need help: twins are acting up

L

liftman

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Jan 1, 2008
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Well, its been a long time since I have been around here but I need some help from the masses.

I've had a set of industrial tow twins 62 over k31 on my truck for a couple years now and they have been run with stock sticks and stock cp3 and a smarty. I could see 58-60 psi (pop off valves on boost tube set at 60 psi) fairly easy with egt's 1200 or lower.

I recently pulled the head to replace the insulation on the firewall so I put in a set of flux 2's, valve springs and studs. I also sent the turbos out to have them rebuilt. And sent the hot pipe and exhaust housings to get ceramic coated.

So heres what concerns me. With the bigger sticks I'm actually seeing less boost and consequently way hotter egt's. The highest boost I can get is 40-45. And egt's are about 8-900 degrees running 70mph at 2050 rpm, and any little throttle input at that speed temps get 1000+ real quick.

I expected to see a jump in egt's but not that high and the boost just creeps up the chargers never light like they did before.

So playing on the dyno we see a max of 22 psi out of the bottom charger no matter what we do. If we pinch off the wastegate on the top charger the primary drops to 12 psi and if we open the top wastegate at 15 psi we still only see 22 psi out of the bottom. And if we pinch off the gate on the bottom still only 22 psi.



What is normally seen with this type of setup? Any suggestions on where to look for problems? Or are we doing something wrong?

Sorry for being so long winded.
 
It's an 04.5 so I set the valves at 10 and 20. I can't see any or hear any boost or exhaust leaks.

How can I check to see if the wastegates are leaking?

What kind of pressure should I be seeing out of the bottom charger?
 
I think something's bad wrong. Running compounds and actually trying to make boost I would expect 100lbs would happen pretty quick.

Do the chargers feel good when you spin them by hand? Hear any strange sounds from them?
 
62/k31 will NEVER make 100lbs.

I would check your ceramic coating on your hot pipe. On the set I built it was just enough to cause a small leak on the v-band connection on the backside of the top charger. No leaks before I coated it but after it did. I knocked the ceramic off with a scotch brite wheel and it sealed right up.
 
SINNER said:
62/k31 will NEVER make 100lbs.

I would check your ceramic coating on your hot pipe. On the set I built it was just enough to cause a small leak on the v-band connection on the backside of the top charger. No leaks before I coated it but after it did. I knocked the ceramic off with a scotch brite wheel and it sealed right up.
Click to expand...

Sorry. With what I would call a small setup running the largest turbine housings made 100lbs would happen at wastegate duty cycles of ~30 - 40% for me. I assumed most other setups would be similar.

I would have thought that 40 - 60psi would be running a set of compounds on cruise control.
 
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Feel great now after they were rebuilt. No strange noises. They still scream just not like they used to and they are very sluggish in building what little boost they do make. They can't clean up a set of don m 100hp injectors.
 
SINNER said:
62/k31 will NEVER make 100lbs.

I would check your ceramic coating on your hot pipe. On the set I built it was just enough to cause a small leak on the v-band connection on the backside of the top charger. No leaks before I coated it but after it did. I knocked the ceramic off with a scotch brite wheel and it sealed right up.
Click to expand...

Good thought but I cleaned that up and the flange from ant overspray. I can't see any exhaust anywhere. Which should be very easy with as black as this thing is running right now.
 
See if your secondary wastegate is closing all the way.... I drilled mine and the flapper got caught up and had similar problems.
 
"62/k31 will NEVER make 100lbs. and live past it"

Prob should have put that part in...LOL

The boost #'s don't seem to run as high on the I6's compared to the V8's. Just like the I6's don't have the insanely high drive pressures like the V engines. Lower air capacity and less rpm's. 1200+ hp has been made with 80-90psi. boost.
 
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