VE LTFT tuning - rookie here

[bennettrp]

Hi,

I've put a G5X3 cam and AFR205's on my 04 C5 LS1. Now trying to "tweak" the tune.

I did some scanning of LTFT's, found they were off considerably and then made adjustments to MAF table to get trims into line. They are running right around 0 now, and she runs pretty decent. Not perfect, mind you.

So I move on to VE tuning. I'm struggling with the directions posted in the beginner section. Sporadically the car runs like absolute crap, with all kinds of codes.

My procedure, as defined in the "how to" section of this forum:
1. Set MAF frequency to "0". Did not tinker with any DTC's, so SES light lights upon start.
2. Fire her up.
3. Turn on the scanner and Reset all trims.
4. Drive under different conditions to get as many hits in the FT histogram as possible.

So I fire her up and she starts sputtering and won't get over 1200 rpm. I shut her down and fire up again. Sounds pretty good, so I start up HPT scanner and start logging. She starts sputtering and I cann't get her out of it, so I shut down. Start back up and she seems to run OK as I move thru a few fuel trim ranges. SO I take her out for a drive. I slow down in the country and she starts sputtering. I pull over and shut her down, restart and off we go again. When she's not sputtering, she's running pretty good and logging fuel trims off by 10-15, particularly in the low RPM ranges. SO I conclude the low end of my VE table is out of whack. Agree?

Now I've tried a few different methods for this (as documented on this site), like unplugging the MAF, and she wouldn't run well enough to get her out of the garage.

Can anybody tell me what I'm doing wrong? Am I not following the directions accurately? Is there a different way you do this with a C5 LS1?

thanks

[Bill@HPTuners]

a. Don't try and tune a big cammed car with your stock o2's doing trims
b. the end.

my recommendation, spend $200 on a wideband & use 1 credit to get the 1 bar SD RTT for your vette & tune away

one other thing, as mentioned in the hptuners help file how to you cannot disconnect a vettes maf...since the IAT is located in the maf it can have a bad impact on things, just follow the fail frequency steps & you should be fine.

[Bill@HPTuners]

if you want anymore advice you might wanna post your current tune...I know myself I like to see whats um how can I put this nicely, done wrong, so I can at least help you fix it right off the bat.

[bennettrp]

if you want anymore advice you might wanna post your current tune...I know myself I like to see whats um how can I put this nicely, done wrong, so I can at least help you fix it right off the bat.

You're speaking to a rookie here, so any advice is welcome. When I bought HPTuners, it wasn't obvious to me that I needed a wideband. And then again, I had only read it was really needed for PE tuning. So I thought I would use the one at my local dyno when I got to the "level" of PE tuning, which I have not started yet.

But lately, after tinkering/reading threads, and generally getting smarter, I figure it was only a matter of time before breaking down and buying it. Only problem is putting a bung in the headers.

Here's the .hpt

She actually runs real decent now, except for some surging in the 1100-1300 rpm range under low load. After addressing that, I was intending on smoothing some of the curves and then moving into PE.

Thanks for any help/advice. Its all welcome.

[Bill@HPTuners]

I know a couple of other people that had the low rpm surge as well...probably not much you'll be able to do about it.

[bennettrp]

SHHHHHH! Don't say that too loud. LOL

If my wife hears that about her daily driver, she's gonna stop and pick up that yellow vert she's been hawking lately. :-)

anyway, I haven't given up yet. Still having fun with this.

Anyway, I still could use some help (er, jabs) on what's wrong with my VE tuning technique? btw, adjusting down the low rpm end of the VE table a bit really seems to have evened out the idle.

Thanks for help.

Dick

[EC_Tune]

BTW: Like FOFF said, on 01 & later Vettes or ANY vehicles with the 5-wire MAF, don't unplug the MAF as that unplugs the IAT sensor as well. No more air temperature measurement...

