Detonation due to Oil Consumption?

[jckrieger]

All,

I've been getting some considerable spark knock on my CSX and am wondering if oil consumption is the root cause of my pre-ignition. Ever since I installed the forged pistons, the car has used a little oil, but last fall I hurt one of the pistons (lost a fuel injector) and now a cylinder is down to 140psi on the compression test. The car now uses about a quart of oil every 200 miles and is spark knocking as low as 18psi at 11:1-12:1 A/F ratio running premium gas with methanol/water injection or straight E85 injection. I'm planning to blow the car up at the track this weekend, but am curious if anyone else has had issues with detonation and oil use. I've never had a damaged piston that still held 140psi before...

If my problem is oil consumption, I will be buying a new set of pistons and will build my 16V motor. What are you guys running for piston to wall clearance on your high power motors? I've always been dropping std pistons in std bores and don't want to fly by what the manufacturer lists and find out the piston is getting tight while under boost.

[Speedeuphoria]

What kind of PCV setup do you have? Are you using a catchcan?

[johnl]

Ditto on PCV, catch can will tell you whether you have a lot of oil - blow by.

140 lbs is pretty good.

A leak down test might tell you whether the oil is coming from valve guide(s) vs piston rings.

[turbovanman²]

Yep, oil will cause detonation.

I am running .005 with the Venolia's, ran .004 with the JE's. Was told I could easily run .004 with Venolia's too.

[Turbo3Iroc]

What were the compression numbers for the other cylinders? I would suspect your turbo is leaking the oil. SDAC 17 going down the track I was getting very audible knock at times with a heavy 110 mix in the tank. Turned out to be the turbo leaking oil into the intake stream.

[zin]

Oil is like anti-octane, it will cause big issues with detonation. Sounds like you need to keep the boost to a min until you can fix it.

[Turbodave]

Oil can certainly cause it to knock as others have said.

The 5.2/ 5.9 Magnum engines had problems with plenum gaskets on the intakes that would let them suck oil from the oil valley into the intake causing knock, seen that on a few Rams over the years. While your setup is much different the symptoms are the same.

That 140 Psi sounds pretty good for compression, never seen a damaged piston read that high.

[moparzrule]

Did you have the cylinder's honed when you installed the pistons?

I would suspect the reason for the lower compression was that there was no fuel to lube that cylinder and the bore ''glazed over'' so to speak but only slightly since it's still 140.

But yeah I've had oil make detonation come. I tried to run Royal purple twice, both times cracked a piston with it. The only thing I could figure was the oil is so slick it was getting past the rings causing detonation. Stopped using royal purple, no more issues. Wierd.

[jckrieger]

What kind of PCV setup do you have? Are you using a catchcan?

Right now the car has the stock PCV setup under vacuum, and under boost it just vents... to the top of the transmission. The PCV is dumping more oil than normal, but I'm also boosting a lot more than normal. I plan on a complete teardown to determine the condition of the bottom end after a couple passes at the strip.

When it comes to compression, all 4 cylinders were 150psi after I assembled the engine. I honed all the cylinders, and have never had oil consumption issues with any of my previous builds. I'm not sure exactly when one cylinder dropped from 150psi to 140psi, but it was around the time I had my S60 turbo die.

The turbo shouldn't be leaking oil, as it was a new Turbonetics Stage 3 "F1"/S50 trim hybrid and only has about 2,000 miles on it. I checked for shaft play last night and it's still as tight as it was the day I installed it.

Go figure the one engine where I installed NEW pistons, rings and valve seals is the one that has the oil consumption problem. None of the plugs are getting fouled with oil, but I've had 3 turbos on this motor and they've all smoked equally (except when the S60 blew up).

I've never had a motor that had 140-150psi compression, 20" of vacuum at idle, and have it burn so much damn oil. I'm completely baffled. Could not having vacuum on the PCV from the airbox cause massive oil consumption? I've never had this problem before with the same setup. I'll check my hoses tomorrow and see if this turbo is spewing oil.

[MiniMopar]

I've never had a motor that had 140-150psi compression, 20" of vacuum at idle, and have it burn so much damn oil. I'm completely baffled. Could not having vacuum on the PCV from the airbox cause massive oil consumption? I've never had this problem before with the same setup. I'll check my hoses tomorrow and see if this turbo is spewing oil.

No, but I have had stuck PCV valves snort lots of oil into the intake. If this motor has burned oil since the beginning, perhaps there is an issue with the oil control rings or perhaps the bores are egg-shaped at the bottom.

