mpg

[usmcagg02]

with the rising gas prices i'd like to get some better fuel efficiency out of my truck with out payin a sh** load of money. what is the best way to improve mileage on a 5.3L vortec? its pretty much stock, only has a new air filter on it.

[Graystroke]

what's a **** load of money? You can try running synthetics in everything. Axles, trans, engine, and t-case if you got one. You probably will pic up a mile or two. Free-flow exhaust and intake. Bed cover will give you the most mpg. get rid of the bug deflector if you have one.

[uglyota]

Don't get a whole replacement intake, because you'll start sucking hot air out of your engine bay. Just get a drop-in K&N for fuel efficiency. I agree with the exhaust stuff too. DO NOT waste your money on throttle body spacer like the Helix Power Tower or the PowerAid. Total waste of $100.
Don't chip or cam your truck if you're sincerely concerned about fuel economy, and for god's sake don't lift it!
Staying off the skinny pedal (or buying Honda Steve) is really the only economical thing that you can do to make a difference. None of the other improvements will "pay for themselves" over time with increased economy.

[Chadnutz]

Or get a diesel. $.18 cheaper per gallon. :flipoff2:

[BigRedFord04]

best way i've ever heard it put is that an engine is like a big air pump, the easier air can get in and out the more efficient it will be.

my suggestions would be a K&N filter (not a full kit), good exhaust, TB spacer (contrary to popular belief, i saw a bit of an improvment when i put mine on about a month ago), and synthetic fluids. i've also read that wrapping your air intake hoses w/ insulation to keep heat out helps keep the air cooler, i.e. more dense > more O2 > more efficient. i know its no fun but stay off the skinny pedal. i know the newer motors dont need spark plugs very often so replacing them might not do much for you. if you've got a bunch of miles on it run some fuel system cleaner thru the gas tank and get the berryman's fuel system cleaner thru the vacuum system, i've always found that stuff does great.

[BMFScout]

I thought that K&N assembly cut off that whole corner of the engine compartment in those models? I'm gettting one, I think it would definitely help even if it is slightly hotter. Have you looked at the resonator on the stock intake tube? Way restrictive.

[uglyota]

okay, then research the TB spacer on your engine before doing it, and if they're worth anything, find one on Ebay. I think you can get the name brand ones for $30 or so. but it didn't help me any

and I still say drop in filter, so you keep pulling air from the fender and not from the engine bay (the kits improve throttle response, but definitely not any more economy than a drop in)

my resonator wasn't restrictive at all, but I still got rid of it

(btw mine's a 5.7 not a 5.3 though)

[stx4wheeler]

i mean simple as that you not gonna be able to get a mile or two per galln better even if you do all that stuff to your truck. But if you think it is worth it when you go to true dual exhuast have and h-pipe put in before the mufflers and also get the cats hollowed out. i noticed like a mile or two per gallon if i am not hauling ass once i got the above exhaust work done.

[AgDieseler]

85% of what goes through a naturally aspirated engine is air, and like Austin said, any addition that lets the engine pump air easier removes the amount of work that has to come from burnt fuel.

An ample supply of fresh cool air for the intake, and the ability to expell spent gasses easily is the first step in making an engine a mpg monster.

Here's the wierd thing that I have yet to understand:

I just finished taking thermodynamics, and I learned that the typical thermal efficiency of a spark engine is 15-20%. That comes from an equation that says you want the energy that leaves the engine (like exhaust gas temperatures) to be as low as possible, and the energy that enters the engine (like the intake air) to be as high as possible.

But as common sense has told us, we try to keep the intake temp as low as possible. It makes sense that high EGTs mean an engine is being inefficient since that comes from unburnt exhaust gases.

Engineering aside, get cooler intake air, let the exhaust breath easier, run the lowest octane rating you can (higher isn't always better; it just costs more), run the AC as little as possible, idle as little as possible, and keep off the skinny pedal. :D

[robertf03]

4 barrel with vacuum secondaries

[Fredo]

Originally posted by uglyota
and I still say drop in filter, so you keep pulling air from the fender and not from the engine bay (the kits improve throttle response, but definitely not any more economy than a drop in)


No, the full K&N kit for the chevy LS based motors blocks off the corner of the engine bay and draws cold air from behind the headlight. Much much better air flow than the stock setup too. A buddy of mine has had 3 of those trucks and had the k&n on all of them.

[Fredo]

Originally posted by stx4wheeler
But if you think it is worth it when you go to true dual exhuast have and h-pipe put in before the mufflers and also get the cats hollowed out.

