2018 Tundra Hitting limiter on WOT 1-2 shift randomly?

Hey guys, i am SUPER new to tuning. I run a side business in automotive repair, but tuning is still slightly over my head lol. im excited to learn as much as i can. Now onto my issue.

long story short: i downloaded HP tuners, and bought a tune from a guy for my tundra. flashed it in the truck and the truck ran like a raped ape! however shortly after, the truck began to start hitting what i assume to be the limiter when trying to shift into 2nd gear on WOT, as well as 3-4 shifts WOT. it will do it from a stand still, or if cruising at 40 and floor it. now the weird part is, if i turn of all the nannies completely it very rarely will do it!?!?! also to note; the rpms the truck shifts at is different in certain gears.

it seems like the scheduled shift point was not calculated to accommodate for the actual rpm delay in shifting prior to hitting the limiter. i contacted the tuner and he just recommends a reflash. which im about to do, but i wanted to drop the tune on here to see if anyone with more experience than me can take a look at it. again im super new to tuning, so i kinda know what im looking at but then it quickly goes over my head lol.:banghead:

P.S. im going to try and record a video of it to add on here as well. Thanks in advance, and i hope to learn alot from this community!

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Originally Posted by GearOne2019

Hey guys, i am SUPER new to tuning. I run a side business in automotive repair, but tuning is still slightly over my head lol. im excited to learn as much as i can. Now onto my issue.

long story short: i downloaded HP tuners, and bought a tune from a guy for my tundra. flashed it in the truck and the truck ran like a raped ape! however shortly after, the truck began to start hitting what i assume to be the limiter when trying to shift into 2nd gear on WOT, as well as 3-4 shifts WOT. it will do it from a stand still, or if cruising at 40 and floor it. now the weird part is, if i turn of all the nannies completely it very rarely will do it!?!?! also to note; the rpms the truck shifts at is different in certain gears.

it seems like the scheduled shift point was not calculated to accommodate for the actual rpm delay in shifting prior to hitting the limiter. i contacted the tuner and he just recommends a reflash. which im about to do, but i wanted to drop the tune on here to see if anyone with more experience than me can take a look at it. again im super new to tuning, so i kinda know what im looking at but then it quickly goes over my head lol.:banghead:

P.S. im going to try and record a video of it to add on here as well. Thanks in advance, and i hope to learn alot from this community!

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Reflashing the same tune isn't the solution for this problem.

Shift Scheduling ("Transmission -> Shift Scheduling -> Normal") in your attached tune is set too high at WOT (100% Accelerator Pedal Position) - over 6500 RPM, which is the rev limit setting ("Engine -> Fuel -> Cutoff, DFCO -> RPM Limits"). The Shift Scheduling tables are in Output Shaft RPM, there's a tool to convert from Output to Input RPM in this post: https://forum.hptuners.com/showthrea...l=1#post598929

There should be some buffer between the Scheduled RPM and the rev limiter, typically 200-300 RPM is enough on the stock converter. Shifting at 6500 is a bit on the high side, 6200-6300 is generally the sweet spot, and on a 1-2, 6000 is often a tick quicker.

Some other observations on your attached tune:

1) The MAF curve ("Engine -> Airflow -> General -> MAF Calibration -> Airflow vs. Voltage) wanders off at 4.38V and beyond - it should be a smooth curve
2) The changes to the spark tables ("Engine -> Spark -> Advance -> Base") weren't given much attention - 4 degrees added to the entire Base Spark, 6 degrees added to the entire High Octane, in some cases this would be beyond MBT if it were achieved
3) Knock Retard is not enabled above 6200 RPM ("Engine -> Spark -> Retard -> Knock Retard -> Max RPM") - Knock Retard should be enabled up to our highest shift point at a minimum
4) The PE curve ("Engine -> Fuel -> Power Enrich -> Power Enrichment -> EQ Ratio (Gas)") is flatlined at 1.119. A flatlined curve is okay without a dyno or track to sharpen it, but an EQ Ratio of 1.119 corresponds to an AFR of ~13.0 - might make a bit more power, but maybe not the best setting for a full-size truck, especially if it does any hauling/towing. The stock PE curve actually has a reasonable trend (richer @ peak torque, leaner @ peak hp), and can be leaned out a bit to make more power while still being conservative; scaling the stock curve for a target AFR around 12.4 (EQ Ratio of ~1.178) at the leanest is a setting that will make a bit more power than stock, while still being on the conservative side.
5) Non-WOT Shift Scheduling is just increased 10% across the board; you may find that you prefer stock or lower, rather than higher, shift points at low throttle positions (30% and less) - the stock cal is already a bit high in some areas, IMO

Since you're new to the tuning world, PE and EQ ratio may be new terms, so some quick definitions:

PE is simply enrichment for WOT conditions (in this case, WOT for PE is defined under "Engine -> Fuel -> Power Enrich -> Throttle -> Enable Throttle")
EQ ratio is the ratio of Stoich AFR to Target AFR (EQ = Stoich/Target and Target = Stoich/EQ). For example: an EQ Ratio of 1.2 and Stoich AFR of 14.6 gives a Target AFR of 14.6/1.2 = 12.167.

