Haltech Nexus Injector Staging
 

How is Nexus staging different from Elite style? What are you running for settings on Nexus Style?

For the last few years I've adjusted the staging on an Elite 2500 in attempts to identify the location in the RPM range that provided a balance between the following:
- keeping primary injectors below 90% max duty cycle, i.e. I experimented with staging approaching 100% primary duty cycle.
- staging in secondary injectors so they were in a reasonable starting point relative to their injector duty cycle operating range, i.e. I experimented with staging below 5% primary duty cycle thus secondaries coming in and attempting 1% duty cycle.
- and placing the staging at a point in the rpm range that it became as unnoticeable as possible to driver
- along with this I attempted to get the AFR's to stay as flat as possible, close to target, from the pre-stage through post-stage portions of the rpm / boost range

I did this using of stock injectors 550/850 as well as ID 1050/2000.

I found that getting the Elite staging to work required getting the staging tables setup well but when done the fuel map would appear as if you were not staging at all, i.e. the change in fuel through the rpm range where staging was happening was just as if no staging was happening behind the scenes, that is it just looked like you had primary injectors that did all the work with very nice smooth fuel curves. The less perfect the staging tables the more "non-smooth" changes would be visible in the fuel table. I was able to get the 550/850 Elite staging very smooth in multiple rpm locations and the Nexus staging had NOT become available while I was using those injectors.

Once I changed to the 1050/2000 combination I started with the Elite staging and had it working fairly well when it was higher in the rpm / boost range. But I was maxing out the staging tables for a setup when the staging was low in boost / rpm range and I was compensating via adjustments in the fuel map, thus there was an obvious step in the portions of the fuel map where staging was happening. While I was able to reasonably achieve the goals above I wasn't pleased with the slightly less smooth AFR line through the staging transition and there was just a hint of staging feeling while driving.

When Nexus staging became available I tried it. I believe I am using it correctly and I think it validated my Elite staging tune was close. The biggest thing I noticed is that without staging maps the fuel map does all the work that the "behind he scenes Nexus staging" doesn't handle. Thus the fuel map "makes more common sense" as the steps in the portion of the fuel map, relative to staging, are still there. For my situation they seem to make sense and when I see a high/low AFR datapoint, a change to the appropriate fuel cell causes the AFR to change as expected. Also the AFR line through the staging transition is smoother and the hint of staging feeling while driving is gone. Since Nexus staging is relatively new, and I have since removed the engine for updates, I haven't tried other rpm / boost locations to see how the fuel map changes relative to staging needs in those rpm/boost locations. But, so far I prefer the Nexus staging to the Elite staging.

Happy for the Nexus fuel staging!
 

Nexus Injector staging works great!
Before it came out I couldn't get my AFRs 100% dialed in during the pri. and sec injectors transition w/Elite staging it was close... about 90% close.
And now w/Nexus it butter smooth :icon_tup:
I heard its similar to the Adaptronic ECU fuel staging which the creator of it, Andy now works for Haltech.

Glad Haltech updated to bring it out for the Elite ECUs


Steve

Sorry if this is a stupid question, but I am planning on getting the Haltech 2500 in the near future for a single turbo swap. Is the Nexus Fuel staging a function of a new software update the pushed out to the Elite 1500/2500 and Nexus product line or is it a hardware upgrade that is exclusive to only the new Nexus ECU?

The new Nexus ECU looks great, but probably way more than I would need for just a street car.

^Its been alittle while since it came out but I think it was a firmware/software update for the Elite ECUs.
So it’s not a hardware upgrade. Hope that helps.

Steve

It is a firmware/software upgrade. Took me about 30 minutes start to finish.

I switched to Nexus style staging as well. I could never quite get my Elite-style staging transitions to be super smooth or get the AFRs where I want them when the 2nd stage transitions.

When I switched to the Nexus style, I didn't make any adjustments. Just selected it the drop down in the menu and started driving/tuning. It removed the transition enrichment tables that I was previously adjusting. I did have to tune my VE table in the range where the 2nd stage would activate, I had to lean out the entire area by a fair amount.