This....this idea is Horrible Peter. :) You're telling me it's a good idea to hollow out all FOUR cats on a 5.3L chevy? You're also saying that the computer won't figure it out and trip the check engine light, or even pass inspection?
I always get a kick out of people who say catalytic converters stop up an exhaust system. I saw a dyno test in Hot Rod a few years back that tested a 650hp big block with and without cats. The motor put out 654hp without cats, and ripped out 653hp with them. That motor was really straining due to the cats huh?

[uglyota]

Originally posted by Fredo
No, the full K&N kit for the chevy LS based motors blocks off the corner of the engine bay and draws cold air from behind the headlight. Much much better air flow than the stock setup too. A buddy of mine has had 3 of those trucks and had the k&n on all of them.
Didn't know this. In that case, just make sure and drop $$$ on the K&N brand, the cheap airaid or pro-crap kit that I got doesn't block off the area like freddy described

[stx4wheeler]

Originally posted by Fredo
This....this idea is Horrible Peter. :) You're telling me it's a good idea to hollow out all FOUR cats on a 5.3L chevy? You're also saying that the computer won't figure it out and trip the check engine light, or even pass inspection?
I always get a kick out of people who say catalytic converters stop up an exhaust system. I saw a dyno test in Hot Rod a few years back that tested a 650hp big block with and without cats. The motor put out 654hp without cats, and ripped out 653hp with them. That motor was really straining due to the cats huh?


ok not all of us drive chevy products with four cats. i got my one stock cat hollowed out on my, 95 bronco 351w and and had them put in another hollowed out cat in when they did my dual exhaust, and the reason for the hollowed out cats was more for the price than anything else because seriously there farva a ford bronco with a 351 is just a real power monster, as we all know. it was gonna cost me like an extra 80 bucks to get cats, and hey i maybe got one hp yeeeeah!! Also i have never had a probelm throwing check engine light or any codes. i simply stated the no cats thing to relate what my pos has, to give him a better idea. Let any further flaming begin now ***.

[mark]

My advice to get better mileage: Get your friends to drive you around. :D

I'm with freddy on the cat thing. With the OBD2 system on the 5.3, there are 4 o2 sensors, one before each cat and one after. The one before provides feedback to the PCU keeping the mixture in line, while the one after monitors the performance of the cat. All 1996 and after gasoline powered vehicles have this (all though not all have two cats), so hollowing out the cat on anything reletivly new will throw a code.

-Mark

[BigRedFord04]

i've seen on that body style truck that a TB spacer and a full K&N kit cause the air intake to rub against the fan shroud. check into it before you go spending $$ on all this stuff.

[eight]

I think you're slightly mixed up there David. We understand that why lower temp air makes more power is because its more dense so its like running a bigger motor. So to make the same power to move the truck, the intake air velocity is lower than stock so that equals less restriction. But then since the air is more dense, the throttle is more closed, and that's the biggest restriction on an engine. It would be great if we could figure a way to make a gas engine work without a throttle. I think it could be done by recyceling the exhaust back into the intake, now if such a system would actually increase effiency I do not know.

A big reason of the low effiency is all the heat (energy) lost to the cooling system. A perfect motor wouldn't need a cooling system because all the combustion energy would be converted into useable power. Running the engine as hot as possible without damage will get the best effiency. I'm not saying to swap to a higher than stock temp thermostat, but definately stay away from the low temp ones.

[uglyota]

Originally posted by eight
Running the engine as hot as possible without damage will get the best effiency.


Originally posted by Fredo
This....this idea is Horrible Peter. :)
I bet the smart people at GM figured this out, and included the correct, "super high efficiency" thermostat with his truck...no extra charge ;)

[BigRedFord04]

i understand where you're coming from kopecki, but i dont see how extracting more heat from the engine via the cooling system affects efficiency. that energy doesnt get used anyway does it?

[eight]

Originally posted by BigRedFord04
that energy doesnt get used anyway does it?

Correct. So try not to produce what doesn't get used.

[uglyota]

so you want to be able to make the same energy with less fuel and less "rapid expansion" like that david? and thus less heat generation, but to do that wouldn't you have to get rid of some of the other things that rob power, like internal friction?

edit: going home now...you guys figure this out while I'm gone, aight?
I'm confident that with enough keystone and a welder, Kopecki could solve world hunger

[stx4wheeler]

{Quote}
I'm confident that with enough keystone and a welder, Kopecki could solve world hunger [/B][/QUOTE]

this much i do believe to be true.

[AgDieseler]

The engine produces energy in three forms: potential, kinetic, and heat. When it comes to making the engine (and only the engine) more efficient, we talk only in terms of heat. Reducing parasitic loads like superchargers, transmissions, etc. deals with the kinetic end of things. We can assume the change in potential energy to be negligible to make things simple.

