I don't have to remind anyone that there is a wet/dry controversey...

However, considering that there are knowledgable, thoughtful, experienced people on BOTH sides of the equation; that seems to imply that there is a way to do dry RIGHT and a way to do it WRONG.

(I have traditionally been a "wet" person, but I got a pretty good deal on a Zex dry kit.)


So, if you are reading this, have used a dry kit and have been SUCCESSFUL...
(Meaning your engine didn't blow up.)

The what is it that you believe you did to BE successful?


Was it just larger injectors?
Was it the tune? The amount of timing you pulled?
Your fuel pump or line pressure?
Your fuel pressure regulator?
The brand names of the parts you bought?

 

I ran the NOS 5176 dry kit for about 5 years. No problems... worked as advertised. You don't need larger injectors, but you do need to change them to a pintle style injector that can live with the higher fuel pressure. I never pulled any timing. Never altered the stock program. The kit included an excellent Bosch inline pump (NOS no longer uses that model) that provided ample fuel. You don't need an aftermarket fuel pressure regulator.... in fact it had problems working with my aftermarket AFPR and I swapped the factory FPR back in. All the nitrous parts except my inline nitrous filter (NX) came from NOS. Injectors were FMS/Denso, plugs were NGK TR6's. An MSD-6A seemed to help. Downside to the kit was the very crude method of adjusting the fuel by using a jet that bled off the nitrous stream that was used to increase fuel pressure using the vacuum port on the FPR. As a result, I tended to run the system on the rich side to limit possible damage.

Currently running a dry 300-shot (800HP total). No problems. But its not something you'll find off the shelf..... remnants of the 5176 kit, dual Bosch fuel pumps, 78# Bosch injectors, and an aftermarket ECU capable of running a program that incorporates WOT switch, window switch, programmable rev limiter/nitrous cutoff, and able to shift from NA programming to N2O programming when the nitrous system is armed.

 

Would the Digital 6 be alright or do you feel the 6A is needed?

Also wondering...
If I'm reading your post correctly (please tell me if I'm not), you feel that adequate pressure and a fuel system that can keep up is the key.

But you don't mention specific pressures.

Obviously, running half the shot you run means that I don't need the pressure you do, but is there a way to calculate the CORRECT pressure?

 

With the NOS dry kit, its designed to run at standard LT1 fuel pressure.... 43.5psi. When you actuate the system, a small slipstream of nitrous is passed through a pressure regulator, and applies that pressure to the FPR vacuum port, boosting the fuel. What pressure it boosts to is controlled to some extent by putting a small "jet" in the vacuum line from the intake manifold to the FPR, and bleeding nitrous pressure off to give a lower or higher fuel pressure. With the full 150-shot, you're looking at 85-90psi on the fuel system. You adjust the bypass jet to match the amount of N2O you are spraying.

My experience was limited to the kit's original configuration - roughly a 125-150 shot, non-adjustable. I bought the kit in late 94 or early 95, and at that time they didn't have the "adjstable" feature. That was added later. I bought the add-on kit for the adjustment, but never used it, deciding to go the stroker route with a custom system. I would assume its simply a matter of using the matched sets of nitrous and "fuel" (pressure) jets for the HP level you want, and reading the plugs to verify the mix, just like you would with a wet system. You can calculate the approximate fuel pressure required for each HP level, but its not useful info, since you can't really accurately control the fuel pressure, other than the degree of control the jet in the vacuum bypass line gives you..... to me that is a "crude" way to handle it.

I really didn't care which way I went - wet or dry, as long as it worked reliably. The shop that built my engine was completely "dry" oriented.... and they had what sounded to me like very valid reasons for that preference. Definitely at odds with mainstream thinking, but they had built so many killer dry nitrous cars - including their own 7.0-second PRO 5.0 Mustang - that I decided to go with their ideas. The setup is highly dependant on an aftermarket ECU like the MoTeC. The features that the MoTeC provides with regard to injector timing, ability to run large injectors while still providing the turndown required for smooth idle, individual trims on each cylinder for fuel and timing, ability to set up offset fields for changes in inlet air temp, coolant temp, etc.... make it "dry nitrous friendly". I run 64# Bosch injectors at 58psi (~78#/HR). Duty cycle at 800HP is only 70%. Dual Bosch fuel pumps, one in the normal in-tank position, runs all the time, and one outboard off the back of the fuel tank, runs only when the nitrous system is armed.

