There is another area in the XDF to control your steps during cold startup, although my location may be labeled differently (IAC - Powerup Init Steps), and it targets the step value based on the corresponding coolant temperature, yours may need some attention below 115-degrees, those values in your bin may be too high and letting too much air in, especially with only needing 5 steps to idle correctly once fully warmed up. As for the 100-RPM difference, is your throttle's fast idle screw fully closed?

I'll give that a shot tomorrow and just reset my tables and see how it turns out after some driving.

I've been staring at that parameter for awhile now and have been hesitant to mess with it since there's so many IAC settings but I will try messing with that when I get a chance. Also I'm pretty sure the screw still has room to go both ways. From what I understood I adjust the screw until I see the steps I want at idle in the WUD and then after a restart the IAC will reset and will correct to minimum idle which is why I'm confused as to why it's not whats being commanded.

Keep the fast idle screw closed, the IAC wants full control. If your running a cam as big as mine you'll want to help the IAC maintain the idle by cracking the throttle blade open until your happy with the steps. Back off your fast ide screw, close the blade, and watch your steps increase with just the IAC controlling your idle, and your RPM will lower to the commanded value. A 5 count is very low, almost closed. If I had the XDF I would look at your bin, as it sounds like some of the other settings are playing tug of war with the commanded steps and commanded afr...

I was under the impression that I needed the steps to be 5-10 at warm idle since I was running TBI? Or is this something that really depends on what the engine wants because I'm still running the stock cam in a month or 2 I'm gonna swap it out for something else and I'm sure everything will change and I'll be tackling all of this over again lol.

Yes, but the difference between those 5 & 10 steps is your extra 100-RPM at idle. I didn't mean to imply that the steps will be able to go up drastically once you close the throttle blade, the steps will just go up enough to maintain the commanded without any help from the throttle. If you command 5 steps at warm idle, but introduce more air during warm idle by cracking the throttle blade open, you essentially created an even larger vacuum leak that your IAC cannot correct for. Give it full control and see what happens...

Since you put it that way it makes alot more sense to me. I didn't think 5 steps made that much of a difference. I will be testing alot of different changes later today after work I'll report back and let everyone know how things turned out. Thanks again!

I take it you're referring to the complete concept behind pulse width and fueling, so taking a shot at this: the pulse width is the key to how much fuel will be injected, since the ECM can't influence things like fuel pressure and it don't have a way to directly measure fuel flow through the injector.

So what we do is this: knowing that an injector flows X amount of fuel at Y pressure (let's assume static pressure for now), resulting in a mass flow in pounds per hour, we can assume that holding the injectors open for say a tenth of an hour will result in a tenth of the fuel. The same thing happens when you hold it open for fractions of a second.
Here's your pulse width, or the easier way to refer to it - the short window of time where the injector is open.. the width of the window where the ECM sends a "pulse" to the injector to open.

Remember that this happens every (other!?) revolution of the engine, and hence that an engine rotating at 6000 rev per min (= 100 rev per sec) will only leave 1/100 seconds (10ms) per revolution for this window at max! This is also where the Duty Cycle comes in, expressing the ratio of time that the injector is open (PW) to the maximum possible opening time due to the engine speed. 50% means your injectors are only open during half of this window.

Furthermore, the injector offsets which we've been looking at, compensate for the time needed for the injector to open and close, because it is a mechanical device. It will take some time for the electromagnetic actuator to energize and lift the pintle of the seat (injector opening process). If you go back to kevm's post, he stated that e.g. an extra 400usec (400 microseconds, 0.4 millisec or 0.0004 seconds) are needed for this. When you have a PW (pulse width, time of injector opened) of 1.2 msec (1200usec), this is quite a big influence (33% difference). At 6 msec PW, 400usec are not quite as critical (6.7%).

By the way the opening injector pintle is also acting against the prevailing fuel pressure, that's why the injector offsets need changing by quite some amount when you raise fuel pressure.

HTH and that i got it right lol

Thank you for that very informative post I'm seeing things a little more clearly now. So based on what you said I don't know if you looked at my screen shots in my previous posts but I originally doubled my injector correction offsets when I setup my first bin a year ago. Others have mentioned that maybe to much, would this be because even though I'm running 80lb injectors I only actually increased my fuel pressure 2 psi over stock. I'm assuming PW is more relative to fuel pressure then it is actual injector size. Now after knowing all of this is there more accurate way to determine what my tables need to be based off of a calculation I could do or is it more of a trial and error thing?

