Yeah, a T25 bb is a LOT nicer unit than the plane bearing model, it should spool up faster. If you are turboing an otherwise stock engine, I would stick with a lower boost level. My T25 easily produced 10 psi on my truck. I don't know what it was capable of, but I had the feeling that it was capable of much more than I was pushing it. I only hit 10 psi a couple of times, because the S-10 2.2L was a notoriously weak engine, and mine had 115k when I turboed it. It was a poor-man's turbo project, but it was very reliable. 6 psi is an extremely good starting point, IMHO. You can always adjust up from there. A good source for info is www.homemadeturbo.com
Keep in mind that the larger turbo you go with, the slower it will spool. I'm not surprised that you said a guy at a local performance shop told you that a T25 would be too small. The "bigger is better" mentality does NOT apply to turbochargers on engines with stock internals. I think a T25 would be an exellent starting point.
BTW: even at 5-6 psi on my S-10, the BOV was nice and loud!
Actually no you got it wrong. A turbo wont provide a certain PSI level, thats determined by a wastegate. Turbo wont blow up if you get more than 15psi, the engine might, but a turbo will keep on boosting until the wastegate opens the path that goes around the turbine.
However, keep in mind that the more you boost the more your exhaust pressure will rise, thats where the turbine side A/R ratio comes to play. Smaller turbine at high boost will have higher exhaust pressure than a turbo with a large turbine scroll. Rise of exhaust pressure will also cause exhaust temp rise, which causes all kinds of confusion in the engine.
Also at 15psi, your combustion temperatures will be almost twice what they are N/A.
yea. i dont think i would ever push 15 in this car. and realisticly i want more accelleration so a smaller turbo would probably be better for that. would it be necessary to block off the internal wastegate and rock an external? or would that have not much purpose if im never going to boost over 15.
Actually no you got it wrong. A turbo wont provide a certain PSI level, thats determined by a wastegate. Turbo wont blow up if you get more than 15psi, the engine might, but a turbo will keep on boosting until the wastegate opens the path that goes around the turbine.
However, keep in mind that the more you boost the more your exhaust pressure will rise, thats where the turbine side A/R ratio comes to play. Smaller turbine at high boost will have higher exhaust pressure than a turbo with a large turbine scroll. Rise of exhaust pressure will also cause exhaust temp rise, which causes all kinds of confusion in the engine.
Also at 15psi, your combustion temperatures will be almost twice what they are N/A.
That's why I said 15psi safely, not limited to.
And Slowrolla, as far as that setup goes, the t25bb has spooled for me as low as 2050 RPM.
Last edited by trancedcorolla; 09-01-2007 at 01:01 PM.
You will definately have stronger acceleration, even at relatively low boost levels. A 2.2L 5-speed S-10 is one of the biggest turds on the road, in stock form. After the turbo, my truck could break the rear tires loose in 3rd gear, when I hit it just right. If you've ever driven a 5-speed, 2.2 S-truck, you'd know what an astonishing feat that was.
yea i can imagine. especially third gear. all this talk of breaking tires lose in third gear and what not is getting me fairly excited to boost my car.
A T25 is actually kinda small for a 2.2L, isn't it? That explains the near-instant response. =)
WRT acceleration, get a properly sized turbo. Going too small will just give you compressor surge at the top end, and you can get /quick/ response with a larger turbo by doing things like ceramic-coating and port/polishing everything from the headers to the rear pipes. http://www.powerlabs.org/swappedimpreza.htm has more on it, if you scroll down to the Porting & Polishing section. Figure out where you want your power band to be and work with that...learn to read compressor maps or talk with your local reputable tuner.
Yeah, a T25 was on the small side for the 2.2, but I wanted something small with my stock internals. That particular turbo was an OEM turbo off a 1988(?) Sunbird turbo with a 2.0, so I figured it was close enough for my 2.2L.
And to be perfectly honest, that turbo was also sized perfectly to my available PayPal funds at the time.
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