The engines gives off heat to 1) the atmosphere and 2) the cooling fluid. Ryan, you're right that a thermally perfect engine (Carnot) wouldn't need a cooling system since the heat out of the engine is zero, but the heat in is very high.

The equation is for Otto thermal efficiency: Nth = 1 - Wnet/Qin

To make this number as high as possible, Qin (heat in) needs to be as high as possible. The waste heat to the radiator and atmosphere is energy that doesn't get sent through the driveline. It's wasted energy, but a good way to reclaim some of that wasted energy is with a turbo. :D

In no way does this have anything to do with oxygen density or airflow velocity. I'm not saying that it isn't related. I was just mentioning the interesting opposition of what one engineering equation tells us and what shade tree mechanics have know for years.

In terms of water temps, I have run 160, 180, and 195 t-stats. I have noticed better power, fuel economy, and less smoke the higher my 195 t-stats.

PS: This is good tech stuff. Most forums will look at this question and never get into too much detail. I personally find this to be some of the most interesting engine tech. It turns out, it's also the cheapest with which to experiment.

[agjohn02]

Originally posted by eight
But then since the air is more dense, the throttle is more closed, and that's the biggest restriction on an engine. It would be great if we could figure a way to make a gas engine work without a throttle. I think it could be done by recyceling the exhaust back into the intake, now if such a system would actually increase effiency I do not know.

A big reason of the low effiency is all the heat (energy) lost to the cooling system. A perfect motor wouldn't need a cooling system because all the combustion energy would be converted into useable power. Running the engine as hot as possible without damage will get the best effiency. I'm not saying to swap to a higher than stock temp thermostat, but definately stay away from the low temp ones.

there is such a thing as a gas engine without a throttle. its called GDI or gasoline direct injection. works just like a diesel by injecting the fuel at the proper time in the compression stroke. they are problematic due to the fact that gas has such a low flash point and it is easily susceptible to detonation and ping. i found a link but didnt read it, hope it a good one:

[URL=http://www.mitsubishi-motors.co.jp/inter/technology/GDI/page2.html]

a perfect engine wouldnt have exhaust either. the 1/3rd rule is 33% goes to heat through the cylinder walls, 33% out the tailpipe in the form of heat, sound, and mass flow, and the other third is converted to mechanical energy only to lose 20% of that to friction in the drivetrain. man, cars are super innefficient.






my reccomendation on better gas mileage is very cheap. but not so simple and it could possibly throw a couple of codes in the PCM.

what you need to do is take the valve covers off and remove four rocker arms and pushrods. firing order for a sbc is 18436572, assuming that its the same for the new vortecs. remove 1467 and it'll still run like a champ. then take the oil pan off and remove the corresponding pistons and rods, hopefully it'll still be balanced. this will not only reduce parasitic friction inside the engine but reduce your displacement. for better flow in and out of the engine, remove the air filter and ducting and the exhaust manifolds. removing the manifolds cold result in a burnt valve but keep your fingers crossed and you'll be ok. dont forget to unplug the injectors, if you dont, your gas mileage will really suck for about 5 miles then it'll result in a huge manifold bomb. if it's 4wd, remove the front cv shafts and driveshaft. i wouldnt worry about the xfer case b/c then you'll have to buy parts. the only other thing i can think of is inflating the tires a bit more, to say 140 psi. this will give you less contact patch and less rolling friction with the road. fold your rear view mirrors in as well. this is about all i got for now, if i think of anything else ill let ya know. hope i helped. :flipoff2:

[BigRedFord04]

Originally posted by agjohn02
my reccomendation on better gas mileage is very cheap. but not so simple and it could possibly throw a couple of codes in the PCM.

what you need to do is take the valve covers off and remove four rocker arms and pushrods. firing order for a sbc is 18436572, assuming that its the same for the new vortecs. remove 1467 and it'll still run like a champ. then take the oil pan off and remove the corresponding pistons and rods, hopefully it'll still be balanced. this will not only reduce parasitic friction inside the engine but reduce your displacement. for better flow in and out of the engine.... :flipoff2:
or you could just get a V6...only reduces "parasitic friction" by 25% instead of 50%, but hell, its an improvement.

Still tho...that is one of the funniest things i've read in a while. to you i award this:

[agjohn02]

(creepy monty voice on, thumbs twiddling) eggggxxcellleennnnt (creepy monty voice off, thumbs stop twiddling)

[agjohn02]

ok, im an engine nut, took thermo in school, and still remember some of it even though its been a while. so, i cant leave this hanging.

i dont remember who posted this b/c i copied and pasted it, but it doesnt matter.


