I just re-tuned my nitrous CRX for the 2010 racing season and as always had a lot of fun doing it. The CRX
still has an internally stock motor and I am starting my fourth season spraying on it.
My Nitrous System
I have tried many nitrous systems and while all are capable of giving you fantastic results, I personally prefer
ZEX wet systems. The superb quality of these systems, the consistency of spraying nitrous and fuel
simultaneously from each nozzle, and the ease of installation are the reasons for my preference.
For this testing, I used a dual stage ZEX wet system, consisting of a direct port kit and a ZEX add-a-stage kit.
http://www.zex.com/Pages/126/Wet%204%20Cylinder%20Direct%20Port.aspx
http://www.zex.com/Pages/29/Add-A-Stage%20Nitrous%20Kits.aspx
I use bottle heaters, pressure regulators, nitrous gauges, blow down kits, and purge kits. The reason is
simple: when using nitrous, you have to triple check the components and condition of your system to ensure
that everything is operating safely.
Please see the Resources section below for the web addresses of all popular nitrous kit manufacturers.
Please see below for the videos, spraying both the 75 shot and 150 shot on the dyno.
The key to my installation is that everything is within reach; in my opinion, a stealth look is nice, but too
difficult to work on. I have learned that a nitrous installation which is easy to get to helps tremendously when
having to change jets regularly, doing maintenance, checking connections, inspecting solenoids, and
making sure all lines are leak free. Whether at the garage or at the track, you have to constantly inspect
your nitrous system to be able to keep it in perfect shape and safe.
Engine Specifications:
K24A1 shortblock
OEM sleeves
K24A1 crankshaft
K20A2 crankshaft pulley
K24A2 (TSX) pistons and rods
ACL bearings (Calico Coatings)
K20Z3 oil pan
K24A1 oil pump
K20A2 head
K24A1 head gasket
OEM head bolts
All OEM internals
NGK BKR8EIX spark plugs
Bolt-ons:
- PRB intake manifold
- Hondata intake manifold gasket
- Intake manifold expansion chamber
- PRB throttle body bored to 70mm with port matching on the manifold
- Custom short ram intake tube with a Blox velocity stack
- Six Sigma Racing stainless headers
- open exhaust
Car:
1989 CRX HF
weight: 1,935 lbs. (without driver)
not street legal
Chassis Dyno Used:
Brand: Dyno Dynamics
Model: 450
Type: magnetic eddy current retarder
Dyno Results:
All-Motor - 201 whp and 169 ftq
75 shot - 262 whp and 235 ftq
150 shot - 325 whp and 282 ftq
Please see below for the dyno charts.
Tuning Specifications:
Base ignition at WOT all-motor: 27-30 degrees
75 shot - 4 degrees ignition retard
150 shot - 10 degrees ignition retard
Fuel used for all dyno testing: Sunoco unleaded 110 octane
Fuel added for nitrous at WOT (besides what the wet nozzle already blends in):
75 shot 30% down to 13% additional fuel
150 shot 50% down to 38% additional fuel
Air/Fuel Ratios:
All-Motor 13.2 – 13.4:1
75 shot 12.6 – 12.8:1
150 shot 11.6 - 11.8:1
iVTEC cross-over is set at 3,600 rpm, while nitrous activation begins at 4,000 rpm. This is intentional to allow
the motor enough time to wind-up on the high cam lobes, before starting to spray. With stock K20A2
camshafts it is very easy to tune out most of the loss in torque when setting the iVTEC cross-over earlier
than what is optimal. An additional reason for switching early is to maximize acceleration, since this is drag
racing application.
I wired both kits in to the Hondata KPro ecu, using Hondata’s wiring diagram.
http://www.hondata.com/techkpronitrousdiagram.html
Hondata's KManager software is used for nitrous activation and control of the nitrous.
Note that for the first stage, the vehicle speed settings range from 6 to 24 mph. When I make my first passes
at the track, I am dialing in what works best with every consecutive pass. These settings will depend on track
conditions, weather conditions, launch control settings, and how my car is hooking from gear to gear.
I test until I find the mph that will give me all-motor or a little nitrous in 1st gear, the small nitrous shot in 2nd
gear, and the large nitrous shot in 3rd and 4th gear.
For the second stage vehicle speed settings are 25 mph and up, in this example. Testing at the track
determines the best settings for the car and the conditions.
Note, I have set my nitrous operating range at a maximum rpm of 7,500. All-motor, I rev this motor up to
8,000 rpm. I do not do this when spraying; after all, it is a 100% internally stock motor. Being conservative in
this respect is not a bad thing!
Nitrous Jets Used:
Here are the nitrous jets that I used during the testing. Note that these are what is applicable for the ZEX wet
systems I used. Other manufacturer’s kits use slightly different jet sizes and numbering methods.
75 wet nozzle -
0.043 nitrous jet and 0.021 fuel jet
150 direct port -
0.054 nitrous jet and 0.019 fuel jet
0.067 distribution block nitrous jet and 0.033 fuel jet
Web addresses for popular nitrous kits manufacturers:
Zex - http://www.zex.com/
Holley NOS – http://www.holley.com/Categories.asp
Nitrous Express – http://www.nitrousexpress.com/
Dyno Tune - http://www.dynotunenitrous.com/store/scripts/default.asp
Edelbrock - http://www.edelbrock.com/sportcompact_new/mc/nitrous/ns_fandb.shtml
Nitrous Outlet - http://www.nitrousoutlet.com/index.asp
Ny-Trex - http://www.ny-trex.com/
Venom - http://www.venom-performance.com/index.php
Warning – Focus on safety:
You should always dial in your nitrous motor on a dyno, tuned by an experienced dyno professional. If you
do not carefully tune your air/fuel ratios and ignition, you will have problems, up to and including destroying
your motor!
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