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I figured I would ask here since its LNF K04 related.
I have a K04 from the LNF installed on my L61. I am running a standalone ECU. I am using the wastegate without the controller, just the 7psi mechanical opening. I am using the BPV without the computer control, running vacuum right off the manifold.
I am experiencing a case where I have compressor surge at a part throttle condition. At roughly 25% throttle, 2500 RPM, 5 psi of boost I am getting compressor surge. I understand this is most likely because the throttle is open so little.
What can I do to eliminate this surge? I assume the LNF doesn't experience this at these parameters, what is the difference?
My map sensor shows 5 psi of positive pressure at this point.
I am using the stock wastegate. If I extend the rod, that should lower boost, correct? What kind of decrease should there be available?
And if I drop the boost to prevent surge at this RPM/throttle then I won't make any more boost anywhere else, without using a boost controller?
the wording "Compressor Surge" is a very specific behavior. It means you are building too much pressure (boost) for the air flow that you are moving through the engine. This messes with the air flow physics of the compressor and you start getting air flow oscillations back and forth through the compressor. Surge is bad, and it can even damage the turbo.
From what you describe, i highly doubt what you are experiencing is surge. it might be blow off valve flutter, but not surge.
with your standalone controller, can you measure air flow? you would have to flow less than 3 lb/min at that 5psi for you to experience surge, seems unlikely.
i think you have blow off valve flutter or something else. Describe your setup and problem more accurately and maybe well be able to help. As of right now i think there's something going on with your BOV / BPV, however u have that system set up.
To me it sounded like what I've read is the sound surge makes. It sounded like the turbo was being quickly stopped.
I do not have the ability to measure air flow, its a speed density setup.
Its the stock K04, with the stock WG, the stock BPV. The stock WG is connected in the stock fashion through the valve, but the valve is not electrically connected at this time. The stock K04 bypass valve is connected directly to manifold vacuum, no vacuum storage tank or valve like the LNF has. I know the BPV is working at least somewhat because it is bypassing on throttle close.
The setup has a much higher flowing exhaust and intake system than the LNF, as its all custom made.
Isn't surge an indication of a turbo that is too big for the motor? Does the LNF ecm use that vacuum storage tank to have vacuum available to partially open the BPV in the low RPM with boost areas to prevent surge?
No.
Car runs like stock with it removed.
Cam profile and electronic BPV and wastegate solenoid make sure the k04 isn't surging on the lnf.
I have 2" coming off the turbo, changing to 2.5" at the intercooler. And then stepping to 2.75" at the throttle body.
You can see the short runs in the photo below.
Take some tension off of the wastegate rod. Loosen the nuts like 1 turn. See if that fixes it.
You have no electronic control and a boost controller is not going to be the asnwer
Do this. You're most likely taking the turbo above the surge line, to high of a pressure ratio for the air flow, drop the preload and the pressure ratio should drop a little and that may keep you under the surge line.
I'm still staying by my previous statement, I don't think this is surge. Unless you have some other hardware problem that is making a LOT of flow restriction, like a clogged intercooler, forgot a rag in the plumbing, something weird like that. I still think you're BPV might be opening, but i don't know why.
The stock BPV on the K04 runs just fine directly to manifold. He is making 5psi at 2500rpm at 25% throttle, he needs to adjust his wastegate; it is too tight.
OP,
just for ***** and giggles try using BorgWarner MatchBot (google it) and make some educated guesses of your system and you'll see that your 2.2 engine flows more air at 5 PSI, 2500rpm than what would cause surge at 5 PSI.
Although the matbot doesn't have a turbo as small as the K04 it'll give you an idea of how much air your engine flows, then look at a K04 compressor map and you'll see that you are not in the surge region.
Hell i can push more than 15 PSI on the LNF at 2500 RPM and it still doesn't hit surge.
OP,
just for ***** and giggles try using BorgWarner MatchBot (google it) and make some educated guesses of your system and you'll see that your 2.2 engine flows more air at 5 PSI, 2500rpm than what would cause surge at 5 PSI.
Although the matbot doesn't have a turbo as small as the K04 it'll give you an idea of how much air your engine flows, then look at a K04 compressor map and you'll see that you are not in the surge region.
Hell i can push more than 15 PSI on the LNF at 2500 RPM and it still doesn't hit surge.
edit: I was agreeing with this, and then realized the OP is hitting surge at part throttle. Part throttle is a major restriction by definition, so it might all be in the tuning as others have pointed out.
OP,
just for ***** and giggles try using BorgWarner MatchBot (google it) and make some educated guesses of your system and you'll see that your 2.2 engine flows more air at 5 PSI, 2500rpm than what would cause surge at 5 PSI.
Although the matbot doesn't have a turbo as small as the K04 it'll give you an idea of how much air your engine flows, then look at a K04 compressor map and you'll see that you are not in the surge region.
Hell i can push more than 15 PSI on the LNF at 2500 RPM and it still doesn't hit surge.
Yes it can, all turbos can surge at low boost. Given its a part throttle not full throttle the throttle blade is limiting the airflow, he's seeing 5psi on the map sensor so post throttle body, but unless he has a boost tap pre throttle body we actually don't know what PR he's at. Here is the compressor map for the k04 or the closest compressor map Stamina could find.
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