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Discussion Starter #1 (Edited)
Product link: Rzcrew Racing - Airstream Intake Manifold - Honda - Fit-Jazz GE8

I came across this while looking around at aftermarket parts for the GE8 Fit. It looks to be well made and seems like it might actually do something, so I pulled the trigger and ordered one a few days ago. Once I receive it, probably in about a month, I plan on taking measurements, drawing it up in CAD and attempting some flow simulations to see how it behaves. I will then make any necessary modifications to it before installing and update this thread accordingly. They claim to do their own "optimization" of the flow in Solidworks, but I don't know how much of that is just marketing. My main concern is even air distribution between each of the runners. This is a side-feed manifold rather than the center-feed approximation our cars and the GE8 come with, so it is possible it will favor the farthest cylinders. It also does not have a Helmholtz resonant chamber as the standard GE8 manifold does, so there may be some loss in low end torque.

Though it is sold through RZ Crew Garage, it is made by Velocity Race Innovations sdn bhd in Malaysia (hence the VR logo engraved on the runner flange). They have a Facebook page with more pictures of this manifold and all the other things they make. It has an 8mm vacuum port as well as four 6mm ports for other sensors/vacuum driven accessories. Plugs and fittings for all ports are included. The standard brake booster barb is welded in place.

They also have an ITB setup which adapts Toyota 4AGE 20V throttle bodies to fit our LEA engine. A couple reasons I did not opt for this is that it requires a traditional throttle cable, rather than our drive by wire setup, and it eliminates the runners which house the EGR and other (in my opinion necessary) things.

Anyway, just thought I'd share this in case anyone else is interested. More to come when it's finally delivered.
 

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I also noticed their products, but for some other engines. I saw they claim their ITB adapter is modular and can be used with multiple engines ? Don’t exactly see how that would work.
If you went for the ITBs, I saw they could also provide a plenum to make them more streetable.
Will you dyno the car without the manifold, then install, and run again for comparison, on top of the flow testing?
Looking forwards to the results!
 

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How ironic for me as a malaysian who buys intake manifold all the way from US (Golden Eagle) when there is a intake manifold available locally that american are buying lol :LOL::LOL: No offences here..

By the way, RZ crew's manifold is nice with the throttle upgrade version and I think it's designed based on ktuned k20 manifold. I think the main difference of RZC's & Golden Eagle's is the internal individual port design. Golden Eagle's doesn't protrude out from inside if I'm not mistaken.

I'm not sure which perform better but I gained 1kg/m torque at mid range vs the OEM manifold on turbo setup. Hope that'll give you some insight
 

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Discussion Starter #4
@TMX26 I'll see what I can do for dyno data. I'm looking around for a good shop now. I think their ITB setups just use different adapters for different engines but all use the same throttle bodies. So it's like a different set of short runners up to the same throttle bodies custom made for different engine bolt patterns and port sizes/spacing.

That's great information SheepGeeks! I tried to get a hold of a Golden Eagle manifold, but I never got a response from them, so I went with the RZ Crew/VR.
 

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Discussion Starter #5
Couldn't resist but to do some quick simulations partially based on the dimensions of the Fit manifold, so I threw this together. It includes an OEM CR-Z throttle body with the throttle plate wide open. All tests were done at 150CFM (80 ft/s or 24.3 m/s flow velocity). Both plots are for air velocity, the first one as a trace and the second as a cutting plane in the center of the manifold. As you can see, it does seem to favor the last cylinders and is starving the nearest one a little. Obviously, none of this is final and there are likely some things that could be changed to correct this potential issue, but it's exciting for me to see the general velocity profiles.
Trial_Trace1.png Trial_Y_cut.png
 

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Couldn't resist but to do some quick simulations partially based on the dimensions of the Fit manifold, so I threw this together. It includes an OEM CR-Z throttle body with the throttle plate wide open. All tests were done at 150CFM (80 ft/s or 24.3 m/s flow velocity). Both plots are for air velocity, the first one as a trace and the second as a cutting plane in the center of the manifold. As you can see, it does seem to favor the last cylinders and is starving the nearest one a little. Obviously, none of this is final and there are likely some things that could be changed to correct this potential issue, but it's exciting for me to see the general velocity profiles.
View attachment 61586 View attachment 61587
When it's a NA setup, cylinder pulls the air instead of introducing 150CFM at the intake pipe. That's why in reality the manifold are usually below atm pres. at NA setup. You should do simulations on each cylinder with the intake pipe is open to atm pres. and the CFM calculation based on how much and how fast the cylinder pull. For more accuracy, you'll have to take in the suction losses at air filter and intake pipe as well.
 

