Okay... some of you may recall (or not) that I posted about lots of smoking from my D15B7 Greddy Turbo setup. I have torn down the engine and STILL don't know what was happening exactly. I'd like to know so I can take care of this.

1) No broken ring lands or burnt pistons
2) Turbo is okay, no leaks
3) Head Gasket was okay as far as I can tell

I have one thought... it looks like there was ALOT of blowby around my pistons. I am a boost noob so maybe my mistake was the way I ventilated, or didn't ventilate in this case, the crank case pressure...

I had an added vent on the valve cover along with the factory vent directed to a catch can. BUT I think I went wrong by blocking off the PCV and thus the black box completely. Now that I've taken the engine out I see what the box is for and how this could be an issue. So, who thinks this was the real root of my problem? I will be running a hose from it to the bottom of my catch can when I put it all back in.

 

You need to be more spec. about the conditions of the engine when it was running: When did you notice the smoke (color, and driving condition that it was worse).
Exp. Acceleration
Deceleration
Downshifts
Cold starts
These are just some examples of what I am getting at. Most of the time if you can isolate when the smoke is the worst, you can think about what is going on in the engine and figure out what is going on. Before you tore it apart did you by chance run a comp. or leak down test?

W/ how you had your catch can I cant see much excessive crank pressure happening if you had an open ventilation catch can.. If it was sealed then thats a different story.

 

I had smoke at all times. If I revved it up the smoke took a few moments to really pour out of there. It was definatly oil smoke, bluish in color and you could smell the oil.

I ran a compression test and it was fine... don't recall exact numbers but it was under 5% variance. I never did a leak down... but I will be replacing all the seals, rings, pistons, etc, etc.

The can was sealed... accidentally. I had an exhaust slash-cut but behind the cat it crimped down to stock exhaust so it actually was creating pressure instead of vacuum. My check valve stayed closed making the can sealed. I tried opening up the can too once I found that out about my slash cut, but still had smoke.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sundownz &raquo;</TD></TR><TR><TD CLASS="quote">

I have one thought... it looks like there was ALOT of blowby around my pistons. .</TD></TR></TABLE>

There you go.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Code &raquo;</TD></TR><TR><TD CLASS="quote">There you go.</TD></TR></TABLE>

Right... but I am trying to figure out why that was. Everything looks okay in there... could it be that my black box was sealed up?

 

I'm guessing this wasn't complete rebuilt w/in the last 10k miles. If not, your first clue to the issue would be: its an old d-series. Commonly neglected, and ovals the sleeves quicker than b-series due to the RS ratio, as well as sludge buildup. I got a d16y8 for free, guy said it wouldn't fire up, but smoke would come out. Sure enough, sleeves were oval like a baby's head.

The service limit for out of round sleeves is .002". Thats roughly half the thickness of the average human hair. If they were more than that, adding boost to the scene probably made it go from bad to terrible.

 

You built up so much pressure in the crankcase that you blew the rings... Yes, that was your problem.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HiProfile &raquo;</TD></TR><TR><TD CLASS="quote">I'm guessing this wasn't complete rebuilt w/in the last 10k miles. If not, your first clue to the issue would be: its an old d-series. Commonly neglected, and ovals the sleeves quicker than b-series due to the RS ratio, as well as sludge buildup. I got a d16y8 for free, guy said it wouldn't fire up, but smoke would come out. Sure enough, sleeves were oval like a baby's head.

The service limit for out of round sleeves is .002". Thats roughly half the thickness of the average human hair. If they were more than that, adding boost to the scene probably made it go from bad to terrible. </TD></TR></TABLE>

Thanks for the help! Although, I am confused about what you mean by "sleeves" in your post. What part are you referring to? Is this the actual block sleeve that the piston sits in? If it is out of round can it be fixed?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nonvtecD &raquo;</TD></TR><TR><TD CLASS="quote">You built up so much pressure in the crankcase that you blew the rings... Yes, that was your problem.</TD></TR></TABLE>

My rings "look" okay... is there any way for me to SEE that they are blown? Perhaps I'm not looking at them correct, as engine building is a pretty new deal for me.

 

Yes, he's talking about the "sleeve" which is the cylinder itself. If they are out of round which lots of high mile D series are then yes you can overbore it but it makes the sleeves thinner everytime. On a D series just get another block and bore it .5 over for true roundness.

You're not going to be able to see that your rings are shot. On my turbo motor that my rings were shot on they don't have strong indications but I am telling you from the symptoms you had your rings were "blown".

BTW, when the crankcase is pressurized it doesnt matter what condition your rings are in the pressure will vent itself and if that means going through the combustion chamber then that is what will happen.

 

It was Chuck Norris, in the Library, with a Roundhouse kick, mystery solved.

 

I'll try to get some tools to measure the sleeves to see if they are out of round. Visually they look okay, but I suppose the difference could be very small. My block is around 120k miles and only ~3k with turbo, FYI.

 

When you rebuild you should always bore over anyway to get a nice tight fit with new pistons. They're definitely at least a little out of round and stop visually checking things because your eyes tell you nothing

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nonvtecD &raquo;</TD></TR><TR><TD CLASS="quote">When you rebuild you should always bore over anyway to get a nice tight fit with new pistons. They're definitely at least a little out of round and stop visually checking things because your eyes tell you nothing </TD></TR></TABLE>

Okay. So if I over-bore by 0.5mm that reflects a diameter change of 0.5mm correct? Meaning that I now would need 75.5mm pistons? Just making sure I am understaning this correctly. I'm going to try to locate a reputable machine shop... anyone know of a good one with reasonable rates in the Charlotte area? What am I looking at for a 0.5mm bore job?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sundownz &raquo;</TD></TR><TR><TD CLASS="quote">Okay. So if I over-bore by 0.5mm that reflects a diameter change of 0.5mm correct? Meaning that I now would need 75.5mm pistons? </TD></TR></TABLE>

Yes. Are you building the B7 because you should just get a D16 block and bore that over to start your build. They're bigger and have more aftermarket support.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nonvtecD &raquo;</TD></TR><TR><TD CLASS="quote">Yes. Are you building the B7 because you should just get a D16 block and bore that over to start your build. They're bigger and have more aftermarket support.</TD></TR></TABLE>

Not worried about aftermarket support since I already have the hard part -- I got the Crower D15B7 rods second hand at a good price so I'm good to go