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Old 10-14-2007, 02:27 PM   #51
flycaster
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...With the increased WGDC (reduced in backwards Subie nomenclature), the more open wastegate would increase the flow into the cylinders per pound of boost...
You've lost me here, unless we're talking reverse logic a la the old HP calculators.

Regardless, I'll be the first to admit that I know nothing about how Hydra works - otoh, I know the OEM ECU actually leans the AFR's as you increase altitude.
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Old 10-14-2007, 02:44 PM   #52
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cool thanks for the good insight, with my hydra my pump gas map stays in Closed loop... In WOT I`am not 100% sure But I think it still should be under closed loop..

Now on my Race-gas map thats a different story, I Run open Loop 100% of the time, you can also see specs of metal in the exhaust port, and also in the exhaust manifold coming out of cylinder 4.

Today I`ll be tearing the Gt35r Turbine Side down to see if I damaged any fins . I`am praying when ever that piece flew off it went out the waste gate
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Old 10-14-2007, 11:44 PM   #53
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Regardless, I'll be the first to admit that I know nothing about how Hydra works - otoh, I know the OEM ECU actually leans the AFR's as you increase altitude.
That's because it moves the ECU into leaner load-sites.

With a MAP sensor setup, until it adapts, with the lower VE, it believes more air enters the engine for a given MAP than actually does, which means too much fuel, which means rich. The inverse occurs with drop in altitude, which means too little fuel, which means lean.

It'd be pretty unusual for an ECU to remain in closed loop even during WOT. You'd need a REALLY accurate wideband and, again, still time for the ECU to adapt. Changes in VE which are adapted via wide-band O2 sensor rarely take place instantaneously because of quick irregularities in the O2 sensor readings during shifts, and abrupt changes in throttle position.

You might also be confusing closed-loop boost control for closed-loop fueling. Just a thought.
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Old 10-15-2007, 01:23 AM   #54
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^ could be.. I`am by no means an Expert.. although, this discussion has given me good information, It probably leaned out and blew... But from what you guys have said, this looked like long term mild detonation right?

Well I just moved to Florida like a month ago, probably drove my car less than 12 times, So this could have been an Issue I had before I moved I assume, Well it is what it is.. I`ll have the short block torn down next week end, I`ll pull apart the turbine side of the turbo, post some pics of that, flow test injectors. and then come to reasonable solution on a next build.

My rods which still should be good are Cosworth H-beam type, Crank I`d imagine is still good and can use, you can see light scratches from the damage, Nothing to major it looks, do you guys think i can just hone the cylinders and be okay?
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Old 10-15-2007, 02:03 AM   #55
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I can't discern what you're talking about (scratch wise), but you'll just have to see once you pull it apart.
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Old 10-15-2007, 08:05 PM   #56
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Originally Posted by STi_Guy04 View Post
How do you guys think about Total Seal Rings? and running like 9.5:1 compression
I have used total seal rings in many different engines...
I have discovered from experience that they don't like three things...

They don't like short rods/piston rock...
And they don't like high rpms...
They don't like high piston temps...

If anyone has used them in our little boxers, I would be curious as to how well they held up...
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Old 10-15-2007, 09:00 PM   #57
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Yeah I think i am going to skip out on those... Pulled apart the turbine side of the turbo today.. everything looks good there, not damage to any of the fins, So that leads me to believe Either this piston has been coming apart little by little, whatever else must have went out the wastegate.. I`am leaning towards the 1st thought though....

I`ll post a pic up for u guys to check out..
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Old 10-15-2007, 09:01 PM   #58
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Originally Posted by shvrdavid View Post
I have used total seal rings in many different engines...
I have discovered from experience that they don't like three things...

They don't like short rods/piston rock...
And they don't like high rpms...
They don't like high piston temps...

If anyone has used them in our little boxers, I would be curious as to how well they held up...
I am using them in my build, I will let everyone how well they holdup (or don't).
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Old 10-15-2007, 09:04 PM   #59
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I`ll post a pic up for u guys to check out..
I want a side picture of the piston when it finally comes out.
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Old 10-17-2007, 10:05 AM   #60
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I have discovered from experience that they don't like three things...

