Spray Bars are Crap

Draco1340

Registered
OK, so I intentionally want to stir the pot on this post and get some new views on the pros and cons of Dry nitrous and spray bars, but I do think they are grossly flawed and this is why.

First, I will readily admit that a bar will make more HP than a well designed fog system. If I spray 15 ounces of spray during a pass, I will definitely make more power with a bar. Fogging the box makes power by dropping the temperature (and thus the density of the total charge), and it makes power by adding 33% O2 in place of 20.9% O2. Spray bars make power using these two methods, but they also use phase change. A well designed bar can shoot liquid at or past the valve, allowing MUCH more liquid 33% O2 into the chamber. So, I readily admit that bars can make more power. Its a fact.

Here is the problem. If you have a bar, its because you want a big hit. You shouldn't waste your money on a 30 or 40 shot. You can easily fog for that small amount. Lets say you build a motor to take a 100 shot with your bar. This means you have to progressively launch the spray through your bar. You can't leave the line with a 300 shot (at least not without bars and a 10 inch slick). You can't turn it on in second gear. Hell, a 100 shot will blow you over. It needs to be progressively launched, and this is were things start to get hard on your parts. The intake valves are opening almost 100 times a second. 11k RPM /60 / 2 = 92 Hz. The nitrous solenoid operates at 25 Hz. That 1/4 the frequency of the intake valve. This means sometimes the valve opens and sees enormous amounts of liquid nitrous squirting down the pipe, and sometimes is sees almost none. During the time that you progressively ramp from say 40% to 100%, your motor is slamming back and forth between super lean and super rich. But your O2 sensor in the tail pipe is just averaging everything out between all of the cylinders and all of the firing. Most loggers (like my Innovate) only collect data at 25 Hz, so you will never see this rich lean condition.

But this is the reason why nitrous has such a bad reputation as being tough on motors. If you only shoot a 40 or 50 shot, it probably doesn't make a difference. If you don't progressively ramp your shot (like many land speed guys), you won't have a problem. But, If you have a 100 shot and you ramp the shot the whole length of the track, you will beat the hell out of your motor. Mini detonation beat the ring lands, wrist pins, and rod bearing. The extra torsional vibration on the crank from running rich / lean cracks cranks. A good fogging system isn't affected by the nitrous solenoid clacking along at 25 Hz. They cylinders see a smooth ramp of increasing N2O gas.

My Gen II motor had almost 2000 passes on stock rods, crank, pistons with a progressive 80 - 100 Shot through a fogger. When I took it apart, The rod bearings looked brand new, and the roundness of the big end was better than a tenth. The wrist pins had almost no wear at the point they contact the little end. The pistons and ring lands had no sign of detonation. People will tell you you can't run 300 hp on stock rods with spray, but it can be done. I just wouldn't do it with a spray bar.

I know this argument tends to boil down to a Chevy vs. Ford argument, but I wanted to add some engineering reasons behind fogging.
 
So you sound like you know alot about nitrous. I will say up front I am new to the nitrous thing so I am just trying to learn.

I have purchased a 42hp wet shot, I have seen many ways to set this system up, however, I want it to be the most effiecient and safest way for my engine to handle.

I liked the looks of the spray bar sold on here that had 2 tubes aimed at each throttle body and I was thinking that was the way to go, however reading this I am not sure???

What is a fogger? Will it work with a wet shot? and how?
 
Wet systems are great, and I have used them for years, but doing a wet system with a double spray bar is double crap.

A well designed traditional nitrous nozzle is located way down in the intake runner well below the fuel injector, and doesn't interfere with the flow of the FI. The nozzle is designed to use the high pressure of the nitrous to atomize and disperse the fuel. There is plenty of room below the throttle bodies on the back of the cylinder head to install nozzles on your hayabusa, but it really is a pain to do it with the head on the bike. It can be done, but its a pain. The other nice thing about traditional N2O injectors, is that the jets are only an inch from the spray point. If you pulse your nitrous and fuel solenoids with a progressive system, the short length of pressure drop keeps the fuel and nitrous in proper proportion more or less. A spray bar system has the spray exit many inches from the jet, resulting in more rich / lean pulsing resulting in broken motor parts. A wet dual spray bar system doesn't use the nitrous pressure to propel and atomize the fuel properly. I would not recommend it. People sell and use these systems because they are all in the air box and easy to install. That's the only thing going for them. Do it right and buy 4 high quality nitrous injector and put it high in your intake runner pointed at the septum of the port split.
 

An old thread that argues (correctly) that spray bars make 10 - 15% more power than foggers for the same jet size. That's absolutely correct, but you can always go with a bigger jet if you need to. Don't progressively pulse a spray bar or you will blow stuff up. This thread also argues that bars are more convenient than injectors that tap into the head. Also true, but rebuilding motors is more inconvenient.

