MAKING THE DRY SHOT EASIER TO WORK WITH

The biggest complaint about the dry shot is tuning it. The biggest complaint about a wet shot are the variables of bottle pressure, fuel solenoid reliability and what happens during a failure. If a fuel solenoid fails which I have seen quite a few times, you get a lean condition. If it leaks you get a backfire. If the nitrous solenoid doesnt fire its a rich stumble you get.

My system didnt install the way other dry systems do. The tuning for a dry shot is to use one dry nozzle pointing toward the MAF to get a concentrated shot of air on the MAF making it think the incomming air is filling the entire volume of the MAF unit and the PCM commands more fuel to be dumped. You also had a hard time adjusting it a little richer or a little leaner. Aiming nozzles can max out the MAF sensor too at one point. The MAF can be made to not max out if the fueling is not done solely with aiming the shot to concentrate the hit at the element. You can have the IFR vs IAT table dump some with nozzles further from the MAF which yeilds less MAF frequency range used for a given shot size. When I hit my thumb activation swith, the IAT reads a higher temp and I programmed the IAT vs Inj flow rate table to dump the extra 8% fuel I want. The MAF never maxes out and the sytem can be brought higher up without puddling, fuel solenoid woes, or bottle pressure varyance.

You can set up the HPT scanner to log MAF frequency to see where you are at but there is a simple and much more accurate way to tune a dry shot. Another tuning problem is timing; it is adjusted with a timing tricker box and you never know if its working because they intercept the signal from the crank and the scan always shows the commanded timing even if the timing is being pulled.

Harris speed works has an active circiut to adjust fuel and timing curves to suit the fuel and spark retard of any application and it goes inline with the MAF. Its advantage is that it can be adjusted to any amount of fuel or timing. It is an active circuit and it can fail. Its tuning is another matter. It also maxes out the MAF frequency at some point since it operates by inputting a false MAF frequency to the intercepted singnal in the harness it attaches to. This unit is a great way to tune dry shots....its 150 bucks.

My final methodology for tuning was to make a passive circiut with parts from radio shack and have the dry nozzles far from the MAF on my dry shot. The MAF then gets a more even hit instead of a concentrated hit and its actually near the commanded PE a/f ratio. To get it richer I used an IAT tricker circiut. The N2O would mix evenly prior to getting to the MAF and the even flow of air keeps the PE exactly at the commanded PE which is 13:1. The reason for this is that the shot will have the added fuel from a more predictable metered way without relying on the nozzles pointing at the MAF element try and guess method. I will be able to add as much fuel as I want to get the a/f to 11.8:1 where I want it. To maximize the car's N/A operation, I wanted the circiut to pull timing and dump additional fuel only while my thumb is pushing the trigger button on my T-handle and not always while the system is armed. Off the button my car runs the hottest max effort tune I could do to my car. OK, for those keeping score my car is now going to run at 13:1 on a nitrous shot as commanded (no we arent leaving it there). It is even and it is predictable. No nozzles to come loose and change where they shoot and no pointing the nozzles with a try and guess and hope reiteration to get 11.8:1 which is my target.

Nozzle location: sorry the install isnt stealth which I just dont understand. It not a curse to have a bottle. Its a legit power adder with drag race classes. NOTE: My nozzle location has changed since this pic. They are closer to the air filter away from the MAF and I use the IAT tricker for 1/2 the fueling and 1/2 from the nitrous hitting the element. Another safety issue in case something went wrong. Lots of back-up is a good thing. There is no fuel solenoid to fail.


I intercepted the signal at the MAF and installed a relay to to change resistence to the MAF's IAT sensor. (this same relay provides the ground for the relay to the nitrous solenoid so if this circiut fails due to the relay, the N2O wont fire). For those not familiar the IAT is a themal resistor and varies its resistance with the temps it is subjected to. The IAT or intake air temp sensor does exactly what it says; it measures the temperature of the incomming stream of air. In the case of my firing the nitrous the resistance is changed to make the car think that the incomming air charge is 199 degrees. Now unless you live and drive on the surface of Venus, the IAT's will never hit 199. The amount of timing is one degree more in the summer. I pull 1.5 degrees per 50HP. Now for the cool part of the tuning.

