Ok, so I recently got a new set of rims on my 04 ls now, I understand that going from 16 - 18 was going to give me a small decrease in mileage whatever... but I'm losing 50 -60 mpg out of the tank... I've changed the plugs and the intake filter, what else should I look into changing out to help with this?
oil and the filter
fuel filter
new injectors?
is losing THAT many miles per take an average for the rim upgrade? I didn't notice that large of a decrease when I took my old cav from 15 - 17...
any help would rock.
Memeber since '99
cardomain New England Tunerz
only thing I can think of is maybe your new rims are rubbing on something, causing excess resistance.
Or they are rediciously heavy. Try putting your old wheels back on and see what happens.
your rims and tires are probably a good 10-15 lbs MORE /wheel than the stock combo.
thats 40 extra lbs of weight on the car now. and not to mention, but its rotational mass... rotational mass when in motion is (by rule of thumb) like multiplying that weight by a factor of 7. you have basically just added 280 lbs to your car while you are driving, or like putting one hell of your hefty buddies in the passanger seat with you at all times.
also, the farther out you put that rotational mass, the worse its going to be. by this i mean, you went from a 16" wheel, which was approximately 8" away from the center of the hub or rotating point. you are now on 18" wheels, putting that rotational mass farther away from the point of rotation at 9".
its physics, and it sucks...
i would also double check and make sure your tire pressures are set right for the new tire size. generally, you will have to increase the tire pressure to maintain the same load capacity in the new tires.
1997 RedR - ZedR
What were the size of your old tires and the size of your new tires
I fyou changed the overall height the speedometer will be off and giving you false readings
I lost about that going from 14" steelies to heavy arse 18" excel daytonas. It makes a big deal...thats why lightweight wheels are so pricey
I have horrible gas mileage in my 03 cavalier ls sport as well. I get maybe 250 city mileage if that. I didn't realize that switching wheels made such a big difference. I dont think I have larger diameter wheels seeing that the rim is bigger but less rubber. If you measure diameter my old and new are .5in off.. the new being .5in more in diameter than the old ones. I also have an intake, exhaust and some other bolt on mounts.
Back to your question though. Would any upgrades to the fuel system actually help mileage? Like new injectors, fuel filter, etc. If so how much? I'm curious as well.
- 2003 CHEVY CAVALIER LS SPORT ECOTEC -
- Current Mods -
-- Vibrant Exhaust & DC Sport Header --
-- Lower Motor Mount & TTR Upper Motor Mount --
-- B&M ShiftPlus & Vibrant Front STB --
-- K&N Typhoon Short Ram Intake --
RIP DAD<3 We love & miss you so much!
just make sure its well maintained. make sure your intake filter is nice and clean and if you have never changed your fuel filter, that might be wise to do aswell. as far as what your asking, those are all more or less performance upgrades and will more than likely not have any positive effect on fuel economy.
1997 RedR - ZedR
RFOGALX wrote:I have horrible gas mileage in my 03 cavalier ls sport as well. I get maybe 250 city mileage if that. I didn't realize that switching wheels made such a big difference. I dont think I have larger diameter wheels seeing that the rim is bigger but less rubber. If you measure diameter my old and new are .5in off.. the new being .5in more in diameter than the old ones. I also have an intake, exhaust and some other bolt on mounts.
Back to your question though. Would any upgrades to the fuel system actually help mileage? Like new injectors, fuel filter, etc. If so how much? I'm curious as well.
the reason is that although the wheels are similar in diameter but the weight is moved farther away from the shaft.
imagine holding a 4ft, 20lb 2"x4" out shoulder level parallel to the ground, now imagine holding out a 4ft, 10lb 2"x2" with a 10lb weight sitting on the far end out the same way. you would have to exert more energy to maintain the latter, it is the same with your car except that more energy
typically means less mileage.
I'm running lean.. so i'm not getting enough gas into the chamber... that's why I was asking about the fuel filter and injectors. I don't have a FPR of FMU so something isn't right with the stock system if it's letting me run lean. Might have fouled injectors or a plugged up filter... but I'm not sure and I haven't messed with a fuel system before so.. I was looking for some insite as to if I should swap in new parts or not. I guess it can't hurt as long as I depressurize the system and follow my manual.
Memeber since '99
cardomain New England Tunerz
Code Zero, or anyone else who knows, give me you OEM tire info, and the wheel info for the 18" tires, I can calculate the EXACT overall tire diameter of both and tell you if someone put the incorrect size tires on it.
It can have an effect on the entire system, as well as your ABS brakes. Like ministock64 basically said, if your tires are throwing off your speedometer/odometer by .20 of a mile, at 200, actual miles your, trip odometer will only read 160 miles.
Later,
Jack
Ok, I found the stock OEM tire size for your car, and the sizes go as follows:
OEM 195/65 R15 Overall tire diameter = 19.99 inches
Tirerack.com recomends 225/40 R18 as a replacement for 18" rims, BUT that is WRONG!
225/40R18 overall tire diameter = 21.54 inches
A better tire choice would be a size of 205/25R18 with a overall tire diameter of 20.02
BUT I can not find a company out there that makes one in that size, sorry
Later,
Jack
ZER wrote:Ok, I found the stock OEM tire size for your car, and the sizes go as follows:
OEM 195/65 R15 Overall tire diameter = 19.99 inches
Tirerack.com recomends 225/40 R18 as a replacement for 18" rims, BUT that is WRONG!
