Q.
is turbo surge a mismatch turbo
and it will surge on every and any engine?
i.e the compressor / turbine is mismatched.
or is it the engine Ve / turbo is mismatched?
i.e the engine just cannot consume the volume
being supplied?
i have very steady boost @ 1bar but above that
i have pulses of boost rising and falling at half
second intervals(is that surge)?
no matter how much fettling i do with the apexi
i can't smooth boost.

 

wont surge on every engine, not by a long shot, unless its something REALLY stupid.

worse on small engines, ie the kinds of things we use.

mapping can help.

 

..lee does the surge clear above a certain rpm?..as it should in theory if not then mismatched turbo surely

 

There are many reasons for surge.
A mismatch can certainly cause it, ALL engines have it, but usually to a degree that you do not notice by careful matching of turbine and compressor sizes as well as other tricks.
caused initially by the pressure fluctuations of the pistons rising and falling.
Even though the mean mass flow rate might be greater than the surrge line, surge can still occur due to the minimum mass flow rate at the pulse(piston) peak can be low enough for this to occur.
Small ports keep gas velocity high so helping to eliminate or lessen surge.
tabetha

 

..your small port theory is bollocks...a T4 on a std yb head can not get more than 25psi before surge..open up the ports and there it goes!

 

Don't people port the heads on YBs when they run a T38 because they'd get surge otherwise?

Didn't Comedy Dan or Butch - one or other - have a ported head for those reasons?

 

Hmmm it feels much worse than it looks.
the 1 bar in pink was awsomely steady on
the apexi(a flat line infact) the car accelerated
constantly unlike at 1.5bar you can actually
feel the car accelerate and slow with every trough

.