downfall of running 3" exhaust?

[BuGS]

too small can also result in boost creep/power not gained.

Do you know what boost creep is?? By what you wrote there it doesn't sound like it.

[JWMotorsports]

460 injectors on a killer 16G are way to small....IF your looking to run much boost at all. You should utilize the tool on http://www.rceng.com for injector sizeing. We've ran a small 16G on a BP w/ RC 440 injectors w/ a S-AFC II and pushed those injectors to their limits with under 20psi of boost due to the Pro-LX ecu's duty cylce settings and OEM fuel pressure. With a full standalone we pushed upwards of 18psi w/ the 440's and pump gas. My old setup with a B6T & VJ-14 had 2.5" exhaust with 440's and a S-AFC I in which the car did idle pretty rich but it ran very well with the timing advanced to the point it was right there on the edge of detination. I could walk away from a BMW M3 (stock 333HP) with the lil VJ-14 @ 14.5psi. As for exhaust you cannot go to big on a turbo car. I've personally experimented with larger exhausts vs smaller exhausts. The larger I went the FASTER the spool started and it hit the target pressure much faster as well. I'm talking gaines of 500+RPMs for it to hit set boost with a GT3076R and see boost as low as 2500RPMs (not more than 5psi until above 3500RPMs) with a STOCK bottom end B6T. HP made HUGE gains with this big turbo. On the 16g's I do recommend 3". As for REALLY small turbos like the VJ-14 they are so small and run out of flow so fast you won't see much gains with exhaust larger than 2.5"

[cjthor]

Im running FULL 3 inch exhaust on my car and it works just fine. I have a mandrel bent 3 inch downpipe, hi flow cat, and a race muffler. Shes good to go!

[Steeb]

Do you know what boost creep is?? By what you wrote there it doesn't sound like it.

similar explaination i have for internal wastegated turbos and divorced downpipes.

2 unequal sized paths flowing into the same piping causes turbulance which can cause the internal wastegate to not flow as well as the lines you took to long to draw on the turbine and compressor maps. if your exhaust could flow better you would be that much closer to the line you drew.

internally gated turbos do the funny thing of creeping and spiking even if you port it. if there is enough turbulance you can reduce the flow of the internal wastegate enough to create even boost spiking with the internal wastegate wide open. almost like standing in a cave during an extreme blizzard or sandstorm.

if you reduce turbulance in the exhaust you can increase flow. the more you can flow at the same psi, the more your volumeteric effeciency increased. if you know what increasing volumetric efficiency does than give yourself a pat on the back.

benchmark racing is like having a drag race with dynos.

about me not knowing what im talking about, my other car hit 2.1bar, recorded by my avcr. i was using the stock downpipe/primary cat running 1 bar and at times the avcr had trouble with exteme boost spikes like so that could be avoided. no more problems full 3" downpipe and full exhaust. if your turbo can outflow your exhaust it can cause boost spike and creep even completely stock. cats are a turbos worst friend. especially when they place them right after the turbos. cars setup this way are very prone to boost spiking especially when the cat is going bad and starting to melt into a big glob from the extreme heat.

then there is also boost creep, the boost creep you had in mind which are the ones u see on paper. those you need to keep under control with a good external wastegate if possible. then again, i wasnt talking about that kind of boost creep...