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What is turbo surge?

17K views 12 replies 7 participants last post by  Term3 
#1 ·
I've been reading a lot on here and I am new to this site, and I hear a lot about turbo surge? Can someone explain to me what that is?
 
#3 ·
As far as i understand...what is actually happening when the turbo surges is that the boost pressure on intake side overcomes the drive pressure on the turbine (exhaust) side which causes it to stall somewhat.
 
#4 ·
Yes, it is a reverse flow thru the compressor. You get the "barking" sound because the flow reverses dropping the pressure a little to momentarily equalize pressure on both sides of the compressor but the turbo is still loosing rpm which means it still is not producing enough pressure to overcome the pressure on the discharge side so the flow reverses thru the turbo again until the turbo is able to overcome the pressure on the discharge side. That's why the "barking" sound drops off and the time between the "barks" gets shorter. I've seen the aftermath of a turbo surge on a large 16 cylinder diesel generator that had a governor screw up, one of the turbos had blown apart in a matter of minutes.
 
#5 ·
It's not a reverse flow through the compressor at all. At the high RPM your compressor wheel will see, as it is cutting through the air in the compressor housing all is well until that air flow is disturbed. Turbo surge occurs as the air begins to buffet over and across the wheel reducing the wheels ability to pull and compress the air flow. Ford redesigned this wheel for the 99.5 - 03 7.3L, that's why these model years are predisposed to this problem. The wheel was re-designed to quiet turbo noise, but obviously went a little to far with the wheel, but never properly re-designed the housing. During surge events you're still compressing air, but much less effectively.

When your motor is running the turbo shaft or quill is riding on a thin film of oil between the journal bearing and the quill surface. Surge disrupts this working bearing and will damage the thrust plate, journal bearing(s) and possibly the wheel/comp housing if the damage is enough. Every time you hear that buffeting air or surge you can think of a hammer banging on the bearing surfaces.

The root cause of what we call turbo surge is a very common phenomena in any centrifugal compressor application from simple turbo's to large turboshaft engines. It can be seen ripping the edges of flags blowing in the breeze, to aircraft falling out of the sky during wind shear events (Air buffeting across the bottom of the wing)
 
#7 ·
This is just an FYI. The WW is what Ford was running prior to making the changes to the wheel design for 99.5, so it was stock on the e99's and some Van turbo's.

The WW will definitely help, but does not always eliminate surging. The true cure is a ported compressor shroud from ATS. A wheel alone, any wheel is not enough as it falls short of addressing the real issue of air management in front of the compressor wheel. But it does help. Also, you may not even notice, but the WW moves less air than the stocker and is one reason it reduces surge. Because your goal is to extend the life of the turbo any mod that goes in that direction is a good one.

Searching on here will yield a couple ways to install a WW. I did mine in with the turbo in the truck, just be careful not to damage anything. I also did an ATS shroud about 2 months later and that killed all surge. I have since gone on to a GTP38r, which will surge if moving fast enough.
 
#12 ·
You're getting higher pressure than 18 psi out of your stock turbo?? it's not about what pressure you're developing surge. It's more to do with wheel speed and the high/low pressure interface in the compressor housing. just so happens in this application, powerstroke stock garret turbo for 99.5-03 that you see it at these pressures. Your PCM will defuel your injectors at or around 20psi if you ever get there in a stock config with tuner.

Anything above 20 means a mod or two to the turbo which probably did away with the surge. Also, given the right circumstances it could develop at higher pressures, but most research and development addressed these things before production. So what Ford did to quiet the turbo worked but accentuated or plus'd what was already probably there to a small degree.

Things like this are designed to work in a confined set of parameters of which most of us has already exceeded by orders of magnitude with tuners, injectors big oil and every other possible mod. To notice turbo surge all it takes is a little bit of a tune. To destroy your stock garret, override the PCM defueling and let it boost as far as you can get it. A few WOT's at 24+ if you can get it there should wipe out the thrust bearing or at least get you close.
 
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