The IAT not only controls the timing curve from the IAT base spark table but on the fuel tab there is an IAT vs. Injector flow rate table (this is on the general fuel tab for C6's and the PE tab for C5's...in the C5's case its an adder for the commanded PE). In this table IFR is changed according to IAT temps. In the following screen shots of my HPtuners editor, the IAT base spark and IAT vs injector flow rate are pictured. In this first you can se where I typed in -4 degrees in the high end of the table. When I first did this mod I used the lower end of the table so the IAT could be in series with the new resistor and they both contribute to the amount of timing pulled. For example if it is 95 degrees out the car is going to pull one more degree than lower temps. On actual hotter days the IAT would vary the resistence and pull the extra degree by accessing the next hotter verticle line on the IAT spark table but my ever knowledgeable brother, whom I believe at times is supernatural, spoke some words of wisdom. A teacher by discipline, he led me to my faulty thinking by asking questions and facilitating the absorbtion of knowledge. He asked why I wanted different values for the IAT temps. I responded with the, "Duh, cause on hotter days it needs to pull more timing." "Why would you do that?" he asked. I said, "because of the hot air comming in." He then said,"Well, nitrous is so cold when its shot that it cools the air intake temps by 70 degrees doesnt it? It dawned on me that the hot air charge would always be under the 95 degree line and therefore not need anymore timing pulled so it isnt an issue. Frady cats can pull another degree if they want in the summer but it really isnt needed.




In this next table the IAT vs injector flow rate adjusts the fuel to where I want it. Smaller values richen the shot. The IFR is lowered making the PCM think it has smaller injectors so it makes them dump more fuel:



In my case the 199 degree input instructs my car to dump 8% more fuel than normal. If I want 1% less I type that change in If I want 2% more I type that in. The best part is that it all shows up in the scans. Wet shots need to have constant bottle pressure to maintan a a/f ratio (which it never is) and the only way to richen it up is to change the fuel jet. I just type in what I want and it works flawlessly.

Initially, I scanned the car safely in my driveway (later in use with a 22 shot then 50 then 75 then 100...)and bypassed my WOT switch to allow the IAT circiut to adjust the timing -4 degrees and add 8% fuel while sitting safely in my driveway and simply revving to 3500 where my shot pops in(this was without the bottle open just to see if the fuel gets dumped and timing gets pulled. The scan showed 42 degrees at that load and rpm and without moving up or down on the gas pedal and triggering the circiut, the timing fell to 38 and the long term fuel trends jumped down 8%. I wish I had saved the scans to show some screen shots but the system workd flawlessly and ends the debate in my mind of wet vs. dry.

Now some safety issues. The relay in the IAT tricker needs to be operating to supply the ground for the relay that triggers the solenoid so if the tricker doesnt function, the N2O doesnt fire. The nozzles are away from the MAF for two reasons.
1) The air and nitrous mixes fully to get an even reading and not a concentrated hit in the center of the MAF. This gives predictable fueling. Keep in mind that the MAF isnt used for adding the fuel on this dry system. It finds a baseline for the incoming air and the additional fuel would be added even if there was no MAF. This is the same operation as the harris sped works box. It doesnt need an MAF and it doesnt need the nozzles pointing at the MAF
2) The lack of a concentrated hit keeps the MAF frequency from maxing out and lets you run a bigger shot than you normally would be able to if you used the MAF to add fuel by concentrating the shot on the element.

