Machine shops & STI engine rebuild...

[Dean]

Damn. An AC hard line cracked while moving it out of the way...

Guess it is time to eliminate it, but how do I make a good seal to the grill without the AC core?

[sperry]

Originally Posted by Dean

Damn. An AC hard line cracked while moving it out of the way...

Guess it is time to eliminate it, but how do I make a good seal to the grill without the AC core?

Slap an A/C core sized oil cooler in there.

[Dean]

Originally Posted by sperry

Slap an A/C core sized oil cooler in there.

Is that what you did? That sounds like a huge oil cooler... And I'm not sure it is a good idea to put a huge 200+ degree oil cooler in front of most of a 150+ degree radiator, or am I confused?

[sperry]

Originally Posted by Dean

Is that what you did? That sounds like a huge oil cooler... And I'm not sure it is a good idea to put a huge 200+ degree oil cooler in front of most of a 150+ degree radiator, or am I confused?

I was being sarcastic. However, my new oil cooler is massive and does cover probably 30-40% of the radiator, but then again I've got a Koyo radiator, so I expect with decent oil cooling the larger rad will be able to handle the water temps even with a 200-some-odd degree oil cooler and intercooler in the way.

As far as sealing it... I've got some sheet aluminum and some snips. I was planning on tracing out the necessary shapes and cutting myself some panels to rivet between the bodywork and radiator... then use some metal tape and weather stripping to help seal it all up. I just haven't gotten around to the work since it's going to be tedious and probably cut the crap out of my hands.

[Dean]

Holy crap! Oil is everywhere. The intercooler, hoses, compressor and I don't even have it out of the car yet... not to mention to the rest of the engine bay even though it was cleaned once.

A/O separator is now a must! I am debating if I can accept a return line to the intake or not.

Only marginally related, I am also thinking about BOVs. recirc. or atmo.? The argument in favor of recirc is that it is already measured air thus should return post MAF. I have been thinking about that.

WHO CARES if it was measured. The circumstances have changed since it was measured, or else it wouldn't need to be blown off!

I would think returning it also causes turbulence if not back pressure in the intake. Does the MAF subtract air blown backwards through it? I think not, if it is just a hot wire being cooled by airflow. And why blow intercooled but still hotter than outside air back into the intake?

I am thinking I'll be a ricer and use that Forge motorsports VTA BOV I have lying around.


And had a thought on getting air to the radiator. The AC core is a mess from rock hits. Was thinking I could cut the core out of the frame and then put a screen on it... protecting the radiator and providing a path without fabbing sheet metal.

[cody]

As I understand it, the issues with moving to a fully atmospheric BOV (running rich between shifts)cannot be 100% tuned around. Def. let us know what you learn on the subject though. The opposition to BOV's could just be a relic of early tuning experiences, much like the fear of MBC's.

[Dean]

Originally Posted by cody

As I understand it, the issues with moving to a fully atmospheric BOV (running rich between shifts)cannot be 100% tuned around. Def. let us know what you learn on the subject though. The opposition to BOV's could just be a relic of early tuning experiences, much like the fear of MBC's.

I understand the theory of why it would be rich between shifts, but only if it falls all the way to idle. All the way down to idle, fuel and likely spark should not even be present if the ECU is doing it's job. And time passes, so why would the ECU even take into consideration air that flowed over the MAF a second or so before?

[sperry]

Originally Posted by Dean

I understand the theory of why it would be rich between shifts, but only if it falls all the way to idle. All the way down to idle, fuel and likely spark should not even be present if the ECU is doing it's job. And time passes, so why would the ECU even take into consideration air that flowed over the MAF a second or so before?

IIRC, the car doesn't run rich when the throttle is closed w/ a VTA BOV. It's when the throttle is opened back up after a quick shift that there is less air in the intake track than predicted by the MAF.

Remember that the MAF is pretty far upstream, so the ECU is basically using the current MAF data under the assumption that what it's reading now is similar to the air the motor is actually combusting, when in actuality the MAF data represents the air the motor will combust several combustion events later. So if there's a sudden change in the air pressure in the manifold, the MAF data will not correctly represent the intake charge you're calculating fuel for.

Because of this, it's plain-old impossible to tune around the rich condition of a VTA BOV on a MAF based load table. Sure you could attempt to use the TPS to detect the closed throttle, and then attempt to adjust fueling properly for the VTA when the throttle opens back up after the shift by guessing how much pressure was blown off, but a) you risk running lean if you back out too much fuel with your "guess" about how much pressure blew off and b) I don't believe the stock ECU has a table for this sort of correction, which means you can't just tune the ECU, you have to reprogram it with new logic.

All this of course is a non-issue w/ a MAP based ECU because that does in fact read the current manifold pressure and the intake temp, so the ECU can properly react to a VTA BOV. But the MAF based OEM ECU isn't ever really going to be able to totally compensate for a loss of metered air. It's just a ton easier to route that air back into the intake making the MAF data more accurate. Plus, why waste compressed air you already spent exhaust energy on compressing?

[cody]

http://forums.nasioc.com/forums/show...blow+off+valve

http://forums.nasioc.com/forums/show...ov+rich+theory

Lots of crap to wade through, especially in the 2nd one, but some good tidbits do exhist in there.

