Impreza “Long”

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Joined: January 13th, 2011, 5:38 pm

Impreza “Long”

Post by defibf » February 21st, 2013, 1:51 pm

In 2003 I purchased a nice shiny, new, grey import, specC Impreza, my first ever turbocharged car. Nice enough car but was mapped for Japanese fuel, I had a remap done a week after purchase and the car was transformed. Since then I have replaced the exhaust from the turbo back, welded and ground the exhaust manifold at each joint, and ported the internal wastegate as far as I dare. I replaced the factory airbox with one fabricated from aluminium and replaced the factory air filter with a K&N item, During this time several remaps were carried out, a higher capacity fuel pump was fitted (original pump couldn’t keep up) and slightly cooler plugs were fitted, the result was more power everywhere, the turbo spools from 1800 rpm and is a pleasure to drive.
Sometime in 2007 I decided I wanted more power, I could get more from the original engine, however this would require a larger turbo with a corresponding increase in lag, and to be safe a rebuild as the stock pistons are known for their chocolate like qualities.
So I decided upon a larger engine, after some investigation I ruled out the US spec 2.5 Ltr 4cyl (EJ257), due to its paper thin cylinder walls and propensity for eating head gaskets, I know that there are ways round these problems and that if kept below 450 bhp these engines are pretty safe, however I really don’t see the point in all this work for the available, safe, reliable, power increase.
Sometime during 2007 I had seen that a Subaru specialist in the US was working on fitting a 3.0 Ltr 6cyl (EZ30) normally aspirated engine from the Legacy and Tribeca into the Impreza and adding a turbo.
The beauty of this engine is that it’s only 20mm longer than the 2.0 Ltr 4cyl engine (and around 30% heavier). I found that (at this time) there were two versions of this engine, the first has siamised exhaust ports (my experimentation with my SpecC had showed me how sensitive to exhaust flow turbocharged engines were) I didn’t like the idea of that, the second version arrived in 2006 with variable lift and timing on the intake cam and individual exhaust ports. After months of emails and phone calls I tracked down an EZ30R from a 2007 Legacy which had been removed from a crash test car. I imported it in October 2009, on stripping down, I found that as expected the engine had just about zero miles on it, not really an issue either way as most moving parts were due for replacement, but nice all the same
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I already had a plan as to which parts to source from where. I found that a machine shop I use had some parts in stock (presumably obtained for someone who had the same idea as me but gave up), so pistons, valves, and valve gear were quickly obtained, I had started working on the heads, the intake ports look pretty good, I made silicone moulds to check cross sectional area, the exhaust ports looked terrible with large intrusions and dog legged ports (all Subaru’s have dog leg ports, however one on each of these heads are particularly bad). The large intrusion in the exhaust ports is directly beneath the spring seat, clearly due the compactness of this engine a compromise has resulted in a less than perfect arrangement.
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Intake 01
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Intake 02
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After a couple of abortive attempts at making a tool which would allow me to measure the thickness of the material which I wanted to remove, I decided that I should obtain an ultrasonic thickness tester, having been frightened by the price of these I decided to take a chance on a lower cost option from China, I had been in conversation with some people on a Canadian forum (American V8 related) regarding these Chinese sourced meters, and “went for it”. The meter arrived after a few weeks and has proved to be accurate and reliable, single point calibration so I made a number of test pieces to check consistency.
Around this time (early 2010) a close family member fell ill, a situation which has only just been resolved (positively thanks to Kings College Hospital), for this reason very little has been done on the engine between then and now. I have just about finished the heads, I found that the casting thickness varied considerably, I wanted a minimum thickness of 4mm, in order to remove the intrusions I went slightly below this in a couple of places. The block has been machined for the new pistons. I have trial fitted the pistons to check deck height, prior to ordering custom Carrillo con rods, Still got to check and set valve clearances machine crank for increased bearing clearance, obtain new (harder) big end bearings, new mains, clutch, injectors (Bosch),and turbo’s.
The variable lift mechanism is known to require a fair amount of oil flow, the oil galleries to and from the existing oil filter, narrow from 16mm to around 10mm, therefore I am going to machine the existing oil galleries and add an extra oil filter (with its own thermostatic air cooled oil cooler) to run in parallel with the existing filter whilst keeping the modine oil cooler for quicker warm up.
It is well known that these engines can run on the hot side so I will be removing the nasty pressed steel impellor from the water pump and replacing it with a nice cast item I saved from a VW Crafter I repaired, as luck would have it (not really luck I have measured a lot of impellors), it’s very close in size and a little machining will see it fit nicely. I am hoping that this together with the additional air/oil oil cooler will prevent the hot running issues that others have seen with these engines.
I am going to run twin turbos Garrett GTX2860R I am in two minds on whether to use internal or external waste gates, it’s not going to be anywhere near a “max effort” job so currently swayed towards internal as these would not be too restrictive (at this level) and a lot easier on the exhaust fabrication.
I will be making my own manifolds, I have modified several in the past and can weld to a reasonable standard with a tig. This will be my biggest challenge (to get it right), the wiring will be ok I have half made the engine loom and am in the process of obtaining some connectors to connect into the existing chassis loom, and then onto the aftermarket ecu (which has been sitting in its box for more than a year). Updates soon time and funds allowing

Guy Croft
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Re: Impreza “Long”

Post by Guy Croft » February 23rd, 2013, 10:59 am

A post that I read with interest, thanks!

Guy Croft, owner

Posts: 2
Joined: January 13th, 2011, 5:38 pm

Re: Impreza “Long”

Post by defibf » February 24th, 2013, 12:03 pm

Thank you
I re-read after posting and though the post slightly rambling and disjointed, I will try to fill in some of the gaps and make it more coherent. Hopefully sometime this week i have time to take some pictures of later port moulds, I find that for me it is much easier to "see" what’s going on with a mould, I also like the option to slice into 1cm sections to check csa. I know that some people seem able to look at a port and see whether it is right or not, for me it’s much easier (and more successful) to use port moulds

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