Flow Control Valves vs. Water Injection Kits

[Dustin Mustangs]

I guess this is a multi-part question. First, do these two parts do the same thing? From what I understand they both regulate water going into the exhaust in relation to engine speed. The difference being that the valve does this indirectly by way of pressure in the cooling system and the injection kit works directly off of engine rpm. Is this correct??

Secondly, given they do perform the same function, which does a better job? The valve is much simpler (good from a k.i.s.s. standpoint) and also much more affordable. I guess the injection kits can have multiple injection points but couldn't you just use multiple control valves and get the same effect?? Given what a flow control valve does, I am surprised anyone even buys the injection kits with how pricey and complicated they are. I must be missing something here...

Lastly, is either a worthy mod for a stock boat? How about a mild limited??

I'm interested to hear what you guys have to say about these questions or any other thoughts you may have on the subject.

:Thinkingof_:

TIA

Examples:

Flow Control Valve:
http://www.jetworks.net/fc123.htm

Water Injection Kit:
http://www.jetworks.net/wik123.htm

EDIT: I just noticed the flow control valve page I posted claims it is compatible with water injection kits. If I wasn't confused before I am now...

 

[dbrutherford]

I have a flow control valve. Some swear by it but in the grand scheme of things I barely noticed a change in power with it.

A flow control valve goes in the cooling line that attaches to the stinger on the pipe. Its purpose is to block this flow at water at low RPM's in effect drying out the water box. This is supposed to provide you with more low end snap as the engine has a more free flowing exhaust system not having to push all that water out of the water box. Once the RPM's increase, the pressure in the cooling system increases and the valve is opened up by the pressure. It is only closed by a spring. The cooling system and exhaust function normally as if the flow control valve wasn't there.


Now a water injection system uses a selonoid that is opened by a controller at a specific set RPM. The selonoid lets cooling water then be sprayed into the exhaust pipe via a fitting. When the cut off RPM is reached, the controller shuts off the selonoid which shuts off the water into the exhaust. Water injection systems are commonly used on dry pipes which do not spray any water into the exhuast pipe until the stinger fitting. These pipes are jacketed so they are cooled by water in this jacket. Just like how the water jackets work on an engine. All other pipes have a small hole or holes at points inside the pipe that spray enough water into the exhaust pipe to cool it preventing the couplers from melting. The speed of the returning sound wave from the tail cone is dependent on the temperature of the exhaust since sound waves move at different speeds through a gas at different temperatures. So when you spray water into the exhaust pipe, you are lowering the temperature slowing down the return sound wave. This will give you more low end. Same principal how the Factory Pipe Products exhaust head pipe works with its three adjuster screws. However a water injection system can be varied to turn on and off at different RPM's via the controller where the the FPP head pipe adjusters are at the same openings for all the RPM range when riding.

I hope this clears up the differences between the two. I too am curious how well a water injection system works. I did once ride a Kawasaki 750 SXi Pro that had a FPP dry pipe with water injection. That ski ripped in the mid range! But the low end snap I look for since I am more into freestlye/freeride just wasn't there. I was always told that drying a pipe out provided more power. But everyone seems to sell dry pipes with a water injection system. Then those systems are programmed to come on say from 1500 RPM to 6500 RPM. That to me is the useable powerband of a two stroke jet ski engine. Usually only race engines are run in the 7500 to 9000 RPM range. So for a freestyle/freeride jet ski just save yourself the weight of a dry pipoe and run a wet pipe, IMO. Dry pipes are pretty heavy since they are two pipes in one bacsically because of the jacket. Then again I would like to try a dry pipe with water injection or just a wet pipe with one.

 

[Dustin Mustangs]

Ok, the light just came on. The valve lowers/stops flow at low rpms to keep the water box dry as a way of increasing off idle power/response. The controller kit lowers/stops flow at high rpm to increase heat in the pipe which increases wave speed effectively shortening the pipe and tailoring it more for peak power. They basically do the same thing but during different conditions and for different reasons. Correct?

:thinkerg:

 

[Matt_E]

They basically do the same thing but during different conditions and for different reasons. Correct?

Incorrect.

Water injection makes the exhaust a wet pipe with an effectively variable-length chamber, providing for a wider powerband.

A flow control valve on the stinger reduces back pressure.

Not the same thing.

 

[sflsurfrider]

Lastly, is either a worthy mod for a stock boat? How about a mild limited??

theres really no place to put a fcv on a stock-piped yamaha engine.

 

[WFO Speedracer]

It really dosen't have to do with drying the pipe out,injecting water slows the wave in the pipe down,which effectivly makes the pipe seem longer which increases bottom end power,taking away the water makes the pipe effectivly seem shorter which creates more top end power.Water injection is a way to get the widest possible useable powerband out of your pipe.It does have to be ste up to go along with your porting setup to get the most out of this system.:wavey:

 

[dbrutherford]

I bought a used West Coast pipe for an old X2 I had and it had a spot for a water injection nozzle. Then again it never originally came with one... the previous owner drilled and tapped the pipe for it. I am not too familiar with Yamaha pipes but I suppose you could drill/tap or weld a bung on there for a fitting?

Water injection systems are typically used on dry pipes to get back the low end that is lost due to the pipe being dry ie hotter. Also it doesn't take much water limiting to burn up a coupler... I know, I learned the hard way...

 

[WFO Speedracer]

I drilled and tapped one into a Kawi STS 750 pipe I am using on a Seacouch,I am actually using the water regulator off of a Seadoo as it is all self contained and works off of water pressure.Pretty simple setup and is somewhat adjustable.

