Racer X Intake manifold design, development, and results
 

As some of you know, we have been tinkering with the intake manifold for a little over a year now, with the most work being completed in the last couple of months. We have openly stated that we have tested 4 intake manifold variations, but we have actually tested 6 and we still plan to test 2 more variations. Let’s start at the beginning and we can bring this to our current stage of development.

Design:

The plenum, runner diameter, and runner length were the primary concern. We started with a plenum size that was slightly larger than engine displacement and quickly found that airflow was bias to the rear cylinders which is not of much surprise. If you look at the OEM manifold, it’s quite simple to see that would be the case. The runners closest to the throttle body make it difficult for air to enter. With our plenum design we moved the rear middle section of the plenum forward, ran several CFD variations to find a happy medium of airflow to all cylinders and then altered the radius and angle to optimize further. This worked quite well and would prove out in testing (or so we thought).

Next, we looked at runner diameter. We started with the intake valve diameter and multiplied this by 80%, all the way up to 120% (and slightly larger). We then used the closest runner diameters from standard material stock to find which diameter would provide the best velocity without hurting overall flow and in turn make best power. (We started with roughly 80% due to the fact that airflow passing the valve is not 100% efficient).

Finally, we moved on to runner length, although this is slightly more difficult due to the fact that it must fit in the engine bay and be packaged with the plenum and flanges. The runner length would remain unchanged with the exception of manifold #6 which would require a runner length that was roughly 1.5” longer.

https://racerxfabrication.com/pics/f...manifold/1.jpg

https://racerxfabrication.com/pics/f...manifold/2.jpg

https://racerxfabrication.com/pics/f...manifold/3.jpg

Development:

We started with the optimized plenum design for manifold #1. We used the smallest runner diameter and the standard runner length that would be used through out all of the testing. Manifold #1 would provide decent results at the beginning of the power band, but falls on its face around 5800 RPM. Our initial thought was the runner diameter is too small.

https://racerxfabrication.com/pics/f...E-Manifold.jpg

Manifold #2 would increase runner diameter by 7% (I know doesn’t seem like any change would happen). We found similar results, gains through the majority of the RPM range, but again falling around 5800 RPM but making more power than manifold #1 (around 10 whp). With this increase in power we decided to go back to manifold #1 and check to see if there was any power gain from increase plenum size.

https://racerxfabrication.com/pics/f...E-Manifold.jpg

Manifold #3 would increase the plenum size by 50%, the easiest increase would force us to comprise our optimized design. It would allow us to see if there were any differences or gains from increasing the plenum volume. The results would be quite similar to manifold #1, however there were slight losses in the bottom compared to manifold #1, but it would produce slightly more power at the higher end of the RPM range.

https://racerxfabrication.com/pics/f...E-Manifold.jpg

We concluded from the 3 previous tests that we would keep the optimized plenum design for manifold #4 and increase the runner diameter again. The runner diameter increase would be 21% this time. We thought this would yield much better power at the higher end of the RPM range, but after testing the results did not provide much, if any gain over manifold #2. This an anomaly to us, why did manifold #4 produce such similar results to #2? The conclusion was quite simple and we ended up redesigning our cylinder head flanges to accommodate the reasoning.

https://racerxfabrication.com/pics/f...E-Manifold.jpg

Manifold #5 was the same runner diameter, runner length and plenum, the only change would be the cylinder head flange. We determined the angle we used to open the flange was causing the airflow to decelerate enough that it was impacting overall power. Manifold #5 is currently the closest to overall power compared to the OEM manifold, with the exception of the low and mid RPM gains that can be seen in the graphs.

https://racerxfabrication.com/pics/f...manifold/4.jpg

https://racerxfabrication.com/pics/f...manifold/5.jpg

https://racerxfabrication.com/pics/f...E-Manifold.jpg

For manifold #6 we decided to test an outlier that would share a plenum size that was similar to OEM. The OEM manifold uses quite a small plenum, we estimate the volume around 80 to 100 cubic inches. The plenum we designed would be smaller than that, at 50% of our original plenum size. The results were very interesting. Enough so that we plan to test 1 more that is larger with a few extra tricks. The gains from the small plenum in the lower RPM range are very impressive with gains of up to 20 whp in the torque dip, however it lacks the plenum volume and runner size necessary to provide the power that is needed at the upper RPM range.

https://racerxfabrication.com/pics/f...E-Manifold.jpg

Manifolds #7 and #8 are currently designed. We plan to build and test them soon, however we would like some feed back from the community. Do you think this is a product that you would be interested in? We have spent a considerable amount of time designing, machining, and testing. What would be the ideal results you would like to see from an intake manifold?

