Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Tuning fuel on evo x

Practical Reflash Tuning

Forum Posts



Tech Articles

Discussion and questions related to the course Practical Reflash Tuning

= Resolved threads



I'm currently attempting to reflash a evo x with open source software and having a bit of problems.

The car still has the stock airbox but a with a ralliart panel filter. I have mode23 enabled on the ecu and I am logging mode 23 on evoscan and I am seeing sensible values with the exception of my fuel trims and maf values.

Firstly on the fuel trims, my short term trims seem to be accurate as they're moving around +/- 1% but then I see there long term fuel trims, long term trim idle, long term cruise and long term high. I am seeing values of -8% for long term idle and -4.5% long term cruise but it's not moving around which makes me sceptical on these values if they're correct or not. When I switch the ecu selection on evoscan to evo x can/multi I see just a short term and long term trim and they're both moving around and seem more sensible....how can I confirm which is really the real trim the ecu is applying?

Then now onto the maf, in evoscan under mode23 logging I am getting maf values in g/s but when I look at the maf calibration in ecu flash I see voltage vs "units". I am skwptical that units on the definition file translate to g/s logging on evoscan since on ecu flash the units values go quite high at the top of the calibration.....in the order of thousands.....surely this can't be translated to what I'm logging in g/s I'm evoscan.

Ive done the reflashing course but I'm finding what I've learnt incredibly hard to apply using the open source software.

This all cumulates to my real problem which is the afr map numbers in the high/low octane fuel maps being way off the measured afr values from by innovatw lm2. Ive heard everyome say the evo is an anomaly and the values never match, but my measured values were around 2 afr points leaner than what was in the map....I find this quite a lot. I set the entire wot running of the map to 10.5 afr and the actual afr measured was varying up/down in no specific trend from 11-13.5!!! I was so confused. I tried just accounting for this in the high octane table itself but then the fuel table was very choppy and all over the place, and still....the correction factors I used did not dial the afr in to what I wanted at 10.5. In the end I ended up seeing something known as lean spool enabled on the definition file and I switched this off. The afr numbers came closer to what the map values were but still. The numbers dont seem to be consistently leaner or richer ....what this means is if I end up trying to fix this on the fuel map, I would still end up with a map that is not smoothe or follow any trend.

I'm really a bit frustrated with it all....any help/pointers would be appreciated.

Can anyone offer some assistance on this?

First off about your trims.

As you know the STFT will move around quite a bit, the LTFT won't move as much depending what your STFT is.

As you mentioned your STFT is around +-1%, so then no more trim will be applied to the LTFT. So if the LTFT was sitting at 8% solid and your STFT was +-1% I would say that is correct.

A test to figure out what is real would be to highlight that area of you map or maf table and add or subtract a large number like 15%. Then watch your trims and see what they do. Watch what your trims do in Mode 23 and CAN. When using Opensource I use ECOX CAN MUTIII. Although I tend to usually use ECUEdit for logging.

For the MAF, You should be able to log MAF voltage and use this to translate to the MAF Table. You may need to change you mode and if you're unsure which to trust then put a scope on the MAF wire and check the voltage to the logger.

To be honest I wouldn't stress to much about the values in the AFR map being off. As nice as it would be to have them match perfectly 90% of the time they won't. Even when downloaded as a stock map the values are around 9.4-9.1 which the engine does not run. Usually in stock form they are around 10.5-10.9 so already off by 1.5afr.

You can fix it by altering the MAF table but be prepared to spend many hours.

Hi Chris,

You touched on something called ecuedit. Can this be used on open source as well? If so, is it a better alternative to ecu flash/evoscan combo? Currently the definition file for this car on on ecu flash is not very well defined. Would moving to the ecuedit platform see me probably get a different definition file that may be better defined? Also, maybe the issues I'm seeing with evoscan would no longer be an issue with ecuedit?


I use both evo scan and ecuedit/epifan depending on what car I am tuning. Generally I favor ecuedit.

The best I have used is ECUtek but it comes at cost.

The ECTEdit can be found here http://www.epifansoft.com/

It is possible the ECUedit has better defined definitions, I have had great success with their definitions or when I have an issue I flick them an email and they fix it. Just recently I had an issue with a missing wastegate map on a BL5 Legacy, emailed the map and he emailed me back a new definition within 24hours.

The bonus as well is that both opensource and ecuedit are .BIN files (providing you saved your opensource as a .BIN and not .SRF) so you can open the opensource files in ecuedit and no need to start from scratch.


I got in contact with epifan and I will be purchasing the pro version of his software. He said he could provide proper defs for my rom so I will see how that goes.

What is confusing me chris is why the long term trims are so far out on this car, if these values are indeed correct. The car has an upgraded turbo gtx3071R and forged pistons but the intake system is still stock with the exception of a panel filter. I find -8 and -5 for long term idle and cruise trims quite far off. I did make a change to the MAF scaling as you suggested, but I did not see any difference in the values once flashed and I started the car back.....maybe it takes a while to update? But then should the short term trims not change while the long terms re-adjust?

It isn't uncommon to see some cars with values in the LTFT 5-10%. This can be caused by many things, one of the most common is as simple as a dirty air flow meter or slight air leak post MAF.

Making a change to your maf table where there is a high ltft % should change you ltft although it does take awhile.

If you had 8% ltft and 0% stft then made a +8% change to your maf table in that area then when you start the engine back up (and get the heat soak out of the engine etc) you should see a ltft of 8% and stft of -8%. Then slowly (can sometimes be anywhere from 5-10min or even more) you will see your ltft come down towards 0 and stft come up towards 0

Hi Chris,

What you've said makes complete sense. I'll have another go when epifan sends me the new definition and see how it goes.

I know this is old but if anyone in the future reads this... if you upgrade the intake, exhaust and or turbo you may have to scale the MAF but also have to adjust the "Calibration fuel map" because these cars run on both MAF and MAP for load values. I was chasing my tail redoing the MAF over and over wondering why I couldnt get the target AFR anywhere near the actual AFR.... adjusted the VE table ( calibration fuel map) with the correction factor we learned here and BANG .. was now within 0.5 AFR... before i did this is was off over 2 full points with an upgraded turbo, intake MAF housing and full exhaust. Now once you get it in the ballpark you just adjust the target AFR table to make your actual where you want it... no, it wont match up completely but it will be much closer... I didnt like putting in 8 and 9 AFR to achieve 11.5 and now its only a few points off.

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?