Quote:
[I just finished taking thermodynamics, and I learned that the typical thermal efficiency of a spark engine is 15-20%. That comes from an equation that says you want the energy that leaves the engine (like exhaust gas temperatures) to be as low as possible, and the energy that enters the engine (like the intake air) to be as high as possible.]

this is bass-ackwards

[But as common sense has told us, we try to keep the intake temp as low as possible. It makes sense that high EGTs mean an engine is being inefficient since that comes from unburnt exhaust gases.]

first off high egt's result from a too-lean condition, to a certain point. upon detonation, egt's actually drop. you could be thinking about a turbocharged diesel or gas engine. the reason you are concerned about egt's in those is you dont want to burn up the turbo. being too rich or incomplete combustion could cause high egt b/c the unburnt fuel will ignite in the turbo. turbo's get really hot y'know. but the egt between the turbo and engine will be lower. on a n/a engine though you want high egt's for max power and efficiency. high temp is indicative of more fuel being burned, more energy. if the fuel into the engine is constant, then the higher the egt the better.


Another quote:
[The equation is for Otto thermal efficiency: Nth = 1 - Wnet/Qin

To make this number as high as possible, Qin (heat in) needs to be as high as possible. The waste heat to the radiator and atmosphere is energy that doesn't get sent through the driveline. It's wasted energy, but a good way to reclaim some of that wasted energy is with a turbo.

In no way does this have anything to do with oxygen density or airflow velocity. I'm not saying that it isn't related. I was just mentioning the interesting opposition of what one engineering equation tells us and what shade tree mechanics have know for years.]


My rebuttal:

the Otto cycle beginning after the intake stroke:

Process 1 - 2: an isentropic compression of the fuel-air mixture from bottom dead-center to the minimum volume, compression stroke, so, lets say ambient air temp (T1) enters the engine and is compressed isentropically to a (T2)

Process 2-3: a constant-volume combustion process, the air/fuel mixture igniting, this will add a tremendous amount of heat and result in (T3) all of this heat is converted from chemical energy in the fuel


Process 3-4: an isentropic expansion of the products of combustion to bottom dead center, power stroke, results in (T4) isentropic means constant potential temperature or adiabatic, no heat added or taken away, but the temp does decrease due to expansion


Process 4-1: a constant-volume heat rejection process until the temperature and pressure reach initial conditions. a little confusing but process 4-1 is actually the exhaust stroke and intake stroke, remember, we started at BDC on the compression stroke


The thermal efficiency of this cycle is found as the net work delivered by the cycle, divided by the heat added to the working substance. From this definition of the cycle thermal efficiency, we may write:

Nth = Wnet / Qadded or 1-Qrej/Qadded this was mentioned earlier, kind of

Since the constant volume heat rejection is equal to the change of internal energy in process from state 4 to state 1, and the heat added in a constant volume process from state 2 to state 3 is the change of internal energy netween these two states, we may write for the case of constant specific heats:



Nth = 1 - T1 / T2 * (T4 / T1 - 1 ) / ( T3 / T2 - 1 )

so: Qadded = (T3/T2-1)

Qadded is the amount of heat added to the process during combustion. the chemical energy from the fuel converted into heat energy. Qadded is not the heat you add from the intake charge. in the above equation, if you raise T1 it lowers the efficiency. however, in application the heat of T1 would carry throughout the process and it would not change the efficiency.

basically: the reason an engine makes more power with a cooler intake charge is because the air is denser and there is more molecules of air to react with the molecules of fuel and being a more dense charge raises the dynamic compression ratio. thats it.
warm air actually flows better because its density is lower.

this is long enough, please dont criticize any mistakes in the equations or whatnot, i dont feel like checking it, my point is Qadded does not tell you that higher intake temps are better. it tells you more fuel is better. you cant simply add more fuel though. you have to add more air.

so taking this into account:


Qadded = CNC ported heads, huge cam, and mongoloid injectors

betcha didnt know that :flipoff2:



if im totally wrong on any of this please let me know and ill get a book out and correct myself.

[eight]

What makes the most power and what makes the most effiency are two different things.

[AgDieseler]

Originally posted by agjohn02
first off high egt's result from a too-lean condition, to a certain point.

basically: the reason an engine makes more power with a cooler intake charge is because the air is denser and there is more molecules of air to react with the molecules of fuel and being a more dense charge raises the dynamic compression ratio. thats it.
warm air actually flows better because its density is lower.

this is long enough, please dont criticize any mistakes in the equations or whatnot, i dont feel like checking it, my point is Qadded does not tell you that higher intake temps are better. it tells you more fuel is better. you cant simply add more fuel though. you have to add more air.

