muncie21

iTrader: (14)

OK, I've got a Magnuson supercharged LS1 C5 running the stock superchips tune. On the dyno it ran lean (~13.8) with the MAF plugged in and OK (~12.1), with it unplugged. Waited until I got HP Tuners so I could try to figure out what the heck is going on.

Here's what I noticed during a scan today (both runs were in PE mode)--
MAF plugged in: 4-6* knock @4000-5000 RPM (75-100 MPH) pulled timing from 30* to 11*
MAF Unplugged: NO knock from 4000-5500 RPM (75-100 MPH) pulled timing from 30* to 11*

Since there's only one PE table what else could be different? BTW, the runs were in very similar conditions with regard to outside temp and engine temps, etc.

I can post a graph if it helps

Assassin

iTrader: (3)

unplugged it reverts to low octane table, BUT, 30* on a boosted ls1 is retarted, is the motor stock?? , also if your still running the 1bar map sensor dont even bother trying to do an sd tune, been down that road for a week or so straight, better to get the ve tables close and scale the maf to match, then play w/the pe table....

edit: wait I think your saying at part throttle it was 30* right?, and wot it went to 11?.... post a shot of your timing table... and also what other mods you have...

muncie21

iTrader: (14)

I've attached a copy of my hi octane table and also a scan of part throttle knock retard.

Assassin

iTrader: (3)

something does not seem right w/that timing table, check all of the timing tables... that aside, if this is maf plugged in, a 13.8 af is waaaaayy too lean for your set up to begin w/, that kr could be because its soo lean, try adding some fuel, do you have a wideband in car?

muncie21

iTrader: (14)

I'm coming to the same conclusion that a lean condition is causing the KR. The guys on the HPT forum are also helping out. From what I've been told so far I could have a MAF or VE table issue, or both. I'm focusing on WOT right now, to keep things simple for me.
Here's a WOT run with the MAF disconnected. No KR in the entire 30 minute run.

jimmyblue

iTrader: (11)

Which of the two conditions produces a WOT AFR most
similar to what is commanded?

Guy2626c

hey also don't know if it matters but you have a few times where one O2 sensor is very diffrent then the other. Do you have any exhaust leaks esp. around headers. Don't know if that'll mess things up too.

muncie21

iTrader: (14)

Running with the MAF unplugged gets me closest to the commanded AFR.

fast98

iTrader: (16)

look how low his maf lbs/min is....................that is more than likely where your problem is at. find a maf sensor to swap with. the maf sensor is either skewed or modified maybe. but it is reading less air coming into the engine then what is. which will throw off everything

fast98

iTrader: (16)

also this will cause spark retard due to the fact the lower maf lbs/min affects the cylinder airmass calculation and will acctually add more timing

muncie21

iTrader: (14)

Thanks for the suggestions Fast98!!
I just got back from doing a logging run. Based on some reading and suggestions from here and the HPT forum I logged the MAF lbs/min and the Dynamic Air flow (lbs/min) and found the MAF reading to be significantly lower than the dynamic air flow.
My next step is to rework my MAF vs. Freq table to get it adjusted to match the dynamic airflow readings. After that, I'm going to work with the VE tables to prevent part throttle knock.

...<crossing my fingers...>

Steel Chicken

iTrader: (3)

where did you get your tune? when I got my maggie for my GTO, it came with a tune that had a properly calibrated MAF table.

muncie21

iTrader: (14)

The magnuson came with a Superchips handheld flasher. I flashed my PCM with this tune. The car ran fine with this tune...well I thought it was OK until I took it to the dyno. Couldn't do a full dyno run cause the AFRs wouldn't go below 13.6 or so. Serveral trips to the dyno later I found that disconnecting the MAF would bring the AFRs to ~12.1 at WOT.

Thus began my quest for tuning

98Z28CobraKiller

iTrader: (17)

But when you disconnect the MAF you default to the low octane spark table. Are your tables the same?

muncie21

iTrader: (14)

The spark tables are different (I actually prefer it that way), turns out my issue was an incorrect VE table along with some bad parameters in my fueling tables.
Thanks for the suggestion though.

silverTA2002

iTrader: (1)

Does that timing table seem ridiculously low to anyone else?

Then again, I'm not supercharged, so I don't know much about Forced induction timing. I have about 7* of timing more than that across the board.

Before heads/cam, I had about 10* of timing more than that.

muncie21

iTrader: (14)

My low octane table is about 3* shorter than my high one...hope that helps ya.

At WOT, I'm seeing about 15* or so degrees of advance. Haven't started tuning the spark tables yet, as I just got my fuel and air tables good

frcefed98

iTrader: (16)

That kind of timing is needed for FI, silverTA2002.

Muncie, you running that black C5 with the maggie sticking out of the hood? If so you passed me and my red bird on jefferson last thursday I was limping the car home with a leaking tranny.

J

ringram

Look at the O2 mv the maf one is 830 and sd is over 900. Fueling is different. (Probably maf table)
Id say you need your maf table calibrating.
But aside from that if you are running FI ditch the maf, it will run out of capacity under boost. Get a 2bar map sensor and forget the maf, its evil and must die.

muncie21

iTrader: (14)

Yup, that was me. Sorry to hear about the tranny. Hope you get if fixed soon, as I would still like to check out your ride.