RBob

iTrader: (1)

Made the trip to the Pow-Wow and back with an EBL Flash under the dash of the '92. This car has an EPA rating of 27 MPG highway. Factory stock ECM it would always get a solid 26.4 MPG on highway driving, day-in and day-out. Having done a lot of highway driving this is a solid number.

Installed an EBL Flash with port mod, it is now pulling down 32 MPG on the highway. This is due to the lean cruise mode and better code. And, at times running fuel with ethanol in it. How much I don't know, pump had a label that said 'contains ethanol.' Which tends to reduce mileage.

Made several long drives last summer with some prototype EBL stuff in it. At that time it too was getting 32 MPG on the highway. I wanted to wait until the released stuff was being used before I posted the information.

This is a 21% increase in mileage, not too bad. Highway speeds varied from 65 through 75 MPH. And was 1185 miles RT. I can't say that everyone will get the same increase, but it shows the potential.

RBob.

Dominic Sorresso

Impressive. Glad to see you made it back safe Bob. Great to see you again. Now get going on making an EBL mod to run 16 injectors.

Gary Anderson

iTrader: (2)

I'd be excited about a '7730 version.

Nitsuj86Iroc

Wow, my lil 2.5 liter ranger cant get much more than 27 mpg!

gotta ask, is that motor a 350? during the highway mode what is the A/F ratio?



Also, if there exists an answer, why can't GM do that?? haha or why have they not offered you a job?

elcam84

If they could reduce the possibly large increase in NOX emissions I don't see why not. But... There is allot more to it than that. Start off by cutting the HP of current vehicles in half dump several 100 lbs of accessories and interior junk and then you will have a more level playing field to comapre with.

Great numbers with the EBL. I'm planning on running one in one of my future projects. Been thinking about getting one and having it run my TPI at some point. Just gotta justify the cost.

I assume the port conversion is basically an upgrade to the injector driver.

DENN_SHAH

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nice numbers RBob

RBob

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This car is actually the 6 banger, a 3.1l engine with an auto. During lean cruise the AFR typically runs from 15.5 to 16.6 to 1. Then adding in between 2 & 3 degrees of SA. It kicks out of lean cruise above 80 KPa on the MAP.

The increase in NOX is why the manufacturers no longer use lean cruise. One of the big three had it in the IM240 loop and it still passed OK. Then the EPA found out why the NOX was spiking and that was the end of that.

The port mod changes the injector firing rate. So that the injectors are fired once per engine revolution.

The mention of newer vehicles brings up something I found yesterday. I can't believe how bad the mileage is on this particular vehicle. A 2007 STS-V Cadillac has an EPA highway rating of 21 MPG. And 14 in city. This is the Northstar 4.4l supercharged engine. For highway that is terrible. I can see the city being low as the vehicle has to be heavy, but 21 EPA on the highway?

And the engine is modern: variable valve timing, all aluminum, oil jet piston cooling, 4-valves per cylinder, extrude honed exhaust ports, boost bypass, intercooled, etc.


Here are the highway AFR & SA tables that are being used with the EBL setup.

RBob.

Cflick

I gotta wonder.....
The new three-way cats are supposed to take care of NOx ??

I also wonder about that new Caddy.
Once upon a time......
Had a 67 Continental convertable. 460 engine, 4 bbl carb. You know the rig.
Got around 6 in town ( expected ) but surprisingly, on a looooong trip, would get 20 or
so freeway. Of course, it took about 4 gallons on the entrance ramp, so it would take a very, very long freeway cruise to see the "freeway" milage. Not bad for a 6000 pound vehicle, all things considered.
About 11.8 on my truck coming home from the Pow Wow. Again, all things considered, I'm not unhappy. Last similar trip got 10.0. That's a significant improvement, considering....
Now, to steal....... er..... appropriate ( nicer word ) your AFR and spark, and see......
;-)

V8Astro Captain

iTrader: (1)

I recently switched to a GM 8.5 axle. I got it with 3.08's and I've been running them for a few weeks now. I've ben getting 30-32 mpg on the hiway, lean cruise disabled. This is mostly on an 18 mile trip to work doing the STL standard speed of 75 mph.

