RomRaider

Fuel Trims are based off of the O2 sensor. When you 'stab the throttle' the TB plates open and the I/C pipe acts as a plenum. Acceleration enrichment takes over trying to control how much the O2 sensor modifies the mixture. If AE is set accordingly, then your Short Term trims won't change very much if the MAF is nuts on. But, we don't have access to enough Acceleration Enrichment variables/tables in order to really dial this in.

IMHO, the turbo begins to spool and reaches that spooling point and draws in a huge gulp of air that rushes past the MAF. The ECU sees this as a change in load and injects more fuel. Unfortunately, it takes an extra very short period of time before that air charge gets to the motor. Meanwhile, the fuel has already started spraying.

The FMIC and it's piping have drastically more volume than the TMIC setup.

t

So it would be better to tune a FMIC with MAP then MAF..
Couldn't I tune with MAP on stock ecu. ? I'm very new with this.
I have a stage 2.5, VF34. Since FMIC are lot more cheaper then what it was, it seems like a good upgrade.

I was under the impression that the o2 sensor data input only applied to closed loop fueling. So if yours falls out of closed loop right away like you stated, how can it accuratly know how much fuel to apply? I agree there must be a table that we dont know the location of.

look at ecu edit, all the tables are there, just no supporting definitions yet. some day it will happen....

Yup - I have done this too. Unfortunately, we are talking about an extra couple hundred tables I've looked through them ... but wow that would take a LOT of reflashing.

t

OK, I need to be more specific. STFTs are active in closed loop only. LTFTs can be active in closed and open loop. LTFTs are learned based off of closed loop and the input of the O2. However, the ECU has the ability to extrapolate LTFTs in order to both add and subtract fuel during WOT conditions too (with no feedback from the O2). STFTs are always based off of the O2 sensor and happen only in closed loop because it NEEDS the O2 sensor in order to make it's adjustments.

Regarding your comment 'accurately apply' ... the word 'accurately' needs to be defined. You have to be specific with regard to what you mean. The ECU has no ability to accurately achieve a given AFR at WOT because our cars do not have Wideband O2 sensors. HOWEVER, the ECU can accurately determine what it THINKS it needs in order to achieve that AFR based off of the voltage reading from the MAF, a g/s lookup, and some calculations in order to reach that target AFR in the primary fuel table.

t

That's xmlwrite defs for 32bit ecus, which you can also use with RomRaider. The 32bit roms have map look-up tables that define every 2d/3d table in the ecu, so you can generate tables from this which is what xmlwrite does. Of course, it doesn't tell you what it does or what the axis values are - that is all disassembly. Unfortunately, there are literally 500-700 2d/3d maps and even more 1d parameters.

Tuning based on MAP is not currently available except through UTEC (or a standalone). MAP fueling is called Speed Density (alpha-n, etc). This would definitely take care of the issue in my eyes because fueling is completely determined by the pressure in the intake manifold (meaning that the manifold is already pressured with the air charge - that air charge is not WAY upstream).

t

BTW - I want everyone to know I am open minded here. If there are any ideas that I haven't tried, I will try them - just let me know.

t

Thats exactly what I meant, the ecu can only calculate what it thinks is correct based on what you described.

And, in the end, it is our job to help the ECU to determine the best way to calculate things correctly. Options as I see it are a blow through MAF where the MAF is alot closer to the motor ... or, having access to more data tables such that we can either input the MAF Delay or fudging it through access to an 'acceleration enrichment vs. delta load (or MAF V)'

t

I just decided to scrap all this talk and go blow through with a 3" section of IC piping about 1 ' away from the intake manifold. I am going to change it up this weekend. Ill let you know how it goes.

At what speed does air pressure travel?

There is a throttle delta table. It should be in every ROM XML by now. You may want to tweak it.

One of primary things you may want to do to tune for a FMIC is to flatten out the IAT temperature to timing compensation. Most of the stock ROMs cut crazy timing if your IAT goes over 40-50 C. If you have a front mount and shortram, you don't need to cut 5-8 degrees of timing to keep things safe.

I've already done all of this - so have others. Again, this isn't a noob post Don't get me wrong - I like suggestions. It's just that we've tried all the obvious stuff (ALL accel enrichment stuff has been tested to the extremes). We've even tried stuff that others wouldn't even think of. We (not just me) still have this issue. Yes, we can fudge it. But, we can't 'fix' it (unless we go blow through which creates it's own set of problems).

t

Another option may be to have a reversed inlet manifold with the inlet at the front of the engine and much shorter ic pipework. I think the turbo can be mounted at the front of the engine too, but there's quite a bit of work involved in all this, some of it custom.