Ok heres the specs probably not needed.
Car is 94 integra b18b1
Chipped P75 tuning with crome.
afr is innovate mtx-l

Question is, while street tuning my afr i know i need it in the neighborhood of 11.5 on boost. Should it be that at low boost, say 2-3psi not yet spooled? Mine is more like 12.5. Im only hitting 6psi right now. Figured i would tune it at that and turn up the boost a bit later. The thing pulls pretty hard at 6psi. Really surprised how hard it pulls.

 

How big is the turbo?

Fi uses fuel to combat cylinder temps.
13.5 is where you make the most power
Fi raises cylinder pressure so much we need to run richer to combat heat

11.5 burns slower then 13.5

Depending how much power your making you will want to run richer. Add timing pull timing etc

You saying it pulls hard at 6 psi tells us nothing

 

I believe he is asking if AFR needs to immediately jump down from ~13ish at 0psi to ~11.5ish at low boost. I would answer no. All fuel trends should be gradual. However the better question is how fast do you ramp from NA to FI AFR?

 

Exactly what i was trying to ask. Thank you.

 

I have decent amount of turbo lag so I have mine tune from 14.7 low load 13.8 mid to high load
12.8 0-5 psi and 12.3 at 10 but in a linear fashion .... When I switched manifolds to a log it spoiled faster so it needed adjustments ... And u only really need enough fuel to lower heat and to prevent knock so low boost can be leaner and still be "safe"

Every motor and setup will be different

 

Mines tuned for 12.5-12.0 from 0 to 5 psi, then 12.0-11.5 from 5 to 18 psi. Running a GT28RS from Garrett on a D16 dohc engine

 

Cool. I am on the right track then. Just turned it up to 10 last night.

 

Some of these comments brought another question to my mind...

In lower Air Temps, can I lean out my A/F a tad since the incoming air is so cold? And if so by how much?

Doesn't cold IAT = cooler cylinder temps? Here in UT the air my engine sees can get pretty darn cold in the winter. Sometimes in the teens. But I have my A/F pegged at 11.7 at all temps.

Thoughts?

 

Technically yes but colder air also means more dense air so more fuel is needed either way... so to help the iat temp compensation can be played with so it doesn't effect it under normal operation temps

 

Colder air= dense air

More air will fill the cylinder.


Removing fuel make motor go bang.

 

Well I didn't mean that I would lean it all the way out in the winter when IATs are way cold. I understand that colder air is denser. But its also, well, colder.

In the IAT comp table I could set up an A/F of ~ 12 when IATs are in the teens, but then like 11.5-7 ~ ish in the summer when IATs are up over 100, interpolated of course. So not a LARGE A/F swing.

What do you guys thing about that?

 

Seems reasonable but it'll have to come down to checking the plugs after some hard pulls to know for sure

 

Read the Crome manual in my signature, it has a section on target AFRs.

 

For IAT's and fuel compensations theirs adjustment tables for this in any platform pretty much....shoot I was just playing around with this yesterday in Crome because it's getting hotter down here in the fun shine state and when the IAT's go up the oxygen volume is less for the air vol being ingested therefore fuel volume needs to be trimmed globally to keep AFR's from going too rich when she's breathing hotter air....the reverse of course apply's to colder IAT's so slightly more fuel is added globally but I don't add any additional fuel through the main tables unless I feel it's needed overall irregardless of the ambient air temps

 

What i did is add 1 percent fuel for every 13 degree change.

From -40 to 86 degrees i added 10 percent fuel at -40 and interpolated it down to 0 at 86

Did the same from 104 to 210 is the max the sensor reads

Same thing 210 came out to 13 percent fuel and i interpolated it down to 0 at 104

With a good intercooler your temps under load should stay around 86 to 104.

This is done after the motor is fully tuned of course

My numbers will defer from other ems systems. So do the math or mess with your own individually

 

PS leaner exhaust is hotter, which scavenges faster and spools a turbo quicker. mitsubishi ECUs actually have a lean-spool function specifically for that. other turbo ECUs just have a lag from CL/OL to keep it lean.
in theory, AFRs should be as lean as possible to make the most power. we only set standards for safety, but... who cares about safety.