RomRaider

I have been stewing over this for a few days - Most stand alone or flashable ecu's I have seen dealt with use the term "Dead Time" when referencing injectors.. Does Subaru have a direct - this is latency and only the amount of time it takes the injector to open or is it used with a formula or equation? For instance I was told that stock 420cc injectors (tested by more than 1 place) have a dead time of over 1.05ms (lowest I was told) but subaru scale it to .69ms. This does not make sense to me why they would use such a low dead time if the injector truely has a dead time of over 1 ms...

I know I'm rambling but things don't add up, I know Subaru uses their maf scaling on v7+ Sti's to compensate for fueling, but why not use latency? Is there something we don't know?? That has not been seen or understood? Could knowing this increase our ability to control fueling better (smoother closed loop?)

I found a few threads on this (Gabedudes) but nothing was really answered or figuerd out..

-Jerod

Definition of latency...

"reaction time: the time that elapses between a stimulus and the response to it"

Sounds like a fair usage of the terminology. I think it's just semantics.

The other issue (measured latency vs. latency values in the ROM) is probably a combination of the MAF scaling things you mentioned + differences in the way it is calculated + other IPW compensations happening in the ECU that make up for the difference.

there are no step functions in the real world.

Neither "latency" nor "dead time" is a completely correct term for this situation.

The injector have a couple of valuable parameters - valve openning time and valve closing time.

Their difference (that make sense for the fuel injected) is commonly used as "latency" or "dead time".

Both of them are mechanical (spring flexibility, armature mass, solenoid core) and electrical (coil turns, coil resistance) dependent. But. Openning time depends on (battery voltage-driver saturation) while closing time is dependand on flyback voltage allowed by th ecu scematics.

The last means that besides the injector itself the ecu scematics also determines the "latency" to be used. The less flyback voltage the more closing time and the less "latency value" is to be used.

I hope this helps.

Sort of - I guess I'm curious as to exactly what the term Latency means to Subaru/Denso in their rom..

I know latency/dead time is comparitavely the same thing using a different term.. I have a good understanding of how it works and things that do effect latency - non permanently and permanently..

So why did Denso/Subaru use a latency value for stock injectors that is, in no way, right? At least 2 injector companies have indicated dead time/latency values of wrx injectors over 1ms when subaru uses .69ms -

Why should we use the maf sensor to ensure proper fueling? Technically if everything were ON par - the maf sensor should only have one scaling per tubing size (IE somone needs to flow bench a maf sensor at 68*F) and report output voltage at known flow rates.. This would ultimately provide proof that one or the other is false...

I have found that with larger injectors and KNOWN latency values that the larger I go over stock the more the maf needs scaled down low vs the stock injectors... This makes little to no sense to me.. Why would a larger injector need more maf scaling? And on top of it the larger injectors have higher latency values (by almost 2x) so this to me would push fueling rich..

When I add latency to "compensate" (add to KNOWN values) I have problems under high loads (knock even on E85) almost like the injectors are opening to early - so this tells me my latency values are good where they are without raising them - but I still have to add almost 20% to the maf scaling on a stock intake... It makes no sense, almost like the computer needs to force more IPW at low rpms/tps...

I don't understand that whole sistuation there must be a different definition to Denso for "latency" then what we truly know...

-jerod

There are no "terms" or descriptions used in the ROM. If the tables were all labeled, that would make it a hell of lot easier, but they are not - nothing is. Any table name used in the RomRaider/Ecuflash defs is something decided by me, although I'm not an engineer. I do sometimes use terminology described in factory manuals. Some labeling I got from patents (such as feedback, fine, rough correction). Some of the common table names that were already widely discussed in forums from commercial software before RomRaider existed, I used that terminology (ex. turbo dynamics, IAM). Some I just thought of a name that best described the logic.

In this case, Subaru uses the term as follows in the factory service manual:
"Voltage correction time ..... This is added to compensate for the time lag before operation of injector that results from variation in the battery voltage."

Way to go Bill - Way to make me look stupid again!!

Ok then lets reroute this quesiton - why does subaru use the technique for fueling that they do? Keeping latency's the same between different injector models and altering the maf scaling?

Some things just don't make sense on their approach - I've been through 25+ OE roms and looked/learned on their style and 99% of their technique is to use a similar or same latency value and change the maf scaling - What doesn't make sense is the MAF is not changing the injector is, so why would they go this route? Seems more complicated and roundy round to me...

first, hello!

Borrowing old tread but I´ve been looking for 05 EDM WRX STI map and was wondering how does latency have thosekind of voltage ranges?
Seems odd that one would ever need 6.5 , 9.0 or 16.5 volts???

Or is there some greater locig?

You can hit 9 while cranking on a cold or weak battery.
The out edges most likely just help with the shape of the curve.

ok, great, thanks for info.

but should it be more helpful in scaling if 6.5volts would move upper?
other manufactorers ecu´s wont even allow starting under certain voltage...

I know many has their own way of tuning but this could be also suitable option if I want to adjust fuel delivery

Lower voltages are also seen when the alternator (or a connection to it) has failed and the car is running off of the battery only. I'm not sure what the lower voltage threshold for the ECU is but it's a good idea to have some valid values in the lower areas. It might get you that much closer to a safer place to stop on the road.