highway mode fuel min. vehicle speed highway mode spark advance min. temp. what are these. do these determine when the motor goes into highway mode? i haev 255mph and 151.25 deg. celcius respectively.

yes they do, and your settings have it turned off

that's funny, this was SUPPOSED to be a stock bin file. would you happen to know what they should be or better yet happen to have a copy of a known true bin file for a 91 5.7 tpi with automatic tranny? i don't know what the other settings should be either.

Its turned off from the factory.

It is common for highway mode to be turned off. The only 3rd gen that I know of having it enabled are the '89-92 TBI cars.

The BIN you are looking for is AUJP.

For settings try using 45 MPH and 70 - 75 C on the CTS.

RBob.

really
why would it be turned off from the factory?


thank you RBob

Most likely the EPA. NOx increases with lean cruise mode.

RBob.

bringin this one back, found it on search.

i'm running a modified ARAP on my 87 5.7 gta, i do alot of highway driving currently and i want to setup the the highway mode but i don't have wideband 02, just chip burning equipment and datalog capability.

the engine is stock, but has AIR removed, no catalytic converter, a modified y pipe, and a 3 inch cat back exhaust, pretty much stock.

what would you guys suggest for a starting place for highway mode settings? Obviously the first place to start is the qualifiers rbob stated, but what about the timing and fuel? i know tuning is very situational but seeing as this car is quite stock, i thought perhaps someone could give me a starting point and maybe some tips on the adjustment so that i can datalog and improve from there.

thanks alot guys

hey any clues guys?
just lookin for some ideas on where my advance and trim should start at roughly.

RBob is correct. The EPA and CARB determined the "Highway Mode" to be a defeat device, so GM was forced to disable it.
Lucky for us the code still exists in the SW to use it.......

The general concensus is to take out all highway mode spark advance and stick to base timing. From what I've heard it doesn't improve mileage and ends up causing overheating problems.

You should set your enable parameters to just below whatever speed you cruise at on the highway and whaever you find as safe operating parameters. GM has enleanment set at .94 in ARAP ($6E), which should give about 16:1 AFR if I've got my math right. I'd like to try enabling this at lower speeds (35 maybe) to see how it would behave, but I'm stuck using $32B. No enleanment for me... unless someone is kind enough to come up with a patch.

ah so it leans it out on it's own! i thought i needed to change the trim manually. Good deal i'll set the enable and pull the spark timing.

Actually, it did make a difference for GM.
You have to remember these were the early days of the HWFET test for data fleet cars to establish that new EPA Highway versus City fleet number. So it does help.

As for the amount, if you take Lambda 1/0.94 = 1.064, and Stoich for gasoline of 14.67:1, so 14.67*1.064 = 15.6 for highway A/F ratio, its not that lean, but did provide some benefit for the testing numbers.

BUT, the EPA and CARB said "defeat device" since it blew the NOx numbers on the cars, so it was disabled by GM for compliance reasons......

Stoich is programmed as 14.73:1 in most stock bins that I've seen. I took another look at 6E and there's a table that specifies highway afr vs load. I was thinking of decel enleanment. D'oh!

enabled with 5 degrees timing left in, seen a bump in fuel mileage, waiting to get thru this tank to get better numbers, i'll report back then guys.

bringin this one back.. but was enabling this highway mode really worth it? Saves gas but pollutes more? Did it overheat? On the highway when I cruise I am not even close to overheating in my car..

Thanks for continuing to have questions on this area, as I've been wondering about it recently as well. My most recent calculation of gas mileage for my 93 Caprice wagon, Shammoo, has been all of 11mpg. Gorey details are in my signature below.

I'm looking at turning Highway Mode back on as a way to get a little more mileage out of the beast. Even all the way up to a near miraculous 12mph would be a 9% increase. Unlike GM, I'm not worried about my fleet mileage. I'm just interested in making an improvement in this car in particular.

There are others of us anxiously awaiting the results from those that have tried this. Would love to know how to wring even more mileage out of a gallon of gas.

i've ran hiway mode on my motor, a lot.
if im not working on the tune, hiway mode is turned on.
i have it set to come on around 45 MPH and 1200 RPM.
if you go too lean, fuel mileage will drop before you get into lean misfire, or at least it does for me.
by the coolant temp, i've never had a problem with the motor overheating.
i don't have a way to watch the oil temp, so i don't know what its doing.
my rear gearing is pretty tall, 2.42. with the 700R4, i spin around 1500 RPM at 70.
i also have a working EGR system which helps to cool combustion chamber temps down.

i add some timing with hiway mode, 2~3 degrees.
i have hiway mode lean cruise set to come in 5 seconds before hiway mode timing.

with hiway mode, my best was almost 30 MPG on a road trip a couple of years back.
on the same trip without hiway mode, i've gotten a little over 27.
other than getting to the freeway from my house and a few small towns, that trip is pure hiway driving.
my driving on both trips was almost identical. A/C and cruise control on, and about the same amount of time running 90+.
i was so close to 30, that i think the 2 WOT blasts i did from 0 to 70 were enough to keep me from hitting 30 MPG.

I'll be loading my changes into my Prominator later today, and run it for the week. Similarly I set the speed to 45mph, (was "off" at 255) Time set at time at 8 sec, and I bumped down the commanded AFR to no higher than 16:1 It was at 16.3:1. I'm a bit leery of going too lean until tested.