The attached file corrects the WOT Shift Scheduling (6000 RPM 1-2 shift, 6200 RPM for all others), corrects the MAF curve, enables Knock Retard up to the rev limit, and has a more conservative PE curve (if this truck is used for towing/hauling frequently, especially in a hilly or mountainous area, a little more enrichment may be a good idea) - the remaining Shift Scheduling and the spark tables are left at your discretion. Attachment 98807

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Originally Posted by SlowNStock

Reflashing the same tune isn't the solution for this problem.

Shift Scheduling ("Transmission -> Shift Scheduling -> Normal") in your attached tune is set too high at WOT (100% Accelerator Pedal Position) - over 6500 RPM, which is the rev limit setting ("Engine -> Fuel -> Cutoff, DFCO -> RPM Limits"). The Shift Scheduling tables are in Output Shaft RPM, there's a tool to convert from Output to Input RPM in this post: https://forum.hptuners.com/showthrea...l=1#post598929

There should be some buffer between the Scheduled RPM and the rev limiter, typically 200-300 RPM is enough on the stock converter. Shifting at 6500 is a bit on the high side, 6200-6300 is generally the sweet spot, and on a 1-2, 6000 is often a tick quicker.

Some other observations on your attached tune:

1) The MAF curve ("Engine -> Airflow -> General -> MAF Calibration -> Airflow vs. Voltage) wanders off at 4.38V and beyond - it should be a smooth curve
2) The changes to the spark tables ("Engine -> Spark -> Advance -> Base") weren't given much attention - 4 degrees added to the entire Base Spark, 6 degrees added to the entire High Octane, in some cases this would be beyond MBT if it were achieved
3) Knock Retard is not enabled above 6200 RPM ("Engine -> Spark -> Retard -> Knock Retard -> Max RPM") - Knock Retard should be enabled up to our highest shift point at a minimum
4) The PE curve ("Engine -> Fuel -> Power Enrich -> Power Enrichment -> EQ Ratio (Gas)") is flatlined at 1.119. A flatlined curve is okay without a dyno or track to sharpen it, but an EQ Ratio of 1.119 corresponds to an AFR of ~13.0 - might make a bit more power, but maybe not the best setting for a full-size truck, especially if it does any hauling/towing. The stock PE curve actually has a reasonable trend (richer @ peak torque, leaner @ peak hp), and can be leaned out a bit to make more power while still being conservative; scaling the stock curve for a target AFR around 12.4 (EQ Ratio of ~1.178) at the leanest is a setting that will make a bit more power than stock, while still being on the conservative side.
5) Non-WOT Shift Scheduling is just increased 10% across the board; you may find that you prefer stock or lower, rather than higher, shift points at low throttle positions (30% and less) - the stock cal is already a bit high in some areas, IMO

Since you're new to the tuning world, PE and EQ ratio may be new terms, so some quick definitions:

PE is simply enrichment for WOT conditions (in this case, WOT for PE is defined under "Engine -> Fuel -> Power Enrich -> Throttle -> Enable Throttle")
EQ ratio is the ratio of Stoich AFR to Target AFR (EQ = Stoich/Target and Target = Stoich/EQ). For example: an EQ Ratio of 1.2 and Stoich AFR of 14.6 gives a Target AFR of 14.6/1.2 = 12.167.

The attached file corrects the WOT Shift Scheduling (6000 RPM 1-2 shift, 6200 RPM for all others), corrects the MAF curve, enables Knock Retard up to the rev limit, and has a more conservative PE curve (if this truck is used for towing/hauling frequently, especially in a hilly or mountainous area, a little more enrichment may be a good idea) - the remaining Shift Scheduling and the spark tables are left at your discretion. Attachment 98807

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apologies for the delay in response. First off thank you very much for the information, its super helpful. some of the terms are familiar to me some arnt so ill definable be doing a lot of research. im planning on flashing the tune in the truck tomorrow and logging to see how it handles it. im in middle ga so no mountains or anything here. as far as the spark tables what is MBT? what would you recommend be done to the spark tables? im running only 93 Octane in it.

Quote:

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Originally Posted by GearOne2019

apologies for the delay in response. First off thank you very much for the information, its super helpful. some of the terms are familiar to me some arnt so ill definable be doing a lot of research. im planning on flashing the tune in the truck tomorrow and logging to see how it handles it. im in middle ga so no mountains or anything here. as far as the spark tables what is MBT? what would you recommend be done to the spark tables? im running only 93 Octane in it.

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Sorry, haven't been on much with personal projects

MBT is Maximum Brake Torque timing (and sometimes backronymed to Minimum Best Timing) - it's the timing for a given RPM and Load where the engine produces the most torque (and, thus, power).

Many engines on lower octane fuel will have knock retard before they can reach MBT timing - the flipside is that, with high octane, it's possible to have timing more advanced than than MBT without knock, which reduces power and makes the engine more knock prone.

The ideal is to use a dyno or strip to determine where the engine is gaining or losing power as timing is added/removed. The old approach of "advance until it knocks, then pull a few degrees" was trying to fudge MBT timing, but it's not an accurate or reliable approach. Fortunately, Tundras have an MBT table available under "Engine -> Spark -> Advance -> MBT -> MBT Spark".

Comparing the stock timing tables to the MBT tables, note that the area to focus on is the 2800-4400 RPM range from 80% load and up. Try adding a few degrees at a time in that range, smooth it to the adjacent areas, and log Knock Correct Learn Value (KCLV) and Knock Feedback (KF) to make sure you're not having timing pulled as a result.