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Old 01-25-2007, 09:22 PM   #5
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Member#: 74110
Join Date: Nov 2004
Location: PERRIN Performance

One of the things we discovered with the first build is the engine runs pretty hot. An oil cooler was added this time around to ensure the oil stayed nice and cool, and maybe help keep coolant temps in control. Of course this adds even more oil to each fill, and makes the oil changes about the same a big diesel truck! Like we said, the engine runs hot, hotter than the 4 cylinders by about 5-10C. So next up is a radiator. A Koyo radiator was purchased, and modified with 2 entry points for the H6 engine. We also added the STI thermostat, which is 5degrees C cooler. All this should help control temps for any situation.

WRX fog light used for a vent for the oil cooler.

In making room for the header, we had to find a new place for the filter, and OEM oil cooler/warmer. Why not use a WRX fog light cover and put the heat exchanger behind it.

Another shot of the packaging. We kept the header as close to the engine as we thought was acceptable. This was important as we didn't want to be bouncing the header off speed bumps, and boulders.


So a little more oil, and a little more coolant than the last build, and she is ready fire! Just like the time before, it fired right up. Went through a few heat cycles, and now some quick drives. Not knowing what kind of oil supply this turbo needed, we discovered an extra restrictor beyond the one was needed. In fact so was a second, so three total. We definitely weren't worried about the turbo not getting enough oil J. So, now it was just a matter of time to break the engine in. No plans for another LV trip so it would be a few weeks before it was ready.

First impressions, was it was laggy. Before, we would get full boost by 3100 RPM, and now it seemed much worse. But I wouldn't judge this until the engine was all nice and broken in. So low 8psi of boost was ran, and slowly but surely the RPMS were raised up.


Then the day came that 500 miles were on the odometer. So I decided to do a pull to 7000RPM. First a 6000, then 6500. But I noticed a strange sound. My stomach started hurting, as this sound was rod knock type sound. This was bad! Babying the car back to work the next day, the sound got worse and valve train noise starting happening. This is not good. The engine came out, and was disassembled. Sure enough, rod bearing #2 has a little more clearance than the rest. Say about 50 times more clearance! Thank goodness we paid the engine builder to assemble it, because it would have a warranty, right?? WRONG!!

The builder of course blamed it on oil supply, or improper break-in, not enough oil pressure, too much boost, or knock, but nothing that they did of course. Being a reasonable person, I looked into his suggestions. Boost didn't cause it, knock didn't cause it (have logs), so I looked to oil. Plenty of oil was in the engine and not a bit was ever consumed. Oil pressure, ya right this thing runs 100+psi, and that wasn't' the problem. The argument back was that was way too high, and the added friction from the added pressure could have broken down the oil (due to heat), and caused this. I don't buy this at all, as all JDM STI's have shims to add oil pressure. It basically came down to there were too many things that could have caused it, none of which could be proven it was their fault or mine.


Now that SEMA is approaching quickly, plans started changing. With the H6 broken, the Legacy Spec B and STI Limited coming out, we thought for SEMA we would show off a different side of PERRIN. Something that better represents what we really do. Plus the H6 was there last year, so its old news! The H6 is a great show piece, but it's not like we are building these all day long and selling them. So the focus on the H6 project was turned to a brand new Spec-B Legacy, and Limited STI sitting at the shop. In great contrast to the H6 build, these would be much simpler and much less stressful builds. This sounded good with SEMA quickly approaching. We built the cars to show off what any customer could build using our catalog. They were great hit at SEMA, and it was nice not having to throw together the H6 at the last minute.


Now that we were back at home, H6 was on my mind, and Subiefest was quickly approaching. At this point I am not happy with the bearing failure. I thought I did everything by the book. Starting with the basics of the engine I started checking into things like oil pressure, and oil pump flow. These were important things to figure out for the third time around as we didn't want another failure. I figured I would talk to the builder about the rod bearings and the clearances they had before assembly. Thinking maybe the failed one was tight or loose. Then I find out that the builder couldn't tell me any of the clearances of the bearings! Didn't write them down!! WHAT!!!

Still not happy, and now doubting the engine builder, the engine, and many other things surrounding how well this will hold up. Well another $2000 and it runs again. Long story short, everything went back together just fine, but this time we are going to 1000 miles for the break in at low boost and RPM. I would like to pretend this didn't happen, and it was all a bad dream.

Last time i would be assembling the H6 in 2006. The paint held up ok the 2nd time around. If there was a 3rd time around, i would be throwing this thing through the window of the machine shop.


I would like to pretend this didn't happen, and it was all a bad dream. Subiefest 2006 was the maiden voyage of the freshly re-built, re-honed, re-balance, re-ringed, re-bearinged engine, and it went perfect! It was also the first time the public had seen the new engine, and turbo combo. Besides the few people that walked by casually thinking it was just another STI engine, the car/new engine was a hit! Plus we got to put tons of miles on the engine and lots of great road tuning.

1500 miles and time to put in synthetic oil and take this baby to the dyno!


First pull on the dyno wasn't as good as the first pull done months prior, but we were running less boost. None the less, it made decent power, and at the starting point of 14psi there was tons more on tap! With further tuning at 16psi we realized there was major gains to be had. At this point in the tuning, most of the time was spent getting the fueling close. The timing curves we had from the previous tune was pretty good, and we didn't want to push the limits too far. As we found, this engine would make more power with boost, not timing. The goal with this tuning session is see what kind of "easy" power we have on tap. We were not going to be pushing this engine this time around. Also this is on pump fuel, with water injection using a 50/50 mixture. All runs below are named by the boost seen at peak power. Example: The 16psi run is running 16psi at 6500, and a little more at 4000.


Above graph is 16psi with some fuel and timing tuning. By the change in this graph you would think the engine was running near misfire, but this was running 10.5-1 vs 11.5-1, with a couple degrees in timing change. We were trying to hit 500, but it just wasn't going happen. Time to turn the boost up some more!

Above graph is 18psi. Again that is 18psi at 6500RPM. The large dip in the graph was from the engine running a bit rich on initial spool. Like seen at 14psi, fueling makes a big difference, this dip was .7AFR change. 4psi and we gain 80WHP and 80ft-lbs of torque, this is starting to look good!

Here is the boost curve of theGT4088R on the H6. The only change in the hydra between runs was a simple change in the boost target map. As far as changing boost, the HYDRA is very simple to do. The only thing we battled with is a falling boost curve. The spike at lower RPMs really helps with torque, but if we could only hold it!!

Yes it was called 22psi, but at peak power, it was 21psi. Again 4psi and some great gains! But we are starting to see the gains not so exponential, compared to lower boost levels. This is a sure sign of turbo starting to run out of air flow. More on this later. During the last few runs we started to see the boost curve spiking a little more, but it would still hit the target, 22psi.

Now the 2psi of boost change only netted about 20HP. During the last few runs we started to see running a little lean close to redline. First small amounts of fuel were added, then larger and larger with no changes to AFR. We were SO close! Well that Walbro was good while it lasted! As we once thought before, the fuel pump wouldn't be enough for to much more than the 500WHP, but it at least allowed us to hit 600!
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Last edited by PERRINJeff; 11-01-2013 at 06:38 PM.
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