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Discussion Starter · #1 ·
Hi Folks, I wanted to see if I could get some help from the mega mind here.

2013 Focus ST with built motor, stage 2 cams, and ported head (amongst all other bolt ons). Recently did a G25-550 .72 AR turbo install, externally gated. Fueling is 94 octane and 4 port Aux fueling with additional E30 Tune.

Day 1 turbo is installed, received low boost tune from stratified, all seemed good, drove approx 100kms home with higher boost tune (maybe 22-24psi)
Day 2 stratified dyno tune, started with 94, made around 340whp, on a heartbreaking mustang dyno. Then went to E30 and made 400wh
Drove home that night (around 5 kilometres) and no issue. Went out that evening and after 1 WOT run turbo started making a siren like whirl. Gingerly drove home.

Upon inspection significant shaft play In the turbo.

Removed turbo and sent to ATP, fortunately Garrett warrantied the turbo, sent back a new unit. Me being concerned as to what caused it, ordered the Garrett matching turbo speed sensor and a Digital Turbo Speed Gauge from FullRace. It can be calibrated to turbo specifica and has pre loaded calibrations.

Jump forward a few weeks and new turbo is installed. Speed gauge wired. At about 21psi 3rd gear the car is registering 186,000rpm. Note the max speed of the turbo is 185,000rpm. So at this point I’m concerned and monitoring closely. At 3rd gear 13-15psi I’m seeing around 13-140,000rpm. So this gets me thinking did i over-spin the previous turbo? Well on one hand Garrett says the failure was not due to overspin. But on the other the speed gauge says otherwise.

Upon stratified request we leak test the car.We manage to maintain 20psi before the air starts pushing through the engine. No leaks found.

Next thought process, let’s compare datalog data From the dyno tuning. Our last pull E30, saw peak airflow lb/min of 41.35 @ peak psi 26.4
Peak boost saw 27.6psi @ 24.2lb/min

Now if you look at the chart I’veadded from Garrett. Both those charted numbers seem to land me well in the safe zone of the turbo. However I’m not adjusting for air pressure at sea level, I’m in Toronto so around 700ft.
Can anyone pass on some suggestions?

if you’ve made it this far, we’ll I’m getting frustrated and Stratified isn’t being of much help at this point. Thanks for your help!
 

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2014 ST3. Garrett GTX2860R Gen 2. FBO
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The only thing I can offer here is an explanation for the shaft speed.

Boost is waste. It's air the engine cannot consume.

When you install things like cams that increase engine airflow characteristics, the turbo has to spin faster to reach a target boost (waste) pressure than on a stock cammed/displacement engine. Especially if those cams have some overlap.

If Garrett says it wasn't from an overspeed condition, I'd take their word. We have another member fighting them right now on a turbo replacement that they seem to think wasn't defect-related. So if they approved your replacement, it was likely a defect of some sort.
 

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Discussion Starter · #3 ·
The only thing I can offer here is an explanation for the shaft speed.

Boost is waste. It's air the engine cannot consume.

When you install things like cams that increase engine airflow characteristics, the turbo has to spin faster to reach a target boost (waste) pressure than on a stock cammed/displacement engine. Especially if those cams have some overlap.

If Garrett says it wasn't from an overspeed condition, I'd take their word. We have another member fighting them right now on a turbo replacement that they seem to think wasn't defect-related. So if they approved your replacement, it was likely a defect of some sort.
The only thing I can offer here is an explanation for the shaft speed.

Boost is waste. It's air the engine cannot consume.

When you install things like cams that increase engine airflow characteristics, the turbo has to spin faster to reach a target boost (waste) pressure than on a stock cammed/displacement engine. Especially if those cams have some overlap.

If Garrett says it wasn't from an overspeed condition, I'd take their word. We have another member fighting them right now on a turbo replacement that they seem to think wasn't defect-related. So if they approved your replacement, it was likely a defect of some sort.
Thanks for your input.
I reviewed this webpage from Garrett:

It explains how to read the 3D graph I posted earlier (I was reading it wrong) you need to apply a few other factors in order to get the proper calculated values.
After applying the values I land at a pressure ratio of 3 and calculated air flow of 41. This still lands me safely under the 175000 RPM mark.
 

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So this leaves me with the question, why is the gauge reading so far off
Is the vain count set correctly for the gauge to read true shaft speed?

I’ve posted elsewhere that my G25-550 has 50k miles on it. It’s feeding a stroker now but the only tune tune finished is 93 octane on DI. This turbo on the 2.0l and 2.3l made 28-29 psi on that fuel. On e85 the 2.0l was making 450/450 on the rollers. I’ve never asked my tuner if we could push the psi farther because I don’t want to do 4 bar map sensors.
 

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It may need calibration on the speed sensor. Does the turbo use a restriction for oil pressure? On the first turbo, it may had starved the bearings at high speed causing excessive wear.
 

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Discussion Starter · #9 ·
Is the vain count set correctly for the gauge to read true shaft speed?

I’ve posted elsewhere that my G25-550 has 50k miles on it. It’s feeding a stroker now but the only tune tune finished is 93 octane on DI. This turbo on the 2.0l and 2.3l made 28-29 psi on that fuel. On e85 the 2.0l was making 450/450 on the rollers. I’ve never asked my tuner if we could push the psi farther because I don’t want to do 4 bar map sensors.
Yes, vain count is at 9 I believe, if anyone has a different count id be happy to know.

