Compression Test and Leak Down numbers - opinions?

[Wasted Potential]

Do you believe I should just pull the motor and have the heads rebuilt? It does seem most probable the bottom end is fine. Can a shop perform a leak down on the motor directly after heads being rebuilt and installed?

 

As per the side things adding up... an 86 mustang Gt I owned had an exhaust leak after I floated an exhaust valve and installed some aftermarket heads.... so I fixed it, by flipping the headers backwards.... and installing a 70mm turbo haha! I know when those "while I'm at it things" add up QUICK!

 

[MilesA]

I was wondering the same thing. It seems people generally are able to go 200K+ miles before major work is needed for the bottom end. It could be that your heads are just in bad shape and that's much easier and cheaper to deal with.

 

Going with forged parts is tempting, but below 300 hp with VF52 you shouldn't really need them and they do have some downsides. Our pistons are strong, but brittle so they don't deal with detonation well. If your tune is good and you are careful you should be OK.

[Wasted Potential]

Can a machine shop mill the head surface on the block while it's all assembled with only the heads removed?

 

Brittle pistons.... again, reminds me of my hypereutectic ones from my foxbody..

[Max Capacity]

New EJ257, stock fueling, vf52, rebuilt heads, 280AWHP/300ftlbs.

 

That's what I did May 2012. Engine still runs great over 93,000 miles later.

 

it really is that simple.

 

Let the machine shop do what they do best, my buddies shop gave me a complete long block back, it's all in my "click here" link in my sig.

[MilesA]

Can a machine shop mill the head surface on the block while it's all assembled with only the heads removed?

 

Brittle pistons.... again, reminds me of my hypereutectic ones from my foxbody..

 

The crankcase has to meet a flatness spec (found in the factory workshop manual). As do the heads. If the flatness spec is OK, resurfacing is not necessary.

 

Our pistons are hypereutectic ones, too.

[Blink]

Do you believe I should just pull the motor and have the heads rebuilt? It does seem most probable the bottom end is fine. Can a shop perform a leak down on the motor directly after heads being rebuilt and installed?

 

In addition to the heads, you definitely have to check the pistons & rings as a failure in either could be the cause of low compression. Once the heads are off, pulling the pistons to check the rings is an easy added step. Mine were fine and I now have peace of mind that the problem was a faulty valve.

 

You cannot deck an assembled short block; the machining fluid and removed material will contaminate the assembly. Is there a reason to be concerned with the flatness?

 

I'm no expert, but for a Stg. 2/VF52 setup, I don't see any advantage to using forged internals.

[MilesA]

New EJ257, stock fueling, vf52, rebuilt heads, 280AWHP/300ftlbs.

 

That's what I did May 2012. Engine still runs great over 93,000 miles later.

 

it really is that simple.

You really think he needs a brand new shortblock at 120K miles? I guess he will find out.

[Wasted Potential]

I don't think Max Capacity believes I "need" it, and neither do I. However, for that little cost (well, subjectively), that new short block is cheap insurance.

 

In regards to deck surfacing, it is merely another insurance thing, rather do it and not need it than need it and not do it (I know we will find out if I need it when the machine shop has it, but just utilizing the saying).

 

I do majority of all mechanical work on my car, other than rebuilding a differential, transmission, or internal engine wise. If this was a motor i was more familiar with I'd give it a shot, but I do not have the time to learn on it, nor the money to do it twice haha!

 

I agree with Miles that this may all end up being really simple and only needing a valve job, but that's when we get back to the "Might as well" shtoof, that's where the special crank and pistons kinda got me, not a need.

 

I guess what confuses me is that these new 2.5l turbo motors are pretty similar, it seems that only the platform and creature comforts have changed. So, if I someday want the similar era STi, or another wagon, I can just build this one and drop it in if it proves reliable. Wish I had statistics to compare my old 02 audi s6 wagon to this car in terms of performance. I like wagons, I'm a loser haha.

 

I also have issues trusting new places to do engine work as I have a lot of friends in the automotive industry but none with a machine shop or good relationship with any, so I feel they will just tell me it needs a complete overhaul, and then I will get killed with their parts prices and they will make me pay to hold the engine if I wanted to order them in. That makes the short block look better every time.

 

Max Capacity, I saw someone say that attachments, like the water pump (no idea who stated this), but they bolted on differently, and that I may need different headgaskets, or something of the sort. I only looked quick, but I didn't find the part number for an EJ257 short block in heubergers (sp?).

[Wasted Potential]

Two emails received, they are only willing to do the work if they pull the motor and install it in order to rebuild it... I'm sorry, but that's a huge turn off and will not get my business... Not paying an extra 1.5k for a pull and install..

[Max Capacity]

I was more saying, you don't need forged piston for your HP goals.

 

You get a ej257 that Subaru is currently selling and engine gasket set for your year car.

 

Everything bolts together just a ej255. When I got a oil pump, I emailed Mike at http://www.AZPinstalls.com and told him to send me which oil pump he's use on my build.

[Wasted Potential]

Big picture question...

 

How does one justify spending 60+% of a vehicles value into one component of it?

