S300 vs S400 Turbo: Which Frame Is Right for Your Build?

This is the decision to make before you buy a manifold, because the two frames are not interchangeable. An S300 and an S400 use different turbine flanges, different exhaust outlets, and different oil drain bolt centres. Choosing wrong means buying the hardware twice.

Here is what actually separates them, and how to tell which one your build wants.

Side by Side

S300 S400
Frame 300 frame 400 frame
Compressor range 57–66mm (2.24–2.60") 64–88mm (2.52–3.46")
Typical power Up to 600–700 WHP 700–1,400 WHP
Spool Noticeably earlier Later, size dependent
Turbine discharge 4.25" marmon 4.62" half marmon (T4) or 5.75" marmon (T6)
Oil drain bolt centre Mid frame, 50mm (1.97") Large frame, 50.8mm (2.00")
Drain port 10AN adequate 12AN recommended
Best for Towing, daily driving, sub-700 builds Four-digit power, drag, pulling

The Real Difference: Where the Power Lives

Peak horsepower is the least interesting distinction between these frames. What matters day to day is where in the RPM range the turbo is working.

An S300 lights early. On a loaded truck pulling a grade, that means boost when you need it, at the RPM you are actually at. An S400 has a higher ceiling but takes longer to get there — excellent on a track, less pleasant merging onto a highway with a trailer.

If you find yourself justifying an S400 by saying "I'll just rev it more," think honestly about whether you will.

Choose an S300 If

  • Your power target is under about 700 wheel horsepower
  • The truck tows, and tows often
  • It is your daily driver
  • You value throttle response over peak numbers
  • Your fuel system is stock or lightly upgraded
  • You want a simpler, cheaper installation

Choose an S400 If

  • You are chasing four-digit power
  • The truck is a dedicated race, drag, or pulling vehicle
  • You already have the fuel system, studs, and transmission to use it
  • You are building a compound setup and need an atmospheric charger
  • You are prepared for later spool as the cost of the ceiling

Or Run Both: Compounds

The reason this does not have to be an either/or is compounds. A common high-power arrangement runs an S400 as the atmospheric (low-pressure) charger feeding a smaller S300 as the high-pressure unit.

The S300 lights immediately and gives you the low-end response of a small turbo. The S400 carries the top end. You get most of both, at the cost of complexity, packaging, and money.

This is the standard answer for a truck that genuinely needs to both tow and race.

What Changes If You Switch

Moving from S300 to S400 is not a turbo swap. It is a hardware swap:

  • Manifold. Different turbine flange footprint.
  • Downpipe. The S300 uses a 4.25" marmon discharge. The S400 uses 4.62" half marmon on T4 or 5.75" marmon on T6. They look similar and will not clamp together.
  • Oil drain. S300 is mid frame at 50mm (1.97") bolt centre; S400 is large frame at 50.8mm (2.00"). Only 0.8mm apart, so measure with calipers.
  • Drain port. Step up to 12AN for the larger frame.
  • Charge piping. Compressor discharge sizing usually changes.
  • Wastegate. A larger frame needs proportionate boost control.

Full detail in the S400 Flange Guide and Oil Drain Guide.

Hardware for Both Frames

S300 / S200

S400

Related Guides

Still deciding? Send your build details through the Turbo Spec Form.

Frequently Asked Questions

What is the difference between an S300 and an S400 turbo?

The S300 is a smaller 300-frame turbo running roughly 57 to 66mm on the compressor and supporting up to about 700 wheel horsepower, with noticeably earlier spool. The S400 is a larger 400-frame turbo running 64 to 88mm and supporting 700 to 1,400 wheel horsepower. They use different turbine flanges, exhaust outlets, and oil drain bolt centres.

Can I fit an S400 where an S300 was?

Not without changing hardware. The manifold flange, downpipe flange, oil drain flange, and usually the charge piping all differ between the two frames.

Which is better for towing, S300 or S400?

The S300, in most cases. It spools noticeably earlier, which means boost at the RPM you actually tow in. An S400 has a higher ceiling but is working higher in the rev range.

Will an S300 downpipe flange fit an S400?

No. The S200/S300 turbine discharge marmon is 4.25", while the S400 T4 half marmon is 4.62" and the S400 T6 marmon is 5.75". They look similar in photos but will not clamp together.

Can you run an S300 and S400 together?

Yes, and it is a common high-power arrangement. The S400 acts as the atmospheric charger feeding a smaller S300 as the high-pressure unit, giving low-end response from the small turbo and top-end capability from the large one.

At what horsepower should I move from an S300 to an S400?

Around 600 to 700 wheel horsepower is where an S300 typically runs out of air. Below that an S300 is usually the better-driving choice; above it the S400 frame becomes necessary.

Do S300 and S400 use the same oil drain?

No. The S300 is a mid-frame turbo with a 50mm (1.97") drain bolt centre, and the S400 is large frame at 50.8mm (2.00"). They are only 0.8mm apart, so measure with calipers rather than assuming.