New ITB (Independent Throttle Bodies) ASM Kit for the NSX

[RYU]

I collected a set of questions from the social platforms regarding my 1+yr R&D effort with [MENTION=20830]A.S. Motorsport[/MENTION]s for this ground-up ITB kit. I would consider this a 90% "no compromise" ITB setup in terms of race and street friendliness. We solved some key drivability problems that can plague ITBs on street cars. This is in long form format with lots of nerdy conversation and technical concepts.

Happy to answer any questions here. There are still a lot of key aspects I didn't talk about. Let's discuss!

https://youtu.be/mODPROKLxzQ

 

[Honcho]

Great video- I appreciate you taking the time to discuss all of these little issues in detail, since that is where a lot of ITB projects fail. I'm really glad to see you've got it mostly worked out, Regan. I know how much effort and time you put into it. One thought- maybe you hold off on the dyno until the airbox is done? I bet it will affect airflow into the trumpets.

 

[RYU]

You're right about postponing the dyno. TBH i'm pretty happy with the way it drives the dyno tune is just icing on the cake and it will simply satisfy some curiosities I have. However, I understand that's what most people care about.

Ideally I wanted to dyno these different scenarios.
* No trumpets
* Short Trumpets
* Curved Trumpets (what I have now)
* Long Trumpets
* With and Without Airbox

I'm not sure how much patience i'll have to go through all these different configurations while strapped to a dyno but we'll see...

Thanks for the input!

 

[docjohn]

Nice plan...I say short trumpets no box will yield highest HP

 

[TigerNSX]

That was super informative and detailed. Thank you so much for sharing your insights and expertise.

 

[RYU]

Maybe yes. Maybe no. Dyno will tell for sure. This is a great read on bellmouth design if you want to get nerdy. Fairly short read but it's why my 3D printed trumpets are shaped as such.
http://www.profblairandassociates.com/pdfs/RET_Bellmouth_Sept.pdf

Nice plan...I say short trumpets no box will yield highest HP

 

[BBVNSX]

Great Video! Lots of good information there! Thanks for sharing!

 

[Ponyboy]

Love the vid, [MENTION=20915]RYU[/MENTION]! Great information and discusses a lot of the issues that prospective owners need to think about. FWIW, I gained 33rwhp when switching to the SOS ITB system from the stock single manifold (note: mine is a 3.6L though). So about a 10% increase in peak hp. Of course, ymmv but that's probably a good threshold to consider.

I think you're going to be making a lot of improvements in the drivability and real world practicality of ITB systems. Looking forward to seeing how you progress. Again, well done!

 

[RYU]

[MENTION=4055]Ponyboy[/MENTION] thanks so much for all your help over the years. you're my inspiration man!

 

[RYU]

Here's a good video just uploaded by HPA regarding using dual injectors. It's like he read my mind.
https://youtu.be/qppERtbMxsI

 

[shingli2k]

Great video.

I think you mentioned your tuning setup but what makes you not want to go full standalone?

 

[RYU]

Great video.

I think you mentioned your tuning setup but what makes you not want to go full standalone?

Hi! I'm on the HKS F-Con VPro is a standalone. I do have it still plugged in because it controls a few minor things like cooling fan control and VVIS opening (which is no longer being used).

 

[shingli2k]

Thanks. Wasn't familiar with the HKS and thought it was still utilizing the stock ECM.

 

[RYU]

Thanks. Wasn't familiar with the HKS and thought it was still utilizing the stock ECM.

The guys are doing amazing work here with the stock ECM http://www.nsxprime.com/forum/showthread.php/211416-Tuning-the-NSX-3-0L-Using-the-OEM-ECU

However, I believe the stock ECU heavily relies on the MAP sensor. I'm not sure if the stock ECU can be configured for TPS (Alpha N), I believe it can? Perhaps @Honcho, @MotorMouth93, or [MENTION=7151]mskrotzki[/MENTION]might know?

I configured my HKS to primarily run Alpha N with MAP as a compensation table. The MAP/vacuum signal alone in an ITB setup is not good enough to run primarily off MAP.

 

[Honcho]

However, I believe the stock ECU heavily relies on the MAP sensor. I'm not sure if the stock ECU can be configured for TPS (Alpha N), I believe it can? Perhaps @Honcho, @MotorMouth93, or [MENTION=7151]mskrotzki[/MENTION]might know?

It can. John knows the details.

 

[RYU]

Yes! i thought I remembered that discussion. Excellent!

It can. John knows the details.

 

[RYU]

I figured I'd give these annoying nsxprime mods a break and not post a new thread... oh wait...

https://youtu.be/WrW7uhPphw8

I'll update my build thread on the tuning exercises we did for this go-around. In a nutshell, i'm pretty happy with drivability. Only one more ECU tuning exercise left - dyno cleanup tuning when airbox is done.

