E40 ECM scaling for 160-190lb injectors

[jarrah]

u mean the ones under open closed loop "open loop gains" so lets say I multiply my STOIC by 2 I need to open those tables and do the same

[jarrah]

thanks guys found it

[schpenxel]

It's the engine-->fuel-->general "Stoich AFR" in "Air Fuel Ratio" table

[trd800]

Do you do the same for E38?

[schpenxel]

Yes double stoich/half IFR will work on e38's. Cut the IVT terms in half also

[trd800]

Ok I have E38 PCM which only goes to 63lb/hr & not 127lb/hr. The injectors supplied are ID1700's running 42psi so 160lb/hr.

Do you think this should work:
IFR divide 2.6 = 61.5lb/hr
Stoich x 2.6 = 38.2.....wait I can only goto 32stoich!!

Any idea's?

[schpenxel]

Yeah the double/half thing only works to the point that you max out the stoich table unfortunately, so around x 2.17

[trd800]

And doing the double/half method along with the old rescale method will just be way too hard I think. Sounds like it needs new PCM that can do 127lb/hr with smaller injectors..

[schpenxel]

Yeah that's a bit much. I'd probably just start over if I was going from rescale method to double stoich method. If you were only 10% off from getting to the right injector flow rate then I'd just go with it, but you're going to be further off than that with just the double stoich method

[5_Liter_Eater]

Correct. It's very few things.. stoich, injector flow rate, IVT terms. That is it

I'm not following what the IVT terms represents and why it should be halved.

[5_Liter_Eater]

And doing the double/half method along with the old rescale method will just be way too hard I think. Sounds like it needs new PCM that can do 127lb/hr with smaller injectors..

I've had to do both. I did the rescale of the entire tune way back before the double stoich method was around. Then I went from 1k to 2k injectors so then I doubled stoich.

[schpenxel]

I'm not following what the IVT terms represents and why it should be halved.

They are coefficients that are used when calculating intake valve temp, they should be cut in half when using the double stoich way, otherwise the IVT ends up being something stupid high. I assume it thinks you're running really lean since you have a stoich AFR of something 29+ but don't really know the details of how it's calculated.

They are under fuel-->general, "IVT Terms". There are two tables, one of the is typically 0 so you can ignore that one. Cut the other one in half

Will it really make a noticeable difference? Heck if I know.. it probably will for transient fueling but I doubt anything will go boom if you don't do it

You can thank DSteck for getting us access to this one

[5_Liter_Eater]

Well I'll find out soon as my tune is pretty lined out now so when I half the IVT terms I'll see if it makes a difference.

[schpenxel]

That will be interesting. To me anyways

[mowton]

My theory is somewhere in bowels of the IVT equation is an element pertaining to fuel mass and its ability to modify thermal changes to the valve vs ECT or something. The IVT Terms must be the keys to the crypt and when we cut the fuel mass in half, so must we change a variable to bring it back.....and Dave figured that out...Thanks man

Again, this is just MHO..

Ed M

[GHuggins]

Uses them for cold engine desired ratio (adders, multipliers) and transient fueling that I know of.
Doesn't the instrument cluster outputs not need to be halved as well when doing the double stoic trick?

[schpenxel]

Uses them for cold engine desired ratio (adders, multipliers) and transient fueling that I know of.
Doesn't the instrument cluster outputs not need to be halved as well when doing the double stoic trick?

Yeah you do need to mess with that.. I don't have access to that one on my E40 so I always forget about it. Something about fuel density I think it's labeled?

Good news is I get 800 miles per tank

[realcanuk]

I started using the double stoich method before anyone talked about halving IVT. I didn't see any change when I did do it later on, but it could be effecting something that I just didn't notice.

[5_Liter_Eater]

Seemed to lean out my tune quite a bit. Particularly in the smaller pulse width areas

[schpenxel]

That is interesting. Though we'll probably never know why..