hey guys, just wonder why can turbos only handle a certain amount of power. For example my turbo the gt28rs.86 can only handle upto 350bhp, altho we know it handles a bit more and other turbos like the gt30 series can handle upto/over 400bhp at less boost pressure.

If you go to the Garrett website and take a look at the tutorial section there's some useful information on how different parameters affect a turbo's performance, it should tell you most of what you want to know.

Turbo is an air pump

A larger pump will pump more air

More air with the right ammout of fuel will make more power.

how does that explain it if you use same pressures but one turbo produces more power than the other?

Oh dear, i can see one of these debates coming up <img src="/forum/images/graemlins/laugh.gif" alt="" />

From what I understand it’s all about volume of air
Basically if you turbo compressor housing holds 1liter of air and a bigger turbo compressor housing holds 1.5 litre’s of air , both at 1.2 bar the bigger turbo has the ability to put more air into your engine . Then you add the right amount of fuel which gives you more power

Another point is turbo efficiency i.e. If you run a STD turbo at 1.4 bar to flow the same amount of air as a gt28 at a lower boost pressure, the STD turbo is working a lot harder there for increasing in temperature which increases your inlet temp’s which then lowers your power levels.

Simple, pressure is irrelevent. Its the mass flowrate that is important. A efficient working turbo will flow more air mass at the same pressure over an inefficient (usually smaller) turbo.

A larger turbine will also allow lower exhaust manifold pressure which will reduce the pumping loss the engine has to do.