Yet another Aquamist jet size question

[mosk]

First, thanks very much to Richard and Ed for sponsoring this forum! It is an excellent resource for WI information.

I am very close to purchasing a 2d system (along with a DDS2) and want to be sure I have the proper range of jet sizes, as I'd like to order everything at once.

I've read and re-read all of the jet size posts on this forum, and still have a few questions.

My motor is a 2.4L turbocharged Toyota 4 cyl with a front mount intercooler, controlled by a standalone EMS (a SpeedPro/F.A.S.T. system with closed-loop wideband O2, so my target AFR and AFR readings are accurate). The intercooler appears to be fairly efficient, as my average inlet air temp under boost is around 40?F (22?C) above ambient, for a max observed of 110?F (43?C) as measured in the plenum.

I am using 4 X 550 cc/min injectors. We are currently running a max of 15 psi. To do this without pinging, I have been running a very rich 10.0:1 AFR above 11 psi, and have also been forced to reduce timing advance to 9? above 11 psi. From everything I've read here, this motor should be a good candidate for WI :)

If I want a max IDC of 80% (an IDC value that most tuners seem to feel is "safe"), then using the formula:

injector size * number of cylinders * max IDC * WI percentage

I get:

550 * 4 * .8 * .15 = 264 cc/min, using the updated chart in this post (http://waterinjection.info/phpBB2/viewtopic.php?t=217). This would put me at either a .6mm or .7MM jet.

Is this correct? Am I close? Because I am currently using so much fuel above 11 psi to cool the intake mixture, I am reluctant to use my current IDC numbers as the basis of any WI calculation, as I believe with proper WI I will be able to run much closer to 11.5:1 - 12.5:1. instead of my current 10.0:1.

Thanks for your time and help,

Jeff

[mx5]

I get:

550 * 4 * .8 * .15 = 264 cc/min, using the updated chart in this post (http://waterinjection.info/phpBB2/viewtopic.php?t=217). This would put me at either a .6mm or .7MM jet.



No. The 2D kit mirrors a fuel injector IDC to maintain a constant water to fuel ratio. So the calculation in your case for 15% water is just 550*4*.15 = 330 cc/min you're supposed to achieve that with a 1.0mm jet.
It is sortoff iffy though because IMHO over the different IDC the bigger jets don't flow proportionally to the IDC change because of the pressure drop. Then you probably need a priming pump to be sure the water % is constant over the IDC range with a big jet - otherwise at longer IDC the pump can't keep up with the jet and alters the water to fuel ratio.

Wrong section though - Aquamist questions go in the ERL/Aquamist section - because Richard monitors and answers there a lot. Probably at some point he will see this thread here and answer too though ...

[mosk]

No. The 2D kit mirriors a fuel injector IDC to maintain a constant water to fuel ratio. So the calculation in your case is just 550*4*.15 = 330 cc/min you're supposed to achieve that with a 1.0mm jet

Well, I guess this is the crux of my question: is water jet size calculated using 100% fuel injector duty cycle, or is it calculated using the actual max IDC that you will see in use? Because the stated size of the fuel injectors is calculated based on 100% IDC at a static fuel pressure of 43.5 psi, but no one in their right mind runs their injectors at 100% IDC; 80% is considered safe, and 90% is about the max you can get away with before repeated use at this level burns up the injector. Also, fuel pressure fluctuates based on boost pressure, which affects the amount of fuel being delivered, so at 15 psi (or 2 bar) of boost, I am seeing a fuel pressure of greater than 43 psi. So I was ASSuming that I would also calculate WI jet size using some sort of offset from 100% IDC. If this is incorrect and I can just toss out all of these other variables, great! I know the benefit of the 2d system is that it ties WI DC to FI DC, so I'm just trying to get a handle on the right set of variables to consider. If I can use fewer variables to get the correct result, so much the better!

-Jeff

[mx5]

Yes it ties the IDC of the water and fuel. So if you see max 80% fuel IDC, then your max water DC with the 2D kit is also 80%. the HSV valve is driven by the fuel injector switched ground. You can't change that.

In the tables/graphs the listed water jet flow is at 100% DC just like the fuel injectors flow are listed at 100%. What the water jet flow at 80% DC will be - I doubt anyone can answer you that and you can't find a table listing it. Probably your best choice is to make a setup which triggers the wire at 80% DC and measure the water flowing ;)

[mosk]

Well, that would sure make things easier, as I wasn't looking forward to working through all of the variables. :)

BTW, I did a quick re-check of the updated chart:

http://www.aquamist.co.uk/forum/flowrate4.gif

It looks like 330 cc/min puts me closer to a .9 mm jet.

Also, thanks for your reply,

Jeff

[Charged Performance]

That is correct with a system 2d you want the flow potential at the jet to a target ratio of your injection system. The 2d will then reference your IDC and when they are both for instance running at 80% then you will get around your target ratio of water/fuel - in this case the 264 you calculated.

What this means to you is that you do want the flow potential of 330cc, but as long as you aren't going over 80% IDC you won't ever use more than 264cc (aquamist pump max is 300cc without an accumulator or priming pump).

The 330 point is actually the 1.0mm jet (labels are to the right of the point, not above).

I would consider an accumulator just to make sure you have some overhead on the pump potential.

[mosk]

Thanks, Ed, that's very helpful. An accumulator was already on my list as a safeguard, and this reinforces that decision.

It will be interesting to see if WI will let me get closer to the full potential of these 550 cc injectors on this motor. As things stand now, I'm glad I have them because I have to dump quite a bit of extra fuel into the mix above 11 psi to keep things stable, but my current situation makes running aything more than 15 psi a very bad idea. Hopefully, WI will let me use that extra fuel for power instead of mixture stability.

--Jeff

PS: I'll be contacting you next week to place an order. :D