GTA

Hello,all

I have just replaced my old multecs with a set of #24 injectors. My BLM's prior to the injector swap was 128/128 at idle and a fairly close to that at part throttle cruise. Now with these new ones my BLMs have shot down to 110-108 at idle and seem to be stuck there at various RPM's ( car warmed up and in park ) .
Question #1 would going up 10% in injector cause such a huge varience?
# 2 to fix the problem should i just start at removal of 10% and see where that gets me?

oh yeah this is all on a 730 SD ecm, thanks looking forward to all your opinions.

AC

iTrader: (3)

I believe the 10% reduction approach is the correct one. That is certainly a safe amount of change.

GTA

Thank you for the reply, any one else have this happen to them? I am just amazed that such a little increase would cause such a huge difference, what effect would a Vac leak have on the BLM's?? I would suspect that it would cause them to roll upwards indicating a very lean condition? I also have noted that since the weather has cooled off the car has a noticible rolling idle when cold and it slowly goes away when fully warm the idle is rock solid. would these 2 issues be related?

RBob

iTrader: (1)

The way I handle this is to change the injector constant to get the best centered 128 BLMs. This is a basic all around 128 on the BLMs.

Then change the injector compensation tables. Usually it is the short PW compensation table that needs a little fudging. Can look at the data log for the PW and the BLM and decrease or increase the compensation as required.

Then to round it out do some VE learns. This picks up the little odds & ends that weren't quite 128 before. Note that 128's all of the time are not really obtainable. They will move some with different weather, and different fuels.

RBob.

GTA

Rbob, thanks for the reply,

Could you please be a bit more detailed in your reply? I was under the impression that now i would have to re work all of my VE tables to correct this..? I Had #22 injectorsBUT my prom was set to 23.5 and it worked well, Now i have changed the Injectors to #24's But have yet retained the setting at 23.5 just to compare. I am now getting 108 in Closed Loop at all RPMs, I will change the setting tonite to #24 But how do i go about getting my Blms back to where they belong? Sorry for the question But heck i am still pretty new to all of this, thanks

RBob

iTrader: (1)

First step is the injector constant. Change that until the BLMs are back into the 128 range. If less then 128, increase the injector flow rate. This will lower the initial commanded PW. Drive it for a few trips (warmed up, up to temperature, normal driving), and adjust the injector flow rate until for the most part the BLMs are 128.

They won't all be, because different injectors have different characteristics.

Rbob.

GTA

Thanks again,

So just so i am clear keep raising the Inj constant and the Blm's will return to 128? Does this not defeat the purpose of changing the VE tables?

Rbob, since i was "very close" in my tune before my VE tables "should be ok" correct ? all i will have to do is Fudge with the inj constant to get things close to where they were before?
PS : I also forgot to mention that the ECM is stuck in cell 4 Now as well, I just read a post regarding this...maybe this is part of the problem?

GTA

RBob,

thanks for the tips... I am back a 128 or very darn close anyway Just one more question will the rest of my Ve tables still be correct as the were before? or will i be doing a whole bunch of data logs come spring and tweaks of the VE tables will be in order? Also the ECM is still stuck in cell #4 But I think that i read and from what i understand this is the idle cell and reving in park will NOT cause the ecm to leave cell #4 correct?? it needs input from the VSS to leave that cell....am i correct on this ? thanks .

Grim Reaper

If you change the Injector size (or fuel pressure) you MUST change the Injector Size constant. The Injector Size Constant is in the BIN for a reason...and it is to properly size your injectors. The VE Tables are NOT the proper place to make modifications and defeats the entire purpose of the Injector Size Constant.

And, the Injector Size Constant is affected by Fuel Pressure. If you run higher than stock fuel pressure, it is effectively the same as increasing your injector size (but not really).

Grim Reaper

There is a good possibilty that you will need to tweak your VE Tables as well - especially if you have changed your fuel pressure. As well, those injectors are measured differently than your stock injectors. As I recall, those injectors are measured at 38 psi while your stock injectors are rated at 42 psi. Those new injectors @ 42 psi are probably closer to 25-26# injector.


BTW, if you were running 128/128 before, you probably didn't need to get new injectors (unless they were leaking). People are too quick to swap out their injectors when a little tuning (and fuel pressure) is all that is needed. And I also feel it is better to use a smaller injector with higher fuel pressure than a large injector with lower fuel pressure.

GTA

Grim,

Thanks for the reply, I Just changed the injectors, the fuel pressure is the same. I Now have the Inj constant raised up to #28 and my BLM's are "back where they belong". This is some really cool stuff, it is really amazing to make a change and see your mods work well, My BLM's went from stinking rich 108 to 127-128 without raising the hood..all in all it really took about 30 min to adjust / scan/adjust/ scan it is good to know that my VE tables "should" not have to be touched, But if they do that is easy as well, but that part of the tuning process will have to wait until the snow goes away
I recall in a old post of yours that the engine seemed to idle better at 127 vrs 130+ range. Mine seemed to be fairly non responsive to idling leaner than 128 . when i was testing the INJ flow rate # in the #30 range the BLM's shot up to 134 or so but the engine just ran perfectly, but i finally settled in #28 which gave me a almost perfect 128/128 so i think that it is a great starting point for the spring.

Eightyninef

lurk

Grim Reaper

GTA, the only time you should adjust your VE Tables (after you have tuned them) is if you do any mechanical changes to your engine. As you now know, an Injector change is best done through the Injector Constant.

A little observation I have made (over time), is the graphical curve of the VE Tables bear a striking resemblance to the Torque curve from a dyno run. Of course, if you tune is really off, this will affect the dyno run. But the overall shape of the graph of the VE Tables (@ 100 kpa) looks a lot like the Torque curve.

vernw

iTrader: (2)

LB9GTA

iTrader: (1)

Did the bigger injectors help in power at all?
Did you notice a difference in idle quality?

GTA

LB9,

I am not able to test due to the weather, the idle is the same as before. I changed them more for "preventive" measures. The idle quality is the same if not a bit better than before. Plus i get to "work" on the prom side of things which i am really starting to enjoy. As for power I dont care so much as long as it runs great and does not hurt a converter(s) and does not burn my eyes or nose then i am happy now to wait 6-7 months for this white rain to go away,

Grim Reaper

If the exhaust fumes are burning your eyes or nose, you are running too rich. Sounds like you don't need MORE fuel, but less fuel.

RBob

iTrader: (1)

The single most important statement of this thread is the first sentence of the first post:

"I have just replaced my old multecs with . . . "

The Multec injectors are worthless. There isn't much else to say about them or how an engine runs when they are in use.

RBob.

LB9GTA

iTrader: (1)

Grim Reaper, I think he is referring to my idle that burns the eyes.

GTA's idle is awesome compared to mine.
Now I just have to get GTA to come and burn me some chips before my idle kills more trees and flowers

GTA

Hello, Folks

Rbob, your correct I really wanted to get rid of the Multecs as i have done a LOT of reading and agree that the Multecs are very problem prone, mine were working ok but why wait for trouble so they have been replaced by a Much better set.
2. LB9 i was not refering to your idle, it was just a general statement.Mine does idle well. Sorry for the confusion.
3. Grim, Correct i have pulled a lot of fuel out of my bin and this injector/ecm works great for me. I was just simply stateing that i am very impressed with the way prom burning has enabled myself and many others to make changes within the bin to work with mods. For example before DIYP i would have to fiddle with fuel press to comprimise one area for a loss in another,DIY prom has made this tuning process so much easier, and will help us realise the most from our mods.
Thanks folks, and again sorry for any confusion. GTA.