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Discussion Starter · #1 ·
hey im learning to tune i have read tons of articles and threads, but im really only starting, my car is idling around 17-18 right now, and is lean everywhere, im running 550cc lucas injectors, and running the latency values for rc 550cc 3 ohm injectors atm i can't find the values for lucas and rc manufactures these injectors so i figured i'd start there , i have scaled the injector size down to 545, 535 and then 518 and have seen little to no change in the afrs at idle, stock maf so the maf values are all stock, fuel trims are also unchanged, pressure tested the intake system to 20 psi, where would you start?
 

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I have not found the manufacturer injector latencies to be very accurate so I no longer try to find them anymore. It’s easier and much quicker to start with stock and go from there. Edit your scaling back to 550 and leave it there. Startup your car and see where your AFRs are at. Changing the scaling size has little to no effect on idle fueling so just leave it at 550cc.

See where your AFRs are at after the car warms up. Now that your car is warm go ahead and edit your peripheries. In periphery +0 you need to edit bits 1,2, and 4. These are your 02 sensors/closed loop feedback. Disable these and it will force your car into open loop meaning the ecu isn’t trying to correct to 14.7:1 AFR.

Now fire your car back up and observe your AFRs. If it’s too lean, then multiply the whole latency column by 1.2. That will effectively add 20% fuel. If it’s too rich, then multiply by 0.8. Rinse and repeat until the car is idling 14.5-15 AFR or somewhere close to there.

Now you should be able to go drive your car and cruise in third and fourth gears. Observe your AFRs. It should be close to 14.7 but if not go ahead and do the same thing as above multiplying your injector latency column.

With that done go ahead and turn back on the bits 1,2, and 4. You just dialed in your actual fuel for idle and cruising that the trims can take over now and shouldn’t be anywhere close to maxed out. Later you will log your long term low(idle) and mid(cruising) trims in order to see how much fuel you need to add or subtract.

From here you will edit your VE MAF Smoothing table and tune by way of the fuel trims ranges. Idle will cover the low trim which is 0-100Hz range. Cruising is 101-500Hz range, and WOT is the high trim 500+Hz range. Idle is still a little lean? Highlight the 0-100Hz values and hit the + key to add fuel in 1% increments. You can do the same thing for mid and high.

It’s really super simple to tune your car this way. You can roughly dial in the car and be in boost. From there on out it’s a matter of logging your long term fuel trims that cycle every 4 minutes and average out after 16 minutes. Log your AFR map, VE, 2 byte airflow, boost, and Wideband. Check your wideband output vs the AFR map number. You can add or subtract fuel from the VE table to dial it in so the wideband matches the AFR map call out. Now whatever value you see in the big fuel maps is what AFR the ecu will command. You can lean out the WOT portion of the map to get away from the stock high 9s AFR. You’re basically done after that.

It sounds like a lot of work but it basically isn’t. You’re using the MAF smoothing table like a SAFC and tuning the volumetric efficiency by load(trim) areas. Dialing in the VE so your wideband matches the AFRs in the fuel map just makes things tune so much quicker because now your VE matches the stock fuel map scaling.

Let me know if you have any questions and I would be happy to explain some more.
 

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Discussion Starter · #5 ·
Okay i turned off the three periphery functions, set the injectors at 545, set the stock latencys back to stock, and then multiplied the latencys by 0.8, its still lean, but it is better, and it runs much smoother, should i multiply the latencys by 0.8 again until i see proper afrs, or should i adjust the fuel trims?
 

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Okay i turned off the three periphery functions, set the injectors at 545, set the stock latencys back to stock, and then multiplied the latencys by 0.8, its still lean, but it is better, and it runs much smoother, should i multiply the latencys by 0.8 again until i see proper afrs, or should i adjust the fuel trims?
Multiply then again and repeat until you aren’t lean anymore. Go cruise a little bit and observe. You may be slightly leaner at cruise but if it’s lose go ahead and turn those bits back on and drive the car for a few days to see what your long term front and rear trims are for low and mid.
 

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What about increasing fuel pressure?
Unless your IDCs are really high and you are trying to stretch your injectors to run bigger, I would just stick to modifying the latencies for the initial rough in.
 

