Honda CivicX Turbo Inlet Pipe Flow Testing – Design Pt.1
Since the introduction of the 10th generation Civic platform with the L15 series engines, intakes have been a fiercely discussed topic; however very little has been discussed about the plastic pipe that connects the “intake system” to the turbocharger compressor inlet. With that, we decided to get some facts about this component and share them with the community. We call this the “Turbo Inlet Pipe”
The turbo inlet pipe aka “TIP” found on the turbo 1.5L is a very intricate plastic injection mold part that provides an airflow path from the intake system to the turbocharger compressor inlet. This part also has attachment points for a purge valve and valve cover breather. These attachment points are the same for both SI and non-SI models so we won’t go into further detail on those.
The above image shows the non-SI design on the left and the SI design on the right.
There is a difference between the two turbo inlets pipes but you may miss it. The difference is the flat “pancake” section of the pipes. The SI design features a thicker/taller “pancake” section that in theory should improve peak airflow capacity.
So what does this mean for you? We put both turbo inlet pipes on a SuperFlow Flow bench to find out where the limit is. The results were surprising.
Both turbo inlets pipes were tested at 25” of H20 and converted to 28” of H20 via the SuperFlow software.
- Non-SI Turbo Inlet Pipe: Steady-state flow of 407.0 CFM @ 28” H2O (2.06 in-Hg)
- SI Turbo Inlet Pipe: Steady-state flow of 414.3 CFM @ 28” H2O (2.06 in-Hg)
First shocker…the delta between the SI and the Non-SI is much smaller than we expected. It appears that the “pancake” section does make a difference but the difference is not significant. From this single data point we say it’s not worth buying the SI turbo inlet pipe as an upgrade but go ahead and swap it out if you can pick up a SI version for free.
Looking forward, there is a rule of thumb that states airflow through a round pipe should not exceed 0.40 mach (aka the speed of sound). The reason for this is to maintain smooth laminar flow through the pipe. Let’s apply this to the turbo inlet pipe. The turbo compressor inlet in the pipe has an ID of 1.88”; back calculating to find the max CFM at 0.4 mach puts us at approximately 510 CFM.
A better question might be - how does this affect power potential? Datalogs from a W1 Turbo equipped Civic SI show a peak flowrate of 432 CFM at an unknown vacuum. That is getting close to the 0.4 mach limit so there may be opportunity for considerable gains with a performance turbo inlet pipe setup on upgraded stock flange turbos.
The question is...how much is there to be gained?
With that we’ll let you decide. Should 27WON dig deeper into the turbo inlet pipe? Do you want more power or just a better looking turbo inlet pipe? Let us know what you think!
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