EDIT: to answer your question, I too have had detonation caused by burning oil. A quart in 200 miles is a lot of oil. My CSX has oil control issues in the bores as well, but it has never used more than a quart in 1000 miles and that is with the worn out original turbo.

[jckrieger]

No, but I have had stuck PCV valves snort lots of oil into the intake. If this motor has burned oil since the beginning, perhaps there is an issue with the oil control rings or perhaps the bores are egg-shaped at the bottom.

EDIT: to answer your question, I too have had detonation caused by burning oil. A quart in 200 miles is a lot of oil. My CSX has oil control issues in the bores as well, but it has never used more than a quart in 1000 miles and that is with the worn out original turbo.

I'll check the PCV valve and see what it's doing. I've never replaced a PCV valve, and sometimes when I'm moving heads and vacuum harnesses around, good parts get switched for bad parts. This block... well, I don't remember where this block came from, but it was in pretty good shape and the ring end gap was on the tight side of the service limits. Of course, that doesn't mean the bores are round, but before the piston swap the motor didn't use this much oil. I guess the only way to know for sure is to take the poor motor apart.

I checked the PCV and it seems to be holding, but it might be a little sticky. I also did a cold compression test and the results were 145-150-145-140 with the engine at around 60 degrees F. Some variation could be due to the hand-carving of the combustion chambers in the head, but I'm a little concerned about the 140 cylinder. Also, all 4 BR9ES plugs were relatively carbon fouled, but not oily.

[turbovanman²]

You can still have good compression and have bad oil control rings. Looking at the plugs or piston tops thru the spark plug hole can help determine where the oil is coming from.

[moparzrule]

What were the gaps of the piston rings? Specifically the oil rings.....and also did you stagger the ring gaps?
Oh and one other thing, the center part of the oil ring groove, did you make sure that piece did NOT overlap? It's very easy to overlap that thing, but it's just suppose to come together and touch.

[WickedShelby88]

I've been told to run a different bore size for forged as well.. If your car came with cast like ours then the thermal expansion of the pistons is different I believe a forged piston requires tighter tolerances. This is just off the top of my head without any specs either. Oil will really lean out your mixture and especially throw your O2 off. My 3.0 mini while it runs okay spark knocks if I don't run at least premium. If its using oil though.. Do you have any issues with your dipstick popping out? Matt's right on that oil ring groove. Thats an easy one to goof.

[jckrieger]

I'm pretty sure I installed the rings correctly, as the Wiseco set actually had some pretty darn good directions with the piston set. The gaps were definitely staggered, but I can't remember if I even measured the oil control ring end gap since it was all .std bore stuff. I measured the compression rings to make sure they were in spec, but the oil rings I figured were in spec since the bores and compression rings all checked out.

I actually took the car to the track today and discovered my clutch is junk. I made a pass with a passenger and clicked off a 13.63@105.68 with some clutch slippage and "low" (20-22psi) boost. I then cranked up the boost and ran a 14.00 @ 100mph... with the car at 7,000rpm all the way down the track in all gears.. no clutch. Luckily the car had plenty of clutch to drive home, but those ceramic clutches are garbage. I'm tearing the car down to install a new clutch (if I find something that's 400hp capable) and will inspect the pistons/rings/head closeley at that time. It's now time to go back on those clutch threads...

[Putter]

Good to see you made it home.

I remembered another clutch brand that the vendors don't carry. SPEC has a full lineup of clutches for our cars. Give them a call see if you can't get an engineer on the phone.

[MiniMopar]

It's now time to go back on those clutch threads...

Which clutch are you running now?

[jckrieger]

Which clutch are you running now?

I'm running a Relentless Performance 6 puck ceramic clutch setup that was supposed to be good to 350-400hp. The clutch can't have 10K miles on it, but it definitely can't hold more than 22psi at the track. On the street at higher boost levels, the tires would just start spinning, but with traction the clutch starts "spinning"

[MiniMopar]

It's probably not worn out. It's just at its limit. The marginal clutch in the CSX didn't show up until I hit the track either. After that it was glazed and I could make it slip on the street too.

[jckrieger]

It's probably not worn out. It's just at its limit. The marginal clutch in the CSX didn't show up until I hit the track either. After that it was glazed and I could make it slip on the street too.

I had the same problem when I took the CSX to the track stock. It had an aftermarket T2 oganic clutch and used to chatter on release. At the track I glazed it pretty bad and it started slipping above 10psi. That's when I put in the 6 puck clutch... and first time at the track it failed me. I guess my setup must be making at least a little torque...