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Turbo redblock compressor surge

Hey guys. I have had this ongoing issue since upgrading turbos.

So firstly, car is a 1990 240 with b230ft from a early 940.
10,000km ago I swapped the 13c turbo over for a .48 a/r 50 trim (allegedly) t3/t4 unit off ebay for something like $150. I only wanted to try it out so I could see how it feels and upgrade down the track to a decent unit.
During that time I have been getting compressor surge at 25-50% throttle under load, for example cruising up hill.
I swapped out the T camshaft for a K with adj. cam gear, thinking it might help the 530 head breathe better but it didnt effect the compressor surge.

So friday night I fitted a slightly different sized turbo. It has a physically smaller compressor housing to the old t3/t4 and supposedly a .63 a/r hotside. Specs looked better than the $150 unit. BUT now im getting compressor surge pretty much from 1-2psi half throttle or full throttle. It doesnt discriminate. I had the MBC set to 15psi bit It wont reach that level of boost.

I unplugged the MBC and It seems to have helped the surge somewhat.

WHAT the **** is going on? I see guys on the social media running big holsets etc slapped onto a junkyard redblocks with apparently no issues in boosting, or is it all just for their Instagram fans?

Specs of current turbo:

Compressor;
a/r .60
inducer 54.3mm, exducer 71mm

Turbine:
a/r .63
inducer 65.2mm, exducer 56.00mm

Car specs:
3" full exhaust, k cam, 2.5" intercooler piping, big intercooler, lh2.4 chips of ebay from some dude in sweden, modded aw71, ported 90+ mani

Is my turbo not sized correctly? Are my dodgy chips messing something up? what am I missing?

Any help or insight would be greatly appreciated. Thank you!

Comments

  • Some of those lh2.4 chips can be hit and miss did you get any specs of what the chips were tuned for eg:injectors,maf?
    Its not really possible to get true compressor surge at such low boost its possibly an ignition timing/fuel issue?
    Spac
  • 240wagsEric (@240wags) Forth, Tasmania
    I'm hoping that's what the issue is. Chip is for "stage 3" tune. 3" maf (which I'm currently running), intercooler, 3.8 bar fpr, bigger turbo and bosch 440cc injectors.

    I had the green injectors installed on the previous turbo but I was running very rich at high boost and revs. So I dropped down to 850 injectors.

    I feel like I've never been happy with the chips. The car has never felt right. I have also developed a stall decel and stopping at lights etc. The stalling has become 100% worse since fitting the new turbo as well
  • Dumb question..
    The 13c had a built in bypass valve
    Did you plumb a new one into the system after adding the new turbo which I would assume does not have a bypass valve
    Vee_Que
  • I'm hoping that's what the issue is. Chip is for "stage 3" tune. 3" maf (which I'm currently running), intercooler, 3.8 bar fpr, bigger turbo and bosch 440cc injectors.

    I had the green injectors installed on the previous turbo but I was running very rich at high boost and revs. So I dropped down to 850 injectors.

    I feel like I've never been happy with the chips. The car has never felt right. I have also developed a stall decel and stopping at lights etc. The stalling has become 100% worse since fitting the new turbo as well

    Running narrowband o2 or wideband with narrowband output to lh2.4

    Also, r the injectors low or high impedance?
    Vee_Que
  • 240wagsEric (@240wags) Forth, Tasmania
    Yep. So first I tried a turbosmart atmospheric bov but LH hated that and kept stalling.

    I have been using a GFB 25mm recirc valve with soft spring pressure.
  • 240wagsEric (@240wags) Forth, Tasmania
    Running high impendence with resistor pack removed. Wideband for the aem gauge and standard factory LH sensor in oem location.



    *This evening I swapped over to standard turbo ecu and ezk without the chips. No difference. It did momentarily drive great with no stalling until the LH started to learn and reverted back to stalling
  • Running high impendence with resistor pack removed. Wideband for the aem gauge and standard factory LH sensor in oem location.



    *This evening I swapped over to standard turbo ecu and ezk without the chips. No difference. It did momentarily drive great with no stalling until the LH started to learn and reverted back to stalling

    Why not use the narrowband output from the arm sensor direct into lh2.4?
  • 240wagsEric (@240wags) Forth, Tasmania
    To be honest I didn't even realise you could do that. The o2 sensor is is relatively new.

    Wondering if the amm could cause compressor surge?
  • Wondering if the amm could cause compressor surge?

    I don't think so as air would flow easily back and forth through it. Where is the MAF in the system? Before the turbo or between the intercooler and thrttle body?

    Have you looked for boost leaks?
  • 240wagsEric (@240wags) Forth, Tasmania
    I have kept the location of the MAF as close as standard location, before the turbo.

    I have checked for boost leaks many times but it's all good. The vacuum port on the manifold for the bov is pretty small. I'll sort out a larger port with larger diameter vacuum line in the next few days and see if that changes anything.
  • You could try running with maf unplugged and see if it still surges.
    What maf are you running?
  • 240wagsEric (@240wags) Forth, Tasmania
    It runs rough unplugged but I haven't tried it on a drive. It's a 012 maf
  • volvodrivermanvolvodriverman (@volvodriverman) Barringwood Estate, Tasmania
    Try putting everything back to stock & seeing if it behaves? If it does then you can add in one mod at a time & see where it goes wiggidy.
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