Discuss all things tuning in this section. News, products, problems and results.
It would be great for us to get a quick view in how to get started tuning a car running on NOS that would be a great webinar.
What do u guys think?
It's a great idea! Obviously we are a little limited based on what we have access to at the time, however I'll keep it in mind and you never know what might come up.
The reality though is that tuning nitrous isn't that challenging or different. It's similar to any other power adder and needs to be treated the same. My general starting point is to retard the ignition timing by about 2 degrees per 50 hp shot of nitrous - This should be a safe starting point if your aspirated tune is on point.
As for the fuel delivery, personally I prefer to use a dry shot and add the additional fuel with the ECU via a 4D overlay table or similar. This gives a lot more control than a fogger system can give. I always found that the recommended jetting ends up far too rich and then you need to mess around changing jets to get the tune right. I just find this easier and faster using the ECU however obviously you need sufficient headroom in your fuel system to cope. As far as AFR goes, I tend to treat the engine like a turbo engine and run the same sort of AFR I would in that situation.
One last point - If you are using a decent shot of nitrous (anything above about 75 hp), you may want to be a little wary of activating the nitrous if the rpm is too low. The amount of nitrous introduced to the cylinder is larger at low rpm since the intake valve is open for longer and if your engine can;t handle the extra cylinder pressure it may not end well. On larger shots I generally don't allow the nitrous to activate until approximately 4000 rpm.
Great reply thanks for that!!
that was one of my concerns that the nitrous beeing activated on the lower rpm parts with there's little load and more ign advance.
I think that's where the ecu's options comes into play i guess with setting up options that only enable the shot above centain rpm's/throttle/load like u said.
But i get the concept.
i'm going to thread jack slightly.
when running a small shot for Anti-lag purposes (on at 2000rpm and off at 15psi) how do you size the shot?
I under stand you have to limit cylinder pressures but this isn't easily recorded for most people, so do you just need to check for knock?
I thought a 35hp shot would be ok for a cast piston motor?
If you're using the nitrous for antilag then it's a little different. Generally the size of shot is going to be much smaller - perhaps 50-75 hp. If this is the case then you can bring the nitrous in from say 2000 rpm or thereabouts with no real danger since the shot is quite small. The danger would be doing the same sort of thing with a larger shot of perhaps 200 + hp. Of course all of this is dependent on the strength of your engine anyway. The cylinder pressure from nitrous will put a lot more load on the piston and rods so these need to be up to the task. If your engine has known weaknesses in these areas, any amount of nitrous may be a bad idea.
When using nitrous for antilag, it will typically be activated by the ECU using a window switch. This might mean that the nitrous becomes active above say 2500 rpm, 80% throttle and 100 kPa, and then shuts off as soon as boost reaches perhaps 180 kPa. Once the turbo initially begins to spool it becomes self supporting with the increasing exhaust mass flow resulting in more turbine speed, more boost and hence more exhaust flow. This means the nitrous isn't needed for very long.
Just wondering.. If i was to add nitrous on a NA engine tuned to (mild) 250ish hp on E85, would it still be necessary to retard ignition by 2 degrees every 50hp shot of Nx?
SALtech its always safe to retard a couple deg and look at the torque what is doing as you increase the timing little by little .
It will really depend on where the knock threshold sits with your particular engine SALtech, and that is going to depend on the fuel, the compression ratio and a number of other parameters. It's always safest to start by retarding the timing and then try adding it back in and see how it effects the torque and if the engine is knock limited.