I don't think whether you go wet or dry is a major issue..... people have done OK with both setups. No matter what system you choose, the key is tuning, and recognizing the fact that you need to look at each individual cylinder, to identify any distribution problems with the system you selected. The more uniform the distribution of both fuel and nitrous, the more power you can make with less risk of a single cylinder running lean... because that's all it takes. Once you have maldistribution, you have to tune to protect the leanest cylinder (and/or one that runs hotter simply because of cooling system configuration) and that means you will be running too rich on the other cylinders and giving up HP. Of course a direct port system gives you the ability to gain additional control over individual cylinders, but that's a step up in complexity and cost.

Just a bunch of rambling thoughts........

 

Thanks. That was helpful.

 

I've slipped the stock longblock a 180 shot of nitrous on a dry kit, and will spray more next season. Iv'e always used dry. I think dry eliminates the distribution problems associated with trying to evenly dispense a liquid enrichment fuel. Take a look at some of the fastest street car shootout guys spraying a wet plate and look at the design of current high hp plate systems. They are geared toward even distribution. There are definately distribution concerns with wet systems; that's why fogger systems (individual runner) are used. Yes, I've made my point by streching to higher hp applications, but I believe the distribution problems are present at or below the 150 hp level, especially on the LT1 wet plate designs.

I started spraying with a 30-40 hp dry kit and have worked my way up. I've always loged data. I started seeing problems with what I believe to be the stock pump/injectors at the 150 hp level so I switched the enrichment fuel to propane. Size your equipment properly, follow your kit manufacturers specific instructions.

A word about tuning - the engine is a system only as good as the weakest cylinder. The important thing is to start slow, check your plugs, and think about what's going on. I log data with freescan, hundreds of hours across three cars. I've directed a lot of attention to the issue of false knock. I've gone so far as to advance the timing to the point of audible detonation just to veryfy the stock knock sensor operation. I don't think there is as much false knock as people want to believe. You have to remember there are 8 individual cylinders in the system; if you look at the plugs closely you will see definate operating differences between the cylinders. One of the keys to a long lasting engine is to tune to the weakest cylinder, pull timing and/or add fuel. This probably will not return the highest power output - fastest MPH at the dragstrip. But it will relieve the stress on that piston, rod, bearing, and crank throw. My advice is that the 2 degrees per 50 is the minimum acceptable on an LT1. The LT1's high compression ratio mandates ignition retard. The stock knock sensor/timing retard program will accomplish this for you assuming you have not modified it, as a lot of tuners like to turn it off (yes you will likely run faster with it off). I would also follow the NOS recomendations for gasoline octane requirements. I am confident you can not spray 150 hp on pump gas for any length of time and not damage the stock shortblock. I'm talking seasons or years here.

In short pull timing and use good gasoline. Start small working your way up checking all eight plugs as you go.

Just my 2 cents - 125,00 miles 11ohs and still driving it to work every day.

 

I do have an aftermarket tune with a more aggressive timing curve.

I'm getting a new tune for the bigger injectors, so this would be a good time to change the curve.

BUT...
I'm planning to run a Digital-6 for ignition control, including retard; so do I NEED to worry about the "off-gas" tune?

BTW, I mix my own gas, a 4:1 mix of Sunoco94 & Toluene, which gets me 98 Octane. I can also mix any octane up to 114, although that gets pricey, obviously.

 

I'd go ahead and leave the ignition curve maximized for motor. Then use the ignition box to retard on gas. The biggest problem I've seen is guys forget to change the pill or the setting. In any case think about letting the tuner leave the knock sensor program in tact. If you wish you can reduce the knock sensor sensitivity with resistors. That way you will not have to keep changing programs or tunes. Again, you need to be careful with this; you can and will destroy the bottom end with real knock. I ran the 11.0 with the stock knock program, it can be done.

You need as much octane as it takes to prevent engine damage. How you get there is up to you. I know your chemical mixing is controversial. Check the plugs for any sort of spotting.

What are you paying for a gallon of toluene? And, where do you get it?

 

I have switched over to an LT4 knock module, which is allegedly more discerning. I'm honestly not sure if Brian took out the knock retard or not.

I'm not going to play around with the nitrous too much. Probably just spray about 125hp and do it with a progressive controller. I just want to try the new technology and see how it works before I do my rebuild; so that I can judge whether or not I want to use nitrous on THAT motor.
(X-Trim on top of 10.5:1 compression 3.50"/6.00" 359ci LTx, running E85 fuel.)



About you other question....
I honestly can't remember what I pay for Toluene, because the summer months are long gone. I think that I once calculated that it got me 98 Octane for about three and a half dollars a gallon, using 4:1 Sunoco 94.

Where I GET it is easy... Sherwin Williams.

Make sure you ask for the contractor pricing so that you pay what the painters pay. They'll give it to you, but only if you ask.

If they ask what you want it for, tell them it's for your race car, even if you drive the car on the street.

 

You'll have fun.

The real fun will be tuning high compression, boost, spray, alcohol, and gas.