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Where do I put my GM temp sensor in relation to the nitrous nozzle?

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perrytheplatypus157

Proven Member
81
44
Jun 18, 2017
Fall River, Wisconsin
I've done a lot of reading and it seems as though the best place to put the nitrous nozzle is 6 inches from the throttle body. It's a 50hp wet kit (30 nos nitrous jet and 16 nos fuel jet). I'm redoing my intercooler piping, but I was wondering where I should put the GM iat bung in relation to the nozzle. If before, I won't get the temperature change, but after, and I don't know what kind of damage the sensor would see from the spray. Anyone else running something similar or have any ideas? Thanks
 
NO2 is VERY cold. Put the sensor between the IC and the TB, pre NO2 nozzle, so between the BOV and the NO2 nozzle. My nozzle is in the TB elbow. My intake temp sensor is after the BOV.
 
I'm commenting because I'm interested in following along with this thread. Unfortunately, I can't be of much help because I don't have any results at this point, however I have located my dry shot nozzle before the AIT in order to allow for fuel enrichment even if the intake charge temp slams far below what the AIT sensor is capable of understanding. Again, because it's a dry shot, this theory made a bit of sense, but I can't really help you given that your fuel will also be jetted. I'd think that you are better off spraying a wet shot post AIT, but a dry pre ait due to how the fuel enrichment is going to be handled. I'm sitting on pills for 25-40 "HP" so I can bump the nitrous and get up on the converter a little quicker so tuning will hopefully not be too difficult.
 
I like the idea. Good reasoning.
Appreciate the quick response. Ok, so air would flow in this order: IC, BOV, GM sensor, nozzle, TB. Correct? Also, for what reason should the sensor be after the BOV?

It can be before the BOV, it is just where I put mine and it worked out perfect. Closer to the IC outlet, the cooler it will be so that's an option.
 
On my car I put it before the N2o. You are running a wet kit as am I. So the kit should introduce the additional fuel not the ecu. My theory was jet it and forget it. Otherwise your ecu would try to compensate for the temp swing.
 
When you spray, do you spray into boost? If so, then you wouldn't be able to set a jet and forget it, right? Reason being is that your fuel pressure rises at a 1:1 ratio when under boost but the nitrous pressure is constant. Wouldn't that affect the mixture?
 
I tune my nitrous fuel jet to achieve the desired air fuel ratio when spraying. The nitrous is very consistent unless the bottle pressure drops. A secondary map with different timeing values is helpful as that is the only thing I change for the nitrous.
 
I tune my nitrous fuel jet to achieve the desired air fuel ratio when spraying. The nitrous is very consistent unless the bottle pressure drops. A secondary map with different timeing values is helpful as that is the only thing I change for the nitrous.
When do you spray? The nitrous may be consistent, but the fuel wouldn't be. Correct? If you have 900 psi of nitrous with a XX jet, it gives you X amount of nitrous. If you have 42 psi of fuel with YY jet, it gives you Y amount of fuel. Then your nitrous (X) with your fuel (Y) would give you an AFR, but if your fuel pressure increases as it does with boost, you would no longer have X+Y=AFR. You would have the same amount of nitrous as before, but more fuel because of the pressure increase. Does that not change the AFR? I'm sort of confused
 
Im already at full boost whenever im spraying. Fuel pressure is boost reference. Boost is a controlled factor. If im running 35 psi of boost adding 100 shot doesn't change my wastegate settings. An auto leaving on much higher boost due to spraying off the line would require a complete dyno session on the nitrous to dial the tune correctly. But as far as affecting iat with n2o I don't find a paticular reason to bring that into the equation as. Nitrous oxide boils at -129°F and it begins to do that as soon as it’s injected into the intake manifold. I haven't tried it but I don't believe that the gm iat in my car has enough range to pickup on that kind of temperature differential. Would it cause issues, ice up the iat sensor and temporarily skew my iat readings after a hard pull. I don't know but I would think its possible. And when im racing in Mexico I want to be back on the gas to flee the federales before the ice melts.
 
Nitrous is around 900psi, so the 20-30 psi change in the charge piping doesn't effect nitrous flow as much as it does the 43.5psi fuel system. This is because the pressure change is a much lower percent of the base pressure.
 
If you cannot use dual maps for tuning nitrous, or are already using dual maps, for say meth etc..
Spraying before the IAT can be useful, as you can use the intake temp/timing map and drop off a bunch of timing when the IAT sees crazy low temps from the nitrous.
Another way to do it, is when the nitrous is triggered have the IAT circuit switch, to a circuit with a resistor, to trick the computer in reading a super low IAT that will drop off some timing. This way, the location of the IAT doesn't matter.
 
Alright, I figured out where to put my nozzle in relation to the iat. Thank you. I guess I may just have to start a new thread because I see I'm kind of asking two questions here.
Nitrous is around 900psi, so the 20-30 psi change in the charge piping doesn't effect nitrous flow as much as it does the 43.5psi fuel system. This is because the pressure change is a much lower percent of the base pressure.
It's not the flow of nitrous I'm concerned about, it's the change in AFR created from the varying fuel pressure versus the constant pressure of the nitrous. This would create a richer mixture as the fuel pressure changes (because of boost rising) if you've jetted your kit for base pressure.

Maybe I'll just have to see what happens come spring when I can actually get the car out or heck, maybe the nitrous shortage is going to leave me without it.
 
The fuel keeps a 1:1 ratio of fuel pressure to boost, that way flow remains constant. The nitrous pressure is so high that boost pressure doesn't really affect the flow out of the nitrous jet.


This is how it would look without a rising rate 1:1 fuel pressure regulator at 20psi of boost with a nitrous shot.

The nitrous flow goes down in proportion to 20/900, the fuel flow would change in relation to 20/43.5.

As you see to keep fuel flow the same across different psi of boost, the fuel pressure has to change at the same psi as boost. But, with nitrous having such a high pressure, a 1:1 regulator isn't needed to keep the flow in check.
 
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