 

[ItsRixter]

There seems to be a bit of contrast on water injection compared to the flow control valve. Water injection shoots water in a low rpms and cuts off at high rpms while flow control value does the opposite by cutting water off at low speeds and opens up at high speeds.

I am one of the few that love the FP type 4 dry pipe for freeriding. Yes the pipe offers huge bottom end. I had a stock 98 SJ with just air filters and carb jets per FP instructions. Nothing else...no cdi, no modified head etc and the thing ripped. The issue is maintenace as the coupler blew out afetr a few seasons. I noticed the spray nozzel appeared clogged also...perhaps part of the isue?

Back to the point. I have two superjets right now and both have b pipes (the dry pipe is screaming to be installed). I just put in a jetworks flow control valkue and will run it this weekend. It does the oppsoite of what the water injection did. I'd like to hear from those that ran BOTH setups and provide feedback (as I will after my first ride with a flow control value). I'd really like to hear Chuck's (supertune) response to this water exhaust question.

 

[chasingdaylight]

There seems to be a bit of contrast on water injection compared to the flow control valve. Water injection shoots water in a low rpms and cuts off at high rpms while flow control value does the opposite by cutting water off at low speeds and opens up at high speeds.

I am one of the few that love the FP type 4 dry pipe for freeriding. Yes the pipe offers huge bottom end. I had a stock 98 SJ with just air filters and carb jets per FP instructions. Nothing else...no cdi, no modified head etc and the thing ripped. The issue is maintenace as the coupler blew out afetr a few seasons. I noticed the spray nozzel appeared clogged also...perhaps part of the isue?

Back to the point. I have two superjets right now and both have b pipes (the dry pipe is screaming to be installed). I just put in a jetworks flow control valkue and will run it this weekend. It does the oppsoite of what the water injection did. I'd like to hear from those that ran BOTH setups and provide feedback (as I will after my first ride with a flow control value). I'd really like to hear Chuck's (supertune) response to this water exhaust question.

You have several very good points... The type 4 dry with injection is a great set up but it's big and bulkey .. I've gathered the info from chuck that the dry is better but the b-pipe is overall a great pipe set up for most applications... Hate to anwser for him but big power needs a big dry pipe set up.. both will work well with 900cc or less motors.
I'm am build a dry pipe fx baby scream with dry pipe and water injection...

 

[WaveDemon]

I'm going to use them together... in the same routing/system

I've got a junker head pipe that I'm installing a spray nozzle in. I'm going to put a Mcmaster-car flow control valve in after the nozzle so the nozzle has as much pressure as possible to have the best spray possible. I'll put an adjustable valve before the nozzle to tune the volume of water.

 

[Dustin Mustangs]

I'm going to put a Mcmaster-car flow control valve...

Curious to see what they have along these lines... do you know the pn off hand???

 

[WaveDemon]

curious to see what they have along these lines... Do you know the pn off hand???

48935k35

 

[ItsRixter]

I'm going to use them together... in the same routing/system

I've got a junker head pipe that I'm installing a spray nozzle in. I'm going to put a Mcmaster-car flow control valve in after the nozzle so the nozzle has as much pressure as possible to have the best spray possible. I'll put an adjustable valve before the nozzle to tune the volume of water.

Are you serious??? Real curious how that works Demon.

 

[WaveDemon]

Are you serious??? Real curious how that works Demon.

I'm serious. I'm hoping to have this on my boat in the next couple of weeks.

 

[ItsRixter]

Whwn is Chuck the expert going to chime in? :scratchchin:

 

[SJBrit]

There are a lot of comments here about water injection and flow controls valves doing the same thing, and some really good explanations about why this is not the case and how water injection works. But just to be clear, all a flow control valve does is to stop the waterbox filling up at low revs. When you hit the throttle off idle the first thing the motor has to do is hawk out all that water in the waterbox before it can breath right and make power. A flow control valve just keeps the motor's nostrils free from snot so it can breath properly :bigok:

 

[FlightPlanDan]

There are a lot of comments here about water injection and flow controls valves doing the same thing, and some really good explanations about why this is not the case and how water injection works. But just to be clear, all a flow control valve does is to stop the waterbox filling up at low revs. When you hit the throttle off idle the first thing the motor has to do is hawk out all that water in the waterbox before it can breath right and make power. A flow control valve just keeps the motor's nostrils free from snot so it can breath properly :bigok:

This is my exact understanding of th FCV. It has very little or nothing to do with the pipe. The water it lets pass goes directly (almost) into the water box. No change in power. Just a little quicker low end throttle response cause you've not been loading the water box while idleing or putting around to set up.
If the water box is kept empty at lower rpm's the motor doesn't have to push it out b4 responding.

Some have complained of the heat melting tanks etc... I've not experienced this.

I would like to understand injection, but I've no experience with it.
I think the 2 mods are VERY different.

 

[Big Kahuna]

Designed for racing to keep the waterbox dry at the start. If you notice 2 strokes at the line, they get blown out, this expells all the excess water in the waterboxes. The FCV's help to keep the boxes dry after the blowout and before the band pops.

 

[FlightPlanDan]

Right, but it also helps in surfriding/tricks. Ex: aproaching a wave slowly to flip...need the bottom to snap quick..

Is Water injection just for dry-pipes? (keep in mind, I know nothing about injection) It seems that you have considerable control of water in a b-pipe.
Wouldn't you risk motor damage with a dry pipe?
Soory for jacking....same subject?