I think I have just experienced my first turbo stall/surge. I just put e fuel and a t500 on my 95 with 160/30 sticks and in my 80e tune I was pushing it pretty hard and the boost gauge hit about 35 and then just fell off all a sudden to 15-20 so I let off it. A few mins later I Layed on it but not as hard and this time it it 35 then fell off to 30. Is this what surge or stall is?

 

Is about the upper limit of what is ok for the turbo. Start overspeeding it and the bearings won't be happy.

Surge is definitive when it happens. Its kind of hard to explain, but you can feel the turbo "fluttering"

Throwing any codes?

 

No codes and I know 35 psi I a lot just wanted to see if the t500 made a difference and I see it did. I just didn't think the obs turbos did this

 

They don't have the turbo surge, like the SD trucks, which is why the turbo wheel from OBS is used on the SD trucks to cure the surge.
Any idea what your drive pressure is?

Wonder if you are maybe driving the turbo outside its map.

 

I'll try and get a reading on the drive pressure

 

you overboosting, not surging.

our turbo's only made to go 30psi.

Turbo surge is weird. I cannot quite explain it.

You'll have to essentially choke out the air filter on our trucks to get them to surge.

I suggest pulling air stuff and checking your turbo.

if the bearings are wobbled out or its out of balance, it will do that.

Or if your air filter is old as hell. That might be your issue.

It' doesn't really just drop boost. You'll hear the turbo make a really crazy noise if your paying attention to it.

Surge is when the turbo runs out of air to suck.
You are more likely to spin it out and destroy it before you are to get surge. on ours anyways.

Like mentioned earlier in the thread.
SD's fix was to put a less aggressive wheel in, which is the OBS wheel.

 

Turbo surge on these trucks can only occur during a quick transition from high engine load (wide open throttle) to low engine load (so-called TIP Out). Essentially, the turbo cannot unspool fast enough to deal with the drop in air flow through it. Because it must unspool, it basically "jumps" down the unspooled level rather than smoothly slowing down. This jumping causes the turbo to make a chugging noise (to me it sounds a little like a steam locomotive going really fast). Driving a long nice and steady would never cause surge.

 

BTW, dug this up:




Pressure ratio of 3 = 30 psi of boost. That's as far as she goes for sure. And, you don't have much room up there it looks like.

 

Yeah, thats the noise!

I have not had it happen in a long time.
I really needed to change the 6637 out when i had it happen.

 

I never thought it would over spin it with stage 1s and not the most aggressive tune. Wonder how much the riff raff or dieselsite wheel would help

 

like I said,
if you are actually surging a stock turbo with stage 1's, you got air problems.

Surge is from lack of air getting to turbo.
So it over spins because there is no back pressure.

 

Not to hijack your thread but I'm having a similar issues on a 04 F-350 at work. I'm thinking this might be whats happening to it. Granted there are no gauges on the truck to be able to tell. But when your hard on it it'll just fall out and sound like a (cha-cha-cha-cha-cha)

So it sounds like the best thing to do is change the air filter first? IDK when the last time the filter has been changed on this truck.

 

Stall/surge can happen to any turbine. Ours are not very suceptable to it. As a simplification of the below definition, it's a 'stall' or reversal of airflow through a turbine caused by too high a pressure differential over/through the turbine.
This can be caused by too low a suction pressure (plugged filter, etc as mentioned before), and/or too high a discharge pressure which could be caused by a sharp drop off in demand (Rapid drop in RPM) from the motor under heavy load.
Not an issue with stock OBS trucks. That's why the engineers didn't put a waste gate on the housings.

Axi-symmetric stall, more commonly known as compressor surge; or pressure surge, is a complete breakdown in compression resulting in a reversal of flow and the violent expulsion of previously compressed air out through the engine intake, due to the compressor's inability to continue working against the already-compressed air behind it. The compressor either experiences conditions which exceed the limit of its pressure rise capabilities or is highly loaded such that it does not have the capacity to absorb a momentary disturbance, creating a rotational stall which can propagate in less than a second to include the entire compressor.
The compressor will recover to normal flow once the http://en.wikipedia.org/wiki/Integrated_Engine_Pressure_Ratio reduces to a level at which the compressor is capable of sustaining stable airflow. If, however, the conditions that induced the stall remain, the return of stable airflow will reproduce the conditions at the time of surge and the process will repeat.<SUP id=cite_ref-Kerre261_1-0 class=reference>http://en.wikipedia.org/wiki/Compressor_stall#cite_note-Kerre261-1</SUP> Such a "locked-in" or self-reproducing stall is particularly dangerous, with very high levels of vibration causing accelerated engine wear and possible damage, even the total destruction of the engine.