I’ve seen some Turbos have half blades further inside the impeller, I dont think the G25 does though.
 

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What kind of intercooler do you have?
20deg C is a big raise. This usually means that intercooler is not up to the task and that leads to bigger pressure drop across IC.
Out TIP sensor is at the IC outlet so if you add that pressure drop you will get actual PR which turbo is trying to achieve.
This means that if you are demanding 28psi at TIP sensor, turbo actually needs to provide 28psi + pressure drop across IC and piping from compressor outlet to IC.
Do you still have stock piping?

Jump forward a few weeks and new turbo is installed. Speed gauge wired. At about 21psi 3rd gear the car is registering 186,000rpm. Note the max speed of the turbo is 185,000rpm. So at this point I’m concerned and monitoring closely. At 3rd gear 13-15psi I’m seeing around 13-140,000rpm. So this gets me thinking did i over-spin the previous turbo? Well on one hand Garrett says the failure was not due to overspin. But on the other the speed gauge says otherwise.
Engine rpm would be also good info so we can see if it lands on the compressor map as it should.
If you are seeing 130-140k rpm at 13-15psi at 6500rpm for example then this looks OK
21psi at 6500rpm should be around 160k rpm

This suggests that there is a leak. Maybe your BOV cracks open after certain boost pressure.
How is you BOV conected? To intake manifold? Have you tried to tighten BOV spring?

Edit:
looking at the shape of charge temp it looks like it raises exponentially. I checked my charge temps and they raise more linear.
This could could back up the story of (BOV) leak. Turbo trying to compensate going into more inefficient regions or even over spinning.
 

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Discussion Starter · #11 ·
What kind of intercooler do you have?
20deg C is a big raise. This usually means that intercooler is not up to the task and that leads to bigger pressure drop across IC.
Out TIP sensor is at the IC outlet so if you add that pressure drop you will get actual PR which turbo is trying to achieve.
This means that if you are demanding 28psi at TIP sensor, turbo actually needs to provide 28psi + pressure drop across IC and piping from compressor outlet to IC.
Do you still have stock piping?

Engine rpm would be also good info so we can see if it lands on the compressor map as it should.
If you are seeing 130-140k rpm at 13-15psi at 6500rpm for example then this looks OK
21psi at 6500rpm should be around 160k rpm

This suggests that there is a leak. Maybe your BOV cracks open after certain boost pressure.
How is you BOV conected? To intake manifold? Have you tried to tighten BOV spring?

Edit:
looking at the shape of charge temp it looks like it raises exponentially. I checked my charge temps and they raise more linear.
This could could back up the story of (BOV) leak. Turbo trying to compensate going into more inefficient regions or even over spinning.
Running a mishimoto Intercooler, it’s not the kit they make but I believe a similar sized one.
Stock cold side piping but aftermarket hot side.
BOV is controlled by guardian Angel, however I’m thinking of temp removing this so we can remove it from the failure situation.
Also I’d have to ask my mechanic where he pulled the boost ref from.
I haven’t tried the bov spring, would this require tuner adjustment? It’s a Turbosmart Raceport
 

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Perhaps someone can better explain to me BOV Spring pressure.

here is the chart from Turbosmart:

currently there is 1 blue spring factory installed.It is rated at 18inHG or 8.8psi

if I’m understanding this properly does spring pressure have to be based on max psi?
I’m running a 14.5# spring combination on the waste gate. I believe most tuners recommend 1/2 the target boost as spring rate for the waste gate. BOV rate? I don’t even know if it can be changed with a HKS unit.
 

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If your BOV is controlled with MAP pressure try adding one more spring (weakest one) .
If MAP pressure + spring pressure is less than compressor outler pressure, BOV will start opening.
On my BOV I can preload the spring by turning the cap left / right. Maybe you can do the same since it states 14 - 18 ihHg in the left column.
 

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If your BOV is controlled with MAP pressure try adding one more spring (weakest one) .
If MAP pressure + spring pressure is less than compressor outler pressure, BOV will start opening.
On my BOV I can preload the spring by turning the cap left / right. Maybe you can do the same since it states 14 - 18 ihHg in the left column.
Boost reference from the compressor holds the BOV closed so if your boost reference is lost it will vent boost at spring pressure right?
Does this work the same for both HKS and TIAL? I know one of push and the other pull operation. Can’t use a Gardian Angel on a HKS.
 

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I don't know how guardian angel is working but without using it, line coming to BOV has to be on the other side of the throttle body. If it came from compressor outlet there would be always the same pressure on the bottom and top of the BOV. On the other hamd if it's coming from intake manifold then once throttle closes MAP drops while compressor outlet surges little bit and with that there is a difference in pressures which opens the BOV.
This is my understanding, I may be wrong.
 

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Yes your right it’s not coming from the compressor but the manifold.
 

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Discussion Starter · #18 ·
Thought Id post an update. Ive spoken with Full-Race, they have confirmed the turbo speed gauge is working within spec, however they too notice the speed is reading high based on the numbers the car is seeing, there best guess…boost leak. I attempted to leak test the car, going from turbo inlet side, and can only get about 20 psi into the system Before it starts pushing through the engine. Does anyone have a better suggestion? Car is going into storage for the winter, so now its just time to research until the spring and hopefully solve it. Always open to your ideas. Thanks for reading!
 

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What amount vacuum are you reading? With overlap cams the vacuum most be very low or non-existent. That will have an effect on the "Guardian angel" and what springs to use.
 
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