They don't like short rods/piston rock...
And they don't like high rpms...
They don't like high piston temps...
Uh-oh. I'm going to stick a build up in an airplane. I hope to run a sustained rpm of around 4500. What do you, shvrdavid, or what do these engines consider high rpm? I only need 300 chp and am hoping to use an EJ-22T or EJ-257 block. I will also use an aftermarket ECU for aircraft. (I am unable to post the link because this is only my third post. I will post it later if anyone wants to see it).
Thanks!
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Old 10-17-2007, 09:33 PM   #61
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Are you thinking turbocharged or NA (EFI)?

You might want to start a thread on this here in the built motor forum to get some observations from the guys that have built a few of these engines.

Red line for these engines with no modifications is 7000 rpm, peak power about 6200 rpm, and peak torque is 4500-5500. The engine is very happy cruising on the highway at 4000 rpm so I doubt you will have much issue. The older Subaru engines are very popular home built aircraft engines. With upgraded valve gear 8000-8500 rpm is easy to achieve as redline.

Go to the dyno plots in the proven power bragging forum and look around you will get a good over view of power levels and rpm range. Keep in mind those dyno plots are typically at the wheel power level so figure 1.15 to 1.2x that power for at the crankshaft given drive train losses in the WRX.

Larry
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Old 10-17-2007, 10:49 PM   #62
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Thanks, Larry,
I am definitely going to run EFI. I was hoping to go NA, but I don't think I can get the hp in the rpm band that I can use. I am restricted by prop rpm and I want reliablility. 6200 would be the most I want to see, but then I would be around 5500 cruise.
I also want a SOHC to save weight. I've been reading the archives using searches. It is amazing how much there is to read!
I haven't been on the bragging forum much. I will be looking there the next few days.
Thanks again,
Ben
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Old 10-18-2007, 11:59 AM   #63
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Well, I hope everything works out for you and you're back on the road with an even stronger engine soon!
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Old 10-18-2007, 08:41 PM   #64
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Originally Posted by Acroduster View Post
Uh-oh. I'm going to stick a build up in an airplane. I hope to run a sustained rpm of around 4500. What do you, shvrdavid, or what do these engines consider high rpm? I only need 300 chp and am hoping to use an EJ-22T or EJ-257 block. I will also use an aftermarket ECU for aircraft. (I am unable to post the link because this is only my third post. I will post it later if anyone wants to see it).
Thanks!
Ben
4500 rpm should be fine...
Most of my bad experiences with total seal rings have been above 6500 rpm
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Old 11-23-2007, 07:30 PM   #65
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alright so its been a lil while, I took a little break from tearing her down, I got the pistons out and Here is what i found,





this was number four cylinder as the thread and conversation states... All other pistons where fine and looked normal, the cylinder wall was not damaged, Minor light scratches on the side in question, but other than that I think it will be alright with drop in CP`s with over sized rings??

Let me know what you guys think, its for sure a case of detonation, its just puzzling because that type of detonation appears to be long term, and it just burnt that ring land down enough to get to the 2nd ring land and break it!... on the ring itself its burt and black.
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Old 11-24-2007, 01:33 AM   #66
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Never heard of "drop In" pistons unless they're oem
There should be a machining process to the block to match the pistons diameter .
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Old 11-24-2007, 03:20 PM   #67
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ya. I seen people do it before, the block is new and not destroyed, you can actually drop in Oem Sized pistons, and use different rings and get by,
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Old 11-24-2007, 04:03 PM   #68
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...the cylinder wall was not damaged, Minor light scratches on the side in question, but other than that I think it will be alright with drop in CP`s with over sized rings?
Thanks for the photo - it is what I expected. You should go to one-over pistons and have a machine shop hone the cylinders to match the pistons; what you consider to be "minor" scratches most likely are not. Also, there is no such thing as "over-sized" rings - there are rings that are properly fit (gapped), and then there are rings which are not.

