nitrous tuning

[gp406Z]

I have a 406sbc that I`ve got running well with the FAST system and I`m ready to use my wet nitrous kit. I know the jetting will be on the rich side and I need to know how to correct it. Should I leave it in closed loop,allowing max rich/lean correction,overlay that and aply how much it corrects to my VE or should I jet down the fuel side of the kit? Again allowing max corrrection till I get the desired A/F. I know it should not be allowed to remove fuel in the top/WOT rows of the table and was wondering if I could do it this way to tune,then disable that correction when it`s right.

Also, my kit uses an arming switch,WOT switch,and fuel pressure safety switch for operation.How should I wire in FAST ?

Thanks
Glen

 

[bobbyp]

I have set my car to run nitrous also, I wired per the manual and everthing works fine. I did not run a safety cutoff on mine but I believe the correct way to wire it would be to place it in series with your arming circuit. Fast will not trigger the nos relay unless it sees the system is armed. I have not had a change to run my car since installing nos, but my understanding is that the fast system will attempt to hold the af ratio that you program in at the nos table regarless of the ve tables or the af tables.
Please email me when you get it up and going as I have never had any feed back on my nos questions either
thanks
bobby patterson
bobbyp@lakemartin.net

 

[bobc455]

I recommend that you don't try to control the A/F when on nitrous- run open loop.

Instead, set the FP on the nitrous system according to your manufacturer's recommended setting as a starter, and then tune from there according to your spark plugs. (Of course first your VE table should be tuned so you get less than 5% correction at WOT!)

I tried to run in closed loop, and for whatever reason, the motor didn't like it (boom!) even though it showed 11.8 as the leanest the engine was running on the juice. I am not going to trust the O2 reading on nitrous until I regain some trust.

If you do run in open loop, it doesn't matter how you activate it- a pushbutton on your shifter should be fine. If you do want the FAST to activate it, you need +12V to the arming signal, then when the FAST wants to activate the N2O it will ground it's output- hook this to the "trigger" ground on a relay that will activate your nitrous solenoids. Using a microswitch is not necessary since the TPS has a minimum threshold where FAST activates the nitrous output, but if you want to be safe you could wire it in series with the ground output from the FAST. The fuel pressure safety switch should be in series with the nitrous activation wire from the FAST.

-Bob Cunningham
bobc@gnttype.org