can anyone explain how exactly it works?

i know the ecu is in open loop during cold start until all sensors are online
then during acceleration it switches to open loop



during closed loop ecu adjusts the short and long term trims to kee it close to 14.7

does that extend to open loop in any way at all?

or once in open loop during wot the ecu doesnt rely on any sensor feedback?



im asking because im not sure how much change is there from adding boltons and an AEBS intake manifold.

and if the ecu adjusts at all during open loop

OBD2-B p2t ecu

 

Im not entirely sure but I would say no. Once in open loop the Ecu should disregard ALL sensor feedback. Certainly not short term feedback because that would, by definition, be close loop. But the question I am unsure about is long term trims are applied overall (even when at wot). I would think not but am unsure.

 

It does not do anything with the long term fuel trims. That part is only there to throw a code to abide by obd2 standards. Open loop is not affected by it at all.

 

has anyone done a before/after pull with a wideband datalogging?

i havent found a single graph to show how much a typical b series engine changes the afr after boltons on a stock ecu

because most of the cars on the road that i see have basic boltons and full exhaust with stock ecu and have no idea what the afr readings are at wot

 

Open loop= fuel and ignition table lookup based on tps and map sensor
Closed loop=fuel and ignition table based on O2 sensor AFR is always around 14.7
During closed loop some Hondas like to run lean 15+AFR in idle and cruise

Adding boltons ie I/H/E will likely run lean since honda uses speed density sensor

 

Closed loop is only active below 60% throttle and for most applications only corrects the AFR to 14.7:1, nothing more. This can not - and should not - be active if the throttle/load is over 60% which means there is no fuel correction for mods.

A GSR with Skunk2 intake manifold and full exhaust (a common tune I do) can require up to 20% more fuel than the stock maps. Even just an AEM intake and full exhaust upgrade can lean you out to 15:1 AFR (+11%) at 7000 rpm. Any time you modify an engine it should be tuned.

 

i was just confirming its been a while since i red that stuff on pgmfi.

but alot of people look at me like im crazy when i tell them that they should tune it when they put intake and full exhaust system

because everyone is doing it so its assumed that its ok.



does that apply to all ecus obd1 obd2a obd2b and the newer ones like k series?
or the k series stock ecu is more flexible?

since they have much more processing power than 92-01 ecus

 

I think newer Hondas use a 5v wideband style o2 from the factory

 

Some of the K series and V6 ECUs run OEM wideband, but not all. None of them use a full-time closed loop system though, it's primarily done for better economy on VVT engines. I don't believe it's a linear 5v signal.
Newer ECUs are more 'and' less flexible. They're tuned better to begin with, so you won't get that much more out of them with minor bolt-ons. The pre-2002 ECU has virtually no usable learning capacity, and until 2007 there still wasn't much to be said about flexibility.
New ECUs do have segmented learning tables that can estimate high load values with enough data, but still nothing compared to other manufacturers and it definitely can't hold a candle to a good tune. If you exceed the learning limits (25%) you'll throw a code.

 

one more question.

everyone says to reset the ecu to clear the memory
what data is actually stored in ecu?
short/long fuel trims?
is long term fuel trim a graph for each rpm/load or is it a single number across the board?
idle information?
same in obd1 and obd2?


I have a scan gauge hooked up to my ecu now and I was under the impression that longterm fuel trim is stored in ecu

but every time I look at it it starts at zero when the o2 sensor is warmed up and then as I drive the short fuel trim adjusts first then long trim changes afterwards.

 

obd1 is caveman technology, it's one value for LTFT and one value for STFT. It erases every time you turn it off. ST is a couple seconds, LT is basically an overall average.
the intelligence and table dimensions vary depending on the ecu and year, but if it doesn't have a visible learning table in your rom editor, it's one value. generally pre-2005 Honda ecus are single value with a few exceptions, but you'll learn those easily if you end up tuning them.