Everything is set properly, I have a screen shot on my laptop of the "winning" mpg. This was later verified by the fill up and calc method.

Knowing this makes it really hard to drive the Bronco and drink down 11 mpg

Props to RBob and the EBL

RednGold86Z

iTrader: (1)

3 way cats can reduce NOx well only at 14.7 or less. Go a little lean, and I mean very little, for more than about 3 seconds, and you'll see NOx ppms go from tens in closed loop up to hundreds and thousands.

A combination of things happen when lean cruise - all fuel is surely burned + throttle is open more (to regain the power from leaner which reduces pumping losses)

Fast355

iTrader: (2)

My EBL has been re-assigned to running my 1987 GMC Jimmy S-series 4 wheel drive. It has a Ford E303 like cammed 3.1 with a 2.8 TBI setup on it. The engine makes approximately 200 ft/lbs @ 3,500 rpm and 225 HP @ 5,000 rpm. It has headers, ported heads, port matched intake, 4.3 injectors, and custom tuning on the EBL. It has a rebuilt 700r4 and 3.73 gears. In daily city driving, I am getting 20-22 mpg out of it. That is driving it 40-50 miles one way in traffic. Purely highway, it has seen a best of 25.8 mpg throughout its 20 gallong tank. I do not take it easy on the highway either. I run lean cruise on the 3.1 as well. I hold it in lean cruise all the way up to 100 KPA MAP, although the mixture is at about 13.5:1 and the SA is 0 at that point. This keeps it in lean cruise mode as long as I am not in PE. Works very well once the fuel tables were dialed in.




https://www.thirdgen.org/forums/tbi/...o-economy.html

https://www.thirdgen.org/forums/diy-...l-new-use.html

Nitsuj86Iroc

So this 16.6 A/F ratio can be acurately reached by the stock O2 sensor? I dont have a wide band O2 yet, so Im not sure if id like to play with the highway mode until I had one to check things out.

RBob

iTrader: (1)

Lean cruise mode is open loop. The commanded AFR is changed to the leaner mix. No need for a WB, as a matter of fact I don't believe I've ever had a WB on the '92. Although it is in the plans to do so. . .

Tuning in lean cruise isn't difficult or critical. As the AFR is leaned out the power is reduced. To gain some power back the ignition timing is advanced. If you go too lean during the light cruise area, the engine starts to misfire. If you add too much timing it usually doesn't feel right. And/or it starts to either detonate or get rough.

If you go too lean on the higher load areas of lean cruise, the engine usually stutters a little.

RBob.

devilfish

same here

Grim Reaper

Great mileage Bob.

Your "tuning narrative" is pretty much bang on that I experienced with the AUJP & the '7730 back about 5 years ago. And when I got it "dialed in" using your basic tuning method, I too got great numbers with my L98.

The only thing I would add, is it is a good idea to play with the "transition" area where you slowly "richen" the lean-cruise until you eventually drop out of lean cruise altogether. I did this inconjuction of tuning up long hills/grades.

Jeremy wanted to try one of my "old Highway Mode" bins for a basically stock L98 to see if he too was able to obtain similar gas mileage as I saw. I know another guy saw high 20s on his L98 running that chip, so I'm hoping Jeremy will to.

It would be interesting to see how similar (or dissimilar) the various lean AFRatios, Map/Rpm values & spark tables. I have a funny fealing that the "numbers" might turn out to be a lot more simliar than dissimilar.

Cflick

I'd like to play with it as well.
Of course, it's completely wrong for my combo, and I'm sure your old bin won't run my truck at all, but the slopes, transitions, relative changes and such should, as you say, show the "numbers" more similar than dissimilar.
With my milage not quite up into the low teens, it could save me some re-inventing the wheel ?

