On my 13B-REW when tuning your vacuum range what a/f should i be shooting for?

I just switched over to 850 primaries and I need to retune my entire map.

The car was running really poorly so I data logged with lambda and I was running in the .77-.82 range. (11.3 - 12.0 a/f) remember this was with no boost in the 2-3K RPM range. I pulled my plugs and they were sooty and black. So I now know 11.3 a/f is way too rich for vacuum low RPM.

Where should I be aiming for? I redid the maps and have it in the .95 to 1.05 (13.9-15.4 a/f) range now and got nervous that may be too lean.

I remembered I had trimmed my fuel back 10% so I fed it back 3% more. This should put me in the 13.3-13.5 range. The car seems much more happy here though.

Thanks for any input in advance.

 

Medium to high vacume i run mid-high 15.x:1 afrs, on reallly cold days ive dipped into 16's and the car still runs fine, sometimes it will buck a little and start to miss, but its rare.

i run bout stoch around low-vac quickly going to 14flat at the first sign of positive manifold pressure dropping to mid 13's and attempt to taper richer and richer as boost comes on (but i suck and my dataloggings finiky) so it doesnt work so well.

 

This is where staring at the wide-band is a waste of time...
Just lean the bitch out until you can tolerate the lean surge...

At higher RPM's, watch the EGT - this is where the wide-band is basically useless.


-Ted

 

lean surge?

I am not sure I get what you mean.


I ordered a EGT Gauge so for now I will not tune too much until I get it and install it. I will concentrate on getting some break in miles on it.

What temps are optimum for what situations?

i.e. cruising while in vacuum?

Running hard under boost?


Time so do some reading under EGT?

Thanks for the tips guys.

 

He means when the car starts to buck and hesitate at whatever load point (under vacuum but not approaching boost threshold). Lean it out until it starts doing that, and then back off a little bit.

 

Yep...
"Lean surge" is the condition where the engine will start to hesitate due to too lean of a mixture.
So...you lean it out to the point where you can handle the hesitation.
This works well up to about 4kRPM and beyond, so it's good for most freeway cruising speeds.

Above 4kRPM, the engine will tolerate a really lean AFR, but it will not lean surge as much.
Although it's nice for gas mileage, the EGT's get REALLY HOT.
I've seen EGTs hit over 1000C or over 2000F without the engine showing a hint of lean surge!
That was just too hot of an EGT!
We're talking cruising speeds approaching close to 100mph, so I dunno how many of you can drive at illegal speeds like that.

Since we're not under load, there is zero change of detonation.
Lean surge is a misfire due to too lean AFR's.


-Ted