EGTs on diesels increase linearly (roughly) with fuel rate in naturally aspirated conditions, so that explains my confusion with gas engines.

So it's not the Qin from the air that needs to be high, but from the fuel. With a cooler intake charge there's more oxygen to burn more fuel - thus a higher Qin. Got it. I was looking at things from the viewpoint that the engine strictly pumped air (since that's how we always solved problems in class), but now I understand.

[stx4wheeler]

Originally posted by Snatch Adams
The real question is, did you see them hollow out the cats, hell, I dont even know how you hollow out a cat.



no jerry you need to learn to read better it would have cost me eighty dollars to put in two new cats, they only charged me five for the other hollwed cat they installed i am a big *** and was pretty sure that paying five dollars was a lot better than 80.

[agjohn02]

Originally posted by eight
What makes the most power and what makes the most effiency are two different things.


you're partly correct...

the thermal efficiency of an IC engine can be expressed as power out divided by the power in.

Nth= Wout/Win

in our case, work out is the amount of energy an engine produces and work in is the amount of chemical energy we put into the engine via fuel. if you increase one variable without changing the other then it will change the efficiency. Wout is directly proportional to Nth and Win is inversely proportional to Nth. so, as Wout increases efficiency increases. if the jets in a carb and the pulse width and fuel pressure in a efi engine arent changed, then Win doesnt change., but we can play with timing to run more efficiently and make more power. in a given engine with no mechanical modification and tuning only, max efficiency and max power are synonymous.

now, if you want max power from an engine regardless of modifications necessary you have to increase BMEP, brake mean effective pressure. BMEP is the average pressure that works against the piston top throughout the 4 stroke cycle. during power stroke this is positive in relation to motion. during the three other three stokes, the pressure in the cylinder is working against motion. so, you want to increase pressure during the power stoke and decrease it during the intake and exhast strokes (i.e.- better breathing=less pumping losses). decreasing pressure during the compression stroke would be more counter productive than anything else, so even though it works against power output, it more than makes up for itself during the power stroke. BMEP is what creates torque and HP is simply torque multiplied by a time and distance, how quickly the torque can move a given force a certain distance in the least amount of time. you can increase torque one of four ways. by increasing dynamic compression ratio, increasing stroke (the distance BMEP works), increasing the area of the piston top (pressure x area = force), or increasing the RPMs (which will decrease the time that BMEP is working). since the last three involve major modifications and would result in pretty much a different engine and for the sake of brevity, ill only talk about increasing dynamic compression ratio.

you can change DCR one of two ways. first, increasing the volumetric compression ratio. this is what you see referred to as 10:1, 11:1 and so on. this is a geometric calculation but does not mean you'll get that much compression during operation. for example, if you had a 10:1 CR and the intake runner was 1/4" in diameter, there is no way the cylinder would be filled when the intake valve closes. you would be starting the compression stroke with a negative pressure in the cylinder, not atmospheric. to increase DCR you must either increase CR or get as much air into the cylinder during the intake stroke as possible. this is one of the easiest modifications to do outside of proper tuning. anything that makes the engine breath better will help with DCR. the term that drives DCR is volumetric efficiency. this is the amount of air that actually fills the cylinder compared to the amount of air that is needed to fill the cylinder to atmospheric pressure. if an engine completely fills the cylinder to ambient pressure before the intake valve closes, then it is said to have 100% VE. forced induction engines can exceed 100% because the manifold pressure is above that of atmospheric. with 15 psi boost on pump gas, 200% VE is easily achieveable. a 350 sbc with 200% VE will flow as much air as a n/a 700 cu engine. therefor, it will be able to burn the same amount of fuel and produce the same amount of torque. horsepower will differ b/c the geometry and speed of the engine will differ. this is why they say that forced induction effectivly increases your displacement by a factor of two. typical small block engines operate between 80-100% VE with the latter being in the high performance arena where low end performance is sacrificed. some extremely well built high performance naturally aspirated engines can exceed 100% by taking advantage of the ramming effect brought on by high intake air velocities. this essentially results in a (slighty) higher than ambient pressure in the cylinder, possibly up 105% VE. when you increase VE you have more air in the cylinder for fuel to react with, so you need more fuel. in order to get more fuel you have to change the jetting on a carbed engine and the fuel pressure and/or pulse width on an efi engine. this decreases economy but not efficiency if the engine is performing where it should.

