Guam

I’m looking for some assistance with port injected NOS for drag racing. Our team has a lot of experience with naturally aspirated racing engines and some experience with NOS on fogger plates in four cylinder low H/P applications. Our strategy is to continue with mostly an all motor (engine) program but we want to be able to apply a limited amount of NOS from time to time when we need a bit of a boost, mostly for setting records.

We have purchased an Edelbrock Victor intake that has single stage NOS port/runner injection. We also have a NOS controller. We are plan on using NOS in a small dose. 100/150 shot. The NOS will be run through a controller and be applied in a ramping process. We plan on applying 20% at the 60 ft mark or approximately 1.4 to 1.5 seconds into the run and then ramp the feed to 100% by 6.3 seconds. This will allow for 100% of NOS to be on for approximately 1 second at the top end of the track prior to crossing the finish line.

The basic car specifications are:

S/G Vega, 2400 lbs, full frame, 4 link tube back half, box frame, tube front end, rack pinion steering, 15x32x15 rear tire, Glide, 5600 stall, 496 PRO Series Shafiroff, 14:1 compression, Brodix heads, Victor intake, 1050 Dominator, Crane R-274/4334-2s-10 intake lift @ .737 exhaust lift @ 726, MSD ignition @ 36 degrees advance lock downed, 1.7 ratio rockers, all electronics, throttle stop.

Weather specifications:

We race a track that is at sea level. Temp is 85 to 95 degrees and humidity is in the 70 to 85% zone on average. (Guam USA).

Questions:

We understand that for every 50 hp of NOS we should retard the engine 2 degrees. Is this a correct assumption?

Does anyone have way ideas on controlling the retard in the same progressive curve as we plan on applying the

NOS. Is it important to ramp the retard, as we apply NOS in a ramp?

Our question/concern is based on our controller (and all the ones we have researched) only has the ability to send one signal to our retard box. Based on a 150hp shot of NOS and 2 degrees retard per 50 hp of NOS applied, we will need to pull 6 degrees of ignition timing our to the engine as the NOS controller comes on and begins the initial ramp at 20%. We have designed a system that could easily manage the ramping of the NOS and retard but it is based on RPM control which we don’t want to got to based on if you have any wheel spin the RPM would naturally increase which will apply more NOS creating more wheel spin.

Technoman64

iTrader: (6)

I build the NOS controllers and also motorcycle ignition/nitrous controllers. In the bike igntions I use a progressive retard with build times that are adjustable just like the build time on the nitrous ramp. However, we have nothing for automotive apps. You can use the MSD multi-stage retard and activate the first stage off from the Progressive controller +12V actiavtion signal. Then activate a second stage at approx. 1/2 of the Nitrous build time using the +12V Output Timer. With some of the retard boxes it may be neccasary to connect a 150ohm, 1/2 watt resistor from the #2 Ground terminimal to the #4 +12V output terminal to insure that the retard remains OFF until the output goes to +12V. There is a 470ohm, 1/2 watt internal pull-down(to ground) resistor on the #4 terminal, sometimes this is not enough of a ground source though. I believe they upped the current requirements to improve electrical noise immunity. This is in regards to the NOS 15834 5-dial Progressive controller. Based on your description this is the one you have.
On another note, I usually run more timing retard than I think I need to start with. The main side effect of this is a lazy engine in the top gears. It is much easier to slowly add more timing than replace components from a blown engine. We take the PRO-MOD bike engines from 34* down to 10-14* withing 3.5 seconds as a typical setup. These are running #40-44 nitrous jets to each cylinder though. A typical Top-Gas application would be a 100hp shot with 26-28* total timing by the time the nitrous is at 100% power.
I do not claim to be an expert on the tuning end of things, this just my .02 worth based on my experiances.

T/A Medic

iTrader: (1)

with a 150 shot, why bother doing it progressively...? squeeze it out of the hole with your 6 degrees of retard... if u were going with a 250 or 300 shot + the progressive would work great if ur traction limited. Or u can do dual stage nitrous if u want to go that big... 100/150 1st stage... 100/150 second etc etc.

try it simple with 150 out of the hole see if u even have traction issues... then go from there

Technoman64

iTrader: (6)

I love my personnal throttle proportional nitrous system. The fact that I can control the amount of nitrous injected at what time, rpm, and how hard I am hitting the gas is great. I have several guys using progressive controllers in ET bracket racing as well as PRO classes(Cars and Bikes). With a dual ramp controller in ET bracket racing you can take the nitrous to 100% over time(much easier on stuff and/or limited traction issues) and then bring it back to 70-80% power. If you flup up on the tree or miss a gear you can use a 100% power override button to run somebody down instead of running just behind them at the big end of the track. You set your ET off from a normal run without using the override power adder. You still have to decide wether or not you are breaking out but at least you have an option in bracket/ET racing.
I aggree that if traction is not an issue you can use a dual stage setup. We are taking bikes to the 6.60 second range at 200mph with a 11" slick. Just normally asperated with nitrous. The PRO-MOD nitrous bikes are running better times now than the Turbo/Nitrous/Alchohol Funny Bikes.
Again this is just my .02 worth, feel free to use what you are comfortable with.

Guam

Thanks a bunch for the input. I'm sure to be back with more questions as NOS is a whole new game for the team and we'll need some ideas.