Custom ITBs and Nitrous Build

Joined
25 April 2005
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3,069
Location
Western PA
Didn't know where to put this - N/A or FI/Nitrous section :smile:

I've been designing and fabricating a custom ITB build using a hacked-up OEM intake manifold with slim Jenvey 50mm SFS throttle bodies.

The problem with some of the aftermarket ITB setups I've seen (besides the price markup), is that the injectors have been angled such that they are injecting the fuel cone directly onto the opposite intake runner wall. Sure, at high mass flow rates into the runner, the fuel droplets are entrained and obviously make it into the cylinders, but this is not the ideal path and can be greatly improved :rolleyes: I didn't want to inject above and below the throttle blades (for complexity reasons, although for high RPM, injecting the fuel sufficiently far away from the intake valves is beneficial).

So, the following are the design goals:

1) I live in a cold climate, drive this car a lot, and want it to idle well so this uses an aftermarket idle air control valve and the ITB blade edges are custom coated for less-leak through

2) I want the TB's as close as possible to the intake valves

3) The TB's need to be angled correctly to optimize airflow and help direct it into the ~40 degree head intake angle, yet be capable of incorporating a special surprise later (not the nitrous)

4) The injectors need to be oriented correctly

5) Keep costs and fabrication down by using a hacked-up OEM intake manifold, which also happens to preserve the ideal injector placement for design goal #4 )

6) Design linkages for simplicity and reliability

7) Incorporate an innovative air filtration system and a progressive 150 HP shot of nitrous (I have a built engine http://www.nsxprime.com/forum/showthread.php/154927-Semi-DIY-Mild-Engine-Build-for-FI)


Image showing OEM intake manifold and heads with injector angle and runner angle (marked up courtesy of Greenberet):
View attachment 163026


Compare with the injector angle for the SOS/Hayward and Toda designs :eek::
SOS Injector Angle.jpg
Toda.jpg

Now, some have correctly preserved the OEM injector placement. For example, the old Comptech builders and someone over in Japan:
comptech3.jpg
acimg1715.jpg

So, in preparation, I completed yet another iteration in my exhaust lineup optimized for N/A flow and using a vacuum-actuated bypass valve instead of my boost-actuated vales with the old turbo setup (quiet mode, low-restriction loud mode, and zero drone with a 1/4 wave resonator and all titanium piping). Took it to get a baseline N/A dyno plot, got the titanium exhaust tip hot enough to blue naturally on the dyno, and then washed it in preparation for the winter overhaul....

Peak WHP was 297. It was previously over 310, but since then I've added the heavier '02+ wheels and the BBK :frown:

More to come!

View attachment 163032


Unfortunately this is as good of a wash as it gets these days
View attachment 163033
 
Awesome! Can't wait to see what you're cooking up. Is the idea to get it to fit under the engine cover with airbox?
 
Awesome! Really interested to read about your results. IIRC, theory implies that injectors should be placed as far away from the intake valves, and as close to the butterfly as possible, to allow for adequate air/fuel mixing time. It may be a net gain in the equation but I very well could be wrong.

Either way, looking forward to seeing your system come to fruition. :thumbup:
 
Thanks.

You're right Ponyboy on the injector placement. Bisi has tuned a few neat dual injector ITB setups, but I was a bit concerned about placing the injectors too high due to the height and impact on rear visibility. That, and fire concerns. Having been through a fire in one of my racecars over 20 years ago and having to kick out the windshield to escape (even after the initial Halon suppression system discharge), I'm pretty anal about that stuff.

But to answer Honcho's question, no, I won't have an engine cover. I haven't had one installed for about 14 years actually. Again, I like being able to see into the engine bay, it's less weight up high, gives me space for stuff like ITB's, blah, blah, blah.
 
6 months later and I have it working pretty well to where I can start it on cold 45F mornings just fine, putter around town at 25 MPH with excellent throttle response, and do WOT runs to 8800 RPMs.

So, it dyno'd at 370 WHP at 8500 RPMs on 93 octane (stock intake manifold was 310 WHP but I have a custom-built engine and exhaust). With mild nitrous it is 500 WHP.

Too bad Prime isn't letting me post pictures....
 
6 months later and I have it working pretty well to where I can start it on cold 45F mornings just fine, putter around town at 25 MPH with excellent throttle response, and do WOT runs to 8800 RPMs.

So, it dyno'd at 370 WHP at 8500 RPMs on 93 octane (stock intake manifold was 310 WHP but I have a custom-built engine and exhaust). With mild nitrous it is 500 WHP.

Too bad Prime isn't letting me post pictures....

MUST. SEE. PICS!

Host them on google photos and set up a shared folder. It's what I do. Unlimited space.

What are the specs of your engine? I'm chasing 300+ whp with the stock manifold, CT cams and RDX injectors. I'm going with the 36mm intake valves after talking to Shad.
 
Need to stress-test my latest setup on the track. I removed the nitrous and have gone with variable-length intake runners based on RPM and TPS (predictive for my PI controller). I'm keeping track of the cycles because I may end up selling this ultimate ITB setup to the public. I even got to test it in the rain!

Socially distancing on the track is weird but I followed the rules:
View attachment 166724

Desperately need to go back to my vented hood and add a front underbody and splitter.
 
Mac Attack said:
Need to stress-test my latest setup on the track. I removed the nitrous and have gone with variable-length intake runners based on RPM and TPS (predictive for my PI controller). I'm keeping track of the cycles because I may end up selling this ultimate ITB setup to the public. I even got to test it in the rain!

Socially distancing on the track is weird but I followed the rules:


Desperately need to go back to my vented hood and add a front underbody and splitter.

Variable runners? Do you have an airbox? Did you mod the OEM manifolds or CNC your own? Cams? So many questions!
 
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