BigJohnston

As you can see by my sig I have plenty of power and fuel to make big boost but 38 is all I can get. I have a Quad Commander and an Auto meter analog boost gauge and they both read similar. The analog seems more responsive and shows boost earlier and slightly more below 15 pounds of boost. My earlier turbo (II SPS 62/14) had a lot of problems and didn't want to make any lowend boost and would top out at 32 pounds. I found out that it wasn't installed correctly and was leaking from the flange. It also had some cracks so I upgraded to the Silver 62. I seem to have much better boost down low but I still should be making 46+ pounds of boost and I am not. I have seen the gauge read 45 twice and have never been able to duplicate. It was about 3 days after installing the turbo. I used all new gaskets and replaced exhaust manifold with the ATS and installed the AFE intake manifold. I have even put in an AFE stage 2 xp dryflow s intake and Areoturbine exhaust to make sure the turbo has no restrictions. What gives? I have checked all the hose and tightened them as far as I can. I have an appointment to have a pressure check of the system next Saturday. If that doesn't turn up anything what do I do? Could the boost fooler from the Quad box be having problems? The Smarty also provides boost fooling too so I think I am covered. Thanks for any ideas. Tom J.

STate

I am still learning about how the turbo and wastegate and wastegate actuator all work together. I was told today by a friend that while he was doing research, he found that our 3rd gen Cummins motors run best between 28 and 36 psi. He read quite a bit on the subject and discovered that with the stock turbo anything over 35 psi is counterproductive. He found this out by disengaging his wastegate, he was able to push 40 or so lbs of boost, but he said the truck ran like crap. Turns out anything over 40 psi turns in hot air being crammed in the intercooler and intake. so again counterproductive. Sounds to me like youve got a great setup on your truck, however if you want big Boost numbers you may have to upgrade your turbo,and if you push over 40 psi you may need to go bigger on you head studs to keep from blowing your head gasket.

Dodgezilla

I have a similar issue with my HTB2 turbo. For some reason, on this truck it won't make more than 30psi no matter how much fuel I'm giving it. I also have a boost fooler and I even put a new wastegate on it thinking maybe the old one was damaged. How did I fix it? I put a small clamp on the wastegate hose and the tighter I make the clamp the higher the boost goes. I now get up to 45psi with proper fueling. Now, if it was going higher than that I would loosen the clamp some but since it maxs out there I'm happy. Your II turbo has an adjustable elbow doesn't it? Maybe you need to adjust that. My HTB2 does not have an adjustble elbow but I'm going to get one and see if it helps me some so I can remove the clamp......

CamperAndy

Have you tried towing? Where are you located? Any big hills to run up?

My stock turbo can and will pull a steady 38 psi (at which point the Attitude starts to de-fuel) when towing or climbing some of the mountains around here. It will also spike up to that level when jumping on the interstate.

I don't see any gages on your list of mods, are you only using the Commander to see your boost? If you are then you are seeing the fooled pressure.

BigJohnston

I have temporarily installed an Autometer analog guage to test against the commander and the results are very similar and top end boost is exactly the same. Also just because you have a boost fooler doesn't mean your guages on the commander will be wrong. You just have to tap the signal pre boost fooler or right off of the MAP sensor to get an accurate measurement. STate I probably should have mentioned that I have an aftermarket II SPS Silver 62 turbo 62/14/74 but I have so many mods now that I just let my sig do the talking. I do appreciate all the responses from you guys and I can't imagine trying to do these things without the help I get from the people on this site. Thanks again, Tom J.