increase gas mileage
Registered User
Joined: Feb 2000
Posts: 1,445
From: Seattle, WA
tuning and headers will help... mostly due to flow increases. Less throttle to maintain the same rpm... that's what efficiency gets you and it's also how you gain hp from such designs. Ditching the heavy-*** iron manifolds doesn't hurt either.
exhasut and CAI does help mpg... it's been shown repeatedly.
Swapping to a more agressive cam won't help at all... although I'm not sure what effect a larger TB would have. It would SEEM that it could help (along the same lines that headers do), but the greater air-flow also means less control-able air deliver at low-thottle positions (shouldn't change idle at all though). I'd think the TB would just make it that much easier to get "into it" accidentally and shoot your mpg back down from any gains it may have had.
higher tire pressures and sticking to skinnier tires (like 245's instead of 275's) helps reduce rolling friction... extreme steps would include light-weight wheels (like 205's on forged alluminum 16" rims
), LT1 brakes (smaller rotors/weight than LS1), and an aluminum flywheel and driveshaft.
Dropping rotational and static weight will always help... especially if you live in mountainous or hilly areas.
Moving to the mid-west also helps a lot.... we get ~3mpg less with the Oldmobile in the Seattle area than we ever did while driving in Saskatchewan. Hill climbs take a fair amount of throttle and therefore gas.
Essientally the headers and lightweight drivetrain is the only stuff that's fun... everything else to save mpg is a pain.
exhasut and CAI does help mpg... it's been shown repeatedly.
Swapping to a more agressive cam won't help at all... although I'm not sure what effect a larger TB would have. It would SEEM that it could help (along the same lines that headers do), but the greater air-flow also means less control-able air deliver at low-thottle positions (shouldn't change idle at all though). I'd think the TB would just make it that much easier to get "into it" accidentally and shoot your mpg back down from any gains it may have had.
higher tire pressures and sticking to skinnier tires (like 245's instead of 275's) helps reduce rolling friction... extreme steps would include light-weight wheels (like 205's on forged alluminum 16" rims
), LT1 brakes (smaller rotors/weight than LS1), and an aluminum flywheel and driveshaft.Dropping rotational and static weight will always help... especially if you live in mountainous or hilly areas.
Moving to the mid-west also helps a lot.... we get ~3mpg less with the Oldmobile in the Seattle area than we ever did while driving in Saskatchewan. Hill climbs take a fair amount of throttle and therefore gas.
Essientally the headers and lightweight drivetrain is the only stuff that's fun... everything else to save mpg is a pain.
Registered User
Joined: Jun 2001
Posts: 268
From: Crown Point,IN,US of A
While on the subject... somthing MUST be wrong with my car... why am i getting 180 per tank city... while driving slow.
B&B Tri Flo cat back, K&N intake, new trans, 255/50/16, programer....
I knew my mpg was bad.. but you guys are talking 300... THATS ALMOST DOUBLE!
B&B Tri Flo cat back, K&N intake, new trans, 255/50/16, programer....
I knew my mpg was bad.. but you guys are talking 300... THATS ALMOST DOUBLE!
Registered User
Joined: Mar 2002
Posts: 2,743
From: Baton Rouge, LA, USA
Originally posted by YZF/LS1 Freak
I heard descreaning the MAF helps some because it leans the car out a little more because LT1's come a little rich from the factory.
On my last f-body an 86 Camaro with a 2.8 I went from 18mpg to 28 (I kid you not).
I heard descreaning the MAF helps some because it leans the car out a little more because LT1's come a little rich from the factory.
On my last f-body an 86 Camaro with a 2.8 I went from 18mpg to 28 (I kid you not).
And if your 2.8 only got 18 mpg stock, there was something terribly wrong with it. The Accell ignition was no better than a good stocker, but your stock ignition was worn out, thus killing the mileage. My old '89 305 TBI got 28 mpg stock, even with the "junk stock ignition".
Originally posted by Farc
Gears for sure.
Gears for sure.
