This is what he sent

Fuel 10.8 timing 16

 

5500 till full boost?
When does start making boost?

 

With those heads, and that cam I am surprised that it peaks out at 5700. With those gears, tires, and weight I wouldn't personally even want a cam that big.

 

I was thinking the same thing. Maybe for the top end combo and the boost level that turbo is a tad small? I know that can make more HP in a combo that is running higher compression, better fuel, and a smaller set of heads and cam...

I'm kind of thinking along the lines of how a 4.8 can post much better HP numbers with a given turbo than a 6.0 can simply because the 4.8 can rev higher and make power longer. The 6.0 will make more torque, but HP falls off.

I dont know a whole lot about turbo's... im a belt driven power adder guy. Just thinking out loud...

 

Ill get you RPM it started making boost, and also Im also very disappointed on its power curve, Geoff speced this for the turbo build and said this should pull to 6800 and be at full boost at around 3200-3600 when engine rpm comes into stall speed.

 

You don't need that kind of cam and rpm in a big truck

 

Do you know what your tuner meant by this? Do you have any pictures?

I would also think that turbo should spool pretty quickly on your setup. I can spool mine up by 3500 and I have a 80mm with a large exhaust. What wastegate are you running? Is there a possibility of the wastegate sticking open a little?

 

Please bear in mind that you're on a dyno dynamics dyno...I wouldn't call them shitty...they're great dyno's...but they usually read a LOT lower than others.

I still can't see why you're not at full boost until such a high RPM. Is there any timing in it before it comes into boost? If it's only got 16 degrees of advance before the turbo spools, that's not helping anything.

 

First thought is it sounds about right to be honest. The tires hurt on the dyno, depending on the type of dyno and how the operator sets it up. He can calibrate to be more accurate but most dont do this correctly.

So a 6.0 at 6400rpm will move about 520cfm, at SLS air is about 0.075lb/ft^3 so thats about 39lb/m. Lets say you engine makes 350hp NA, and you want to make 800hp with the turbo, so you are going to need (800/350)*39=90lb/m. This is back of the envelope stuff but will give you a good idea.

If you look at the compressor map of that turbo, you are going to have to push it hard to move that much air, but you probably could if you run it closer to 30psi or so assuming none of the stuff I mention below is going on.




Things I would look into:

-Check though is the pressure drop across the intercooler. It may be 14psi at the intake but might be 30psi at the turbo if your intercooler is choked up, in which case you are wasting a lot of power making boost you arent using.

-If you have a filter on the turbo take it off for your glory dyno run. I did this one mine and picked up 50hp.

-Make sure you dont have any boost leaks in your cold side piping.

-Measure converter slip, it will be engine rpm as compared to transmission input rpm. You want this <8% or so before peak torque, after which it should tighten up to around 5% or so. I bet yours is 20-25%, which is just turning torque into heat inside the trans.

-The merge pipes will not limit the power ourput, but they will delay spool if oversized. If you have the generic log/2.5" pipe setup, then thats not your problem. 2.5" hot pipes will support 1500-2000hp. Below 1000rwhp you could probably use 2.25" and be just fine with better spool. The biggest restriction is the turbine wheel, not the pipes. Guys that do dual 3" pipes are not doing any good and just making it laggy.

-Sounds more like your wastegate is a little lazy, is it just run right off the spring with no controller? Using a boost controller that can keep the gate shut until your desired boost will help spool tremondously. Exhaust leaks before the turbo will also greatly affect spool time. Keep in mind dynos typically load the engine different so spool is often delayed on the dyno vs the street. If it spools fine on the street dont chase a problem that isnt real.

While you probably dont need that much cam its not really hurting you either. The turbo is going to move the air no matter what cam you have.

I put mine on a dyno damics and only made 820 or so. Same basic setup on a dynjet made 1008, which is closer in line with what mph my truck ran at the track.

With 8.9 SCR you can run 15psi no problem. Add a meth kit and 20psi is not unreasonable on good gas with good tuning with that turbo.

 

Here is a pic (not to scale) of how the hot pipe comes into bottom of turbo flange.




Tuner said that if we had to cut the pipe between two holes we should have ran the 2.5 right into hole closest to cold side.

Hot pipes are made of Flipped truck manifolds, 2.25" that merge into 1 foot of 2.5 into turbo.

I though this would be a restriction but guy that did pipe said that it will get velocity really moving.