Any secrets for a bumping MPG on 1998 305?

[Hipster]

Thanks.

I like to do the HLC, and a replacement muffler, I ordered the over size AC delco air filter.
I have a crv for my main car, still sometimes I have to take my truck on long runs to the property.
Wanting a bit better fuel economy. I think these 3 upgrades will help.

How do I go about get the ECU updated using the HLC?
Local shop? what would I expect to pay for this tune?
Can you recommend a good quality quiet (<if that is possible) straight through muffler?

thanks

I'm not so sure how much lean burn would benefit. It mostly centers on small throttle opening, low load, high vacuum situations which very little of around town stop and go is. I'm not sure 70 mph on the high way gets you into lean cruise either. The biggest factor in stretching mpg is time. There are mpg's to be gained by slowing down to 62-65 mph and otherwise keeping that throttle plate closed as much as possible.

Somebody else mentioned Chrysler's lean setup. It worked and definitely made a few mpg's. The problem was the electronics that controlled it were mounted adjacent to the air cleaner and subject to heat failure and run-on/dieseling/spark knock would become issues. Lean burn is not much more than advancing the timing to 45 degrees or so and leaning out the afr. I too am from the North East and remember acid rain and how many cars I repainted and replaced glass in because the glass and paint were acid etched.

I can't remember how many guys I used to talk to when the homemade hydrogen bottle thing was the rage, but I would ask them if the 2-3mpg they were claiming was a result of the bottle or if it was just because they were paying attention to how they left a stop light or the speed they were running down the highway because they were trying to maximise mpg's. They could never quantify the results.

At the end of the day it's hard to get around the physics that it takes x amount of fuel to generate x amount of hp to carry x weight x distance for a given amount of cubic inches and rolling resistance not withstanding. You looking at spending dollars to save some pennies that's still going to be dependent on how it's being driven.

 

[honkon]

Not at all. Chrysler "lean burn" had driveability problems largely because the computers were hung off the air cleaner--high vibration, high heat, cheap circuit boards, prehistoric control of spark timing and carb mixture strength. YES, "lean burn" was a disaster, but mostly because the components were unreliable and not appropriately sophisticated.

Engine detonation can be monitored via the knock sensor. The main proponent of HLC on this forum has done so, and not found problems in his application. GM clearly found no problems with HLC when they used it in markets that were legal from an emissions perspective.

So HLC was a GM factory strategy, and the difference between stock and modded is entirely in the ecu programming, besides EGR delete? That sounds better than what I had in mind...

 

[PlayingWithTBI]

I'm not sure 70 mph on the high way gets you into lean cruise either.

Mine stays in HLC @80+ MPH, the higher the MAP it will reduce AFR and SA accordingly. At 65 I'm at ~16.5 and 43*. You're right city driving it won't. I have it set to 40 MPH minimum before it goes into HLC. See post #39 on page 4 of this thread.

 

[Schurkey]

Mine stays in HLC @80+ MPH, the higher the MAP it will reduce AFR and SA accordingly. At 65 I'm at ~16.5 and 43*. You're right city driving it won't. I have it set to 40 MPH minimum before it goes into HLC. See post #39 on page 4 of this thread.

I think this is COMPLETELY fascinating.

I've got zero experience "tuning" the computer; everything I've ever done with them is to get them running to factory spec. Frankly, I'm not looking forward to the learning curve. I will probably never experiment with HLC...but I do like the idea.

No idea why they have to disable the EGR to apply HLC. Seems weird to me.

But what do I know?

 

[Erik the Awful]

No idea why they have to disable the EGR to apply HLC. Seems weird to me.

My guess would be that you're already running lean, and recirculating exhaust gases would cause detonation.

 

[L31MaxExpress]

On level road my 350 Vortec stayed in lean cruise at 85 mph pulling an Express van with 3.73 gears and a 4L80E. ~2,500 rpm @ 80 mph.

I did an expirement with the new 383 on the run stand as well with a Q-Jet. I set the APT of the Q-Jet at the factory 2.5 turns out with the larger primary jetting I run. Then I adjusted it up enough to drop 1 in/hg off the vacuum at 2,000 rpm. The difference at no load, 2,000 rpm was close to 30% longer run time on the same fuel volume.

I repeated the same test with an Edelbrock jetted up 6% on the primaries on the power side and 3% leaner than stock cruise calibration. 850cfm Q-Jet murdered the 600 cfm Edelbrock in this test. Even with a carb at 16-17:1 the 11:1 383 runs perfectly smooth. The microphone on my phone picks up the roller rocker noise like 2-3x as loud as they are in person for some reason.

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[PlayingWithTBI]

No idea why they have to disable the EGR to apply HLC. Seems weird to me.

My guess would be that you're already running lean, and recirculating exhaust gases would cause detonation.

Yeah, it's kinda redundant. FWIU in my EBL Flash-II, HLC will supersede EGR - besides, I have it blocked off and the MALF flag disabled

 

[Pinger]

My guess would be that you're already running lean, and recirculating exhaust gases would cause detonation.

EGR reduces the 'lean flammability limit' so mixture would have to be richer - defeating the object of the exercise. It is for this reason that 2-strokes at part throttle (when they retain a lot of exhaust gas from the previous cycle) cannot be run lean without them 4-stroking.

 

[Pinger]

I think this is COMPLETELY fascinating.

I've got zero experience "tuning" the computer; everything I've ever done with them is to get them running to factory spec. Frankly, I'm not looking forward to the learning curve. I will probably never experiment with HLC...but I do like the idea.

No idea why they have to disable the EGR to apply HLC. Seems weird to me.

But what do I know?

From the stuff PWTBI has shared on this forum it's obvious he has really put his back into getting the tune that best suits his motor. All TBI, but tables he has shown me have increased my understanding of my Vortec also. Because much of what is going on with a TBI will also be going on with a Vortec.
The level of technical knowledge on this forum BTW, is beyond anything I have seen on any other forum.

 

[thinger2]

A man has got to know his limitations. Sometimes our limitations turn out to be kinda cruel to us.

Indeed they do.
But that little "what if" is how you learn to pay attention to the things around you.
I think everyone needs to have a "what if memory"
And everyone probably does.