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Thread: Add Highway mode to LT1

  1. #31
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    Quote Originally Posted by LeMarky Dissod View Post
    LT1 Swap to LS 411 pcm

    Although the video is 32min long for some reason, the gist of it is:
    he converted his OBD1 LT1 into an OBD2 LT1 with a 96/97 front timing cover and added wiring for the OBD2 crank sensor
    he repinned his harness into an 0411 pcm
    he basically runs his OBD2 LT1 as an OBD2 L31

    Of note, both the L31 & the LT1 both need only one coil to run.

    In terms of inputs and outputs between the pcm and either engine, the distinctions between an OBD2 L31 and an OBD2 LT1 lack any meaningful differences.

    Can't think of a cheaper way to use an 0411 pcm to run an LT1 - even though I'm not as imaginative and resourceful as y'all.

    That said, if an OBD1 LT1 pcm can be coerced into reliably exceeding 29 highway MpG in an LT1 Caprice Roadmaster or Fleetwood without hypermiling, I'll be impressed regardless of how it's achieved, in inverse proportion to the cost, and not just because it would be novel.
    It's neat, but it runs batch ignition, and you still need OBD2 interface software and hardware to mess with it. The hardware you could just make with parts if you had to (though personally, my attempt to do so with the OBD1 didn't go well, thus my $70 cable), and while flashing software that is free-as-in-beer is finally starting to materialize as of this year, it's very much prototype stuff and they warn you about that up front. Once that materializes, it'll make the OBD2 PCMs much more attractive.

    That all said, yeah. It's still worth looking at the OBDI PCM. I wouldn't count it out so fast.

  2. #32
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    Hey guys, the author here. So I see we have run off topic hard here. Let's start with why I am looking for this feature, it's my daily driver. I started looking at options when I enabled it on my L98 corvette and noticed a 2mpg increase in combination driving.

    Stevo you asked about me just settings g the afr to 15.3. Yes I did to see if there would be any gains, there where not. The car starts up drives down my road and its highway speeds all the way to work so this was just a test.

    For those recommending the LS style ecu, forget it. I have a MS3 unit sitting on a shelf I can throw in for pennies. I was just trying to see what can you get from a stock ecu.

    Stevo if you decide to pursue a highway cruise patch I'm more than willing to test it for you.

    Kuro if you have any tips for increasing my mpg I'm all ears from the more experienced.

    Thanks everyone for the input.

  3. #33
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    Quote Originally Posted by space387 View Post
    Hey guys, the author here. So I see we have run off topic hard here. Let's start with why I am looking for this feature, it's my daily driver. I started looking at options when I enabled it on my L98 corvette and noticed a 2mpg increase in combination driving.

    Stevo you asked about me just settings g the afr to 15.3. Yes I did to see if there would be any gains, there where not. The car starts up drives down my road and its highway speeds all the way to work so this was just a test.

    For those recommending the LS style ecu, forget it. I have a MS3 unit sitting on a shelf I can throw in for pennies. I was just trying to see what can you get from a stock ecu.

    Stevo if you decide to pursue a highway cruise patch I'm more than willing to test it for you.

    Kuro if you have any tips for increasing my mpg I'm all ears from the more experienced.

    Thanks everyone for the input.
    Have you altered the 02 sensor target volate in the area you are trying to acheive 15.3:1. At low loads above idle I am running at 15:1 in closed loop. Stoich value on the fuel is 14.1. Instead of the stock 0.450 volt target I am down around 0.325 volts.

  4. #34
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    Quote Originally Posted by Fast355 View Post
    Have you altered the 02 sensor target volate in the area you are trying to acheive 15.3:1. At low loads above idle I am running at 15:1 in closed loop. Stoich value on the fuel is 14.1. Instead of the stock 0.450 volt target I am down around 0.325 volts.
    No I have not. That realization came last night and with my work schedule I have not had time to alter the tune.

  5. #35
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    i wouldn't really change the switch point in EE, i don't think you'll gain much except an unstable closed loop.

    'leaner is better fuel economy' is only true in narrow operating bands like extremely light loads

    outside those bands removing fuel can reduce your power enough that you negate the gain.

    the point of highway lean cruise is to find the conditions where load is light and having optimal torque isn't helping....then lean it out. that's the 'highway' and 'cruise' part of 'highway lean cruise'. running leaner all the time isn't really highway lean cruise, it's just lean, and that's just bad tuning.

    on my own cars i'd tend towards a hair more fuel than stoich in most cruse conditions above coasting. pennies a day for a smoother running engine is worth it.

  6. #36
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    Quote Originally Posted by steveo View Post
    i wouldn't really change the switch point in EE, i don't think you'll gain much except an unstable closed loop.

