start psi question

[Laz93RX7]

in the manual it says this will be the psi that the pump will start to operate, but then it says to adjust 25% of vehicles maximum boost? can anyone explain? this I'm a little confused with this.

[NS]

The START PSI adjustment is the amount of boost that needs to be present before the system will start injecting.  As a generic rule of thumb, we recommend that this starting point be about 25% of your max boost pressure.  So, if you're making 16 psi of boost a good starting point would be about 4 psi which is 25% of your max boost pressure.  From here the system will ramp up and increase the duty cycle of the pump until it goes to full injection at whatever you have your FULL PSI adjustment set to.

[Laz93RX7]

may sound stupid, but what if I dont want it to start pumping til about 12-13 psi?

[NS]

Mind telling me why you want it coming on that late?  What's your max boost pressure?

[Laz93RX7]

max boost is 15psi, dont really know how long 1gal will last spraying so early. just want it to let me squeeze of a little more boost. (Sorry forgot to mention its for a 93' Mazda RX-7)

[NS]

During normal street driving you'll find that a gallon will proabably last you 50%-75% of a full tank of gas.  Starting the injection so late totally defeats the purpose of having a progressive system.  At this point it's basically on or off.  If you don't need it to start at 4 psi then have it come on later but 12-13 psi is too late IMO.  Just play with it and see what works best.

[Quijinn]

I was wondering this as well. Prob going to use this system on my stealth. I normally see 6-8psi in the hilly areas around here, car runs 16 psi on 93 want to run the full 22 psi. Was thinking I could set it at around 8-10 psi as the start so in normal driving it would not kick on, much. Does this sound outside the realm of logic for the system? Also with the check valve does this mean instant spray action?? The turbos can spool super fast in the winter, so fast I cant get the AEM to compensate to keep from overboosting, this system should have np keeping up right??

[TheBoz2]

There have been lots of tests about this.  The best results happen when the Meth/Water come on sooner.  There are also lots of way to inject Meth/Water.  So for me I start spraying my 50/50 Meth/Water at 5psi, and progress to about 20psi.

Anything less that 5psi would make my system start to spray when I really dont need it, like going up hill on the freeway.

[NS]

Water/methanol injection is just like an EMS.  There is no single black-and-white, 100%-true-to-all answer.  You tune it to how you need it to work for YOU and YOUR application.  If you notice slight ping or high IATs during low boost without injection then lower the injection point and have the system start spraying sooner.  Too much on the top end?  Reduce your injection by turning your full adjust higher to decrease the final pump duty cycle.