Port fuel injectors I believe are published. I recetly bought them (24lbs) and they came with the needed offsets. I think there were like 6-8 differing values that a tuner might use. TB injectors I dont believe were published. I think RBob once calcuated voltage based offsets and are in a thread here some where.

I posted thread some time back where several of us commented. Also tips are given as to what to look for that would indicate when offsets need to be changed. I run my 75 lbs injs at 21 lbs fuel pressure. I believe my offsets are about right. I could post them for review.

U remember the name of thread ? Or is it in this one somewhere ? I run 68#'s @ 30psi with aeromotive 13301 vrfpr

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

Advance search Ronny as starter of thread and offsets as key word. There are a few that come up. Most recent one may be the best.

i'll give it a try to dig it up.. also yeah most port fuel injectors have data from the manufacturer available, with factors to scale the offsets with fuel pressure and voltage and all that. btw, what are 75# injectors?

@whatif, glad it helped let me recommend reading (at least) these two links to you from rbob's site, i find they help quite some to get your head wrapped around the basics and then some
http://dynamicefi.com/Tune_Intro.php
http://dynamicefi.com/Tune_Intro2.php
on the offsets, yeah as you said basically you're not that far off from stock pressure (although service range is 9-13). if you talked setting the offsets over with rbob, i'd be pretty sure they are correct, but might wanna shoot him email again with your VE table and the offsets and doublecheck.. or he might chime in here soon anyways

edit: did some digging with the search function but couldn't come up with something definite.. not sure if this link to the search results is working, but here's also the keywords i used:
Search: Keyword(s): tbi, injector, offset, 75 ; Posts Made By: Ronny

hey i just looked at the #80 @22psi injector offsets in provided calibration 3001... they are lower than the ones you posted, whatif! so i'd guess it's safe to say the ones you are running are too high! at 14.4V, 3001.bin shows 778usec, yours 793usec.

I have read all of the tuning intros top to bottom well atleast the 2nd one multiple times in the past year as well as read through this entire thread twice. It takes awhile to sink in I've always been a hands on need to see it for myself type person before I completely understand. And as far as the offsets I've been comparing some of the bins including the one you mentioned and yes my offsets do seem pretty far off. The past 2 days I've been busy getting some things squared away on my truck so I havnt had a chance to try out any changes yet I probably will today. I'm going to try changing them back to the stock 5.7 bin and maybe increase them 25% but previously I had actually doubled them haha.

GM 17112560 . I believe it is commonly called a 80 lb injector but I think RBob flowed it at 75 at 12 lbs FP. He posted that many years back i recall. I went with it.

Not sure on this but if the offsets/compensation are off the integrator seems to be moving excessivly.

Ownor do you recall what may be the minimum usec the injector can pulse assuming my injector at 21 lbs FP? I am seeing 1.6 steady at idle and in DE I can't get it under 13.5/1 (20MAP) even though my VE has very small values in 20 MAP cells. I idle OL and see 14.3-15.0 on WB at 750 rpms 45 MAP.

Yeah, sure didnt mean it in an offensive way when posting those links, I know these things take time to sink in just as you say
Maybe starting out from a 5.7 bin is a good idea, although I'm not sure how much more offset the #80 injectors would need even at stock pressure compared to smaller 350 injectors.. This post suggests there isn't much difference between SBC and BBC injectors, so you might get away just fine by multiplying in accordance with the mild increase in fuel pressure for your setup.

Ronny: damnit, i just got a pair of these.. So they are 75 huh? Interesting..
I don't have a definite answer for your question, sorry, but would be interesting for me as well. Hmm, seeing 1.6 msec in WUD? That includes the offsets.. So guessing real PW should be somewhere like 800 usec with that injector and FP, idle is stable at that PW? Not sure but you _could_ go async for DE maybe..?

No offense taken that really is the best way only way to understand this stuff for a DIY is constant reading and just playing with changes to learn what works through experience. I knew when I was getting into this it would be a huge challenge but from all the knowledge I've gained its been well worth the trouble. And now after discussing all of this stuff involving the PW and injector offsets I can completely understand why my VE tables look so strange to people. I'll be reporting back with my results at some point this weekend after I get a good amount of learns done. I'm planning on increasing the offsets slightly more then stock and replacing my VE tables with the stock ones and starting over.

Just got back from taking a 30 min drive with the new changes and wow what a difference. I swapped in some stock 5.7 tbi VE tables and changed the injector correction offsets back to stock and then increased them 25% to try and compensate for the slight fuel pressure increase. I still need to do a lot more driving to finish the tables, alot of spots are left to be learned in but WOW what a huge difference. Although it was pig rich from the new stock VE tables it started and idled perfectly and ran and drove so much smoother. The throttle response seemed way better it was alot snappier and it idles a ton better now it just no longer sounds like it has a cam in it haha. Once I get the tables finished I'll post a before and after if anyones interested in the results.