 

[Honcho]

I figured I'd give these annoying nsxprime mods a break and not post a new thread... oh wait...

https://youtu.be/WrW7uhPphw8

I'll update my build thread on the tuning exercises we did for this go-around. In a nutshell, i'm pretty happy with drivability. Only one more ECU tuning exercise left - dyno cleanup tuning when airbox is done.

This is one of the most exciting things on Prime right now- congrats!

 

[furinax]

Awesome thread! I'll watch the video when I get the chance, but the clips sound great! Are you planning on getting an airbox?

I remember meeting Adnan 2 years ago. Great guy- has passion for the car like us enthusiasts.

EDIT: just saw it. Looks like you have an airbox solution planned. I am looking forward to what you come up with. It would be really great to maintain the type-R engine cover for those who want to fit an airbox on. I really like the Kakimoto one but I doubt that one fits under the standard maintenance lid.

 

[docjohn]

Sweet..its like I'm back in 1994 drooling at all the JDM vids of the wild ITB cars...one of the reasons I went GTLW (gym/tan/laundry/waaaaaappp) with test pipes...

 

[RYU]

Thanks guys! The project has certainly renewed my interest in the car and has helped taper some of that Covid boredom (i.e. depression for some!). I'll spend a few mins today updating my build thread if any cares to hear the details.

 

[A.S. Motorsport]

Ultra late to chime in on this, I've been swamped with projects in the shop and all "engagements & updates" done via Facebook & Instagram, a utter-shame as i heavily prefer the forum as a data-bank.
OK so a addition to all of the above.

Firstly!
RYU has been instrumental during R&D that first and foremost also we've gone trough so many updates and intricacies i won't even bore people with.

The idea and sketches for a street ITB kit have been around here in the shop for many years I just never-had the time to start with them until late late 2019
Let me elaborate on the why's and what's in the design layout.

Key point overview:

• Modular design
  • Parts used tap into existing frameworks for cost reduction and make tuning simpler
    • OEM Honda fuel rails and FPR retained
      • this will allow OEM hardware to be reused, OE equipment such as FPR is retained
    • Existing NSX Fuel-injector options retained
      • The fuel rail mounts are infinitely adjustable in height
    • Largest selection off the shelf trumpets
      • All Jenvey flange trumpets fit given they are not wider than 100mm (due to cylinder spacing)
  • The setup is designed so that existing ITB users can easily upgrade to my design
    • Hayward & SOS
    • This did make certain features of the prototype sketches disappear
  • It's designed with tolerance and wall thicknesses so that forced induction won't be a issue
    • the 45 degree off cylinder design make for a flat flange the billet's are more than thick enough to handle boost, big reasoning behind this is so you can bolt on a turbo plenum.
  • Simplified airbox flange
    • see above, it make a NA box easier too.

• OEM Style injector placement
  • This is one of the huge improvement points over all other available ITB kits, be using port injection angled towards the intake valves we can ensure
    • Maximum spray length > fuel cloud directs towards intake valve as to give the most time for incoming air charge to mix generating proper low speed AFR
    • Incoming air has more time to stabilize after the throttle blade (smoother flow)
  • Traditional NSX ITB kits used off the shelf injector placement in Jenvey throttles this is rather crude as it forces fuel charge on to the back of the intake runner, causing low speed fuel pooling in the runners (and diagonally in the narrowest portion!)

• Tune ability especially torque power-band
  • ​This is the other reason for the 45 degree offset from cylinder, it give you a flat plane up until the hatch for limitless runner tuning and airbox design.
  • 48-54mm throttle size range is larger than any other ITB kit (most are ether 48 or 50, RYU is running 50's, we have a number at 48 and Christian/ATR is running custom 54mm)
  • Total length, due to the flange layout and the offset very very long runners can now be done so a engine builder/tuner can actually get a ideal runner length for a given cam setup. (That inherently allows for good airspeed)
  • 12 injector version, two possibilities
    • Throttle mounted injectors for high RPM those where featured on facebook last year.
    • Velocity-stack mounted, the most effective way for very high RPM engines, like a F1 car

• Progressive throttle linkage
  • On the mechanical throttle setup we spent a lot of time making a progressive nonlinear curve, this to mimic what Honda did on the 90-94 throttle body, so your low rpm and low speed throttle control is much improved (parking, etc)
  • It's designed in such away the progressive portion can be replaced in future to accommodate customization in curves
    • A number of adjuster holes are provided in all sides of the linkages to accommodate any special needs
  • Throttle springs, this came up after testing at RYU's first runs we spec kits with special jenvey throttle springs to retain OEM feel.
  • Ball bearings all way round, this to eliminate the flimsy setup Hayward throttles have
    • My ideal design would have used spherical bearings and a custom throttle cable, and billet actuator levers, as you can imagine that would have tremendously increased cost and labor for any install

