LostCauseZ06

iTrader: (4)

alright... so my car has been tuned to perfect A/F ratio running speed density with a safe tune and 28 degrees of timing for quite some time now.


last night we decided to do some playing around. dropped it to 26 degrees and leaned the **** out of the car. the car makes a TON more power and there is no detonation at all..

so heres my question. is it safer to runs lots of timing with perfect A/F or is it safer to run less timing and a leaner mixture?

btw a/f ratio is right around 13.5:1 right now with NO knock... we actually advanced it trying to hit knock and hit 29 degrees with no knock still

SSpdDmon

iTrader: (10)

The purpose of the extra fuel is to cool the cylinders and prevent pre-iginition and/or detonation. If you only run short WOT bursts, you might be able to get away with this tune. But, over the long term I'd think you'd want to keep it down to 13.0. Lean is mean...

brad8266

iTrader: (23)

I would shoot for a desired AFR, and then adjust timing till you get knock, then back off a degree or 2.

LostCauseZ06

iTrader: (4)

yeah.. that makes sense... BUT... my car runs VERY cool for some odd reason. stock everything with adjusted fan settings. it runs at 178 all day long unless im in super hot heat at stop lights. the highest it ever gets is 192

we ran back to back to back WOT 2-3-4 gear runs up to about 130 MPH and the car wouldnt budge over 180 degrees.

SSpdDmon

iTrader: (10)

He's at 13.5:1 (in his original post)...

LostCauseZ06

iTrader: (4)

btw.. another odd thing.... when we backed the timing down to 24 degrees advance it started knocking in some wierd spots?? dunno WTF was up with that? why would the car knock with less timing?

brad8266

iTrader: (23)

Mine runs cool with the adjusted fan settings too.

brad8266

iTrader: (23)

yeah, my bad

Ls1Bait

I would imagine cause its pre ignition or its leaning out?

Anyone

LostCauseZ06

iTrader: (4)

pulling timing out cannot lead to preignition.. nor should the car be running any leaner

Ls1Bait

But you were pulling timing from 28 to 26 and you said it leaned it out in your first post.


Im still learning how to tune

Alvin

iTrader: (2)

The AFR the car makes peak power at will be seperated a good deal from the AFR that starts to burn a piston. Flame travel speed and combustion effeciency determine what AFR the engine likes. There is no one magic AFR for every engine. As the mixture goes lean there are less unused reactants to carry heat out, the flame speed slows down which means less heat is there to do isentropic expansion when the piston is at the top of the stroke (where expansion ratios are high) and more heat is there when the piston can't do as muchexpanding therefore it burns edges and pockets of the piston.



What i'm saying is the AFR and the timing you found to work best for your motor is not on the edge of burning a piston. It *may* be close to pre-ignition or knock though. So find the happy spot and back it down a touch and you'll be fine.

SScam68

iTrader: (20)

What's your elevation?

Reason I ask is I notice you're from Utah, Im assuming your at a high elevation with thinner air. You can generally run more timing than guys a lower altitude because the density altitude is higher (air is thinner).

We can run 36 here with no power increase, or knock for that matter.

No reason to run that much though.