Originally posted by Steve in Seattle
exhasut and CAI does help mpg... it's been shown repeatedly..
exhasut and CAI does help mpg... it's been shown repeatedly..
Mike
Registered User
Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Originally posted by engineermike
II don't see how exhaust or intake mod's would help gas mileage. At cruise, the air flow through the engine is very low since maintaining speed may require as little as 20 hp, so the exhaust and intake tract are plenty big enough.
II don't see how exhaust or intake mod's would help gas mileage. At cruise, the air flow through the engine is very low since maintaining speed may require as little as 20 hp, so the exhaust and intake tract are plenty big enough.
-Mindgame
Registered User
Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by Dreadsen
Well I should have went further into detail of what i'm trying to accomplish.
I looking into buying a 1995 Caprice Wagon for it's space and towing ability for my Courier business.
It has an LT1 in it.
I have a 91 Camaro and a 97 SS with lots of work done to them for racing. So i have no interest in turing this station wagon into a drag car.
I picked up three contracts with three airlines to deliver their lost luggage to their customers. Paying $1.10 a mile. Most truck owners only get .80 cents a mile and those huge trucks burn a lot more gas then a car does.
So YES if long tubes along with a combination of other things can raise the miles per gallon from 16 to 21 or even more then i'll look into getting some installed.
The main goal is to bring operating costs per vehicle as low as possible.
Well I should have went further into detail of what i'm trying to accomplish.
I looking into buying a 1995 Caprice Wagon for it's space and towing ability for my Courier business.
It has an LT1 in it.
I have a 91 Camaro and a 97 SS with lots of work done to them for racing. So i have no interest in turing this station wagon into a drag car.
I picked up three contracts with three airlines to deliver their lost luggage to their customers. Paying $1.10 a mile. Most truck owners only get .80 cents a mile and those huge trucks burn a lot more gas then a car does.
So YES if long tubes along with a combination of other things can raise the miles per gallon from 16 to 21 or even more then i'll look into getting some installed.
The main goal is to bring operating costs per vehicle as low as possible.
So, if you are towing a trailer with lost luggage in it, you need to keep the trailer LIGHT with minimum number of axles and a shape that doesn't rise above the wagon. If you aren't towing, get something with more cubic volume and less engine, like a van. There is a reason UPS, FedEx, etc. use large cube, low powered vehicles.
IMO, the 350 LT1 Caprice is overkill and not a high mileage combination for it's capacity. However, if you MUST use it, here are some thoughts:
Strip out all the seats, etc except for the driver's for weight reduction and more space. Remove the spare, and consider a covered roof carrier for around town delvieries to increase payload. Only use it or a trailer when you absolutely need to.
Make sure you have lowest numerical rear gear available (unless towing or in the mountains). 2.73s probably or maybe 2.56s. Make sure airdam under front end is still in good shape both for cooling and lower drag on the highway.
Run hard skinny tires, like those "guaranteed" for 80,000 miles. Get a good wheel alignment. Run tires at as high a pressure as you can stand, but not above tires rated max. If you are hitting lots of potholes, yo may have to back down to 35 or so.
Put on a freeflowing muffler(s) like a Dynomax Ultraflow. The rest of the system is fine because you aren't going to run this thing past 3000. Put in a good oiled cotton air filter like K&N or Air Hog, etc. New plugs and wires will help. So will synthetic oil, and it's good for 15K.
Keep you foot out of it. Add a cheap tach. Practice driving for economy and it will become second nature. Drive so the engine stays between 1500 and 3000, and most often between 2500 and 2000. Use cruise at every opportunity. Keep that barge under 65 and above 40 as much as possible. Always use OD and make sure TC is locking up. Forget underdrive pulleys. Keep the engine r's down and the accessories off!
Shut off the engine at every delivery. You want engine to be up to operating temp, but idling uses lots of fuel in a 350.
Don't use air conditioning unless you absolutely have to.
Plan your delivery route. A few minutes chosing the best routes to your destinations especially in rush hour will pay dividends. You might consider a GPS nav system if you are in a metro or rural area.
