RAF tuning issue, hard light load bucking, any suggestions?

[CarsonTech]

Hey guys,

My head hurts like hell from work, and I am finding it hard to think. Sorry if everything is long winded…

My name is Andrew, and I am from Greenville, South Carolina. I am on my 3rd LS1 car and I am just getting into tuning. I am currently tuning my 99 Trans Am.

Could someone check out some of my tunes, logs, and methods? Maybe comment on them? Basically i want to see if I am headed in the right direction, and maybe get some help with some common problems.

I did have this posted in the Geting Started section, but decided to post this over here to see if it will get more publicity.


Sorry if I jump around, but I have a lot on my mind. I am tuning in SD mode and had some concerns. Here is some info that may help:

Mods:
230/236 .613/.601 112+3 Cam
Supporting valvetrain components (Double springs, 7.4 Hi-Tech pushrods, LS7 lifters, LS2 Timing chain)
LS6 Intake Manifold
30# SVO redtop injectors
Ported LS6 oil pump
Underdrive pulley
Pace Setter LongTube Headers
Pace Setter Offraod Y pipe
Magnaflow catback
3.90 rear gear

I am using an LM-2 Wideband through the EGR connector to log AFR.

I had my VE table below 4000 rpm pretty much dead on before the temperature change, and close at WOT at most RPMS as well. Last time I logged it was in the 60's, it was around 80 today.

Everything feels great about the car, idles good, starts up fine, feels strong how I have it now.

But, I have bucking at light throttle below 2000 RPM. Even when I had it with the professional tune loaded when they appeared to have only tuned the MAF.
Tuned by a Mustang shop in Pensacola, FL before I bought the car.
I will attach the “professional” tune as well.

I had lots of bucking on deceleration below 2000 RPM. Once I zeroed out the Throttle Cracker at 400 and 1000, and lowered the numbers in the 1600 column, and the rest, the deceleration bucking is almost completely gone except below 1500, but it’s a lot better.

The car Idles great when using the RAF that was in the "professional" tune. But when I use the RAF tuning histograms supplied on this forum, I get lower numbers in the warmer temps than I think should be there. The car doesn’t want to start up when warm and the idle dips with my RAF tuning. Again it seems fine with the "Professional Tuners" RAF table. I used RedHardSupra's MAF spreadsheet to calc my new RAF after each log.
I turned the LTITs off after a couple of logs and logged RAF a few more times.
I will post a bunch of Raf logs.

When i first got HP tuners and a wideband:
I changed my injector values to match the 30# SVO Red Top injectors, which was almost the right values from the "Tuner", but not quiet (According to the Spreadsheet floating around here).

I have tuned the VE table, eliminated some knock retard, tuned the VE table again, and so on. I have also been doing some MAF tuning along the way.

Tried to fix light throttle bucking by matching base and main spark advance tables under 2000 RPM at low throttle positions and blended them into the main timing table for smooth transaction. I redid my VE table again after this. Did not seem to help at all.

Also, I have a WOT run starting around frame 107060 in my most recent log,in the Recent Tunes and Logs of the zip file. I hope this helps...

Car put down 397hp and 370 tq with the tune that I logged recently.

Anyway, I have attached my Tunes, logs, and cfgs, in an organized fashion, inside a zip file. All, and any, comments welcome

Actually, here is a link to the zip file since ZIP files are not supported on this forum, right click and save as:

http://www.freewebs.com/carsontech/99TA.zip

[Cantalope Kid]

I am using an LM-2 Wideband through the EGR connector to log AFR.

Okay stop right there...you have over $1200+ in equipment hooked to your hearts passion (car) and you haven't had someone cut you a hole for a direct wideband hookup in your Y-pipe, $25 at best? Think about it! Sorry I just don't trust the accuracy of the whole EGR hookup.

[Sam88gta1]

Okay stop right there...you have over $1200+ in equipment hooked to your hearts passion (car) and you haven't had someone cut you a hole for a direct wideband hookup in your Y-pipe, $25 at best? Think about it! Sorry I just don't trust the accuracy of the whole EGR hookup.

He is hooked up to the EGR plug to log it through the scanner. He has a 02 sensor installed but my guess is he dont use a MPVI Pro cable with inputs.

