EvoIII 16G @ 17-19 psi...2.25", 2.50", or 3.0" exhaust?

[kjewer1]

Avoid the flapper mod like the plague The WG spring will have nothing to do with creep as well.

Consider this. There is a given exhaust manifold pressure at a certain airflow rate. That pressure is always trying to open the WG flapper. Thats why we have a spring there to hold it closed. Now ponder this:

Force = Pressure x Area

If the pressure stays the same, but you increase the area of the flapper, you increase the force trying to blow it open. Try to run high boost, good luck.

With a 16g and a stock flapper you can hold up to 25 psi without too much trouble. With a 34mm flapper the boost will go to 25 psi in the midrange, then, almost invariably, fall to 19-20 psi. 19 psi doesnt get a whole lot done... I Did an experiment back in the day and wired the flapper shut (I was using the deltagate on the manifold to actualy control boost). Boost held solid at 25 psi to redline Everyone has always assumed that they were outflowing the turbo, including me. Until I tried this little project. You can search for the actual info on DSMtuners, it would be a year or two old.

So my advise is to NOT get a larger flapper. With enough porting to the turbine hosuing, you can get boost creep below 15 psi on large exhausts. This way you can run 15-25 psi, rather than 10-20

[Shpyder]

u da man. all of that actually made perfect sense to me (even at 1 in the morning). :

[TurbosR4me]

Lets say I was going with a 14B and 3" turbo-back exhaust. Do I need to worry about porting the turbine housing?? (maybe running 16-25 psi)

[soyee7]

what is the max efficiancy rating on the evo3, what boost is considerered the most efficiant without overheating the air.

[JoeWagon]

I just watched a GSX do 12.7@110 on the evo3, and it was running 21 psi. If you figure that we are at elevation, it equals out to the other fast evo3's running 25-26psi. Turn it up until it knocks.

[kjewer1]

Originally Posted by TurbosR4me

Lets say I was going with a 14B and 3" turbo-back exhaust. Do I need to worry about porting the turbine housing?? (maybe running 16-25 psi)

Yes. Creep will likely be over 20 psi on a 3" exhaust. Mine was 22 with a 2.5".

what is the max efficiancy rating on the evo3, what boost is considerered the most efficiant without overheating the air.

I would say once you get over the 35 pound/min mark you should be looking into running race gas. The highest airflow I have seen for the EVO3 is 44 lbs, comapared to the 40 pounds I saw on the regular big16g. Joe G has seen ~38 lbs on the small 16g. When you start to max out those airflow numbers knock becomes the main concern (big intercooler, race gas, cams, etc).

What boost pressure that airflow works out to be depends on the setup in question. Like Joe said, let the knock guide you.