silverstream

Which is the better options ? To richen it and advance timing or lean the mixture and retard timing ?

My thought will be, by running richer, we run lower risk than leaning the mixture ? However, enriching the mixture first causes worser fuel consumption and also introduces incomplete burn.

Any expert advises ?

MR Turco

iTrader: (16)

From what i have found in street tuning/butt dyno is that slightly richer (low 11:1) more advance feels better then leaner (high 11:1) and less advance. I think byran (razorlab) has done some testing in this area so he should have some nice data. I am also not too fond of the higher EGTs yielded with leaner fuel. I can definitely say that the richer scenario has much safer egts by almost 100F.

C6C6CH3vo

iTrader: (9)

First, richen and retard, log, lean to mid 12 if not octane limited, mid 11 if on pumpgas, log, add timing, log, until it quits making power or pings (whichever comes first).

More advance and richer makes better torque the opposite is true for HP, but this also depends on 100s of other factors like fuel, charge temp, and soforth.

Richer more advanced combustion has lower egt's but the combustion is slower allowing a longer flame exposer to the protected chamber surfaces breaking down this barrier, hense lower egt's/higher cyl head temps (preignition). Leaner/Higher egts can also turn your exhaust valves into detonation areas (nothere) which is why octane/cooling might be more important making HP with leaner burns.

Personally, I would rather have a higher egt/cht ratio with it leaner spraying loads of methanol and a flat timing ramp. But on pump your better off mimicing the OEM rich/advanced route.

The power curve is flat from mid 11 to high 12 afr but will peak at mid 12 (which is hotter). The temps will keep increasing to about 14.7 then taper off. Pwr is made by pressure (rich) and heat (less rich), the perfect balance is had at peak pwr. The turbo also dictates things

mplspilot

iTrader: (7)

It depends on fuel, set-up and purpose for which the car is used... If it's for the street, all you need to do is set the car up for both and compare DLL's to figure out what YOUR car with YOUR particular mods responds to better. We all drive different cars here, even though they are all called evos

Oracle1

iTrader: (1)

tried both.

leaner/retard makes for smoother driving and less knock.

silverstream

Yeah, I leaned by AFR by very slightly, and noticed I had to reduce the knock by 5 or more timing. So wondering if I'm leaving anything on the table, and end up reducing power instead of gaining more. I don't have a dyno so it's all feel of the pant.

Jorge T

iTrader: (18)

If you can datalog you can compare the time it takes to accelerate for example from 4k to 6k rpm. This works if same day, around the same time (to get similar temp, baro, etc) and on the same stretch of road(same direction).

I've also tried both and my car likes leaner/retard with the same results Oracle1 had.

tephra

iTrader: (6)

its all about fuel burn speed

leaner fuel will burn quicker than richer fuel

THUS REQUIRES less advance.

I opt for leaner (11.5) and then tune whatever timing I can...

Oracle1

iTrader: (1)

I aim for 12.1 midrange, 12-11.9 top end and 11.7 redline. Most importantly 0 knock.