Captain C

What is Highway Spark Mode and what does it do? I'm playing with TunerPro and trying to figure out what some of the Constants do. Any help would be appreciated!!!!!

Twilightoptics

When conditions are right to enable it usually low load on the highway cruising as it works with highway fuel mode.... the computer will add more spark in an effort to maximize fuel economy. I disabled this because I run all my spark in the main fueling table (no power enrichement spark) and when highway spark kicked it, it would put my cruise spark at like 50deg!

Grumpy

It's part of a fuel strategy.
Lean means needing alot of advance for getting it to burn.

Also, puts more heat into the chamber, higher loads on the rod bearings, etc..

You can wind up with Tip-In preignition which the Knock Sensor may or may not sense.

Not worth the down sides, IMO.

Properly tuned, it's not going to make that much of a difference, key word thou, is properly.

JP84Z430HP

So, in a sense, Hiway mode is a way for GM to make up for their tuning deficiencies? Basically, they get a general tune that will work on that engine, since one engine will vary from the next off the line, then use hiway mode to get some mileage out of them.

How many BCC's actaully had hiway mode enabled? Very many?

contactpatch

IMO, the reason that hiway mode affects fuel economy is:
there is less vacuum at cruise, than otherwise, results in
'less negative work' done during the intake stroke.
At 16 to one, you pull less vacuum.
Keep in mind that, at 16 to 1, there is surplus air, so that
all gasoline vapor is burned.

Grumpy

BLs used to take care of the differences in car to car, and maintance levels.

The EPA with the CAFE requirement drove the lean cruise idea. Well that and popularity with customers.

Now, originally, the oems supplied source code to the EPA. With that done, GM went with a lean cruise mode. The EPA didn't bother to read the source code, and when dyno'ing a car saw the LCM, and freaked. They thought GM violated the *spirit* of their intentions, and instantly stung them with a big fine. The downside to the EPA, is that there is no appeals, or forum for relief from them. So GM as well as other has been on and off again about wondering what the real issues are. Now the EPA has bailed from doing any of their own testing, and is now just fining their way into being in a position of power.

This is the 3rd gen related info.,


Not to mention that EGR, and the converter, also play a role in all of this.

Captain C

Unfortunately I don't have my laptop with me at work to verify it, but it seems that the highway mode didn't kick in (according to the setpoint) until it hit the high RPM cut off limit. That of course would make it totally worthless anyway....

I'm still trying to work my way through all the help files in TunerPro. Then I will read through the Holley DFI manual and the Accel DFI manuals to help me understand as much as I can about what to change in the programming to meet my goals.

Once I get my PROMinator, I want to setup several different bin files on it. I want to have a bin for power (duh!) one for gas mileage, one for normal driving, and one for smog purposes. I don't want to trash the engine so I will only change a very minimal amount of things until I know very clearly what I'm doing. So y'all get ready for lots of questions!!!!