I reach the top of a long hill the road opens up ahead of me... Miles and
miles of dry black tarmac with perfect visibility, and not one other car on
the road as far as the horizon... The speed is fifty five miles an hour and
the car hums along quietly in 5th gear...
This is going to be a long boring drive.
Or is it? Clutch down, blip the throttle, the RPMs instantly leap up to 4500. A quick flick of the wrist has me in 3rd gear. The gas pedal comes down, the car begins to move. First, a whine, like a jet engine, but higher pitched and more subtle. Then, the whine gives rise to the sound of rushing air and a glance at the boost gauge tells me what I already know: 20 pounds per square inch of turbocharged, intercooled air are being forced into the engine, over 500 cubic feet of them a minute. But I don't need a boost gauge to know that: The acceleration is brutal! 3rd gear goes by in seconds as the car leaps forward, the speedometer climbing almost as fast as the rpm gauge. Clutch down, 4rth gear, 90 miles an hour, the gas pedal comes down again; the tach now reads 5500RPM; boost buildup is instant; the car does not hesitate; it pulls so hard there is no time to reconsider the decision... Soon we are going 130 miles an hour, 8000RPMs in 4rth gear... Should I? The road continues straight, the car is rock solid, and the sound of air rushing by and the engine screaming eggs me on... Why not? Nothing can catch me now.
5th gear... The brutal acceleration gives way to a more gentle push on the back... 140, 150, 160... Now it is getting really loud inside the car...
170MPH (273KM/H)... The engine is now spinning at 7600RPMs. The white dashed lines on the road give way to a solid line, this one not as bright as the stripes that form it themselves. The scenery goes by in a blur as the scream of the engine blends in with the sound of tires rolling over the pavement and air going by at almost 3 miles a minute. But still, the car is rock solid, and still accelerating, albeit at a much slower rate now. I come off the gas, and realize in braking that when you are going that fast, it takes an incredibly long distance to stop the car. I've just covered miles of road in a few minutes. The fuel gauge is a hair lower.
WOW! This is fast... This is really really fast!*
Welcome to the 3rd iteration of my car page. As I work towards my
goal of having one car that will do everything: drive me to school on a
daily basis, get decent gas mileage on an inter state trip, and also be
equally at home at a race track, an autocross, an ice race or a rallycross,
I have come to the following realization:
My older car modification
*None of the events depicted above ever happened ;)
The new block.
I approach engineering from the perspective that, if something failed,
then it obviously wasn't strong enough and should be modified or built up to
withstand the level of abuse that caused the original failure in the first
place. It is no secret that I abuse my vehicle; I drive it for all its worth
and then some, and if the old motor couldn't stand it, then a re honed version
of it probably wasn't going to cut it either. Since I don't see my driving
habits changing any time soon, changing the car to accept them was the
What I really wanted would be to build up a race motor off the EJ257 (USDM STI, 2.5Litre) engine block with forged internals. The larger displacement interested me because it would give me more low end torque and off-boost power, which makes any car that much more enjoyable to drive in the street. Unfortunately this would be well beyond my student budget, and it also would be something my stock ECU would be incapable of running, so I would need a stand alone ECU to run the motor, along with a new transmission, rear differential, and half shafts to support the power, and it would have to be tuned at a dyno, at the cost of $150 an hour.
The next best thing was to obtain a lightly used (under 30K miles) EJ207 (JDM STI Version 8) shotblock. This is the 2 liter engine that comes standard on 2004 - 05 Japanese STIs. It is a semi closed block and has a blueprinted, lightened rotating assembly, and all the internals are a lot better that my previous Version 5. It also has extra oiling holes drilled in the crank and is rumored to be capable of spinning to almost 9thousand RPMs.
The engine was re-assembled with ARP head studs (the best in the market) and
a new JDM STI gasket set. I considered using aftermarket head gaskets (Cometic
makes very good ones) but several experienced engine builders (such as Quirt
Crawford, who makes some of the most powerful STI engines around today, such
as a 720AWHP engine used for drag racing) talked me out of it. Apparently
the stock STI head gasket is a 3 layer stainless steel gasket and will more
than adequately hold all the power this engine can make. Also, using after
market head gaskets that are not the exact thickness of the stock gasket
will alter the combustion chamber "squish" area and also throw off the cam
timing; both bad things. The ARP head studs will provide enough clamping
force to essentially ensure that the gasket doesn't blow at any boost level
I intend on running.
