cause that is what the WG is supposed to do. My truck has a single Tial 44mm it holds boost to redline no dropping with just spring.

Plenty of bigger displacement motors run single WG and dont have issues of boost falling off. His setup seems pretty simple so to me it doesnt make sense that its losing 3lbs by redline on that boost level, its not like the turbo is running out of breath or anything

Are you 100% sure you have no boost leaks or Vac leaks? Done any tests?

 

Because its a bigger displacement motor I was wondering if the WG is too small or should that not matter? And Im limited in WG selection cause I have 2 bolt flanges for mine, unless I weld on a v band, which is possible

And I know the Boost controller wont fix that issue but it will fix the issue with the amount of boost I want to run

Between the Throttle body and the WG I am am 100% sure theres no leaks. As for vacuum leaks I dont where one could be. Its not like this is a old setup I just finsihed it a few months back and have barely driven the truck. The truck holds a steady 14 inches of vacuum at idle and I dont hear any hissing in the engine bay at all.

What kind of tests did you have in mind?

And I think GMCtrk is right, my turbo only has a 68 mm turbine so I wouldnt be surprised if it makes extra back pressure. And I inquired to kyle about a 3.5 inch downpipe a while back and he said the 3 inch DP will outflow the turbine so dont worry about it. So I dont see how the 4 inch duramax cat back is a restriction

As usual one has to be chosen, lower end or top end power. Cause this thing spools so fast when you mat it to the floor but if the turbine were bigger it would take longer yes? Cause I saw that thread about the 78/76 and went a new wastegate is half the cost of a new turbo but no I should make what I have work

And thanks for the input guys I appreciate it

 

If I have a 3/8 t lying around Im gonna go try running the WG off the intake instead of the TB and see what happens Ill give an update in a little bit

 

only 14 vac? but i guess you have a cam right?

my truck pulls 18-20 on vac but im bone stock motor, if WG size was a issue it would be over boosting usually

 

Yup isky triple 12 cam in her

So I tried and no luck, however it only drops to 5 now that ive been watching closely, so only 2 lbs.

Well in theory my issue could be that I have a WG on the smaller side with a small turbine, so the WG is opening like it should to maintain 7 lbs at the intake but the back pressure increases so much when the RPMs come up that its forcing open the WG more and then the turbo isnt making the boost it should, even though the WG is supposed to stop that from happening.

7-4 was a big drop imo but 7-5 is not so bad. So when I get the boost controller lets say 11-9 wont be too bad either I guess

But if someone can figure out how to keep my boost flat without a electronic boost controller Im all ears

 

You have a 65mm turbine also, not 68mm. Doubt that's your issue but just sayin.

 

Oh maybe it is a 65 that sounds right, I still have the specs from the box with the receipts in my garage

 

Also I was surprised when I did a brake boosted launch that the truck actually build 2 lbs of boost and I wasnt trying hard, I always thought on a stock stall you couldnt build any boost

 

hard to say man, verify the spring in the WG first, make 100% sure its a 7lb spring. maybe try to run the vac line somewhere else . Do a boost leak test, soapy water works great for finding those

those are just things i would look at

 

Well kyle told me generally that spring makes 10 lbs, see the JGS wastegate only has 3 springs that are different thickness, and arent for specific boost levels

How do you put pressure in the whole system to look for leaks?

And I just did that, no difference unfortunately