[relative4]

Big picture question...

 

How does one justify spending 60+% of a vehicles value into one component of it?

One word: ZOOM!

[Wasted Potential]

I think it's a curiosity question, my fiancee asked me "this car was suppose to be a get in and drive vehicle." It's interesting to hear how others validate spending 5k on a build for an 6k car. It is like, learning a new perspective, a new way to think.

 

My fiancee is an audiologist, I often wish she could ask all patients (voluntary of course), "what are the biggest regrets in your life?" I would love to hear answers from so many people over 60 plus and what not.

 

Sorry for this huge tangent!

[MilesA]

Economic justification can be an interesting question. I don't consider resale value as a huge factor, more important is how much would it cost to replace this car with a car I would enjoy more. If you are the type of person to hold onto vehicles a long time and maintain them well, you can come out ahead since you don't have to absorb high depreciation, interest, higher insurance and transaction costs that new car buyers do. The trick is picking a car you will enjoy and use for a long time that you can also maintain DIY.

 

If you have a rebuilt engine, it's not unreasonable to expect another 150K-200K miles from your Subaru.

 

Tangents can be fun. The biggest regrets question has actually been studied. Some of the big ones are

- "I didn't do the things I really wanted, I worried too much what other people thought, or worried about failing"

- "I spent too much time working, did not spend enough time with family and friends"

- "I didn't resolve conflicts and kept my feelings suppressed"

 

Back on topic, here is a good picture of a burned valve from a WRX.

[Blink]

Economic justification can be an interesting question. I don't consider resale value as a huge factor, more important is how much would it cost to replace this car with a car I would enjoy more. If you are the type of person to hold onto vehicles a long time and maintain them well, you can come out ahead since you don't have to absorb high depreciation, interest, higher insurance and transaction costs that new car buyers do. The trick is picking a car you will enjoy and use for a long time that you can also maintain DIY.

 

^This.

 

Miles hit the nail on the head for me. Sure, $5k to repair & upgrade is cheaper than buying a new or new used car, but that arguement is only successful for me because I love the LGT wagon and for the $ I’m comfortable spending on my DD, I couldn’t find anything I would rather be driving.

 

Wasted, sounds like you’re running into the same issue with machine shops that my brother did. Recently, he inquired about building a Chevy 350 for an older Corvette. All the shops wanted $5k+ and next to no warranty on the work. Compared that to $3600 for a brand new crate 350 that comes broken in, dyno tested, and warrantied. No contest.

 

That’s why I suggest skipping the decking. The decking itself isn’t much, but the engine short block will have to be torn down and reassembled. Unless you do it yourself, a shop will hit your wallet hard for that.

[covertrussian]

Late to the party, but wanted to add a couple more data points. I did a slightly warm compression test on my car the other week (engine was probably around 100F). 140k miles, 100% Stock with stock tune up to 100k miles, Stage 2 with diy tune since 105k miles.

1 = 135psi, 3 = 132psi, 2 = 125psi, 4 = 130psi

 

I'm at 1,300ft elevation.

 

As for stock tune causing burned valves, all USDM Subaru's have what's called a Closed Loop to Open Loop delay, ECU basically keeps in closed loop fueling while you floor it, causing major leaness. It's not as dangerous on NA Subarus as it is on Turbo one's though, here is why:

http://legacygt.com/forums/attachment.php?attachmentid=258216&stc=1&d=1510676384

 

Redline shows stock tune, I'm at full boost at ~3.3k rpm but my AFR's stay above 13:1 until almost 5k RPM. Normally by 10psi you want your AFR's to be at 11.1:1 on turbo Subarus to reduce detonation. Don't mind the power up tick at the end, that's a virtual dyno anomaly.

 

Notice I said all USDM, JDM versions of the same cars have code and tables for closed loop delay, but the values are zeroed from the factory! Which means this was a US market only fix (probably for emissions).

[MilesA]

Covertrussian, I'm curious when you zero out the open loop delay, how does that effect your fuel economy? Do you notice any changes in driveability?

[covertrussian]

Covertrussian, I'm curious when you zero out the open loop delay, how does that effect your fuel economy? Do you notice any changes in driveability?

 

I've seen WRX guys mention that disabling Open Loop delay killed an MPG or two, but I don't trust people's MPG claims anymore since they are only speculative and full of variables. When I tried to do a low variable same highway test, one day was sunny one day was rainy, which means numbers are not comparable (rain increases friction and requires headlights, thus MPG will always be lower), I didn't bother testing it after. I will say I saw no real difference in the city or highway mpg.

 

I might do a proper low variable test later when I'm SUPER bored because I don't think it will make a difference, with my current setup, cruise control doesn't hit boost even when going up a moderate mountain (from 500ft to 2200ft) at 70mph for me.

 

Drivability changes are all positive, no lean hesitations when going into boost

[solidxsnake]

Covertrussian, I'm curious when you zero out the open loop delay, how does that effect your fuel economy? Do you notice any changes in driveability?

