IFR Table Scaling

[dmtnt]

Ok, so I scaled my IFR table by 90% and got my average LTFT's from ~13 down to ~4. I'm going to try scaling the original table by 85% now. Sound OK? My only mod so far is an aftermarket air intake (Vararam). I had read elsewhere that I should really focus on cells 6-14. Comments?

Sorry for the :newbie: question, just figured I'd ask before messing something up. :D

[JandJsTA]

You are correct Sir ... once the LTFTs are set then you can go on with your WOT logging to see where you are with A/F remembering that a wide band dyno or an a/f meter is truly the safest and most accurate way to do this :)

[smiley]

sounds good so far :thumbup:

[dmtnt]

Thanks, guys! :2thumbs:

[ulllose]

here's a ?? By scaling down the IFR table effect how the car acts a WOT? The reason i ask was that if i start messing with my ltft to get them alittle lower,,,,,mind you i have had the car tuned on a widebnd already so i don't want to mess wot up.

No what i mean..

[smiley]

during wot - the pcm does not waste time computing all values.

if your ltrims are negative or zero when you hit wot - they will stay locked at zero during wot.

if they are positive - the pcm thinks there is a lean condition so it is dumping in extra fuel. it continues this during wot because lean = bad. so if you have positive ltrims when you hit wot - the pcm will keep it at that number.

that is why you must tune your ltrims BEFORE you tune wot.


ulllose - who tuned your car for you? you seem to have many questions tonight ;)

[JandJsTA]

Smiley :thumbup: ... ulllose , I sure hope someone didn't tune your WOT A/F without first checking/correcting the LTFTs if they needed it .. because it is almost impossible to get that done with any accuracy if the LTFTs are adding fuel to the WOT mix (+ LTFTs) .. as Smiley says you need to get the cruise/base LTFTs in check BEFORE going to WOT ... if you do it backwards those changes will have an effect on your WOT A/F and you will have to revisit the PE A/F twice to get it right :(

[dmtnt]

Okay, I loaded the tune w/ the IFR table at 85% of original and drove to work this morning. I know you're supposed to wait 100 miles or so for the computer to relearn, but this morning the car was acting weird. It had a slightly different sound to it, kind of "flat" if you know what I mean. I had to hit WOT at one point to get around an idiot on the highway and it broke up a tiny bit after 6k rpms. :( This was only after about 30 miles since loading the tune. Took it out at lunch time for a quick spin and it seems a bit better, but I'll log some data after hitting 100 miles. Does this sound normal? Maybe I scaled the table too far?? Thanks guys. :D

[JandJsTA]

Originally posted by dmtnt
Okay, I loaded the tune w/ the IFR table at 85% of original and drove to work this morning. I know you're supposed to wait 100 miles or so for the computer to relearn, but this morning the car was acting weird. It had a slightly different sound to it, kind of "flat" if you know what I mean. I had to hit WOT at one point to get around an idiot on the highway and it broke up a tiny bit after 6k rpms. :( This was only after about 30 miles since loading the tune. Took it out at lunch time for a quick spin and it seems a bit better, but I'll log some data after hitting 100 miles. Does this sound normal? Maybe I scaled the table too far?? Thanks guys. :D

If you were adding fuel at WOT with the LTFTs (+) and now you have it corrected you may very well be running lean now at WOT .... you need to log some WOT data and take it easy until you do just in case you are running WAY lean...... can you hear any audible PING :confused:

[dmtnt]

Originally posted by JandJsTA
you need to log some WOT data and take it easy until you do just in case you are running WAY lean...... can you hear any audible PING :confused:

By the time I get home tonight it will have about 90 miles on the tune so I'll start logging then. No audible ping. Now I need to read up on WOT tuning. :D PE vs RPM table, right??

[smiley]

[qutoe]I had to hit WOT at one point to get around an idiot on the highway and it broke up a tiny bit after 6k rpms. [/quote]

do not do that. you are messing with your car - don't do things until you know how the car is running! :eek:

By the time I get home tonight it will have about 90 miles on the tune so I'll start logging then. No audible ping.

you can log now just so you can watch the pcm start to relearn - plus if something is way out of whack you will know.

keep in mind - 100 miles, drving cycles, what ever methode you use - you have to do the correct tpye of driving. if you put 100 freeway miles on you have just wasted 95% of your time. you must give the pcm time to relearn all timing and fuel curves by giving it time in as many modes of operation as possible. cruising on the freeway will not do it. (remember to be careful about wot until you know what's going on).

hell after my cam i was afraid to push the gas down for a long time ;) better safe than sorry. especially when you are new to tuning. small steps with tuning changes - and small steps when driving after those changes.

Now I need to read up on WOT tuning. PE vs RPM table, right??

yep.

