Thread: Deka IV (4) 80# injectors?

Originally Posted by matt5112

Well op, I'm wrong, there is no solution.

Thus play with ifr and the maf table until its close.

I will try your way first and see what happens. I am just saying I am open to suggestions at this point. I just want to get these nailed down as quickly and correctly as possible.

Everyone I know with 80s (I have never ran into a set myself) are using stock offsets. The injectors are fast enough that stock settings will be more than enough to handle controlling them down low. If you have the paitence to deal with the minimum injector pulsewidth values, then I would consider playing with them for a bit based on how different they are from stock (you will need stock 33# injector data measured in the same way the 80s are if you were to calculate anything).

http://www.injectordynamics.com/ID72...03-23-2011.xls

This corresponds with my initial assumptions.

Originally Posted by matt5112

Well it seems my understanding of the tables was correct.

The voltage vs offset is the voltage vs offset.

The offset vs PW vs MAP is the short pulse adder. If your fuel pump can keep up then the MAP component is irrelevant and values in all columns should be the same.

But the data is still not correct as that data is for 4 bar when we have a 3.5 bar system.

Offsets will be lower as will the min pulse in our system.

nice try, but you forgot about minimum pulse width.

It sucks that you cant, and its not particularly required for proper adjustment, it just is IMPOSSIBLE to know where your OFFSET should be... as the offset is a direct hook onto minimum pulsewidth.

Its the "base value" in the whole injection system... which is why you need to know it and how it works before you can go about adjusting offsets.

PS. Matt I can really appreciate the effort you are putting into start learning these things. I may suggest it is a bit easier to work with me on these subjects instead of saying I am wrong/ignorant of things in the future. I have quite a few bits of information after I have tested many of the min pulse width and voltage offset values in the PCM... and you would really be suprised to see how (poorly) t works.

You were the one who jumped to tarnish my name first.

You also mentioned the min PW is different yet failed to specify the value.

Also you've mentioned in another thread some particular OSID's have been mapped further than others in TT.

Has the stock min PW been located there?

One interesting thing is the min PW for every injector listed in the banish data minus the 80's has the same min PW of 0.8 which also seems to be the default setting in a few LSx OSID's as well.

And the min pulse width in 3800 files is 1.3ms... which completely and utterly breaks any offset values based on a .8ms by .5ms

ninja edit? for real?

sucks doesnt it.... The 98 camaro file I worked with had 1.3 as the min.

Nope.

Min pulse width is the minimum amount of lead time the injector needs to actually spray fuel. The offset modifies the min pulsewidth in terms of addition. Think of the min ipw + offset value as a "boot time" of the injector.. the amount of on time needed to begin fuel injection.

The calculated pulse width coming from the air mass side of the pcm uses these constants to build on, as it uses this as a floor to add onto... in crude terms... if your min pulse width value after offsets is 2.0, and the air/mass side decides it needs .5ms worth of ipw to get the fueling it wants... it adds onto the min+offset value to get the objective IPW of 2.5. To think of this objectively.... lets say that 20ipw is "100% fueling"... in this case an IPW of 2.0 would be 0% fueling, and an ipw of 12.0 would be 50% of max flow.

This is the reason why you can commonly see injectors pushing 110-120% while still maintaining fuel resolution... because the injectors are in batch fire above 3000 rpms you can start overlapping the dead time after you get passed your calculated max ipw.

I keep seeing a very different definition though.

HP Tuners Bulletin Board - View Single Post - What are 'Short Pulse Limit', 'Minimum Pulsewidth', 'Short Pulse Adder' ????

minimum pulse width is the minimum allowed pulse width when all calculations are done. no pulsewidth will be allowed that is less than this.

short pulse limit and short pulse adder table are meant to linearize the injector output, becuase at small pulsewidths (below the short pulse limit) the injector doesn't actually deliver what you are commanding it to, the adder takes care of this.

Chris...

Ideally the injector would entirely linear.

Going off that assumption, would the PCM not calculate first required fuel mass, then PW required at the IFR you provide then proceed to apply corrections such as offset and if necessary, short pulse adder.

Min pulse width in a 3800 pcm is dead time.... If you find otherwise congrats but I have tested it sucessfully. In LSx platforms they may use it differently, but the value found in the 3800 is the same as what is in my AEM/MS/BS3 pcms I tune.