11 Bravo

iTrader: (3)

When I got dynoed, my a/f was 13.0 across the board. I think I'm still a little rich. When I nail it, I get the smoke out the pipes, and the carbon (or whatever) inside my exhaust tips. I have AutoTap on the way, how much hp could a MAFT help me eek out? If 13.0 isn't too rich, what's up with the puff of smoke and the carbon in my tips??

[ November 24, 2001: Message edited by: 11 Bravo ]</p>

ChrisB

You might find another 5-10hp, though the 10 number would suprise me. 13.0:1 is pretty close to ideal. At your torque peak I wouldn't go any leaner, though you could probably get away with 13.3-13.4:1 at your hp peak.

It's not going to be that huge a difference though.

As for black smoke my guess is it's only on initial acceleration, etc. It shouldn't continue to smoke on steady state TPS (Basically the computer version of a "acellerator pump" - it is probably set extra rich to kill detonation/pre-ignition problems during transient acceleration


Chris

11 Bravo

iTrader: (3)

Yeah, I thought 13.0 was pretty good. But, I don't like the puff of smoke when I nail it. That doesn't seem like something that should be normal. And it's almost embarrassing. People probably think I have a fried engine. I know it's not normal for other engines, it is for ls1's?

Colonel

Normal. Mine does the same thing. I wouldn't worry about it.

gfbrown

Thanks for posting this message. I had my car dyno'd for the first time the other day and we discovered that my A/F was 11.6 ! Needless to say, this did not make me happy. Makes me wonder about the last folks who tuned it after I added some bolt-ons!

Anybody know what factory A/F should be? Should I run a little more to the lean or to the rich for a daily driver that I bracket race a couple times a month?

Many thanks in advance,

Gary

<img src="graemlins/corvette.gif" border="0" alt="[Corvette]" />

JS

iTrader: (4)

LS1's like to run closer ot 13.3 to 13.5 N/A
Thats an olbsrvation...

JS

Terry Burger

iTrader: (4)

My car seems to run best at 13:1 dynojet. The black smoke could be tip in fuel enrichment like ChrisB mentioned, or could be an oil control problem.

VINCE

iTrader: (1)

My car likes 13.1 as well..

EFILive

iTrader: (2)

Take a look at the "recorded" fuel map for a 400hp LS1:
http://www.starrperformance.com.au/images/fuelmap.gif
Displayed as RPM v's MAP.
It shows the AFR changing from 14.98 at low rpm/low map to 12.75 at high rmp/high map.

Holes02

I believe the IDEAL air/fuel ratio at lower RPM is: 14.7

When you're on the gas, it richens up to around 13.0...That's what I've typically seen.

Blackbird

you want that puff of smoke. just like all the others said it's tip in.
if you get the puff and then its gone and your running 13.0 accross your setup very nicely.
get another 5hp somewhere else, don't risk leaning out for 5hp.

Skelton

13.0-13.1 is optimal on the dyno. Remember there is more load at the strip than at the dyno so the 13.0 becomes 13.3 or so at the strip. Your A/F is on the money.

01 SS Jay

Practically every car ive seen blows out black smoke when you gag it. Even new lexus's (is that lexi?) and mercedes do that (at least the ones that had the misfortune of being in front of me and thinking they can run haha)

Terry Burger

iTrader: (4)

Just because most cars do it, doesn't mean you want it. <img src="gr_images/icons/wink.gif" border="0">

Matt98SS

mine does that most of the time too if i look in the rear view. I usually tweak my MAFT then and it gets better.

I swear I have to change the settings on that thing when the weather changes but this is EFI and did not think you had to

Brian'sCharlotte(TA)

iTrader: (2)

Last time I had my car tuned.. The a/f ratio was like 16.5-17 to 1. My fuel pressure maintained at about 54 psi so I think I have some clogged injectors. Just ordered some 42lbers so hopefully that fixes it

Brian'sCharlotte(TA)

iTrader: (2)

Damn this is an old thread!

printmanjackson

iTrader: (1)

someone's been digging in the bone yard

YellowToy/A

iTrader: (1)

If you put in 42lbs with out a tune u will wash down the cylinder.

Brian'sCharlotte(TA)

iTrader: (2)

Yeah, I know.. I was gonna put them in and then drive it a couple of miles to a buddys shop to tune it