[dmtnt]

Originally posted by smiley
keep in mind - 100 miles, drving cycles, what ever methode you use - you have to do the correct tpye of driving. if you put 100 freeway miles on you have just wasted 95% of your time. [/B]

Yep, I knew this. ;) Pretty heavy traffic to/from work with a good 10 miles of the commute residential. I've tried to change gears and vary the RPM's alot so as to try and hit all the cells. Thanks again for the help! :D

[jimmyblue]

Just a question, but what do you suppose caused
the degree of lean error you are trying to correct?
>15% off from the factory? Unlikely. The Vararam (?)
is really the only non-stock mod?

Because if it's not really a fuel delivery source of
error you're fixing, then there's probably something
more appropriate than the IFR table to represent
it. It doesn't seem from reading this that a clear
culprit is identified.

But let me ask you this - have you been running
around for many miles on the oiled-foam-filter
version of the Vararam?

Johnny, what do we have for our contestant?

Why, it's a brand new, General Motors K&N Filter
Technical Service Bulletin! And it's fun for the whole
family!

[JandJsTA]

Goint point Jimmy...... may be time to check the MAF wires for a wax buildup ;)

[dmtnt]

Originally posted by jimmyblue
Just a question, but what do you suppose caused
the degree of lean error you are trying to correct?
>15% off from the factory? Unlikely. The Vararam (?)
is really the only non-stock mod?

Because if it's not really a fuel delivery source of
error you're fixing, then there's probably something
more appropriate than the IFR table to represent
it. It doesn't seem from reading this that a clear
culprit is identified.

But let me ask you this - have you been running
around for many miles on the oiled-foam-filter
version of the Vararam?

Jimmy, I've been wondering the same thing. Unfortunately, I never logged data prior to installing the intake. :rolleyes: I've got about 400-500 miles on the car since the new intake. I checked the filter the night before last to see if it had shifted or something, possibly causing unfiltered air in. All was good. The backside of the filter was dry. I made sure it wasn't over-oiled when I installed it. I will pull off the MAF tonight and check the wires (yes, I saw the GM bulletin). If there's oil buildup, I can clean them with electronics cleaner, correct?

FYI, I logged more data last night and with an 85% reduction in IFR, I have most of the LTRIM's negative. They lock at 0 on WOT (although I didn't have a chance to make more than 2 runs). A couple of cells are still + (cells 2 & 3 with an occasional + entry in other cells 6, 10, 13 & 21). O2's look got at WOT, averaging .884 and .889. No KR on the WOT runs at all. Car was running VERY strong last night!! :D :drive:

Edit: the Vararam is a pretty decent mod for the vette. Guys are cutting almost 1/2 second off 1/4 mi times and adding 5+ mph trap speeds with just this mod.

[ulllose]

smiley----

Took me awhile to read the post.
I had the car tuned by a guy that use work with Mallet Motorsports on tuning his 396 and 435 conversion packages
Believe it or not.
the car was tuned back in March of 2003. I drive the car minimal maybe 1000 miles last year ( Business owner/1 small kid) in other words not alot of time for me...... So he picked up 13 RWHP from my stock tune but thats it. He didn't do any logging or change much of anything else. At the Time i didn't know anything about edit,,so over the last year i started screwing around with it to correct my idle issues,,(very rough) and have learned alot but at the same time i need to learned alot more. I waiting to get me excel program (tomorrow) so i can export my logging but for now all i can do is just play it back and look at it. I have notice my bank1 and 2 are off from each other by 4.5% at all times,,so maybe i have an exhaust leak.......
Well from my dyno sheet 'm running around 12.9:1 @ WOT but i'm guessing everything else could be off.....
but the funny thing is the car runs great,,,except at idle.
Man my head hurts from this stuff.....

[ulllose]

Originally posted by JandJsTA
Smiley :thumbup: ... ulllose , I sure hope someone didn't tune your WOT A/F without first checking/correcting the LTFTs if they needed it .. because it is almost impossible to get that done with any accuracy if the LTFTs are adding fuel to the WOT mix (+ LTFTs) .. as Smiley says you need to get the cruise/base LTFTs in check BEFORE going to WOT ... if you do it backwards those changes will have an effect on your WOT A/F and you will have to revisit the PE A/F twice to get it right :(

jandjsta--

i,m kinda understanding,,,,question is when you say it is impossible to get that done with any accuracy-------wouldn't tuning on the wideband be as accurate as it gets,,,,at WOT?? Or are you saying every run would be different depending on what happened before WOT.

the guy that tuned it...looking back on his edit file he added 2* on the High octane spark advance between 0.56gms/cyl and down and from 2400 rpm and up,, but thats all he did for a/f ratio.

[smiley]

wouldn't tuning on the wideband be as accurate as it gets,,,,at WOT?? Or are you saying every run would be different depending on what happened before WOT.

correct. if your ltrims are positive - that number gets locked in for wot...... so it might be +1.2 one time, +5.6 the next time.... it will almost never be the same number. it will be whatever it last was before hitting wot. that means you'll be getting added fuel in the mix during wot... and it will always be a different amount. htat means no way to tune because it will be a different amount every time.

if your ltrims are negative (or zero) when you hit wot - they will get locked in at zero - meaning no fuel is being added or deleted during wot.