Just go to the Engine Diagnostics --> Airflow tab and set the MAF fail frequency from 13500 (or what ever it is in you stock cal) to 0. Then click on the DTC list and set the P0103 code to "MIL on First Error". Now you are in Speed density mode.

Oh, and what FOFF said: Try out the 1 bar RTT. It's fun moving the fuel around in real time...

Last thing... Do you have any idea what the cam spec's are on the G5X3? Might help to ballpark your tune.

[Bill@HPTuners]

i think its like 234/242 600/610 112 or 114

[bennettrp]

BTW: Like FOFF said, on 01 & later Vettes or ANY vehicles with the 5-wire MAF, don't unplug the MAF as that unplugs the IAT sensor as well. No more air temperature measurement...

Just go to the Engine Diagnostics --> Airflow tab and set the MAF fail frequency from 13500 (or what ever it is in you stock cal) to 0. Then click on the DTC list and set the P0103 code to "MIL on First Error". Now you are in Speed density mode.

Oh, and what FOFF said: Try out the 1 bar RTT. It's fun moving the fuel around in real time...

Last thing... Do you have any idea what the cam spec's are on the G5X3? Might help to ballpark your tune.

Thanks for giving me some confidence, EC. I did as you said. But I got real uneasy with her sputtering like I said at beginning of thread. Thanks also for clarifying that my C5 has IAT sensor in MAF. I kinda thought so, but wasn't sure. So I guess I was in SD mode. Any idea why it was sputtering? Possibly my VE table was WAY OFF (the one posted has been tweaked down a bit)?

Cam specs are 234/242 duration and .602/.610. 114 LSA. LG does not post, but they're available in several places. I found on LS1Tech.

I found a couple of tunes for G5X3's on this site and noticed that they all seem to have significantly lower values in the VE table, particularly in the low RPM ranges. Make sense?

I've got fuel trims decent using MAF, but it seems that I'd better get the VE table better before I start playing too much with other things. Agree?

I'll take her out again today in SD mode and see how the trims are looking.

Any other thoughts are welcome.

D

[bennettrp]

i think its like 234/242 600/610 112 or 114

You got it FF.

[bennettrp]

Oh, and what FOFF said: Try out the 1 bar RTT. It's fun moving the fuel around in real time...

Ah! And I just checked out the RTT function. I had already played with the timing stuff in the VCM controls stuff, but this is pretty slick. Its now making more sense. But I don't find the parameters in the VCM - Engine - General tab of the editor. Is this another enhancement I have to "acquire"?

[Bill@HPTuners]

Ah! And I just checked out the RTT function. I had already played with the timing stuff in the VCM controls stuff, but this is pretty slick. Its now making more sense. But I don't find the parameters in the VCM - Engine - General tab of the editor. Is this another enhancement I have to "acquire"?

RTT is included(at no extra charge)with all of our custom operating systems...for the 1 bar SD custom OS & 1 bar MAF custom OS it uses only 1 credit out of your initial 8 to apply

[bennettrp]

Thanks, After fumbling around I just found the "how to".

I assume that once you set up a pcm to 1 bar sd, that it stays that way?

[Bill@HPTuners]

depends how you set it up...if you enable the maf it still works just fine which is why myself & EC_tune prefer just using that custom OS then the maf OS in most cases so that we have the best of both worlds...a tps vs. rpm multiplyer for even more resolution, secondary VE is gone, full use of the high/low octane tables if you ever go into SD mode, RTT & can use a maf still

[bennettrp]

Success!

Well I adjusted the VE table using VE mode. Trims in the low kpa were all off by about 15% and low rpms up till 4000 and kpa less than 60 were off by close to 10%.

After first adjustment, trims came in close to zero and the sputtering is now gone. In fact, she ran pretty good in SD mode after trims adjusted. Why should that not surprise me.

Thanks foff and ec_tune for advice. This piece actually was pretty simple once you explained it.

On to the next step.

Merry Christmas!

[Bill@HPTuners]

always glad to help

[EC_Tune]

Glad you're having fun in SD RTT mode now!

EC