really, the only way to make an engine of said displacement get better gas mileage is to make it run at max efficiency, which im pretty sure its close to doing in the case of the 5.3l vortec. the next step is to reduce pumping losses, because an engine really is just a big air pump. better breathing is the answer to this. the PCM will be able to modify fuel and spark curves for any cheap modification you will make. frictional losses play a big part in power loss as well. the only easy and cheap way to do this is follow grayson's advice and run sythetic oil. there are many ways to do this internally, none of which are cheap or easy. gaining proper alignment and clearancing, teflon coatings and proper lubrication are all expensive and labor intensive operations. all this applies to making the engine more efficient. if you were trying to make it more economical you would need to reduce the displacement, therefor reducing the fuel requirment and potential power output. for the answer on how to do this, refer to my previous post.

in conclusion: efficiency and power are one in the same if you take into account the actual definition of efficiency. your statement would be better worded, "What makes the most power and what makes the best economy are two different things."

efficiency=power

[eight]

Ok I didn't read all that cause I gotta go shoot at somethin or make sure the jet ski still runs or somethin.... but yea, they can be related, and often are, but not allways. Like a cam with lots of duration makes lots of power but wastes some fuel, and tuning the air/fuel mixture to make the most power will cost more fuel than running it a little lean.

[agjohn02]

Originally posted by eight
Ok I didn't read all that cause I gotta go shoot at somethin or make sure the jet ski still runs or somethin.... but yea, they can be related, and often are, but not allways. Like a cam with lots of duration makes lots of power but wastes some fuel, and tuning the air/fuel mixture to make the most power will cost more fuel than running it a little lean.


you're right on both accounts in the last sentence, but only the last sentance.

furthermore, if you're going to waste my time, try to make fun of me for doing it, and not read my post then why argue with me. im not cack measuring here. i just like to see gobs of good tech thrown around in the tech section of a forum.

the reason a cam with larger duration uses more fuel is because it increases the volumetric efficiency of the engine, needing more fuel to run efficiently. it will actually run at low efficiency at low rpms b/c of the increased valve overlap. you essentially are letting fuel out the exhaust valve before it even gets a chance to get burned. it significantly reduces DCR at low rpms, thats why big cams idle rough and make less power down low. at high rpms its a different story b/c the cam is made to operate there. engines have to be tuned for their intended use.

by playing with the AF ratio you are changing the (potential) efficiency of the engine. if you let either unburnt fuel or oxygen out the exhaust, then you are decreasing the engines efficiency. both elements are a potential energy source. if you circulate o2 through the engine without burning it, you are losing power to unecessary pumping losses. running lean leaves oxygen in the exhaust that could be used to burn more fuel. by fattening the mixture up you are burning the most fuel that amount of air will allow. lambda (the dimensionless variable the o2 sensor produces) for best ECONOMY is 1.05 or 15.4 parts air to 1 part fuel, this of course will reduce power output but get best gas mileage. however, by running lean you are essentially selling yourself short and not running at the engines potential efficiency. lambda for best power is 0.9 or 13.2:1 a/f ratio. for reference, a stoichiometric a/f ratio is 14.7:1 which is what most stock engines run at b/c it is a nice midway between max power and max economy. by tuning for a lambda of 0.9, you are burning the most fuel possible without letting any unburnt fuel leave the exhaust. so, while a lambda of 0.9 will net the best efficiency, it will also produce more power. these lambda values are for a narrow band o2 sensor (0-1.1v) as this is all i have experience tuning with. i would assume that the new vortecs have wide band o2 sensors(0-5v) so different lambda values are expected. to further answer the original question of the thread... a PCM retune for best economy could be done, but not cheaply. if you showed up at a performance place and told them this is what you wanted they would probably laugh at you anyways. maybe i just got too far off topic talking about efficiency, when this thread is really about economy. its evident that eight and i both understand how to tune an engine. we are just dissagreeing on the definition of these two words. so, to end this pissing match we've got going here and get back on topic, I'll let Mr. Webster have the last word.

economy (i-kon'e-me)- 1. the careful or thrifty management of resources

efficiency (i-fish'en-se)- 2. the ratio of the effective or useful output to the total input in any system.




edited because i forgot to say, "dont argue with me because i am a MASTER deBATER."

[agjohn02]

Originally posted by BigRedFord04
i understand where you're coming from kopecki, but i dont see how extracting more heat from the engine via the cooling system affects efficiency. that energy doesnt get used anyway does it?

this one will be quick i promise.

if the cylinder walls are hot then less heat can transfer from the burning mixture to the cooling system. if they are cool, then the heat differential is less and more heat can easily transfer into the cooling system. think of heat as air pressure, high to low pressure is easy, high to high is hard. heat that passes through the heads and cylinder walls doesnt get used to drive the piston.

