Fuel grade and fillups?

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Author Message   98roverdisco Posted on Wednesday, May 01, 2002 - 04:40 pm:    Anybody played with the fuel grade on GEMS equipped rigs? I just bought a 1998 w/80k miles. The manual says "premium." The local station was out, so I tried "plus"-89RON. Truck ran fine, no pinging on the ugliest hills. This intrigued me, so I tried a tank of "regular"--unleaded 87RON. Same story. I cannot discern a power difference (in highly accurate seat of the pants evaluations). Not a ping to be heard, ever. So, my question for discussion: Does the knock sensor-equipped FI system have the have the ability to adjust that far? Anyone have long term consequences or thoughts? It might be nice to have as an option for trips to neverland, it would also be OK to save the .40c/gallon, assuming no adverse imapact........ Also, my rig is an ex-California truck. Query: Is the evap system any diferent? I have noticed that fillups need to be done SLOWLY. If you go fast, it will shut off at about 4 gallons. This is fine for my visits to Washington, where adults can fill their own cars. Sadly, in Oregon, we are not intelligent enough to do so--my slow fill takes more concentration than most fume-addled attendants can muster. Any thoughts?   p m Posted on Wednesday, May 01, 2002 - 06:43 pm:    98, yes, GEMS listen to knock sensors, and will alter the ignition timing once it hears pinging. Everyone who tried using 87 octane fuel says there's no problems at all. I would imagine that if it retards ignition too much, your engine will lose performance. Once you start compensating for it by heavier throttle application, your gain disappears. there are other considerations (like carbon build-up), for which there's a variety of opinions. peter   98roverdisco Posted on Wednesday, May 01, 2002 - 07:06 pm:    Thanks Peter, I've seen some of the build up info on the site....I might just take that problem on as it comes. Anyone got input on the fillup issue? Normal?   p m Posted on Wednesday, May 01, 2002 - 09:42 pm:    tell the attendant to keep the nozzle handle up, not down (a jeep trick). it'll go much faster without shutting off, but may spill a bit. peter   Leslie N. Bright (Leslie) Posted on Thursday, May 02, 2002 - 09:21 am:    I never had to fill up the Disco w/ the handle up, but the Wag, you HAD to do it that way, lol..... FWIW, I ran mid-grade in mine for a long time, but started having symptoms of valve-issues. Changed to premium, and the problems subsided (well, for 50k mi, anyway). While it can adjust for knock, I did notice a difference in performance behavior between the different grades. As you said, a seat-of-the-pants kind of measurement, but, it was noticable. Mi dos centavos, YMMV.... -L   Garrett #2 Posted on Thursday, May 02, 2002 - 11:09 am:    Can somebody please tell me what "GEMS" is...it's a term used above. Sorry, i'm new to all of this. Thanks   Leslie N. Bright (Leslie) Posted on Thursday, May 02, 2002 - 11:17 am:    It's the abbreviation for the Engine Management System, meaning that it's an OBD-II Rover ('96 and on) instead of a OBD-I Rover (ie, '94-'95). Does that help? -L   cartner Posted on Thursday, May 02, 2002 - 11:27 am:    does an OBD 1 do the same thing? I mean sense grade/knock and compensate for it?   Leslie N. Bright (Leslie) Posted on Thursday, May 02, 2002 - 11:37 am:    I dunno off the top of my head, but I tend to think that adding the knock sensors were part of the switch to the 4.0 GEMS system, so I think not.... I don't have my workshop manual here, so I can't check right now.... Someone else will probably pipe in first, tho'.... -L   Garrett #2 Posted on Thursday, May 02, 2002 - 11:44 am:    Thanks Lelie! But does GEMS stand for something?   p m Posted on Thursday, May 02, 2002 - 12:34 pm:    Glorified engine marketing system, or something like that Leslie, both my disco and rangie need just as much of handle-up action as the jeep peter   Leslie N. Bright (Leslie) Posted on Thursday, May 02, 2002 - 01:22 pm:    I don't remember the G for sure, but notice my capitals.... Engine Management System! It might be General, I think, but anyway.... Funny, the Disco didn't.... I'd click it to fill-fast, let it run, then round it up to wherever.... the Wag, if you filled it fast it'd cut off, and, you couldn't put any more in once it cut off or it'd spill..... Every wag I've ever looked at as a fuel stripe down from the tank... -L   p m Posted on Thursday, May 02, 2002 - 01:35 pm:    Leslie, it's nearly every 4x4 station wagon. The fuel inlet bends too sharply, causing flow problems and pump nozzle shutting off. Beats me why couldn't they just angle the filler hole down... the nozzle would've stayed put... peter   Leslie N. Bright (Leslie) Posted on Thursday, May 02, 2002 - 01:42 pm:    Yeah, that's the problem I had on the Wag, and on the Cherokee... But the Disco's angled in there, and never cut off on me until it was almost full, but it saved me enough room to round to the next dollar... -L   Milan Posted on Thursday, May 02, 2002 - 03:01 pm:    FWIW, following the last discussion on fuel grade, I started using 87 octane only. Thanks to the knock-sensor, no pinging but I did notice some power loss. The only way to tell for sure, though, would be to dyno the truck. I still run 2 tanks of premium every now and then as we get 10% ethanol premium at Mohawk. Burns hotter and cleaner, so I do this on all vehicles even if they don't require premium. Suffice to say, my walet is hurting less since I switched to 87. Allmost $9 every fill (about once a week). Hey it buys me 2 beer and that can't be bad.   