RDX Injector Fitment Improvement

Greetings to All,
First off I would like say "Hats Off" to Brian at ProSpeed for the much needed improvement to the NSX injector. Most people don't realize how much time it takes to do all of the research and development for something like this. Thanks Brian and the others that helped you.

About a year ago, I started installing my RDX Injector Mod. During the installation of the RDX injectors into my NSX intake I noticed that the RDX injector seals into the injector pocket in a much different way from the original injector. The more I looked at it the more I saw what I thought would be an improvement to the sealing of this modern day injector into the injector pocket.

Well a year later I have finally picked up the parts from the CNC machine shop. As with every great idea that has positives there comes disadvantages. SO, lets get the disadvantages out in the open. YOU HAVE TO REMOVE THE INTAKE.......there it's out, but with this disadvantage comes advantages, you get to clean it. You may be surprised how dirty it really is.

After removing the intake and spending some time cleaning it comes the easy part. I made a drill guide that fits into the injector pocket to align the drill bit to enlarge the hole to fit the RDX injector. Drill all six holes carefully cleaning any shavings when you get done. Then, reinstall the intake with new gaskets. Remove the O-ring off of each of the RDX injector tips and install the fitted spacer and replace the O-ring. Install the fitted fuel rail spacers, the injectors and fuel rails. That was a nice day spent in the garage with the NSX.

And the OEM injectors will still fit if you want to go back to the dark ages.....just saying.


Take a look at my pictures and see what you think.

Brad

Love the innovation Brad. How much larger is the hole drilled to?

It is 14mm. I had to purchase a RDX intake runner to get the dimensions of the injector pocket before I got started having the parts made.

RDX Fitment

Here are a few pictures to show the fitment of the RDX injector into the smaller NSX injector pocket hole and the enlarged hole.

The piece of black plastic with the two holes shows the very small difference, about 1mm, from the NSX injector pocket hole and the RDX hole. (sorry about the shadow from my iPhone taking the picture) I used this piece of plastic to demonstrate the two different methods of how the o-ring seals on the two different size holes, one on the top edge of the hole and the other down in the hole. The o-ring seal is the only thing holding the injector in place with the enlarged hole. I also enclosed the RDX injector intake part with RDX injector installed to show how the OEM injector pocket was designed.

Brad

Gotta love Prime. Someone takes the time to improve on an improvement.
Fantastic job.

Brad is Handy!

Gentlemen,
Thanks for the kind words.

I do have some extra kits if anyone is interested PLEASE send me a PM.
BRAD

Brad, those CNC machined spacers look great!

I wanted to upload some pictures of how the RDX injectors sit in an NSX intake manifold but unfortunately, it seems pictures can no longer be uploaded to the NSX Prime Owner's Gallery. In any case, as you wrote, RDX injectors seal differently than NSX injectors do. Perhaps by dumb luck, the sealing O-ring of an RDX injector has about the same outer diameter as an NSX injector. So as ProSpeed recommends, you can stick an RDX injector including its O-ring into the sealing ring of an NSX injector and then stick the lot into the injector pocket of an NSX intake manifold. It should seal properly. However, like that you have two seals where you'd prefer having just one and an additional mating surface that could potentially cause problems.

Given the shape of an NSX sealing ring and an RDX injector, there's nothing physically preventing the NSX sealing ring from slipping up off the RDX O-ring and breaking the seal. Perhaps the vacuum in the manifold at part throttle will keep the NSX sealing ring sucked down and seated safely despite the vibrations.

To eliminate that potential source of problems, one solution is to drill out the hole in the base of an NSX injector pocket as Brad described so that the OEM RDX O-ring seals as it was designed to, directly against the intake manifold. Another solution would be to get rid of the OEM RDX O-ring and OEM NSX sealing ring completely and replace both with one custom RDX to NSX adapter seal. Either way, then you'd be sure there's no air leak between the RDX injector and the NSX intake manifold.

My installation is COMPLETED! I am very pleased with the whole installation. Performance seems to be improved. My next step is back to the same dyno for some post modification pulls. That is the only way to really compare apples to apples.

I do have some pictures that I will post showing how dirty the intake, all the way into the intake ports, was. It was very easy to clean the intake ports in the heads after removing the intake. The intake is very easy to clean after removal and separating the VVIS from the intake. Pictures to follow.
Brad

Here is the gasket list that I used:
17167-PR7-A00
17105-PR7-A01 2 ea ( I used ProSpeed custom insulating gaskets, not sure if they are still available)
91303-PK2-005
17142-PR7-A01
17141-PR7-A01
36455-PT3-A01
16077-PR3-005
91304-PE2-005
90428-PD6-003 2 ea for each fuel line connection that you disassemble
18721-PR7-A01 2ea

If you need a ZIF socket for your ECU here is a source. http://www.hamotorsports.com/zifsocket.html

My experience with this mod. 1st of all, if you are using Prospeed RDX kit, this mod is a must. The parts Brad supplies are top quality. He even supplies a drill bit and guide to prevent drilling issues. Great extra service. The mod has made my 91 run smoother throughout the RPM range. The car pulls better throughout the RPM range. Drivability in traffic and highway is a pleasure, since the power band is so smooth. lI ove to redline it when the opportunity is there. Thanks Brad.

