NITROUS Hemi Zex kit and questions. [Archive] - Cherokee SRT8 Forum

: NITROUS Hemi Zex kit and questions.

06-10-2007, 11:16 AM
Ok. Some issue's, thoughts, and questions that I've run into with the Zex nitrous kit 82176 so far. These problems happen both on my wanabe SRT-8 5.7 Jeep, and my father's real SRT-8 Jeep. My upgrades are far and many so I'll be brief. CAI, headers, full exhaust system, 75 shot zex nitrous hemi kit, factory fuel rails and injectors and pump.

No check engine lights... thank god and so far no blown engine. lol

1.) Engine / Fuel Issue. The computer has to "learn" the new air, fuel, and nitrous mixture that goes into the intake manifold and engine when spraying. This increase in fuel pressure and levels in the engine at times creates excessive vibration and then levels out back to normal. The primary issue is that once the computer learns the new mixtures it expects to have it all the time. For example start the truck and let her warm up, go for a dry run, and two or three runs with nitrous. Then go to lunch, as I'm sitting in the parking lot the truck's idle fluctuates up and then down once or twice and then the truck stalls out. I can fix this problem by giving a little bit of gas when it drops off but I don't want to have to do that. Now could this be a fuel filter and or fuel pump pressure issue? It doesn’t do it all the time, only after two or three really hard runs. If there is any way to combat this fuel issue as I can't think of what else it could be, either by upgrading the pump or using a new fuel and or air filter, are there any suggestions?

2.) Bottle issue. I have a pressure gauge at the bottle from Zex, and one in the A Pillar pod now, that's all swell as long as the bottle is open and ready, but my biggest problem is I don't know when the bottle is empty. I don't want to do a run and have the improper fuel or nitrous mixture and possibly blow or damage my engine, even though the Zex kit prevents misfiring like this I like to cover all the bases just in case the system fails to cut off or cuts off too late. Other than trying to count the runs and purges I do, I wanted to know if there is any way of knowing inside the vehicle when a nitrous bottle is empty other than un hooking it, taking the straps off and weighing the bottle by hand.

3.) Launch / Usage issue. When using the nitrous, when is the most effective time and or safest way to use the kit and nitrous, rather when is the best time to enable the system to spray on open throttle. Example, after first gear or shift, or before.

4.) Computer / Programming Issue. It is my understanding that the Jeeps with the HEMI engines and other similar equipped vehicles do not have full open throttle till around or after second gear. If this is so then the full open throttle nitrous setup only hits after second gear or a hard whomp on the throttle. So there are either three ways to combat this, please let me know what you think.

Either change the system to manually firing of nitrous, or when programming the throttle body's position to the Zex's computer or programmer only open the throttle body 3/4 of the way so the Zex computer think that that is full throttle. This way the system will inject nitrous at 3/4 to full throttle instead of just full throttle.

5.) Reflashing / Chip / Programming Issue. Can you run the JET stage 2 chip with the nitrous system safely? If so great, if not, any suggestions for upgrading the stock computer / ECM / ECU. Some one recommended having the computer flashed with the police package HEMI software rather than sending the computer to someone.

6.) Engine Oil / Filter issue. The 5.7 Hemi's are required running 5W-20 oils, daily, but for a nitrous set up is it possible to run thicker oil for the summer to reduce friction and wear as much as possible? I am currently using Amsoil high grade synthetics but I want to go to Mobil 1 but with a thicker viscosity. Any ideas or suggestions.

Thanks so much for your time and help with these issues. I figured I'd get them out there and see who knows what and share and exchange information. Any and all help will be greatly appreciated.

06-11-2007, 09:34 AM
...some quick responses for you, from my experience.

to be extra safe, install some iridium 6ix NGK plugs.

If you just spray fuel (ie bottle empty or very low) you won't really hurt
anything, it will just run pig rich, while you are spraying.

With a 75 shot, you should get about 8 good "passes" and 4 fading out.
Best way to determine how much NOS is left. Weigh bottle. ...but generally
keep track of the shots you use. You best shots will definately be your first

I spray mine with a hand held button, b/c I don't want it "spraying" through
the shifts. I may spray the whole way, once a tune is had, and tranny
firmness and consistency are addressed.

I thought the Zex system, sorta optimized your nitrous for best consistency
etc, based on bottle pressure and other stuff?

I wouldn't mess with oil viscosity based on nitrous???????? Oil & filter really
don't have much to do with whether you spray it or not. I do recommend
changing oil religiously if you are like me and run the heck out of stuff on a
regular basis.

Rule 1 for me is don't over think the nitrous, it's not that complicated.

Launching.....I don't brake torque my Jeep at the track.
I rest foot on brake and gas.......when I slam accelerator to the floor, I
then push button as soon as the truck lurches forward. I have tried hitting
the juice almost simutaneously as when I floored it, only to have the right
rear tire and front left tire burn.

As for PCM, or flash from my understanding, the truck's
computer somewhat adjusts for the nitrous hit, torque increase, fuel maps etc.....but
I don't recommend having a tune on the ragged edge and spraying it with
more than a 100hp shot, b/c a flashed computers timing may be too high
to be considered safe? make sense?

I also haven't had any issues with the SRT8 Jeep learning too much, or
adjusting too much and altering the computer control too much??????
I have put about 4 bottles total through my Hemi and have had no problems.
I may up the shot to 110-120 soon. The 75 is great, but I think I am real
safe, and the ET potential with another 40-50 seems to be good, if I can
use the power ASAP without tire shredding single wheel peels.

To get the most ET out of any nitrous application, you need to spray the
vehicle at the earliest point on the track. (Example) you could spray it from
half track to the finish only, and only pick up about 2 tenths, 2 mph max,
however all things being equal, if you sprayed for just the 1st half of the track
you would pick up almost double that????????? You make all of your time
down low!

I am anxiously waiting for a Predator or another hand held tuner, but I feel
like I will have to break down and get the B&G if I want it sometime before

I know 11s are going to be had with either 30* weather and good traction, or
with a tune and good traction.

Goodluck, and I will try an answer any thoughts you have.

I have a simple 1999 wet Nitrous Works kit on my Jeep, and it is probably
a hair rich with the Jeeps 50psi operating fuel pressure. I would rather be
safe then sorry with this vehicle though.