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Old 01-11-2001, 12:51 AM   #1
thepas
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Post Personal Turbo SIZE experience. What Size to pick notes.

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. :-)


Kyle
BoostedImpreza@aol.com
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Old 01-11-2001, 12:57 AM   #2
Kevin Thomas
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Old 01-10-2001, 01:03 PM   #3
stimpy
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Thanks a lot for the insight. This is actually something I am currently looking at and I do appreciate it

Jon
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Old 01-10-2001, 01:06 PM   #4
thepas
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Yeah, it's a bit easier to understand something written like this than something like that Boost caculator, and those arn't always right for every car. . Glad to help!

Kyle
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Old 01-10-2001, 01:13 PM   #5
Eric SS
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swap and N20. gone. : (

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DO you have stock pistons and bottom end?

Eric
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Old 01-10-2001, 01:21 PM   #6
omahasubaru
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so when you gonna sell your T28??
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Old 01-10-2001, 01:43 PM   #7
TMR Impreza
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Our little MRS is making 290 at the wheels out of a stock 1.8 and a stock T28. We can toy with an SS camaro and kept on par with a 911 Turbo all the way to about 145. How do I know? Don't ask Now my car was perfect with the T28\TO3 that JC sells. The kit when I first recieved it needed LOTS of help but as time went on JC helped me, ED at ISR made it all work well and I ended up with a decent kit.
So Kyle, 13lb's. I remember hearing someone say " I only want to run 7lb's, thats it" I am not going to mention any name *cough* KYLE *cough* . Want to run the MRS at 10lb's? Call me. Could be fun.
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Old 01-10-2001, 02:42 PM   #8
Rick Hunter
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Kyle,

Thanks for the detailed report! What kind of fuel computer are you running? Have you upgraded your fuel pump?
13 lbs... woah that's a lot. Sounds like you're having a blast.

So a T28/T03 is the best size for our engines to do 230-300 hp. Would there be a big difference between a T28/T03 and a T3?
The kits that I've looked at all use T3/T04s. I'd like to have minimal lag in 2nd since I'll be auto-xing this summer a lot but i'd also like good boost all the way to redline so now I'm torn between the turbo sizes you mentioned. argh! What to do...

Ingo



[This message has been edited by Rick Hunter (edited January 10, 2001).]
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Old 01-10-2001, 02:48 PM   #9
Skidd
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A little bit of a side question.
All this talk about T28, T4, T3/T4 ect... Is there somewhere on the net that goes into a bit of detail explaning the difference between all these turbos?
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Old 01-10-2001, 03:50 PM   #10
jeffg
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All of the numbers, T28, T3, etc... are model numbers for various turbo manufacturers. I bet if you went to the home pages of Garrett, or Turbonetics (spelling?) you could get details
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Old 01-10-2001, 04:29 PM   #11
thepas
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First off, the my motor is STOCK internaly. . . ya ya, cough cough, I'm up at 13lbs. . I would almost rather be running around 11lbs of boost, it just doesn't seem worth running any more than that with the T28.

omahasubaru : I would like to sell it right now. . Let me get a Price. Note: this is just the turbo, not the up pipe/downpipe ect.

Rick Hunter: just look at my post earlier up top, pick what boost/hp you want to be at and pick that size turbo. Like I said, Donald was running a T03/T04 and it was just a bit big unless you want to go over 350-375HP or so. All these numbers are just kinda from guesstimating, not dyno proven.

Skidd : The numbers just are the types of turbos. The T28 is a Gerret turbo and is about the smallest you would ever want to put on a 2.5L, they have hybrids where the Exhaust side is from a T28, but the compressor side is a T03. you'll get the hang of it as you read.

Kyle
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Old 01-10-2001, 04:32 PM   #12
Dan_E
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I'm Glad I went with the T3 turbo...(still waiting for it) but from what I've read, its the happy medium. I don't plan on racing, but when I turn up the boost, I want the BOOST TO TURN UP! None of that T28 top end choke and no T04 low end lag.
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Old 01-10-2001, 04:34 PM   #13
thepas
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I wouldn't really call it Lag, you get boost, but you go through the gears soooo dang fast the turbo doesn't get in it's most efficiant sweet spot.

Kyle
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Old 01-11-2001, 04:10 PM   #14
UCmego
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Do you guys who are running high boost have problems with he engine heat on topend? It is amazing to me that you are running stock compression ratios and 13psi on top of that! I would have expected the motor to overheat pretty quick! Have you quarter-miled the car? Probably high 12s from what you are saying.

