I see that you can buy either a wet shot or a dry shot for nitrous systems, whats the difference?

 

wet has gas with nitrous, dry has just nitrous, but if your going with anything over 75shot dont get a dry set.

 

Properly set up, both a wet and a dry sytsem require extra fuel to match the amount of nitrous that you are spraying.

In a wet system, the nitrous and fuel are both sprayed together, at the intlet to the intake manifold, or via "direct port" nozzles installed in the intake manifold runners.

In a dry system, only the nitrous is added to the incoming air stream, and the extrra fuel is added through the stock injectors. This is accomplished either by raising the fuel pressure when you spray (NOS 5176 dry kit) or by using an aftermarket computer to increase the injector pulse widths.

I sprayed 125HP dry with the NOS 5176 kit for 5 years, no problems. Currently running a 300-shot DRY on top of a 500HP stroker. Fuel is supplied through 64#/HR Bosch injectors running at 58psi (equals 78#/HR), and controlled with a MoTeC engine management system. Works fine. Absolutely nothing wrong with a dry system AS LONG AS IT IS SET UP PROPERLY. The shop that does my work runs ONLY dry systems, including their own 7.0 second Pro 5.0 Mustang.

 

exactly! thank you. god, if i hear one more bad thing about dry kits from people that dont know what they are talking about or doing (blown motors, blah blah blah) im gonna shoot someone. i mean, my god, wet manifold cant be that great or blower and turbo setups would be using a fogger nozzle instead of larger injectors. thanks for setting the record straight Injuneer.

 

Back the point i was really trying to make. Most people who ask about nitrous and want to do a dry shot would never think of adding more fuel pressure or bigger injectors, mainly because they dont know how or what and when they find out how much it is to do it correctly, wouldnt. That is why on stock injectors and stock fuel pressure its not really safe(daily driving safe) to run more then a 75shot. But as you both stated when used correctly it dont matta.

 

thats the reason the NOS kits raise fp when the nitrous flows thru the soleniods. all you have to do is follow the directions when setting up the kit.

 

How does the ECM add fuel for you when you use nitrous? Is there an input that tells the ECM when you open the solenoid? I always assumed that it is like a "switch" and when you open the N2O solenoid the ECM gets a signal to jump to a different fuel table. Is that right? That way you could still run on the "normal" fuel table when N2O isn't used. You don't use a MAF sensor do you?

I would love to run a dry setup with the fuel controlled by the ECM someday. Right now, I think my college student budget is going to force me to tune my fuel with a stand alone system that I can change pressure and jets in. An aftermarket computer is way more than I can afford.

Sorry I have so many questions, but I have always wondered how this works.

Dustin

 

with all the systems that have wideband capability now running a dry nitrous kit is a lot easier. it used to take a lot of dyno/wideband time to setup the maps. you started out way rich and worked your way down.

 

What tells the ECM to use the "N2O" map?

 

you wire the nitorus WOT switch into the computer or use a throttle position sensor.

 

umm...........


In most dry kits for lt1's to increase fuel to the cylinders, a extra INLINE fuel pump is used to increase PRESSURE so that more fuel flows when the nitrous is activiated. The PCM doesn't know to change anything.


And if your on a budget and want to use a dry kit with PCM fuel maps, just get a wet kit, just change jet sizes alot easier The computer is out of the loop, you control the A/F ratio yourself....

 

as far as the computer stuff, we were talking about gen 7, fast, speed pro and motec systems where you can control the nitrous fuel flow thru the computer, not the stock computer.

 

We got off track and I was asking about "non-traditional" dry kits where fuel is controlled by the computer. I know this doesn't apply to 99.9% of the dry kits out there.

Dustin

 

The MoTeC basically has two programs.... an NA setup that is the default. As soon as I flip the "arm" switch, the power is enabled to the solenoids, the extra fuel pump kicks on, and the "armed" signal goes to the MoTeC as a digital input. From that point on, the computer continues to control on the NA program, until the programming in the computer tells the nitrous to activate. In effect, I can program RPM and throttle position limits in the MoTeC. Once I meet the programmed conditions with regard to TPS and RPM, the MoTeC kicks the nitrous solenoids, and simultaneously adds the "nitrous" program on top of the NA program.... in essence the nitrous program adds fuel to the NA fuel maps, and pulls timing from the NA spark advance map.

The MoTeC also offers the advantage of being able to individually program fuel, spark and injector timing to EACH individual cylinder. Part of the dyno tuning was evaluating the nitrous distribution, using the two NOS fan-jet nozzles in the outlet of a stock Ram Air box. We found by examining the plugs that there was virtually no maldistribution of either air or nitrous. If there had been, it would have been possible to adjust the fuel to each individual cylinder, or even pull some extra timing on individual cylinders, but that was not necessary. Tests with "plate" type distributors for dry nitrous showed major problems with maldistribution of nitrous between the cylinders..... we could have "tuned" down the fuel to the individual cylinders that were not getting their share of nitrous, but that would have meant some of the cylinders were simply producing less HP that the ones that were being pushed to the max limits.... and why give up that HP?

Second Street uses the NOS NOSzles in their Pro 5.0 car. But they use them ONLY for nitrous, using a MoTeC to control the fuel.

Just to clarify on the NOS 5176 kit, the inline booster pump provides the flow/pressure curve that allows the system to flow the required volume of fuel at the required 85-90psi, but it is not the pump itself that raises the pressure... it is the pressure applied to the vacuum compensation port on the fuel pressure regulator that raises the pressure. If you don't apply the pressure to the FPR, the system runs at the stock FPR setting, even when both pumps are operating. It just bypasses more fuel to keep the pressure where it belongs. I don't think anyone was saying that the PCM changed the fuel pressure..... I'm sure everyone here knows it can't. Niether can my MoTeC.