I have actually been doing a lot of testing regarding this, because I was under the same impression: that the car will run just as well with less bottle pressure.

Anyhoo, I have been doing some testing over the past week and here is what I have found related to bottle pressure. All testing was done with a 75 dry shot (noooo traction) from a NOS 5177 kit ontop of an ARE H/C car. Purge was used in every case.

Bottle Pressure 1100 PSI:
1) Car kicks like a mule
2) Fueling is good.
3) No KR (timing at 25 w/ edit)
4) O2 hold steady at NA levels
5) Injector Duty Cycle Increases dramatically with N20 injection

Bottle Pressure 900 PSI:
1) Car kicks like a mule
2) Fueling is good.
3) Mild KR up to 2 deg.
4) O2 hold steady at NA levels
5) Injector Duty Cycle increases mildy with N20 injection

Bottle Pressure 600 PSI (cold):
1) Car stumbles
2) Fueling does not change with N20 injection
3) Massive KR around 4 deg
4) O2's deviate down roughly .2 to .3 from NA levels
5) Injector duty cycle does not change with N2O injection.

It seeems like the lower my bottle pressure the less the MAF picks up the N2O going into the motor. At the lower bottle pressures, the car barely even recognizes the N20 going in. You can still feel a change when the pressing the "go" button, but the car stubmles, and begins to surge close to 6000 rpm. Basically, the car does not like the lower bottle pressure.
The higher bottle pressures everything goes as planned. The MAF picks up the NOS and all goes well.

My thinking: I think that at the lower bottle pressure the N20 does not mix with the air properly, and I am ending up N20 traveling along the underside of the intake outside the normal laminar flow (because it is much denser). Because of this the MAF barely picks up any change air mass, and does not adjust the fuel accordingly.

Has anybody else found this? Am I the only one with these results?

<small>[ October 18, 2002, 01:12 PM: Message edited by: NoGo ]</small>

 

Wow...thanks for the info. I believe you are correct. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Cool! Actually a thread that I post that other people comment on! keep em comin! NoGo's info is very interesting. I wonder what the same effects would be with a wet kit? I think there would be less knock but alot less performance because of the rich mixture...

<img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

With a wet or dry kit if the bottle pressure is not of at least 900 psi it will not dispurse properly.The Nitrous will not flow in a steady flow.Even the dry kit is desighned to operate with atleast 900 psi.The best pressure to run is 1100 psi.A bottle heater will help you get more runs out of your bottle.
Dave

 

I was just thinking and I thought Id post this...

Nitrous kits release nitrous based on bottle pressure, and a wet kit has fuel jets for a CERTAIN bottle pressure. Even though most of the time the bottle pressure is where it needs to be, if it is low you will run rich, lean if the pressure is too high.

Therefore, with a dry kit, no matter what the bottle pressure is, the MAF will send Just the Right Amount of Fuel.

Thanks for listening...
Wes <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />

 

Yes about MAF if and only if the fuel can deliver the amount of fuel calculated. If it can not..... <img border="0" alt="[kaboom]" title="" src="graemlins/gr_bomb.gif" />

Because of that, I would only run about a 75hp shot on a stock fuel system.

 

You wouldnt run a dry kit over 75? Ive heard people saying even 125 is safe for a dry kit, esp on a 98 with big injectors

 

I run 150 shot wet on my 97 LT1 with stock fuel system. It works fine. I even used the NGK tr's meant for no nitro. I have felt a power loss over time sprayin with those plugs. Im sure i need the NGK step colder plugs. One thing is agreeable about the original post with the wet shot, hes right. But at the same time on dry shot the injectors can lock up on stock with too big of shot. There are pro's and cons to both systems. Pick your poision and take prevenitive action over saftey get all the extras (guages, fuel saftey shutoff window switch bigger injectors ect. you get the idea. (Im on here with LT1 becaus i dont like the forum for LT1. I love both motors Have both. Long live both of them! <img border="0" alt="[guns]" title="" src="graemlins/gr_guns.gif" />

 

I'm using a 125 shot on my 5177 kit in my '01. No problems to report other than my car also doesn't seem to gain much if anything at extremely low bottle pressures ... 600 psi or so. It surges and just doesn't act happy. At roughly 900 and above it hits hard and runs flawlessly . I wonder what the actually reason for this is ?

 

On my car with dual .040 jets, the A/F spiked at 14.2 for about 600 rpms on the initial hit then dropped right off every time. I never shoot with less than 1000 PSI. Try to keep it round 1200 for MAX effort

 

I have a LOT of experince with MAF referenced dry systems on the ls1.
I was running it dry back in 98 before NOS even came out with a dry kit.

The method works OK. It's a real tricky thing to tune properly beyond 125hp or a set of .038's.
You really need a wideband but stock o2's and plug reading will workout OK.

I tried dual nozzles, single nozzle, wet and dry and then moved to a custom 14 hole dry spraybar I made.

I used 42lb injectors at 60psi and dual .055's for a while.
Then a spraybar and a .078 jet.I could not ever get it to run real well an entire pass.
It would be very strong out of the hole. The hit was as good as any system I have ever run for the jetting.
But it always ended up going dead rich up top and sputtered around the 1000ft mark as the maf began to over compensate and added to much fuel.It was actually easier to tune with smaller injectors.
Just dial in enough spray to max the injectors at a good looking plug tune and hold on.
But this was long ago when I was trying this with stock PCM tuning and sensor manipulation for larger injectors.

Low bottle pressure will work OK.
I ran 11.22 at 114 shutting down at the 1000ft mark on only 650psi. 2.73 gears.

At the higher power levels it gets harder and harder to manage as the maf is easily over cooled and goes real rich.
So if you had it all setup nicely with lets say 800psi and then ran 1100psi, odd's are it will go to rich if you have the injector.Or if your on the limit of injector you'll go lean.

Back then when I was playing with dry methods I liked it.
But in hindsight, wet systems are so much easier to dial in.
And the intake does flow wet pretty well.
I run huge amounts of water/methanol through it now with the blower.

Although with ls1edit, you could tune a high power dry system much better now.

Steve

<small>[ November 01, 2002, 12:20 PM: Message edited by: SJH ]</small>