Triple challenge

Discussion in 'Start Your Journey Here' started by SentraSE-R, Dec 1, 2008.

  1. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Glad to offer something useful. :)

    Hopefully you'll have that offset problem fixed now with the new cutoff level on the SG? I know my Elantra showed some really high numbers when I got the SG-II (my other one is a SG-I and doesn't have a fuel cutoff adjustment at all) so I quickly adjusted it to zero and the numbers went back to normal. My first clue was seeing the instantaneous jump to 9999 at the top of a pulse as soon as I let off the pedal to start my coast.

    Good luck and keep us posted!
  2. SentraSE-R

    SentraSE-R Pishtaco

    Thanks again Sean,

    I'm probably going to make a run over to Reno later this week, to use half a tank practicing hypermiling techniques, and to calibrate my SG. On the way back, I hope to crack the 50 mpg barrier on my 180 mile drive. If I could do 45 mpg with cruise control during the summer, I should be able to top that by hypermiling in the winter, right?
  3. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    On the highway? Possibly with sustained P&G. If you want to try it, high speed P&G is pretty tricky so you have to keep an eye on the current trip average. Concentrate on making sure that the end of every coast leaves you with a higher average than the end of the previous coast. You might want to just use NICE-ON for a while when practicing? My Elantra ECU has a really long reboot time... sometimes as long as 7s. Because of this there are few things to keep in mind when FASing...

    The last thing the SG sees in terms of fuel usage rate is what it will keep using during a reboot until it starts receiving data again. What this means is that if you cut the engine right at the end of a pulse you may only have an instantaneous reading of 17mpg. Until the ECU comes back online, the SG will continue computing using your last known speed and fuel usage... so for a matter of seconds it will hold onto the 17mpg readout pulling your average down (at least I hope that would pull your average down!!! :eek:). To work around this, let the RPM die down to something close to idle speed. The instantaneous will go to a much higher number for the duration of the reboot and you'll also be able to reduce the time of the key off event without causing the engine to diesel back to life. Using NICE-ON avoids this issue altogether and at highway speeds, the difference between FAS and NICE-ON isn't nearly as great as at city speeds -- so I only use FAS for long distance glides on the highway in the Elantra and it is still worth 57mpg or so.

    As for the cold, you'll be able to counteract it somewhat with hypermiling. What are your average temperatures right now?
  4. SentraSE-R

    SentraSE-R Pishtaco

    Temperature is 46ºF today, supposed to hit mid 50s the next couple of days.

    I'm re-reading the Scangauge forums, and the people are saying to set cutoff to 1 over the idle TPS, not 4 over like the SG manual says. Is that what you advise?
  5. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    If you saw 45mpg at those temps with CC, 50mph is very doable. :)

    Try it at 1 over and see if you get fuel cut showing 9999 as it should. You should see it when the engine is warmed up and you've got engine braking with the RPM over 1100. If you don't see it, raise the value by one. Try it again. Keep going through the cycle until you see it when you should.
  6. SentraSE-R

    SentraSE-R Pishtaco

    Thanks Sean,

    I'll try the cutoff at 2, and adjust it if necessary. I've been driving with my SG set at a cutoff point of 24, so I'm used to seeing it show 9999 mpg whenever I ease off the gas pedal. It's going to be a shock to me to see what my real-time mileage really is. I can rationalize that my 40-50% calibration figures are there to offset the artificially inflated 9999 mpg times. So i expect to see higher mpg ratings in normal driving, but a lot less of those 9999 mpg times. The former will be nice but the latter will disappoint me. I'm not sure if my test route figures will rise significantly now, stay about the same, or even go down. As I said, the miscalibrated SG estimated my highway tank mileage pretty well, but overestimated my around-town tank mileage That's not too encouraging, as I might see worse in-town mileage on the correctly calibrated SG

    I was probably being far too optimistic in hoping for an 11% improvement over my already-excellent freeway mileage, in colder winter weather, when I still haven't perfected any hypermiling techniques. My revised goal is just to try hypermiling techniques, learn their effects on mileage, and see what improvements I get.
  7. SentraSE-R

    SentraSE-R Pishtaco

    Today I drove to Reno (actually to Verdi) and back, doing real world hypermiling. I didn't high speed P&G, but I slipstreamed trucks and FASed a lot. The coast down into Verdi from Truckee is nearly 20 miles. There's even more coasting on the way back, and my trip mileage reached an indicated 75 mpg at one point, 80 miles back from Verdi!. My uncalibrated SG showed 50.8 mpg driving over, and 65.1 mpg coming back. Calibration offset ended up at 26.8%, and actual mileage was 45.2 mpg overall (350 miles on 7.75 gallons.). I got 53.6 mpg on the return trip, better than my wildest expectations.

