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Old 05-18-2009, 03:15 PM   #301
WrXtaCy2003
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I was not trying to make an apples to apples comparison. Nor was I saying, "well the evo can do it so can we". I clearly stated the major differences. I was just saying, cross drilled crankshafts are proven, without a doubt, to work in high rpm builds. Thats all.

DK
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Old 05-18-2009, 04:25 PM   #302
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Quote:
Originally Posted by WrXtaCy2003 View Post
I was not trying to make an apples to apples comparison. Nor was I saying, "well the evo can do it so can we". I clearly stated the major differences. I was just saying, cross drilled crankshafts are proven, without a doubt, to work in high rpm builds. Thats all.

DK
don't get me wrong...I did not mean to imply that you wrong in anyway. I was just trying to further explain why the differences are made...in simple terms.

Honda's are similar to evo's though usually with even shorter rod ratios. They have small light pistons and wider rod journals. Piston force and oil wedge area are the big killers for us.
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Old 05-18-2009, 04:39 PM   #303
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yea. I couldn't believe it when I first saw my friends ROD bearings, are wider than our widest main. i was just like, give me some of that. LOL

Well I can't wait until I try my straight shot 2.5 crank in my build this summer.

DK
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Old 05-18-2009, 06:01 PM   #304
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I can't wait until I can test a new 48mm journal setup with .030" wider bearing
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Old 05-18-2009, 06:26 PM   #305
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now all we need is a combination of yours and mine! and we'll be up in the F1 range.....

DK
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Old 05-19-2009, 07:07 PM   #306
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I already have straight shot available...I was working on a 'V' shot but am contemplating the feasibility of actually producing them in an affordable manor.

Regardless, it should all be interesting to see the 'new' things happening in the subie community
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Old 05-20-2009, 11:09 PM   #307
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Micah is this a new crank designed and manufacturered by you, or a stock crank modified by you?
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Old 05-21-2009, 12:21 AM   #308
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straight shot is used by BC and K1...the 'v' would have been manufactured based upon my design but finding 4340 at a decent cost is ridiculous being I'm not buying direct from china or egypt...the material cost for one crank would be right at $1k...so not a profitable crank or cost worthy venture when others get enough job done for about $500 over just my material cost.
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Old 05-21-2009, 06:30 PM   #309
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Quote:
Originally Posted by Homemade WRX View Post
I can't wait until I can test a new 48mm journal setup with .030" wider bearing
HAHA Go ahead and go back in time with your project. 48mm was a design of the past bro. Why do you think today's engines are not using them? Spun bearings!
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Old 05-23-2009, 06:19 PM   #310
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HAHA Go ahead and go back in time with your project. 48mm was a design of the past bro. Why do you think today's engines are not using them? Spun bearings!
you do know that only one subaru engine ran 48mm (phase 1 EJ25) and it also had a NARROWER bearing than our current 52mm bearings. So now take a 48mm with a bearing that is 0.030" wider than our current 52mm bearings.

Heck, why do you think domestic guys are dropping down to 48mm journals on their high rpm and stroker builds

Its not the past but possibly a future option.
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Old 05-27-2009, 01:32 AM   #311
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You would really have something if you could move the decimal point over to the right one place on the width. Thats the one I'm saving up for. That and a sequential shifter.
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Old 05-27-2009, 07:19 AM   #312
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Please make easy for the beginners... Should you buy straight drilled(shot)
or Cross drilled? Which is the better option?
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Old 05-27-2009, 11:16 AM   #313
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You would really have something if you could move the decimal point over to the right one place on the width. Thats the one I'm saving up for. That and a sequential shifter.
yeah, if we could fit .3" we'd have massive overkill but I don't think rod bearings would be an issue any longer.
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Old 05-27-2009, 02:21 PM   #314
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Originally Posted by acssa View Post
Please make easy for the beginners... Should you buy straight drilled(shot)
or Cross drilled? Which is the better option?
We have a tendency to over-complicate things here. Stick with the stock stuff and you'll be fine . I was looking at this kind of modification for 10k+ rpm.
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Old 05-27-2009, 06:34 PM   #315
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imho and ime the vast majority of bottom end failures are VERY likely due to detonation.. det that puts shock loads on the bearings at LEAST 10x higher than they see in normal service.
I am not in with this! I've tore appart several engines with completely ruined pistons due to detonation (even forged pistons), but none of them had big-end bearings which were damaged. On the other hand, I've seen quite a few 2.5 engines with damaged big-end bearings were was absolutely no sign of detonation. We all know those pistons are made off glass, so if it had detonated few times the ring lands would have been broken.

