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Trying To Understand Hondata S300

Practical Reflash Tuning

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Discussion and questions related to the course Practical Reflash Tuning

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So I do NOT have the Hondata S300 yet. However, I have the software on my computer and am attempting to get familiar with the tables and everything. I will be getting this ecu soon to start learning how to tune on my own vehicle.

So for fun I pull up the d16y7, 550cc injectors, turbocharged map. When I look at everything it's so vastly different than what I was expecting, only having "tuning" experience on the PC Link in the live remote engine dyno tuning. So it raised a few questions.

What parameters are they using for fuel tables? As in I'm used to seeing the low numbers such as 45.3, 51.5 etc, they using numbers from 64 all the way to 2348. When using lambda does it not really matter what the numbers are in the table and so say if you need to take 10% of fuel out because it's 10% richer than your target would I just take the 10% off whatever number it happens to be in the cell I need to take it off from? Or does it depend on what the number in the table is to determine how the fuel will be added or taken out?

How can I identify which numbers they are using? Say percentage of injector time IE 50% 100% of a set value etc, the pulse width, how can I easily identify and know what numbers are being used as is what I mean basically?

Last two questions are, they have a low speed and high speed fuel table, same thing with ignition table, would the low and high speeds be used for engines with vtec, non vtec or are they for turboed applications? Last but not least, I could switch over to the target AFR table, then I converted it to lambda. Now the target fuel table itself I can not change like I can in the PCLink. I found that I can only change it through the settings menu which is a very broad from this load to this load it should be 1.0. then from this load to this load is should be 0.90. Then full acceleration it should be 0.85 and those are the only three options they give so is this the only way to adjust the targets is through these three options and the ecu interpolates it from there for the target table?

Thank you for any help. I'm new to tuning and everything in the performance world, so just am trying to gain as much knowledge before I can feel comfortable to get real life experience tuning something I never have before. It is much appreciated!


Hi Damen,

Welcome to the wonderful world of reverse engineered stock ECU's. On a standalone, the people who wrote the tuning software know how the fuel calculations work, even though they may not give you all the details. When reprogramming a stock (or in your case modified stock) ECU, the control system is reverse engineered. Somebody looked at the assembly code and did some testing to make educated guesses about where the tables are in the ECU and what they do.

That means you will see a lot of assumptions made and a lot of "well, we don't know what that table actually means, but we know what to change to make it do what we want." For your purposes the values in the fuel tables are directly related to injector pulsewidth. Higher number--> more fuel.

Do you have a wideband set up to your S300?

The low and high cam tables are for classic VTEC systems engines with just a low and a high lift mode for the cam(s). Later stuff like K series is more complicated. So when the VTEC switches into the high lift mode, it jumps into the new set of spark and fuel tables.

Ahh ok. I don’t have anything at the moment I’m just playing with the software and one of the maps that come already on it to see if I can get to understanding what I’m looking at which for the most part I do. It’s just the injector pulse width it’s using is vastly different from the pclink I used in the live remote tuning dyno lessons. Say on the pclink it would read 40s on up. Haven’t seen 100s yet so far for the fuel tables.

However when I open the s300 software it’s showing 64 up to 2,500 so I didn’t know it that changes anything or if I tune it the same. IE: say the cell I’m in the middle of is 1539. Lambda measured is 1.0 and target is 0.85. I would still just put 1.15 in the percentage calculator and that would add the 15% more fuel that I need correct?

Just making sure that the past 6 months of studying the lessons is sinking into my mind lol.

Thanks for the help.


Also for non-vtec applications, I would just ignore the Highspeed ignition and fuel tables as well correct?


First of all, what you see in your fuel map are units fuel, reason why you have that higher numbers,

when you add or take 10% of fuel you are doing that, so if you measure in labda or AFR and you need to add 10% to match your target, you left click on your mouse/track pad, select adjust and type 10 under percentage and you will add 10% so you will match your desire AFR.

Your low/high cam is for Vtec engines only D series Sohc Engines have low cam only map, although you will see low and high, when you actually datalog you will notice that all trace cells will stay in the same low table, on vtec engines as you past your vtec engane point it will switch to the high cam map,

Regarding your question about target Table, Yes you have only 3 parameters, although these we don't use, and never pay any mind, you should know which AFR or Lambda numbers you are tuning to, so when tuning you make corrections to get to your AFR target, then is you dice to interpolate it will do based on your selected load cells, not based on AFR target table, same applies when ecu is interpolating.

Now what you see in PClink under fuel map is your actual VE therefore you will never see higher numbers than say 110 for example, as is based in 0-100 percent Volumetric efficiency, where Hondata uses fuel units

When you want to tune for fuel, taking your example, you have 1.0 lambda and your target is .85 you need to remove 15% of fuel, and that is exactly what you do, do not pay attention to the number if that confuses you, the tuning principle is the same, just add or take whatever the percentage you need to achieve your desire AFR target. no matter what number you ended up with again those are fuel units, you add or take as much as you need to get to your AFR target if you end up with a number such as 2000 per say, that means you need 2000 fuel units to get to your AFR this is based on your injector size,

For none Vtec engine, the trace cells will always stay on the low cam table. so there is no need to ignore high cam as you will never use it, as you have no vtec to utilize the high cam table.

I would suggest to navigate through parameters tab or the help file on Hondata and you will pretty much get your answers there, if not, then feel free to ask any questions.

Hope that helps

Hey Javcolin, thank you for that! I appreciate it very much!

Man I’ve really been put in my place now. I thought that by doing the courses I could understand how to tune. However I’m aware now that we’re being taught all the easy things first and there’s still so much more to learn that isn’t taught in the lessons.

Im just wondering when I’ll actually be ready to tune my first car.

Anyways thank you so much for the help. I was making adjustments the same way I would the VE table. Thank god I wasn’t tuning a real hondata s300 because I wouldn’t have been adding enough fuel!

Hi Slowcivic,

Actually all the courses theory is applicable to all platforms, although there are some worked out examples for different ECU's that may help you better the theory still the same, same thing applies to Hondata, you would be adding or taking x fuel % just the fuel numbers will be different.

So don't be afraid to start tuning, but you did good, when in doubt better look for answers so you are clear on what you are doing before hand

Right well I mean there’s differences. You’re saying for the hondata table you type 5 for 5%. Where on the VE table I’m used to putting 1.05 for 5%. Or is this still applicable?

Have you checked out the recent worked example we added on the Hondata KPro? There are obviously some big differences given the K20's continuously variable cam control, but the basis of the s300 and KPro are very similar. Don't worry, while the smanager software looks different to a Link G4+, the majority of what you've learned so far will be 100% applicable :)

Sweet, thank you Andre! My boss just gets me nervous because if there’s an issue such as a boost leak, vacuum leak, I may not notice it since I’m still new to everything.

thank you again. I will most definitely be checking out the kpro lesson

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