Mateo Posted on Friday, May 03, 2002 - 11:40 am:    how could the petrol station have 89 and 87 but not the 92 (91)? Oil refineries dont make a mid grade octaine. They deliver 87 and 92 to the station, and the stations have a mixer that takes from both tanks to create the mid grade. If they were out of 92, you got hosed! You actually got some 87. But hey, I've had my disco for three years and I run 87 octaine. Every once in a while I run Redline system cleaner in it, and about every fourth tank I'll run the 92. Thats about it.   Jay Hobbs (Jayxd) Posted on Friday, May 03, 2002 - 01:24 pm:    You mean there are no self-service fuel stations in Oregon??? Holy Smokes!   doug james (Dgj95lwb) Posted on Friday, May 03, 2002 - 03:17 pm:    The station owners' lobby overwhelmed the Ore legislature and the policy wags. The 'premium service' you get, 'only' costs 5-10cents more per gallon there than here-'pump yerself' neighboring WA. DIY in Ore? Hell no, they might blowed themselves up real good...! doug, ex-Oregonian   Leslie N. Bright (Leslie) Posted on Friday, May 03, 2002 - 03:28 pm:    Oregon and New Jersey, no self-service gas at all.... FWIW.... -L   Jason Vance (Jason) Posted on Friday, May 03, 2002 - 07:45 pm:    HAHAHA Doug! Ex-Oregonian over here, too! A friend of mine once visited Oregon and was pumping his own gas when the gas attendent ran out and started yelling at him... Attendent: "Hey, you can't do that...whaddaya think yer doing!!?" My friend: "...uh, it looks like I'm pumping gas..." Attendent: "Don't you know that stuff is explosive??!!" And my friend wondered if that particular gas-refill-technician had undergone any formal training qualifying him for such a dangerous task!   M. K. Watson (Lrover94) Posted on Friday, May 03, 2002 - 07:51 pm:    jasonV i had that same experence. several years ago my wife and i flew out to Ore. (Hood River)in an attempt to adopt a child. that aside, i borrowed a friends car that lived there. he failed to feel me in on the butt chewing i would get when i attempted to get fuel. there was a bit of a scuffle and then i recieved a verbal lashing on the dangers of refueling. its funny now but at the time its wasnt and they take checks at the mcdonalds drive thru. wow i love Ore. mike w   98roverdisco Posted on Friday, May 03, 2002 - 08:03 pm:    Being, currently, an Oregonian, I return to my native state--Washington--to buy my gas. I DO love driving for 15 miles to do it.......... I consider it my special "thank you" to all the station owners in the aforementioned lobby.   Jason Vance (Jason) Posted on Saturday, May 04, 2002 - 01:34 am:    Dang, 15 miles! That's about 2 gallons round trip just to refill! Sadly, few (Oregonian) gas-station attendents must get out of the state, 'cuz they treat self-serving offenders as gun-wielding madmen hell-bent on destruction! I wonder if they know that, in other states, their job isn't all that exclusive!!!! BTW, here's some tidbit I heard, but haven't confirmed: when you are topping off your tank to squeeze that last bit of gas in (or trying to make the bill even), the extra fuel doesn't enter your tank but is sent to recovery tanks under the gas station. I heard this on a money-saver tip on the news...don't know how logical/true it is, but if it is true, those full-servers in Oregon/New Jersey are taking even more money out of your wallets!   Milan Posted on Saturday, May 04, 2002 - 10:30 am:    Does not the pump shut of when the nozzle fluds? How would the fuel get back to recovery tanks?do you guys have some special pumps?   cartner Posted on Saturday, May 04, 2002 - 08:08 pm:    Hoover.   Jason Vance (Jason) Posted on Saturday, May 04, 2002 - 11:38 pm:    Because the nozzle is above the level of the gas in the main tanks (and the recovery tank...if this exists?), the fuel left in the hose behind the nozzle would be sucked back. I guess the news warning was that when topping off, you are paying for gas that is metered at the pump to refill the emptied hose before it reaches the nozzle and enters your tank. That's the only logic I can come to...anyone else ever heard of this?   Paul T. Schram (Paulschram) Posted on Monday, May 06, 2002 - 12:41 pm:    Knock sensors on OBD I Vehicles. Correct me if I'm wrong, but I believe the OBD I vehicles are essentially limited to electronic control over the fuel injection (when and how much relative to air density). The ignition timing is (as far as I can tell) purely mechanical and vacuum operated. Paul