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Mods to make the ultimate MPG LS1

This is a discussion on Mods to make the ultimate MPG LS1 within the General Help forums, part of the LSx Technical Help Section category; OK, for starters I recognize that I'm going to get flamed like there's no tomorrow for this post. If you ...

  1. #1
    TooSlow
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    Mods to make the ultimate MPG LS1

    OK, for starters I recognize that I'm going to get flamed like there's no tomorrow for this post. If you feel the need, flame away, I have thick skin.

    I'm in the market for an LS1 Z-28 or Firebird. I'm attracted to the incredible performance of the LS1, as well as its relative thriftiness. I have a 25 mile commute each way for work, most of which is interstate, and I would like to get some opinions on whether an LS1 car can be tuned to regularly turn in 30 plus MPG. What do you think about these mods:

    1. Change rear gears to 3.73 to make 6th gear functional at a lower speed (60-65 mph)--yes, I am only considering an M6 car

    2. Replace tires with something a bit skinnier for a smaller contact patch (may require picking up some junkyard steel rims off of a V6 Camaro?)

    3. Tune computer to lean out the fuel curve slightly

    4. Hi flow cat-back exhaust

    5. Underdrive crank pulley

    6. Synthetic fluids throughout the drivetrain

    What kind of mileage could a car with these mods pull down? Any more good mileage suggestions? This car will be a daily driver with the occasional trip to the drag strip.

    TooSlow

  2. #2
    Member Capster78's Avatar
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    Buy a Geo, there fun to drive.

  3. #3
    TooSlow
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    Had a '97 Geo Metro, it just died. Need new wheels...

  4. #4
    Tech Junkie hammertime's Avatar
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    Any six speed LS1 you find is going to have 3.42 gears. You should drive it first before you change them. 6th gear still does rather well for highway motoring, and if you have to accelerate faster, 5th gear is awesome (well, so are 4th & 3rd)

    In the quest for mileage, you will never get your money out of the cost of the gear swap. Plus, you are wanting a higher numeric ratio, which may actually hurt mileage a bit.

    Otherwise, it seems you are on the right track. Instead of getting steel wheels, you could switch to a 225/55-16 tire, which is the same height as a 245/50-16 and will still mount an 8 inch wheel. If you go too narrow, you will loose the great handling of these cars.

    And definitely get a lid to replace the stock inlet tract! Later on, consider headers and high flow cats as an additional mileage/performance mod.

    Let us know how it goes.
    Hammer - hammertime.us
    2001 Light Pewter Metallic Camaro SS, 6 speed
    K&N, SLP Lid, SLP y-pipe, GMMG cat-back, Lou's Short Stick - more to come!

  5. #5
    Senior Member SeVeReDiStOrTiOn's Avatar
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    Quote Originally Posted by TooSlow
    I'm in the market for an LS1 Z-28 or Firebird. I'm attracted to the incredible performance of the LS1, as well as its relative thriftiness.
    Welcome to the boardTakes fuel to make the power the ls1 makes...M6's definatly get better mpg on the freeway though...cruising in 6th gear going 70 is only at like 1500rpm.

    By the way you're talking you sound like a 87 octane kinda guy...not flamming just pointing out the obvious. Why not get a different car that gets better milage and loves 87 octane? Yes the pcm in our cars will adjust for 87 octane...you'll lose performance and still have the possibility of detonation.

    For gas mileage you'll want to go to a higher gear...not a lower gear like the 3.73's you mentioned. Best thing for gas mileage is a good tune-up and keeping your foot off the floor. Also be careful with leaning out the fuel...make sure it's done on a dyno or data logged on the road and tuned by someone that knows what they're doing.
    Last edited by SeVeReDiStOrTiOn; 02-04-2006 at 09:53 AM.

  6. #6
    TooSlow
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    Thanks for the replies. The reason that I mentioned the 3.73 gears was that I have heard that the 6th gear is basically unuseable below 70 mph without bogging the motor down. My interstate trip is mostly flat, but there are a couple of sizeable hills on it--it would be nice to have the car geared so that I could shift to 6th, set the cruise and settle back. I picked up a $114 speeding ticket in the aforementioned Metro a few months ago, so cruising at 70+ in 6th gear is out of the question until my driving record improves a bit.