[usmcagg02]

well that is definatley more info that i was expecting to get. thanks everyone for the input. i'm gonna throw down some money one a new exhaust for one. and i've also thought about wrapping the air intake tube in something like header wrap to try and keep engine temps from affecting it. i'll let y'all know how it goes when i get it all done(which may be a few weeks)

almost forgot, while i'm sure that everyone know's austin's opinion on the best exhaust shop in town:flipoff2: i was wondering if anyone else had a stong preference. at the moment i am kinda just considering mail ordering one and putting it on myself unless i can find a better deal.

[BigRedFord04]

Originally posted by usmcagg02
almost forgot, while i'm sure that everyone know's austin's opinion on the best exhaust shop in town:flipoff2: i was wondering if anyone else had a stong preference.
just go to McAlister's....i hear they use some badass stainless stuff. Or the one on the very end of College on the right (Bryan Muffler?)...nothing they install EVER leaks :rolleyes: :rolleyes: :rolleyes:


.....fawker :flipoff2: :flipoff2:

[usmcagg02]

do you know what kinda prices they charge for true dual with h-pipe?

[uglyota]

why do you want a true dual? You'd have to start ahead of the cat and rebuild the entire exhaust (b/c I'm pretty sure your truck only has 1 cat) which would mean you would need to put in 2 smaller-diameter cats, figure out how to keep the O2 sensors from getting confused, then 2 mufflers, then have a bunch of pipe bent to get it around your spare tire. Why not go with a Borla or Banks side-exit single exhaust? what I'm trying to say is that "true dual" is not always the best option

[stinger7401]

actually from what i understand, in all the bigger cities with the smog problems and laws its getting harder to find places that will actually run the "true" dual setup, at least in SA where there are no laws yet its impossible to find a shop that will do it for a paying customer

[Broncocustom]

Never impossible in SA. take cash to one of those yellow mexican muffler shops down on the south part of town by military drive. Then you find a local shop that does inspections that do not require the engine running.

[usmcagg02]

Originally posted by uglyota
why do you want a true dual? You'd have to start ahead of the cat and rebuild the entire exhaust (b/c I'm pretty sure your truck only has 1 cat) which would mean you would need to put in 2 smaller-diameter cats, figure out how to keep the O2 sensors from getting confused, then 2 mufflers, then have a bunch of pipe bent to get it around your spare tire. Why not go with a Borla or Banks side-exit single exhaust? what I'm trying to say is that "true dual" is not always the best option

for some reason i wanna say that i have seen two cats, but i havent even seen my truck in 4 months so i cant be positive. i'll have to look when i get back. if not then i guess i will just go with reagular dual exhaust. as for borla or banks=$$$$$.

[Fredo]

Originally posted by usmcagg02
for some reason i wanna say that i have seen two cats, but i havent even seen my truck in 4 months so i cant be positive. i'll have to look when i get back. if not then i guess i will just go with reagular dual exhaust. as for borla or banks=$$$$$.

Hey, try reading the first page of the ****ing thread...


Originally posted by Fredo
You're telling me it's a good idea to hollow out all FOUR cats on a 5.3L chevy? You're also saying that the computer won't figure it out and trip the check engine light, or even pass inspection?

[usmcagg02]

Hey, try reading the first page of the ****ing thread...


i finally got back an was able to check, i do have two cats on my truck like i thought. where did you hear that chevy's came stock with 4?

[BMFScout]

unless longbeds or some other **** is different, they only have two that I can see. There might be one hiding inside the manifolds or in the pipe itself ;) It does however have four O2 sensors, one before and one after the cat on each side. I have heard that they flow well and there is no reason to **** with them. True dual would be wicked easy to do though, because it is true dual right up until it empties into the 55 gallon drum muffler. Then some chrome "boom tubes"!!

[uglyota]

True dual would be wicked easy to do though, because it is true dual right up until it empties into the 55 gallon drum muffler. Then some chrome "boom tubes"!!
yeah, but they both dump into the muffler on the passenger side, so if you want twice pipes, you need to force half of that exhaust back across the truck to the driver's side...just so you can have a pretty pipe coming out of each side of your bumper. If you're really going for performance/efficiency/etc, dump them both on the right side.

[jerryg79]

yeah, but they both dump into the muffler on the passenger side, so if you want twice pipes, you need to force half of that exhaust back across the truck to the driver's side...just so you can have a pretty pipe coming out of each side of your bumper. If you're really going for performance/efficiency/etc, dump them both on the right side.


