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Link G4+ Modelled fueling

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I currently run the Silver box G4 Extreme in a Subaru STi. My map currently has fueling mapped MGP vs. RPM. Fuel/IGN table 1 is my pump gas map, Fuel/IGN table 2 was my pump + meth map. The Maps where switched via a digital out from the meth injection system. My question is could I still do something like that with the G4+ Extreme if I used Modelled-Multi fuel equation and I mapped fuel TPS vs. RPM in the main table and MGP vs. RPM in a 4 D overlay? I would like to tune for E85 flex fuel but would also like to keep the meth injection map switching ability also. Are the 4D overlays common to both Fuel table 1 and Fuel table 2 or do you have separate overlay maps for each.

Why would you want to map a single throttle body boosted engine on TPS? I know some people will but I'm curios for your reason to change.

The 4D tables are active at all times unless you give them an activation protocol, you can see this in the G4 software too, they are usually used for changes in the VE of the engine, i.e. your AVCS.

With the G4+ Xtreme you can use flexi fuel, that way the amount of ethanol or methanol is measured (or at least the conductivity of the fuel is measured) and will interpolate between E85(MAP1), pump fuel(MAP2) and methanol dosed fuel(somewhere in the middle between MAP1 & MAP2)

I run large overlap cams with no AVCS and its hard to get fueling right at idle and low load. BAP/MAP crossover was suggested to help improve idle. Even with the multi-fuel interpolation I would like to add another overlay map on both the pump gas and the E85 maps that would be triggered when the methanol injection is active. The overlays applied to fuel/Ign table 1 and 2 need to be different though and be able to be activated by a DI input.

What you could have is 4d for one of them and 5d for the other with different activation parameters.

When your at idle and low load do you get pulsation in your map trace?

Actually TPS as the main load axis does give some advantages on a single throttle turbo engine and I went to the trouble of writing some custom code to do this in M1 Build on our 86 turbo.

If you run MAP as most do, the results are going to be great but you will notice if you go to full throttle/full boost and then reduce the throttle opening the AFR will usually go richer than target. This is because the turbo is so good at producing boost that the boost pressure (which is the ECU's load input) remains the same until you get down to perhaps 50-60% TPS. Despite the boost remaining constant, closing the throttle reduces the engine's VE and hence the AFR moves rich. TPS as the main load with an openloop AFR table (in the Link G4 ECU) and possibly a 4D compensation if you move outside the turbo efficiency works exceptionally well and maintains a constant AFR at these part throttle openings.

With that out of the way, I'm guessing you're not going to use the methanol injection when you're using E85? You could use a 4D/5D comp map as Chris suggested to compensate for the methanol injection. You could also use E% as a parameter to allow the meth injection to become active. To answer your other question the 4D/5D compensations will function on both maps.

So if the fuel equation mode is set to BAP/MAP Xover, is it necessary to map your primary load axis as TPS. I would need a separate overlay maps for pump gas and one for E85 due to the difference in VE from the added cooling right? I guess I could swap between the pump and E85 overlay table at some defined ethanol content. When running pump gas though I would like the ability to run an alternate ignition map when spraying methanol. I don't think I have the tables for all that.

"If you run MAP as most do, the results are going to be great but you will notice if you go to full throttle/full boost and then reduce the throttle opening the AFR will usually go richer than target. This is because the turbo is so good at producing boost that the boost pressure (which is the ECU's load input) remains the same until you get down to perhaps 50-60% TPS. Despite the boost remaining constant, closing the throttle reduces the engine's VE and hence the AFR moves rich. TPS as the main load with an openloop AFR table (in the Link G4 ECU) and possibly a 4D compensation if you move outside the turbo efficiency works exceptionally well and maintains a constant AFR at these part throttle openings."

Hello Andre,

Thanks for that tip... but shouldn't this issue be compensated for by using throttle-based boost control? If we reduce TPS% then the boost target should move down and fuel supply lowered accordingly through the Main Fuel table (with MAP on the load axis).