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Discussion Starter · #9 ·
wait so when i multiply latencys by 0.8 i am telling the ecu that the injector deadtime is shorter, thus making the ecu open the injectors for a shorter period of time, so if i need more fuel because its lean, wouldn't i want to make the latency values larger? just a typo? or am i missing something
 

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wait so when i multiply latencys by 0.8 i am telling the ecu that the injector deadtime is shorter, thus making the ecu open the injectors for a shorter period of time, so if i need more fuel because its lean, wouldn't i want to make the latency values larger? just a typo? or am i missing something
Yeah you’re right. Sorry I had it backwards. The total fuel commanded by the ecu is the latency time(delay time it takes the injectors to open) plus the pulse width(actual fueling time). Increasing the latency will mostly effect idle and very low loads since the injector pulsewidth is pretty small. So if you’re still lean multiple your latency values by 1.2 to add 20% more fuel.
 

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Discussion Starter · #11 ·
okay thank you, i used your method last night multiplied by .8 still lean .8 again and my wideband scared the shit out of me so i shut it off immediately and looked at my plugs and stopped tuning for the day to do more research, but thank you so much for the "guide" shit happens
 

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My on throttle afrs are great, idle is still a bit lean
Did you enable the closed loop again or are the 02s still disabled? If it’s already pretty close cruising and just a little lean at idle, I would turn your 02s back on and it should correct itself. If it doesn’t, you may have some lazy 02 sensors. Make sure the voltage while idling is cycling between 0-1V back and forth fairly rapidly. If it hangs towards one end or seems pretty slow to respond, then it’s time to replace them. The only way they couldn’t correct the slightly lean idle is if your fuel trims are pegged at +\-12.5% which means you’re pretty far off. You have the option to add fuel to the 0-100Hz area in the MAF smoothing table but I would investigate your 02s first.
 

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Discussion Starter · #15 ·
Okay i set my knock alarm for 1 and went for a drive, no knock, but my idle afrs are around 17.5, and my cruising afrs are around 15.5-16, as soon as i get on it it goes to 13.5, normal spirited driving tends toward 12.5, if i give it a footful of throttle it will drop to 11.5, sustained wot is 11.0. so on throttle is exactly how i want it, i went into my maf smoothing table and everything 500 or below i added 1% and did that 10 times for effectively 10% and it made no noticable difference
 

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Discussion Starter · #17 ·
Okay so i did more research my 13ts move 30% more air so i need to adjust scaling by 30% as a baseline and then do the standard adjust incrementally until afrs match target afrs
 

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Your 500Hz and higher areas probably need more fuel added if you want your AFR to match what is in the fuel table. Stock is high 9s. You can rewrite the fuel map and lean out the higher load higher rpm areas to 10.8-11 and then add more fuel in the VE table until it matches.

Also, just because your turbos flow more air does not mean it changes the volumetric efficiency by how much more airflow they can move. I’m on 20Ts that can put out 3-4x more air than 9bs and my VE table is adding just over 20% more fuel up top for higher boost.

When you added 10% fuel to the VE table for low and mid 500Hz and below it may not have made a difference in idle or cruising AFRs because you were still within the closed loop +\-12.5% fuel corrections the ecu can make to target 14.7:1.

I suspect you have some other issues going on with your car causing it to report a lean idle on the wideband. Most likely you have some huge exhaust leaks. Adding 10% more fuel did not change your AFR which means the ecu thinks it is hitting 14.7:1 still by way of the narrowband 02 sensors. 14.7 is not 17 of course but the ecu may actually be happy.

Take the 10% fuel back out, drive the car for a few days, and see what the low and mid trims are reporting. If they aren’t pegged at 120 if looking at the LCDBC or some similar dataloggers, or +12.5% if logging with Evoscan, then the ecu is actually targeting the correct stoich AFR and you have downstream issues with an accurate wideband reading. This is usually exhaust leaks even a leaking joint gasket can do it. It’s sucking in air and leaning out the AFR reading. Looking at the ecu fuel trims will tell you right away how accurate your wideband reading is. I’ve seen this happen a number of times where the car seems to want to idle at 16-17 AFR no matter what adjustments you make and it has always been exhaust leaks.
 
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