    'leaner is better fuel economy' is only true in narrow operating bands like extremely light loads

    outside those bands removing fuel can reduce your power enough that you negate the gain.

    the point of highway lean cruise is to find the conditions where load is light and having optimal torque isn't helping....then lean it out. that's the 'highway' and 'cruise' part of 'highway lean cruise'. running leaner all the time isn't really highway lean cruise, it's just lean, and that's just bad tuning.

    on my own cars i'd tend towards a hair more fuel than stoich in most cruse conditions above coasting. pennies a day for a smoother running engine is worth it.
    With an over powered V8 anything the engine is more efficient with less intake vacuum. Meaning the throttle plate is more open. If you have adequate torque even during light throttle acceleration leaner will give better mileage. The OEMs are doing it these days with cylinder deactivation. Hence the turbo 4 cylinder silerado that runs on 2 cylinders.

    My 11:1 383 runs and accelerates smoothly at 16.5:1. I pulled the plugs at 5K to read them. They are carbon amd deposit free. Much cleaner than anything running at stoich.

    I am getting 14 in town and 18 on the highway in a 6,200 lbs Express van with a near 500 hp 383, 1-ton running gear, a 4L85E and 5.13 gears on LT265/75R16s

    If you drive as much as I do it is more than pennies a day. My round trip is 120 miles. Going from 16 mpg to 18 is a BIG difference at the end of the week.

    Then again my 4 cylinder/6speed 2014 Nissan Sentra went from 35 mpg to 40+ when I tuned it. It is usually the vehicle of choice.
    Last edited by Fast355; 1 Week Ago at 10:52 PM.

  7. #37
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    I don't think you're really getting it...or maybe both of you are actually making the same point but for different reasons.

    It was actually touched upon in the video series linked all the way back in the beginning of the thread. There is a specific amount of power required for maintaining steady-state speed of any vehicle. As long as you remain at or above that power, you're golden. So if you don't need any more fuel to hit that power level, you can lean it out and be just fine and dandy. Likewise, you can remove cylinders from the equation and be fine and dandy (what OEMs realized recently). Leaning things out above that load, however, not so fine and dandy (which is why OEMs reenable cylinders once you exceed a specific load value). There are lots of factors involved, and no engine is the same since each is going to have different dynamic compression, peak torque values, control systems, etc. But at the end of the day, if you only need 50 HP to cruise at 65 MPH, you don't need 300 HP worth of fuel.

  8. #38
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    So I have decided to attack this a little more scientifically than just lean it out until I see improvements. So I recorded the car driving down a strait road with stock settings and recorded the engine telemetry. There are 2 factors to watch to directly show if you have achieved tangible improvements, MAP or MAF and injector pulse width. If you can lean the engine out without increasing the MAP or MAF readings then it is not taking more volume to maintain the same speed. You can then show a decrease in fuel use by the injector pulse width. If all this is done at the same RPM and along the same stretch of road the results should show some improvements.

  9. #39
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    Quote Originally Posted by space387 View Post
    So I have decided to attack this a little more scientifically than just lean it out until I see improvements. So I recorded the car driving down a strait road with stock settings and recorded the engine telemetry. There are 2 factors to watch to directly show if you have achieved tangible improvements, MAP or MAF and injector pulse width. If you can lean the engine out without increasing the MAP or MAF readings then it is not taking more volume to maintain the same speed. You can then show a decrease in fuel use by the injector pulse width. If all this is done at the same RPM and along the same stretch of road the results should show some improvements.
    Actually you want the MAP and MAF to increase. You just want less pulsewidth. More throttle, More Airflow, Less fuel, Less Torque production, Less pumping loss and more MPG.

  10. #40
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    For fuel economy thera are 3 parameters that are related, pulse width, rpm and mph. PW and rpm must be as low as possible and mph as high as possible.
    We are still missing that INS.Fuel .Economy in eehack. I hope steveo will add it on the next release. If we have that available in the datastream, high end experiments will prove what is needed.

    If the engine torque is not efficiently transformed to rolling movement, due to high gears for example, there is a waste of fuel for sure. So lets say the engine makes 100% power and only 70% of the power is used to drive the vehicle, the other 30% are wasted.
    One way of improvement will be to lower the gears so the load the engine make can be utilized 100% to movement. Increasing the speed while maintaining the same load on the engine.
    It will get alot of trial and errors to get the best combo of gears, weight and engine torque curve.

    The other way of improvement will be to lean the mixture so the engine makes less power but enough to be used 100% for vehicle movement.
    With really high gears, low weight vehicles going to 18-19:1 even 22:1 AFR can be beneficial.

