Saturn SC Cheats

Discussion in 'Other Manufacturers' started by msirach, May 3, 2007.

  1. diamondlarry

    diamondlarry Super MPG Man/god :D

    I checked my Saturn with the 110 ohm setup and the SG said 247F for intake air temp. Shorting the wires won't work because it throws a code. In fact the bottom limit is somewhere between 110 and higher than 105 ohms to avoid the CEL(check engine light).
     
  2. jamtee

    jamtee Well-Known Member

    Larry, is there any sign the car is running too lean? That is my greatest fear with this and is why I went with a 220 ohms before.
     
  3. reedy71

    reedy71 Member

    What does one have to do to get 45 mpg in a SC2 ('93) 5 speed (the 124 hp DOHC engine)? (I might buy one as they tend to be less than any other car promising good mpg.)

    Somewhere else on here suggested that the sweet spot for Saturns was 40 mph. I was hoping for a sweet spot of more like 55-60 mph. This is probably the wrong place to ask what cars might provide that but any suggestions are welcome at this point BEFORE I buy something.
     
  4. jamtee

    jamtee Well-Known Member

    HAI, P&G nice/off (as often as possible), basically follow the techniques in "Beating the EPA - the Why's and How to Hypermile" I am still learning but my last 3 tanks average 44.84.
     
  5. tommyt31

    tommyt31 Active Member

    reedy71: Before I knew anything about hypermiling I was getting between 30 - 35 mpg in my 96 DOHC. Then I rebuilt the engine and lost about 8 - 10 mpg. (I have to rebuild it again) I am back up to 30 mpg with only city driving, by coasting in neutral (or clutch pressed in), acclerating slowly, I don't use the AC, and I have an HAI. The rpm's on my car stay high (1500) till the car just about comes to a stop. I disconnected the IAC valve and the problem went away. The car runs fine without it but if you turn on the AC it will idle so low that it nearly stalls. Also, it will idle lower than normal at startup. That wasn't an issue for me, though. Possibly in the winter it would be.

    Below is a pic of my HAI. The silver duct off the side is 3" aluminium dryer vent hose with insulation and aluminium tape wrapped around it. The duct sits along side the exhaust manifold. It has holes in the side of it right next to the manifold. Also, a 3" hole at the bottom. I capped off the other end of the airbox with cardboard, hotglue and packaging tape. I also moved the IAT to the middle of the box to get hotter readings. I have a digital thermometer installed on my dash to read the temp in the box. It is usually around 130 F when driving around 40mph or higher. It takes at least 10 minutes to get to 130 F. It will get to 150 F or a little higher when driving slow in stop and go traffic. I need to wrap some aluminium foil around the whole exhaust manifold to trap the heat better. As Jamtee stated, 40's is doable.

    [​IMG]
     
  6. tommyt31

    tommyt31 Active Member

    PS: I hope my wife doesn't mind me posting a giant picture of her on the internet!
     
  7. reedy71

    reedy71 Member

    Thanks for all the encouraging words.

    Still deciding on the '93 SC2. Got codes 22, 27, 45, and 53. Replacing the TPS may take care of all that and it may then get decent mpg (about 25 now.) Then again there may be some other problems. Not sure what to make of code 53. It also needs coolant flush and seems to have a cooling fan problem (the cause of code 27?) and needs a tune up and...
     
  8. reedy71

    reedy71 Member

    Do other Saturn owners experience the same high rpm issue? (The SC2 I've been looking at did 1600 rpm until stopped then dropped to 1250. If running real warm then it went to 900. But it has a TPS problem.)

    If so, is disconnecting IAC valve the best solution?
     
  9. diamondlarry

    diamondlarry Super MPG Man/god :D

    It seems to be something designed into the software. Disconnecting the IAC seems to be the only fix.:( It does cause some minor issues in the cold IN winters on start-up but I have found it easy to deal with. When first starting the car in the morning or after sitting all day at work, I just put light pressure on the gas pedal while starting and for the first few seconds after it starts. After it runs for a bit it smooths out.