Dominic Sorresso

RBob,

Once I had the VE Hiway Cruise mode up to 75 mph and 70kPa. Added about 1.5d of SA and a commanded 16.5 AFR. Once in HM, my WB would register a 16-16.5 AFR and the mpg gauge would show an instantaneous mpg at 27-32 depending on the speed. That's on a Xfire with 3.45 gears running at about 1800rpm.

Guest

The ethanol blend would have been something 10% or less. Knowing oil companies and that they can make more off ethanol sold as gasoline its right at 10%.

PLANT PROTECTION

iTrader: (6)

Pumps around me say 'Contains 10% ethanol'.

Grim Reaper

Back to the original post as I have always been keen on maximizing gas mileage...

RBob, does your car also use the "cycling" of lean/normal to help protect the cats?

I found that my best gas mileage (on my SD L98 when basically stock) was with a commanded AFR of 17.2:1 and 47* of spark advance. I also disabled the "cycling on/off" time to keep it constantly working.

I had no ill effects to my cats with a number of years usage BUT I will also add that I live in a mountainous area so there is a constant cycling anyway. But, I did take a couple of trips to Alberta & Saskatchewan (where it is as flat as billiard table) and had no ill effects either. Also, I installed a couple of copies of my bin on few other guys with SD L98s who did live out there and they too experienced similar increases to their fuel economy.

The biggest problem I found with running this setup: you MUST constantly clean the distributor cap. The large spark advance produces a wide arc trace that over time will build up. Removing the distributor cap and cleaning it the terminal contact and rotor tip on a regular basis (every couple of months) fixes that.

RBob

iTrader: (1)

I set highway mode up so that it drops out every so many minutes. I do this so that the BLM may adjust. Then stay in closed loop for so much time, and revert back to highway mode.

Interesting about the cap & rotor. If the base timing can be advanced it would help. It just may be time to do the CnP setup.

RBob.

Cflick

Hmmm.....
Found something similar a while back.
Drilled holes in the cap, so I could see where it was when it sparked.
That's how I determined my original static advance.
Looking back, I'm very, very close static to where the rotor aligns with the post most of the time ( averaged spark advance over time ) and the engine likes it much better than the GM specified zero.
I'm at 10, and the block originally ( mechanical dist ) called for 10. Imagine that !

So, Grim, why is it that you haven't simply phased the dist for the curve ?

junkcltr

iTrader: (1)

Maybe this doesn't apply, but since it is a MPG topic then I will put it out there. Mods, please remove if you don't think it fits the forum/thread.

I retired the car as a daily driver. I now get 78+ MPG city, 72+ MPG highway. Both are at stoich. so I am not polluting the air we all breathe with NOx. Top speed is 105 MPH and 1/4 mile time is 14.6 sec.

Driving the turbo car I get over 20+ MPG. I only drive that when I want to do 12 second runs.

Alternative transportation is the future if one wants MPG and clean air.

Grim Reaper

Junk, we probably all should start using a bicycle, walking or taking public transit more often; if only to reduce foreign oil consumption, improve our health and reduce pollution. However, you are right, it is off-topic from RBob's original post, and doesn't really add anything on how to improve fuel economy on a 3rd Gen F-body.

Cflick, I did all my experimenting trying to increase fuel economy back over 6 years ago when gas was still cheap and people weren't that interested in Highway Mode. In fact, the proper way to invoke the HM Switch wasn't yet known and I had to make a physical code change to get Highway Mode to work at that time.

I then modified my engine (heads, cam & Miniram) back in 2002; so HM no longer would work the same (as I had no EGR). And for the last couple of years the GTA has been collecting dust while I wait to either rebuild the engine (or install a crate engine). Unfortunately, the GTA is low on my priority list these days as I am suffering a serious neck injury and waiting for surgery before I can do any work on my car. As well, we subsequent got out of the condo and bought a 2 car garage with an attached house...and that has been swallowing a lot of time (and cash).

RBob, I did think about raising the base timing to just below the "lowest" SA in the Main Spark Table (while I was running the basically stock setup). But I thought that if I ever needed "safe mode" or worst, "limp mode" that I may effectively disable it. CnP wasn't available yet; but that is most definitely the best answer, and could help improve mileage even more.