    I am a bit of a mixture between an 87 octane and 100 octane kind of guy--I grew up driving exclusively V8 rear drive GM products and only recently was seduced by the dark side (small economic cars). I'm at a point in my life where I am ready for something powerful again, but have come to really enjoy the great mileage of the Metro. I'm willing to sacrifice some handling prowess (and even a little power) in the name of better mileage, but I am still in need of a fast car. You have no idea how tired I am of people at work telling me to upgrade to a nicer car than the Metro. (As an aside--I bought an '88 Plymouth Voyager for $500 to tote me around until I find the right LS1 car. Scary to say, but the van is a step up in almost every way over the Metro).

    Finally, one more thought--how much more do t-top cars weight than standard roof cars? I would think that I want to avoid the t-top, especially if I'm going to hit the drags.

  7. #7
    Senior Member 02z28ls1's Avatar
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    My six speed car gets over 30 mpg on strait up hiway driving .You can definetly shift into 6th gear at 60 mph-the throttle response is terrible-even the cruise control has trouble maintaining 60-better at 65-70 or more which is more average speed on the hiway anyway. I use 5th gear more at 60-it doesnt really cost much mpg at that speed.The best mod for mpg that I found is an OBDII moniter that I have mounted on my dash that gives me mpg readouts from the on-board computer(along w/other interesting stuff).You will see exactly where your mileage goes and it's an eye opener.Stop and go stuff ,idling through ATM machines and fast food joints,letting the car warm up for 5 minutes instead of 30 seconds,just kills your mileage.Anyway these cars can definetly give you good gas mileage IF you exercise restraint(hard to do) with the gas pedal. If anyone is interested in the monitor thing which I highly recommend to anyone with a newer than 96 car-it's called a "Scangauge" made by linearLogic- www.scangauge.com and no I don't work for the company!It helped me get a couple more mpg average in the city stuff so it was worth the purchase.And I don't think you are wrong about the t-top car being heavier-but I don't think it's really enough to make that much difference,if you and the little woman go on a diet you will gain more benefits than worrying about the t-tops ,and t-tops are just plain cool in the summer.

  8. #8
    Tech Junkie hammertime's Avatar
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    Realistically, there is no problem running 87 octane in an LS1 for highway driving. Yes, you are taking chances if you run it hard, and losing performance over the higher octane spark map. But it won't harm the engine at all at part throttle. Cruizing down the road, you are using suprisingly little power, and the octane requirement is pretty low.

    Think of it like this: if you've ever read the manual on a lawnmower, the engine requires somthing like 77 octane. This is a function of the governed engine speed (part throttle) and light load on the engine.

    Now, when you take it to the track, you'd better fill up with the good stuff!

  9. #9
    Senior Member 02z28ls1's Avatar
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    I'm not arguing that -but like he says-use the 91 or better if you are going to full throttle it,and you know that urge is there at the stoplight with that obnoxious 5.0 revvin it up next to you. Anyway-wanted to relay another story about gas mileage.I had a V-6 98 Camaro,no t-tops car that got great gas mileage and was an awesome car on top of it(a viable alternative if you are looking for ultimate gas mileage).I kept track of every gallon of gas that went through it(like my present car)and noticed something about octane and that car with the 3800 v6.For every grade better of fuel that you put in it you would average 1 or better mpg.So for example (and this engine is designed for 87 octane)if you went up to 89 octane the extra cost was more than offset by the extra mile+ per gallon mileage you got.If you went to the 91 or 93 octane stuff you were a full 2-3 mile per gallon better average over the tank full of gas. Once I noticed this I continued trying this out to see if it was a fluke or not and it always worked. So basically if you wanted to try this with an LS1 motor(I havent)maybe it'll work .My theory was the knock sensor would allow the timing to bump up with the increase in octane and give better mileage ,I know I could definetly feel the better power.My LS1 gets nothing but 93 octane-it doesn't add up to that big an investment in the overall picture to me,and might get better mileage on top of it.

