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i have a greddy evo2 from my NA setup (2.5"), is it goign to restrict my hp/tq vs having a 3"?

i know restriction for NA is good, but a friend said turbos need a little as well. but im sure none is better for high boost... i dunno, you tell me =)

 
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Lemme correct you, the GReddy exhaust is only 60mm aka 2.25"

If you are not making enough power to justify a 3", it's really almost pointless. The first restriction you should be looking into would be your turbo manifold and turbine housing with A/R.

 
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I understand what you are saying about not being able to hit way higher numbers without some headwork and a cam. That makes sense. But you said you couldnt get any higher than 260 at 18psi, and hes already hitting higher than that at 17. It may just be the way everything is setup, or maybe the particular setup you had at the time. I am almost confident it will hit 300 with the stock head being that it already hit 280.1 with the stock head. The only reason he didnt push further was because the fuel pump wasnt pushing enough fuel. Im pretty sure the stock IM wont handle 300 for very long though. haha.

...and please dont take that as **** talking, thats not it at all, I just know the guy Bob is using to tune is really good at what he does, and with the fuel pump pushing a little more fuel in the motor, he will probably be able to hit the mark.

 
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There are a few things you're overlooking. First off, look at the equipment used. Ask any tuner about power measures on a dynapack vs. dynojet. The dynapacks are known to give higher numbers, but are the best way to tune because you simulate real driving conditions with load. So, that 273 on a dynapack is probably closer to 250-ish on a dynojet. Also, there are temperature and elevation to consider as well.

I was maxing 440cc inejctors at about 18 psi. We made 255 whp. I swapped out for 550cc injectors. I maxed at 20-ish psi at about 260 whp. This was all with a walbro 255 in tank pump and stock cam. I upgraded to 750cc inejctors and a return line with a boost reference aeromotive fpr and suddenly I was at 335 whp on 18 psi. Like Paul said before, I was only using the best components; intake, exhaust manifold, 2.5" ic pipes, open downpipe, etc, but still, that's a massive restriction in the head due to the cam. The point is, the stock cam will only flow so many cfm before you hit a wall, regardless of how good a tuner is. Like I said, I had two of the best Honda tuners in Texas tuning mine. I have personally seen where that wall is and had to overcome it.

For the record, I haven't had any machine work done to my head, its completely stock minus the cam, springs and retainers.

 
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I see what you are saying. I totally understand. You do have a point however that the dynapacks do give out lower numbers. I will be interested to find out what he can get out of the stock head.