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Old 01-11-2001, 04:16 PM   #15
N/A
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Is that loss of power in the higher gears possibly due to the fact that the compression ratio, boost levels and design make it so that the intake tempts are getting a little too high? If the air gets hot enough it will be obvious when doing pulls all the way through the gears. Top Mount IC's aren't the most efficient as they sit above a big heater, the scoop as cool as they look only allow so much air through them and you can't get that large of a cooler under the RS hood. That is if you compare a top mount to a front mount.
I don't work with Subaru's anymore (just don't get a chance) but you might want to look at something larger then. Then T28 is about right though if you want a more street friendly less peaky car.
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Old 01-11-2001, 06:19 PM   #16
thepas
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Okay, N/A has brought up a topic people have discussed before, the TOP mount IC thing. Let me tell you, Unless I'm sitting stopped for more than like ONE min it doesn't really matter. My IC stays COOL to the touch if I'm moving at the least bit. I feel the Top mount IC is MUCH MUCH more efficient than most people think. It is currently MUCH more efficient than I would have ever thought.

To combat the Heat soak at stops and such I'm going to install a very inexpensive IC water spray system that most people could make for under $50. Temps are looking warm at 13lbs, thatís why I'm looking into water injection now. Thatís what almost all the cyclone and typhoon owners needed to do if they upped there boost at all due to there motors being easy to blow.

Kyle
Boostedimpreza@aol.com
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Old 01-11-2001, 06:52 PM   #17
thepas
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Talking

Hey, here is a pic under my Hood as of now.





By the way, the Brown stuff on the clear plastic/plexiglass is just the protective film, I only took a little off to show what it will look like with it all off. If I get my lazy but out of my house I will go take it all off and take a pic of it all clean.

Kyle

[This message has been edited by thepas (edited January 11, 2001).]
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Old 01-12-2001, 10:30 AM   #18
BugBomb
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Why a cold-air intake for an intercooled turbo? Its redundant. Its your engine though, so I am not telling you what to do with it. I just think its a waste of time and material.


my .02
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Old 01-12-2001, 10:45 AM   #19
Kevin Thomas
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Thumbs up

"Why a cold-air intake for an intercooled turbo?"

Because now the air entering the intercooler is even cooler than it would have been without it. Just think if it's 20F outside and ambient temps are going into the intake, it would have some cooling affect of the hot air the turbo is pushing into the intercooler.

I don't have proof of this but I was thinking the same as you before. Now, Im thinking differently so I bought the CAI WRX bonnet vent scoop from MRT to add to the intercooler I will be putting on.

BTW: I talked to a guy I know that drags his Supra on street nights at Atco and by him taking out his headlights at the dragstrip allowing cooler air in, he gained 2-3mph in his trap speed. Also, I posted that my trap speed went up by 1-2mph (96-97mph vs 94-95mph) a while back after adding the vent scoop to allow colder air in. And this is without an intercooler, yet.

[This message has been edited by Kevin Thomas (edited January 12, 2001).]
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Old 01-12-2001, 01:07 PM   #20
Sauginius
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Hey Kyle, if, for any reason, omahasubaru doesn't want your T28, let me know
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Old 01-12-2001, 01:52 PM   #21
thepas
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Thanks Kevin, your right, the cooler the intake temp, the cooler the temp into the IC, the cooler the air is overall. . . when your under the hook you get eddities (SP?) of hot air off the radiator, NOT GOOD.

I will post a FOR SALE, T28 Turbo when I get a $ for it.

Kyle
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Old 01-12-2001, 01:56 PM   #22
thepas
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Okay, I will be posting a for sale on the turbo today, so watch for it.

Kyle
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Old 01-13-2001, 01:56 AM   #23
N/A
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What I don't understand is why somebody would pay $600 for a top mount when you can buy a factory Evo or GTR front mount out of Carboy mag here in Japan for about $200. The water sprayers are a good idea though because I even used them on my front mounted setup. It allowed me to relocate the air sensor to free up some room for the racing BOV and some other toys. I would imagine that the top mounts temps would be lower if you would get some weather stripping and make a seal between the underside of the scoop and the top of the IC. It would also then look more like the factory WRX setup. Air would have to go through the IC instead of being able to go around it.
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Old 01-13-2001, 02:02 AM   #24
thepas
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Yeah, I have a IC Shroud idea I'm going to try. . . I have some nice pics I will be posting from the LA Auto show, there were a few nice cars there. . .

Kyle
Boostedimpreza@aol.com
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