Anyway, I use throttle-based boost control but I get the issue you are describing when modulating the throttle mostly with the engine running under vacuum, and I have not been able whatsoever to solve that issue. All 5D tables are used already (EGT and Gear), and we have no Deceleration Enleanment with the Link software. Adjusting Accel Enrichement settings has proven so far as fruitful as peeing in a violin ;-(

Andre can you please elaborate setting up TPS as load axis. What axis do you use then on openloop target table and on ignition table?

How to deal with barometric compensation on this setup?

Axis setup and barometric compensation is still something that I'm struggling with. A webinar would be great on this topic!

I made the follow experience:

If I tune the fuel map in stady state on a MGP setup, the engine runs much leaner on the road during transition of the part load map. Thats very likely to see in Datalogs, during accelaration out of a race track corner.

In stady state the turbo has much more time to produce boost, hence you reaching the same MGP whit less throtle. It's like a "lean spool function" on the race track. :-P

Car runs fine, but feel detonation can get a problem during this lean situations. Especially if you tuned to the knock limit on stady state.

What engine is this your talking about Adrian? as different engines require different approaches.

To change the axis in the Link software you firstly open the table you want to change the axis on, press 'X' and then choose which axis you want to change and select it from the menu.

Once this has been done you need to initialise the axis by pressing 'Init axis' this will give a simple 0-100% in 10% increment axis.

If you look at the picture I've attached you'll see a screen grab of the menu, the axis has already been initialised.

There is also a webinar dedicated to the acceleration enrichment for the Link software which can be found here in the archive:

https://www.hpacademy.com/previous-webinars/038-configuring-and-tuning-acceleration-enrichment-on-a-link-g4/

This should help you with your transitional areas.

Attached Files

Thanks Chris, but I have nearly every possible setting an possibility on the PC link in the memory of my head ;-) so my question is unique to tuning.

Yes, I should have mentioned that. Single throttle, turbo engine.

The lean transition has nothing to do with acceleration enrichment (no sudden TPS change). Andre covered the problem from the other side pretty well. You can reach full boost also with only 60-70% TPS. If you tune on stady state you reach (slowly) full boost with only 70% TPS. You tune the cell to the target with only 70%TPS. If you apply full throttle now, you stay in the same cell, but mixture goes lean.

Same happens in the part load. In staedy RPM 4000rpm boost reach lets say 50kpa on MGP axis with 40% throttle. But the ECU uses also the same cell If you accelerating quickly trough the cell in low gear with WOT. So you have 100% throttle trough the cell you tuned in stady rpm but only with part throttle, because the turbo needs time to spool.

So same cell once with 40% TPS and once with 100% TPS >>> conclusion: runs lean on 100% TPS and same boost.

Have a look at this webinar on 4D tuning with the G4+ - https://www.hpacademy.com/previous-webinars/4d-tuning-link-g4-plus/

The basics are that you use TPS as the load axis for the fuel/efficiency table. The fuel equation needs to be Load = MAP so that the ECU does a background compensation for manifold pressure. You can then use the open loop AFR table with MAP as the load axis to set your target AFR - Note that open loop AFR needs to be turned on for this to work. This table then makes a correction to the fuel pulse width based on your target lambda. If this is set up and tuned properly it's incredibly effective. What you'll find is that once you start pushing the turbo really hard and turbine inlet pressure increases, the measured AFR starts drifting richer than target. I use a 4D compensation with MAP and RPM as axis to correct this.

Watch the webinar and let me know if you have further questions. Note that this is an essential technique on multi throttle turbo engines but seldom is it used with a single throttle/plenum.

I just watched the Webinar, again very helpful.

I would like to know what would the difference be if I use MAP as the load axis for the fuel/efficiency table then use the TPS as the compensation with 4D tuning turned on? so the opposite...