It's an oiling problem and in the 2.0 WRX's the poor bearing quality doesn't help either.
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Old 05-27-2009, 11:08 PM   #316
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I finally lost a bearing in my 2.0 L WRX a while back. It is an oiling issue I am sure of that. I was auto tuning a new Autronic ECU and in order to get a load cell at 6000 - 6500 rpm I was running at essentially zero load in second gear on flat ground holding the rpm's up there long enough for the ECU to dial in each load cell. Total time hung at high rpm about 48 seconds per my re-enactment in my other car. No G loads flat ground almost no throttle.

I personally am convinced that the stock oil system does not have enough oil pan capacity to support sustained high rpm unless one of two things are happening. The engine is periodically "breathed" like you do on shifts to give a moment for the oil to drain down out of the heads, or the car is involved in moderate G turns so that the G forces help pump oil down out of the heads, and throw oil down into the pan from the head that is experiencing negative G loads. We know sustained high rpm in high G turns like when doing donuts kills the bearings as a few folks have nuked a rod bearing doing that.

I suspect we are sucking the pan nearly dry and pulling a slug of air, and the most vulnerable bearings are the ones off Main #3 that is trying to feed two rods. If one of them gets too much air in the oil it kills the bearing. The stock rod bearing clearances are also too tight in my opinion for sustained high rpm.

I have been without work for 6 months now, so I have not cracked the engine to get pictures of it as I cannot afford to put it back together, but it definitely lost a rod bearing.

After that brief 48 second period at high rpm when I lifted throttle there was a very very faint rattle. It was so subtle I was not even sure I actually heard anything. I took the car home and by the time I had driven the 3 miles to the house it had a very real rod knock. This also explains why folks say "gee I was not doing any thing when the rod went out". That is probably true, because they actually killed the bearing a few miles earlier. It just took a while for it to degrade enough to be noticeable for someone who was not listening for that noise or was not very experienced with engines so that subtle sound on throttle lift was not even noticed.

I called a local crank grinder and he off the top of his head told me which rods to expect to see damaged. He also believes the pattern of failure he sees on the subaru cranks indicates oiling issues with mostly those center 2 cylinders.

That said as hard as I have beat on this engine I have no complaints.

Larry
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Old 05-27-2009, 11:32 PM   #317
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Sorry to hear about your bad luck Larry, hope things get better soon. Hope your new job will be better than the last one. How many miles were on your motor and how much pressure were you getting at 6k?
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Old 05-28-2009, 12:59 AM   #318
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I only had about 78,000 on the engine if I recall correctly, but I beat it really hard trying to set the local high altitude record on the TD04, including running a 7800 rpm rev limit for a while. Plus over 100 drag strip passes including flat shifting. I was currently running a extrude honed 16G, and hitting 20 psi at 6000 ft altitude which was pressure ratio wise comparable to about 26 psi at sea level as far as the turbo was concerned. Not to mention all the experimentation.

Timing was bad personally, but the engine served me well considering everything I threw at it.

Larry
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Old 06-17-2009, 09:06 AM   #319
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Hotrod - What oil pan were you using? The STI or the WRX pan?
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Old 06-17-2009, 12:23 PM   #320
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One problem on my car with oil loss has been through the crankcase breather. It sucks the oil out with engine vaccuum. I ran through the mountains for a long trip a few weeks ago and my oil disappeared by the time I got back home. Normal driving has never done that. I was hard on it for consecutive days and the oil vanished. There is no smoke, leaks, or compression loss, either. Big turbo motors do the same thing with a vent attached in front of the turbo.

