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*Please follow your state's requirements for installing nitrous oxide on your vehicle.
**NOS is intended for offroad use only.
***I am not responsible for any damage you may cause to your vehicle, and I am not a mechanic.
PURPOSE
The purpose of this write up is to provide a complete DIY for nitrous oxide installation for a w203 mercedes. Specifically, a Nitrous Express Proton Plus Kit is installed with a wet application.
OVERVIEW
A wet nitrous kit is used for this install. The term "wet" indicates that you tap into the shrader valve on your fuel rail in order to mix optimal amounts of fuel with nitrous. Without fuel, the nitrous would create a "lean" condition, and could cause detonation and engine damage.
An overview of the steps required for the install are as follows:
1. Bottle install and running nitrous line to engine bay from wheel well
2. Installing solenoid and relay
3. Plumbing, nitrous nozzle install
4. Wiring (Solenoid, Relay, Arming Switch, and WOT switch)
5. Testing connectings
6. Test drive
7. Other accessories
8. Notes
BOTTLE INSTALL, RUNNING NOS LINES
For the 2005 w203 sport sedan, the bottle can be mounted nicely in the wheel well. This area of the vehicle conceals the bottle, and also provides insulation from extreme temperatures.
The line from the trunk goes under the rear seats. There are two screws to remove the seats, then the line can be tucked under trim to the drivers side. NOTE: In order to get the NOS line to engine bay, go through the fuse box located on drivers side. It's a panel that opens up, and there is a hole that leads to another fuse box in the engine bay.
Bottle installed in wheel wheel, facing forward, and bottle nozzle downward. The bottle is at a 15 degree angle.
Nitrous bottle under trim, as shown,
This is the fuse box on drivers side engine bay. There is a cavity that leads into cabin which you may route the NOS line
Finger is pointing towards hole that leads into cabin
NOS line (with black split loom tubing) is not running into engine bay.
SOLENOID AND RELAY INSTALL
Two electrical switches are installed in the engine bay. The Relay is the switch tells the fuel/nitrous to function. The relay includes several wires:
GREEN: Powers the solenoid
WHITE: Ground
BLACK: Goes to (+) terminal on car's battery
RED: Goes to Wide Open Throttle Switch in cabin
BLUE: Is NOT used
The area that is next to brake fluid reservoir and above fuse box provides a good location for the relay, and the solenoid may be mounted nearby as well, as shown in pics
fuel/NOS solenoid mounted on drivers side near brake master cylinder and front shock
Notice the carbon fiber material that is on the solenoid, in order to conceal
Mess of wires coming from relay, which is hard to see in the photo., but recall green goes to solenoid, red to battery, white ground, and blue is NOT used
PLUMBING, NITROUS NOZZLE INSTALL
The solenoid direct fuel and NOS going in, and going out. When system is armed, and WOT depressed, solenoid opens and NOS/fuel mixture goes into engine.
In order to access the fuel line, just go to the schrader value on the fuel rail. It looks just like a valve on a tire and is next to the oil fill cap. Open it with car off and remove the valve stem with a valve stem removal tool. DO NOT skip this step, since leaving the valve stem would not allow fuel to mix with NOS and create a potential damaging situation for engine. Have a shop rag present, as some fuel will shoot out.
Use the 4AN type fitting and screw it on and screw to solenoid. On the solenoid, use blue locktight threadsealer so there will be no leaks. This is very important, otherwise you could have fuel or nos leaks in engine bay!!
Next mount the NOS/Fuel nozzle. I emailed Nitrous express, and they agreed the air intake just before the throttle body and supercharger is optimal placement.
Take out the tubing as seen in the photos, and drill appropriate sized hole with nozzle facing throttle body. Use blue locktight on nozzle, screw in, and attach the fuel and NOS fittings.
