2xLS1

iTrader: (25)

I'm just saying that when you are tuning that car with 70K miles on it, you don't really know what those stock 70K mile injectors are actually flowing, do you? All you know is what they are supposed to be flowing. What you are calling pushing around the IFR table might just be getting it closer to reality for those injectors.

WeathermanShawn

iTrader: (1)

Frost, you made some good points that clarified the perils of 'unilateral' IFR tuning for Trims.

I see the other poster's point. I am not sure he would disagree about altering IFR just for the purpose of Trim tuning.

So I take it you prescribe getting Trims +-0? Is it always an airflow problem when your Trims are not equaled? I.E., ever a case to leave stock IFR, stock MAF calibrations, and leave Trims alone.

Probably would not make sense for PE fueling, but just curious as to your viewpoint.

..WeathermanShawn..

Frost

iTrader: (45)

I hear ya there and don't dispute flow variations at all, but... Even if they have time and wear and you flow them and get your average you should still be using Bernoulli's equation [simplified to: static pressure + dynamic pressure = total pressure] or some approximation (there are spreadsheets floating around that use this method or mimic it well enough) to find the slope against manifold pressure, and that will *NEVER* produce an IFR that looks like this, which is unrealistic and comes from IFR "tuning":


That image, is a file from user on here's supercharged, stock bottom end car at about 9psi and was done by a very popular and well known shop. The car started and ran like butt and went dangerously lean up top. The MAF maxed and the AFR at WOT would vary with outside temperature. Heck that PE table may not have been unreasonable if not for the stock VE and MAF table that the car had. It does not lean out in the cold at WOT or fatten up in the opposite season now that it has has been retuned in 2bar speed density.

joecar

One example:

The PCM computes cylinder airmass from MAF and/or VE, and uses it for looking up the spark timing table...

If airmass was not "true" (due to the IFR being tweaked instead to correct trims), then the spark table lookup is wrong...


Another example:

The PCM computes cylinder airmass, determines commanded AFR, calculates required fuelmass, looks up IFR to calculate injector pulse width to deliver that fuelmass to give that AFR...

if any of MAF/VE/IFR is "wrong" (not modeling actual conditions), then the actual AFR will be wrong... it may be spot on under one particular condition, but it will be off everywhere else.

----

Sure, IFR does not account for injector wear/deposits over time... this is where scheduled maintenance should include on-vehicle cleaning... (I believe wear has very minimal impact, but don't quote me on that...)

But don't assume GM has correctly programmed the IFR for each vehicle.

Mike454SS

iTrader: (4)

Closed loop has nothing to do with wether or not you're running speed density. My car runs closed loop speed density. The misconception on this forum is that speed density requires open loop...which is not the case. A LOT of people ARE running open loop speed density, and a LOT of people are running open loop with the MAF...the narrow band O2 sensors are what create closed loop functionality though, and they function in MAF or Speed Density mode.

In regards to modding the IFR table when injectors are old...I don't think thats a good idea at all. In my opinion, before tuning a vehicle, everything should be in good working order. If the injectors are not flowing like they're new, then I feel they absolutely should be removed, sent out for proper cleaning, then reinstalled...if you want to tune with the MAF and it's not reading what it should be reading, same thing, it should be cleaned or replaced if cleaning doesn't cure it, if your O2's are old and switching slow do you change the closed loop mode values or do you replace the O2's? I replace the O2's.

Mike454SS

iTrader: (4)

The IFR differences in each vehicle could also be due to different fuel systems other than just the injectors...variances in fuel pressure can affect how the injectors react to variances in manifold pressure...you need to remember the total pressure differential across the injector (it's just like a resistor in an electrical circuit...how much fuel or current flowing through it is directly related to the pressure across it)...so that could also be why the IFR tables in the 01-04 vettes are different than the 01-02 f-body's, I'm going to research that more tonight.

Steve (Frost), that tune is HORRIBLE. I'm glad you fixed it for them...I actually laughed a little when I saw the graph of IFR...I say to just say no to IFR AND MAF table raping...if you want to run a MAF, thats great, run the correct calibration for that MAF in that intake stream.

2xLS1

iTrader: (25)

Maybe 1 in 10 people that bring me a car to tune can even tell me when the last time the fuel filter was changed, or when their K&N was cleaned last, or if their MAF has ever been cleaned. The typical car I see is one that has been driven around as a daily driver with no maintenance other than oil changes for many years, then they throw a big cam and springs in it and then say tune it. Maybe it's different with the cars you see. And I could even show you worse tunes than that. This is from a well known shop in Texas.

WeathermanShawn

iTrader: (1)

Mike454SS thanks for the clarification of closed-loop vs open loop. You are right, I failed to state it correctly.

Interesting choice running closed-loop speed density. You are right, the common assumption is one runs SD or MAF open-loop to bypass feedback from the O2 sensors. How has that approach worked for you?

Joecar, I think your explanation was spot on. I take it that under that premise that if VE/MAF/IFR is absolutely correct, your Trims will be near zero.

