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 57–80mm (2.24–3.15") 64–88mm (2.52–3.46")
Typical power Up to 820 HP 820–1,520+ HP
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-820 builds Four-digit power, drag, pulling

Ceiling is not the same as the right choice. Individual S300-frame turbos are rated well above 820 HP; the largest reaches 1,300 crank. Those are compressor ceilings. The figure in the table is the practical crossover — the point past which a 400-frame turbo does the same job with less strain, better efficiency and room to grow. Buying to a ceiling rather than to a working range is how people end up with a turbo that is technically big enough and unpleasant to live with.

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 820 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 80mm on the compressor, recommended up to about 820 horsepower, with noticeably earlier spool. The S400 is a larger 400-frame turbo running 64 to 88mm and supporting 820 to 1,520+ 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 820 horsepower is where we would move you across frames. That is a selection threshold rather than a physical limit — individual 300-frame turbos are rated well above it, up to 1,300 crank on the largest — but past 820 an S400 makes the same power with less strain, better efficiency and room to grow.

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.

Power ratings on this page are quoted in crank horsepower (HP). Figures previously published in wheel horsepower (WHP) have been restated using our in-house tested conversion — the hardware and its capability are unchanged.