 

It shouldn't change fuel efficiency appreciably, as it's a transient effect (when changing between closed/open loop). Unless you spend all of your driving feathering the throttle such that you're constantly on the border between closed and open-loop fueling, it won't make any difference

 

I agree with covert on the drivability aspect.

[covertrussian]

Though with stock turbo & wastegate tables I was in boost when I would breathe on the cruise control speed increase buttons (actually make the car very jerky to daily drive).

 

I've been on retuned wastegate tables for way too long, so by the time I tried to do closed loop testing, it wouldn't have been the same as a 100% stock car.

[Wasted Potential]

Covertrussian: I am failing to understand that graph, if it were entirely open loop, what necessarily would the difference be? Or what component particular would be different?

 

I thought an AFR of 11 is rich, seems like a relative term, maybe that is lean at high boost?

 

MilesA: would merely grinding the backside/edges of the valves that seat flush, would this be equal to the new valves, or is there a tendency to over weaken the valves doing such?

 

Also, the mentions you give for regrets, I feel when the survey generalized people's remarks it looses a lot of the power of the statement. It's overly personal, but important to me. For example, my father's biggest regret was selling an old historic house (nothing to do with the divorce!).

 

Blink: I can tear it apart, but feel I would not know directly what to look at and replace, and would end up being over my head and just start replacing many things that weren't necessary, (bearings, crank, connecting rods).

 

 

I believe my issue with this, is I have never owned a vehicle for over 2.5 years. So, I always loose money (generally 3-5k per vehicle) as I also keep and make my vehicles be in better condition when I own and sell them rather than when bought... bad idea financially, but makes me feel good while owning and selling lol.

[covertrussian]

Covertrussian: I am failing to understand that graph, if it were entirely open loop, what necessarily would the difference be? Or what component particular would be different?

 

I thought an AFR of 11 is rich, seems like s relative term, maybe that is lean at high boost?

 

12.5:1 AFR is the peak torque range for gasoline. While this range is attainable for NA engines safely, it's too lean for forced induction engines (primarily due to fast flame front and secondary due to heat). Thus all turbo cars that are not meth injected are ran richer 12.0:1 for safety reasons. Usually ~11.8:1 is safe on turbo cars, but not on these cars where a much richer ~11.0:1 is needed to avoid deadly detonation. Keep in mind all properly working stock tunes are actually closer to ~10.5:1 afr after CL delay is off, it's just the stock wideband can't read that low.

 

Some of my theories on why these cars like really rich mixtures are:

• Heat soaked engine bay mounted intercoolers
  
• Poorly flowing log style stock UEL headers which are prone to reversion
  
• People trying to run 18-20psi on tiny turbos, turning them into hot air blowers
  
• Cylinders 3 and 4's exhaust ports are worse flowing then 1 & 2's. 3 & 4 ports have a wall infront of them while 1 & 2 are more gradual, this is due to packaging constraints.
  

 

Thus general consensus on the forum is to not be leaner then 11.1.

 

Blue line is what it should be like with being completely open loop. Btw Open loop means O2 sensor feedback is not control the AFR's. No other car, that I've seen, forces closed loop well into full throttle, by definition they all are supposed to go into open loop during full throttle.

 

 

I believe my issue with this, is I have never owned a vehicle for over 2.5 years. So, I always loose money (generally 3-5k per vehicle) as I also keep and make my vehicles be in better condition when I own and sell them rather than when bought... bad idea financially, but makes me feel good while owning and selling lol.

 

You've bought a wrong car my friend, better cut your losses now before it gets more expensive. I bought my car in 2013 and dropped about $2k in maintenance alone within the first. Timing belt/WP, wheel bearings, brakes, suspension components, all add up. The car has been very reliable since then, but I'm very religious on up keep and oil changes (and oil level checking!)

 

Have you considered leasing cars instead?

[Wasted Potential]

Always get stuck modding cars, makes leasing hard! Plus, 25k miles a year or so would make it astronomically expensive. Ironically, almost bought a audi B5 S4.. I thought I got lucky on this end, seems it was a wash haha.

 

At 80-99% throttle, is there much difference between 100% throttle? Is it just me, but it seems like sometimes at half/three quarter throttle it seems like it runs full out...

 

I appreciate the data you offered up, thank you.

[covertrussian]

It's a drive by wire car, so at 10% pedal it might actually be 50% at throttle body (NA subaru's do something stupid like this to make cars feel more peppy of dealer lots).

 

In my driving anything about 30% is a wash, it's full throttle at that point haha.

 

There are two tables that I can dig up from the tune if your really interested.

[Wasted Potential]

I always appreciate true factual data rather than speculation but do not go out of your way for it if you are busy!

 

Within closed loop, is there anything that creates the particularly roundness to the line? Of course not expecting perfect linearity, but it seems periodic hump pattern.

 

Do you have any opinion on my particular compression pickle? Would you advise a simple stage 1 cobb OTS tune with the sti up pipe I have to help limit damage I do whilst driving? It seems at this condition, the driving it until it pops is as good as any. Money not spent is money accruing interest even if spent a couple months later.

 

Are you aware of corn cobbs stage 1 or 2 AFR curves?