Guys - Just real quickly - Do you all think that 10g/rev should be the upper limit for the axis?

I am trying to determine appropriate scalings but I need an upper bound (for stuff to fit into words and longs)

ps according to my calculations (someone please check ) a 3000cc engine running at 50psi (ie approx 36psi real) with -20 celsius temps will only use 7.117 grams of air a second at 100% VE...

 

This is probably the most technical thread i have ever read on here.

 

yeah it was a toss up between here and aktivematrix - but here has a lot more tuner knowledge which i think has proven beneficial.

 

I remember reading Bez's disassembly and notes and he foud that this is already in our ROMs. The item in ECUFlash labled 'Maf Size', is really 1/engine size. So, I'm not sure if that helps you or not, but I figured I would mention it.

10g/rev is plenty for an upper limit. We will never ever even approach that.

And, yes, I get 7.12g/rev in your hypothetical example. Also, I did a quick calc for a 2.0L engine running 60 psi of boost (74.7 psi absolute) at 100% VE and -20C and came up with about 7.07g/rev. So, again, I think the 10g/rev upper limit should be fine. 95% of us will probably never surpass 4g/rev.


Eric

 

Will 10g/rev limit the resolution of any of the maps or anything?

What is the uncompensated load? Is it the actual airflow/rev going into the engine under the given baro and temperature in the MAF sensor? Or is it a load value that is based only on the MAF frequency and ignores the baro and temp measurements?

I have got to admit, I'm an ECUFlash newb and just recently started messing with it. I tuned a car last week using AccessPort and noticed something interesting. Maybe this is already well known, but the AccessPort logging software had a "fuel Load" and a "Timing Load" that you could view. Is this due to the ignition and fuel maps being based on different load parameters? While tuning, I used the "Fuel Load" for fuel tuning and "Ignition Load" for ignition tuning and the values in the map matched well with the ignition and fuel tuning. The loads were considerably different too.


Hopefully we can get the right balance of software knowledge and tuning knowledge to make it all work out well.

 

I dont think the 10g/rev is the max he will put on the axis, its just an upper bound needed for code. Im hoping that the actual axis "load" will be scaleable as it is now.


I could be completely wrong though

 

That's been known for a while. Ignition uses either uncompensated load or baro compensated load. Fuel uses either uncompensated load or baro and air temp compensated load. It depends on a few factors. Here is an early thread on the topic:

https://www.evolutionm.net/forums/sh...d.php?t=288214

 

Another real quick one?

Highest PSI anyone is going to run?

I know we mostly get 3 or 4 bar sensors, so will a max of 5 bar be enough?

 

Considering that's 72 psi, I should hope so. You're thinking the AEM 5-bar sensor, or something else? (That 5-bar sensor is pretty popular with DSMLink and AEM guys.)

 

Max of 5 bar will be sufficient to start out with. When people start to push the envelope then keep in mind that this may want to be adjusted. Evo's love boost, the 3 bar limit on the JDM map is almost criminal. The 4 bar starts to make sense until you start using race gas. The 5 bar should be ok for 90% of people. My feeling is that MAP resolution isn't nearly as important as people think it is. You don't really fine tune in 0.1gram/rev increments at WOT. Hell for me half the time it is 0.5 gram/rev resolution. My friends car was pulling 4.00 grams/rev last weekend and when I pulled the maps I couldn't understand why timing was basically locked vs rpm for the whole pass. He hit a wall at 2.08 grams/rev because I didn't burn him a ROM for extended maps. The car was running so good that I didn't want to change it and mess him up.

10grams/rev is about 900whp worth of power. Ideally I love the stock ecu and would like to keep it in the car forever. However do you have a safety if somebody were to hit the 10grams/rev limit? Like will the car still interpolate off the last set of data in the map such that it will hold 10 deg at 7000rpm and 10 gram/rev or will the code go bonkers? Also will it hold the same afr (or VE setting a MAP based car) or will it go lean? Think about what you want to do. Is a fuel cut safe at this level? I don't think it is. Personally I would just dump the injectors to 100% duty cycle, lock timing down to 5 deg, and throw the CEL. That may not be feasible either but its just a thought.

 

I want a number big enough that NOONE will ever hit it, but small enough that we don't waste resolution...

I don't think we will ever see 10g/rev OR 72psi...

 

I agree that most people won't hit these limits, at least within the next 5 or so years.

Remember that not but 5 years ago 20psi on a 4g63 was dedicated to race cars. 25 psi was serious amounts of boost for built motors, race gas, and trailored track queens. Here we are not but 5 years later and we have street cars making 150 more WHP, running 30+ psi on pump gas, and driving 200 miles to the track. All its going to take is a couple morons on street E85, 40R's, and 5+ years of development to throw what is impossible to what I hope is someday possible out the window.

 

ok well it shouldn't be too hard to rescale it...

onto the topic of resolution for the g/rev axis.

what is too much? 0.01? ie 2.50 vs 2.51 - is that even a decernable difference? I mean if you have a AFR of 10:1 (for simplicity) then 0.01 of a gram of air requires 0.001 gram of fuel, I don't even think/know if an injector can spray that quickly.

Anyone want todo some quick maths?

 

Our stock maps have about .1g/rev resolution down low and about .2g/rev higher up. So, that gives you an idea of what we are dealing with right now. I edited my fuel maps a while back to show g/rev along the top instead of load. If you want, I can post up a picture of what it looks like for a stock map.

Actually, forget what I just wrote. That is the change in value from column to column. You are referring to the number of decimal places per column. I think going to two decimals places is plenty. Even 1 should be enough. I can run some math for you tomorrow if you want. It's late here. ; )

Edit: Just some real quick math to get you thinking. Maybe we can look at the injector pw math some more tomorrow to see how fast or how much change an injector can handle (mrfred may have some input on that with all of his testing).

At idle, we will be at around .3g/rev of airflow. So, if your resolution is 0.x g/rev, then the next column is going to be a 33% change. If you use 0.xx, then the next column can be as little as a 3% change. The stock maps seems to use about a 0.x resolution, so it seems to work fine, but it's food for thought. Obviously, the higher you go in the scale, the resolution becomes less of a factor.


Eric

 

Alright Gents (and Ladies if there are any reading)

How about something like:



Note the 25 point 'load' axis, don't take too much notice of the AFR map, its just a stock one copied and then extended to hit 25 columns.

Using my current formula/scaling (x/4096) we can specify down to 0.0002 (1/4096) accuracy. lol

That scaling wasn't so much chosen for the accuracy of the 'load' axis but rather my divider for the variable where the g/rev is stored in the ECU.

Remember the ECU only thinks in integers, 1,2,3 etc

Obviously 1g/rev vs 2 g/rev is a MASSIVE change, so I make the number artificially bigger (in ECU land) then divide it once we can think in floating point.

So 3.5 g/rev in the ECU is actually 14336 (3.5 *4096), thus to get 14336 back into a "human readable/understandable/real" number we divide it by 4096... back to 3.5 g/rev

Anyways - I have basically done the code that calculates the g/rev - I just need to integrate the VE stuff and then its almost ready to be tested.