SBD

Can someone explain what happens when IFR are modified?

What affect does modifying IFR have on LTFT and WOT?

Does it affect injector DC at all?

brad8266

iTrader: (23)

IFR will have a direct affect on LTFT's as well as you AFR at WOT. Do not change IFR at all unless you change to a different sized injector. Do tuning via VE and MAF tables.

RedHardSupra

iTrader: (1)

so let's say you're mixing cement

your shovel can move 1 pound of cement per second to the mixer (or whatever that's called) you supposed to mix cement and water in 1/13 proportions. you have a hose going in there that you believe delivers 13lb/sec of water. however, the hose is clogged, and you don't know about it, all you know is that your mixture despite your best effort is a bit off. so instead of checking what's wrong with the hose, you decide to grab a bigger or smaller shovel depending if your mixture is too watery or too solid.
did you get the right mixture in the end? yes. did you get the right amount of it? no!

this is exactly what IFR tweaking does to your engine. instead of looking at the source of the problem, you just try to make up for it somewhere else.

brad8266

iTrader: (23)

Well said!!

ringram

Yep, consider your IFR a constant like cylinder displacement, or cam spec. Set it to what it should be and forget it.

tici

iTrader: (1)

Timing depends on G/cyl which depends on G/sec.
I don't agree with this of tuning the MAF table because it messes with timing too (indirectly).
I really prefer IFR alone.

brad8266

iTrader: (23)

Doing it via IFR is just fooling the computer. Wouldnt you want your sensors to operate like they should and accurately report the amount of air entering the engine? Also if you unplugged the MAF the pcm has to get timing from somewhere and I would say that it gets by the timing via the spark table which is in gms/sec but since the maf is unplugged it uses the MAP and converts the MAP signal to what it would be in gms/sec and applies that to the spark table to get the timing, keep in mind that IFR is ran by MAP signal also as well, so either way the timing would be scewed by your assumption. Someone correct me if im wrong.

RedHardSupra

iTrader: (1)

http://redhardsupra.blogspot.com/200...ing-jihad.html

enjoy

SSpdDmon

iTrader: (10)

In EFILive, it tells us that timing comes from the GM.DYNCYLAIR_DMA pid. So, regardless of the MAF, timing is calculated this way. Not tuning the MAF is only going to lead to bandaiding the fueling to get your AFR's in line (just the same as "tweaking" the IFR tables).

TAQuickness

iTrader: (28)

as an additional perspective...

IFR is an easy constant to get right. VE can be tuned with a correct IFR, and MAF can be tuned with a correct VE and IFR. Now spark can be tuned because MAF, VE & IFR are correct.

joecar

And if IFR, VE, MAF are correct, then PE becomes 'what you see is what you get'.

RedHardSupra

iTrader: (1)

it's not THAT simple, but it is the idea. normally spark and ect has a lot to say about your real vs commanded afr. it is helluva lot closer than doing it using any other method, but the best part is that the only thing you have to change is PE, which doesn't screw up your normal driving, as it applies only to WOT.

brad8266

iTrader: (23)

I knew timing didnt come from MAf cause if it did and the maf broke timing would be screwed.

brad8266

iTrader: (23)

Its great now that I got ve and MAf dialed in cause now I can easily do the division in order to quickly go in and change AFR. Every time I want to change AFR at WOT all it takes is a quick change in the PE table and its done.

tici

iTrader: (1)

From where is this pid taking the G/cyl values? If not from the MAF then it should be from the VE (what else could give an information about that?)