Overall it has been a pleasant experience so far, almost too easy. Makes me feel like I'm probably missing something, but all the data shows it is where it should be.

When the ecu does the maths properly the VE tables should be smooth reflecting air movement behaviour, previously the main table was compensating for the simple staging logic.

Not necessarily. Remember injectors under 45% duty are not linear. So when the primary or secondary injector is working through this area you will see odd changes in your VE.

Is staging really needed anymore for cars with fueling requirements under 500whp? Injectors and ECUs have come a long way since Mazda decided to use staging.

what is the benefit these days, unless going for massive power while trying to get drivability.

More homogeneous charge mix, Andy from adaptronic specifically tested that on his own personal 13b and then renesis if I recall correctly. Better efficiency/torque/emissions if you bring secondaries in sooner than near max primary flow provided you are decently above dead time transition of the secondaries for control/runner control transitions.

ecus have come a long way which means you can stage runners ports and injectors, will port wall fuel film models and target a balanced air fuel mix in each flow path. More power and better response from the same airflow.

I'm saying something different. You can size your injectors properly, and they can be controlled well below their max capacity (e.g. you can make an ID 1700 injector idle the car as well as a stock 550.

So if you don't have crazy fueling requirements, why not run ID 1300 in both primary and secondary locations and just leave them on all the time. They give a little fuel when you need it and a lot when you need it. No staging.

Best torque at low rpm will be with only primary runners flowing air.
If you are running an IDA or 4 barrel without staged throttles, I agree all at once is probably better.

Only the primary runners flow air at low rpm?

It you set it up right.

This is true of the oem throttle body. Although I'm not sure at what percentage it opens up the secondaries. I believe it's fairly low, but the consensus is that it improves low end torque because of the higher air velocity which results in better air/fuel mix.

If you have your injectors calibrated properly in the software this shouldn't be an issue. The calibration would indicate the non linearity and the ecu would be able to use that data to adjust the the injector timing as needed. A lot of people don't configure their injectors properly but it's well worth it if you want consistent tuning.

No it doesn't. There are no tables to account for it. Populating flow rates vs Differential pressure and Injector dead times does not account for it.

Where are you getting the 45% number from? That seems very high.

http://injectordynamics.com/articles/low-pulse-tech/

Injector linearity has nothing to do with duty cycle. It’s purely a function of pulse width. Most good, modern injectors have good linearity above 1.5ms.

Curious to get your thoughts on staging C.Ludwig. Assuming the stock secondary throttle stuff is gone (I switched to ProJay), with a good ecu and new style injectors, is there any point in staging? Assuming around 500whp on pump and using primary and secondary injectors of the same size (maybe ID1700?).

Ideally, you’ll want injectors close to the port and further up the runner. So staged injection has merit in any application. Personally, on a street driven NA, I prefer the simplicity of a single stage in the primary location. On a turbo car, where you need the fuel, then staged makes a lot of sense. The injector close to the port makes throttle transients better and an injector further up the runner can, at least in theory, provide better fuel distribution, charge cooling, and mass ram effect.

Staging Duty Cycle, affect when different?
 

My car is together again and I've been dialing in the tune for the new stuff. Still using the ID 1050/2000 injectors. The issue I've had since ESP days is a few tenths of a second lean/rich transition as the secondaries come online. This issue is still happening on NSP, not as bad but still noticeable. So far I've been using the same value for both Staging Duty Cycle settings. I've tried 40, 32, 24, and 20. The staging moves as expected to different location in the fuel map and the lean/rich transition follows. I haven't seen any Haltech documentation of the usage of the setting other than the blue question mark pop-up. I think my next experiments will be to try different values such as 20 primary, 32 secondary, or vice versa, with the mindset that the NSP algorithm being used will act somewhat differently bringing the secondaries online with the values being different. What I'm hoping for is to find some setting that ramps the secondaries up to 5% or so more quickly. I say this because the logs show them ramping up slowly and while they are under 2 / 3% the lean condition happens and then up to 3.5 / 5% the rich condition happens. Once past this point the primaries/secondaries work well together and fueling follows the map settings well. Have any of you guys experiments with this setting and or seen other documentation?