I dont have to worry about a dry hit heading over the MAF and leaning out or an MAF failure. I have consistency and a degree of control no wet system has. If I want say 1.23% more fuel, I enter the exact value to the decimal (98.77) in the IAT vs. Inject5or flow rate table. No messing where nozzles point. If the MAF fails, no problem. In the case of my speed density tuned 2005 I dont need the MAF to even be there and the MAP/VE would calculate the fueling and still compensate to the commanded PE. I have a permanantly mounted XD-16 Lc-1 wideband to monitor fuel. The fuel curve never spikes lean on the shot engagment. The N2O takes time to hit the MAF and then the motor and the IAT commands the IFR to dump more fuel instantly. When you come off the pedal the car isnt under load anymore and doesnt need a sustained rich state. I couldnt get the car to spike lean before or after the shot even staying on the pedal. I didnt invent the IAT resistor trick first but I invented it to myself and later checking on the internet found that I wasnt the only guy to do it.

Now with all this safety and simplicity I want to see a guy make an argument for a wet shot over this. You can keep the fuel solenoid and the fuel in the intake manifold idea. If you are going to do this you need to get the MAF patch to extend the frequency limits for the MAF or you can potentially max out the MAF. For those that dont know what it is, on the editor click the operating system button in the upper left corner. A write-entire must be done to enact these changes. If anyone has questions about this system or is close by and needs a hand with its install, shoot me a PM. All my work is shareware and I share secrets. (I guess that means they arent secrets)

What shot you run is entirely up to your rear tires and the power level you have N/A. A guy running near 500rwhp on the street isnt going to run a 175 shot. Another issue is that a 50 shot is 85+rwtq. Most H/C cars wont be able to use it on street tires. A 50 shot isnt insignificant unless you have no power N/A in which you lean your car (and ego) off the bottle. 50 shot guys will have plenty of shots per 10lb bottle so its a good situation. Keep in mind that the fuel injectors need to be big enough to supply the needed fuel for the additional requirement. If you have 90% duty cycle with a H/C car and you add a 125 shot you are over the line. Think 40lb'ers for a 500rwhp car which is likely more than 550rwtq. Go bigger for silly numbers. Also remember that the fuel pump isnt going to support 600/700 without a boost-a-pump. 600HP from a supercharger isnt like the 600rwhp from the bottle. The TQ is 500 for a 600rwhp S/C car and close to 700rwtq for a 475 rwhp H/C car on a 125shot. They call it TQ in a bottle.

 

Nice writeup Spin! Thanks for taking time to post all that!!

 

Hey marc I cant wait to take you for a ride LOL!
Mike

 

http://www.nitrousdirect.com/nitrous...roduct_id=1718
This was a little cheaper. after a long talk with Spin This is the one I got canceled the first one. This one is a dry shot! with 15 lb bottle.
Mike

 

I've never been more confused about a mod in my life. The nitrous (wet/dry) debate is too much to digest. I don't know much about nitrous, except that it is "the best bang-for-your-buck" mod.

Of course Spin knows his stuff and makes a great argument for dry kits. Then you'll speak with someone at the tuning shops and they recommend wet kits. I know the wet is easier to tune and this may be the reason why the shops prefer wet.

I found it most confusing when I spoke with a couple Nitrous stores (who are strictly selling the nitrous) and they recommend the wet shots. One guy I remember clearly saying "even if you don't buy from me, definitely make sure you buy a wet kit." I still have a headache from many hours of reading about wet vs. dry.

 

Getting my 100 installed on the LS3 this weekend. Going with a programmer to hit gradually instead of a instant 100 shot that is harder on components. Let you know how the dyno goes.

 

Wet or dry?

 

the programmer is hard on the solenoids, because it keeps pulsing them, and comes in so soft it cant plant the tires on the launch, the best way is bring into a full transfer on motor then hit it hard 100% that plants the tires in the transfer, then add stages.

 

Looks like a good kit. If Spin were closer to me, I'd give this a go, but as it is, I am very worried about finding someone to tune it and don't have the time to learn to do myself.

Spin, want to move to Houston?

 

I'm there!

I've been in turbo cars, blower cars and even stroker cars but I can honestly say that even though I have at least 6 friends that either use or have used nitrous over the years, I've never been in a car when they've hit it so it will be a new experience for me.

 

Yeah looks like a much better deal.