Run 87 octane gas. Consider trying various on and off brands to see if there is a difference. Log all gas purchases and odom readings so you can make ratiional decisions.
In metro/rural, non-mountains, you might average 20 mpg. If towing, stop and go, hills, etc, expect 15 or less. This is overall say for a year. If you can't make a profit with these numbers, consider a different vehicle or renegotiate the contract.
My $.02
Registered User
Joined: Mar 2002
Posts: 2,743
From: Baton Rouge, LA, USA
Originally posted by Mindgame
A reduction in pumping losses generally equates to better fuel economy. A CAI and freer flowing exhaust, in my mind, should help in this area.
-Mindgame
A reduction in pumping losses generally equates to better fuel economy. A CAI and freer flowing exhaust, in my mind, should help in this area.
-Mindgame
Install a pressure gauge on your exhaust just behind the header collectors. You'll see that it builds 3 - 9 psi at WOT depending on the quality of the exhaust and rpm, but ZERO backpressure at idle and cruise. If you're pumping against zero psi, there are no losses.
Mike
Registered User
Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Originally posted by engineermike
Just how much pumping losses could there be - when the intake and exhaust systems are designed to flow enough for 250 hp, but you're only making 25???
Install a pressure gauge on your exhaust just behind the header collectors. You'll see that it builds 3 - 9 psi at WOT depending on the quality of the exhaust and rpm, but ZERO backpressure at idle and cruise. If you're pumping against zero psi, there are no losses.
Mike
Just how much pumping losses could there be - when the intake and exhaust systems are designed to flow enough for 250 hp, but you're only making 25???
Install a pressure gauge on your exhaust just behind the header collectors. You'll see that it builds 3 - 9 psi at WOT depending on the quality of the exhaust and rpm, but ZERO backpressure at idle and cruise. If you're pumping against zero psi, there are no losses.
Mike
That seems to suggest that there is some degree of pumping loss present doesn't it?
-Mindgame
Registered User
Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Gale Banks Engineering
Some people think that once airflow is increased, additional fuel must be added at all times, and that would hurt fuel mileage. This is not the case during normal driving. Increasing airflow means an engine doesn't have to work as hard to overcome pumping losses. In other words, power that was previously consumed by pumping losses will be available to do work after airflow enhancements have been made. Or, looking at this from the economy standpoint, the same amount of work can now be done while consuming less power (fuel). So in effect, what really happens is that during normal driving, fuel consumption required to achieve equal acceleration or cruising speeds will be less than before the flow enhancements were made.
Some people think that once airflow is increased, additional fuel must be added at all times, and that would hurt fuel mileage. This is not the case during normal driving. Increasing airflow means an engine doesn't have to work as hard to overcome pumping losses. In other words, power that was previously consumed by pumping losses will be available to do work after airflow enhancements have been made. Or, looking at this from the economy standpoint, the same amount of work can now be done while consuming less power (fuel). So in effect, what really happens is that during normal driving, fuel consumption required to achieve equal acceleration or cruising speeds will be less than before the flow enhancements were made.
Here's the link
http://www.bankspower.com/Tech_Airfl...sFuelEcono.cfm
-Mindgame
Registered User
Joined: Mar 2002
Posts: 2,743
From: Baton Rouge, LA, USA
The amount of power it takes to pump a gas or liquid is directly proportional to the mass flow rate multiplied by delta pressure.
If. . . you gain 10 hp by adding a cat-back to a stock LT1, assuming the gains are due to reduced pumping losses, you are flowing 300 gm/sec air and pumping against 8 psi backpressure.
But. . . at cruise, you might be moving 30 gm/sec against .1 psi backpressure.
So. . . the part throttle gain would be somewhere around .01 hp from reduced pumping losses.
I think Gale Banks is trying to dispel the myth that more power = worst gas mileage.
Mike
If. . . you gain 10 hp by adding a cat-back to a stock LT1, assuming the gains are due to reduced pumping losses, you are flowing 300 gm/sec air and pumping against 8 psi backpressure.
