Hi..

Will experiment with a sort of Highway mode ($58) this year.

I have dual WBO2 and EGT now so I think I have the things needed for this.

How lean is normal for highwaymode? I scanned a 6E car with WB and it went to 15.5 when HWM was activated.

And what about SA adder at lean crusie, why is it needed? Shouldnt it be enough to give it less fuel, why raise the EGT more with more SA? or am I wrong here

Does big bore engines require more timing? I think so........

/N.

 

I cannot directly answer for you. I have noticed that Highway Mode seems to work differently (and with different results) depending on the calibration.

I found HM worked best with the SD/MAP based $8D setup. On the 89 MAF $6E, I had issues. I was getting spikes with lean readings, even with HM turned off.

I found the $8D yielded more consistent results. I did run very lean (high 16s/low 17s) with no noticeable issues. But, I also got some incredibly great gas mileage, especially for an L98/4L60. This was when I had the TPI and a functioning EGR.

Now that you are experimenting with $58, you may find even more issues and build a bit of knowledge base on this subject.

 

Is xtra SA needed in HWM? or have anyone tried just to lean out the AFR?

Will post results, have to put the engine together now first.... and install the EGT....

/N.

 

Yes, a lean mix burns slower. You can run as a lean as possible with it still firing off. Basically run it up against the lean misfire limit.

Then add SA until the power comes back with no roughness or ping.

RBob.

 

Advancing timing REDUCES EGT. EGT (or things that affect it) is mostly about combustion efficiency (and where the energy goes - cooling/lubrication system, exhaust (EGT), or pushes the piston down which turns the crank (torque)).

 

Without the added timing your pedal will go to mush.

Just try it once and you will understand what we mean.

I am like the only one who has never had highway mode work for me. Its certainly not for lack of trying.

I will begin the assualt again when I come home in summer and have a 1000 mile trip home.

 

for me it didn't take much additional SA in HWM, depending on MAP, i run 2 degrees at 65 kpa, 3 at 60, & 5 degrees from 55 to 40 kpa. its quite noticeable without it. im thinking about bumping it up a little more at 60 & 65 kpa to see if it makes a difference in my fuel mileage. on average my MAP is around 55 ~ 60 kpa at cruise in overdrive. without the additional SA, i was getting MAP readings of 60 ~ 70 kpa under the same conditions.
i have the AFR set to 16.2 at 60 kpa in the bin. i won't know how accurate it really is till i get a wideband.
as far as how it drives now, i can't tell when im in HWM or not unless i look at my O2 voltage, seeing a flat line on my O2 took some getting used to.

3.8, are you running a 730 ECM with 8D in the two 91s?

 

Though actual numbers are different, the highest "extra timing" that I added are very similar to the MAP values given by DENN. The "cruise range" of the MAP value 40-50 kpa had the highest spark advance and then I decreased it from there.

I also did experimentation of when to "phase out" Highway Mode. I found 70-72 kpa was the best for me. I did various experimentation on highways and the 70-72 range worked best to drop out of Highway Mode.

I found my best gas mileage with an AFR ratio of 17.2:1 with 47* of total spark advance in the 40-50 kpa range. I reduced the AFR ratio and spark just a little until around 60 kpa. Then I started drop the AFR ratio and spark advance quite quickly until around 70-72 kpa where I dropped out of Highway Mode entirely and matched it to "Normal mode".

HTH

 

Wow 47 deg of spark
My highway is about 16.0-16.5 AFR. Gets about 20.5-21MPG when I take it easy (highway).

I am so dumb. just checked my SA-highway table...0.00 across the board.
I probably could get 1-2MPG more with some timing