NOS Control

[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.

I look forward to a replay and any information or other web sites you can diret me to that may be of assistance.

Fred from Guam.

 

[tstom]

Fred,
I think you will find more gains by turning your nitrous on full much sooner in the run At that power level the only reason to ramp the nitrous would be traction problems even so you would be better of to run a smaller shot and turn it on sooner To see the logic of this compare your 0-1/8 mile time to your 1/8 to 1/4 mile time a typical 9.90 car will run aprox. 6.40 in the eight so you are spending about 64% of the run in the first half of the track
We use a throttle stop timer and turn our first system on at .05 sec from the release of the trans brake and spray the whole run if we don't need to run as fast we just use a smaller tune-up
The timing retard seems reasonable but we usually pull a couple extra degrees out on a new combination to give us a chance to sneak up on it nitrous will perform amazing well with a little too much timing out and the worst that will happen with too much retard is it will miss a little ....not enough and you'll be changing pistons
Make sure you use spark plugs with a short fat side strap and a standard tip ( not projected) You said you had Brodix heads so an AR2592 is what I would recommend
If you retard much more that 6 deg you will begin to run into rotor phasing problems as you will begin to swing the rotor off of the contact in the cap then you must go to crank trigger ign. so rotor position becomes independent of ign timing
I would think a four link Vega would handle a 150 hp shot without much trouble right from the starting line......hang on!

Tom

 

[Guam]

Tom

Thanks for helping a fellow racer. We have a crank trigger ignition so we shouldn’t have any problem in the retarding and rotor phasing. Fortunately our car is hooking ok and we have been very consistent with 6.25/30 1/8-mile times. With the BBC churning a bunch of torque the car is really putting out on a short wheel base to at least the 60ft mark so we wanted to delay the spray a bit until we were well hooked up. I see your point and we may start to spray a bit earlier.

I’m interested in your viewpoint on jets. We purchased the manifold and wet NOS system from a guy running a full NOS 540 ci BBC motor. The jets it came with are 32 NOS and 102 gas. The gas jet are throwing us off as all the jet/hp indicator charts we have don’t reference gas jets that large. With the 32 NOS jets the best calculation we came up with was about 270/300 hp. Can you suggest a NOS and Gas jet combination to start us off at about 150 /200 shot.

Regards,

Fred from Guam

 

[tstom]

Fred,
A 102 gas jet is definitely not right regardlees of what nozzle you have Your assumption that a 32 nos jet is about 270 to 300 hp is pretty close for 150 to 200 try a 24 nos jet and a 20 fuel jet but before you do this please describe to me which nozzle you are using... NOS has about 4 different nozzles and the tuneup varies a little for each
the particular difference is in tip design also you want 6.5 lbs of fuel pressure flowing through a .070- .073 orfice and about 950 to 1000 lbs of bottle pressure when you leave the starting line
Delaying the hit about .1 to .2 from the brake release should give the car time to get hooked and still give you a nice e.t. jump

Tom

 

[Guam]

Tom

Thanks for the reply. I'll stop by the shop tonight and get the info and revert.

Fred from Guam

 

[Guam]

Tom

We found out that the102 jet I mentioned earlier was the only mis-match in the jet pack we got from the owner of the system and the rest of the jets were in a sensible range including 22 and 24’s. I should have looked a bit closer at the whole combo. I did look at the NOS nozzle and there are no ID numbers on the nozzle. It has the NOS brand mark and then designators for the gas and nitrous sides of the union. Can you describe what I should be looking for in the tip and I’ll come back with a description of what I have. We are getting close to installing the system and any information will be greatly appreciated.

Regards from Guam

Fred

 

[tstom]

Fred,
There are basically four type of NOS nozzles We can narrow it down like this if the nozzles are black in color they are either an "A" nozzle or a "B" nozzle the A's have a V shaped notch on the discharge end the B's have two small holes , one angled, one perpendicular to the nozzle
The other two are stainless bodies one discharges straight out of the end of the nozzle with what looks like a cutting torch tip this is an annular nozzle the second stainless body has a rectangular notch on the side of the nozzle they are called soft plume nozzles The tune ups are all slightly different sorry it took me a while to respond ....hope I'm not too late

Tom

 

[Guam]

Tom

We have plastic nozzels with two holes. Will this help with your suggestions.

Regards,

Fred

 

[tstom]

Fred,
Are they manufactured by NOS? Maybe you could email me a picture, particularly of the tip tom@hemphillracingengines.com

Tom