Any CFD experts here? Need some advice on custom intake mani - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

speedingmofa · 01-20-2017, 03:33 AM

Hi guys,
As my build will be using an sr16ve head and the stock plenum faces the wrong way. Chopping and flipping the stock VE plenum doesn't look like a neat option as the runners wouldn't line un correctly. Also thought about chopping a stock s14 sr20det intake and welding it to the VE flange, but to be honest, the DET runnerrs are alot narrower. I was discussing this with a friend and he so happens to be a metalworker so he offered his services to build me a plenum that would mate to the lower VE runners (xcessive style). I would need to provide him with all the sizes and shit though...

So i pulled my CAD knowledge out of the old closet, pulled some cracked cad software off the net and started right away and even did some flow simulations on the darn thing.

This is where my design comes to a halt... I have no knowledge of intakes so hopefully some experts are willing to enlighten me a bit on how i can make improvements instead of second guessing.
The numbers are in but same as above, i'm not sure how i can use these numbers to improve my intake design.

The simulation was done without the transient conditions of an engine. So the figures you see below are of static flows (?). I would like to do a transient flow simulation, but am unsure how...

Parameters used:
Medium: Air
Mass flow rate: 0.14 kg/s (equals to +/- 300cfm, what the head would flow)
Pressure: 1 bar
Plenum size internal volume: 3.7L (including runners)

Arrowking · 01-30-2017, 10:22 PM

I have some experience with my school's FSAE team doing CFD simulations (primarily using Ansys Fluent). Really though I mostly know it pertaining to designing aero devices but the software can definitely do an intake. I don't know much about the optimum air flow characteristic of an ICE engine so I can't help much there. I will say that with CFD it's easy to get meaningless results (but it'll produce a pretty, colorful picture).

speedingmofa · 01-31-2017, 01:40 AM

@Arrowking Thanks for your reply bud, appreciate it.

You're right on the money about the meaningless pretty colorful pictures. hahah that's exactly what I have here. I wonder though, do all the big names improve their design through CFD or do they just muck up something pretty and hang a $1000 price tag to it? When you boil it down, basically every big volume plenum WILL make more power, given there are no major obstructions in the air flow.

Arrowking · 01-31-2017, 10:09 PM

Maybe they do but honestly I don't have a clue. Most probably just go by what traditionally has made power and/or moved the powerband and go from there. It's something I'd love to go deeper into (maybe during the summer if I get bored...I already have a design or two for an intake in Solidworks) but really it'd be a lot of work for moderate gains in power.

ReedMann · 02-01-2017, 10:20 AM

I don't have experience with CFD simulations, but know from using FEA (structural design equivalent to CFD) that the boundary conditions are everything to getting accurate results. That said, will this car be turbocharged? If so, you will want to use a greater inlet pressure than atmospheric.

I'm not sure how accurate a steady flow analysis would be, but I'm sure the transient is much more difficult to develop to a useful level. You would have to take into account the varying pressures across the plenum as the valves open and close and the engine operates at different RPM. It can get very complex very quickly. One thing you could use the steady state analysis for is to ensure each runner is receiving equal mass flow rates at their respective exits. You could tweak the runner and plenum shapes to tune this.

Another thing to keep in mind is that larger plenums work by "storing" a large volume of air that the engine can draw from. The flow characteristics aren't nearly as important as ensuring there is sufficient air stored. I imagine smaller plenums and probably OEM plenums are much more sensitive to the flow characteristics inside since they don't have as large of a reserve to pull from.

Just some speculation based on my engineering knowledge...