[Dean]

For $159 bucks, I could switch to a MAP based system. $50 Cobb adapter and zeitronix 3.5 BAR MAP sensor. Hmmm... Wonder if Mike, Paul or Ed have any experience tuning via MAP? If there were a Stage 2 MAP map, I could start there.

[cody]

I know Ed tunes a lot of blow through MAF setups. I assume that's different though?

http://www.seccs.org/forums/showthre...hlight=results

[Dean]

MAP <> MAF. Pressure vs. Flow.

[Dean]

Anybody want to help tear down the '07 long block today? It is kind of interesting if you have never seen or done anything like that.

I can do it myself, but occasionally need somebody to hold the stand steady while I use a breaker bar on the head bolts, pulleys, etc...

Water and gloves provided. I might have some aged beer around somewhere.

Starting after Rolex is over. About 1:30ish

[Dean]

Damn Cam Pulley bolts!!!

Edit:

Got them. Breaker bar, pipe, old belt and 2 vice grips FTMFW!

Leverage is your friend!

Only slightly mangled one which I will replace. Easier when you have 2 people and by myself, I got a little angle on one before realizing it.

Heads and pistons will have to wait until tomorrow. Too cold and getting dark out there.

[Dean]

How you get zero compression in a cylinder...

See the nice compressed aluminum stuck to the rim of the cylinder sleeve where it got mashed against the head?

Surprisingly enough, heads are likely fine. that sleeve or the whole block may be done.

I am definitely going to flow test or swap injectors before rebuilding either block.

[cody]

Jeez, that looks all sorts of wrong.

[ScottyS]

Yummy.

[sperry]

Originally Posted by Dean

How you get zero compression in a cylinder...

See the nice compressed aluminum stuck to the rim where it got mashed against the head?

Surprisingly enough, heads are likely fine. that sleeve or the whole block may be done.

I am definitely going to flow test or swap injectors before rebuilding either block.

Ouch!

I remember a similar picture of the piston in my 1st EJ257 that let go on S-Squared's dyno (I think Aaron took it w/ his cell phone). Mine was probably caused by a lack of fuel due to the missing Walbro that wasn't installed (800cc injectors are pretty worthless with a stock WRX fuel pump trying to supply them). Are you leaning towards a bad injector at this point?

That makes me consider pulling my 800cc injectors and sending them out for testing, or maybe just going back to the 675's I've got. Or perhaps just getting something in an 800cc size other than the super laggy PE800's I've got that are impossible to tune for in the Hyrda (the lag in the PE800's is larger than the largest number you can put in the latency table, meaning you have to set the latency 20% shorter, then modify the fuel table).

[Dean]

Looking more closely, it looks like the cylinder may be salvageable. What you see in the picture appears to be aluminum build up on the cylinder wall, not wear. it might need a 99.75 overbore, but probably not all the way to 100.

This failure does mean I have to finish the tear down on this block, not just leave it as a shortty and swap pistons.

I have no justification for blaming injectors, but figure it does not make any sense to rebuild without checking them. 100K miles on a set of injectors probably is enough to justify a flow and pattern test. I am just as likely to replace or upgrade them though.

The more I look and research, the more convinced I am to use a gapless top ring set when I do rebuild. It should reduce blow by and equalize pressure and heat on the second ring land. if you notice in the piston failure picture, the piston failed at the top ring gap. It is highly likely that the failure was in ring land 2 and then it just progressed up and down until it blew the hole in the piston.

Not sure I mentioned it, but a section of one of the '04s piston's 2nd ring land fell out while the piston guys were inspecting them. I don't recall for sure, but believe that may have been in the gap area as well. Apparently failure in ring land 2 is the most common failure on these pistons/engines.

Back to the original topic of this thread. Not sure when, but I will definitely need a machine shop. Still looking for recommendations.

[Dean]

Interesting update.

The piston on the '04 block that had the piece of the 2nd land fall out during inspection was also from cylinder #2. That absolutely reinforces my urge to get the injectors and maybe the rails tested further.

Maybe I should just swap to the '07 TGVs and fuel rails. I'd need to see the '07 injector maps to compare to the '04s...

There was also some slight lateral loading on one of the '04 rods which may mean it was slightly bent. Not cylinder 2 though... Slightly weird, but then again, 100K miles. Even something on the edge of tolerance might start a bit of wear. The rest of the '04 bearings and crank and even sleeves look pretty damn good cleaned up. we will see how much wear they actually got when I get it measured and/or rebuilt.

And my theory about load in the gap area was bogus. The rings actually rotate in their groves at double digit RPMs so it does not load or heat a specific area. Who knew???

[cody]

Crazy. Where'd you learn that?

[Dean]

Originally Posted by cody

Crazy. Where'd you learn that?

About the rings rotating? The piston guys mentioned it. Between the cross hatching and piston loading/wobbling, the forces on the rings which are basically just springs cause them to spin slowly. Something in the neighborhood of 1/1000th of engine RPM.

2 strokes have to be pinned to keep the gaps from hitting the ports.

[cody]

Interesting.

[Kevin M]

Does anybody have a reasonably accurate cost estimate for a basic OEM-style shortblock rebuild? Factory bearings and boring and all that.

[sperry]

Originally Posted by Kevin M

Does anybody have a reasonably accurate cost estimate for a basic OEM-style shortblock rebuild? Factory bearings and boring and all that.

~$300 if you bring them the SB already stripped down, IIRC.