Where I am having the conceptual problem is if you make one unilateral IFR change, or one uni-MAF change to 'tune' out trims, is there really a difference?

Not being lazy, just find it tedious to work with various MAF HZ Freq, and comparing againt dynamic aiflow. I have found even that changes depending on what gear you are in, load etc.

Likewise I have found just 'jacking' the IFR to tune trims, does leave the car a little 'boggy' (more fuel in my case), and too rich at idle and lower rpms.

Having stock injectors, stock MAF..car runs great just leaving those tables stock. It is just the +Trims and resulting PE inaccuracies that makes this an issue.

Is the bottom line, you have to get the airmass calculation right at every point in an engines operrating zone, or you have a car that is not performing at its best? Again, not being lazy..just curious if anyone has come up with any new insights to make AFR tuning a little less tedious for the masses.

Thanks.

..WeathermanShawn..

Frost

iTrader: (45)

Trims should be close, but unless the cars are race cars (never HAD to tune a street car in OL and leave it that way), I usually tune the SD cars in CLSD with LTFTs disabled (well I don't tune them in CL, I set leave them that way when finished) .


Mike, with regard to your MAF statements, where would you find cals for all of the different intake arrangements that these cars run from the aftermarket ? Simply re-clocking the MAF in the piping alone will change it's reporting significantly. Also, the MAF is not the precision sensor that many believe it to be. Take 3 stock MAFs, swap them one at a time on a car on the dyno and run them around a bit in OL and check out the difference in airflow that they report (and your subsequent AFR error); you'd be surprised how differently they will all respond even with the same base tables.

2xLS1

iTrader: (25)

But the precision of the injectors that the OEMs throw in these cars by the millions are? And then add some age to them. That's the only point I'm trying to make here. Some would consider changing the value .01 in the IFR table from what it [I]should[I] be is hacking a tune.

Mike454SS

iTrader: (4)

The major differences I've seen are for an intake path similar to an F-Body or vette where the MAF is right in front of the TB, versus a truck, where it's off to the side with an elbow between it and the TB. I agree with you, they do have differences sensor to sensor, but the standard deviation in how 1000 MAF sensors read, and how 1000 sets of the same injectors flow, is not a big deal, and THAT is what the fuel trims are for. If every sensor and injector was the same (not necessarilly reporting correctly, but at least the same), we wouldn't need closed loop and we wouldn't even have O2 sensors in the first place...narrow band or wideband.

Mike454SS

iTrader: (4)

It's worked out great, unlike Steve I choose to leave LTFT enabled...though I also work to get the tune so close that the LTFT's rarely ever deviate from 0. The car drives great in any weather...I hop in, turn the key and go, I only re-tune it when I change it.

Changing the IFR table to get the fuel trims back in check doesn't work for a lot of reasons...for starters, it's a table based only on KPA, and has nothing to do with RPM. The VE of an engine at 80 KPA at 2000 RPM is very different than it is at 3000 RPM and so on...thus affecting fuel differently at different RPM's and the same KPA.

Also, spark advance in these PCM's is determined in a lookup table based on the airmass calculation. The MAF and VE tables are how the PCM determines what that airmass is. If the VE tables are reporting airmass incorrectly then the spark advance is incorrect as well, this can result in anything from knock, to a spongy non-responsive feel when you hit the throttle...to occassionally getting it correct in random load/rpm situations rather than proper tuning getting it correct all the time.

Frost

iTrader: (45)

Like I said, I'm with ya I called IFR raping pushing the table around in one place or another to affect trimming in certain areas rather than VE/MAF work.


Back to the MAF thing... here's a little further understatement for the fact that it's table must change when the intake tract, even before the MAF, changes. A friend of mine put his car back to stock to sell ti and had me retune it. Before he sold it, he took the last mod off; the air lid. Years ago, when he got the car, the lid made 8rwhp by itself. Now, when removing the aftermarket lid and putting the stock lid back on (and losing the 8 hp) the trims went from -1, -2 to +9 all over the place in cruise. If this were taken at face value, the car now needs more than 10% more fuel in cruise areas with a stock lid?? No, we changed the path of airflow THROUGH the MAF, so the value reported by it changed as well. If the MAF cals ARE good from the factory, why don't you get what you command in PE at WOT with a stock curve... EVER? I'm not trying to tell anyone 'the way' to tune, but if you leave the MAF table stock and the car has a MAF in use, there is no way to hit commanded fueling.

Ralls

iTrader: (32)

Could you tell me who is doing those tunes? I'd like to avoid them because I'll most likely have to come down south for my SD tune since there is no one around here.

12secSS

iTrader: (30)

All of this is close enough, you will drive yourself crazy trying to get it dead nuts on. It will never happen. Being .01 on the IFR scale is not an issue to me, but if you have 30lbs injectors and you IFR table looks like a roller coaster or shows the injectors flow 46lbs, then that is rapping. As for scaling the injector constant up or down for the fuel trims, because the injectors are old ... I wouldn't recommend it either. Either do as mentioned above (have them cleaned and flowed), or just leave the table alone. If they are used ones swapped in, unless you know the actual flow, just go with the advertised flow.