Who cares about pretty if you want cheap, go buy two flows and dump them before the axle. DUMPS LIKE A TRUCK! :cheers:

[jerryg79]

until it empties into the 55 gallon drum muffler

Which by the way makes for good target practice with a .45 when you are done. Don't shoot the end though, it wont go through :D

[Fredo]

i finally got back an was able to check, i do have two cats on my truck like i thought. where did you hear that chevy's came stock with 4?

I was thinking of the old body style vortec trucks....they have 4 cats on them. Oh well.

[uglyota]

Who cares about pretty if you want cheap, go buy two flows and dump them before the axle. DUMPS LIKE A TRUCK! :cheers:
...or the 2-in, 1-out they make just for chevys
http://www.jeepyj.net/tamor/www/members-rigs/albums/album01/rusty_muffler.jpg


I was thinking of the old body style vortec trucks....they have 4 cats on them. Oh well.
Not tryin to bust your balls, but my 97 only has 2 ;)

[Fredo]

hmm....then why does my mother's 99 have 4 and my oldest brother's 96 have 4?

[uglyota]

Oh my god! There's 3 Brune brothers?
weird... :D
Perhaps your mom and brother are extremely environmentally conscious, and had them put on "just in case" there were a few hydrocarbons the first one missed :confused:
I'll ask her tonight :flipoff2:

[Fredo]

Well, they might be there and you just aren't looking for them. They are small and they hang out right behind the manifolds on the exhaust sytem, then further downstream there are two more....or maybe I'm smoking the good **** today....I don't know.

[uglyota]

either my truck's been modified (very possible...had twice pipes when I got it) or you're smoking the mota buena...unless the "secret cats" are cast and disguised as manifolds :eek:

[eight]

I'd throw on a pair of long glass packs, and H pipe, and dump it before the axle and hope its not too loud. My 4" dump also keeps the axle from rusting. :D

[agjohn02]

either my truck's been modified (very possible...had twice pipes when I got it) or you're smoking the mota buena...unless the "secret cats" are cast and disguised as manifolds :eek:


the hunting lodge i worked at was named Mota Bonita. in old school spanish it means beautiful group or trees, but not in tex-mex. you shoulda seen the looks i got in town when i told them where i worked. mind you, in falfurrias, everyone speaks spanglish and smokes mota.

is that flow on your truck? im wanting one for the skizzout but i dont want anything too loud, i got tired of the drone of the old turbos. hows it sound?


my old 96 tahoe 5.7 vortec has two cats and my mom's 03 5.3l suburban has two. i think you got a bad batch of brownies fred. are you sure you're not thinking about 02 sensors? what you're saying sounds familiar, as in i think ive seen it before, but really though, whats the point in four cats? four 02's i understand but...

[jmancuso]

You may want to check out some of the new products from Kalecoauto http://www.kalecoauto.com/general.htm

[BigRedFord04]

You may want to check out some of the new products from Kalecoauto http://www.kalecoauto.com/general.htm
:flipoff2:

[uglyota]

the hunting lodge i worked at was named Mota Bonita. in old school spanish it means beautiful group or trees, but not in tex-mex.

is that flow on your truck? im wanting one for the skizzout but i dont want anything too loud, i got tired of the drone of the old turbos. hows it sound?

another fun fact: a small group of trees, particularly oaks, such as is found in our post-oak savannah, is called a "mott." Coincidence?

Yeah, that's a flowmaster on my truck. Sounds pretty good, a lot deeper than the dual flows I had on it before, but almost no backpressure. I think I lost some low-end torque. It was my cheapest option and that's why I did it, but I think flowmasters suck and rust out quick and I would choose any brand of muffler over a flowmaster any day. That should mean something coming from someone who's now on his 4th and 5th flowmaster.

[agjohn02]

[QUOTE=uglyota]another fun fact: a small group of trees, particularly oaks, such as is found in our post-oak savannah, is called a "mott." Coincidence? [QUOTE]

yeah, thats what we called all the clusters of live oaks on the king ranch. i.e.- the "big mott" in the east azul pasture was a big landmark. i walked through it a couple of times looking for large plots of skrilla but with no luck. if you want weed down there you have to find the mexicans that are smuggling it across the ranch in duffle bags. my boss's bird dog pointed 115 lbs of the good stuff last year that some poor, probably dead now, guys left out there.

[uglyota]

haha no wonder you decided to wander around King Ranch instead of getting a real job :cheers:

[usmcagg02]

You may want to check out some of the new products from Kalecoauto http://www.kalecoauto.com/general.htm


and if you are interested i can sell you a left-handed screwdriver :p