[96GMC6.5L]

I wired the wastegate shut expecting to see if my vac system is bad or not. I was expecting to see atleast 10-15psi of boost by doing this, but it only got about one pound above what it gets with the wastegate not wired shut.

I am confused now.

Please Help!!

Thanks, Jacob

 

[Chicago TDP]

did u wire it wrong?

 

[Turbine Doc]

I think you must have wired it open, normally full vac pulls the actuating rod all way into the actuator can so wire it to same way as if the vac was requesting full boost.

Remember in functional vac system WG is always in closed position (full vac) unless PCM is seeing too much boost for the programmed curve, at which point WG solenoid goes to vent mode lessening vac applied to can allowing WG to go more open ergo less boost.

 

[dieselboy28]

when wiring it shut you want to pull the lever towards the vacuum canister.

i caution you to be very careful when wiring shut. when i did this, before i knew what i was doing and listening to someone that thought they knew 6.5s but didnt, i could easily hit 21 pounds boost

 

[Dan Hunter]

when wiring it shut you want to pull the lever towards the vacuum canister.

i caution you to be very careful when wiring shut. when i did this, before i knew what i was doing and listening to someone that thought they knew 6.5s but didnt, i could easily hit 21 pounds boost

Worthy of a sticky! I've been guilty of passing on bad info and have throttled back in postings. When I've been flat wrong, I've tried to acknowledge it in the thread. The moderators to a fine job balancing courtesy and "truth" control. Again, gauges first and a knowledge of what you're looking for is the best insurance.

 

[dieselboy28]

ill never make another mod to a truck until ive researched it. he still has the nerv to say "ya he shouldnt have wired that wastegate shut" after he told me in the first place "just wire it shut, ive done it and it works great, no bad effects "

 

[96GMC6.5L]

That is how I wired it, I put the wire behind the wastegate, pulled it up as tight as I could, and twisted it behind the canister and bracket so it would hold. The rod was as far into the canister as I could get it. That is what I do not understand why boost did not sky rocket. Any thoughts?

Thanks, Jacob

 

[Turbine Doc]

Exhaust leak, see pics of leaky cross over, boost/intake leaks, or turbo issues itself (WG flapper stuck or erroded most probable, compressor wheel eat up mext possibility)

Send us a pic of the wired shut WG, if not full seated it will loose boost

 

[96GMC6.5L]

How do you know if you have an exhaust leak? If I do it is deffinately in the x-over, or downpipe because from the cat back is almost mint.

Thanks, Jacob

 

[Dave12]

You would have to look and listen. If you had a S engine you would probably be getting EGR and MAF codes.

My x-over pipe cracked in the summer. Prior to it finally giving out I was throwing EGR and MAF codes. Just before it cracked I could hear the leak around the drivers side. Once it cracked it threw turbo codes. The unfortunate thing is I didn't have my boost gauge hooked up at the time or I would have known if I was loosing boost prior to it totally crapping out. If you're getting higher than expected EGTs, this could be the cause also.

Dave

 

[Turbine Doc]

Crawl under the truck and look for bad pipe, or start your truck, plug exhaust partially, a assistant's hand over cold tail pipe, or heat resistant gloved hand will do and listen for leak. Also Dan Hunter's call on plugged cat in the other thread is a good one.

 

[Scrufdog]

keep in mind the wire needs to be strong and tight. The pressure of the exhaust is probably more than you think once you start hitting boost. The littlest bit of stretch will make you loose boost.

 

[96GMC6.5L]

What has to be strong and tight, the tube going from the boost gauge to the plenum?

Thanks, Jacob

 

[Scrufdog]

the wire thats holding the wastegate shut

 

[96GMC6.5L]

I thought I had it pretty tight. Would it being a little loose cause it to only get to 5. Seems like even with it loose it would still get up there pretty good, better than with the vac system, but maybe not.

Thanks, Jacob

 

[Scrufdog]

yeah, only takes a pinch....

refer to this thread to see the little bit of wastegate movement it takes to loose boost. When I get off the throttle you see the spring move just a bit, thats all it takes.

http://dieselplace.com/forum/showthread.php?t=126580

 

[96GMC6.5L]

Would not using teflon on my boost gauge fittings effect anything. I figured it was pipe thread, and I tighened them well so I don't think it would matter, but look at what is happening now. I can try wiring it again real tight. The gauge was a little more responsive with the gate wired shut. At 50mph I was at like 2-3psi when with the regular vac system at 50mps the gauge doesn't even pick up. So maybe I didn't do it tight enough. How are you supposed to wire it? I took a stiff piece of wire and passed it behind the arm and the wastegate and brough both ends up behind the canister and twisted them there.



Thanks, Jacob

 

[Turbine Doc]

If there is any movement at all WG will open and boost will be lower or non existant, gauge fittings should be compression metal to metal fittings with a ferrule that crimps into your gauge line, so teflon tape or paste will actually do more harm than good,

 

[cool_fool]

I would bet that your soot trap is plugged or close to it. BTW, the wastegate arm only has to move 1/16th of an inch to dump almost all exhaust pressure.

 

[Dave12]

My truck boosts up MUCH easier since installing my 4" exhaust (no soot trap). When I looked through the soot trap after it was off, I could only see a spot of light about the size of a dime.

Dave