    Jamtee, I never noticed any signs of running too lean with the 110 ohm setup. The sparkplugs never showed any signs of excessive heat like you would expect form a too lean condition.

    This brings up another point I wanted to make. Running an engine too lean doesn't necessarily mean that it will run hot. In fact, running lean will cause the engine to run cooler. This is because there isn't as much fuel to produce the heat; in most cases. The only time the engine will start running hot when lean is when it's under a heavy load such as full throttle or climbing huge hills. If a hypermiler is behind the wheel though, neither one of those conditions should be an issue.:p
     
  10. tommyt31

    tommyt31 Active Member

    I agree with DiamondLarry about disconnecting the IAC. Startup does require a little rev. when cold to get it to idle smoothly. Also, running the AC caused the rpms to go so low that it got a little rough at idle. The nice thing about doing this is that the rpms drop much quicker inbetween shifts, so you can match your rpms to your transmission speed easier when shifting quickly. When I run with the IAC connected I always pause a little inbetween shifts to let the rpms drop enough to match the transmission speed for a smooth shift. I think the Saturn engineers did this on purpose. Probably better that way for people that are new to 5 speeds and tend to shift a little slower anyways. The higher idle while the car is moving is tied into the vehicle speed sensor (VSS). I don't know why they did it that way. Maybe just to keep the rpms up for smoother shifting and to prevent bogging when going to the next gear.
     
  11. scramblejim

    scramblejim I make Baked Beans

    I'll give another vote to the rpm fluctuation when coasting in Neutral at speed.
    I just re-ringed my DOHC engine in my wagon about 1,000 miles ago, (about 100 miles after I bought the car) because it was burning oil (as per previous owner 1qt/600miles) and my first couple of tanks were less than impressive. My theory is that Saturns burn oil because oil rings stick in the piston, reducing drag on the pistons. With new rings and honed cylinders, I got alot more drag in the engine till the new rings cut in. My mileage has steadily improved-almost daily. I started to P&G a little on this tank and with about 150 miles, my SG2 is showing 44.1mpg for this tank.
     
  12. reedy71

    reedy71 Member

    Update on '93 SC2:
    1st tank: 26 mpg, some Lucas and a tune-up
    2nd tank: 30 mpg
    3rd tank: wiped stuff off of IATS, changed ECTS, 37 mpg
    Given that I did the ECTS about 1/2 way thru tank 3, tank 4 could be 40+
    Car is working out. About the only other things to check are IAC and EGR.

    Someone posted a question about substituting a resistor for the IATS and possible engine damage. Haven't seen a reply so I'll ask it. Basically the resistor is telling the PCM that the air is hotter than it really is and thus less dense than it really is (less O2). That would probably cause the engine to run a bit lean - obviously lean enough to save fuel or one wouldn't do it. Doesn't running lean hurt the engine in the long term? If not, why not?
     
  13. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    That only works for a little while. The exhaust oxygen sensors will quickly pick up the lean condition, and the ECU will feed more fuel to restore the ratio.
     
  14. tommyt31

    tommyt31 Active Member

    You could make a hot air intake like I did. It definately helped me to get about a 3 mpg improvement. Plus you are not leaning out the AFR, you are adding less air and less fuel but the AFR is still the same.

    If you run consistently too lean from the resistor trick (or other tricks) you will get a higher average temperture in the combustion chamber which could lead to burned valves, pistons, etc. The problem is the flame speed slows down which requires you to advance the timing. If that is not done, the combustion event will not be complete when the exhaust valve opens and you end up with a higher average combustion chamber temperature. To be safe, you could fool your ECU to advance the timing, or make changes to the combustion chamber to speed up flame speed. I think you would be fine at AFR's below 16-17. Above that, I would start to get worried. As DiamondLarry said, when hypermiling you have less of a chance of issues with heat because you have low load and low rpm's. With a slower flame speed it is imperative to keep from reving the engine real high. And low load will also keep the heat down. Once you get around 20 AFR you should start to get some misfiring, so that would be your first clue you are too lean.

