12A EFI nitrous: What do you think of this?
 

Personally I don't LIKE nitrous since it has to be refilled, but I'm going
to run it on my 12A soon after it's fuel injected (megasquirt.)

The nitrous/fuel charge will be delivered through Holly's new "NOSzle" found
here. http://www.holley.com/HiOctn/ProdLin...OS/NOSzle.html I
believe from everything I've found, that standard bottle pressures/fuel
pressures these noszles will only allow me to run 30 to at the MAX 50hp
worth of nitrous per unit. I'll be running 2, so plan on a 50ish shot with
extra extra fuel at first, and a max of 80-90hp, also jetted significantly
richer than standard safe jet settings.

As with other wet nos systems I've implemented in the past, I'll have
several safety margins. EFI fuel pump in the under-hood surge will be
plenty large to feed the 4 720 cc injectors and the nos.

Safety/system designs: Standard system with WOT switch and "arm" switch
both having to be on for the system to come on.

Another rpm activated switch/relay won't allow the nitrous below
4000-4500rpm, undecided on exact rpm yet but common thinking is that at
higher rpm a certain sized shot won't stress the motor as much.

Power to the nitrous solonoid will also be cut by the rev limiter. A double
throw relay will be wired with the normally closed circuit ran to the
nitrous solonoid. The rev limiter will first trigger this relay, cutting
power to the nitrous solonoid if it was running at the time, and the other
circuit that would then get closed is what will actually carry the other
trigger to cut power to the ignition.

Power will not be able to reach the nitrous solonoid UNTIL fuel pressure is
seen PAST the fuel solonoid. In other words, once all conditions are met
for the system to trigger, the fuel solonoid will get power, a fuel pressure
(hobbs) between the fuel solonoid and the delivery orfice will have to
close, allowing power to flow to the nitrous solonoid. I may stick another
hobbs switch in the fuel side to only allow the system to come on if fuel
pressure is above a certain level.

Any input? Primary questions revolve around just how little stress it might
be putting on the motor if it only comes on at such a higher rpm and timing.
I plan on locking the timing, and I believe I can engineer it for some
retard when the nitrous is on or suffer the loss of bottom end :) if I
retard it across the board for track duty. Anyone have a spare '80+ dizzy
sitting around I can play with?

R

clutch
 

Will also have a clutch and brake switch, if either one is touched, no NAAAAWS.

I'll just call it MazdaVVT-N2Oi, like Honda's VTEC, to passengers. Car will run up to the rpm trigger point and CLICK, start pulling harder. :)

It's nice to hear that you'll at least be doing it right.

Agree, sounds real good. What are you going to use to activate it - the actual switch?

I personally like the WOT switches on the floor below the accelarator.

Yes, arm swith and WOT switch will be the 2 things from in the car that make it happen.

Trying to rule out potential failures and make it trustworthy. Might put two nitrous solonoids in series as well, if one hung that'd be the worst thing that could still happen.

Any input on timing? I hear lots of NA cars even in stock form can run locked timing and not have any performance problems, only give up a bit of bottom end and fuel economy. Anyone with a dizzy handy picture what I might do to make it retardable under signal? Basically lock it with the centrifugal advance locked in, but have a vacuum can push it back retarded, sucking the weights back in. :)

R

Another thought if you got this far:

If you could draw up anything you wanted, what would your EFI 12A intake manifold look like? :-)

At first I'll be violating a '79 carb manifold for efi.

If I was to setup EFI on my car I'd use twin IDA style throttle bodies and a Weber manifold.

As for the timing, you could also get an ignition control box that has built in retard for nitrous. Like one of the MSD's.

YEP.
http://www.msdignition.com/images/pn6462.gif

MSD 6BTM, PN 6462
Supercharged or turbo engines will benefit from the 6BTM in more ways than one. Not only do the full energy sparks help burn the fuel mixture, it allows the driver to retard the ignition timing based on the amount of boost being produced by the supercharger. The timing is adjusted from a dash
mounted knob and can be retarded 1 - 3° per pound of boost with a maximum of 15°. There is also a built-in adjustable rev control to protect the engine from over-rev damage.

OR, Better yet..

DIGITAL DONE RIGHT!

http://www.msdignition.com/images/8975.gif

MSD Digital Multi-Retard
The new Digital Multi-Retard provides four different stages of retard along with an adjustable start/retard feature - all with no modules!
The MSD Multi-Retard uses a high speed RISC micro-controller to direct and timing functions. This RISC processor can make extremely quick adjustments to the timing signals while still keeping accuracy to within 1°. These circuits are thoroughly debounced and isolated for protection against Electro-Magnetic Interference (EMI). There is also a new innovative Magnetic Pickup Compensation circuit added to allow perfect timing with a variety of magnetic pickup triggers. See the sidebar for more information.

Activates up to four separate stages of retard independently.
Adjustable start retard feature- 5°, 10°, 15°, and 20° options.
New Magnetic Pickup Compensation circuit for perfect timing.


The Multi-Retard has four separate retard stages, perfect for multi-stage nitrous applications, and they can be activated independently or together for a total sum of retards. Each stage is adjustable from 0° to 9° and the maximum amount of retard is 20°. The Start/Retard feature allows retard timing for ease of starting. Since all engines are different, the unit can be programmed for 5°, 10°, 15° or 20° of retard during starting.

MSD Digital Multi-Retard PN 8975*
Not legal for sale or use on emission controlled vehicles.

Very similar to the 13B-REW manifold, but with a few design cues from the new Renesis manifold.