    To sum up lean cruise will work best on high torque, high gears vehicles.

    To get a better fuel economy a general engine tune up can be performed.
    Full revision of ignition system.
    Internal engine cleaning of carbon deposits. A fine water mist method works good and can wake up poorely maintained engines.
    Checking injectors for leaks and clogs.
    Switching all oils to full syntetic like redline.

  11. #41
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    Quote Originally Posted by kur4o View Post
    For fuel economy thera are 3 parameters that are related, pulse width, rpm and mph. PW and rpm must be as low as possible and mph as high as possible.
    We are still missing that INS.Fuel .Economy in eehack. I hope steveo will add it on the next release. If we have that available in the datastream, high end experiments will prove what is needed.

    If the engine torque is not efficiently transformed to rolling movement, due to high gears for example, there is a waste of fuel for sure. So lets say the engine makes 100% power and only 70% of the power is used to drive the vehicle, the other 30% are wasted.
    One way of improvement will be to lower the gears so the load the engine make can be utilized 100% to movement. Increasing the speed while maintaining the same load on the engine.
    It will get alot of trial and errors to get the best combo of gears, weight and engine torque curve.

    The other way of improvement will be to lean the mixture so the engine makes less power but enough to be used 100% for vehicle movement.
    With really high gears, low weight vehicles going to 18-19:1 even 22:1 AFR can be beneficial.

    To sum up lean cruise will work best on high torque, high gears vehicles.

    To get a better fuel economy a general engine tune up can be performed.
    Full revision of ignition system.
    Internal engine cleaning of carbon deposits. A fine water mist method works good and can wake up poorely maintained engines.
    Checking injectors for leaks and clogs.
    Switching all oils to full syntetic like redline.
    I was assuming same RPM and Speed. Lower pulse width equals more MPG. Less vacuum means the engine is using less of the power it makes just to pull the pistons down against the vacuum. More throttle for the same power is giving it more volumetric efficiency.

    I had a Ram that had 3.55 gears and a MDS Hemi in it. When I put 4.56 gears the fuel mileage improved. The truck spent much more time shut down to 4 cylinders. When I put a cam and converter in it stayed in 4 even more. When I opened up the exhaust and intake it almost always ran in 4. The PCM judged when to go into MDS mode by monitoring vehicle speed, rpm and load via the MAP sensor. Over idle, over 20 mph and under X vacuum amount it went to 4 cylinder. With the small cam it made more torque. With the gears and converter the engine ran and accelerated with less load. It would pull into 4 cylinder mode accelerating up an on-ramp.

    FWIW an internal combustion engine is only about 30% efficient and even less efficient at part-throttle.
    Last edited by Fast355; 1 Week Ago at 03:44 PM.

  12. #42
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    Quote Originally Posted by Fast355 View Post
    More throttle for the same power is giving it more volumetric efficiency.
    As much as I hate to agree with Fast355, he is correct. My daily driver regularly gets 49+ mpg because it's a diesel and has no throttle plate, which causes far less pumping loss than an equivalent 1.9L gasser.

    The trick with lean cruise strategy is proper tuning. You can't run at 15.4:1 (or equivalent adjusted for fuel stoich) all the time - not even "a lot" of the time. But maintaining speed while going down a hill at 75mph takes a much smaller amount of power than doing the same going up said hill. Coupled with well-tuned DFCO and perfectly tuned stoich combustion with MBT spark, I believe impressive numbers can be made with an over-powered V8 in a light and aerodynamic car.

    "Hypermiling" isn't an evil word. Waste not, want not. I look at it this way - I'm all too happy to bank my unused hydrocarbons while driving conservatively so I can gluttonously consume them in the six or eight times a year I get to exit my favorite hard right corner with tires smoking at 80+ mph in 3rd.

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    Quote Originally Posted by spfautsch View Post
    As much as I hate to agree with Fast355, he is correct. My daily driver regularly gets 49+ mpg because it's a diesel and has no throttle plate, which causes far less pumping loss than an equivalent 1.9L gasser.

    The trick with lean cruise strategy is proper tuning. You can't run at 15.4:1 (or equivalent adjusted for fuel stoich) all the time - not even "a lot" of the time. But maintaining speed while going down a hill at 75mph takes a much smaller amount of power than doing the same going up said hill. Coupled with well-tuned DFCO and perfectly tuned stoich combustion with MBT spark, I believe impressive numbers can be made with an over-powered V8 in a light and aerodynamic car.

