:boost ratio numbers get thrown around a lot without much explanation. Also you really need a mechanical boost and ebp
gauge to know what is going on.
There is a common misconception that vgt turbos "always" run higher ebp
:boost ratio as opposed to non-vgt turbos. But that is not true. They can and will run a higher ebp
:boost ratio when spooling the turbo (only if you desire and command it). You can pick your ebp
:boost ratio with a vgt turbo and adjust this through tuning. I have multiple tunes that run at different ratios. (it has more to do with desired ebp
or desired boost and not necessarily the actual ratio)
Most people want faster spooling turbos down low, so when you mash the throttle you can see upwards of 20:1 ebp
ratio (20psi ebp
:1psi boost). But that usually only lasts for a split second until the turbo is spooled. After that split second the ratio drops WAY down to like 1.5:1 (15psi ebp
:10psi boost). That is how vgt works. You can manipulate the vanes to create excessive back pressure for a split second which will spool the turbo. A 20:1 EBP
:boost ratio will not hurt the motor at those small boost/ebp levels. Heck 20-35psi of ebp
is completely normal and wont hurt anything.
When cruising I have tunes that run at a 1.7:1 ratio (10psi ebp
and 6psi boost) which seem to spool faster and be much more responsive with much less smoke output. I also have some tunes that run 1:1 ratio (3psi ebp
and 3psi boost) Those tunes are usually less responsive and are a little smokier... Interestingly enough they both run about the same egts
at the same cruising speeds.
most people I know see right around 1:1 through 1.2:1 ratio (unless they are throwing a ton of fuel at it). On long hard runs the ratio can start to creep up a little bit to around 1.3:1, which is completely normal and safe. It is the high ratios with higher ebp/boost numbers that you need to worry about. A 2:1 ratio at (90psi ebp
: 45psi boost)... that can blow your motor/headgaskets... but that does not happen with vgt turbos unless something is wrong (stuck vanes, bad tuning, etc). The vanes will adjust to keep that from happening.
Cruising usually around 1:1 - 2:1
Mashing throttle and spooling up the turbo can see upwards of 20:1
1/2 throttle acceleration after turbo is spool can see around 1.5:1
runs after turbo is completely spooled usually see around 1:1 - 1.3:1
But it all depends on which tune and turbo you are running
So I don't think anyone wanted to watch a 10 min video... but I pulled out my cell phone and grabbed a quick video to show a little bit of how the vgt duty cycle, EBP
, and Boost react together.
The gauge is EBP
and you can see boost and vgt duty cycle on the livewire. I know it sounds weird but I recommend watching it a couple of times and stare at different gauges. You just cant see them all at once :rofl:
Hope that helps a little bit.