But. . . at cruise, you might be moving 30 gm/sec against .1 psi backpressure.
So. . . the part throttle gain would be somewhere around .01 hp from reduced pumping losses.
I think Gale Banks is trying to dispel the myth that more power = worst gas mileage.
Mike
Registered User
Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
I think people are going to have to read the article and draw their own conclusions on this one.....
My interpretation of that is...... decreasing restrictions in the exhaust and intake improve fuel economy throughout the rpm range. An engine with freer flowing intake and exhaust will need less throttle to maintain a given speed.
Open for interpretation though... as is everything.....
-Mindgame
Gale Banks Engineering
Gasoline engines differ from diesels in that fuel is mixed proportionately to total airflow (or air mass) through the engine. Because gasoline engines are "air throttled", power output is then directly related to the total airflow through the engine at any given time. This means that after airflow enhancements have been made and pumping losses have been decreased, a gasoline engine will be able to make the same power at a lesser air throttle opening. This subject of pumping losses for gasoline and diesel engines is described in detail in "Understanding Today's Diesel". When the throttle doesn't have to be opened as far, less air mass is ingested, and that means a proportionately smaller amount of fuel is used too.
The air throttle in a gasoline engine will create a pumping restriction for the intake cycle of the engine whenever the throttle is partially closed. Consequently, under partial throttle conditions, the majority of pumping efficiency gains for gasoline engines come from exhaust flow improvements. Things in the intake system, such as air cleaner capacity and cool air induction, help most at wide open throttle, or nearly wide open throttle. An unimpeded exhaust path helps at all throttle openings.
Gasoline engines differ from diesels in that fuel is mixed proportionately to total airflow (or air mass) through the engine. Because gasoline engines are "air throttled", power output is then directly related to the total airflow through the engine at any given time. This means that after airflow enhancements have been made and pumping losses have been decreased, a gasoline engine will be able to make the same power at a lesser air throttle opening. This subject of pumping losses for gasoline and diesel engines is described in detail in "Understanding Today's Diesel". When the throttle doesn't have to be opened as far, less air mass is ingested, and that means a proportionately smaller amount of fuel is used too.
The air throttle in a gasoline engine will create a pumping restriction for the intake cycle of the engine whenever the throttle is partially closed. Consequently, under partial throttle conditions, the majority of pumping efficiency gains for gasoline engines come from exhaust flow improvements. Things in the intake system, such as air cleaner capacity and cool air induction, help most at wide open throttle, or nearly wide open throttle. An unimpeded exhaust path helps at all throttle openings.
Open for interpretation though... as is everything.....
-Mindgame
Registered User
Joined: Mar 2002
Posts: 2,743
From: Baton Rouge, LA, USA
You just quoted Gale himself saying that free flowing intakes don't help mileage, but interpret it to mean that intake AND exhaust help mileage.
Based on Gale's article, CAI's/K&N will do nothing.
All I'm saying is that gains from free flowing exhaust would be so small, the effect would be neglible, and certainly wouldn't pay for itself.
Try an economic analysis. Any modification with less than 20% rate of return isn't worth it. You could invest the money elsewhere and do better than 20%.
So. . . a $80 underdrive pulley would have to save you $16 per year.
A $300 cat-back exhaust would have to save you $60 per year.
Let's assume you're getting 20 mpg now and you'll drive 20,000 miles per year.
Fuel consumption would be 1000 gallons, or approximately $2000.
If you add 1 mpg (about what the pulley would add), you would now use $1904, or a savings of $96 per year. Not a huge sum, but the rate of return is great at 120%. How about I buy you the pulley and you give ME the savings? Too bad you can't put 5 or 6 underdrive pullies on it.
If you add a cat-back and gain 0.01 mpg (roughly equated to what I calculated above). The fuel usage would become $1999, saving $1 per year. The rate of return is 0.3% and it would take 300 years to get your money back. Why don't you give ME $2000 and I'll pay you the .3% return per year?
