4b11slayer

Whats up yall so im attempting to tune my evo 8 on speed density.
Have a few questions about MAP VE.

If my max boost level is 30 psi should my last KPA column be 221 kpa?

Why do i always see 350 kpa on the last column on most speed density roms?

I dont get how the ecu provides the correct fuel for a given BARO/KPA region if the MAP VE doesnt cover all KPA regions just steps.

Lets say i go lean at 200 kpa but there is no 200 kpa on MAP ve table. How do i richen it up?

Biggiesacks

kpa starts at absolute zero not atmospheric pressure. So if your hitting 30 psi of boost you have to add what ever your atmospheric pressure is to that number. so at sea level you would add 14.5 to 30 to get 44.5 psi = 306kpa

4b11slayer

Im sorry i did the equation in my head.
So does the last column in my MAP VE need to be my max boost?

And if i go lean at 200 kpa how do i correct with more fuel if i dont have a 200 kpa coulmn?

Do i use rpm ve?

4b11slayer

So if you have the following.

21kpa
41kpa
61kpa
140kpa
200kpa
350kpa

On your MAP VE table. How does the ecu adjust fuel for KPA such as 180? Or 300kpa for example

Biggiesacks

i can only attempt an answer based on my generic understanding but I haven't tuned SD myself so i can't get too specific.

You can rescale your tables if you want, but if anything else is sharing that table scaling it will also be rescaled and need to be adjusted. I don't know if anything else is sharing that table scaling.

I would expect you would want the final column to exceed your max expected value by some margin. The way I understand it though, if you do exceed the max scaled value the ecu just sticks with the last data point in the table.


If you don't have a specific scaled point in your table you adjust the cells around that point to effect how the ecu interpolates the final value. The alternative is rescaling the table like you where talking about to give you more resolution in the area you are trying to target.

200kpa is like 15ish psi of boost i think? So are you going lean during spool up or are you tuning wastegate pressure or something like that?

Biggiesacks

it interpolates the value. So to effect 180 you would adjust 140 and 200. 200 is closer to 180 so it will have a larger effect then 140 would, but they need to both be adjusted.

4b11slayer

I see.

So im on 30 psi. Not doing full pulls but partial pulls from 2k rpm in 3rd gear. Starts to go lean around like 250 kpa i think. I gotta look at logs but i remember 250 or so load. I just dont understand how ecu controls a KPA that isnt on the MAP VE 2d table. I mean theres only like 5 or 6 columns.

I previously tuned the car on speed density myself. I am just trying to retune since i had bad lean issue from a stop and also really rich tip in. Ive got that all sorted now. My idle and cruise is great so is 0-18 psi of boost but after it will go lean. So now im trying to get some answers ive always had.

Biggiesacks

the fuel map?

4b11slayer

Well yea. I can dial in my afr via fuel map. But then what is map ve for?

Biggiesacks

pushing the outer limits of my knowledge here, but i think its a calibration. So yah it will effect fueling but its a blunt instrument which is why the resolution is so poor, it will effect large areas of the fuel map at once where as the fuel map itself allows for finer adjustment. I could be way off on this though.

4b11slayer

I see. In for some more insight

4b11slayer

Thanks biggiesacks

Biggiesacks

yw, hopefully someone with more knowledge will chime in.

WytWun

In terms of how the map is used to translate from the MAP input to the VE, have you used the "View Graph" menu option present on each 2D or 3D map window? This shows the relationship, including the interpolation between axis values, graphically.

4b11slayer

Thanks for oppening my eyes. I got car dialed in prettt good now. No lean issues from a stop and also no rich issues at part throttle. I fixed all this via MAP ve and also fine tuned wot via the fuel map. Im seeing around 360 load at 29 psi. I know i can fine tune it more so load and boost correlate better. I.e 30 psi 300 load.

The 96531706 has BIG MAPS. I wonder if i should switch to a rom with a smaller map so i can use the entire map.