Okay so I would like to see a lot more part throttle/low end boost. I can get up and go fast if I floor it. But then I can kiss fuel milage goodbye. I got thinking about ways to do this and I think that a compound turbo setup would be perfect for this. I know that there will prolly be some flaws in my thinking and im not even sure if this would work, but here goes.... First I could take the manifolds off and switch them to the opposite sides, so the openings are facing the front of the truck. From there you make a y pipe to connect the two, and then run it into the first turbo in front of the engine. For the first turbo I would like to use a very very small one that would spool extremely fast in light acceleration, and then by highway speeds it could be putting out 4-6 psi. I dont have to worry about the top end abilities of it because I will still have the other trubo to count on for that. And then the exhaust gasses expelled from the first turbo would be routed back under the manifold, and exit right where the manifold did, so I could still use the old crossover pipe. The boosted air would be easily fed to the second by fabbing up a pipe to connect the two. The y pipe that feeds the stock turbo would not be needed and would be eliminated and the crossover pipe lengthened so that it connects right into the up pipe. Then back through that turbo and out the exhuast. For sufficient oiling, there is an allen head on the oil cooler by the oil filter. This would supply a lot of oil and pressure and I think would be enough to feed both. Get an adapter to fit in the hole and connect it to some braided tubing and to the first turbo, and then out of that one and on to the second and drained in the valley pan. And thats the basic idea, mounting it I would have to fab up something and could share a coulple of bolts off the timing cover or something. Sorry for the long post lol. But tell me what your thoughts on this are!

 

honestly i dont think you will end up with the results you want.the factory turbo can spool enough to blow the heads apart.and it spools pretty fast as is.thats just my opinion.but this does sound interesting

 

Yes the factory turbo does spool very well, if you stay on the throttle. On a typical accel I will hit about 3 psi. That is over half throttle with a little smoke. Doing 55 its only 2 psi. Now imagine being able to hit 5 psi on accel with less throttle, and cruise at 5-6 psi. This would mean instant off the line boost, almost no smoke, and a lot higher boost down low, which=more low end power. Also I believe with a compound turbo setup that the first turbo feeding into the second helps it build boost? May be wrong there though.

 

what im thinkin is a little over boosting on turbo laying down x amount of and the other putting out y amount of boost what would x+y equal?

 

Yes, after I got them on I would have to play with the wastegate on the ford one get the desired amount of top end boost without overboosting. And I do see the point your getting at that the stock one spools fast enough already, and that got me thinking. Lets say your engine is making 300 peak hp. But your not making that power for very long because your running out of rpm, and you cant get the boost needed to get that power at a lower rpm. Slap on the smaller turbo and now you can hit the amount of boost needed to make 300hp a few hundred rpm earlier. This would help to flatten out your peak power over a wider rpm range and lower when you peak.

 

Imagine. You just described my Banks Sidewinder! Actually on a mild accel (about half throttle) it will put out 7-8psi, and depending on my crusing speed it puts out 4-7psi @ 55-65 respectively.

 

Mack did something something like that, it was a mickey mouse little sort of thing I think they called it a whipple charger or something. You have to change your plans you can't run the oil to boyh off the same line, running hot oil out of one and into the other would cook the second turbo.

 

Personally, I feel that since we are dealing with relatively low boost levels on these engines, a properly sized parallel twin setup is the way to go. 2 smaller turbos sized to spool quickly, yet still sized properly to make decent amounts of boost .
I've had the plan in my head for years, crunched the numbers, plotted the turbo maps... I'm going to give it a shot soon as I'm driving my 6.9 again...

 

87crewdually how are you getting boost numbers like that? And for the oil thing I guess I would have to t the line and find a place to return it out of the first turbo. And I dont want to run really small twins because someday I have plans for headstuds and 18 psi. Small turbos wouldnt like boost numbers like that. But do you think that it would be worth my time?

 

I've been tweeking the fuel and wastegate since I put the new system on 3-4 years ago. I'm now peaking over 15 psi (gauge only goes to 15). My EGT's rarely go over 1050*f . I was having issue with head gasket failure but now I think I got it. At high boost it would bleed boost past the fire ring to the water jacket and deform the rubber coolant seal causing failure. This only happened with Felpro gaskets. On the driver side I still have Victor Reinz with no probs.

 

I didn't say small turbos, I said properly sized. Big difference. My design goal in sizing the turbos I want to use is 20 psi, which is still a relatively low amount of boost, especially considering my old non gated banks unit would push 18. Response was horrible though.
Since you already have a factory turbo on there which does respond fairly well at low boost/rpm levels, a compound setup would be a cheaper route for you, due to only needing to purchase one turbo, not two.
I currently do not have a turbo on my 6.9 at all. Without digging out my old paperwork, I think the Turbos I had decided would work best for what I had in mind were a T3/T4 Hybrid with a V trim T4 compressor and a T3 turbine with a .48 or so housing
I know a pair of Super 60 T3's size out nice and efficient for 15 psi on a 6.9.

 

So..... Do you think it would be worth my time to try?

 

It'll be worth a shot, but, considering the boost levels Dave S. is running with basically the same turbo setup, adding an intercooler to what you already have and the ats upgrade downpipe/exhaust housing might be just as beneficial. At the same time however, that is most likely pushing the existing turbo out of it's efficiency range and making a bunch of heat, so, the compound setup is worthwhile pursuing too.

 

I really am thinking that this could be a doeable project for sometime this summer. I just need to figure out what size turbo. I do not care whatsoever about the high end capabilities of the turbo, I just want it for the best possible low end boost with barely any throttle. And I like compound turbos vs. twins for the fact that one helps to provide air to the other.