 

They say you should never dyno NOS
Mike

 

I just got got back from the Cherry Hill meet there were several guys with NOS Vito, Rob, Nick, etc all running dry shots with no tune and running the nos before the MAF with no issues they are all running 100 to 125 shots with no issues I tried to explain to them
A dry shot need to be tuned! I made myself look stupid because
there they are, the cars sittting in front of me.
They dont understand why it costs 2500$ for the NOS and set up.
Im not sure I do either? I think Im gonna do it myself. and save 2 grand. The kit I bought has all the safety stuff so. I set my Z28 up with 175 wet shot and had no issues. I have HPTunes Ill do a scan
with the Shot and see if I need to pull timing. as long as I run 93 Sunoco and a little octane boost if needed, shouldnt have to do anything with the timing. Ill run a #6 plug like the other guys and go from there.
I think we overcomplicate thing sometimes. the more I read the confused I get. Im going with my gut on this one.
With such a small shot I cant see spending that kind of money.
If it was a 2 stage 250 200 then it makes a little more sense.
Just my 2 cents. Who knows after I get the NOS hooked up
I may change my mind or add another stage. Then might be a better
time to bring a guy like Spin to work his magic.
Mike

 

I usually dont research medical surgery techniques before surgery having to know the ins and outs of what a doctor does to remove a disc. I just look at the stats and trust in the docs ability. I dont go to 5 doctors arguing over what surgical instruments they prefer. Pick one that is proficient with his choice of tools.

If you give the list of parts to a tuner to do the same install, he will quote you 1500 more than 2500 for the same job. Shopping price gave you a lost opportunity.

 

The MAF maxes out on the C6 with shots over a point and the typical concentrated shot isnt going to have the same top to bottm fueling with the aim at the sensor method. Under 175 shots its a no brainer to go dry. Wet shot lovers say the dry shot rely's too much on the stock fuel system as if wet shots dont. A failed fuel pump will kill a supercharged, nitrous, or turbo engine just as fast. Would you rather trust a fuel injector or a fuel solenoid? Solenoids fail way more often. Intake manifolds arent designed to flow fluids...period. Lastly on the reliability issue, this sytem doesnt rely on the MAF for all its fueling.

As for what is included with a tuner installed package is a bigger set of fuel injectors because you will be over 100% duty cycle ( you are at 390rwhp now with your mods and a 100 shot would put you at 490rwhp and thats a maxed out set of stock fuel injectors when you have to run 12:1 or richer at WOT) (injectors absolutely must be tuned in), nitrous pressure guage and sending unit, a bottle warmer, and fuel pressure sensor to cut out the solenoids if your rail pressure drops, a window switch so you dont activate too low in rpm or hit off the rev limiter and the fuel cuttoff causes a lean condition, switch for thumb activation to go in and out of a shot without releasing the gas pedal, a timing retard module to pull 1.5 degrees for each 50hp you run, a WOT switch, a remote bottle opener, and a first bottle fill at 50 bucks. The number of hours to install such a system is 2 full days. Labor these days would account for 1000-1600 with tuning and the parts list is very close to 2000 with all the needed parts. You can skip the bottle opener and heater to save 450 or so but it isnt what was quoted for you.

Kit: 550
Injectors: 400
bottle opener: 225
bottle heater: 220
nitrous pressure guage : 170
Window Switch: 100
Shifter activation: 70
Bottle fill: 50-75 10 or 15lb bottle
Spin IAT Control module: 20 bucks homemade-eliminates timing module and MAF for fueling--takes a few hours to assemble with getting parts. All free for friends.
Shipping to get all the above: 40?
$1800 for parts and 500 (250 a day) for install and 200 to tune. thats a far cry from the 100 an hour asked of most shops.

Wet shots are 1500 installed with my pricing for friends...that eliminates the fuel injectors.

Anyone see the bargain here? Anyway you look at it, the kit I was proposing was a gift.