I would be interested in the difference in tables after you finished the learns. I've alway thought my inj offsets might be off on my setup. (36lb injectors). Would be interesting to see if your before be tables look like mine do.

Guys, stock LB9 bin has IAC - Gain set to 12.55% in both Park and Gear. IAC reaction is too slow in my case with my mods, so as a general rule we normally bump it up in 25% increments until it becomes unstable, then back it off a few until stable again. Now, in terms of Idle - Gain Breakpoints, the stock LB9 bin embellishes 50.00 RPM (High) and 37.50 RPM (Low), what would you recommend the offset/relation be with the change made to the IAC - Gain, say if my IAC - Gain values are now reading closer to 30%, and do the IAC - Gain Breakpoints need to be changed at all. Please elaborate on why you think they do, or why you think they don't. You will be graded...

Edit: 30% of 12.55, meaning 3.765% more totaling 16.32% in Park and Gear...

Just FYI.....

The injector offset compensations wash out the *mechanical* delays involved in the inertia of the parts. ( and the current bucking characteristic of the inductance of the electromagnetic armature ) The real time it takes to open the pintel from some percentage of open to some other percentage of open, and vice versa on closing. Note that it's not from fully closed to fully open !

My best advice on those, would be to find a stock bin from anything that used the injectors you have, copy those, and leave them alone !
When I went from 12PSI fuel pressure to 23PSI I didn't touch them. Why ? Because 11PSI change is not enough to affect it in any meaningful way.
Based on the area differential, and therefore the pintel pressure differential vs. magnetic force, I'd be a little surprised if 50PSI change made much difference, if any.

It's real easy to "correct" A when A was fine, but B needed a tweek. If one does correct A, then both A and B are wrong, and things will get real complicated real fast.
Take it for what it's worth.

Cflick, i don't think i have any data to back this up, but when I went from stock pressure with an old TBI pump to somewhere like 15-18 psi TPI pump fed on the stock L03 injectors, before tweaking the injector offsets i would run into the bathtub phenomenom. also, FWIW.. but from what most of us are experiencing and doing, i think there's indeed some influence on injector offsets from pressure change as well.

I agree .. My ve table was all kinda wavy n im at 30psi

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

Having a problem ... I've noticed since I went closed loop my AFR always stay around 14-15 even if its in pe mode at 30% throttle or 100% wtf ? Thanks

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

Does the light come on in WU? Same for analysis is PE then checked?

In the datalogs its showing pe active

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

I switched it back to closed loop to cwhat happens

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

Ownor,

I would agree w Cflick. I wouldn't play w IB to compensate for increased FP.
IB is a primary parameter which helps form the basis for fueling calcs. It needs to be accurate. Increasing the FP affects the calc'd BPC. That needs to be altered to accurately reflect the current situation.

Is this the commanded AFR or a WB reported AFR value? Make sure that when in PE mode the commanded AFR is in the 12.8-1 region.

RBob.

I prefer closer to 12.0:1 on E10, but he may be referring to reported, in which case maybe there's an issue with the sensor/controller.

Did you gorilla tape the FPG to windshield (with passanger monitoring) and do a PE run?

Yes reported is always 14-15:1 commanded is 12.4-12.8 in pe

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

Need to increase the VE in those areas when in PE mode. If that doesn't lower the AFR during PE then look for falling fuel pressure.

RBob.

here is a compressed zipped datalog csv file go down to about 7:20 runtime

thanks for any help I wanna go to the track tonight n need HELP I need some good times out this thing tonight!

You are taking a chance running full 1/4's with this set up.

If the column PSI_1 is fuel pressure there is a problem with it. From record 6645 through 6692, WOT, the MAP is about 95 KPa. Yet the fuel pressure (PSI_1) fluctuates between 21 and 30 psi.

However, I also graphed the PSI_1 after the above area when in decel. Records 6715 through 6765, it too is showing large fluctuations in fuel pressure. Between 13 and 25 psi.

Either there is really something wrong with the fuel delivery, or the pressure sensor isn't right.

RBob.

