C15 MXS Conversion Issue - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 4 (permalink) Old 10-14-2018, 05:26 AM Thread Starter
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C15 MXS Conversion Issue

Hey guys I'm new here just looking for some help here, i have a 06 peterbilt 379 that has a mxs c15 and i just did a single turbo conversion, i used a borg warner 177148 turbo and a 6nz manifold, i got everything together and it starts and runs Good, has about 80 psi of fuel pressure, the issue I'm having is it only wants to make 20 psi of boost, i had the iva delete done and i backed all of those off and plugged the oil galley that feeds them, also unhooked the iva oil pressure sending unit, i have no check engine lights at all, anyhow it is turned up to about 580-600 now and i know 20 psi boost is to little for that and i have plugged the wastegate, checked cac and boots for leaks, it fuels hard till it hits 20 psi and then just stops fueling, BUT I was driving it around and shifted into the next gear and all of a sudden it had full fuel and made about 38-40 psi in boost but then i shifted again and back to 20 psi it went and i can't get it to full fuel any more than that one time, side note i took the resistors out of the boost wire that i had in there before any help is appreciated, some people have told me to try boost sensors it just threw me in a loop when it did full fuel that one time and made 40 psi any help is so so appreciated

series 60 750 hp
c15 de acert 650hp
blowing smoke and making her choke since 1998
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post #2 of 4 (permalink) Old 10-14-2018, 06:58 AM Thread Starter
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I also have the coolant diverter valve solenoid unplugged if that matters i haven't tried hooking it up to see if that changes anything i will first thing monday

series 60 750 hp
c15 de acert 650hp
blowing smoke and making her choke since 1998
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post #3 of 4 (permalink) Old 11-22-2018, 08:09 PM
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That sounds like an ECM issue to me.
I've done at least 50 of those on the pretty same way as you did.
Replaced the turbo and manifold, and backed the vvas off.

I recommend that you visit the web site of a guy that does my tunes https://truckecmtunes.com/
They are expensive compared to some other solutions, but they sure are worth it.

PS. Maybe try to plug everything back in (talking about electrical connectors) - maybe it will help.
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post #4 of 4 (permalink) Old 12-19-2018, 12:56 PM
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ILoveDetroits fuel pressure should be higher. 105 psi at 1700 rpm. Replace fuel pump change/shim fuel pressure regulator. A guy wanted me to turn his MXS up 50 HP. We needs to make sure he had air and fuel first. He had 80 psi. Upped it to 105 and his hp came back. Gained 1/2 gear in the hills loaded. I'd check for boost leaks. On 75% of the trucks I see I find a leak. Windex bottle with soapy water. Every intercooler boot and tanks on intercooler. A ScangaugeD is useful for monitoring things and they are inexpensive.

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