Another thing to understand is that the way the system I typed about above isnt relying on a MAF for fuel and definitely monitors all aspects of the system. The system control module I make, while simple, isnt easy to make for most people. Going in blind isnt that uncommon. Nor are bad installs all that uncommon. No form of FI is a DIY project for a first time set-up. Anyone who told you to install a nitrous sytem without a tune is not anyone I would ask for advice on anything.

The above parts list and labor isnt 500 bucks. The system you are looking at doesnt have even the minimum safety items included.
Running a tune for nitrous all the time is still a tune and you cant optimize both sets of parameters at the samer time unless its a system that triggers only while firing as my system does. Anyway you will see from start to finish, the number of hours involved with an install. Few people will want to touch your car if you need help after the fact. Fixing mistakes is much more time consuming than just doing the install. You had some issues with the FAST install and I would rate that much easier than a N2O system. I think you are making a mistake. Dry shots are way harder to install then wet. If you aim the nozzle wrong and it heads over the element, you will be pricing a motor swap.

One peice of advice for the other window shoppers. Sooner or later you have to trust in one source for your mods. You go for a test drive in the R&D car that has your mods and you stop listening to the guys that tell you to skip safety things. That tuner has to have a similar perspecive of price vs quality. When a trust is formed, you stop asking 10 different sources about what direction to go with mods. It will keep you sane at the minimum. I'm not in business to do this stuff. I try to help people to get more for their money and do installs as if it was my own car. It took months of testing before I did a real nitrous shot in my car and even then it was massive testing and tuning before I used a shot that was even strong enough to feel. I have seen 3 cars in person that blew a motor among my friends who thought it was simple enough to do themselves. I recall them saying how easy it was back when I was anti-NOS. I envision all those guys on youtube that had nitrous backfires bragging how easy it was to install too.

...but then, I did mine on my own so you shouldnt have a problem.

 

Wet shots are so much more simple that a parts seller will want to keep you from biting off more than you can chew by telling you to get a wet shot. You dont have to know how to tune it or worry about how much fuel injector you need to use. You dont have to worry about aiming nozzles or calculating injector duty cycle. All you do is put in the jet that they tell you to use for the size shot you pick. No one tells you about bottle presure, window switches, bottle heaters.....lots less to go wrong until you get to the fuel solenoid that can leak or not fire. You also dont hear them talk about fuel puddling. Its peace of mind. Its not that common to get a nitrous backfire with a wet shot. Roll the dice!! You likely wont be on youtube putting out the flames. Nitrous backfires never matter to people until its their car. They are the guys that tell you they have nitrous for 5 years and went through 100 bottles and never had an issue. That means all wet shots are safe right? The cars that dont fail are always the important ones.....thats what we use for statistics right?...the cars with no issues. Ask dry shot guys for the things they had problems with. Dry shot owners always find themselves having to defend the dry shot and where are their failures?

Whats the worst that can happen with a wet shot?

Wet shots are not as safe as dry shots. If you still doubt that at this point, you're lost.

 

I felt it necessary to state that direct port nitrous systems which are wet shots are very safe. Such systems use 8 nozzles at the locations on the intake manifold to inject the nitrous and fuel where the fuel injector also operates.

Such systems are nade by top line tuners such as ECS. I was there once years ago when they had prepped an intake manifold for such a system. It was a work of art. Perhaps Doug or Chris have pics to post. In this system the 8 ports all put fuel in directly without any fuel flowing through the intake manifold. Its expensive but has no limits as far as how big the shot can be....other than your shortblock.

One way to make such sytems or regular wet shots safer is to use a harris speed works box to help with fuel delivery to the motor while making the fuel solenoid responsible for less delivery. This unit works just like my IAT tricker in that it uses the MAF connection to add fuel and pull timing. If one sytem fails the other is still adding some fuel and may be just enough to avoid a big failure.

 

Spin

does it make a difference if you already have a cam in the car when adding NOS ?

Thanks

 

No, all cams amke 100hp on a 100 shot. Big overlap doesnt hurt WOT performance. It only affects part throttle where you cant use nitrous.

 

A little nitrous backfire/explosion is not a problem...a little Zaino and some elbow grease will take that right out.