Overboost or Detonation (or both)?

[MAK]

I installed my RPM CAI and vac line kit today. All went well. After the install I took her for a quick ride to make sure nothing was wrong. The idle is near perfect now and she runs like a top. I have been taking it easy on her because of a possible detonation issue but I figured a 3/4 throttle blast would not hurt. When I pressed the accelerator it took off but the boost needle blew WAY past the 15 psi on the stock gauge. This is a first. After I let off the throttle (immediately) there was a LOUD noise coming from the turbo. It did this the last time under hard acceleration also. It runs fine other than the loud "bang-whoosh-thud".....:lol:

For reference, the truck is all stock except for the CAI and a Thermomaster (I think) chip my dad was talked into buying several years ago. It has a new(er) stock turbo and stock exhaust.

Does anyone have even a hint at what this might be? I did a search but found nothing resembling these symptoms. I know it is almost impossible to understand what I am describing unless you hear it for yourself. I figured I would ask anyway.

Any help would be much appreciated.

 

[SyTyAddict]

Re: Overboost or Detonation (or both)?

The noise that you hear after you let off is probably the boost pressure venting back through the compressor, the tend to do this if they run a cai without a bov. The stock boost gauge also has terrible accuracy, you need to have a decent mechanical gauge. You need to hook it up to a scan tool to check for knock, be careful knock seems to kill a lot of these motors.

 

[MAK]

Re: Overboost or Detonation (or both)?

SYTYADDICT - It did this before I installed the CAI. Also, the boost pressure never went this high before today. I know my boost solenoid looks pretty rough. Could this have something to do with it? The wires going to the solenoid are also in bad shape. NONOVA0074 posted a picture of a BOV on athother post...I think it was a hint.....:tup: I have heard the gauges are not very accurate and will be getting at least a boost and oil pressure gauge. Knock also scares me.

My wife is going to divorce me over truck parts. I can see it now.....:rant:

 

[elorejas]

Re: Overboost or Detonation (or both)?

i think its louder know that you have a shorter air intake tube thats why its louder before when you had the factory intake it silenced it since it was a long way before the noise came out and know its an open filter besides the enclosed factory box thats just my guess?

 

[neildemo]

Re: Overboost or Detonation (or both)?

check your hoses near the boost solenoid I had similar problems. Once I fixed it Ran fine. Lucky I didnt blow my motor. After that thought I couldnt get 15psi so I installed boostvalve. and it fixed this problem runinng e85 with 19psi. Ty Runs great.

 

[elorejas]

Re: Overboost or Detonation (or both)?

because my trucks factory intake tube came loose from the elbow and you could hear the turbo louder than when everything installed

 

[MAK]

Re: Overboost or Detonation (or both)?

NEILDEMO - I had just replaced all of the vacuum lines including the boost solenoid so I know they were tight. There are two nipples on one end of the solenoid - one having nothing attached and the other going to the wastegate. the end with one nipple goes to the turbo. I don't even know if this is correct, as they were that way when I got it back from the mechanic.

Picture would be here if I could make it work

 

[SyTyAddict]

Re: Overboost or Detonation (or both)?

Here's a pic, make sure there is not a hose on the vent port.

 

[nonova0074]

Re: Overboost or Detonation (or both)?

they ,make that noise my bov just went bad and i hear it again make sure you install a bov

 

[gstacky]

Re: Overboost or Detonation (or both)?

Make sure your turbo wastegate rod moves, they tend to seize and overboost, reach in through the right inner fender, grab the rod and pull back towards the firewall.

 

[MAK]

Re: Overboost or Detonation (or both)?

Here's a pic, make sure there is not a hose on the vent port.

My vac line was on the vent hose (the nipple with the "claw" on it). The mechanic in NC put it there so I assumed it was correct. Thank you for the picture. Now I know how the solenoid bracket mounts.

I will also add a blow-off valve to the wish list.

 

[SyTyAddict]

Re: Overboost or Detonation (or both)?

No problem, I'm glad you figured it out. I'd still put a scan tool on it before you really run it hard, if you have a laptop already, you'll just have to get a cable to connect to the aldl port and tunerpro (free, but you can donate).

 

[MAK]

Re: Overboost or Detonation (or both)?

SYTYADDICT - I am taking it to a mechanic next week to have it tuned so I will make sure he checks everything. What symptoms would show up with the vent hose running to the turbo instead of the proper hose (coming off the boost solenoid)? Could this cause the overboost or detonation?

 

[SyTyAddict]

Re: Overboost or Detonation (or both)?

I would think that that the wastegate wouldn't open with it on the wrong port, which will cause it to overboost and boost spike, and that will definitely result in knock.

 

[MAK]

Re: Overboost or Detonation (or both)?

I switched them out and will check to make sure the rod on the wastegate moves freely. I will be thrilled if the fix for the truck is as simple as this.

 

[Scubanme]

Re: Overboost or Detonation (or both)?

The noise that you hear after you let off is probably the boost pressure venting back through the compressor, the tend to do this if they run a cai without a bov. The stock boost gauge also has terrible accuracy, you need to have a decent mechanical gauge. You need to hook it up to a scan tool to check for knock, be careful knock seems to kill a lot of these motors.

Where do people normally make the BOV install?

Thanks

 

[wildphil]

Re: Overboost or Detonation (or both)?

If I am reading your posts correctly. I think you have the vaccum hose on the wrong nipple. On the side with two nipples. The vaccum nose goes on the nipple that DOES NOT have the claw. Origionaly the nipple with the claw had a little foam filter on it. On most trucks this filter is missing. It doesn't hurt anything.

 

[MAK]

Re: Overboost or Detonation (or both)?

If I am reading your posts correctly. I think you have the vaccum hose on the wrong nipple. On the side with two nipples. The vaccum nose goes on the nipple that DOES NOT have the claw. Origionaly the nipple with the claw had a little foam filter on it. On most trucks this filter is missing. It doesn't hurt anything.

It was connected to the nipple with the "claw" on it. I switched them out and will drive it to work to see how she does. The last mechanic had it on the wrong one and I just assumed it was correct. Hopefully the loud noises will all go away. Thanks for the info.

 

[MAK]

Re: Overboost or Detonation (or both)?

Swapping the hose did not correct the overboost issue as I hoped it would. I gave it about 3/4 throttle again and the boost gauge pegged VERY quickly. I let off the pedal and got a loud sound - but a better sound - the typical turbo/wastegate shudder during deceleration, not the loud bang as before. This is a start in the right direction (I think). I am just about stumped on the overboost issue. These turbos are new to me and are going to take some time to figure out. Thank goodness this forum is here.

 

[BMFB]

Re: Overboost or Detonation (or both)?

Where do people normally make the BOV install?

Thanks

http://www.syty.net/forums/showthread.php?t=80764

This is what I did, I have since moved on to better couplers (Vibrant) and clamps (breeze constant torque) because I kept blowing the HD ones apart.

I don't like the sound of your goofy chip, just for giggles, you could take the vacuum hose straight off of the turbo and put it directly onto the wastegate solenoid. This will open the gate up right off the bat, and give you the least amount of boost that the turbo can make. This will at least let you know if its the solenoid, or if you have some other problem. I would only recommend this after you make sure that the gate is not frozen, and that the actuator does not leak vacuum.