I also lowered my fuel table entries just off idle 900-1300rpm where my "neighborhood" driving is. My BLM's have been a little rich in this area and it's where I spend lots of time in the city traffic "stop and go" 30-40mph range. So a little gas savings here might also help.

Of course I'm expecting the fact that no good deed goes unpunished and the Law of Unexpected Consequences will rear it's ugly head. So I can report back after a tank of gas to see if there is an improvement. Unlike Denn_Shah, most of my travel is strictly around town, with some express way driving a few times a week.

Stay "Tuned"

Dave

FWIW, here are my highway mode settings. I have used it a long time as well, but like someone said above, not real good mode for tuning.
Min speed 50mph
min rpm 1300
min temp 161 degF
LV8 to disable 130
2 minutes in, 5 sec out.

And I do add some spark, like 9 deg at low loads, and less as load increases.
For AFR, I have it lean as 17.00 at lowest load, then 16.9, 16.7, 16.5. Now I do have an LM1 WB, so I can watch "leanness". It never really gets that lean. I mostly look at the Lambda #, and if it shows 10% lean I am happy.
As far as results, I havent seen a big gain in local driving. I get about 17-18-19 local. But I have gotten up to 22 on some "trips". With my gears I think that is good. Actually I dont really drive that many true "highway" roads.
I had tried enabling at 40mph, but I dont think it helped. Only drive back roads at 40-50mph, and I think it runs better in normal closed loop with the O2 doing the corrections.
So IMO, i think it can help if you truely do ALOT of real highway driving.

I've run high way lean cruise for a number of years. Easily good for a 10% increase in MPG.

RBob.

What is the difference between highway lean and highway spark? Can you have noe enabled and the other one disabled or do they work hand in hand together?

They should be tied together. As the AFR is leaned out it takes longer to burn. So adding SA should also be done. The various masks do it differently. Need to look at the one you are using to see how it works.

RBob.

Can u show me what settings i need for HW mode?

Rbob,can you list what i need to change to make HW mode work for my superAUJP 8D.bin?

before you really use hiway mode, your fuel and timing tables need to be pretty close.

to enable hiway mode, find and lower the coolant temp and MPH qualifiers in Constants/Scalers.
set the coolant temp a little below what the motor normally runs at on the highway. IIRC, im around 10 degrees below what my motor runs at.
set MPH at what ever speed you want. i have mine around 45~50 MPH.
i have hiway mode fuel set to come on 5 seconds after the conditions are met, hiway spark is set to 10 seconds.
get on the road and make a data log and see if hiway mode is engaging.
adjust hiway max map if needed.
hiway mode will automatically turn off after being on for a certain amount of time. you can change time on/off in Hiway mode fuel Max time in Constants.
with all the 8D masks, hiway mode time on is the same as time off.
in other words if you set it to be on for 60 seconds, it will turn off for 60 seconds too. if its set for 120 seconds on, it will be off for 120
seconds.
personally i would like to be able to control time on and off along with a couple of other things separately, but i don't think its possible, at least not without a major rewrite of the code.

next, find the hiway mode AFR vs MAP, and hiway spark advance vs MAP in Tables/functions.
hiway spark may be zeroed out, start by adding 1 or 2 degrees and work up.
do the same for hiway AFR until you either get into lean misfire or see drop in fuel mileage.
watch your coolant temp, and the oil temp too if you have it.
if you do get into lean misfire, drop the hiway AFR back down by .5~1.0.

there are some other threads on hiway mode. you can do a search for highway mode, hiway mode, and lean cruise.
i believe those are the 3 ways its of wording it that its been posted about.

if you haven't already, look into S_AUJP_V4. it has a lot more things added to it than what the standard 8D mask has.
a warning about V4, there are some things that you can not use copy and paste on. that info is here in one of the S_AUJP_V4 threads.
also, im not sure if the current files at Moates for S_AUJP_V4 have been corrected or not. there is info on what needs to be checked in one of the threads on V_4

Is that done to reduce combution chamber/coolant temps in head? Too long at lean A/F ratio if kept in hyway mode?

It is to allow the BLMs to adjust as the engine characteristics change. Provides a more accurate AFR while in lean cruise mode.

RBob.

I wonder if I enabled hyway spark in tune. Need to look at that this weekend.

I would have thought that the on again off again of hyway lean would just cause the BLM to move following the A/F? would not a BLM adjust to a changing A/F every 60 secs or so? How soon does a BLM move following the Integrator changes it sees?

Can't you set the frequency of BLM adjust? Like isn't it every 3 seconds by default?

Are you suggesting when using hyway mode one should deviate from stock settings?

I am using stock LO3 setting for hyway mode and it is active. EBL.

If hyway mode cycles every 60 secs for example should the update rate for BLM be changed?

that was my point. If hyway is on off 60 sec cycle would not BLM respond to it being on or off every 60 secs?

During highway mode the INT is reset to 128 and the BLM won't move from where it is. When the ECM exits highway mode the ECM resumes closed loop (if closed loop parameters are met), and the INT/BLM are allowed to adjust.

I've found that 12 to 15 seconds of highway lockout (closed loop) is enough for some BLM adjustment. Then in highway mode for even 3 - 4 minutes works.

Note that the EBL has separate timing parameters for in and out of highway mode.

RBob.

Makes sense now ! Thanks.

i noticed when i was driving thru drastic changes in altitiude that sometime HF AFR would drift, once it dropped out of HF the blm would move from like 130 to 120, depending on the temp and baro. then it would lock it where it was at when HF cycled again.