[JandJsTA]

Exactly ... but my theory as to why dyno tuners can get a car tuned with a graph that looks good each time when some of the LTFTs are + is how they dyno the car. Each time they ramp-up the RPMS almost identically so the PCM (in theory) is following the same FTC pattern each time before hittng WOT. But on the street as Smiley says you may hit WOT from a different fuel cell many times when going to WOT as you don't follw the same ramp-up to WOT, thus you need to be sure all LTFTs are - not just some or an average :)

That's why it is important to make sure the LTFTs are good before you go into a dyno session as sometimes tuners don't bother with LTFTs before they proceed :(

[smiley]

or just tune from the street since that is where you car is most of the time. yes - i got a dyno once and plan on heading back this summer now that i have tuned my cam and headers..... just hat just to put a number in my sig.

imo - dyno numbers are like post count. i could care less about tweaking my car so it is perfect on the dyno.... once i drive out of the shop.... that tune ain't perfect anymore.

[ulllose]

great info guys,,,,,
well back to the drawing board.......I do see how everyone is tuning by fuel cells and making adjustments in the IFR table but i don't see people tuning with timing (high octane spark advance).
Not saying this is wrong or right but adding timing to select areas of this table will make changes in the a/f ratio. I've also noticed that i'm running around 30* of timing during WOT runs,,,(that was bumped up by the tuner 2*) and other people are running 23-27* at wot. Is this a 1998 year thing with more timing in the higher rpm's? Like i said before it was only bumped up 2* from stock.

[smiley]

28 * is good for a '98... he bumped you up 2* so i'd say that is in line.

now i haven't tuned any timing on my car yet - so wait for joe to jump in here. i think you are ok bumping up a little as long as you don't get kr.

[ulllose]

Ya i have no KR. I'm just wondering why you would mess with the timing table if you have already adjusted your ifr table and your main VE. (to get correct a/f ratios). Like you for instance.
Thats all the tuner did on my car,,,so i think i will just keep his file for back-up and start doing some changes of my own to see if i can make it any better. You know whats really funny my car runs great except for idle issues,,,and all that was done was timing changes in certain areas,,,,now others are really making alot of changes across the board/individual cells/ifr/map/etc,etc, and really putting alot of work into the changes,,,,I'm going to be curious to see if i make all these changes if the car is going to run any better??Maybe everyone else is just doing overkill,,,maybe, maybe not. I hope these changes will help my car run better, but like i said it runs great now, except for idle,,so if i can fix my idle i will be extremely happy;)

[JandJsTA]

Originally posted by ulllose
great info guys,,,,,
well back to the drawing board.......I do see how everyone is tuning by fuel cells and making adjustments in the IFR table but i don't see people tuning with timing (high octane spark advance).
Not saying this is wrong or right but adding timing to select areas of this table will make changes in the a/f ratio. I've also noticed that i'm running around 30* of timing during WOT runs,,,(that was bumped up by the tuner 2*) and other people are running 23-27* at wot. Is this a 1998 year thing with more timing in the higher rpm's? Like i said before it was only bumped up 2* from stock.


Actually I believe most of the good tuners end up in the high octane table for the final tweaks to get the most out of your car, they set the A/F first and then polish up with timing in particular ranges as you describe :thumbup: at least the ones I've seen at Agostinos do it that way and they have put out some impressive cars/tunes :) That is the way I set mine up after viewing numerous dyno runs, just take it slow and easy and log your changes to be sure, once you start seeing KR take it back 1º at a time until the KR is gone. The only thing you can't do is tell what effect you're having on your A/F without the wideband when you are adjusting the timing table, IMO that's the only part that is really missing for the home tuner :( .. those LM-1 sniffers are some tempting :)

[ulllose]

Sure when he adjusted the high octane table i was on the wideband dyno,,,,,,so i will start from scratch make my adjustments and then revisit the dyno to see whats up. I getting alot of misfires while driving so i'm trying to figure that out right now...
:mad:

[smiley]

isn't that the old way of tuning? add timing until you get detonation or loss of power on the dyno... then back it down to the last spot?

[ulllose]

Originally posted by smiley
isn't that the old way of tuning? add timing until you get detonation or loss of power on the dyno... then back it down to the last spot?

Yes it is,, go advaced as possible until detonation and back up a degree or 2

But it still seems to work.

First dyno run with no tuning.......went from 12.4 at 3500rpms and dropped to 11.5 by 6100 rpms.

added 2* of timing in @ 2400-6600 rpms from 0.56gms/cyl up to 1 gms.cyl and A/F went 12.5 across that rpm range,,,,seemed simple enough.

But like i said before i do have + ltfts and i'm not sure what my
A/F ratio are really at in the real world. I have some logs from atap i will check my o2's