MSefi.com read only forum (Jan.15,2018)

Hi,

I haven´t bothered about ReqFuel so far, but now I get to a point where I do some fine-tuning to the VE bins. Unfortunately I have a relatively high ReqFuel figure of 18. Had been no problem so far, but now I suffer from the low resolution of the VE values that I get as a consequence of the high ReqFuel. Sometimes increasing a cruising area bin by "1" changes AFR from 15.5 to >16.0 which I think is a lot.

a) If I reduce the ReqFuel to, say, 16. By how much would I have to increase all the VE bins ? (I´d expect that ALL values would need increased by the same addend. Right ?)

b) If I did a), would there be any side effect to other tables to be expected (like ASE etc.) ?

Looking at the fueling equation we see that Req_Fuel and VE are multiplied together:

PW = REQ_FUEL * VE * MAP * E + accel + Injector_open_time

So if you reduce Req_Fuel by come factor you can simply multiply the VE table by that same factor. 18/16 = 1.125
Multiply the entire VE table by 1.125 and you're done. I think there is even an option in Megatune to scale the whole table by a factor.

C|

hi and:

landybehr wrote:Sometimes increasing a cruising area bin by "1" changes AFR from 15.5 to >16.0 which I think is a lot.

Changing the Req_fuel will not change this from happening. The only thing that the Req_fuel will change is the range that your values are in. If you are between 10 and 240 on all values, you are as close as you can get using the VE table.

landybehr wrote:a) If I reduce the ReqFuel to, say, 16. By how much would I have to increase all the VE bins ? (I´d expect that ALL values would need increased by the same addend. Right ?)

Uh, no.

landybehr wrote:b) If I did a), would there be any side effect to other tables to be expected (like ASE etc.) ?

No, they are all relevant since req_fuel is part of the fueling equation.

cygnus x-1 wrote:I think there is even an option in Megatune to scale the whole table by a factor.

Yes, there is this option in MT. It is in the VE table pulldowns.
IMHO, Jacking around the req_fuel values to improve your AFR will be an exercise in futility in this instance.

Hi,

just looked for .. and found the option in MT. Unter tools there´s a way to re-set the ReqFuel and with just typing in a new value and clicking ok all is done.

Now that I´ve changed ReqFuel from 18 to 15 -> I´ve same time increased a VE that was formerly 40 to now 48. For today I did nothing else
If I want to stay with full decimal numbers (unlike 40.5 f.i.) my situation in improved now. The engine does feel no difference, I understand that, as one factor is increased by the same amount the other one is decreaced. If a VE of 40 was a tad too lean and 41 a tad too rich I now can have a VE of 44 instead - tomorrow I´ll start with that.

BTW: according to the formula Cygnus posted I can see no influence on the enrichments when I decrease the ReqFuel by 1.2 and same time increase the VEs by 1.2

The ASE, WUE, Cranking PW, all that extra stuff, is all scaled to Req_fuel, and none of it gets changed by the tool you just used to scale your VE.

What that means is that all your values for starting and warmup enrichments, as well as a slew of other variables, are now going to be 'off' by the same factor. There is no built-in tool to correct this.

That being said, I was in the same situation. My req_fuel was way too big, and all my values in the VE table were very small, resulting in reduced resolution. I actually took it down from 16 to 10. Yes I had to start over from scratch, but I was doing that anyways so it wasn't a concern. Now my VE table scales from 10 to just over 200, much better ;) It also helps the 3d map actually look like something other than of a coffee table.