SS5: The proviso here should be type of Turbo as the GT DBB Turbo's have made me totally reassess what I believed to be correct about sizing/response and pipe size.
intercooler
- Thread starter i165mk
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Yep they react very differently to anything I've played with in the past, all the old knowledge is just about useless.
Basically the powerband is bumped down few hundred RPM's, maybe as much as 1000? I still don't see a need for 3" IC piping though, you think if the powerband is getting moved down a lot and critical velocity is being reached earlier on with 2.5" piping, then a bump to 2.75" would be in store...
Needs and requirements of exhuast piping and intake piping are not related.
edit: they are related, but not the same. I misstated that.
edit: they are related, but not the same. I misstated that.
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When reading intercooler FAQ's, I can't find any that suggest smaller intercoolers for smaller engines or horsepower. You would have to go into the airflow, which I am not doing.
Smaller turbo yes, but the intercooler seems to not matter, to a point. It does seem like really large piping will hurt veolocity, as it does it with intake manifolds and cylinder head ports.
Smaller turbo yes, but the intercooler seems to not matter, to a point. It does seem like really large piping will hurt veolocity, as it does it with intake manifolds and cylinder head ports.
SS5: Just reporting my real world findings, I used to stick with the theoretical when sizing pipes and the 3540R on 2.5" pipes at 20 psi should have been no where near Critical and on 3" should be a laggy bitch but isn't even close even with a 1.06ar Hotside.
1psi @ 1900 rpm amazes me 
I think back to a 700 hp crank Turbo on a 3.0L back in the day and you might have had a 500rpm powerband from 5500>6000.
I think back to a 700 hp crank Turbo on a 3.0L back in the day and you might have had a 500rpm powerband from 5500>6000.
That doesn't really matter, you need to match the piping to the turbo and what you goals are. The throttle body itself is so short that the size difference is negligable (sp?), just as long as you have calculated what size piping you need and it comes out to you needing 2.5", then just make sure the smallest part of you piping is indeed 2.5".
I suggest reading this to help you decide what you need
http://www.supramania.com/forums/showthread.php?p=608539#post608539
I suggest reading this to help you decide what you need
http://www.supramania.com/forums/showthread.php?p=608539#post608539
QWIKSTRIKE
475rwhp459torq an climbin
If you have a 3:" outlet on the IC use 3" IC piping. Why go to a large tb then restrict it with a 2.5" tubed inlet. It will be very responsive trust me.
Responsive for your setup maybe. Again, tune your setup for what your goals are, other people's will be different.
Your statement is confusing. 2.5" tubed inlet of what? You just said using 3" piping....
Your statement is confusing. 2.5" tubed inlet of what? You just said using 3" piping....
The Q45 ID is 80mm...that's 3.15". A throttle body is more restrictive compared to the same size pipe diameter due to the throttle plate. You want the TB a 1/2" or so larger in diameter than your piping.
SS5 is correct...you choose piping diameter to suit the flow of the specific turbo. The piping/IC set-up has an effect...a FFIM has much more of a direct routing (less bends/length) than the stock route. Pressure drop across the IC does too.
Like IJ said above, the new GT series turbos have better flow a lot earlier in the rpm band...you may want larger piping diameter to support it. How you run the motor, specifically where in the rpm band you spend the most time, and how you want it to perform in this regime is what drives your decision.
SS5 is correct...you choose piping diameter to suit the flow of the specific turbo. The piping/IC set-up has an effect...a FFIM has much more of a direct routing (less bends/length) than the stock route. Pressure drop across the IC does too.
Like IJ said above, the new GT series turbos have better flow a lot earlier in the rpm band...you may want larger piping diameter to support it. How you run the motor, specifically where in the rpm band you spend the most time, and how you want it to perform in this regime is what drives your decision.