Blackbird

if yes what target a/f are you finding to be best?

NoGo

iTrader: (2)

I was able to get mine into the upper 15's before she ran funny. You may be able to go higher on a non-supercharged car though. I have a much higher parasitic loss at cruise so I probably end up a little richer.

Blackbird

this one is a supercharged V and it will run in the 16's no problem, I just am not sure how lean is too lean. I know there is a point of diminishing returns, just not sure where that is.

I am just going to shoot for 15.5 unless anybody can tell me they know that xyz will and does work better than that.

Thus my post, hoping to find some folks that have done this or maybe some holden folks can tell me what their cars with lean cruise enabled run at, etc...

NoGo - did you happen to monitor the improvement, if any, in MPG vs just running at 14.7?

NoGo

iTrader: (2)

I could get mine to cruise fine in the 16's, but there was a hesitation if I matted the gas. In the 15's there was no hesitation.

What rate you spin your blower, compression ratio, and advance I think are going to play key roles in what a/f is going to work for you.

I figure MPG at every fill-up but WOT eats up so much gas that 1 or 2 WOT runs and the MPG figure is crap. The car chews up about 1 gal every 40 seconds at WOT. Because of this my mileage runs between 9 and 22 MPG depending on if I beat on it.

Todd157k

iTrader: (5)

I'd like to try it too, however I want to lean out my 'cruising' while leaving wot rich (n20). Anyone know if I "lie" and adjust my injector size at low KPa, will it lean out a little? Or would it be better to advance the timing a low rpms?

Tiger2o69

iTrader: (16)

What table are you guys changing to get this? I assume its not the ve table since pulling from that would change your ltfts/stfts?

jeffstar

iTrader: (6)

Do you mean DEFCO?

NoGo

iTrader: (2)

Car is open loop so I do it with the OL commanded a/f table. Actual A/F is checked with an onboard wideband.

Blackbird

no not dfco, I am telling the car to run 15.5 at certain map values that represent cruise and idle conditions. so when crusing at 65mph steady state down the freeway it sips less gas. just posting to see if anybody had any hard evidence to show what a/f seems to be optimal.

Blackbird

Kevin, do you know if it's feasable to do this closed loop?

I haven't been able to figure out what tells the car 14.7 when in closed loop.

So for now like you I am doing this in Open Loop.

jeffstar

iTrader: (6)

That's going to vary from car to car. Based on the heads/cam/induction package. My car doesn't cruise well at 15.5+ at anywhere in the fuel map except around 40kpa at really low RPMS (6th gear)

Frost

iTrader: (45)

You CANNOT lean out cruise if you are closed loop; it will be corrected through fuel trimming.

Sorry guys, this is OL only.

NoGo

iTrader: (2)

I've never played with doing this in Closed Loop, I haven't had narrow-bands in the car for years.

You may get it to do it in closed loop by playing with the switching point of the O2 sensor, I've never tried though. I think this would be a global change though.

ringram

Closed loop switch points are mapped against airflow.
So while its a pretty broad brush as mentioned you can target it somewhat.

I know guys that alter this (and the CL Mode airflow points) for triming rich at WOT as well as lean cruise.

Plenty or care needed though.

MrDude_1

iTrader: (4)

ive played with commanding different AFRs.... works great.
at low low load cruise, i can go just past 16.0:1...
for low load cruise, i keep it at mid 15s....
everything else, i keep at 14.7 for normal AFR.... PE set rich of course.

Blackbird

your doing it open loop as well Mr, Dude ?

MrDude_1

iTrader: (4)

you can do it in closed loop by having the PCMs target AFR changed. then, instead of aiming for a 14.7 bounce, it will try for whatever you tell it.

the easiest (and temporary) way to do this is to have the scanner open in HPtuners (im sure EFI live can do this too) and command a AFR.... works ok on hwy roadtrips, just tap it off before you get off the hwy.

the other kinda easy way is if you have a 01/02 fbody OS that doesnt do the Holden check... then you can run in lean cruise mode... but thats taboo on here for some reason.

both of those work in closed loop



in open loop, you can make it do whatever you want.
i run in open loop speed density most of the time now.... so it just does whatever i tell it to do.... but im staying at 14.7 in most places because its just easier to screw with...err..."tune"

Blackbird

what table are you tweaking to change the targeted afr while in closed loop?


it sounds like sticking with open loop is what I will end up doing but for curiosity sake I am wondering what table your talking about to do this in closed loop.

Thanks!

MrDude_1

iTrader: (4)

with the cable? there is no table, its in the scanner window.

Blackbird

ahhh ok, so your just refering to a method to test target a/f's to see how the car responds. I was looking for a way to permantly make the change like we can while in open loop but do it in closed loop.



thanks for the replys!