nitrous
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Want to tune it and get it right, use an AF meter. Get the tune up spot on for NA, then jet the juice unit for the same AFR as NA.
NX uses a lot of fuel pressure. If that works out and gets the tune right great. Most of the kit tunes out of the box are fat. At least the fuel jet is smaller than the N2O jet.
NX uses a lot of fuel pressure. If that works out and gets the tune right great. Most of the kit tunes out of the box are fat. At least the fuel jet is smaller than the N2O jet.
TT5.9mag
Two atmospheres are better than one
I was just going to say something similar to what @crackedback said above. The fuel pressure is a tuning point. You can increase/decrease the pressure to dial in the fuel side.
Bobzilla
Well-Known Member
I have only run NOS brand kits so far. I see you are looking at instructions for Nitrous Express (NX) kits. I just looked at their website and the instructions for two different kits I checked out had the same 8-10 psi spec. Just beware that if their kits are calibrated for that much fuel pressure with the suggested jetting but you start off running lower fuel pressure you will be leaning out the settings.
If it were me, I would call them or send a message and ask if the instructions are correct, or I would start with their suggestions and then if it runs rich while activated you can start lowering the pressure.
Bobzilla
Well-Known Member
If you already "needed" an NGK 8 range spark plug with your combination naturally aspirated, put a set of NGK colder 9 range plugs in as @Jeremiah (jd) suggested. When starting with less compression and less engine horsepower your tuning window margin of error is much wider. With engine power and compression, the tuning window gets smaller. Don't assume you are good until you make sure. Once it is sorted out and you know what it wants, it will live a long happy life unless something malfunctions, like low fuel pressure or fuel with too low octane, or even ambient temperature getting really hot like it is right now in your area.
Edited to fix plug heat range as pointed out in post 33.
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weedburner
Well-Known Member
If he "needed" NGK 8's NA, I would go the other way with 9's for a slightly colder plug with nitrous.
Grant
We used to purge through the engine. LOL
Bobzilla
Well-Known Member
Absolutely agree because of NGK numbering. I messed up that one.
TT5.9mag
Two atmospheres are better than one
I’ve never had a system with a purge. We always just burped it through the engine.
weedburner
Well-Known Member
Keep an eye on the plugs instead of relying on AFR alone, most engines have a cylinder or two that are a little closer to the danger zone than the rest. The cylinders I pay the most attention to in my sbc are #5 and #6.
Back around 2013, I had an obsession with spraying 200+hp doses of nitrous on on 87 octane pump gas, using cheap $90/set rebuilder hyper pistons. Super low compression, only cranked about 100psi on the starter. You don't often get to examine cracked hypers before they explode, but I had devised an early warning system. Basically I seal the crankcase, use a PCV valve to draw a vacuum in the crankcase, then monitor crankcase vacuum with a gauge in the cockpit. If there is any change in the ring seal, the hurt shows up on the vac gauge as soon as the engine returns to idle. The loss of power isn't noticeable, but I do a leakdown whenever crankcase vac drops from normal at idle.
The pcv valve in this hyper engine normally pulled about 9-10"Hg of crankcase vacuum at idle. In this instance I was out making 1/4mi passes on a backroad, spraying around 200hp on 87 octane. AFR's with nitrous flowing were between 12.1 and 12.6 pulling 10 degrees of retard. First couple passes were great, I decided to put an 8* pill in. Sweep data said it picked up on the 3rd pass, but I noticed idle vacuum had dropped to 5"Hg from the previous 10. Suspecting the engine was hurt, I drove it home to find the problem. Plugs looked good, but two pistons had cracks...
After replacing all the pistons using the same rings, it was back to normal the same day.
The engine had picked up on that 3rd pass, without that early warning system I would have leaned it a little for another pass and likely lost everything inside. I had several sets of hypers out of that same engine, they also got swapped out after finding cracks.
Still use the same early warning system today, but i'm wiser now and rarely hurt an engine.
Grant
Back around 2013, I had an obsession with spraying 200+hp doses of nitrous on on 87 octane pump gas, using cheap $90/set rebuilder hyper pistons. Super low compression, only cranked about 100psi on the starter. You don't often get to examine cracked hypers before they explode, but I had devised an early warning system. Basically I seal the crankcase, use a PCV valve to draw a vacuum in the crankcase, then monitor crankcase vacuum with a gauge in the cockpit. If there is any change in the ring seal, the hurt shows up on the vac gauge as soon as the engine returns to idle. The loss of power isn't noticeable, but I do a leakdown whenever crankcase vac drops from normal at idle.
The pcv valve in this hyper engine normally pulled about 9-10"Hg of crankcase vacuum at idle. In this instance I was out making 1/4mi passes on a backroad, spraying around 200hp on 87 octane. AFR's with nitrous flowing were between 12.1 and 12.6 pulling 10 degrees of retard. First couple passes were great, I decided to put an 8* pill in. Sweep data said it picked up on the 3rd pass, but I noticed idle vacuum had dropped to 5"Hg from the previous 10. Suspecting the engine was hurt, I drove it home to find the problem. Plugs looked good, but two pistons had cracks...
After replacing all the pistons using the same rings, it was back to normal the same day.
The engine had picked up on that 3rd pass, without that early warning system I would have leaned it a little for another pass and likely lost everything inside. I had several sets of hypers out of that same engine, they also got swapped out after finding cracks.
Still use the same early warning system today, but i'm wiser now and rarely hurt an engine.
Grant
Jeremiah (jd)
Well-Known Member
The bottle valve is facing the passenger side. I top off the bottle or swap for a full bottle after 1 or 2 runs depending on the jets amd 1/8th vs 1/4. AFR = 13.0-13.2 with no issues. I run a purge, but you can purge into the engine if a purge cannot be obtained. My kit and much of my tuning theory came from the late great Monte Smith.
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