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I know this topic has been discussed many times and I am likely going to get some "use the search function" responses but here goes...
Took my 03 X50 out for a ride tonight and started monitoring the boost gauge. It was 52 deg F. outside and I was making 0.7 bar on a couple of 3rd and 4th gear runs. Cause for concern?? The car has 24K laps on her and no engine lights. Just watched 10 videos about chasing boost leaks and would welcome a little feedback before going down that rabbit hole.
Thanks for the quick reply. Guess I set up for the full test utilizing the outlets of the turbos? I have a 4 post lift so that is not an issue for me. Seems to be a ton of attention regarding check valves and the infamous #16. Please don't tell me these engines are that susceptible to tiny plastic parts.
You can pressure test at the airbox inlet, the turbo inlets, or the intertercooler inlets... Intercooler inlets work best as you won't be chasing phantom leaks through the turbo oiling system.
My engine made full boost on the gauge, but still had leaks including #16 and one of the small check valves. Acceleration is now a complete kick in the *** once I got all the little boost leaks addressed!
Yes, the Turbo's are susceptible to tiny plastic parts and rubber hoses failing. But oh so worth going through and addressing the small and large leaks.
Here is the boost leak tester I made. Parts came from McMaster Carr & the PVC cap came from Home Depot. I plugged this into the hose coming off of the turbos. I found bad diverters and a crack in the f pipe.
Blowing off the test fittings is a real issue... A metal fitting with some sort of ridge or lip is ideal, but I found that wrapping my PVC fittings in a couple of layers of a heavy, textured duct tape (I think I used gorilla tape) allowed them to be clamped securely into the hoses. Slick PVC will definitely have a tendency to blow off at higher pressures.
i use a 3" to 2.5" silicone reducer and attach at the i/c on both sides. compressed air thru d/s and p/s is simply blocked off. i test to 35 psi since my boost can run that high. you will see leaks at above 20 psi that you never see below that setting
Ok fabbed up a test rig this morning and just performed the test. Pulled the outlet hoses off of the turbos and attached two plugs. Pressurized up to 22 lbs and don't hear or see a thing. The pressure drops down to 15 within 3-4 minutes but I wouldn't expect it to hold tight forever. Does that leak-down rate seem reasonable or should I spray everything down looking for a leak
Pressure test sounds pretty good to me... How much does it drop in the first 30 seconds or so?
Also, make sure your N75 valve is hooked up and operating correctly... If you don't have any boost leaks, a disconnected or defective N75 might explain your low boost.
If N75 was unplugged or inoperative it wouldn't show as a boost leak, but your turbos would be dumping pressure at the pre-set waste-gate spring pressure instead of being controlled by the ECU. This is kind of a fail-safe mode.
The N75 valve when operating correctly is controlled by the ECU, "tricks" the turbos into producing more boost than the pre-set wastegate pressure by switching/sending non-pressurized air to the wastegate control port instead of boosted air keeping the wastegate closed even when the boost exceeds the wastegate crack pressure.
Blue: Air path into N75 Valve from Y-pipe. Boosted Air. Default flow-through if N75 is disconnected
Orange: Un-boosted air path into N75 valve. Picked up from dump side of diverter valves. Unpressurized. Routed through N75 valve when 12V is pulsed to switch.
Green: Output path of N75 valve routed to turbo wastegates. By default, (N75 off by ECU, disconnected, or stuck/broken) it is BOOSTED blue path. When 12v is cycled on, it is UNBOOSTED green path. This allows the turbos to make more boost than the default, mechanical wategate spring pressure.
Very minimal leakage if you could track it down at all... Not your problem if you are only making .7 bar.
See above, I'd definitely check out your N75 valve, particularly if the electrical connector is on and fully seated. It is under your y pipe, just under where the fuel cooler is. A bit hard to see with the y pipe installed, but possible to get a glimpse without taking off the y pipe.
05-18-2018, 11:08 PM
x50 Boost 0.7???
