What Size S400 Turbo Do I Need? Sizing by Horsepower Target
Picking an S400 turbo size is the single decision that shapes how your truck drives. Go too small and you leave power on the table. Go too big and you own a truck that does nothing until 2,500 RPM and then tries to break itself.
This guide explains how S400 sizes are named, what the numbers actually measure, and how to match a size to your power target and your driving.
How S400 Sizes Are Named
An S400 designation splits into two parts:
- S4 — the frame. All S400s share the same centre housing, bearing system, drain geometry, and mounting hardware.
- The last two digits — the compressor wheel inducer diameter in millimetres. An S476 has a 76mm (2.99") inducer.
So an S467 and an S488 are the same frame with different compressor wheels. Stepping up a size does not change any of your fitment hardware — same flanges, same clamps, same drain.
Inducer vs Exducer
The inducer is the inlet side of the compressor wheel, where air enters. The exducer is the outlet side, where air leaves. S400 naming uses the inducer. Some manufacturers quote exducer for other product lines, which is why cross-shopping specs between brands can be confusing.
S400 Sizes and Power Ranges
| Size | Inducer | US Standard | Approx. Power | Character |
|---|---|---|---|---|
| S464 | 64mm | 2.52" | 700–800 WHP | Earliest spool of the frame |
| S467 | 67mm | 2.64" | 750–850 WHP | Common first big single |
| S472 | 72mm | 2.83" | 850–950 WHP | Street/strip balance |
| S475 / S476 | 75–76mm | 2.95–2.99" | 950–1,050 WHP | The default choice |
| S480 | 80mm | 3.15" | 1,050–1,200 WHP | Serious drag and pulling |
| S483 / S485 | 83–85mm | 3.27–3.35" | 1,200–1,300 WHP | Race-oriented |
| S488 | 88mm | 3.46" | 1,200–1,400 WHP | Top of the 400 frame |
These are directional. A 6.7L Cummins and a 5.9L will not make the same number on the same turbo, and no turbo makes power the fuel system cannot support.
Past 88mm you leave the 400 frame — see the TNT5R 500-frame turbos for 92mm and larger.
The Trade You Are Actually Making
Every step up in compressor size buys airflow and costs response. Specifically:
- More rotational mass. A bigger wheel takes more exhaust energy to accelerate, so it lights later.
- Higher spool threshold. The RPM where the turbo comes alive moves up.
- Lower usable range in normal driving. On the street you spend most of your time below the point where a big S400 is doing anything.
- Higher demands elsewhere. More air needs more fuel, and more power needs a transmission and head studs to match.
The honest version: most people are happier one size smaller than they think they want.
Sizing by What the Truck Actually Does
Daily driven, occasional fun
S464 or S467, T4, 0.90–1.10 A/R. Spools early enough to be pleasant, still makes far more than a stock frame. If the truck sees traffic every day, this is the size that will not annoy you.
Street/strip, ~1,000 WHP target
S476, T4 or T6, 1.10–1.25 A/R. The most common S400 configuration in the market. Good top end, tolerable street manners, well within the capability of a built fuel system.
Drag racing and sled pulling
S480 through S488, T6, 1.25–1.45 A/R. Response is no longer the priority. Assume head studs, a built transmission, and a fuel system to match are already done.
Compound top charger
S472 through S480. The small turbo handles low-end response, so the S400 can be sized purely for top-end flow. Match it to the manifold pressure your high-pressure turbo will actually produce.
Turbine Housing Matters As Much As Compressor Size
Two identical S476s with different turbine housings drive completely differently. A/R controls exhaust gas velocity into the turbine wheel:
- 0.90–1.00 — earliest spool, restricts at high RPM
- 1.10–1.25 — the balanced middle where most street/strip builds land
- 1.32–1.45 — top-end flow at the cost of lag
If you are torn between two compressor sizes, it is often better to take the smaller one with a larger A/R than the bigger one with a small A/R. Full detail: S400 Turbine Housing and A/R Guide.
Sizing Checklist
- What is your realistic power target, given your fuel system as it exists today?
- What does the truck do most days — commute, tow, race?
- What RPM do you actually drive in?
- Is your transmission and bottom end ready for the number you are chasing?
- T4 or T6 — what manifold do you have or plan to buy?
- Single or compound?
Answer those and the size usually picks itself. If not, send them through the Turbo Spec Form and we will work through it with you.
Shop by Size
- TNT467 67MM T4
- TNT472 72MM T4
- TNT476 76MM T4
- TNT480 80mm T6
- TNT485 85mm T6
- TNT488 88mm T6
- All TNT4R T4 · All TNT4R T6
Related Guides
- S400 Turbo Guide: Sizes, Specs, Flanges and Fitment
- S300 vs S400 Turbo
- S400 Turbine Housing and A/R Guide
- S400 for Cummins · Duramax · Power Stroke
- The Origins of the 88mm Turbocharger
Frequently Asked Questions
What size is an S400 turbo?
S400-frame turbos commonly range from 64mm (2.52") to 88mm (3.46") on the compressor inducer. The last two digits of the designation give that measurement in millimetres, so an S476 has a 76mm inducer. All sizes share the same frame and mounting hardware.
How big is an S400 turbo?
The 400 refers to the frame size, not the wheel. Physically it is a large-frame turbo — considerably bigger than an S300 in every dimension, with a 50.8mm (2.00") oil drain bolt centre and either a 4.62" or 5.75" exhaust outlet depending on turbine flange.
How much horsepower will an S400 support?
Roughly 700 wheel horsepower at the small end and up to about 1,400 at the top of the frame. An S467 sits near the bottom, an S488 at the top. Actual output depends on displacement, fuel system, tune, and turbine housing.
What is the most popular S400 size?
The S475 and S476 — 75 to 76mm — are the most widely used, because they balance roughly 1,000 wheel horsepower of capability with street manners most people can live with.
What is the smallest S400 turbo?
The S464, with a 64mm (2.52") compressor inducer. It offers the earliest spool of the 400 frame and is the usual pick for a street-driven first big single.
Does a bigger S400 always make more power?
Only if the rest of the build can use it. A larger compressor needs more fuel, more exhaust energy to spool, and a drivetrain that can handle the result. Oversizing generally produces a slower truck in real-world conditions, not a faster one.
Is inducer or exducer used in S400 naming?
Inducer — the inlet side of the compressor wheel. Some manufacturers quote exducer measurements on other product lines, which is a common source of confusion when comparing specifications across brands.