Looking forward to the feedback from the community, please let me know your comments and thoughts.

More midrange with equal top end would be nice but probably hard to attain. Nice work though. Impressive commitment on your part

OEM knew what they were doing with i.m. design.

Are you testing these with the stock exhaust manifold? I haven't seen any reference to resonance tuning...? I highly doubt you didn't consider it, but I thought I'd ask.





I would be interested in this product, but it'll have to give decent gains across a good chunk of the power band while not losing anywhere. That ~7% lose in the top end is a hard pass but I look forward to what you come up with from here.



I do appreciate your commitment and research. Thank you for sharing!

Hmm, you were running with stock tune? Have you logged engine params apart from dyno performance numbers? Just that i think that some designs may have underperformed due stock ecu tune, not custom tailored to design of these manifolds. For example - what if different design means that at specific rpm range it's not so much that intake manifold optimisation itself is at work, but with stock tune/stock MAF nonrescaled sensor it may run too lean at some rpms, resulting in extra knock and tune retarding timings & robbing power? Or too rich, and not producing power it might have?

I love the scientific method based testing you are using here, and the honesty in showing that it is pretty difficult to beat modern OEM design. That is sadly lacking in so much of the performance aftermarket.



I would be interested in any intake that could help reduce the torque dip without penalties in the top end, especially one as good looking as this.

So hopefully there will be no more claims that the stock manifold is a "bottleneck "

We are using the OEM air intake box with a drop in filter, other than the intake manifolds it is completely stock (engine, exhaust system). I do agree its tough to look at as an upgrade if its losing power at the top end.

We are using the OFT V4 stage 1 tune, we have logged all of the manifold runs. We sent off the data for manifold #5 to OFT along with payment to see if they can optimize the tune for the intake manifold but we have not heard anything from then yet. I believe you are correct, optimizing the tune should in theory yield a bit of additional gains.

This was the original goal to improve power in the low end and middle of the RPM range with similar performance but slightly better at the top end.

Without a doubt this will stir interest. Especially with you guys being super transparent in the development process and saying the OEM manifold doesn't leave alot on the table. Some people don't want to spend the cash on the 2017+ red manifold and would like something like this with all the parts needed for install included and such. Also I can imagine CNC fabrication time is risky and may be expensive, so you might need to compare this all in cost to the cost of someone doing the OEM style red manifold install before mass market sale.

Also if someone like shiv from OFT can assist with OTS tunes for it and if the edits made can be done by everyone easily, it will without a doubt get buyers, I can imagine a uel, intake manifold and an OFT tune on a 2013-2016 car would be amazing. Everyone is looking for bolt on plug and play solutions these days anyway.

Jeff: also what do you think of choosing different materials for prototypes? Plastic plenums, plastic/silicon hoses and such .. shouldn't it make much cheaper/quicker prototype turnaround (if not on-site adjustment)/requiring less work to test multiple configurations vs welded metallic one? Flexible hoses also should enable simpler testing of constructions less tied to cylinder location/manifold plenum size & shape, allowing eg. even longer runners, if one were to test longer then distance from cylinders and rigid plenum width. If some such temporary prototype of cut hoses config may show up promising, just then think of putting it into "iron", with putting extra length via extra bends, connection to back of plenum, not sides, for example.
Also .. do you still have stock resonators with your intake manifold or they are deleted? Shouldn't volume of them also be added to stock plenum volume, as it's "after" most restrictive bit, airfilter? That "reserve" probably will affect more throttle response, not flow

An alternative to the JUN IM is what I'm seeking. But rationality an extrude honed MY17 IM was my future choice.

I like the method you all are using however searching for gains in the torque dip was something even oem could never fix. Going catless with a UEL or 4-2-1 header solves this.

The potential buyer who is looking for a IM already has a catless header and tuning software of some sort. Without running a catless header your setup isnt close to representative of potential costumers who all do.

Your results will get even more interesting testing as a typical tuned system.

Any plans to test this with forced induction upon completion? I'd be interested to see the results, and the ease of access to the intake ports would make resolving vacuum leaks there much easier..
Looks extreme, it's shiny, let's do it.

Good research!

:thumbsup:



humfrz

I have nothing constructive to say other than I love the dinosaurs on the graphs. :D