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Discussion Starter #8
@SheepGeeks You're 100% right about that. I was more or less playing around with what something like a flow bench would give. The 150CFM came from my own car at WOT at 6300pm based on what my OBD2 MAF reading was with a Mugen intake and full 51mm exhaust. I'll do some more in depth calculations to make it more accurate (y)
 

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Discussion Starter #9
Completely re-worked the simulation setup and the model to make things more realistic. Things are looking much better now! I included the OEM runners too so that I can later do a transient analysis simulating the opening and closing of the intake valves. This is still a steady-state, flow bench style setup pulling air through the manifold. The first picture is a velocity profile of the complete manifold right down the middle and the second is a velocity profile looking into the runner ports just after the velocity stacks. The third picture is a particle trace of the manifold to give another perspective on the flow and its direction.
Y_cut_pull_VR.png Z_cut_ports (45.1mm).png Trace_pull_VR.png
 

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Looks like cylinder 3 is choking. You can see the velocity is much more higher and narrower than others at the same flow rate. Probably due to the throttle angle towards the ports (same goes to Golden eagle's). :unsure::unsure:
 

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Discussion Starter #11
@SheepGeeks Yeah, it's not the most even flow throughout the runners, but the OEM one doesn't seem to be a whole lot better on cylinder 3. Transients are really necessary to make sure there are no issues, but I'm still working on those simulations. These steady state simulations give a reasonable impression of flow, however.

I just finished a run of my best guess of the OEM intake manifold, based on measurements I took from mine. This was done under exactly the same conditions as the previous test on the VR manifold. I'm sure Honda put a LOT of thought into the design of the manifold to make the cylinders get as even flow as possible, but cylinder 3 still has some stagnation according to this simulation.


Fit Intake.PNG Y_Cut_OEM.png Z_cut_Ports_OEM.png Trace_OEM.png
 

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Discussion Starter #12
So transient simulations are giving me some difficulty, especially with the free version of Simscale, it seems like one would really need the professional license to get them done properly, I will keep trying. However, I did go through and make a plot in MATLAB of the approximate intake flow versus time for an L15A7 at 6300 RPM. I used the OEM cam data from CAT CAMS website and the flow data from Bad Guys Worldwide for the OEM head as well as the 1-3-4-2 firing order for our engines. I will add the clearance ramps to the plot once I can get a good transient result with the basic shape. This is a bit higher flow than the stock LEA because of the cam, but if anything, it is a more rigorous test of the manifold because of that higher flow. I happen to be running an L15A7 valve-train so it should be fairly representative for my engine. I assumed a 90% volumetric efficiency across all cylinders and a 5kPa pressure drop at the intake tube as a starting point. I then did steady-state simulations in eight steps across the Time-Flow plot to make some pseudo-transient velocity profiles for both the OEM and VRI Manifolds (one point at each intersection and one point at each peak of the curves). Obviously it's not a true transient because the time steps were calculated independently from each other so there is no initial flow for each case, but it's something for now.

Here are the plots for the OEM Manifold:


Intake Timing.png 1 OEM_CYL 1-2 Overlap.png 2 OEM_CYL 1 Max.png 3 OEM_CYL 1-3 Overlap.png 4 OEM_CYL 3 Max.png 5 OEM_CYL 3-4 Overlap.png 6 OEM_CYL 4 Max.png 7 OEM_CYL 4-2 Overlap.png 8 OEM_CYL 2 Max.png
 

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Discussion Starter #13
Keep an eye on the velocity scale as it is a sliding window, the corresponding numbers matter more than the colors.

Here are the velocity profiles for the pseudo-transient VRI Manifold simulations:

1 VRI_CYL 1-2 Overlap.png 2 VRI_CYL 1 Max.png 3 VRI_CYL 1-3 Overlap.png 4 VRI_CYL 3 Max.png 5 VRI_CYL 3-4 Overlap.png 6 VRI_CYL 4 Max.png 7 VRI_CYL 4-2 Overlap.png 8 VRI_CYL 2 Max.png
 

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Discussion Starter #14
Update: The manifold has shipped and will arrive on Wednesday the 29th

Continuing with the simulations, I came across this link:

Manifold Optimization | SOLIDWORKS Simulation (Part 1)

As SheepGeeks said before, it is not 100% accurate because they are introducing 300CFM with the runners open to the atmosphere, but it’s a place to start.

I recreated their simulation for the side feed manifold in Onshape and Simscale and adapted it for our car. In addition, I modeled the Golden Eagle manifold as well for the sake of comparison.

I then simulated each manifold, the OEM, VRI and Golden Eagle, under the same conditions with 150 CFM introduced at the bend before the throttle body and the ends of the runners exposed to atmospheric pressure. From there I used the area integral tool in Simscale to calculate the volumetric flow rates in each runner for each case and found the standard deviation. I was expecting similar results from all of them as they all are similar styles of manifold and similar in plenum volume. The results were as follows:

Flow Balance Results.PNG

As expected, there were no substantial differences between any of the manifolds under these conditions, though I was surprised to see the Golden Eagle with the highest standard deviation, though not by much.