2- The pistons are a completely different design; the domed crown with valve reliefs cut into it should improve combustion chamber turbulence which in turn should reduce the likelihood of detonation. They are also made by a different method; since Version 8 Subaru has employed Hypereutectic cast pistons on all their engines. HyperCast pistons hold much tighter tolerances and are stronger than cast, but they are also brittle due to the extremely high levels of silicon on them. This block should be capable of making over 500HP at the crank, but unlike a forged piston block, it will not tolerate much detonation.
I obtained this engine from FineLineImports, the supplier of my previous engine (under acknowledgements).
Thanks to Subaru's virtually complete interchangeability between
various model years within the Impreza lineup I can use my JDM WRX Version
5 Type RA heads on my new STI Version 8 short block. There are a few
better heads out there (for instance, it would be very desirable to have a
set of Version7 heads with AVCS (electronic valve timing control), but
these are amongst the better ones to have; aggressive cams, large valve
ports (much larger than USDM WRX for example) and a red line of 8000RPM
stock. Unfortunately the large leakage numbers meant that the heads had to
be redone. I had the heads resurfaced, the valves reseated and a 3 angle
valve job done. They should be better than new now. It is interesting to
note that these heads have a chamber volume of 50ccs, whereas the STI
heads are 51cc. This will bring my compression ratio up to 9:1, which will
provide more off boost power and better spool. The higher compression
will, however, limit the maximum boost for any given fuel octane level.
So, how much power does this all make? If I had to guess I would say:
"No more than 140HP at the crank". This is a dedicated turbo
engine and as such, it has relatively low compression (9:1, which is
actually pretty high for a turbo engine, but still not very high for anything
naturally aspirated). The low compression, plus the 2litre displacement
makes for relatively little power off boost.
Porting and Polishing:
Minimizing lag requires looking at the engine as a whole; anywhere
where restrictions to air coming into or out of the turbo can be minimized,
gains will be made in turbo spool up time. Furthermore, minimizing exhaust
restrictions opens up the door to making more horsepower. Another added
advantage is that this is one of the few modifications that will actually
improve gas mileage, since the engine does not have to work as hard to make
power. Of course, it will also allow the engine to burn more gas and make
more power when accelerating.
In order to minimize lag and maximize engine efficiency I decided to have all the parts of my intake, exhaust and induction system ported and polished. All P&P work was (with the exception of the intercooler) done by Carl Sidel. I used a Dremel tool to do the intercooler pipes myself, but the heavier sections require an air grinder and some experience. More on acknowledgements.
Induction side: Intercooler:
Here is a picture
of my old intercooler (black) under the new USDM STI intercooler I
installed. The larger intercooler causes less pressure drop and also cools
down the intake charge more efficiently. A cooler intake charge means denser
air which translates into more oxygen for the same pressure; I.E. more
power. Also, the colder the charge the less likely the engine is to knock.
Knife edged, ported and polished. Throttle plate rod and bolts shaved down and polished.
This picture shows one exhaust port ported and polished next to the other one. You can see how much material can be removed, resulting in less restriction to the exhaust flow. The proper method for doing this is gasket matching; opening the ports up to the diameter of the gasket holes. You can see the outline of the gasket on both ports.
I started out running the stock JDM up pipe; it is catless and I had it ported and polished and heat wrapped. One day the flexible flange blew up, so I got a Perrin catless up pipe. Again this was ported and polished and heat wrapped:
This was *spectacular*. The car was fast before the P&P work, but afterwards it felt like it had a completely different engine. The P&P work was so effective at improving exhaust gas flow into the turbo that the stock waste gate was no longer able to maintain stock boost, and my boost level went from 17 to 22PSI. The increase in boost of course brought with it a very large increase in horsepower, but more importantly I could hit 14PSI at as little as 2900RPMs.
