There is a big trend in the diesel pickup market to use T-4 non-waste gated housings as a turbo upgrade from stock. For many, it seems like a great alternative. Without waste gates, these turbos are cheap, often between $500 and $800 instead of the typical $1500-$2000 price tag.
However, like most things in life, you get what you pay for. These T4 turbos, are generally created for OEM, are not manufactured for high performance vehicles but rather for small industrial, low RPM engines or gasoline cars that don’t have the same need most diesel truck drivers have like quick spool up, high top air flow, and high pressure ratios.
What people don’t realize is that these turbos are not bolt in applications. Without a waste gate, the housings have a high A/R ratio, somewhere around .9 or higher. This means the spool up is incredibly slow and while the top end performance is fair to good, the bottom end performance and drivability is really sacrificed.
There are also hidden costs. T4 housings were not manufactured to fit on a Dodge with a Cummins engine so you have to adapt the intake, the exhaust pipe, the exhaust manifold, and the intercooler tubing. After all these extra costs, you are still left with a turbo without a performance bearing structure. They hold up okay and are decently reliable, but they are not very drivable and will not have 360 degree thrust bearing or grooved journal bearings to keep oil on the shaft, at extremely high speeds. They are just not structured for high performance application, and are more suited to lower boost pressures.
The reason waste gated housings costs so much and people are willing to pay that price is because a waste gate is the most simple form of a variable geometry housing. This means that a smaller turbine housing can act as a larger turbine housing by virtue of the waste gate which allows the exhaust to bypass efficiently. This increases the capability of the housing to flow 10-15% more without sacrificing spool up. A T4 might flow well on the top, but it will generally be a dog on spool up and drivability.
Before you go buy a big, inexpensive T4 turbo, give us a call and ask a few questions so you can be an informed customer. We understand the sacrifices made to be able to drive a great truck with a great engine and know there is nothing worse than buyer’s remorse. We can give you quality parts and guarantees so that you get the most value for the truck you love.