Dr.Boost

I don't know about that. A T4 at 10 psi will outflow a T25 at 10 psi. It's all about the CFM, not the psi. The T4 at 10 psi is just getting started in it's flow, but a T25 is done and past it's power output, but yeah it would depend on your motor also. Obviously a gigantic turbo won't work as well on a tiny motor, while a palm sized turbo will spool up quick and build boost for most of the rpm band.
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Todd

don't know about that. A T4 at 10 psi will outflow a T25 at 10 psi. It's all about the CFM, not the psi


What you said right there is what I am talking about. A certain amount of cfm of flow on a set engine is what will give you 10psi if restriction. So say on this engine that number is 500cfm. If both turbos are capable of blowing that much air then they can both make 10psi. The question is which one does it more efficiently. Which ever one that is will make the most power at that cfm of flow.

For example.. You have a .60 trim t3 and your d seires engine is right in the middle of the 75% efficiency island. Then you jump up to a 60-1 turbo and its in the 60% island. I believe the properly sized turbo will make the most power.. In this case the t3.

Do you agree?

Dr.Boost

Haha, agreed. My head hurts now.
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2000psi

One more thing to really mess things up.....It also depends on things like how much CFM your engine can flow. You can't get air in without first getting it out.

I like pizza

jeff ran 15 on a dx with out an intercooler and with out fuel management.

Todd

2000psi- huh? Are you refering to our big turbo is better debate?

2000psi

yep. I would rather have a more efficient setup (running a larger turbo slower) and have to wait for the boost than overspeeding a smaller turbo. I think alot of people miss the boat on how important the exhaust flow is out of the engine. Turbine wheel and housing size is VERY important in the efiicieny of your engine....You think about how much more exhaust volume there is in an engine running 10psi @ 7K RPM than a NA engine @7K RPM. Those small turbos like the RHB5 cause exhaust gasses to back up in your exhaust manifold at higher RPMs. And where does this gas go during valve overlap? back in the combustion chamber, keeping an amount of fresh charge out of the cylinder and heating things up in general. I like the idea of having boost only past 3500RPMs or so. That usually means exhaust flow is set up well for that particular engine....through the use of a large A/R turbine housing, open exhaust and a proper exhaust manifold. People see the importance of exhaust flow when their cars are NA, why do they forget when their car becomes turbocharged? sorry for the Novel.

JD

Damn some of you guys make things so complicated. Basically you just want a turbo that will kick in at about 3k and pull to redline. If your turbo dies out before redline it doesnt mean the turbo isnt working it just means it is just pushing too much hot air through the engine because it is working too hard. Case and point is my turbo project. My accord (2.2 f22a) had a tdo4 mitsu turbo on it which was way too small. I hit full boost at like 2200 and it died off like crazy around redline where I would also get some detonation because the air was so hot because of the turbo being overworked. Then I put a mitsu tdo4 on and I hit full boost (9psi) at around 3500 and it pulled all the way to redline with no pinging at all. Reason being because it was bigger and could handle the size of my engine better and more efficiently. Understand now? My car couldnt really handle the 9psi with the smaller turbo because it was too small and wasnt efficient at high rpms but it handles 9psi fine now because the turbo is more suited to the size of the engine.

45psi

i learned a lot from this. it should be added to new user faq.