    I put a wideband oxygen sensor on my car recently. I am amazed that the average AFR is well above 14.7. I need to do some datalogging but it looks like the average AFR during light driving is around 15.5. I should re-calibrate just to make sure, but the first time I calibrated the sensor, it came back good. I have been trying to lean out the mixture a little at a time, with the wideband. I got up to 15.6 so far with room to go (obviously). When I put the wideband in, it caused the car to run richer than normal (about 14.6:1). So I have been slowly adjusting it leaner to get were i am now. Which is right about where the factory sensor is at. I thought I would get a pretty good gain on FE with the wideband but now I'm thinking it is already pretty good. There is one thing I would like to try, though. I am going to try and lean out the mixture just during light cruising in order to get the AFR up to about 17 or 18 at that time. It is a little risky, but I am willing to give it a try. From what I understand, Honda used to make a civic that ran lean during light cruising that ran lean for better mileage. I think that was a good idea. I just wish I had some control over the timing.

    Anyone know if any of the sensors have direct control over the timing on a Saturn?
     
    Last edited: Sep 23, 2008
  15. tommyt31

    tommyt31 Active Member

    Just an update: I lost my datalog info from my narrowband (NB) sensor so I will have to redo that to find the average AFR. I managed to hook up a micro-switch on the throttle plate lever so that I can automagically switch between the wideband sensor and the NB sensor depending on how far I press the gas pedal. The default sensor is the wideband. The car doesn't switch over to the NB sensor until the TPS reads 33 on my Scangauge (or 1.5 volts on my wideband software). My first test was this morning. Everything worked beautifully. The car was running around 16.5-17 AFR (still need to look at the datalog). Then when I hit the gas a little harder, the AFR would go down when the NB sensor kicked in. I am going to turn the NB on a little sooner and lean out the wideband portion a little more. No issues with driveability so far. Water temps look good, too. No mpg results yet, but I hope to get some results in a week or so.
     
  16. tommyt31

    tommyt31 Active Member

    Well, I did some more playing around with my wideband. I tried to lean it out a little further and turn on the NB sensor a little sooner. Around an 18 AFR I am getting some missing and severly decreased power. I was getting missing even when cruising at 40-50 mph. I dialed the AFR back to around 16.2-16.5. Seems to be running fine. I also adjusted the NB to kick in a little later (like I had before). I would like to be able to cruise at around 70mph and not have the NB sensor kick in. Hopefully, I can do that now. Before, my top speed before the NB sensor kicked in was around 50 mph. I am going to get some mpg readings and see how much improvement there is. I would also like to go back to the NB sensor only for a short time and monitor what happens when you do the resistor trick on the Intake Air Temp sensor. I think that would shed some light on why some people are seeing gains.
     
  17. DrivenByNothing

    DrivenByNothing New Member

    From the research I've done, the timing isn't directly controlled by any one sensor. The Saturns use a crank angle sensor to know when to fire the coils. The ignition is a solid-state, wasted spark setup. This amounts to two cylinders getting spark whenever a coil is fired. It's used to save money on parts and tends to be just as effective as ignitions with coils for each cylinder.

    The resistor trick has the potential to advance the timing, but as you stated it really shouldn't be considered as a long-term solution.

    We basically have 2 options when it comes to controlling the timing. The first and most challenging would be to hack the PCM by finding and altering the timing maps. The second option is a method that has been pioneered by others and it amounts to using the Ford EDIS system with an ignition controller like MegaJolt. Of course, we could always try to look for other options, but something like the MegaJolt Lite Jr. system isn't all that expensive compared to most other options and would give quite a bit of control over the ignition.
     
  18. diamondlarry

    diamondlarry Super MPG Man/god :D

    As DBN mentioned, no single sensor has complete control but several can influence it. I know that the MAP sensor can be used to tweak the timing as well. I think that the coolant temp sensor may have some influence on timing as well but I would have to do some checking to verify that one.
     
  19. diamondlarry

    diamondlarry Super MPG Man/god :D

    There is a device called an EFIE that can alter what the O2 sensors see to keep that from happening.
     

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