What have we done to improve 5s mpg?, Anything you've done to get better mpg out of your 6g Options

[ricochet1490]

My initial thoughts on this would be to make some clear (as to not detract significantly from the look of the car) body panels to improve aerodynamic efficiency... but I have a separate thread for that http://www.6gc.net/forums/index.php?showto...mp;#entry928769

I post here however to discuss engine mods. Any ideas or thoughts on this? I was thinking of maybe advancing the ignition timing a bit to burn hotter, increase hp and hopefully mpg, but idk. Does a good CAI help? or a larger O.D. exhaust? What have you guys done?

[RabidTRD]

Anything that helps the car breathe better increases MPG. Turbos, intakes, larger exhaust, clean throttle bodies...

Iridium laser cut plugs are great too.

Areodynamics is a waste of time for how little you'll gain in the end. Realistically, you'll gain more from just lightening the car. CF hoods, CF hatch, strip the interior... lol.

[ricochet1490]

Anything that helps the car breathe better increases MPG. Turbos, intakes, larger exhaust, clean throttle bodies...

Iridium laser cut plugs are great too.

Areodynamics is a waste of time for how little you'll gain in the end. Realistically, you'll gain more from just lightening the car. CF hoods, CF hatch, strip the interior... lol.

I don't know about you but i'm not very keen on gutting my car haha. I know that making these things breathe better produces power power power, but I guess I'm curious to know if anyone has tracked the mpg change after making those mods. Or at the very worst, if you have those mods, post your best mpg up here.
I know mine at 100% bone stock with the exception of the wheels ( which are a mathematical OD match to stock tires) gets maybe 31.5 - 32 with 80% highway and 20% city if I stay WAY out of the gas. Normal driving at 50h/50c with the occasional lead foot puts me at 26.5 - 29.5

[richee3]

Realistically, you'll gain more from just lightening the car.

Best thing you can do. You can spend a fortune trying to change the amount of fuel that the motor wants to use, but for what? Save that money, put it in your gas tank. You'll go a lot farther. Just reduce the weight that the motor has to pull around and you'll reduce the fuel it wants to drink.

[stephen_lee]

the biggest increase in MPG comes from a lighter foot, and that your motor is in good shape ( no bad rings, in a good state of tune up), then weight of your car, tire pressures last

[Smaay]

Turbos do NOT increase MPG, in fact they hinder it

[bloodMoney]

Or you can do what Richee did and just swap in a BEAMS and get 33MPG.

[KAOS]

Turbos do NOT increase MPG, in fact they hinder it

I was just going to say, in what world do turbo's improve MPG? LOL.

[jordisonjr]

^ No kidding.
And boost doesn't help the fact that you want a heavier foot too.

[ricochet1490]

^ No kidding.
And boost doesn't help the fact that you want a heavier foot too.

Haha, that would probably be the biggest killer for me. So heres the question of the hour though, does a good flowing intake and exhaust help? I know on a big Chevy 350 dual exhaust = +2 mpg on the highway. But our cars from my experience kinda like the backpressure. The 4cyls from my understanding can't be as easily catagorized as the big v8's can. But I could EASILY be wrong on this. Are there any numbers on it?

I also did a bunch of calculations here if anyone is interested.
http://www.6gc.net/forums/index.php?showtopic=80535

This post has been edited by ricochet1490: Aug 15, 2011 - 7:54 PM

[azian_advanced]

in terms of exhaust diameters for ideal flow, this graph should give you an idea.


(Source)

also for the same amount of hp, the turbocharged engine will consume less fuel than the NA version.
so as long as you don't alter your driving style, you will save more fuel with the turbocharged version.

[ricochet1490]

in terms of exhaust diameters for ideal flow, this graph should give you an idea.


(Source)

also for the same amount of hp, the turbocharged engine will consume less fuel than the NA version.
so as long as you don't alter your driving style, you will save more fuel with the turbocharged version.

That kinda tells me that for a 5s, any upgrades to the exhaust... aka going to 2.5" back etc is.... useless? - or at least not required i would think

[azian_advanced]

it would reduce hp actually but not by much. while the genereal idea to reduce backpressure is by increasing the exhaust diameter, you also want to have smooth unidirectional exhaust flow which is obtained by having the ideal size diameter. larger diameters will actually promote turbulence and CAUSE backpressure.

[ricochet1490]

i could envision that after a certain point, pressure reduction and centerline velocity reduction could cause something like and Eddy current to come about if the velocity of the gas was just right. I think this is where the complications of gas fluids and liquid fluids come into play however and experimentation is required. azian, I tried to get your ppt but it wanted me to install some .exe program read the file so I never did it, but I am interested.

either way, if what you're saying is true, it makes sense to reason that more hp produced at a given rpm/level of fuel consumption = better mpg
So, the larger exhaust could be a drop in hp and worse gas mileage, but a turbo if driven the same could yield better? I can only assume ford and chevy have recognized this fact with the recent production of the supercharged 4 cyl cars. The CMAX in europe and soon to be the Focus in the states. Already in the Cruze. All have small supercharged 4cyl and get 40mpg or so.
I figure increased mpg would be true of advanced ignition timing as well though right? I mean, burning it earlier and hotter tends to provide more power (at the expense of your valves), so it should also yield mpg then. There is a nicr write up here Timing about his findings on advancing timing. I don't think he mentions mpg, but with ^ hp i would expect to see ^ mpg if we assume the above.

[azian_advanced]

advanced timing will gain hp at higher revs so this would be beneficial especially if you drive on the hwy a lot. but as to what degree is best is difficult without actual testing.

This post has been edited by azian_advanced: Aug 15, 2011 - 11:26 PM

[stephen_lee]

smaller static displacement = less air/fuel req'd to maintine a certain rpm.. you're using very little engine power to maintain a steady speed, this is where the small engine comes into play. the forced induction helps when u need more power(accel) to make up for the tiny motor.

so technically i can swap in a 4afe and turbo it...get better MPG AND a little more power than my 7afe, assuming it is tuned correctly.

[spolski07]

lightweight flywheel will remove a lot of the rotational mass. this will raise your MPG a ton

[stephen_lee]

lightweight flywheel will remove a lot of the rotational mass. this will raise your MPG a ton

only during accel will it matter. steady speed and uphill it will make no difference

[ricochet1490]

lightweight flywheel will remove a lot of the rotational mass. this will raise your MPG a ton

only during accel will it matter. steady speed and uphill it will make no difference

exactly correct. city mpg would improve, but steady cruise on flat highway would be negligible.

So where are we exactly with what can be done? exhaust could go either way.
Improved intake - only if tuned correctly and you stay out of the extra power
advancing timing - viable, to what extent we don't know
has anyone made any mods and tested at all? This weekend I am going to advance the timing to 14deg before top dead. I'll report what I find, as it shouldn't take me more than a week or so. like I said. I'm doing A LOT of highway driving lol.

[jlspec]

Ok finally did some testing of MPG for my 99 vert.

Did a drive to Santa Monica Beach Pier from San Diego. Also did some light city driving around china town. Highway speed range from 65-70 mph. (got two points so no speeding for me).

36 MPG was the result of that test. Another long highway test to LA gave me 35 MPG.

Another test which was base around San Diego but mostly highway gave me 28-30 mpg. avarage out of 4 test

50/50 test gave me about 24 mpg. An avarage out of 3 test.

Mostly city gave me 22 mpg. An avarage out of 3 test

Only mod is a K&N drop in. Engine runs great with no oil leaks and timing was stock. New OEM toyota plugs, wires, cap, rotor, and fuel filter.

This post has been edited by jlspec: Sep 7, 2011 - 4:20 PM