225/40R18 overall tire diameter = 21.54 inches
A better tire choice would be a size of 205/25R18 with a overall tire diameter of 20.02
BUT I can not find a company out there that makes one in that size, sorry
Go here...
http://www.1010tires.com/TireSizeCalculator.asp
...Overall tire diameter for 195/65/15 is 24.98 whereas 225/40/18 is 25.08 which is as close to OEM as you can get.
I don't believe 205/25/18 is even in large scale production since you would only have about 2 inches of sidewall and most cars speedo would be off by over 10%.
Oops...
When calculating I forgot to multiply the "cross section width and aspect ratio" part of the equation by 2, before dividing it by 25.4, then adding the wheel size.
You are correct, 24.98 is the OEM overall tire diameter.
The 225/40R18 that tire rack suggests are 25.08 and would be a good fitment.
Sorry for any confusion...... I didn't get much sleep last night.
The formula is an easy one(when you remember it correctly)
(cross section width X Aspect Ratio) X2 / 25.4 + Wheel diameter
Later,
Jack
its not the tire diameter of the new wheel and tire combo thats the problem for the poor gas mileage.
its the weight of the new tire and the positioning of the weight being farther out from the point of rotation.
im pretty sure it was already said but i will say it again.
take holding a way for example. if you take a 10 lbs weight and hold it in your hand close to your chest, its not very difficult and you could hold it for hours or until you got board. now take that same 10 lbs weight and hold it straight out in parallel to the floor. you exert alot more force holding that weight farther away from your body (point of rotation in this example) then you do when its right up against your chest.
same goes for your car. it takes more energy to spin that wheel when the weight is pushed farher out (going to a bigger rim) because you are moving the weight farther out from the point of rotation. not to mention aftermarket rims and lower profile tires do tend to be a little heavier then the original ones. the rims maybe heavier then the factory or may even be lighter, but the tires that you would need for the larger rim to keep the same diameter would be lower profile tires. low profile tires are generally heavier because of all the sidewall reinforcment that they need to put in to the tire to help it maintain the vehicles weight and take impacts better such as potholes.
1997 RedR - ZedR
I've got 225/40/18's on there. the 04 LS's come with 16s not 15s. The stocks are 205/55/16 and I used 1010tires for my calculations..and I'm actually running slower than the speedo, so for ever 60 miles driven I'm only going 59.4. So even at .6 per 60 miles, that's not going to factor in too much. I'll have to get a scale and weight each tire/rim combo. I didn't think there was that much difference in weight when I was moving them around. I'll have to see. My main concern is that, I'm running lean, but have crappy gas mileage. I was at 120 at half a tank...that's horrible! And now gas around here is over 3 bucks a gallon again... f'rs!
Memeber since '99
cardomain New England Tunerz
Go ahead and replace the fuel filter when your funds/time allows, I understand its not been done, and a plugged fuel filter will cause a fuel restriction, the computer will then fire the injectors a bit longer to compensate. But, your mileage didn't drop till after installing the rims, so the extra weight is definitely also a factor. Edgeracing.com often lists tire weight along with the other info, you might look there next time you are thinking of getting tires, and perhaps choose a tire that is lighter than what you have now. I'd definitely weight one of the 18's and a stock and see what the difference is. A bathroom scale would be good enough to do that. Also make sure they are properly inflated, like stated before, larger I.D. tires usually require higher pressure to maintain load rating, an underinflated tire will definitely affect mileage negatively.
Code Zero wrote:I've got 225/40/18's on there. the 04 LS's come with 16s not 15s. The stocks are 205/55/16 and I used 1010tires for my calculations..and I'm actually running slower than the speedo, so for ever 60 miles driven I'm only going 59.4. So even at .6 per 60 miles, that's not going to factor in too much. I'll have to get a scale and weight each tire/rim combo. I didn't think there was that much difference in weight when I was moving them around. I'll have to see. My main concern is that, I'm running lean, but have crappy gas mileage. I was at 120 at half a tank...that's horrible! And now gas around here is over 3 bucks a gallon again... f'rs!
Actually that is not correct... It means that at when your speedo shows 60MPH you are actually travelling at 59.4MPH.
1010tires.com says that there is a Diameter Difference of 0.84% larger for the 18's. This means that for every rotation of the tire you travel 0.84% further than normal. So in the end you can basically add 1% to your fuel economy. Still not a great number... I would place the blame on the mass being moved outward on the rims and you driving the car a bit harder to test the new tires...
Knowledge about everything and yet an expert of nothing!!
Jack of all trades.
either way it's neglegable looking at the tires today I know they need air pretty bad. Gotta get that oil changed too. I've got the fuel filter, just need to find the time to install it. Not driving the car any faster or harder than usual, not with these streets around here in Rhode Island... not exactly smooth and level if you know what I mean! I've got a week off coming up at the end of this month so I'm going to take stuff apart and make sure it's all put back together the right way. The decrease in mileage didn't happen with just the rims.. the rims and plugs got changed out as well as the ignition got messed with when I dyno'd it so I need to make sure everything it getting the correct sparks and that everything is grounded the way it should be... double check my plug gaps too... I went back to the stock gap from being .010 over stock when I changed the plugs out.. might have something to do with it... as well as I really do think there is an issue with my stock FMU, when I ran the dyno I was lean for a VERY long time before going stouch, which only happened at the very top end of the rpm range..which isn't good.
Thanks for the input guys! I'll post back when I get everything ripped down and reinstalled or replaced!
Memeber since '99
cardomain New England Tunerz