    "Hypermiling" isn't an evil word. Waste not, want not. I look at it this way - I'm all too happy to bank my unused hydrocarbons while driving conservatively so I can gluttonously consume them in the six or eight times a year I get to exit my favorite hard right corner with tires smoking at 80+ mph in 3rd.
    I run leaner than 16:1 ALOT of the time. Even light throttle acceleration.

    In WW2 it became common for planes like the P38 to run with the propellor pitch at maximum advance, a lean cruise mixture and moderate manifold pressure. Basically low rpm, lean and higher load. When a brilliant pikot aka Charles Lindberg first attempted it the ground crew thought he was nuts. They examined the engines after 500 hours and determined their were no ill effects.

    On a LS I run as lean as 16.9:1. On the older SBC I run 16.5:1
    I run my 8.1 in my Tahoe at 16.5:1 as well. The chamber design better on the LS.
    Last edited by Fast355; 1 Week Ago at 08:21 PM.

  14. #44
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    Here is the basic run down of the P38 story.

    For some real world, historical reference here is an excerpt from an article about Lindberg 's briefings about P-38 long range cruise power settings. *Interesting reading.....

    "Two missions later, on 3 July, the group covered sixteen heavies on a strike against Jefman Island. Lindbergh led Hades Squadron's White Flight as they wove back and forth above the lumbering B-25s. After the attack the Lightnings went barge hunting.

    First one, then two pilots reported dwindling fuel and broke off for home. MacDonald ordered the squadron back but because Lindbergh had nursed his fuel, he asked for and received permission to continue the hunt with his wingman. After a few more strafing runs, Lindbergh noticed the other Lightning circling overhead. Nervously the pilot told Lindbergh that he had only 175 gallons of fuel left. The civilian told him to reduce engine rpms, lean out his fuel mixture, and throttle back. When they landed, the 431st driver had seventy gallons left, Lindbergh had 260. They had started the mission with equal amounts of gas.

    Lindbergh talked with MacDonald. The colonel then asked the group's pilots to assemble at the recreation hall that evening. The hall was that in name only, packed dirt floors staring up at a palm thatched roof, one ping pong table and some decks of cards completing the decor. Under the glare of unshaded bulbs, MacDonald got down to business. "Mr. Lindbergh" wanted to explain how to gain more range from the P-38s. In a pleasant manner Lindbergh explained cruise control techniques he had worked out for the Lightnings: reduce the standard 2,200 rpm to 1,600, set fuel mixtures to "auto-lean," and slightly increase manifold pressures. This, Lindbergh predicted, would stretch the Lightning's radius by 400 hundred miles, a nine-hour flight. When he concluded his talk half an hour later, the room was silent.

    The men mulled over several thoughts in the wake of their guest's presentation. The notion of a nine-hour flight literally did not sit well with them, "bum-busters" thought some. Seven hours in a cramped Lightning cockpit, sitting on a parachute, an emergency raft, and an oar was bad, nine hours was inconceivable. They were right. Later, on 14 October 1944, a 432nd pilot celebrated his twenty-fourth birthday with an eight-hour escort to Balikpapan, Borneo. On touching down, he was so cramped his crew chief had to climb up and help him get out of the cockpit.

    The groupís chief concern surfaced quickly, that such procedures would foul sparkplugs and scorch cylinders. Lindbergh methodically gave the answer.*The Lightning's technical manual provided all the figures necessary to prove his point; they had been there all along. Nonetheless the 475th remained skeptical. A single factor scotched their reticence.

    During their brief encounter, MacDonald had come to respect Lindbergh. Both men pushed hard and had achieved. Both were perfectionists never leaving things half done. And both had inquisitive minds. John Loisel, commanding officer the 432nd, remembered the two men talking for long periods over a multitude of topics beyond aviation. If, as MacDonald had informed his pilots, better aircraft performance meant a shorter war, then increasing the Lightning's range was worth investigating. Lindbergh provided the idea, but it was MacDonald's endorsement, backed by the enormous respect accorded him by the group, that saw the experiment to fruition. The next day, the Fourth of July, Lindbergh accompanied the 433rd on a six-hour, forty-minute flight led by Captain "Parky" Parkansky. Upon landing, the lowest fuel level recorded was 160 gallons. In his journal entry Lindbergh felt ". . . that the talk last night was worthwhile. " The 475th had lengthened its stride."

  15. #45
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    what works for one engine won’t necessarily work for another. comparing this airplane engine to an lt1 highlights the total absurdity of your generalizations both here and elsewhere. combustion chambers flame fronts and air fuel charge dynamics are an insanely complex thing with so many inputs and outputs and that’s why tuning is required in the first place. lots of engines melt down when lean, and lots can run 25:1+. lots of factors involved.

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