Don't wing this stuff. Take it to a good machine shop and get it done right.
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Old 11-24-2007, 07:58 PM   #69
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Thanks for the photo - it is what I expected. You should go to one-over pistons and have a machine shop hone the cylinders to match the pistons; what you consider to be "minor" scratches most likely are not. Also, there is no such thing as "over-sized" rings - there are rings that are properly fit (gapped), and then there are rings which are not.

Don't wing this stuff. Take it to a good machine shop and get it done right.
I hear ya man there is really no short cutting this type of stuff, Its pretty much that I really do not want to Tear down the bottom end, with lack of instructions and help on rebuilding the bottom end, I`am not 100% confident I could build the bottom end right, ya know get the oil clearances right, crank end play, and all the others,

I know the bottom end is assembled right as is, If i tear it down all the way give it to some Machine shop here, Its more risky than I believe, Another thing is I do not know of any machine shops that are used to seeing or have built subaru motors down here in South Florida, Its to costly to send my block to axis or some of the other companies

If anyone has any suggestions let me know, or If yourself have built your own ej25, let me know if it was a hassle, I have built motors before just not one of these, so you can see probably understand why i am a little concerned about splitting the case..

anyhow, thanks for the help and the information! oh but back on the wear on the piston, thats just from detonation over many months right, to burn a top ringland which was forged and coated seems to be a tuning issue, and for some reason number for cylinder always sees its affects.
I plan to send out the injectors to be flow tested, anyone know where and who to contact to do this?
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Old 11-24-2007, 09:19 PM   #70
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...seems to be a tuning issue. I plan to send out the injectors to be flow tested, anyone know where and who to contact to do this?
It could be the tune, a plugged injector, a bad injector seal, or a bad electrical connection. If it were just the tune, I'd expect to see at least a little detonation damage in the other jugs. Do you have any logs from the car before the engine let go - there are guys here who could look it over for you...

As for injector servicing, I know several members who've used Witchhunter and were very happy. They have a web-site.

Best of luck buddy.
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Old 11-24-2007, 09:55 PM   #71
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Hey that just sparked an Idea.... Wow, Never really thought about this but WoW!! KINGPIN those Broke the coil pack Connector on my number 4 cylinder, this as funny as it sounds could this be problem.. It was left Push on and electrical taped on, It seemed to work

This would make sense It ways that at high engine rpm and Power outputs, cause vibrations which in turn could Wobble the connector out and loose connection and Small scales, I`am not 100% sure it caused this issue, but funny it seems like the clues are matching up...

yeah sorry no logs, I Would have but i can never get my hydra and Laptop to be friends with each other, Looks Like i`ll have to buy a laptop from the 90`s so i can make logs

Last edited by STi_Guy04; 11-24-2007 at 10:44 PM.
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Old 11-24-2007, 10:55 PM   #72
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The connection that concerns me is to the injector, telling it to dump fuel in. An intermittent spark connection would just cause misfires, not broken pistons.
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Old 11-25-2007, 07:14 AM   #73
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Broken pistons are almost always due to detonation or overadvanced ignition timing and excess cylinder pressures. My guess is you had a strong detonation event that cracked the ring land then that cylinder lost oil control in the area near the broken ring. The oil that got buy the ring cause long term low intensity detonation which ate up the crown of the piston over time.

Larry
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Old 11-25-2007, 01:35 PM   #74
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Larry, don't you think one of his priorities has to be to determine whether this was a jug specific, or a systemic problem (ie, tune)?
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Old 11-25-2007, 05:27 PM   #75
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Yes given how Subaru engines come apart it is a pretty good bet he has had plenty of opportunity to see if similar things are going on in other cylinders. You should always look at all the cylinders if you have something like this happen. If you see similar early signs in the other cylinders you can be pretty confident that the tune or fuel or boost controller or some other "global" issue is at fault. If all the other cylinders look fine than you have some sort of problem unique to this cylinder.

Larry
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