  10. #10
    TooSlow
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    Great replies, guys! Lots of good info to consider. 02z28ls1, where did you mount your scanguage and are you happy with how it looks there? It looks like a good tool and the price is right, but the design of the enclosure looks like it came out of the early eighties. The picture on the site shows is mounted under the dash at the front of the console--not too obtrusive there, but maybe hard to read?

    At any rate, I'm pretty confident that 30mpg can be attained with careful driving habits. Hopefully I can find a low mileage, low option car soon. Thanks for al of your help.

    TooSlow

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    Run the lowest octane you need. Change your plugs and all the rest of the maintenence stuff, then get the tank down as far as you can and put in a few gallons of 87 in. Drive the way you normally do. If you get no knock, then run 87. If you do, try it with 89, and then whatever the next step you have is.

  12. #12
    Tech Junkie hammertime's Avatar
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    Quote Originally Posted by 02z28ls1
    I'm not arguing that -but like he says-use the 91 or better if you are going to full throttle it,and you know that urge is there at the stoplight with that obnoxious 5.0 revvin it up next to you. Anyway-wanted to relay another story about gas mileage.I had a V-6 98 Camaro,no t-tops car that got great gas mileage and was an awesome car on top of it(a viable alternative if you are looking for ultimate gas mileage).I kept track of every gallon of gas that went through it(like my present car)and noticed something about octane and that car with the 3800 v6.For every grade better of fuel that you put in it you would average 1 or better mpg.So for example (and this engine is designed for 87 octane)if you went up to 89 octane the extra cost was more than offset by the extra mile+ per gallon mileage you got.If you went to the 91 or 93 octane stuff you were a full 2-3 mile per gallon better average over the tank full of gas. Once I noticed this I continued trying this out to see if it was a fluke or not and it always worked. So basically if you wanted to try this with an LS1 motor(I havent)maybe it'll work .My theory was the knock sensor would allow the timing to bump up with the increase in octane and give better mileage ,I know I could definetly feel the better power.My LS1 gets nothing but 93 octane-it doesn't add up to that big an investment in the overall picture to me,and might get better mileage on top of it.
    Well, I always put 93 in mine too, so I haven't ever checked it with lower octane. But that theory makes sense, more spark advance should equal more part throttle power and efficiency. I've been able to get 28+ mpg on long trips with the tops out at 80-85 mph (actually down 44 to table rock lake, Branson area...)

    But the good news is, if any of us were testing mileage with 87, and a 5.0 came revvin it up, we should be ok. We all know you don't need WOT for one of them.

    No flames please - its called humor

  13. #13
    Senior Member 02z28ls1's Avatar
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    I mounted the scangauge right on top of the dash (in the middle) with velcro for the visibility factor.I felt and it seems to be true that you have to be able to see this thing without taking your eyes off the road for very long.Now as for as looks-yeah it could have been done a little prettier,but for what it's worth mine is alot darker looking than the picture on the website would suggest.At night it's got this amber glow that's adjustable on brightness that looks cool.And if you were worried about looks like for a show or w/e just remove and stick in the glovebox or something.I've had some people think I was some kinda Camaro police pursuit vehicle with this thing on the dash-haha-well worth it for the entertainment factor right there. Added note-I don't see what all this is about running the worst octane fuel-it's not that much money at the end of the year to me.In a typical gas stop you are talking about $2.50 to fill er up from near empty.I've found a gas station a mile from my house that's only .05 cents a grade difference instead of the .10 cents that I used in my example.Most people waste more than $1.25 a day on Twinkies.If you want to track gas mileage and other things the Scan gauge is awesome.

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    Impounded YoMommasTA's Avatar
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    want max mileage...install a intake preheater like the older TBI used......you can use exhaust heat to heat the intake charge raising efficiency quite a bit....of course at wot throttle a good system would disable this feature.By the way lots of boilers use this feature to raise their efficiency.Its insane the power that is tossed out the exhaust.Another thing you could do is run HOT VAPOR CYCLE.This will more than double your efficiency....but of course everyone knows this,its been around for 30 years.OH you never heard of it? hmmm maybe because the oil companies and gov killed it...bet you can guess why!