BTW, any guesses what the vacuum measurement is in front of a turbo?
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Old 06-17-2009, 12:26 PM   #321
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More important than vacuum is probably the delta P of the crankcase to inlet.
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Old 06-17-2009, 12:48 PM   #322
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Quote:
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BTW, any guesses what the vacuum measurement is in front of a turbo?
Ideally it would be zero (atmospheric pressure). The smaller the pressure drop at the turbo inlet, the lower your Pr for a given level of boost, and the more power you'll make (turbo is more efficient = lower temps).
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Old 06-17-2009, 04:01 PM   #323
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Ideally it would be zero (atmospheric pressure). The smaller the pressure drop at the turbo inlet, the lower your Pr for a given level of boost, and the more power you'll make (turbo is more efficient = lower temps).
Since we're not dealing with an ideal, are you saying smaller turbos have a greater pressure drop in front of the turbo when pushed harder?
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Old 06-17-2009, 04:20 PM   #324
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Since we're not dealing with an ideal, are you saying smaller turbos have a greater pressure drop in front of the turbo when pushed harder?
Well yes that's true, but that's not what I was saying.

When you are going to pick a turbo, you decide on a level of boost, and determine the pressure ratio that corresponds to (Patm + Pgauge)/Pinlet. You use your engine's VE, boost, RPM, etc to figure out the volume of air the engine is drawing at that level of boost, and then you go to the turbo's compressor map to see what its efficiency is at that pressure ratio and flow rate. Higher efficiency means less heat, lower efficiency means more heat. The more heat you have in the charge, the less air is actually there (IE: 15 psi at 70 deg might be 300g/s, but 15 psi at 120 deg might only be 200g/s. Same pressure, but less air, same reason why larger turbos make more power at the same level of boost...they're more efficient, heat the air less, and are actually delivering more air).

Now when you're looking at the pressure ratio for the turbo, Pinlet plays a big part, this is going to be Patm - Ploss. The Ploss term is the amount of pressure you lose through the intake tract, the higher the air flow rate the higher this will be, and the longer and more restrictive your intake is the higher this will be. The more loss you have, the lower your absolute pressure will be at the turbo inlet, and the higher the pressure ratio required to achieve the same level of boost. Higher pressure ratio usually means lower efficiency, which means less power. For example, say you just had a filter stuck directly on the turbo inlet, with say .05 psi pressure drop. If your atmospheric pressure was 14.7 psi and you were running 20 psig, your pressure ratio would be (14.7 + 20)/(14.7-.05)=2.37. Now say you had a corrogated rubber inlet that was 5 feet long and had a 2 psi pressure drop. In the same situation, your pressure ratio would be (14.7 + 20)/(14.7-2)=2.73. That restrictive inlet just increased the pressure ratio required to run 20 psi from 2.37 to 2.73. Take your typical 20g turbo at 500g/s, you just dropped your compressor efficiency from 77% to 74% and probably lost about 10-15whp.

Now your question was what is a typical value for Ploss, the pressure you lose through the intake tract. Well this is completely dependent on how much air you're sucking through the inlet, its diameter, if you've swapped out your stock turbo inlet for an aftermarket one, what intake and filter you're using, etc. For example, on my rotated kit, my intake is about 18" long, 3" diameter with one slight smooth bend and a big filter on the end. I'm probably only losing a tenth of a psi in my intake, maybe a hair more, but not too bad. Now with the stock setup that has the corrogated turbo inlet, then the corrogated intake with the big panel filter, the silencer in the fender, and the "cold air" scoop by the radiator, you're probably looking at a 2-3 psi drop at stage 2 levels of boost.
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Old 06-17-2009, 05:27 PM   #325
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Since we're not dealing with an ideal, are you saying smaller turbos have a greater pressure drop in front of the turbo when pushed harder?
The physical size would have little to do with it if anything at all...it would all be based upon flowrate and restrictions before and after the turbo.

Regardless this is ALL way off topic.
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