Again, if your not running a progressive controller and a shot over 50HP, then spray bars are not a problem.
 
This is what happens when you fog the airbox. The Nitrous goes everywhere first, then it goes into the velocity stacks.

fog.jpg
 
An old thread that argues (correctly) that spray bars make 10 - 15% more power than foggers for the same jet size. That's absolutely correct, but you can always go with a bigger jet if you need to. Don't progressively pulse a spray bar or you will blow stuff up. This thread also argues that bars are more convenient than injectors that tap into the head. Also true, but rebuilding motors is more inconvenient.

Again, if your not running a progressive controller and a shot over 50HP, then spray bars are not a problem.

So you just contradicted yourself with your own title that says spraybars are crap.
 
So you just contradicted yourself with your own title that says spraybars are crap.

Hardly Gixx.

Making power with Nitrous is the easy part. Spray bars make power. Big deal. They are still crap.

Going rounds with a reliable 300+ HP bike that safely makes power is the objective. Spray bars propagate the myth that nitrous bikes are time bombs that can't reliably go fast and win races. The myth that any joker looking for a cheap short cut can bolt a bottle and go fast once or twice.

If your real about N2O and you wish to reliably shoot 50, 60 100 HP, then you will need to progressivly launch the bike. If you cycle those nitrous solenoids, you will eventually blow your motor due to rich / lean cycling. I hate to keep helping people on motor rebuilds.

Your bridge photo was very pretty btw.

Tom Peterson
 
With everyone preaching the power of spray bars, I thought I would get some debate.:hmmm:
Isn't there someone out there racing a points series going deep into rounds running a 100 shot with one of these things?
The only argument I hear has something to do with the golden gate bridge.
Stand up for your bars!
 
This seems way wrong.

If your cycling a wet kit you'll be cycling both noids, a dry just the nitrous and depending on how your setup the fuel will remain rich, at worst run 2 tables with your ramp. how is that ever ending up lean?

How is a 4 nozzle kit in the intake or head any different from a spray bar?

seems allowing nitrous to be pulsed into a cloud of varying density would make correct metering tougher.
 
With everyone preaching the power of spray bars, I thought I would get some debate.:hmmm:
Isn't there someone out there racing a points series going deep into rounds running a 100 shot with one of these things?
The only argument I hear has something to do with the golden gate bridge.
Stand up for your bars!

Why should I? They have been proven time and time again. I am not so easily baited and hooked on someone's idiom and disbeliefs
 
This seems way wrong.

If your cycling a wet kit you'll be cycling both noids, a dry just the nitrous and depending on how your setup the fuel will remain rich, at worst run 2 tables with your ramp. how is that ever ending up lean?

How is a 4 nozzle kit in the intake or head any different from a spray bar?

seems allowing nitrous to be pulsed into a cloud of varying density would make correct metering tougher.

Ridgeway,

Fair question, and if you are spraying a 40 shot and you tuned for 100% duty cycle on the solenoid, your fine. If you ramp a 40 shot at 50% duty cycle, it just runs a bit rich, but not enough to break up. But if you have a big shot you can't tune for that, because the motor will fall on its face if you cycle a 100 shot at 40% duty cycle. Way too rich, and the motor will dangerously break up. If you tune on a dyno or with a logger for the ramp with a big shot, then the lambda sensor is just taking the average of the rich / lean cycling. Agin, the nitrous solenoid is cylcling at 1/4 the frequency of the intake valve, and the motor will eventually tear itself apart as it cycles both rich and lean.

Your other question is also good. A traditional nitrous jet takes the big lazy fuel jets coming out at 4 - 10 psi and blasts them with 1000 psi and atomizes them. The wet spray bar systems just spits the fuel at low pressure. Not great, but not that much of a problem. The bigger problem is the distance from the restricting oriface to the outlet of the tube. The shorter the distance, the less the flow surge during pulsing. THe relatively long distance from oriface to opening, causes the N20 and particulary the fuel to surge badly. You will notice that all of the videos of the wet and dry spray bars don't show a 2 second ramp from 40% to 100%.

I'm not baiting. I'm debaiting. And its not ideoms and beliefs. Its engineering and science. Plus I hate to see all my budies continue to blow there ****e up, and I REALY hate to keep rebuilding them.

Tom
 
Hey LOOK! 4 Plumes must mean a bunch of power?
Can you please address the problems associated with progressivly launching with a spray bar, or are you only interested in pushing this stuff?:rofl:



C141.jpg
 
There are none. Just to give you an example. I launch my Busa at 6000 rpm. I progress from the launch and in first gear. Starting percentage is 20% and ramp to 100% in 4.5 seconds. I spray a 150 shot.
 
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