    My car has an original EPA combined mileage estimate of 26 mpg. I got >200% of the EPA estimated mileage on the return trip of 163 miles.

    Last edited: Dec 11, 2008
  8. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Very nice!

    DON'T "slipstream" trucks -- it is incredibly dangerous and won't benefit you as much as many other techniques will. :(

    Work on some HS P&G and you should see even better numbers.
  9. SentraSE-R

    SentraSE-R Pishtaco

    I slipstream one lane over from the big rigs, about 2 car lengths back. I know from motorcycling, that my 90 cc bike would get sucked up to 70 mph in that area. Once it dropped back to drafting distance of 2 seconds back, the calm air advantage was nowhere near the sucking that occurred within 2 car lengths, and I'd drop back to my normal wide-open throttle speed of 55 mph.

    The next lane is arguably dangerous, if the truck shifts lanes and closes that escape route.

    I did a survey of pack cars passing my big-rig/SE-R combo when I dropped two seconds back waiting to get back into the slipstream. Fully 75% of the pack is tailgating the guy in front of them, with less than a 2 second safety margin. Several times, you could have squeezed THREE pack tailgaters in the space between me and my big rig!
  10. SentraSE-R

    SentraSE-R Pishtaco

    My SG fuel cutoff monitoring didn't trigger very often when set at 2, even though I could see the TPS down at 1 (idle). My SG instantaneous mileage showed values around 113-180, rather than 9999. I know my Sentra does shut down its fuel injectors with an open loop/idle combination. I'll set the SG fuel cutoff monitoring value to 5 tomorrow (idle TPS +4, per the manual).
  11. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    If you are traveling within 3 car lengths at highway speed, that is WAY too close. Minimum safe following distance is 3s. At 60mph that is 264' in that time period. Your car is 177.5" so that works out to 18 car lengths. If you are traveling at 3 car lengths from the truck you are only allowing 1/2s following distance! :eek:

    Dude. It isn't safe. Don't do it. The faster you go the worse the numbers look. At 70mph the minimum following distance for your car should be 21 car lengths and 3 car length following distance is only 0.4s of separation. You CANNOT react quickly enough at those speeds. Your life is entirely dependent upon your accurate prediction of other people's actions and you are seriously limiting your visibility of the travel conditions (especially if you are following a semi) you need to know about for safe reaction time. One panic stop or piece of road debris thrown by a tire is all it would take to end everything for you.

    Please reconsider.
  12. SentraSE-R

    SentraSE-R Pishtaco

    I hear you, Sean. I don't mean to be argumentative, but I disagree with you.

    I'm not denying there's some risk involved, but I'm in the next lane over, with a clear view ahead of me. I'm not blindly following the semi 2 car lengths back. When I follow, I stay at least 2 seconds (176' @ 60 mph) behind. That gives me a .5 second reaction time (44') + my 125' stopping distance to stop within my 2 sec. following distance, and we all know a semi takes about 450' to stop at 60 mph.

    If it's that dangerous to be close to a vehicle in an adjacent lane, none of us should ever pass anybody, because it brings us within 3 car lengths of the other vehicle.

    My reaction time was .11 sec when I was 15. Studies show it slows to about .5 sec by the time you're my age (60+). I found a simple reaction time applet that indicates my reaction time is still pretty good, about .18-.19 sec. At 60 mph, my car will still travel 16.72' (about one car length) before I can respond, but it's not as bad as you think.
  13. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Possibly not, but why live on the edge? Especially when you note that an unloaded semi can stop much faster than you'd think? And what about evasive maneuvers by the driver to avoid something in the roadway you can't see because you are too close? I darn near had my hood taken off by just such an event as I was coming up to pass a semi. I saw a flash of taillights and suddenly this huge bar was 2' in front of my bumper and high enough to clear 1/3 of my hood before hitting metal.

    Why take the chance? I thought 1 lane over was safe too -- until that happened. Tire blowouts and large debris thrown by semi tractors have also been known to cause serious damage to vehicles and people. At the distances I noted the debris usually won't still be airborn by the time you reach it and you'll have plenty of time to steer around it. 2 car lengths off? Not so much.

    You are going to do what you are going to do, and habit tends to breed comfort, but I urge you to reconsider. I'll leave it at that.
  14. SentraSE-R

    SentraSE-R Pishtaco

    No disagreement there about following too closely. I had a semi toss a 5" wide rock at my windshield from between its rear tires, on a downtown freeway (in L.A. or Phoenix). The rock hit about rear-view mirror level, between my wife and me.

    Another time, I was following a pickup truck on a Bay Area freeway, when he hit a bump and a ladder bounced out of his bed. The ladder ended up straddling the entire lane. I was planning to pass him, anyway, so I knew my right lane was clear, and I swerved around the ladder. The two cars behind me drove right over the ladder - OUCH!

