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Discussion Starter #1
I have a question about the 'smart box' for the Zex Dry kits. When the box changes the fuel delivered, is it based on the amount of nitrous that is running through, or simply which jet you have in the line (fuel jet)? When I dynoed, we ran the 75 shot and my A/F was pretty a pretty steady 12:1 from 3700 to 4400 RPMs and then dropped significantly to about 10:1 from 4600 to 5400 RPMs, with a few slight bumps up to 11:1. This was with the recommended 43 fuel jet.

The day we did this, my bottle was a bit cold and I didn't have a heater on it. We then switched the fuel jets around and used a 46 which seemed to do a bit better, with the A/F at 12:1 from 3600 RPMs to 4400 RPMs and then dropped to about 10:1 from there out.

Then we used the 38 jet, which was pretty much 10:1 all the way through.

The tune is set up to run a 12:1 A/F on the juice, but the best graph we came out with was the one with the 46 jet.

If the box is dependent on the amount of nitrous that is run through, the A/F shouldn't change...correct? But if it's not, and I have a higher amount of nitrous coming through, the A/F should bump back up a little...correct?

I'm concerned with the iffy A/F that if I bump it up to the 100, something's not going to like it and I'm going to hear a slight bang...

And, I know the optimum A/F in this case would be the 12:1, but how bad is it that it dips to 10:1?? I think this is my major concern.

Thanks

Joe
 

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West Virginia Chapter Director /, MA Drag Race Te
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The ZEX kit has a selonoid that measures bottle PRESSURE. Based on that bottle pressure it determines how much fuel/vacuum to feed the engine. It also has a jet to help control the fuel. Running the correct bottle pressure is very important on this system.

My car's dyno was nearly a flat 11.9-12.1 on the 350HP and 503 Lbs ft torque spin on the rollers. It seems to hold pretty steady. "J" even commented on the system holding the ratio's very well.

Sounds to me like your car is going rich then going lean. Could be a problem in the fuel system, not enough pump or regulator not doing its job as well as anything the kit could be doing. You should have some variation at "Tip in" but it should level and pretty much hold after that. If its not then somethings probably awry.

Check things out and be safe with it. :)
 

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Discussion Starter #4
1MTNCAT said:
The ZEX kit has a selonoid that measures bottle PRESSURE. Based on that bottle pressure it determines how much fuel/vacuum to feed the engine. It also has a jet to help control the fuel. Running the correct bottle pressure is very important on this system.
That answers my question perfectly. I don't know the pressure of the bottle when it was dynoed, but I know it was no where close to 900 psi. What is the recommended bottle pressure for the Zex kit? Zex says 900-950 psi, whereas other manufacturers say 1000-1050 psi or so.

1MTNCAT said:
My car's dyno was nearly a flat 11.9-12.1 on the 350HP and 503 Lbs ft torque spin on the rollers. It seems to hold pretty steady. "J" even commented on the system holding the ratio's very well.
With a correct and steady bottle pressure, holding all other factors in good standings (fuel pump, etc), there should be a pretty stable A/F across the board then I'm assuming.

1MTNCAT said:
Sounds to me like your car is going rich then going lean. Could be a problem in the fuel system, not enough pump or regulator not doing its job as well as anything the kit could be doing. You should have some variation at "Tip in" but it should level and pretty much hold after that. If its not then somethings probably awry.

Check things out and be safe with it. :)
Since I continuously mix up rich and lean, I'll just go by numbers. The A/F when it's first triggered is pretty high (about 14:1) but very soon after it settles in at about 12:1 and holds for a bit, then slowly goes down to about 10:1 but stays fairly steady there. I'll post my graph so you can see what I'm talking about.

I've got a 255 lph pump in the tank and an Aeromotive afpr set at 40 psi. I also have 24# injectors, but with the tune, I don't think the injectors should be the problem.

In running the nitrous last year, the car seemed to run very well. I had the bottle at about 75* before the runs and I only made about 5 passes with the bottle, so I'm assuming the bottle didn't cool too much in that time, but it was much colder when it was tuned.

A heater and pressure gauge are definately going in before it makes it to the track again, and I might even get it on the rollers to check it to make sure.

Joe
 

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Discussion Starter #5
Here's the graph with the correct fuel jet and a cold bottle. Sorry for the size



This is one with the 46 jet in. It is a little better stability wise, but still dives.



Joe
 

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Pressure on that kit should be at 1000-1050 according to the paperwork I received with mine when new and that is where I run mine.

That will have an effect on the power also. You also can't guess as to where the pressure is run to run. two things happen. As you use nitrous pressure generally drops, then on the subsequent passes the same thing happens. The lesser amount of nitrous the more the pressure drops. Its not only temps.

To accurately know what it is, you need to have a gauge and KNOW what it is every pass/run and a heater if necessary to keep it up.

Good dyno numbers. It will do better when you get everything leveled out.

Have a good one!

:)
 

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Discussion Starter #7
Thanks Steve. What heater do you run if I may ask? Would I be better off with a simple constant temp heater, or one that is pressure controlled? And where would be the best place to get one? I know Summit has Zex and NOS equipment, but I'm assuming those are just simple thermostat controlled ones. I'll do some digging and see what I can come up with.

Joe
 

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Whitecougar

There are many suppliers out there to purchase from but I bought one from www.archeat.com

The phone number is 1-877-272-4328

They have different kinds, sizes etc available. There prices are a bit more than some but I can personally vouch for the products. Check there first. Most all Nitrous retail suppliers have their own brands but most aren't that good as far as what I've dealt with in the past.

Hope this helps. Let me know what you find and how it works out for you.

Good luck to you and let me see those digits!!! :)
 

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Discussion Starter #9
Thanks for the link. Just at a quick glance, this one seems to be the most appropriate for my app.

http://www.archeat.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=Archeat&Product_Code=AN-619DWK-4&Category_Code=NBH

Looks like the only other thing I'd need with that would be a pressure gauge/manifold to run off the line.

I also came up with this one from Summit, the NX heater.

http://store.summitracing.com/default.asp?Ntt=nitrous+bottle+heater&Ntk=KeywordSearch&DDS=1&searchinresults=false&N=0&target=egnsearch.asp&x=37&y=19

It comes with a gauge and is also a little more pricey than the other one, but there's not too many details on it.

I will call both of them, unless the NX one wouldn't be worth getting, plus it's quite a bit more expensive. I'd rather have one that controls the heat based on pressure than simply keeping the bottle at a constant temp.

Do you have any recommendations for guages for the first one? I figure one from zex or something of the sort should do fine.

Thanks for all the help thus far too.

Joe
 

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That would be totally up to you. I have my gauge in the trunk at the bottle so I know what it is and check it just prior to running. You can have one mounted in the car so you could see if from the drivers seat and purge to get the pressure exaclty where you want it prior to launching.

The choice is basically yours. I manually work mine just for consistency sake. I am considering going to the other soon and see how that works out. We'll see.

Glad the link helped. Good luck!!
 

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Discussion Starter #11
Well, I went ahead and ordered the heater from archeat, and a simple Zex gauge to mount on the bottle. I'm looking forward to getting these put on and seeing how the numbers are. We shall see in late May.

Joe
 

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Good luck on the purchase and the install.

Keep me posted as to how it goes. Make sure you check the pressure often on that. The heater does a really good job of warming those bottles. It will drain your battery too so don't leave it on with the car turned off for long periods of time.

Happy modding!!
 
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