Boosted 3100

[Vbb1994]

hi all. first time posting here. been lurking a bit.
i have a 3100 lumina, 1999 that ive been tuning on hptuners with a aem wideband and all that. i had my fueling and modes all dialed in good, and then installed 36 lb injectors from a L67 and am currently working on a retune for those before i boost the motor. i have some questions however regarding fueling and all.. perhaps someone can help.

first off, i noticed that the P04 OS i have right off has alot of missing parameters, so i created and add the ones that was missing via the tiny tuners database, and TunerPRo for the .xdf's i need.
with this capability in hand, i obviously peaked in on what my luminas 99-00 SC counterpart would be hiding.... similar stuff. notably i want to say i saw the p04 has a map scale offset and linear setting which peaked my interest. so i start looking and learn obviously i can offset my own lumina's map scale and linear and probably run a 2 bar brick MAP .. no doubt. correct me if im wrong ....

heres my question for you lads.... how do you fuel above 140 kpa?? or time it above above .92 g/cyl? isnt 140kpa actually 5 psi? doesnt the 3800 s/c stock do 8?

the SC and n/a p04 ecm OS's only share one difference that i see. the S/c OS uses 0,10,20,30 - 140 kpa. the 3100 uses 30-140 kpa. ? what gives.

so my curiosity was peaked more. i browsed the forums here for guys running 3800 motors that posted datalogs so i could see how they behave in boost.

i find a datalog from a guy doing a pull in his car on E up to 11+ psi and he hits 190 kpa, 1.06 g/cyl, but his MAF meter only reaches like.. 10,750hz
the timing continues on at the last place it was at which is 22 degrees, and fueling never really drops off.

im a lil confused how that works since theres no map scale for that much. i know that in the p04 the VE is used for transient and maf is king, and i plan on boosting the lumina and controlling it with my maf meter.. blow thru.. but how can i be sure i wont like, run lean and explode past 140 kpa like the s/c does?

thanks guys.. i appreciate any insight.

[Vbb1994]

since this post ive just naturally done alot of reading on my own and learned things. no doubt you must rescale your injectors to time higher boost levels. ive already seen you can put fake data in and get wild cyl pressures.

the tune is done, im just finding the right afr it likes from the bottom end pre 2500.

heres my question now, instead of this earlier one. hopefully someone can help. i see within the ecm i have an IFR lookup mode. either by Engine Vacuum or by VE. i have a regulator and rails, but mine stock is setup by VE. would i continue to use this for boost? or switch it to IFR? it would make more sense to me to keep it VE for now i guess? i saw the 3.8 , or at least the one i looked at uses the IFR table. my most important question i have is, how is it being fueled past 100 kpa? i know the 3.8 is a maf based system. and more direct and to the point, which should i use when i boost my motor? ifr or ve? either ones gonna have to be scaled to get the correct g/cyl to time the motor, right? thanks guys.

im keeping my maf to fuel my target of 15 psi, i just guess i dont understand how the ecm interpolates beyond 100 kpa on the IFR table. i see the VE is 140 kpa, so i got... what? 5psi i can fuel? after that what happens? it looks to the maf only?

[5FDP]

Aren't both the 3100 and 3800 MAF based? I thought they ran the same computers.

Basically they are fueled with the MAF, the VE will always max out when running above 5psi. So the MAF is the way we fuel them. Lots of guys will end up installing a LS1 MAF which is larger to get more resolution.

Anything injector wise is a set and forget table, you don't change anything once the data is put in there.

[Vbb1994]

Aren't both the 3100 and 3800 MAF based? I thought they ran the same computers.

Basically they are fueled with the MAF, the VE will always max out when running above 5psi. So the MAF is the way we fuel them. Lots of guys will end up installing a LS1 MAF which is larger to get more resolution.

Anything injector wise is a set and forget table, you don't change anything once the data is put in there.

Hey thanks for the reply. I apologize for intially posing such a noob question, but ive learned alot.


Yea, same computer on the 3.1 3.4, and 3.8 it appears. P04, except the 3.8 seems to consistently have a 0-140kpa scale, but the 3.1 is 30-140kpa.

Kinda weird?

Is there any real value in buying a 2 bar brick map and doing a MAP rescale and offset? (I found these tables and created my own on tiny tuners for these two tables)

And what about that ve vs IFR lookup mode?

Its not a setting hpt provides, but again it was one within the tiny tuners DB, that i made for me to switch.

Theres others like i can change how transient airmass is calculated, but the focus is on how to properly fuel the injectors.

(And thank you for just telling me what i was deducing on my own from looking at other peoples tunes and datalogs)

It just exceeds the VE and goes back to maf. Or like i got it now, its maf all the time


So do i need to add a 2 bar map and rescale so hptuners and my ecm will read 140kpa? (I know its just for information sake , not fueling, but i want to be able to determine my afr and tune based on kpa, so i need to accurately log it.

[Vbb1994]

Might be a double post.

That IFR lookup mode.

Which would be ideal for the boosted motor ? VE based or the single IFR lookup table ?

[Vbb1994]

Anyone? Regarding the IFR lookup mode ?