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  1. #1

    Join Date
    Oct 2013
    Brisbane, Australia

    MSX150 won't rev past 4400

    Hi guys,
    I've put together a few boxes of parts and now I have a MSX-150. First test in the water was encouraging as I wasn't convinced that it would work at all!! So everything seems to be working but it just won't rev past 4400rpm. There is no oil in the intake system, no check engine light, throttle opens to 100% and I can't seem to find a solution. Any ideas????

  2. #2
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Haha... a few boxes of parts. Nice! and congrats... that's no small feat.

    So what was your solution for the blown turbo? What do you got in it now? Same stock size turbo?

    So max of 4400 RPM... every time? Did it surge really good the first time you punched it... then seemed to dial it back all the other times? 4400 is close to the known overboost RPM limiting max of 4700-4800. So if you overboosted it, the ECU would dial it back to a max of 4800 (what I've seen). But this also comes with a flashing red warning light.

    I would hook up a boost gauge to see what you're reaching for sure. Tee into the small hoses going to the BOV or to the wastegate. Then take a spin and see what your max sustained boost is. Should max at 14-15psi (1 bar) at 7250-ish RPMs. So if you don't get that high in RPMs... might not see max boost.

    Another way to "test" turbo is giving you good boost (and that you are having a possible ECU boost control issue... usually the boost value/wastegate solenoid)... unplug the line from wastegate solenoid to the wastegate. This will give you max turbo boost and should trigger an overboost condition where the ECU steps in and brings back RPMs to a 4800 max (limp mode). This will reset after turning engine off then back on... so no worries. I wouldn't do it repeatedly... but once will confirm you can reach that high boost and that the ECU steps in (overboost... plus warning light)... then plumb the hose back up correctly again and restart the engine.

    If you reach max boost in above "test"... but when plumbed back correctly you can only reach 4400... I would suspect a bad wastegate solenoid. If the wastegate solenoid is bad, it can likely stick in the non-powered state where it send all boost all the time to the wastegate. This give you a max of 6psi and no check engine lights. This amount of boost will only get you up to around 5300 RPMs max (in my experience). While higher than your 4400 stuck limit... might be related.

    Do you have the old wastegate solenoid (mounted on side of turbo intake)... or newer style (mounted on bracket off valve cover)? Old style one was known to fail.

    Another thing to check... the BOV. Make sure you have a boost line connected to it... or it'll lift off it's seat when boost pressure overcomes the springs pressure (need boost pressure on backside of diaphragm to keep it seated) and bleed off boost. Less boost... less power... less RPMs and speed.


  3. #3

    Join Date
    Oct 2013
    Brisbane, Australia
    Thanks for the reply,

    I did a bit of research about the turbo and eventually worked out that it was very similar to the audi a4 1.8t turbo. They're both KKK K03 turbo's and the exhaust side is identical but the Audi has a larger compressor impeller. I bought a replacement turbo cartridge from China for USD196 delivered and used my original plate and compressor wheel with the new shaft, bushes, exhaust side etc. A lot better than shelling out for a genuine replacement that's for sure!

    It was 4400 exactly every time. No surge and now you've got me thinking about my turbo fix..... I guess I figured it would be something tricky or computer related because it was 4400rpm every time but I suppose it's possible that either boosted air or exhaust gases might be escaping somewhere. I didn't replace any of the vacuum lines and I ended up drilling out a grease nipple and using it in place of the banjo fitting on the compressor housing. A bit dodgy I know but it seals.

    I have the new style solenoid but I haven't bench tested it yet. For some reason I was very negative about this project and I didn't expect it to work at all so I've probably cut a few too many corners. The fact that it actually works(ish) has reinvigorated my resolve so yesterday I started pulling it all apart again with a view to do it all properly. First things first, I'll check that solenoid.

    Thanks again for your help. I literally would not have gotten this far without it!

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