  15. #15
    Senior Member 02z28ls1's Avatar
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    Conspiracy theories -An easier way to heat the air intake is to do the free mod -opening up the air intake below the air filter. Unfortunately this also allows the radiator to heat the air when you're sitting at a standstill.The scangauge shows real time air intake temperature as well as coolant temp. Just another interesting aspect of the thing if you use it on a daily basis.

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    Junior Member Gonad's Avatar
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    Oh and most importantly....keep your foot out of it!!!..........

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    Edited post...

    Hey, glad you stood your ground, MPG Man. And some good advice from everyone else.. not many of us can afford to waste gas. I not only like 4th-gen f-bodys because they are fast, but also because my Z averages better than 20mpg in the mixed driving I do (I can't imagine why anyone would want any less -- like the ones who drive a 6000 lb. truck to go to the store to buy a loaf of bread). I also happen to like driving a car that has functional OBD II instead of dumping shit out the exhausts so that we all get cancer (my wife and I know five people under the age of forty with cancer right now, and she tells me they are getting quite common in the ward she works in...). Oh, and by the way, while I'm confessing, I've driven Toyotas for years as well because they are bullet-proof and also get high MPG, and I LIKE them!

    You see, I've owned just about everything --- just sold a '69 427 Caprice that was my weekend car--- and I did a lot of street-racing as a kid -- in a Hemi 'Runner --- but since then I've actually read a thing or two and something happened -- I grew up.

    I still love Camaros as much as I did as a kid when I had my first '67 convertible. But man, it feels GOOD to go on a site and admit that I value gas mileage and low emissions as much as performance. I can't imagine wasting gas on a daily basis this far into the 21st century, and somehow convincing myself that it isn't hurting this country. Feels REALLY good to be a man and not a sheeple.

    More car guys should try it...!
    Last edited by F-body fan; 02-06-2006 at 02:57 AM. Reason: Clarifying

  18. #18
    Impounded YoMommasTA's Avatar
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    a 4 cylinder engine run in hot vapor cycle makes more hp than a 8 cly engine running standard FI and uses half the fuel to do it!Its a fact not a conspiracy.Was invented 30 years ago by a well known engineer.Noit that YOU would know the name...YER TOO YOUNG HAHAHAHAHAHAHA!http://www.schou.dk/hvce/?mode=2
    Last edited by YoMommasTA; 02-06-2006 at 06:40 AM.

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    go buy a truck, drive it for 6 months, realize how much it sucks to get 16 mpg. Then upgrade to a ls1 getting 30+ mpg. It will seem like your are upgrading.
    Your geo got....what....50mpg, so yeah 30 is bad in comparison. But compared to some other vehicles, they are in good shape.

    Ps: I have no problem getting 33 mpg, also i can run in 6th hear at 60 mph all day long.

  20. #20
    Senior Member 02z28ls1's Avatar
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    YomammasTA-I am a full 15 years older than you- I remember Smokey Yunick very well-amazing mechanical engineer.Thank you for complimenting our youth however. If you were to actually read the reference you refer us all to however you would see some facts that they quote Smokey himself as pointing out.The 2.2 Mopar experimental adibiatic engine was specifically asked about in 1988 and the answer that Smokey gave was that there was no reasonably priced motor oil that would last in this engine.Milspec jet engine oil @ 1988 prices of $98 a quart was the only one-by todays prices that would be like $200 a quart I'm sure.Smokey himself was of the opinion that you could only use carburation and not fuel injection.This is probably the downfall-it would pass 1983 emission standards but not the much,much tighter standards of today.I'm not trying to argue about this -I'm just quoting Smokey and the reference that you give-please reread if you didn't get it.There is no conspiracy-just reality-get over it.
    Last edited by 02z28ls1; 02-06-2006 at 07:48 AM.

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