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

Hello
We have been trying to figure out why our engine leans out at higer revs.
Logs, and msq can be found here.
http://www.dryg.se/~lasse/MS/080601/

Issue
Engine volvo b23, NA, twin throttle bodies 48mm
4 High impendance injectors @354cc/min
lamda LC-1
MS 2.0 V3
MS II code 2.885
Megatune 2.55p3

Engine Displacement 2314cc
Number of Cylinders 4
Number of Injectors 4
Number of Squirts 1
Injector Flow 354cc/min
Injector Staging simultanious
Fuel Type Gasoline

We first calculated our req_fuel to 11.4 and tried to map with that, but our VE then did not allow verry much, since many fileds ended up at more than 255 in the chart.
So we doubbled the req_fuel to get more room for mapping. Rec_fuel is now @ 23, but we still got tendency to lean out att high revs (255 in VE)
But Megatune does not allow us to have higher rec_fuel than 25, but we need 11.5 x 3 = 34,5 to get the VE corrected so we can map further.

Anyone with experience with alphaN mapping that could tell us where we went wrong?

Lance wrote:psbryt,

I didn't look at your log or MSQ, but it sounds like you have hit the duty cycle limit and need larger injectors (and smaller req_fuel).

There is a pulse width limit in MegaSquirt, and I blelive it is 32 milliseconds for recent code. With a req_fuel of 34.5 and a VE of 255%, you are certainly over this. Again, the solution is larger injectors and a smaller req_fuel.

Lance.

The thing is that we calculated roughly that we have
200Nm tourqe
250Hp

The injectors should be large enough
Eaven if we alterd the req_fuel we did not se wider PW..the longest pulse we have seen is about 14

But we are now investigating if the fuel pump/filter is sufficient, so we are going to monitor the fuel pressure during load.