jasonsnova

So as I messed with the tune on my nova (365" ls3 heads,ljms cam, s475) . Anyway I was having trouble getting it to idle decent and finally found it likes 10-12° of timing at idle and a bit on the rich side. , I also had a stumble from a dead stop....which I think was also a timing issue. Once i get above 3k in booost there is zero issues timing ramps from roughly 22° @ 100 kpa down to 12°
Curious to see everyone else's, maps especially off idle part throttle and cruise stuff....

sbcgenII

iTrader: (1)

A car with a bigger cam is less efficient at idle and low RPM. Less efficiency is going to need more timing to make the same power. Try and find a stock LS3 tune to compare yours to.
Are you using HPtuners?

LLLosingit

iTrader: (4)

I'm running a Holley system so I'm not 100% sure how well it crosses over, My idle timing is 14* but have read that depending on cam that some LS3 headed engines go as low as 5* at idle. My car idles at 750rpm warm so I ramp timing up to 22* at 900rpm and it's pretty smooth, I'm also running a 6-speed so that may also make a difference.

It could also be your tune, I had to lean out the fuel slightly at idle or the motor would stumble at throttle tip in.

jasonsnova

sounds simular, I too am running holley and a 6 speed mt. I was getting idle surge nomatter what way I went with fuel....so I was messing with idle timing and my girlfriend came up to me and was chatting and I accidentally keyed in 0° and the dam thing smoothed right out....so I kept adding timing til quality went away then backed it off some....
It was raining so I didn't get to drive but prior to this I had a help of a off idle light load stumble

Nitroused383

iTrader: (10)

Have you verified timing with TDC #1 piston? I've never seen an LS engine like to idle at 0 degrees of timing. Sounds like it's off about 20 degrees, in which case as soon as you get into boost could be really bad.

jasonsnova

I have not.....that being said been in boost a ton(12lbs).....doesnt seem to have any issues in boost. It is a stock crank so I couldn't imagine it being off that far....?
I will check/ verify tho to be sure.

69-chvl

iTrader: (11)

My 5.3 and 6.0 both like to idle with about 12* and 13.2 AFR. Any less/more timing/AFR it loses idle quality and vacuum. This is with an LS6 cam and 600 rpm idle. Kinda weird...my 502 BBC wanted about 30* of idle timing and about 14.5 AFR!!

ddnspider

iTrader: (26)

No way it's happy idling at zero degrees and the cam is installed right.

svslow

My car would not stay running at 0*. You definitely need to verify the timing.

jasonsnova

Here's what I ended at yesterday....car idle at 850rpms 11.8°
Cam is a custom ljms 111 +4
I didn't get to drive it so I can't comment on drivability

badass68

iTrader: (7)

My 6.0L turbo and LS3 supercharged idle great at 16 on E85. The idle spark helps control hunting. 6.0L is 14.0 AFR and LS3 is 14.7 AFR.

badass68

iTrader: (7)

Here you go

jasonsnova

Well I spent 3 hrs on mine last night and settled at 12.9° at 850 rpm 13.8afr.....any more or less timing/fuel idle quality goes away......lowering my idle timing also cured all my idle-3k stumbles. It seems pretty happy now.

toytech93

iTrader: (2)

badass68, our spark table are very similar. I got a 69 chevelle TT 6.0L on E85

TrendSetter

the holley uses kpa for timing
fast xfi uses kpa
0411 uses g/cyl
my evo uses 'load'

Why do oem ecus seem to use some calculated form of load value but stanalones use map for timing?

It makes it difficult to compare timing maps unless you use a standalone.

ddnspider

iTrader: (26)

I assumed it would be based on the equation variables the ECU is using to calculate everything. I.e. some use kpa as a variable, others use g/cyl.

stevieturbo

That's because some are speed density, and some use those silly airflow meters

And some do strange things

And OEM will often use a lot more, and have many fallback options should the main load metering device have a problem or fail.

badass68

iTrader: (7)

Cool, we're twins. Mine is still a safe tune. Probably add a couple degrees once I get it on the rollers.

LLLosingit

iTrader: (4)

If you look at Badass68's timing table you'll see that he has timing the same throughout his idle area, This helps keep the idle stable. If your good as is you might not need to change anything on yours but if it's still hunting idle more than you'd like you can smooth out the surrounding cells and see if that helps.

LLLosingit

iTrader: (4)

Here is my table when I first started my tune, LSA supercharged LY6 LS9 Cam, Flexfuel so I have additional 1D Tables setup to adjust fuel and timing according to ethanol content. There have been some changes but nothing drastic. The one thing that stands out between my table and Badass68's is my timing at low rpm/boost, My boost comes on low/fast with the LSA supercharger so I choose to pull a shitload of timing if I lug it in the lower rpms. They aren't quite this low on the tune that's in the truck now but not to far off. I'm only running 10lbs of boost so anything above that can be ignored. This is also 93 tune not E85, Going from 93 to E85 I have a table that adds timing according to E content.