Mike
Based on Gale's article, CAI's/K&N will do nothing.
All I'm saying is that gains from free flowing exhaust would be so small, the effect would be neglible, and certainly wouldn't pay for itself.
Try an economic analysis. Any modification with less than 20% rate of return isn't worth it. You could invest the money elsewhere and do better than 20%.
So. . . a $80 underdrive pulley would have to save you $16 per year.
A $300 cat-back exhaust would have to save you $60 per year.
Let's assume you're getting 20 mpg now and you'll drive 20,000 miles per year.
Fuel consumption would be 1000 gallons, or approximately $2000.
If you add 1 mpg (about what the pulley would add), you would now use $1904, or a savings of $96 per year. Not a huge sum, but the rate of return is great at 120%. How about I buy you the pulley and you give ME the savings? Too bad you can't put 5 or 6 underdrive pullies on it.
If you add a cat-back and gain 0.01 mpg (roughly equated to what I calculated above). The fuel usage would become $1999, saving $1 per year. The rate of return is 0.3% and it would take 300 years to get your money back. Why don't you give ME $2000 and I'll pay you the .3% return per year?
Mike
Registered User
Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Originally posted by engineermike
You just quoted Gale himself saying that free flowing intakes don't help mileage, but interpret it to mean that intake AND exhaust help mileage.
Based on Gale's article, CAI's/K&N will do nothing.
You just quoted Gale himself saying that free flowing intakes don't help mileage, but interpret it to mean that intake AND exhaust help mileage.
Based on Gale's article, CAI's/K&N will do nothing.
Gale Banks Engineering
the "majority" of pumping efficiency gains for gasoline engines come from exhaust flow improvements
the "majority" of pumping efficiency gains for gasoline engines come from exhaust flow improvements
All I'm saying is that gains from free flowing exhaust would be so small, the effect would be neglible, and certainly wouldn't pay for itself.
Try an economic analysis. Any modification with less than 20% rate of return isn't worth it. You could invest the money elsewhere and do better than 20%.
So. . . a $80 underdrive pulley would have to save you $16 per year.
A $300 cat-back exhaust would have to save you $60 per year.
Let's assume you're getting 20 mpg now and you'll drive 20,000 miles per year.
Fuel consumption would be 1000 gallons, or approximately $2000.
If you add 1 mpg (about what the pulley would add), you would now use $1904, or a savings of $96 per year. Not a huge sum, but the rate of return is great at 120%. How about I buy you the pulley and you give ME the savings? Too bad you can't put 5 or 6 underdrive pullies on it.
If you add a cat-back and gain 0.01 mpg (roughly equated to what I calculated above). The fuel usage would become $1999, saving $1 per year. The rate of return is 0.3% and it would take 300 years to get your money back. Why don't you give ME $2000 and I'll pay you the .3% return per year?
Mike
Try an economic analysis. Any modification with less than 20% rate of return isn't worth it. You could invest the money elsewhere and do better than 20%.
So. . . a $80 underdrive pulley would have to save you $16 per year.
A $300 cat-back exhaust would have to save you $60 per year.
Let's assume you're getting 20 mpg now and you'll drive 20,000 miles per year.
Fuel consumption would be 1000 gallons, or approximately $2000.
If you add 1 mpg (about what the pulley would add), you would now use $1904, or a savings of $96 per year. Not a huge sum, but the rate of return is great at 120%. How about I buy you the pulley and you give ME the savings? Too bad you can't put 5 or 6 underdrive pullies on it.
If you add a cat-back and gain 0.01 mpg (roughly equated to what I calculated above). The fuel usage would become $1999, saving $1 per year. The rate of return is 0.3% and it would take 300 years to get your money back. Why don't you give ME $2000 and I'll pay you the .3% return per year?
Mike
Let's not get shifty on this one. The original question in all of this was, "Will a freer flowing exhaust and improvements in induction increase fuel economy?".
People are going to do the modifications anyways, so this isn't a matter of Return On Investment.
I hold my stance based on the conditions of the original question.
-Mindgame