How is it done ??? I have always wondered how the "plumbing" is done using compounding.... does the air charge coming out of the first turbo get plumbed to the inlet of the second ?? and how is the exhaust sent thru the second ? I have never seen the turbo setup's,, let's say on a tractor pulling engine,,,,but I have been told that they use like 5 or 6 turbos in compound to make 60 + psi of boost.... Can anyone shed some light on this and explain compounding ?
My kit - Bottom (primary) turbo recieves fresh air from air filter. Compresses air and discharges up and forward. Uturns and heads to the inlet of the top (secondary) turbo, wher it is again compressed and discharged to the intercooler. Exhaust is expelled from the motor and passed through the secondary turbo's exhaust turbine. It exits the turbine, 90's down and enters the exhaust turbine of the Primary turbo, and is expelled to the downpipe. Oil supply for each turbos' bearings are separate Questions?
Are the turbos of equal size ? How much boost does it make ? What else is required to run dual turbos ? injectors ? Reprogramer ? Intercooler ? overall cost ? Last but not least,,,any drawbacks ? ( other than the obvious decreased engine lifespan....)
One turbo will be larger than the other, thats the reason for twins. One will spool faster and provide good bottom end boost and the second will come alive later and provide massive top end. Boost varies, I think I've heard guys talking to have a pair make as little as 40lbs or so, and have heard peak boost from a monster pair in the 180lbs range. Two turbos obviously, and all the piping to make it all work. That is usually the most costly part, all the piping and material. You need a lot of fuel, enough to decently run two turbos. Regardless of how you get the power from injectors, boxes, etc, I still wouldn't bother with twins under 450HP. Thats the whole idea of twins. Guys that are in the 650HP class with a big single have a nasty slow smokey bottom end, to gain big top end from a huge turbo. That would be the popularity of the twins, a smaller turbo to help bottom. If you are running 450-500 or less horsepower, you can get away with a nice custom turbo that spools great with good bottom that still flows enough air at higher RPM to keep 475ishHP happy. They run from $3K and up it seems, from what I have seen. Drawbacks would be that you will likely have to O-ring your head. Twins vary easily make 50+lbs of boost and will pop a head gasket. Also the overall cost would be a drawback.
On the 3rd gen Cummins, like your 07, little is needed really. I still have stock head bolts. I have the BD set, and a TST will spool them. I have 100hp injectors, 50hpp injectors would be perfect for a Daily Driver or a tow rig. Like RJF said, you really need 450+ to effectively spool a decent set of twins. There are alot of advantages to them, and they are the only way to get decent driveability out of a high powered truck.
