Okay, there has been a lot of talk in the past about what size turbo to go with on the subie's. I'm talking about 2.5L and mainly the SOHC ones, but the DOHC ones aren't much different.
Now, I'm running a T-28 Turbo with a Large Top mount intercooler and 3" exhaust. I have a Fuel Computer, a ITC, and a ACT clutch.
Notes with the T28 Turbo:
5lbs Boost thoughts= WHOW, this is nice, it pulls all the way to redline and it is MUCH quicker than stock. Makes a Stock car feel like a dog.
7.5lbs Boost Thoughts= Now we are getting somewhere, the car seems to be taking it okay with only a bit of retard after 2600rpm. My stock clutch holds about 50% of the time in 5th now, and when I ran Octane booster and turned up the timing it would never hold 5gh gear, and only hold 4th gear 50% of the time. The car had REALLY fast throttle response this way to.
NOW I'm at 13lbs of boost with the T28 Turbo= HMMM. . . 1st-3rd gear ROCK, but 4th and 5th kinda are weak. The Poor T28 is out of its efficiency as far as RPM of the turbo go. The little turbo is REALLY HUFFIN and PUFFIN to make that boost on this 2.5L. I would say that anything over around 10-11lbs of boost on a 2.5L and a T28 turbo is not really worth it. The efficiency of the turbo goes down so much that almost no HP is made even though you have more boost.
Turbo size note: So, the T28 is PERFECT for anyone that wants to be around 235-280ish HP and somewhere under 11lbs of boost. Believe me PERFECT. But if you want more you need to go with something bigger.
Now TMR Impreza (Donald) was running a T3/T4 at first and the car was CRAZY fast on the Top end (4th and 5th Gears) but was a little sluggish in the lower gears. Around a month or two before he crashed his car he changed it to a T28/T03 and he said it was PERFECT for around 10-15lbs of boost, maybe a tad more, but thatís pushing it. I would have to agree, I got a few rides in it and it felt a LOT like my car in the lower gears, but was much stronger in the top gears than my car is.
So, Pick your Turbo size according to WHERE you want to go in the end so you don't have to buy another one like I'm looking into doing now.
How fast is MY99 car with the T28 turbo at 13lbs of boost you ask? Well first off, I'm still RUNNING RICH even with the stock injectors. But I was on the FWY and caught up to a Pontiac WS6 (Pontiac's Cameo SS version with the ram air). at around 75mph we both Stomped on it. I was RIGHT next to him all the way to 100mph, then SHIFT to 5th, STILL NEXT TO HIM!!! all the way to 135. I know our Speedos only go to 120, but I know 135 cuz he got off on the same off ramp and he rolled his window down to say "NICE CAR". I then asked him how fast we went. Next. . . We stopped at a stoplight just a min after this. I LAUNCHED the car out of first pulling about HALF a car length ahead, BAM- hit second REALLY Clean and SMOOTH and LAUNCHED ANOTHER half Car Length. I held that ONE car length all the way to around 100mph. (mind you this was out in the boonies with almost nothing around but farm land.) SO, I think I'm doing quite well, I'm keeping up with a 300+HP car on the move, and pull him on the line. :-)