01-20-2017, 03:33 AM	#1
speedingmofa Zilvia Member Join Date: Nov 2012 Location: Rotterdam, the Netherlands Posts: 290 Trader Rating: (15) Feedback Score: 15 reviews	Any CFD experts here? Need some advice on custom intake mani Hi guys, As my build will be using an sr16ve head and the stock plenum faces the wrong way. Chopping and flipping the stock VE plenum doesn't look like a neat option as the runners wouldn't line un correctly. Also thought about chopping a stock s14 sr20det intake and welding it to the VE flange, but to be honest, the DET runnerrs are alot narrower. I was discussing this with a friend and he so happens to be a metalworker so he offered his services to build me a plenum that would mate to the lower VE runners (xcessive style). I would need to provide him with all the sizes and shit though... So i pulled my CAD knowledge out of the old closet, pulled some cracked cad software off the net and started right away and even did some flow simulations on the darn thing. This is where my design comes to a halt... I have no knowledge of intakes so hopefully some experts are willing to enlighten me a bit on how i can make improvements instead of second guessing. The numbers are in but same as above, i'm not sure how i can use these numbers to improve my intake design. The simulation was done without the transient conditions of an engine. So the figures you see below are of static flows (?). I would like to do a transient flow simulation, but am unsure how... Parameters used: Medium: Air Mass flow rate: 0.14 kg/s (equals to +/- 300cfm, what the head would flow) Pressure: 1 bar Plenum size internal volume: 3.7L (including runners) __________________ Need UKDM/EUDM/JDM/RHD Nissan parts? Hit me up Insta: skids14 Last edited by speedingmofa; 01-20-2017 at 05:19 AM..

01-31-2017, 01:40 AM	#3
speedingmofa Zilvia Member Join Date: Nov 2012 Location: Rotterdam, the Netherlands Posts: 290 Trader Rating: (15) Feedback Score: 15 reviews	@Arrowking Thanks for your reply bud, appreciate it. You're right on the money about the meaningless pretty colorful pictures. hahah that's exactly what I have here. I wonder though, do all the big names improve their design through CFD or do they just muck up something pretty and hang a $1000 price tag to it? When you boil it down, basically every big volume plenum WILL make more power, given there are no major obstructions in the air flow. __________________ Need UKDM/EUDM/JDM/RHD Nissan parts? Hit me up Insta: skids14

01-30-2017, 10:22 PM	#2
Arrowking Zilvia Member Join Date: Feb 2014 Location: U.S. Posts: 213 Trader Rating: (3) Feedback Score: 3 reviews	I have some experience with my school's FSAE team doing CFD simulations (primarily using Ansys Fluent). Really though I mostly know it pertaining to designing aero devices but the software can definitely do an intake. I don't know much about the optimum air flow characteristic of an ICE engine so I can't help much there. I will say that with CFD it's easy to get meaningless results (but it'll produce a pretty, colorful picture).

01-31-2017, 10:09 PM	#4
Arrowking Zilvia Member Join Date: Feb 2014 Location: U.S. Posts: 213 Trader Rating: (3) Feedback Score: 3 reviews	Maybe they do but honestly I don't have a clue. Most probably just go by what traditionally has made power and/or moved the powerband and go from there. It's something I'd love to go deeper into (maybe during the summer if I get bored...I already have a design or two for an intake in Solidworks) but really it'd be a lot of work for moderate gains in power.

02-01-2017, 10:20 AM	#5
ReedMann Join Date: Nov 2010 Location: NC Posts: 5 Trader Rating: (1) Feedback Score: 1 reviews	I don't have experience with CFD simulations, but know from using FEA (structural design equivalent to CFD) that the boundary conditions are everything to getting accurate results. That said, will this car be turbocharged? If so, you will want to use a greater inlet pressure than atmospheric. I'm not sure how accurate a steady flow analysis would be, but I'm sure the transient is much more difficult to develop to a useful level. You would have to take into account the varying pressures across the plenum as the valves open and close and the engine operates at different RPM. It can get very complex very quickly. One thing you could use the steady state analysis for is to ensure each runner is receiving equal mass flow rates at their respective exits. You could tweak the runner and plenum shapes to tune this. Another thing to keep in mind is that larger plenums work by "storing" a large volume of air that the engine can draw from. The flow characteristics aren't nearly as important as ensuring there is sufficient air stored. I imagine smaller plenums and probably OEM plenums are much more sensitive to the flow characteristics inside since they don't have as large of a reserve to pull from. Just some speculation based on my engineering knowledge...