Handling / Other stuff:
Greddy Catch Can:
One drawback of forced induction cars is that they will pressurize the crankcase and burn oil that gets spit out by the Positive Crankcase Ventilation (PCV) valve. This oil tends to gum up the valves, coat the intercooler, and is therefore not a good thing. I installed a Greddy catch can to help remedy that. I also added copper mesh inside the can to improve the condensation of oil and water vapor inside it:
For being a daily driven, street vehicle, this car is frightfully
fast; it is very easy to hit the gas at 55MPH passing another car on the
freeway and be going 90 - 100mph by the time I get back to my lane. As a
result, the stock brakes tended to overheat and smoke every time I drove
aggressively. My current braking solution:
Tein TypeHA Coilovers (16 degrees of dampening adjustment, 7K springs up front, 6K in the rear), Tein Pillowball tophats on rear, pillowball camber plates up front, Whiteline 18 - 22mm rear sway bar, Cusco21MM front sway bar, whiteline heavy duty swaybar mounts and endlinks, front and rear strut tower bars, steering rack bushings, rear differential bushings, STI Gr.N transmission and engine mounts, STI Gr.N pitch stop mount... Please check my JDM Engine Swap page for that.
The STI Forged Aluminum Alloy Control arms are lighter (a couple pounds), much stiffer, and have harder rubber bushings than the stock control arms. The Tein Coilovers allow me to rise or lower the car as I see fit; I have an even fender wall gap of about 1.5" all around. In fact, I had a friend of similar weight sit inside the car while I played with the coilovers to get it to sit perfectly flat. Right now I have dampening set on 8 all around and it feels perfectly streetable.
To recap: The differences between the old setup and this setup:
JDM STI Version 8 block instead of JDM WRX Version 5 Type RA block.
Lighter, Hypereutectic cast Vs heavier Forged Pistons
Improved crankshaft design with extra oiling holes
9:1 compression ratio, ARP head studs and 3 layer stainless steel head gaskets.
3 angle valve job on the heads
IHI VF-22 Turbocharger, ported and polished and ceramic coated, Vs. VF-29 turbo.
Right now I am letting the ECU control boost. It seems to have the boost target set at 1 Atmosphere, and it hovers right around there. There is no noticeable extra lag from the bigger turbo, and it is roughly as fast now at 15PSI than it was with the old turbo at 22PSI.
Off boost power is a little bit better, and throttle response seems to have improved as well. There is zero knock with some race fuel in 93 octane, and 153mV of knock on 93 octane. The engine sounds a bit smoother as well. Enough with the talk though, here are the results:
The car puts down approximately 288.5HP between 5900 and 7000RPMs, and 260foot-pounds of torque at 4700RPMs. Torque is over 250ft/lbs between 3600 and 6000RPMs. This is all on 93 octane, with the stock, un tuned ECU.
For comparison purposes a stock STI will put down approximately 260AWHP on this dyno. My car was probably making around 330Horsepower at the crank then. Yes, its pretty quick :)
Completed engine bay photos:
So far the car was quite good; in fact it far (very far) surpassed even the wildest dreams I had before and after buying it. If you told me I would be driving 330horsepower when I bought my 165HP impreza I would have laughed. Still, it wasn't perfect. The Japanese engine came with a Japanese ECU, and, as one would expect, it was designed and tuned to run on Japanese gasoline. Japgas is 100RON, which, here in the US, works out to roughly 96Ron+Mon/2. The effects of this are profound; the ECU is tuned very aggressively as far as ignition timing and air fuel ratios go, and it will detonate and pull timing when run on the best fuels available at the pump in this country. Worse still, the ECU still thought I had a version 5 block, a smaller intercooler and a VF29 turbo, and that's not to say anything about all the porting and polishing work. With this in mind, it is actually somewhat surprising that it worked as well as it did.
But it was time to do better. ECUTEK99 is the only available reflash utility for Subaru ECUs up until 2002 (when ECUTEK02, Accessport, and others, became available since the USDM WRX became a much more popular car than the one my engine came from). Torn between going to a full standalone ECU (namely the Apexi PowerFC, due to its cost and simplicity) or doing a reflash, I chose the reflash route because it would allow me to keep my stock cold start, idle and part throttle maps, which were very good and worked well. I thus had my ECU reflashed and retuned with the ECUTEK99 software. The results?
I am running a modified Version 6 STI Type RA map which incorporates ECU
controlled automatic intercooler water spray and intake air temperature
based load mapping.
