(safe) timing #'s with different fuels

[SH4DY]

I'm planning on heading to the dyno this weekend to dial in the car and was just curious what kind of timing people are running on their boosted LS motors.
Historically, I've only tuned these motors on pump gas and low (<10psi) boost (street cars) and kept timing pretty conservative in the 10-12* range to keep things safe. Plugs generally look pretty good and the motors last.
This trip to the dyno is with my personal drag car (stock piston/rod LS1) and I'm running VP110 and planning on running 15-ish psi. MS3pro with no knock inputs so there will definitely be some apprehension.
I figured I would start with my "street" timing curve and get the boost sorted out, then creep up a degree or two - thinking 15-16* max.

Looking through maps I've seen anywhere from 10* to 18* north of 15psi depending on fuel type and/or meth injection.
Anybody want to chime in?

[freeskier7791]

No experience with boosted cars but you can go 32* with race gas on NA.  I think staying at 16* is safe and will still make plenty of power.

[largeorangefont]

On 110 you'll likely be able to get more out of it than 15-16 degrees, but there are too many variables to really get a meaningful answer. The process you stated is the best way to go.

[coltboostin]

Bone stock Ls1, down to the cam!

This was on 23-24 psi.  Cam2 110 out of a pump down the street.  17 deg up top.  Took 2 seasons and a few accidentally 30psi pulls to bend a rod.

[SH4DY]

What plugs were you running? I had BR7ef's in there gapped at .028" and it was not happy under a lot of load. Thinking they are too cold. 2nd gear pulls at 6 psi were fine but when in 3rd (th400) it would hesitate so badly i would have to abort the pull- wouldnt go past 3,800. Afrs were 11.5, 14# of timing, 6# of boost and holding . I picked up some TR6's that im going to gap down to .025" to see if that helps. Wonder if I'm fighting the 110 octane fuel?

EDIT: I'm also going to try increasing the dwell to 3.5ms and see what that does (up from 3 - LS2 coils).

[SH4DY]

Attached is a screen shot of the log. Pull starts at 3,000 and I lift at 4k - takes 4 seconds to get there. Gets to ~3,800 and starts to miss. 4psi boost - my KPA math was off. Could probably stand some more timing now that I look at it but either way...

[blacksi]

I ran 15 degrees once boost came on for years, then tried to bump it up more for the GA 1/2 mile to 17 and melted number 7... That was on 93 and around 9:1 compression.  I usually shot for 11.8 AFR but errored to the low vs the high.

[coltboostin]

What plugs were you running? I had BR7ef's in there gapped at .028" and it was not happy under a lot of load. Thinking they are too cold. 2nd gear pulls at 6 psi were fine but when in 3rd (th400) it would hesitate so badly i would have to abort the pull- wouldnt go past 3,800. Afrs were 11.5, 14# of timing, 6# of boost and holding . I picked up some TR6's that im going to gap down to .025" to see if that helps. Wonder if I'm fighting the 110 octane fuel?

EDIT: I'm also going to try increasing the dwell to 3.5ms and see what that does (up from 3 - LS2 coils).

I was on 7's.  Same set of plugs for a whole season



Yes on baby boost stick with a 6.  I would not go 7's unless you are consistently above 14psi.  Gap .22-24

I ran 15 degrees once boost came on for years, then tried to bump it up more for the GA 1/2 mile to 17 and melted number 7... That was on 93 and around 9:1 compression.  I usually shot for 11.8 AFR but errored to the low vs the high.

On a 1/2 mile pull with 15psi Im shocked you were dicking around with pump gas.  Everythings gets so damn hot on a pull like that-you want the coolest cylinder possible.  I am 100% sure you would have been fine on better gas.

[coltboostin]

OP so what did you end up making? 

[SH4DY]

No #'s... I didnt notch out the frame rails enough and the tires were swelling up and rubbing at higher speeds ( 275 MT ET street pro radials). I was able to work on the fuel tables some though so i may just forego another dyno session and just dial it in at the track. Just check the plugs and see what the mph does...

[BlnLs1/rx7]

No More than 18 degrees or your rolling the dice.