ECUTalk Fuel Consumption Wrong?

Any idea what would cause ECUTalk to give an excessively high fuel consumption reading? I have entered the correct injector size (550cc) & cylinders (6). ECUtalk has my fuel consumption average at 20-21L per 100km!!! The lowest I could get it was 16.5-17L per 100km after a retune. However I can drive 430km on 56L, which should put me around 13L per 100km (not too bad for a 401rwhp 23 year old car). Why is ECUTalk off by so much? I have reset it but still has the same figure. If I was actually getting the fuel consumption that ECUTalk indicates then I would only be getting 329km out of the same 56L. So what gives?

 

Peter is away on holidays at the moment, otherwise I would ask him / direct him to this post.

 

MIne did that once...

I have ECUtalk on my hand held HP iPaq. I too had the same problem as you do. For me, the problem was occuring because I didnt have the "Speed" sensor active. For accurate fuel data you need speed, injector duty cycle, injector timing and I also think RPM.... actually, not sure about the RPM. But having all the correct sensors active, fixed my problem

 

In that case my ECUtalk unit might be faulty. As the "main" screen shows accurate speed, injector duty cycle, rpm & the fuel screens show distance traveled. So all the sensors def work. However the "Timetest" doesnt work, it gives my top speed but no time or distance. Also the "MaxVals" doesnt show true max values - I just did a 0-100km run and hit redline in 2nd, but it is telling me that my max was 92kph & 3950rpm? Yet the unit itself read 106kph when I did the run. Very strange. Hopefully can get an answer from Peter when he gets back. The fact that the car has had an auto to manual conversion w/na rear end & nistune shouldnt affect the readings should it?

 

I suggest you send Peter an email so he can get back to you as soon as possible.

 

Beat me to it.
What HE^ said.
E

 

Attempted to make 5l/100 300zx joke.
Couldn't work out how to upload pic of Z being pushed.
Admits lameness and moves on.

Serious note though, how accurate is the speed reading? Mine is out by about 2% and that is reflected in the mileage. Might not seem like much, and I really don't see it being enough to be as much of a difference as you are getting, but combined with some other settings being wrong it may be a contributing factor.

 

I dont have ECU talk but I do have consult adaptas and a lappy (its my understanding that ECU talk is reading the data from the ecm as well) and my lappy displays the same spead as my GPS - all 3 that is, my phone a tom tom and a navman - so assuming tyre sizing and diff ratios are stock I would imagine ecu talk to give a pretty accurate reading

 

Injector size & cylinder numbers are correct, have double checked

 

hi guys. calculation of the fuel portion (forgetting economy which also uses speed to determine distance) only relies on injector pulse width (duration injectors are open for per revolution) and rpm, along with user input injector CC size, and number of cylinders.

if your fuel used readings dont coincide with your actual fuel used (e.g. you fill up fuel tank full, reset trip stats with ecutalk, and then have ecutalk on for all trips till you next fill up, then fill up full, and compare fuel filled up with ecutalk fuel used for all trips), then the reasons are one of these:

1. injector flow rate isnt actually what you think it is (e.g. theyre sold as 550cc at 50psi, but std fuel pump is 40psi or whatever... so cc rate may be lower at lower fuel pressure).
2. fuel pressure isnt the standard fuel pressure (i.e. fuel pressure that results in the given injector CC/min flow rate)
3. RPM reading is incorrect (should be easy to check roughly versus tacho?)
4. ECU is reporting wrong injector pulse width (unlikely).

but, ultimately, unless there is something mechanically wrong that you need to fix, you just need to calibrate the CC to what gets you the correct reading (i.e. a reading which matches what you fill up with). even for a normal vehicle with stock injector size, worn injectors or small variations in fuel pressure can mean i need to run ecutalk with injector size of 355cc for my 370cc, or whatever.

so, pretty much just do the full tank run with ecutalk, and then do the maths and adjust the CC size by the portion the results are out by. e.g. if its set to 550cc, and ecutalk is reading 80L when you fill up with 56L, then just multiply 550*56/80 = 385cc and set that as your cc rate.

now, when you're comparing fuel economy readings, this makes it slight harder as now we're having to take into account whether your speed readings are correct (that's the only thing which would make fuel economy readings wrong when fuel used readings are correct). for that just get GPS out and compare ecutalk speed to GPS speed. if its not correct, adjust speedo % correction in the options. should be pretty accurate on a standard car (mines spot on in GTIR).

Peter

 

Thanks for that Peter, I will give it a try. Speed & rpm are perfectly matching with actual figures so we know that part is good. How do I go about getting the time trial function to work? Eg 0-100? It starts & registers me getting to 100km/hr, over distance but always shows 99.9 as my time at the end of the run? Not sure if I need to change anything? Reset of unit didnt seem to help.

Cheers

 

can you get a video showing this? time trials should auto-start, after you have clicked on 'start', once your speed goes from 0->2km/h, and stop once you hit the target speed/distance.

also, i should mention, if you think there could be something wrong with the display, occasionally the firmware can become corrupt - often this would be after some unusual electrical spike, e.g. jump start or battery disconnect while engine is running. a normal firmware update (v2.05 on top of v2.05) should restore it back to normal.