Well... For starters, the car is now tuned to run around 20 pounds of boost. This is 6 more PSI than before, and it makes quite a difference... Torque peak also moved up by 30foot pounds, and it now occurs 580RPMs sooner in the power band: More torque with less lag. Horsepower peak went up by about 26HP. Thus the car should now be making around 370HP at the crank, and around 300 foot pounds of torque. I'll dyno it some time, but I'm expecting circa 310AWHP / 300AWTQ. All this on pump gas, without having to worry about fuel additives or detonation. The engine also feels a lot more eager to build boost and go FAST.
That's right: 22PSI at 9:1 compression, on pump gas (93 octane), out of
a VF22 turbo, on a safe daily driver tune.
The perfect car? Not quite. Ultimately what I accomplished is I got an
otherwise ordinary compact car and turned it into something that will
embarrass all but the most expensive cars on the road. From a standing start
the all wheel drive launch, coupled with 370 horsepower, and a curb weight
of 2840pounds will leave behind most Ferraris, Porshes, Corvettes, BMWs, etc
etc... And if the the road isn't perfect, there is almost nothing rear wheel
drive that can keep up. From a roll where all wheel drive is no longer an
advantage, the power to weight ratio will still rocket this car forward
faster than just about anything you can buy in a showroom for under 65000
dollars. It is funny that I had always dreamt of having a Ferrari Testarossa,
and now I have a car that would out perform one in every single possible
But... Still... It will always be a Subaru 2.5RS at heart. The interior is cheap and the paint job has seen 7 years of winter driving. I love this car, but eventually plan to move on to something newer once I graduate and get a full time job. Interestingly enough there is absolutely nothing I see myself buying that will be as fast as this, but I think I've learned enough tuning tricks to fix that problem once the car is paid for and the need for speed shows itself once again... Or maybe I'll just keep the RS and turn it into a track car... Only time (and money) will tell. I'd also like to start up another crazy car project... Like a modified RX-7, or a NSX, or a muscle car buildup.
On the mean time I have one more modification planned for the car: I would like to install a Version 5 / Version 6 STI transmission. The stock 2.5RS tranny has held up well, but I have also shown restraint, and I did manage to break it twice before the car was turboed, so to get the complete package I want a transmission that can handle rough driving... Once I have that, I'll take it down to a 1/4mile track and do some passes, for fun. My friend ScoobySteve ran an 11.8 Second quarter mile with the same engine / same turbo as me, and he was only pushing 18PSI of boost... For comparison purposes, last year's Corvette Z06 has a best 1/4 mile time of 12.4 seconds, and that is a 400 horsepower dedicated sportscar.
On the mean time I will continue to enjoy this car every day, on my way to school, on my long inter state trips, and specially on my track days, autocrosses, rally crosses, ice races, and any other competitive event I can enter. I smile every time I push the gas pedal down, or take a corner. Honk if you see me on the road... Just don't try to rev at me; I'll blow your doors off* :P
*Disclaimer: This is a joke. I did NOT build this car up for street racing, and I think morons who kill themselves street racing deserve it. We'll take it to the track and I will break my transmission trying to launch and then you will win :-)
1st and foremost I would like to thank Tim Sanderson,
who took my car in when I realized there was something wrong with it, did
all the compression and leak down tests, took the engine out and apart, and
assisted me with all the aspects of this repair. Tim is an outstanding mechanic who lives near Milwaukee, WI. If you
need any work done on your car, he's my first recommendation.
Thanks goes to Myles Hechtman and Ryan at Fine Line Imports. Ryan sold me the Version8 engine, and Myles helped me source all the parts I needed to pull this off. If you ever need a performance part for your subaru, Fine Line Imports is my first recommendation! Give them a call, ask for Myles, and tell them Sam sent you ;)
A big thanks to Carl Seidel for all the outstanding port and polish work done on the engine manifold, exhaust headers, up pipe, throttle body and turbocharger. Carl is a rally car driver and an experienced mechanic and he does awesome work for cheap. Send him an e-mail if you want any P&P work done.
Thanks to Kelly Drew (snowbrd4evr on NASIOC) for taking the long drive with me to get my car tuned, and putting up with my driving for thousands of miles.
And a HUGE thanks for all the guys at NASIOC, specially turbosubysteve, with his 11 second JDM-swapped monster and supermoose for all the technical info without which I couldn't have done this.
Comments? Mail me.
People have visited this page since 02/04/06.
Last updated 11/02/10
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� 2006 by Sam Barros. All rights reserved.
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