Intake Runner Length Dyno TESTED – Short vs Long
Dave Walker did dyno testing of intake runner length vs engine torque on a 1.6 Ford Zetec SE (Sigma) engine. You can read the full article here, well worth a read. The table below is the data from the testing in an easier to digest form.
Intake Runner – Test Data
Nothing changed between tests, just runner length.
| RPM | 40mm lbs/ft | 40mm bhp | 80mm lbs/ft | 80mm bhp | 120mm lbs/ft | 120mm bhp | 170mm lbs/ft | 170mm bhp | 330mm lbs/ft | 330mm bhp |
| 3000 | 113 | 65 | 111 | 63 | 113 | 65 | 116 | 66 | 115 | 66 |
| 4000 | 118 | 90 | 121 | 92 | 126 | 96 | 127 | 97 | 135 | 103 |
| 5000 | 127 | 121 | 128 | 122 | 138 | 131 | 135 | 129 | 137 | 130 |
| 6000 | 135 | 154 | 136 | 155 | 140 | 160 | 136 | 155 | 128 | 146 |
| 7000 | 133 | 177 | 132 | 176 | 133 | 177 | 132 | 176 | 124 | 165 |
Velocity Stack vs Straight Cut Pipe
Not on the graphs or table, flair/trumpet/velocity stack vs straight cut, max difference around 5%. In short, velocity stack is worth it. Powerband RPM range, not affected.
Tested on flow bench, trumpet vs straight cut minimum difference in flow which suggests pulse tuning is the driver.
Tapered vs Parallel
No real difference found in this test.
Conclusion – Inlet Runner Length Test
On this engine, with this cam, with these ITBs etc etc, 120mm looked optimum. Not giving up much down low, as good as short runners up top.
Short runners only started outperforming the 330mm runners at 5000/5500RPM+. After 5000RPM the 330mm runner really drops off badly.
The numbers themselves don’t show that big a difference, but if you look at it in percentages there are some big differences.
Other Interesting Links
4AGE Testing different intake lengths.
Comment on the video
“
@MrTL3wis
2 years agoOK, so in the day I raced Toyota Atlantic. I’ve got a lot of time playing with intake trumpets on a 4A-GE. You definitely want the trumpet on the end, but I understand why you tested like you did. We would run as short as 50mm trumpets on ovals when we were only concerned about 9200-10000 rev range. We would run from 80 to 150mm trumpets depending on if we were looking for more high end or more mid range. In the last few years, the best road course / street course setup was with cylinders 1-4 about 30mm shorter than cylinders 2-3. A high rev track might be 80/110 while a street circuit might be 130/100. It seemed to help mid-range without hurting the top end. We would also run a tri-y header on everything except the ovals, which was 4-into-1. The airbox sizing is very important. You’re missing something if you haven’t gone down that bunny-hole.“
From what I understand, the commenter is also saying an average of 120mm is power and wide powerband. This suggests to me length is dictated by RPM as opposed to cam profile.
