Alpine951

I have been recently trying to figure out a lower than expected boost issue this past week. My cycling valve is removed and bypassed. I am trying to determne if I can make 15 psi without any boost controller. The pupose is to see if my k26/6 can make 15 psi in high rpms. I use a reliaboost that feeds off the intercooler pipe. The outlet side of the rboost then goes straight to my single port wastegate. I disconnected the Rboost and plugged up the line coming off the intercooler pipe. I am trying to modulate the gas pedal so I don't overboost during this test. All of a sudden when i try this test Ihear this sound which my first fear was detonation, but I'm not sure. It happens on boost when I hit 15 psi. When I am driving the car it sounds like its on the left side of the engine. Its either the rattling can sound or its a Pshhhtt like some air leak, but I can't really tell. When detonation occurs can the sound be heard from a specific part of the engine bay while driving? I think I am going to run out and throw some toluene in just in case.

Alpine951

Lots of views here but no responses yet. bummer. The reason for my question is because I'm not sure if its detonation. I remeber back in the 70's hearing detonation on cars. It was load and sounded like a diesel engine. The sound I hear in my car is much quieter. By the way i just put in a gallon of xylene to a half tank it it still made the sound.

Danno

Typically you hear the popcorn-kernel-in-coffee-can sounds of knock/detonation coming from the right side (exhaust) side of the engine. I guess it comes out the exhaust-ports since that's the valve that opens up next.

If you're hearing fluttering phhhssttt sounds from the left side of the engine, that could be the compressor-bypass valve that's leaking. Also could be the outlet of the J-boot which gets really brittle over time and tends to crack (probably due to heat from the turbo).

Also check on the back side of the large hose at the turbo-outlet. That tends to get brittle with age and splits underneath the bend in the elbow where you can't see it. Have to grab the hose and feel around the back side. Also make sure the hose-clamps on both ends are tight. I double-up on the hose-clamps here to be sure (2 clamps per end of hose).

Alpine951

Danno,

so you don't think its detonation. I sent you an email . I just installed the Evolution Motorsports Diverter valve a month ago. do you test this the same way as the stock one. You know, by sucking and blowing?

Alpine951

The j boot is on the non compressed side of the intake. Does the pressure in the j boot increase on boost?

Danno

No, pressure doesn't increase, but a cracked J-boot will cause you to suck in air there and cause a hissing sucking sound. Also this air is unmetered since it's after the AFM and will result in lean mixtures. Thus may be a contributing factor to the knock and detonation you may be experiencing.