Finally, here are the OEM, VRI and Golden Eagle velocity profiles which resulted from the simulations:
OEM Balance 150CFM.png VRI Balance 150CFM.png Golden Eagle Balance 150CFM.png

I might try and do some development on a dual plenum manifold just to see how balanced it can get. Also, I may look into what can be done to modify the VRI manifold to get more even flow as a standard deviation of 6CFM is far from ideal considering flow distribution is its main purpose.
 

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Discussion Starter #15
The manifold arrived safe and reasonably well packaged:
IMG_0982.JPG IMG_0983.JPG IMG_0986.JPG IMG_0988.JPG IMG_0987.JPG IMG_0990.JPG

I find the lack of gasket recesses a bit odd, but making a few gaskets from some Fel-Pro sheet shouldn't be too hard. Now that I have the manifold in hand, I can make sure the model is as accurate as possible for the simulations.
 

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Discussion Starter #17
I've been spending a lot of time on the models for the OEM and VRI manifolds trying to make sure there aren't any major discrepancies between them and reality. After some fairly drastic re-drawing, I have the following results:

Flow Balance Results Corrected (OEM VRI).PNG

This is again under the conditions of the GoEngineering example with 150CFM being introduced at the intake and the runners exposed to atmospheric pressure. With these conditions, it is more or less a test of how easily the flow can reach each runner. Lower flow numbers in a runner correspond to the air having a more difficult (higher loss) path to traverse. The OEM manifold does a particularly poor job for Cylinder 4, causing the standard deviation to be large among the runners. The VRI manifold does a better job, but is still not where I would like it to be. The Average value at the end is just a sanity check, it should be close to 37.5 CFM (150/4) if the simulation converged properly.

These flow values are quite a bit different than the ones I previously obtained and go against what I initially expected, but I'm learning as I go. This just goes to show that every feature counts in aerodynamics of this scale. Based on this, I omitted the Golden Eagle manifold for this round of testing because I simply do not have the measurements I need to ensure accuracy.

Here are some velocity profiles and traces for both of the manifolds:

OEM Balance 150CFM.png OEM Trace1.png OEM Trace2.png OEM Trace3.png VRI Actual Balance 150CFM.png VRI Actual Balance Trace1.png VRI Actual Balance Trace2.png VRI Actual Balance Trace3.png
 

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Discussion Starter #18
In my researching, I found some flow numbers for other OEM manifolds, albeit from German 5 Cylinder engines. I'm not sure of their flow bench conditions, but here are the standard deviations and absolute flow numbers:

German 5Cyl Flow Balance.PNG

And here are some shots of the manifolds themselves with CFM values written on each runner:

RS2_IM_Flow.jpg AAN_IM_FLOW.jpg 3B_IM_FLOW.jpg 034HO_IM_FLOW.jpg

Make of it what you will, but I feel as though it gives some confidence to the CFD numbers as they are within the same range. The 034HO manifold does a relatively nice job of distributing the flow evenly with by far the lowest standard deviation.

Next up, I will make some small changes to the VRI manifold in CAD and see how the flow responds.
 

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Discussion Starter #19
The area I chose to focus on for the modifications to the VRI manifold was the throttle body flange, the main reason being it is a square profile on the inside of the manifold and I wanted to see if adding a radius to it (like a bell mouth opening into the chamber) would reduce turbulence and help reduce the flow deviation between cylinders.

After many hours of testing, this design came out on top for ease of modification and outright performance. Under the same test conditions as before, I added a 2mm deep radius tangent to the original surface with a radius of curvature of 57.25mm. This resulted in a standard deviation drop from 9.84 CFM down to 5.59 CFM, or a 43% reduction. I tested depths from 1mm to 5mm in steps of 1mm. With 1,3 and 4mm depths, the performance improved slightly over standard, but 2mm and 5mm performed best and nearly identically. I believe the performance benefit comes from a smoother transition from the inlet to the internal velocity stacks and gives a slightly more even fill of the chamber volume.

Here are some CFD screenshots of the 2mm deep flare:
VRI Actual 2mm Full Flare Balance 150CFM.png VRI Actual 2mm Flare Balance Trace1.png VRI Actual 2mm Flare Balance Trace2.png VRI Actual 2mm Flare Balance Trace3.png
 

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Discussion Starter #20
This is what the modification looks like in practice:
IMG_1039.JPG IMG_1040.JPG IMG_1044.JPG

I made a plastic template with the 57mm radius cut into it 2mm deep and started cutting the rough profile with a large round file. I finished shaping it with a flap wheel attachment on a Dremel. I used layout fluid and digital calipers to mark a 2mm larger radius circle onto the outer face of the flange to help give visibility on the template as to when 2mm depth was reached. Overall, it got pretty close to the template and I am satisfied with the results.

Next, I made gaskets out of Fel-Pro 3157 for the two mating surfaces:

IMG_1047.JPG IMG_1048.JPG IMG_1049.JPG IMG_1050.JPG IMG_1059.JPG

I tapped the gasket with a small hammer to imprint and thin the material on the edges and then finished them with an Xacto knife.
 
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