I realize your engine is a 3.1, but it would be interesting to see how it would respond if you tried the same parameters as I used in my L98. Jeremey was going to try one of my later bins (before I modified the engine) that has my Highway Mode parameters close to the one where I got my best mileage (30 US MPGs) and that was driving from Kamloops BC to Calgary Alberta (almost 400 miles) and I used just over 13 US Gallons (a little over 50 litres).

One thing I did forget to mention in the specs, I also set the minimum speed where Torque Convertor was prevented from unlocking set to around 45 mph. If I think of anything else, I'll mention it.

I'm just glad that people are finally looking at Highway Mode/Lean Cruise seriously; plus other means to improve fuel economy on 3rd Gen F-bodies.

Cflick

Or is it ?
If one is in persuit of the ultimate milage machine, then I'm all for off the wall ideas, no matter how impractical they may at first appear. Junk is claiming 78+ MPG city. Fine. The hyper-milers do even better. I think the most recent contest, the winner was something like 165 MPG average, but the way they drive is totally impractical, and unsafe in many ways, like turning off the engine altogether during hiway coast.
Still, 78 MPG city and 72 MPG hiway got *my* interest, if true, even if totally impractical.
That's more than twice RBob's numbers. How ?

Again, which ECM ?
Though I knew about hiway mode as far back as about 1987 or so, I knew nothing more than that it existed, and have been persuing a workable hiway mode ever since. Details are still lacking, which is why I'm still interested in your parameters. Why reinvent the wheel you already had rolling ?
That's why I ask about your numbers. How lean, and where in the operating range ? How much difference in timing in hiway mode, and at where in the range ?
You speculate that others would probably end up close, and I'd like to spend the next few months proving, or disproving that theory rather than reinventing the same parameters.

Possibly a key bit of info, that !??
Does ( did ) EGR affect lean cruise in ways that would seem obvious ? ( more advance, for instance ) Or, does/did EGR simply help, or hurt, or have no real affect on the final outcome ?

Definitely off topic, but get well soon just the same.

An alternative, maybe, that worked for me, although with a VERY narrow range application.
It's not that tough to modify a rotor. Soldered a tab to the fire end to broaden it a bit.
Practical ? Maybe, but REALLY makes the limits critical.
Useful as a tuning tool, though not good as a routine part on a daily driver.

YES !!

And, I'm gonna ask again for the relevent portions ?

For me, I'm thinking that what applies to one, will apply ( at least in part ) to all, even a lawn tractor !
There is still data missing. Things like, excluding wind resistance, but using the typical theoretical maximum efficiency possible from an internal combustion engine, how much is the minimum amount of gasoline needed to push a pound of steel down the road ?
We know, for instance, that we're interested in pushing the pistons by burning gas.
We know that there is so much energy in a particular volume of gas.
There should be a way to subtract the heat energy from the volumetric expansion of the burning gas, and know a theoretical percentage of what is available to move parts, and how much WILL simply go out the tailpipe as waste heat.

Practical numbers should be out there somewhere. If they are, PLEASE point me ( us ) at them. Numbers like, assuming an engine runs at a constant 80% power at its torque peak, and assuming at equalibrium it's pushing steel down the road, the fuel consumption, torque, and RPM there should be a fairly simple formula that will determine the absolute maximum milage possible.
If, for instance, RBob is running at 5% of thoretical, there's likely much yet to be gained, but if he's running at 95%, likely there isn't.
It seems that this single bit of data would be invaluable to anyone chasing reducing all of the effects ( whether green, or simply financial ) of burning fuel.
To me, and probably a few others, this may be the most valuable thread on the whole site !

RBob

iTrader: (1)

Motorcycle.

RBob.

RBob

iTrader: (1)

I also run highway mode in the El Camino, it has an '85 Camaro LG4 motor in it converted to TBI. Lean cruise does make a difference. However, I don't drive a lot of highway in it, so there isn't any solid numbers on how much of a gain there is.

