The short answer
A half-inch impact wrench does not have one universal airflow requirement.
At 90 PSI, Ingersoll Rand publishes 4.2 CFM average and 22 CFM under load for the 231C. Chicago Pneumatic publishes 4.4 CFM at free speed and 19 CFM under load for the CP7741. Ingersoll Rand states that the 2236 series requires 36 CFM at 90 PSI.
Those labels describe different operating conditions. Compare a compressor with the figure that matches the way the tool will be used, keep the pressure the same, and leave average, free-speed, and load figures visibly labelled.
Five half-inch impact-wrench records at 90 PSI
The table below keeps the manufacturer's wording instead of blending every number into a generic “required CFM” column.
| Manufacturer and model | Drive size | Published air consumption | Stated pressure |
|---|---|---|---|
| Ingersoll Rand 231C | 1/2 in. | 4.2 CFM average; 22 CFM under load | 90 PSI |
| Chicago Pneumatic CP7741 | 1/2 in. | 4.4 CFM at free speed; 19 CFM under load | 90 PSI |
| Chicago Pneumatic CP7748TL | 1/2 in. | 22 CFM under load | 90 PSI |
| Ingersoll Rand 2125QTiMAX | 1/2 in. | 4 CFM average; 17 CFM under load | 90 PSI |
| Ingersoll Rand 2236QTiMAX | 1/2 in. | 36 CFM required | 90 PSI |
The range is wide even before accounting for how each figure is defined. Drive size alone is therefore not enough to size the compressor. Use the model-specific number and label.
Average, free-speed, and load consumption
Quincy Compressor's buying guide explains that average tool CFM represents intermittent use and is usually based on a 25 percent duty cycle. That makes average CFM different from a continuous-flow requirement. The Ingersoll Rand product pages used here publish both average consumption and consumption under load, but they do not state the averaging method on the specification table itself.
Free-speed consumption is another distinct condition. Chicago Pneumatic lists 4.4 CFM at free speed and 19 CFM at load for the CP7741. A free-spinning tool is not doing the same work as a tool impacting against a fastener, so those figures should remain separate.
For a garage task involving short trigger pulls, the average figure is a useful published reference. For sustained work or a production shop, the load figure reveals how far the demand can rise. Compressor duty cycle and storage still need checking because a numerical airflow match does not show how long a particular compressor can maintain that output.
Pancake-compressor comparisons
The Metabo HPT EC914S publishes 4 CFM at 90 PSI. Against the Ingersoll Rand 231C, that is:
- 0.2 CFM below the 231C's 4.2 CFM average figure.
- 18 CFM below the 231C's 22 CFM load figure.
The Metabo HPT EC711S publishes 2.8 CFM at 90 PSI. It is 1.4 CFM below the 231C's average figure and 19.2 CFM below its load figure.
These comparisons do not support either pairing from the published airflow figures. Tank size does not erase a continuing shortfall in delivered airflow, although stored air can affect how long a brief task runs before pressure recovery is needed.
Some pancake compressors publish SCFM instead of CFM. For example, PORTER-CABLE labels the C2002 at 2.6 SCFM at 90 PSI. Air Tool Match does not subtract that SCFM figure from a CFM-labelled tool requirement. The pancake-compressor directory preserves the original labels so the difference stays visible.
Twin-stack comparisons
Makita publishes 4.2 CFM at 90 PSI for the MAC2400. That exactly matches the Ingersoll Rand 231C's 4.2 CFM average figure on paper, with no airflow margin. It remains 17.8 CFM below the 231C's load figure.
Ingersoll Rand publishes 4.3 CFM at 90 PSI for the P1IU-A9 compressor. The half-inch 2125QTiMAX from the same manufacturer publishes 4 CFM average and 17 CFM under load at 90 PSI. The compressor is 0.3 CFM above the average figure and 12.7 CFM below the load figure.
An exact match or small positive difference is only the arithmetic result. Hose restrictions, fittings, pressure loss, compressor recovery, and compressor duty cycle can change the result at the tool.
A larger portable-compressor example
DEWALT publishes 6.2 CFM at 90 PSI for the DXCM201. Compared with the Ingersoll Rand 231C, it is 2 CFM above the tool's average figure and 15.8 CFM below the load figure.
This is the practical distinction the two tool ratings expose. The compressor's published flow clears the average figure but does not meet the stated load demand. A reader planning occasional lug-nut work and a shop planning repeated sustained use are not evaluating the same operating condition.
Higher-output compressor examples
Rolair publishes 12.5 CFM at 90 PSI for the wheeled 3095K18. DEWALT publishes 14 CFM at 90 PSI for the stationary DXCMLA4708065. Both outputs are well above the 4.2 CFM average figure for the 231C, but both remain below its 22 CFM load figure:
| Compressor | Published output at 90 PSI | Difference from 231C average | Difference from 231C load |
|---|---|---|---|
| Rolair 3095K18 | 12.5 CFM | 8.3 CFM above | 9.5 CFM below |
| DEWALT DXCMLA4708065 | 14 CFM | 9.8 CFM above | 8 CFM below |
The table shows why a compressor category or tank size cannot answer the question by itself. Exact delivered airflow and the intended duty pattern matter.
Hose size and pressure at the tool
The Ingersoll Rand 231C specification calls for a minimum 3/8-inch hose. Chicago Pneumatic specifies a 3/8-inch internal hose for the CP7748TL at a working pressure of 90 PSI.
The compressor's gauge setting is not proof that the tool receives the same pressure while air is flowing. Hose length, inside diameter, fittings, filters, and regulators can introduce pressure loss. Follow the tool and compressor manuals, use the stated minimum hose size, and have a qualified person review permanent air plumbing or electrical work.
A repeatable way to check your pairing
- Identify the exact impact-wrench model and drive variant.
- Record every published airflow figure with its label: average, free speed, load, or another stated condition.
- Record the pressure attached to each figure.
- Find the compressor's published delivery at that same pressure.
- Compare CFM with CFM and leave SCFM-labelled records separate unless the manufacturer supplies an equivalent basis.
- Check hose size, pressure loss, compressor duty cycle, storage, and the instructions for both products.
The impact-wrench airflow directory lists the site's current exact-model tool records. The 90 PSI compressor directory preserves each compressor's published label, source, and check date. Compatible CFM-labelled records can also be compared in the matcher.
Sources checked
- 231C Impact Wrench | Ingersoll Rand Power Tools, checked 2026-10-07.
- 2115TiMAX and 2125TiMAX Series | Ingersoll Rand Power Tools, checked 2026-10-07. The manufacturer table identifies the 2125 variants as half-inch models.
- 2236QTiMAX Product Information | Ingersoll Rand, checked 2026-10-07.
- CP7741 | Chicago Pneumatic, checked 2026-10-07.
- CP7748TL product leaflet | Chicago Pneumatic, checked 2026-10-07.
- Air Compressor Buying Guide | Quincy Compressor, checked 2026-10-07.
- Air Tool Match compressor record directory, with exact manufacturer URLs and per-record check dates for every compared compressor.
Manufacturer pages can change. Recheck the current specifications and instructions for the exact tool, compressor, hose, and fittings before purchasing or installing equipment.
