Measuring Restriction in the Stock Intake System - A GrimmSpeed Report

[Ranatsu]

Originally Posted by GrimmSpeed

Thats not nit picky at all. One of the first things I did was run a hose in the front air damn near the snorkel, and test to the throttle body. The results were the same as when using the fitting at the front of the snorkel, which goes to show that I could have just taped some hose down in that area instead of adding a fitting to the snorkel.

Thanks to everyone who took the time to read this, its a long read, but hopefully it's as interesting to everyone else as it was to us.

Chase
Engineering

lol

[GrimmSpeed]

Originally Posted by Ranatsu

lol

Hahaha! I didn't even think about that when I wrote it, and I refuse to edit it!

Chase
Engineering

[FrsDuke]

Originally Posted by GrimmSpeed

Hahaha! I didn't even think about that when I wrote it, and I refuse to edit it!

Chase
Engineering

potty mouth.

[Sphirit]

Thank you very much!

[arghx7]

This is a good topic. While there isn't really a totally standard way to do this testing, the most common way is to run steady-state rpm and torque/load points with a loading dyno. An engine dyno is easier but that's not an option here.

As airflow increases, the localized pressure will drop. You'll see this on turbo cars especially--it's important for calculating pressure ratio on a compressor map. When you get a heavily boosted engine the restrictions get crazy and that's when rubber pipes on turbo inlets start to collapse and such. You can use different instruments and different measurements, like using a pitot tube instead of a manometer, or doing static pressure only vs taking into account dynamic pressure.

What you'll end up with though is a chart like this:



So x axis might in this case be 25 grams/sec increment. Y axis would be in 1 kPa increments for something like this. Each point is a steady state test from holding the dyno at specific torque points to capture different airflow. Then through the magic of Excel you put a curve fit in there. So at 100 grams/sec you could have atmospheric pressure be 98 kPa, measured pressure be 96.5, and your pressure drop would be 1.5 kPa.

There's always an exponential relationship between mass airflow and pressure drop--when you change the intake pipe you change the shape of that line through the points. Then you can start comparing across different intake pipes or even across different engines if the measuring process is similar. Once you collect enough data trends you can place your intake within an upper and lower boundary line to see how good the design is.

[Turdinator]

Originally Posted by GrimmSpeed

...Thats not nit picky at all. One of the first things I did was run a hose in the front air damn near the snorkel, and test to the throttle body. The results were the same as when using the fitting at the front of the snorkel, which goes to show that I could have just taped some hose down in that area instead of adding a fitting to the snorkel...

Awesome! Thank you for being so thorough and for freely sharing what you found from your tests. It's this sort of support from vendors that keeps me coming back to this forum. I can't wait to see what you come up with for your intake

[zooki]

Since it seems that the snorkel is an integral piece of the whole induction system(and not a restriction), it makes me wonder how these aftermarket(HKS, Zeek, etc.) intake ducts affect pressure, flow, and AFR's on these cars?

[solidONE]

Love the way Grimspeed does things. Science, fuk yea!

[Bobfiveoneohh]

Great write up ! Thanks for the research !


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[Basti]

A number of laws about the behavior and movement of gases come to mind... very interesting.
Thanks guys!

[leicaboss]

@GrimmSpeed - Thanks for your hard work and detailed explanation. This is the kind of stuff that will make me want to support you guys by buying your products, even if there are cheaper alternatives out there. Please continue to keep the community informed

[Turdinator]

Originally Posted by leicaboss

@GrimmSpeed - Thanks for your hard work and detailed explanation. This is the kind of stuff that will make me want to support you guys by buying your products, even if there are cheaper alternatives out there. Please continue to keep the community informed

I will second that!

[GrimmSpeed]

Thank you very much for the kind words everyone, it really means a lot to us as a company!

Chase
Engineering

[Shiv@Openflash]

Awesome testing guys! Your results make sense. At speed, there will always be a positive pressure zone in the bumper opening of the car as the air rams against the radiator. Makes sense that the intake would be configured to pick up from there.