I purchased a prepped intake manifold from Brad and finally have it installed on my car. He is a pleasure to deal with and his work is excellent. This mod is a must for anyone wanting more HP for cheap. Thanks Brad for all the help!! We are lucky to have you on prime

I have a cleaned intake with the injector holes modified for the RDX injectors ready for anyone that would like to do an intake exchange. I charge $50 for the exchange plus round trip shipping. I am finding that $25 each way is average shipping. Let me know if you are interested.
The intake that I have works on 91-94 NSXs.

If you have an extra intake that you would like for me to modify that is fine also. I just did that for an owner. From the time I get the intake figure 5-7 days depending on my work schedule.
Brad

In addition to improved sealing, is the distance between the injector to the valves optimized such that the spray doesn't hit the sides?


Sent from my iPhone using Tapatalk

dablackgoku1234 said:

In addition to improved sealing, is the distance between the injector to the valves optimized such that the spray doesn't hit the sides?

Click to expand...

The injector is as close to the valve face as possible without extensive welding and machine work to completely rework the injector pocket.
Brad

I have the Prospeed mod and I am curious as to where the possible performance gains from this upgrade are coming from. Is it because the injectors sit deeper in the pocket so they have a better spray pattern? Interested in this.

Blackhorse06 said:

I have the Prospeed mod and I am curious as to where the possible performance gains from this upgrade are coming from. Is it because the injectors sit deeper in the pocket so they have a better spray pattern? Interested in this.

Click to expand...

Hello Blackhorse06,
The injector does sit lower in the injector pocket, about 3/32. I feel the big improvement is the way the RDX injector lower o-ring seals in the NSX intake, which is how it was designed to seal. With providing a positive seal at the injector base removes the possibility of an air leak which would cause a lean mixture condition, which is BAD.
Brad

Nice job on the improvement. Good thing I have an extra intake (or 2) laying around. I'll send you a PM.

Very satisfied with this upgrade. I had an issue with my car "choking" after this mod. I have a stage 3 with I/H/TP/E and got Brad's improved intake manifold. I contacted Brian at Prospeed power and he was very responsive and did an update on my chip. Problem solved! Car now pulls to redline smoothly. Can't say enough positive things about this mod.
Thanks Brad!!

Great improvement.....Will this help with the idling issue of the earlier tune?

My intake manifold is on its way out to see you, showing that it's currently in North Salt Lake, UT and should be delivered tomorrow! Thanks again for offering this great mod!

REDNSXT said:

Great improvement.....Will this help with the idling issue of the earlier tune?

Click to expand...

If you have any air leaks around the injectors, it very well could fix your problem. senna91 had a early ProSpeed RDX Tune and contacted Brian at ProSpeed who remapped his chip to the most current tune. senna91 seems very pleased.
I drove my car today, I am very happy the whole mod.
Brad

The following pictures may help visualize the potential sealing issue when sticking RDX injectors into an NSX intake manifold.

Here's an OEM NSX injector in an OEM NSX intake manifold:


An NSX uses a rubber sealing ring to create an airtight seal between the injector and the manifold:


The RDX injector doesn't use a sealing ring like that. Instead, it uses an o-ring to create a seal between the injector and the manifold.


The RDX injector is skinnier than an NSX injector so the NSX sealing ring won't seal against an RDX injector's body. However, by dumb luck, the outer diameter of the RDX o-ring is pretty much the same as the outer diameter of the NSX injector's metal body. As a result, you can stick the RDX injector and its green o-ring into a black NSX sealing ring.



The potential issue is that when everything is mounted in the manifold, there's nothing physically keeping the NSX sealing ring from slipping up off the RDX o-ring. An NSX injector is shaped so that that can't happen - see the first picture in this post. If you stick an RDX injector and its o-ring into an NSX sealing ring and then stick the lot into an NSX intake manifold, it can. Have a look how that combination mounts:


That seemed like an unnecessary potential source of problems to me so like Brad, I wanted to mount the more modern RDX injectors in such a way that the seal cannot break.


Just for reference, here's a skinny blue RDX injector with its fuel rail adapter on top versus an OEM NSX injector.

would you happen to have a photo of the underside of this? where the injector protrudes on the bottom side?

Yep. NSX injector in an NSX intake manifold:



RDX injector in an unmodified NSX intake manifold:

I still have a few sets of my kits available.