[CarsonTech]

Yup, I do not own the professional interface. So I do not have the EIO hookups. I have the wideband sensor in the passenger side narrowband o2 bung.

I am upgrading to the pro interface is a couple of months and definatley having a separate bung for my wideband installed. Just have to wait until I close on a house and all the good stuff.

Anyway, lets say that my wideband reads are accurate, atleast for now.

I am going to mess with the timing in the areas where bucking is present, low load, low throttle position. I have done this before earlier this year and I remember the bucking almost disapeared when timing was about 24 degrees in that area. But when I tried this about month ago, the lowest timeing I went was about 27 degrees, and I sill had the bucking.

But in the logs I have, when the car bucked my AFR did not change much at all. The time timing doesn't change a single degree.

[CarsonTech]

Today I played around with timing for a few hours. I took the timing lower and lower in the areas that were bucking all the way to 24 dgrees, and it bucked just the same. even though the logs showed that it wasn't transitioning from the main tables the the base tables, I sparked matched in those areas as well. No dice.

So after doing a little research I decided to see if something funky was going on with my IAC, TC, TF, ect. My IAC count was not changing during the bucking. My airflow wasnt changing for TC airflow and TF airflow.

Assuming my wideband is accurate, 0 lag, ect, and that my VE table is tunned well... what other things are there to log that can help me track this low load, low throttle position bucking?

I only have 30# injectors, but I have been reading up about injector offset and pules. Everything I read only indicated that much bigger injectors only need these parameters changed. Is this true? If not, what should I change to test? Higher values, lower values?

I have also heard that running richer, like a 12.5 AFR, in the bucking area may help. I see where I can do this with the 1 Bar SD OS. I have read some people using the stock OS to do this with the PE mode. Any suggestions or recommendation for or against this?


Thanks!

[RoDan]

Which 30# injectors are you using? I'd say that it is unlikely you need to mess with the short pulse stuff the injectors that small. You could perhaps have error in the offset tables, but that is just guessing for the most part.

If I were you, I'd see if your throttle cracker stuff is dialed in and also take a look at your throttle follower tables. Most likely though it is fueling related, try upping your EQ ratio just in that small area and see if it helps to fatten up the mixture slightly.

[CarsonTech]

Thanks, I didn't think injectors this small would require much messing around with. THey are the 30# SVO red tops.

I will play around with the EQ today and see what results I can get.

[CarsonTech]

Well, I played with the AFR by using the Scanner in the problem areas. I confirmed that I was seeing the correct AFR being logged in the scanner and on my wideband compared to was I set the AFR to on the scanner.

No matter what AFR I was at, I still got bucking.

So with what I have researched that helped others, has not helped me.

Changing the timing, AFR, TC parameters, TF parameters, and trying to get the RAF tuned properly, has not helped my insane bucking situation under low load, low throttle situations.

Although, I do know that when I tried tuning RAF, the airflow numbers seemed too low at warmed up idle. The car didn't idle well for a few minutes after shutting it off when it was warmed up and starting it back up.

I am going to try RAF tuning again this weekend for more data to look over.

I am also going to switch my wideband to my drivers side narrowband bung to check the AFR, as compared to where i have it now (in mypassenger side bung).

[CarsonTech]

Progress has been made on the low load, low throttle bucking problem. I didn't expect the results, as I was just screwing around.

I smoothed out my VE table a lot, by hand. Then raised some of the problem areas cell values and smoothed by hand again, to richen up the problem area.

I then logged some data to tune out KR again. Which lowered timing a lot in some areas.

I took it for a drive again, noticed a little less torque do to the car running a point and a half richer than stoich where bucking had been. The bucking is MUCH less significant, and the car doesn't buck at all when engaging the clutch to start from a stop, like it was doing.

I do get slight bucking in really low RPMs at no throttle, like at 1200 and below, but that is expected.

Still have a fine tuning to do, and I know there is a wrong way to make stuff work, a right way. This is working for me, so I am going with it.

I am still going to swap the o2 sensor to the opposite bank and check the AFR. And see about getting a non drilled TB and redo RAF tuning.

[CarsonTech]

One thing I dont understand is that when using the scanner to change stoich to be richer, that didnt seem to help the bucking. I guess it was the hand smoothing in the VE table tha really helped.