I will say this, there are instances where you need to fudge the tune to get results. Like at work, we can not touch the VE table in order to have emission certification. That is just a given that we work around, it is not my chosen way though, but when your hands are tided you do what you can to escape. But each method of tuning has it's place. If you do not have such restriction, why not model the airflow closer to reality.

BlackNiteWS6

iTrader: (2)

Funny i never had any issues tuning using the IFR to fine tune the amount of
fuel that was needed. And back in the day this way of tuning was the preferred method for adjusting LTFT's at part throttle period and PE was for WOT tuning. I didn't invent this method. It was how guys were tuning before i even bought LS1-Edit, which was the only PC based software out in 2001. So don't tell me that this method is wrong since there were tons of guys already doing it and were going fast so when it came time for me to tune for my mods i followed the IFR method. I remember one example of a guy that did it and was a tuning guru. His screen name was NoGo. And like i stated it was so easy to tune with that method. And i know theres no way in hell that my car would have went any faster using any other method. It only had the old lobe design Comp. 216/220 .525/.532 114lsa cam, i only had my 241's just cleaned up to remove the casting flash in the runners and the chambers. The only real work done to the heads was the throat and bowls were blended and only flowed like 255 to 260 cfm tops. My heads even still had the bump in the intake runners. Plus it was full weight with still running the 2002 heavy *** WS6 rims I wanted the older version but in '02 they weren't offered and they were noticelly heavier. And after doing searching on here lately i don't see other running any faster than my car with the same setup. And they are using as you say " the correct way " of tuning. Bottom line theres more than one way to skin a cat and if one method works then who are you and the ******* that has the ***** to call me a dumbass that if a certain tuning method works deal with it!!! Tuning is one of those things that was different ways of getting the job done. BTW, i had Geoff from Thunder Racing and Craig Gallant from GTP who ports heads both were surprised that i ran the times that i did based on my setup and my cars weight. So i guess they are wrong as well since at the time they tuned cars the way i tuned mine?? Yeah right!! God himself wouldn't have gotten anymore power or more importantly lower my ET's since my heads and cams weren't picked out to be insane. I just wanted a nice little torquey setup that was a blast on the street, which it was bottom line so i could care less about comments, bottom line the way i tuned obviously worked when i did it back in 2002. Today i probably would tune differently since the head and cam technology got so much better than back in 2001 and 2002. So flame away i couldn;t give a rats ***...i was more than happy with my WS6 I never understood how or why certain people need to talk **** about someones setup just so they make themselves think they are smarter or whatever. It actually makes you people look either jealous or come off as just a big mouth that thinks they know it all and doesn't offer anything positive

BlackNiteWS6

iTrader: (2)

Thank you a guy with common sense. You're right certain tuning methods have their own place and as long as a method works who's to say that you are automatically wrong cause you don't tune the same way they did

BlackNiteWS6

iTrader: (2)

What are you an 18 year old idiot that just repeats what someone told you or
something that you over heard. Your intire post is retarded i helped out on my heads when they were ported. I lapped the valves in myself, do you even know what that even means..lol. I doubt it I also did my own install on my setup after the heads were ready. I tuned it on the street, not the dyno, since dyno numbers mean nothing. But i always wondered what the dyno would have showed, but i dont care. Dynos should only be used get the A/F correct. But there still is a difference since a dyno cant totally simulate what the car will see when running on the street or track. And you are again showing how rediculous you are by stating that your car would beat mine after your turbo is installed...DO YA THINK?? man i know i'm shaking in my shoes You are compairing a small head/cam package over a FI setup...lol. You're a hell of a guy...ha!! I guess i'll now have to have a 427 build and bolt on my D1SC kit which i already own....but man i hope your turbo setup will out run my small street setup so you can feel like a tough guy or whatever....dumdumdum.

Mike454SS

iTrader: (4)

Alright I'm with you...find the stock tables from an intake that most closely mimics your intake...then fine tune the MAF to that intake path...hows that . Similar to the IFR table, the MAF curve should have a very specific shape to it...if you are fine tuning it and finding that the shape of that curve no longer looks anything like the stock one...something else probably needs to be changed.

12secSS...I wasn't aware you'd fail an emissions test if the VE table wasn't stock...is this just a Cali thing...or is it just to be able to be an emissions certified tuning shop? (ie would the car still pass the plug in but you guys would be in trouble if someone pulled the flash out and checked it?)

Back to the C5 and F-body having the same injectors and different IFR tables...the offset tables are different as well...maybe they just had different teams calibrating the injectors?

Do any of you guys ever touch the offset tables at all when switching style of injector (like from a pintle to a disc)?

Mike454SS

iTrader: (4)

BlackNiteWS6...will you please calm down a bit? If you want to argue who's car is faster with the other guy, please by all means PM him. The rest of us are trying to not be insulting to anyone, and I think we're all learning quite a bit from each other too.