I c this ... Idk how the FP could change that much in split seconds ? Weird ... IMA go check it out

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

I am becoming stumped with my idle. It will idle like a charm just sitting with no AC and fan not kicked on. Turn the AC on and it bogs and drops then comes back up to commanded idle with AC. Of course the fan turns on at the same time the way mines set up. I have a Taurus fan I just installed today and it is wired to the high speed. I will be changing that to low speed with high speed on a manual switch. When I am driving around fan/ac on, the car doesnt go straight to idle when I push the clutch in. It drops below idle then sometimes comes back up straight to commanded idle or it will swing up and down. Also, possibly the most annoying, when I am sitting still or driving slow speeds and turn the steering wheel the idle drops down and then comes back up.

I have a datalog showing the idle doing this. This is with no AC. Fan on but was the original single fan not the Taurus Fan. All I was doing was sitting in the drive and turning the wheel clock to clock with a pause to let the idle go back to normal between turns.

idle bog.txt

You can see the MAP go up. The Spark Advance raises some as the rpms go down. Along with a slight increase in the IAC steps. Any suggestions? To low of an idle for the cam?

Could me splitting the sender wire cause this reading ? I split the wire from the transducer and ran one to the pilliar gauge and one to the ebl .. Also I'm running NO filter on the ADC channel preferences on both the WB & FP

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

Shouldn't be an issue with splitting the signal. Although the pressure sensor ground should be to the engine block.

The other thing to do is to place a small orifice in the line or fitting at the sensor inlet. I use a 1/32" (0.032") restriction to help dampen fuel pressures pulses. Usually use a piece of brass or aluminum about 3/16" long, drill the .032" hole and press it into the fitting.

RBob.

What you are seeing is somewhat normal. Even though CompCams states "strong idle", I guess that is relative. An idle RPM of 800 may be a bit low for that cam. Try an 850 RPM idle speed on a warm engine.

There is also IAC bumps available for when the A/C and the fan turns on:

IAC - A/C on Bump Steps
IAC - Fan on Bump Steps

They can help prevent the RPM from dipping too low.

RBob.

RBob,

It has been a while since I looked through the EBL calibration. Does the EBL have IAC based AE compensation that is adjustable like some GM calibrations. I found years ago if the IAC opened and the MAP increased, sometimes the MAP increase would not trigger a delta MAP AE change and the engine would momentarily go lean and cause a stumble.

The EBL systems do have IAC AE when opening:

AE - IAC Opening Fuel

Mostly used for TBI sets ups (wet flow), but I've been known to use a small amount on port injection set ups.

RBob.

How do.I scale the whole Ve table down ?y idle/ low loss numbers are,low.30's and top end ve is close to 100 with a few cells.at 100

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

Reduce the VE table(s) by 10% and increase the BPC vs VAC table by 10%.

RBob.

RBob,

Just curious, but if Injector Opening time increases w FP, how does EBL, or any other system, modify the Injector Bias to account for that when using a VAFPR? Does it need to given that higher FP is occurring where IB is not as great a factor?

Yeah, I'd think you would deal with the IB as a function of two things: lowest fuel pressure with the vAFPR (low map = low PW = high IB influence) and, I think this is more fool-proof, just a judgment on the shape of the VE table. Bathtub isn't right (not enough IB) and unrealistically low VE on low map isn't right either (too much IB).

Well I did this except went with 15% and still ran into ve overflow @ 2000rpm 90 map wtf ! Idk what is going on I haven't physically changed anything on the car but the air filter ...and I played with the tune the other night but I was pretty wasted :-/ idk what I did ....

I added a filter to the ebl preferences for my fuel pressure and it no longer jumps around like it did stays within 1.5psi or so

Also fixed a fuel line problem I've had since day one so that may gave helped the FP stability too

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

Can u go into a little more detail about IB and VRFPR ? Thanks

91' bird 305 TBI T-5, trick flow 175 cc heads, 4.10 gears, lots of suspension upgrades......... 24mpg @ 2300rpm hwy 65mph ........ 8.63@ 85mph 1/8th on street tires... 8.000's soon

This is from DynamicEFI site:

Injector Compensations:

The purpose of injector compensation is to make up for the time it takes for an injector to open and then close. The proper values can be difficult to obtain, so many times they are guessed at based on results. Which in many cases works out OK.

In general terms the higher the fuel pressure the longer it takes for an injector to open. Increased fuel pressures are more prevalent on TBI systems. And as such should have the injector compensation values increased. Check the 5.4l calibration with the 80# injectors at 22 psi. Compare those values with some stock calibrations. That will give an idea of what values can be used.

With port injectors there is some information available for various injectors. If available then it is worth using to update the calibration.

My first question becomes what's the duty cycle on the injectors ?