• Billet construction
  • To ensure highest possible fit finish and standard, the whole runner is a solid billet 5 axis machined piece, off course this does cost tremendously more but in my opinion this is one of the defining features and allows for a lot of intricacies
    • Every design modification had a number of 3D print stages (cutaway flange, cutaway vertical, full size) as to make sure the port match is as best we can.
      • interesting thing came up, the head castings differ we had to average the fitment a set of manifolds was made so perfectly matched to one specific head they didn't match 3 other heads
  • Not only is it finished in a mirror finish the inner runner is machined in length wise 5 axis passes with the air flow direction in mind!!

• Vacuum system
  • The kits come with a 8 port vacuum manifold, this is a CNC machined extrusion.
    • each runner has a dedicated vacuum port feeding in to a vacuum plenum intended to collect and buffer all cylinders
    • MAP sensor taps into the end of this gallery so you have a steady map signal for part throttle of all 6 cylinders! (so you can actually get smooth operation and some fuel economy at part throttle and cruise!)
    • FPR attaches to this "vacuum manifold" so the OEM FPR still functions as Honda designed it with port pressure compensation, so your fuel pressure is always relative of inlet manifold pressure
    • 2 large ports, one is intended for IACV input the other for brake booster output (we recommend a OE off the shelf electric vacuum booster pump, this is a far superior method)

Detail pictures

Port fitment cutaway

Prototype cutaway featuring 12 injectors > this is the in throttle placement version, also clearly shows how we position injectors to give the best possible spray pattern

The inner runner machining paths of the 5 axis as described above:

A kit prior to shipment, the linkage and vacuum manifolds clearly visible

Prior to shipping kits are assembled on a C30A, note how the OEM fuel rails and FPR install seamlessly

Modular design in lengths exemplified by these full billet trumpets on a kit prior to being shipped out to HQ Engineering

 

[RYU]

I couldn't have articulated it anywhere near as well as [MENTION=20830]A.S. Motorsport[/MENTION]. I'm the forever tinkerer so of course there are still a few areas i'd like to improve but i'm very happy with the setup thus far. This could definitely be the forever setup for me. Overall, this setup has worked out surprinsingly well. The drama is fantastic.

Be sure to check out [MENTION=33247]MotorMouth93[/MENTION] 's thread. He's making huge strides using the factory ECU to run off the ASM ITB setup.

Here's my airbox solution for those interested.

Without the plenum

 

[BBVNSX]

Great writup on the ITB's thanks! I have one questions for you guys, Have you ever measured the power changes between using airbox with fresh air from the side vent, and no airbox at all, with airfilters on the top of the velocity stack like the ones from Toda? here:

Wondering what would that mean in terms of performance... Also any other reason to go airbox vs no airbox other than the cold air intake? (noise?)

 

[RYU]

Great writup on the ITB's thanks! I have one questions for you guys, Have you ever measured the power changes between using airbox with fresh air from the side vent, and no airbox at all, with airfilters on the top of the velocity stack like the ones from Toda? here:

Wondering what would that mean in terms of performance... Also any other reason to go airbox vs no airbox other than the cold air intake? (noise?)

I'll attempt to answer.

Airbox vs. No Airbox is actually rather difficult to measure in real life. Yes, you can measure it in the dyno but even then that's not real life. I have noticed the main differences between running a plenum vs. not are in two areas.

1. The biggest difference is Intake Air Temperatures. With the plenum my IAT is at least 5-10F degrees cooler than ambient. Without the airbox it's at least 10-15F higher than ambient and gets worse with heatsoak. That has some affect to power as I can notice it in the throttle pedal. How much? I don't know exactly as you can only get these affects when the car is in motion. Check my build thread for how I ducted the air flow from the driver's side duct into the K&N dual cone filters that feed the plenum into the ITBs. There's also some minor ram effect when the car is in motion which is impossible for me to measure. It's minimal though im' sure.

2. With the airbox I noticed my power band is a little lower but it's moreso a shift in optimal power on the power RPM band. I don't have a dyno to prove this yet as i'm waiting on my 3.6L to be built.

I've tried various different types of velocity stack testing. I can say that each design makes a noticeable difference. You can check out the backyard garage style videos this guy does. They're great. https://www.youtube.com/c/Garage4age

Moral of the story... running some kind of filtered plenum "airbox" is my best choice all things considered. It refines the noise, it's allows for filtered air, while reducing the power loss as much as possible.

I would also run some type of filter in the long run but those sock style filters rob the most power because it slows down the air velocity so much. Someday soon i'll do a Update video on my car and i'll explain more then.