    I can think of many other examples of watching people hit box springs, sheet metal, dodging deer, watching boxes fall on the roadway, etc.

    Basically, when there's flying/falling debris on the roadway, it's anybody's guess where it's going. You can see it, and slow down, but you might still hit it anyway. If you jam on the brakes in Bay Area traffic, you're going to cause an accident, and likely get rear ended. Sometimes it's better to hit the debris.
  15. AlphabetBackward


    I hate the traffic in San Francisco. Bay Bridge is awful; Golden Gate not too bad.
  16. SentraSE-R

    SentraSE-R Pishtaco

    I know it all too well, and totally agree. I drove backup in a 15 passenger vanpool for several years, traveling from the city back to the north bay - about 33 miles. We'd leave the city at 4:45 p.m., and usually got home about 5:35-5:45. About once a year, everything went perfectly, and we'd hit the toll gates at the Carquinez bridge at 5:13 or 5:14. More often, there'd be a problem, and the clocks on the bridge would read 6:30 before we arrived.
  17. SentraSE-R

    SentraSE-R Pishtaco

    I dug up all the old gas records I could find from this summer, and created my mileage log. It came up with me getting 144.34% of my EPA estimated mileage! I'm already an Expert hypermiler, and I just got started ;) :Banane27:
  18. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Congrats!! Nice work! :thumbs_up:
  19. SentraSE-R

    SentraSE-R Pishtaco

    In my never-ending quest for improvement, I started to maximize my FAS glides today, with my calibrated SG. I'd been to the next town to visit the pharmacy, and drove back via my 19 mile flatland test route. My initial test route drive got 39 mpg using cruise control, and 42 mpg with my first P&G. I improved that to 44+ mpg before recalibrating my SG. I learned that aggressive P&G, and P&G in 6th gear hurt my P&G mileage.

    This time, I maximized my glides at either end of my turnarounds, and got 46.2 mpg over the 19 mile route. Getting to it involves a downhill 3 miles, and about 6 miles of flatland driving. I got 57.5 mpg on the 9 mile drive. Going home afterward, I got 43.6 mpg over a 9.3 mile route. On the return drive, I practiced P&G in fourth gear, from 28-42 mph.

    A couple of questions, if people are still reading this thread. I noticed I'm always in open loop when P&Ging. Is this normal? I thought my car was supposed to be in closed loop most of the time, but P&G operations seem to keep it in open loop all of the time.

    My car doesn't like to enter fuel cutoff on highway drives, since I set the cutoff value to 2, and then to 5. My repair manual gives a 2500 rpm lower limit for fuel cutoff, which is about 65 mph in 6th gear. I've been monitoring TPS and loop values, and the problem is the ECU stays in closed loop. The solution seems to be to FAS quickly, as 9999 mpg beats 113 mpg. Comments?

    So, I'm learning to finesse my hypermiling techniques. I plan to glide a lot more, and I've got my P&G speeds for my top three gears. Hypermiling is like a real-life video game, hopefully without the crash and burn that goes with most video games.
  20. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Very nice work! Those numbers look very promising -- particularly for colder weather! :thumbs_up:

    After bump starting it is normal for the engine to run in open loop for a bit. If you pulse for less than the time period the engine stays in this mode, you'll never see closed loop. I wouldn't worry too much -- as you've seen you will still beat the pants off of steady state with it. As a test, bump start and then just steady state cruise while watching the loop gauge -- you should see it transition to closed after a while. Then you can compare that timeframe with your pulse duration.

    Absolutely FAS quickly -- that will win. Do be aware that the SG remembers the last consumption values it received before an ECU reboot (key on and off for FAS and you get one ;)) and will continue to use it until it starts getting new data again. What does this mean? Technically you'll get your best FE by cutting the engine off at the top of the pulse but there are two problems with this:

    1. You have to leave the key in the ACC position longer if your engine is at a higher RPM to prevent dieseling back to life.
    2. The SG will latch onto the really low value for the whole duration of the ECU reboot and will pull your average down quite a bit -- you'd be "flying blind."
    Compromise is your best bet. Sacrifice a little of the efficiency by waiting for the RPM to drop close to idle level before FASing. You can shorten up the keying event substantially and the SG will use a high value (which will be higher than your trip average) during the reboot. It won't be as good as 9999 but at least it will be high enough to pull your average up pretty reasonably during that short slice of time.

    For highway speeds (50mph and up) I only use NICE-ONs for the glides because my ECU reboot can be as long as 7s.

    No crash and burns!!! I like to tell people that proper hypermiling is the best combination of chess and billiards every invented -- but without the collisions!!

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