whenever I change it). I'm going through oil at about 1qt per 1,000 miles. I'm running Brad Penn 10-40 per LNs recommendation. And my manometer test (car warm at idle AC off) is reading -2.4. (Per Skip the manometer reading will be about 3.5-4 for the manometer when using an UOS). Note, I ran the manometer test with the purge valve plugged just to take that out of the equation.
Does anyone have any suggestions of what to check next? Here are my Durametric readings:
NOTE: MAF was generally reading about 17, but fluctuated from 13-19. Is this normal? 02 sensors voltage fluctuated between .10-..80.
When testing crankcase vacuum, what you DON'T want it is a "high" (negative) vacuum reading, that is dangerous, a low reading is not ideal and indicates a problem, but is not dangerous.
I would suggest a test of engine vacuum, in HG , a leak down test with a quality tester, and a blow-by test. I would also recommend doing the smoke test again...
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A quart per 1k miles oil consumption is not that bad, a lot of new engines do this...
When testing crankcase vacuum, what you DON'T want it is a "high" (negative) vacuum reading, that is dangerous, a low reading is not ideal and indicates a problem, but is not dangerous.
I would suggest a test of engine vacuum, in HG , a leak down test with a quality tester, and a blow-by test. I would also recommend doing the smoke test again...
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A quart per 1k miles oil consumption is not that bad, a lot of new engines do this...
I'll get those test lined up.
Do you think the low manometer reading could also be due to rings still not being fully seated? I only have 5K miles so far. My pistons came from LN with JE’s “SX” ring pack. These are a chrome ring package that LN says is Nikasil compatible. I believe they offer these for durability purposes but my research shows how break-in could be more challenging versus something like cast and phosphated rings.
Do you think the low manometer reading could also be due to rings still not being fully seated? I only have 5K miles so far. My pistons came from LN with JE’s “SX” ring pack. These are a chrome ring package that LN says is Nikasil compatible. I believe they offer these for durability purposes but my research shows how break-in could be more challenging versus something like cast and phosphated rings.
Those rings would have been an XS ringset; we have switched them interchangeably with JE's JG ringset depending on availability as both ring sets work well with Nikasil. The XS aren't a hard chrome ring but rather CrN coated. The problem you have is that no one really makes or uses cast 2pc oil controls like those originally supplied by Mahle and used by Porsche, and even if they did, with the short compression distances on these modern pistons you would not be able to fit the wider, older style rings.
Most modern pistons, even those from Mahle or Porsche, supply similar CrN coated steel rings for Nikasil bores. They can be difficult to break in, but at 1 quart per 1,000 miles I'd wager they are seated and I would not be too concerned. That's what I would consider as average consumption for an engine with Nikasil bores.
My 2006 GTI has used a quart every 700 miles for the first 130,000 miles of its life and just now stopped burning oil. It ran 8100 X-Cess until out of warranty and has run Driven DT40 since. Long story short, one quart every 1,000 miles isn't going to hurt anything.
Another oil you might want to try is Liqui Moly 2040. We've had several customers report lower oil consumption with that oil. I would advise against using any additive such as LM MoS2 or Ceratec as in my experience adding more friction modifiers tends to make engines consume more oil than one with less friction modifiers, hence our original recommendation to run the Penn Grade oil in your situation.
Last edited by Charles Navarro; 05-24-2022 at 06:30 PM.
Those rings would have been an XS ringset; we have switched them interchangeably with JE's JG ringset depending on availability as both ring sets work well with Nikasil. The XS aren't a hard chrome ring but rather CrN coated. The problem you have is that no one really makes or uses cast 2pc oil controls like those originally supplied by Mahle and used by Porsche, and even if they did, with the short compression distances on these modern pistons you would not be able to fit the wider, older style rings.
Most modern pistons, even those from Mahle or Porsche, supply similar CrN coated steel rings for Nikasil bores. They can be difficult to break in, but at 1 quart per 1,000 miles I'd wager they are seated and I would not be too concerned. That's what I would consider as average consumption for an engine with Nikasil bores.
My 2006 GTI has used a quart every 700 miles for the first 130,000 miles of its life and just now stopped burning oil. It ran 8100 X-Cess until out of warranty and has run Driven DT40 since. Long story short, one quart every 1,000 miles isn't going to hurt anything.
Another oil you might want to try is Liqui Moly 2040. We've had several customers report lower oil consumption with that oil. I would advise against using any additive such as LM MoS2 or Ceratec as in my experience adding more friction modifiers tends to make engines consume more oil than one with less friction modifiers, hence our original recommendation to run the Penn Grade oil in your situation.
Charles - Thank you for the reply, clarification, and suggestions. I'm not as concerned about the oil consumption as I am about the low manometer reading and carbon in my oil. Would these two things be related to the rings and linings?
Charles - Thank you for the reply, clarification, and suggestions. I'm not as concerned about the oil consumption as I am about the low manometer reading and carbon in my oil. Would these two things be related to the rings and linings?
I don't know the complete history, but I can make a general statement that if fuel trims aren't right off the get go, fuel trims can affect ring seal negatively which often can require deglazing of the bores and re-ringing of the pistons to correct. I can also tell you that the Penn Grade starts to drop off around 2k miles and is done by 3k miles, so usually we'll see higher consumption and lower manometer readings on used oil than fresh oil. Out of curiosity, how many miles were on the oil at that time?
I don't know the complete history, but I can make a general statement that if fuel trims aren't right off the get go, fuel trims can affect ring seal negatively which often can require deglazing of the bores and re-ringing of the pistons to correct. I can also tell you that the Penn Grade starts to drop off around 2k miles and is done by 3k miles, so usually we'll see higher consumption and lower manometer readings on used oil than fresh oil. Out of curiosity, how many miles were on the oil at that time?
Somewhere between 500-700, with one DE event in there.
Somewhere between 500-700, with one DE event in there.
A track day is hard on the oil, so I'd expect the manometer reading to be higher with fresh oil. Like I mentioned above, you might try the LM oil. Ideally you want to stay away from any oil with ester (group 5) or oils with lots of FM (moly, etc) as these can increase oil consumption by their very nature. Depending on your ambient air temps, you might even try going to a 5w50 or 15w50 instead. You might find another oil that works better in your engine and will further reduce consumption and might improve the manometer reading.
As Skip recommended, I would smoke test the engine again to be 100% sure there are no vacuum leaks.
A track day is hard on the oil, so I'd expect the manometer reading to be higher with fresh oil. Like I mentioned above, you might try the LM oil. Ideally you want to stay away from any oil with ester (group 5) or oils with lots of FM (moly, etc) as these can increase oil consumption by their very nature. Depending on your ambient air temps, you might even try going to a 5w50 or 15w50 instead. You might find another oil that works better in your engine and will further reduce consumption and might improve the manometer reading.
As Skip recommended, I would smoke test the engine again to be 100% sure there are no vacuum leaks.
Will do. I've lined up a smoke machine, vacuum gauge, and am building my leakdown cap. Hope to get to it within the next 2 weeks.
05-23-2022, 12:22 AM
Low Manometer Reading - Now What??
