Fuel table 1 vs AFR/Lambda table

[MarcusV]

Hi,

I've started to dial in my car and diving in to the system and it's possibilities and there is one question I want to ask about fuel maps.

According to my understanding, most stand-alones on my platform use a fuel map which utilizes the WBO and load (MAP) for adjusting, with the predefined AFR as a result.

I'd like to comprehend the principle of two different fuel maps in the Link, and ultimately use them both correctly.

For starters I noticed the instructions stating that turbocharged engines shouldn't rely on the MAP as the load source in the Fuel map 1. So now I have my fuel map 1 using the TPS and the AFR/Lambda with the MGP as it's source.

What's the correlation of these two maps and is the Fuel map 1 truly necessary?

What I really learned today is that the TPS/RPM combination seems to be fast enough for flooring the throttle quickly, but what role does the AFR/Lambda play in the entire setting?

Thanks again!

 

[Vaughan]

Most engines run well using MAP for load. The exception is engines which have very little vacuum or erratic vacuum/MAP readings which is typically engines with Individual throttle bodies (ITBS) as the lack of plenum between the throttle body and intake valves mean the pressure varies massively over each intake stroke making it very hard to figure out how much air is entering the cylinder based on the air pressure. The setups with TPS/RPM on the main fuel table and a MAP correction on a 4d table are typically for turbocharged engines with ITBs as the same throttle position with a higher air pressure in front of the throttle body will flow more air and so needs to be accounted for in the fueling, examples of this kind of engine would be the RB26DETT and the SR20DET that came in the GTIR pulsar.

The AFR/Lambda target table (if Open Loop Lambda correction is on or if using a Modelled fuel mode) is used as a multiplier on top of the main fuel table so that when the main fuel table is tuned correctly (and the injector deadtimes & spwa are correct) to match the AFR/Lambda target table the actual AFR/Lambda can be changed simply by changing the AFR/Lambda target with no other corrections needed. It is also very useful as a reference when you are tuning and looking at logs for seeing if the AFR/Lambda being seen by the wideband is where you want it to be.

[Electredge]

I often use TPS as load when tuning a track car, as 100% throttle needs more fuel than 70% throttle... but it will often read the same Manifold Pressure

[MarcusV]

Great info! My car is a Dodge Stealth RT/TT (3000gt VR4 equivalent) so I do have a plenum. The car ran with a piggyback before and the fuel map was TPS/RPM only. What I did learn yesterday reading the manual, the autotune used AFR/Lambda map to adjust the Fuel 1 table. IDK if they both need to use pressure for load in that case. I guess it would be beneficial for both maps to be with similar sources.

[Adamw]

For a turbo engine like this with a plenum and single throttle your best option will be MGP on both the fuel table axis and lambda target table axis.  

[Pete_89t2]

8 hours ago, Adamw said:

For a turbo engine like this with a plenum and single throttle your best option will be MGP on both the fuel table axis and lambda target table axis.  

@Adamw - Curious as to why MGP on both tables is the preferred load axes in this case, as opposed to having MAP on the AFR/Lambda Target table and MGP on the Fuel Table?

While my car is very different being a rotary (13B-REW), it shares similar characteristics to this one, namely being turbocharged, with a single throttle plate (GM DBW, 90mm) and a plenum (using the 13B-RE Cosmo upper & lower intake mani). I could be completely wrong, but I thought it was best to use MAP on the AFR/Lambda target table, in order to correct for altitude, and then use MGP on the Fuel table?

[Electredge]

2 hours ago, Pete_89t2 said:

@Adamw - Curious as to why MGP on both tables is the preferred load axes in this case, as opposed to having MAP on the AFR/Lambda Target table and MGP on the Fuel Table?

While my car is very different being a rotary (13B-REW), it shares similar characteristics to this one, namely being turbocharged, with a single throttle plate (GM DBW, 90mm) and a plenum (using the 13B-RE Cosmo upper & lower intake mani). I could be completely wrong, but I thought it was best to use MAP on the AFR/Lambda target table, in order to correct for altitude, and then use MGP on the Fuel table?

MGP is basically MAP but includes the BARO offset, so if tuned using MGP... in theory you should be able to travel up and down a mountain without any problems. 

[MarcusV]

So far I'm pretty much out of luck tuning my car with the MGP Fuel table 1.

Actually I can't get it to rev freely without the engine bogging down when I lightly touch the pedal. The car goes lean no matter what I do. On top of that the quick tune wants to adjust it to the leanest possible setting nevertheless what I set to the AFR/Lambda map. For example 0.800 lambda turns into +1.200..

The TPS/RPM option works fine though, I can rev it to +6000rpm with just the right settings and actually even drive the car. So I guess I'll just start my season with that and develop the pressure map later when the time and motivation serves me right.