Jump to content

Water injection control, miata PnP


Recommended Posts

Hi all,

I've been searching for some time now but I can't find an answer to my query. I have an aquamist HFS3 water injection system I plan on installing.
There are various control strategies that can be used to control the aquamist HFS3. MAP with RPM, or injector duty cycle with MAP, etc. 
I believe I need either an RPM output or injector output, or ideally a configurable extra injector driver (with programmable duty cycle map).  An extra fueling map (such as for controlling a 5th injector) would be ideal since it would allow complete control of the water injection i.e when it activates (load/rpm) and water flow rates. 

My previous ecu was e-manage ultimate, and despite its failings (as a piggy ecu) it did have an extra independently configurable map ("sub injector map", independent of fuel injector control map) that could be used to drive a high speed valve controller, which I used. I understand the G4+ will probably require a different control strategy since I can't find any reference to a 5th injector map or equivalent. 

HFS3 manual

Can anyone recommend an workable approach?  At minimum it looks like I need an injector signal, and I'd rather not splice into an existing injector wire. i.e. could I program one of the G4+ outputs to achieve this, and just run the duty cycle signal wire from the G4+ to the engine bay? Can the G4+ output a MAP signal (so I don't have to install an extra map sensor) that could be used as input to the aquamist system? How about RPM signal?
Also, it would be handy to be able to control when the high speed valve (water injection) activates from pc link, if its possible. 

If there are no extra map features, then I'll just need to input MAP signal and injector duty cycle. Rather than installing another map sensor and splicing into the fuel injector harness, if the G4+ can output these signals then that would be a great plus. 

I could try the age old trial and error approach by accessing the G4+ and checking the configurable outputs, but I'd imagine the seasoned experts here could advise me! 
Any suggestion would be much appreciated, thank you!

Link to comment
Share on other sites

I would prefer to control the entire water meth system with link ecu itself. Bypassing the aquamist control box. Our ecu is more than capable of controlling water meth.

Select an unused output, configure it as GP output, use condition 1 AND 2 (MAP and RPM) and you get to select whichever rpm/map you want the meth to start spraying. Use an external 30A relay to run the water meth pump controlled with the ecu output.

You can then use 4D ignition and fuel to trim fueling and timing when water meth is running.

Link to comment
Share on other sites

Ah, there it is! Just found the GP PWM DC map in the auxiliary output settings tree. Hadn't even seen that there before!  Lots to work with now, thanks very much for the assistance fellas, you've really helped me a lot.  I'm amazed at the versatility of the G4+. 

Edited by Aaron99
Link to comment
Share on other sites

  • 3 months later...


I've finally installed the aquamist HFS-3 water injection system and is all up and running. Controlled by the GP PWM map. Been up and running for about a week now on my MX5, no problems. 



So this is one way to control the water injection via G4+. 


Edited by Aaron99
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...