EGR is interesting. Some folks claim a MPG gain while running EGR, others claim that is is 'possible' to gain MPG, while others can't get any MPG gain from running EGR. The theory is that EGR reduces pumping losses, thereby increasing efficiency.

For technical information on lean cruise the aviation world is the place to go.

RBob.

Grim Reaper

Cflick, if you read a few posts back, I mentioned it was a "basically stock SD L98". As for "other engines like lawnmowers etc", this is a 3rd Gen F-body site and technically, ANYTHING not dealing with a 3rd Gen F-body (or applies to a 3rd Gen F-body) is to be closed or deleted. I don't think anyone SERIOUSLY thinks Junk's mileage was a 3rd Gen. RBob's comment motorcycle/scooter is the most likely and what immediately came to my mind; and they DO NOT apply to this site or forum.

As for all your other comments about wind resistance etc. Who cares? We may as well make the same comment when talking about drag racing. We are just a bunch of hobbiests with limited funds. We are not GM with billions of dollars for R&D. I base my comments on approximately 100,000 miles of driving done over a couple of years on typically the same round trip of 300-400 miles in a variety of weather at all times of the year.

For the me (and most of the guys who post on this site) we are looking for practical info that is repeatable by EVERYONE. If you are looking for more technical and scientific research, you are on the wrong website.

On DIY Prom we are allowed to be a bit "looser" and permit tuning info on other GM systems (most tyically Corvettes) as they work on 3rd Gens. But, when people come here requesting info on tuning other Auto manufacturer's ECM/PCMs (non-GM), I usually send them a polite PM informing this is a 3rd Gen F-body site and those posts are not permitted (and usually end up orphaned). This rule is per the request of the Administrators & Owners of this site and has been enforced since this site began.

So let's keep the keep the posts related to tuning on GM ECMs (as required) and not get the posts "off-topic" or "hi-jacked". My comment (which you quicly state is off-topic) about my car and neck injury was to point out that I am not in any position to do anymore testing or research on this area. If you do some searching, you can find a lot of my posts on Highway Mode about 5-6 years ago where I discuss a lot more in detail - but few were interested and I stopped posting my findings. Every now and then, someone digs one of them up and I try to answer them (if I'm around, but I don't do that often anymore due to health and limited time).

RBob, I believe the EGR was instrumental. On a buddy's car who had a Miniram, we were not able to run Highway Mode (except on nearly stoich settings) as it caused driveability issues. Anything close to 16:1 was just not nice. You also make a point too, that Highway Mode is actually "open loop". In one of my old posts, when I first tried to invoke HM; I found that you MUST have your tune "bang on" before invoking HM or you actually can worsen your mileage with HM. It was only after I worked for months on my VE Tables getting my tune right that I was able to invoke HM and get those resuls.

I tried to keep the EGR functioning as LONG as possible as the area I live is just one hill after another. Also, I made some minor code changes to engage the EGR as quickly as possible (as well as locking the TC as quickly as possible).

I believe my "city mileage" also made quite a gain based on my "overall/mixed increase mileage readings". Though it was a bit tougher to measure as I didn't have too many times where I drove a tank's worth of gas in "pure city".

Craig Moates

I've been getting better mileage on my vehicles, one of which is a 3rd gen F-Body, since I retuned the fueling tables to lean it out a bit.

This was especially helpful at part throttle and deceleration. Both MAF and SD setups would respond to this sort of recalibration.

Having quick feedback during this effort is crucial, and RBob's EBL and the new EBL Flash are a great way to get it along with some very special custom code for improved fuel management.

junkcltr

iTrader: (1)

The data I posted was from a motorcycle. I figured some DIYers would be interested in data from a fuel consumption point of view. That was also using 87 octane E10 fuel. Straight 87 octane gas had an average of about 82 MPG.

For the SD ECM, I take in the WBO2 signal. Then in the code I invert the value and subtract off a 2-D table value to make it look like the NBO2 value. Shortly I am going to remove that and make some new AFR vs map vs rpm tables using just the straight WBO2 so that I can run closed loop all the time and have a closed loop AFR table that is tunable. This will improve MPG.