Nitrous Express confirmed that this is the correct locatin to install nozzle
Here is the tube
Throttle body
Blue print of where to install nozzle
The line that taps into schrader valve on fuel rail to access fuel, Just lift engine cover.
Nozzle installed
WIRING
The solenoid has two pairs of wires connected. Once pair of wires goes to the green wire on the solenoid, and the other goes to a ground. Each pair of wires has heat shrink tubing. Since it is a solenoid, it does not matter which pair of wires you use for power or ground.
Inside the cabin, the red wire goes to the WOT switch, which is designed to open the solenoid when you fully depress the gas pedal. It is tricky to mount the WOT switch. Just find a way to mount it with zip ties so that it depresses when foot goes down.
The another wire goes from the WOT switch to the arming switch. I drilled about a 3/4" hole to the right of the fuse box and used a fuse tap to access power. For a ground wire, I ran a wire into the engine bay.
As seen above, the a fuse tap was used to access power in the fuse box on the drivers side interior panel. For the arming switch, the gold prong is ground, middle goes to WOT switch, and other prong to 12V source.
TESTING CONNECTIONS
Do not start the car, but turn to the key to the "on" position. Press the arming switch, and depress your pedal to activate the WOT switch. You should hear an audible click. If you do not hear a click, check your wiring. In my case, I forgot several ground wires.
The next step open the NOS bottle (car off). Listen for leaks. Your 4AN fittings should be fine, but if you forget to put blue locktight on solenoid fittings, you are likely to have a leak.
TEST DRIVE
Open bottle, turn on car, and arm the system. Depress gas pedal to full throttle, listen for denotation. I used a 35 lb shot, as advised by Nitrous Express and my tuner Eurocharged. Since I already have an aggressive tune, they did not recommend going higher than 35 lbs.
On my initial test drive I could not initially detect the additional power. But then I turned off the arming switch, and turned it on again at full throttle. THEN I felt the additional power. A 35 lb shot is a nice increase on a 1.8L engine, but it is not like the movies. You will not see streaking lights and get vision blurred. It just pushes you back in the seat a bit more and is fun.
OTHER ACCESSORIES
There are several accessories you can buy for your NOS system. I decided to buy them all. First, a nitrous kill switch (~$75) can be used in case fuel pressure drops in order to avoid engine damage. If fuel pressure drops below a specified PSI, the nitrous is cut off. The kill switch is connected to white wire on nitrous relay.
A remote bottle opener can also be installed to open bottle (~$275) from the cabin. I considered this a must, as it would be no fun to walk around to my tire well to open the bottle. Heating the bottle from the cabin with a bottle heater (~$250), allows bottle pressure to get to the optimal 950 PSI to facilitate optimal performance. Purging nitrous with a solenoid (~$115) not only looks cool, but also clears the line so NOS kicks in all at once.
OTHER NOTES
I want to thank Jarrod and Chris for help with the install. Nitrous Express has a hotline where you can call business hours with questions.
perfect post.I bought my unit used off ebay for $250,best place to look.One guy had a 4 cyling w124 he ran 100 shot all the time.
Hey Buddy, thanks for the post. Did your friend retard timing, or use colder plugs? Since I already have an aggressive tune, with advanced timing, I fear predetonation if I go greater than a 35 lb shot. Do you retard timing on your set up?
now most people only use nitrous on forced induction cars,that have a turbo.For quicker spool up for 1st gear.with my automatic I keep one foot hard on brake,and raised rpms to 2000.then launch at last yellow light,holding button all the way thru shift changes.My car when stock was 17.5 nitrous got her to 14.6 in the 1/4
Well I just spoke with a technician at NGK spark plugs. Her name was Leyla and she was very nice. She suggested that with a 50 shot of NOS, a 1 step reduction for a street car would be sufficient. She also explained that a 1 step reduction is 200 degrees cooler. If I am to keep my plugs carbon free, I'll need to keep my RPMs up. I can do that :-))
09-20-2016, 02:03 PM
