Low Boost & High EGT's

[Jobless]

Seem to be having some issues with the twins.

Smarty is on 5 and the TST is on 0.

Unloaded on flat ground it makes about 32psi, 1200 degrees, lots of smoke and is real slow to spool up, this is in 5th & 6th gear and pretty much just flooring it...I could do this with the single HX35 only it would spool a whole lot faster.

While towing about 10k pounds it made 25psi of boost but was at 1250 degrees...6th gear doing 65+mph which puts the RPM's a hair under 2k. this was on the flats and slight inclines between Monroe and Lynnwood and back. I couldn't get any more boost out of it because it would just cause the EGT's to climb higher.

After talking with Pete it seems I had the wastgate set up with no preload, I took it apart and gave it about a 1/4" of preload but it didn't seem to do anything.

I pulled all the cold air pipes and started the truck to ensure that at idle both turbos spin freely, which they do.

When building the HX35 I attached a larger valve to the wastgate so I am starting to think that maybe I had the lever with the flapper valve misaligned just enough to make for a bad seal? I can check this by removing the hotpipe later...

Should I try giving the wastegate more preload before removing the hotpipe and checking the wastegate or is there something else I should be looking at?

Looking for ideas...

Thanks
Brad

Truck specs...
'00 3500 drw 2wd 6sp SO, Jammer 3's, FASS Pump, AFE 4", Smarty, TST PM3, ARP studs, fire-ringed, CON-OFE, CFM+, K&N, HX35/S400

 

[Mudn_1]

boost leak? check the lower intercooler boots thoroughly where the intercooler piping goes in, they are bad about expanding under boost and cutting themselves on the fender! there could be a cut on the top side of them, bend the fender away from them with some pliers

 

[Jobless]

boost leak? check the lower intercooler boots thoroughly where the intercooler piping goes in, they are bad about expanding under boost and cutting themselves on the fender! there could be a cut on the top side of them, bend the fender away from them with some pliers

Checked the boots and the clamps, everything seems to be good. I did see the sheetmetal area you were talking about and clearanced it.

 

[Jobless]

I disconnected the W/G actuator and hardwired it shut...no difference

I hardwired the W/G open...it definately made less boost

I'm still leaning towards the flapper not making a good seal...

I hooked up a drive pressure gauge in the exhasut manifold and a boost guage for the S400.
Making 20psi total boost, 5psi of that was being made by the S400 alone, drive pressure was around 25-30psi. It's pretty hard to monitor as the needle flickers badly, probably needs a snubber like the boost gauge.

It was recommended that I hook up up the shop air compressor to the intake side and check for boost leaks so that next before taking the hotpipe off...

 

[Mudn_1]

yeah, about 10psi should be sufficient for large leaks

 

[Jobless]

Checked the boots and the clamps, everything seems to be good. I did see the sheetmetal area you were talking about and clearanced it.

yeah, about 10psi should be sufficient for large leaks

I found 2 boost leaks...I couldn't get my contraption to hold more than about 15psi w/o blowing off the intake pipe but that was enough to track down a couple.

1. The seal at the output of the HX35 where the 90 degree elbow is. The o-ring is old and compressed and the v-band clamp doesn't look much better. I'll pick up new parts tomorrow.

2. The HX35 has an alignment dowl to orientate the aluminum housing with the bearing assembly. This dowel has to be removed in order to keep the oil inlet and outlet vertical. By removing the dowel it created a gap in the aluminum housing which should be covered by the large snap ring that holds the two pieces together...but it wasn't seated properly either.

I really have no idea if these two small leaks are enough to be causing the overall problem though?

 

[Jobless]

The 1st time I got this setup running I took it over to DDP for tuning the wastegate. The truck hit well over 50psi of boost that day out on the road as we were monitoring drive pressure.

At the time, the HX35 bearing assembly did not have the oil inlet/outlet located vertically due to the alignment dowel between the bearing assembly and housing. I learned that it should be vertical so in order to align it I had to remove the dowel so everything would rotate. This appears to be the start of the boost leak.

I picked up a used, but much newer HX35 from DDP this afternoon and installed the housing on my truck...same exact leak.

After going through "x" number of heat cycles over the years, does the mating surface of the bearing assembly and turbo housing become "matched" due to possible warpage?

And if so, is my only option of fixing this a new HX35? I don't imagine that you can use High-Temp RTV to seal the two together...

 

[Jobless]

After making a few phone calls (cummins/holset) and research on the interent I RTV'd the compressor to the bearing housing and let it cure for 24 hours...

Got home today and pressure tested the system up to 25psi...no leaks.

Wired the wastgate shut again, cleaned the MAP sensor and hit the road. After it warmed up it hit 40psi easily with little to no smoke depending on how heavy footed I was. It definately could have made more but with the w/g wired shut I didn't want to push it.

EGT's never got above 1000 degrees. Got home and re-installed the actuator and set it at about 27psi. Tomorrow I'll go rip it around somemore.

The real test will be loaded up with the trailer attached but it seems to have worked itself out!