31 MPG
Thread Starter
5th Gear Member
Joined: Apr 2004
Posts: 3,026
From: CA
31 MPG
I saw that the new 2010 v6 Mustang will get 31 MPG and this was the first 300hp car to do this but someone pointed out the LS1 and LS2 had already done this? Car review sites like edmunds say the vette is getting 19 - 20mpg but corvettes on youtube are getting 30MPG and so are cars on the vette forums.
How does the vette do it? is it really that tall 6th gear? cause I have a lot less HP and 2.73 gear 4speed auto, im running under 2K RPMs at 65 and I am no where near 31 MPG. Is it multi factors? aero/weight/gear/injectors?
what gives?
How does the vette do it? is it really that tall 6th gear? cause I have a lot less HP and 2.73 gear 4speed auto, im running under 2K RPMs at 65 and I am no where near 31 MPG. Is it multi factors? aero/weight/gear/injectors?
what gives?
5th Gear Member
Joined: Jul 2003
Posts: 3,451
From: United States
Practically everything. The gearing, car weight, aerodynamics, a/f ratio, frictional losses, rotating weight, & the engine design.
To make more power you can use higher rpm or bigger displacement (not factoring in boltons or force induction). Ford chose to go the higher rpm with smaller displacement route, in doing so their engines are built to be more efficient at higher rpms. GM chose to make their engine more efficient at lower rpm & use displacement to get more power. If you try to get more power at higher rpm you cause efficiency to drop at lower rpm. variable runners & valve timing has helped somewhat, but you're still unable to change a majority of the engine. In an ideal world everything on an engine would be variable in size.
Most newer cars can gain some fuel economy by changing the tune. For example, most car companies try to run close to 14.7:1 a/f ratio at cruise because of emissions. less emissions are produced at stoich. It's wasteful but better for the environment. For higher fuel economy you want to run as lean as possible without surging. Most people say you can't because that number is pounded into everyones mind, in all actuality there isn't enough air & fuel in the cylinders to produce enough heat to cause damage. On the cars I've tuned I've ran up until it surges then backed it off a couple points. One of mine runs at 16.7:1 at cruise, 12.2:1 at wot.
There's a car company that took a common engine that gets 15-20mpg in their vehicle, modified the engine & are getting 500hp & 70mpg at interstate speeds & that's in a 3200lb car. They were aiming for that though & that's not even a hybrid.
To make more power you can use higher rpm or bigger displacement (not factoring in boltons or force induction). Ford chose to go the higher rpm with smaller displacement route, in doing so their engines are built to be more efficient at higher rpms. GM chose to make their engine more efficient at lower rpm & use displacement to get more power. If you try to get more power at higher rpm you cause efficiency to drop at lower rpm. variable runners & valve timing has helped somewhat, but you're still unable to change a majority of the engine. In an ideal world everything on an engine would be variable in size.
Most newer cars can gain some fuel economy by changing the tune. For example, most car companies try to run close to 14.7:1 a/f ratio at cruise because of emissions. less emissions are produced at stoich. It's wasteful but better for the environment. For higher fuel economy you want to run as lean as possible without surging. Most people say you can't because that number is pounded into everyones mind, in all actuality there isn't enough air & fuel in the cylinders to produce enough heat to cause damage. On the cars I've tuned I've ran up until it surges then backed it off a couple points. One of mine runs at 16.7:1 at cruise, 12.2:1 at wot.
There's a car company that took a common engine that gets 15-20mpg in their vehicle, modified the engine & are getting 500hp & 70mpg at interstate speeds & that's in a 3200lb car. They were aiming for that though & that's not even a hybrid.
Thread Starter
5th Gear Member
Joined: Apr 2004
Posts: 3,026
From: CA
Practically everything. The gearing, car weight, aerodynamics, a/f ratio, frictional losses, rotating weight, & the engine design.
To make more power you can use higher rpm or bigger displacement (not factoring in boltons or force induction). Ford chose to go the higher rpm with smaller displacement route, in doing so their engines are built to be more efficient at higher rpms. GM chose to make their engine more efficient at lower rpm & use displacement to get more power. If you try to get more power at higher rpm you cause efficiency to drop at lower rpm. variable runners & valve timing has helped somewhat, but you're still unable to change a majority of the engine. In an ideal world everything on an engine would be variable in size.
Most newer cars can gain some fuel economy by changing the tune. For example, most car companies try to run close to 14.7:1 a/f ratio at cruise because of emissions. less emissions are produced at stoich. It's wasteful but better for the environment. For higher fuel economy you want to run as lean as possible without surging. Most people say you can't because that number is pounded into everyones mind, in all actuality there isn't enough air & fuel in the cylinders to produce enough heat to cause damage. On the cars I've tuned I've ran up until it surges then backed it off a couple points. One of mine runs at 16.7:1 at cruise, 12.2:1 at wot.
There's a car company that took a common engine that gets 15-20mpg in their vehicle, modified the engine & are getting 500hp & 70mpg at interstate speeds & that's in a 3200lb car. They were aiming for that though & that's not even a hybrid.
To make more power you can use higher rpm or bigger displacement (not factoring in boltons or force induction). Ford chose to go the higher rpm with smaller displacement route, in doing so their engines are built to be more efficient at higher rpms. GM chose to make their engine more efficient at lower rpm & use displacement to get more power. If you try to get more power at higher rpm you cause efficiency to drop at lower rpm. variable runners & valve timing has helped somewhat, but you're still unable to change a majority of the engine. In an ideal world everything on an engine would be variable in size.
Most newer cars can gain some fuel economy by changing the tune. For example, most car companies try to run close to 14.7:1 a/f ratio at cruise because of emissions. less emissions are produced at stoich. It's wasteful but better for the environment. For higher fuel economy you want to run as lean as possible without surging. Most people say you can't because that number is pounded into everyones mind, in all actuality there isn't enough air & fuel in the cylinders to produce enough heat to cause damage. On the cars I've tuned I've ran up until it surges then backed it off a couple points. One of mine runs at 16.7:1 at cruise, 12.2:1 at wot.
There's a car company that took a common engine that gets 15-20mpg in their vehicle, modified the engine & are getting 500hp & 70mpg at interstate speeds & that's in a 3200lb car. They were aiming for that though & that's not even a hybrid.
Thread Starter
5th Gear Member
Joined: Apr 2004
Posts: 3,026
From: CA
I was always under the impression that a catalytic converter was the miracle cure all for emissions,
C02 and water rather then CO and NOX..
anyway. Can I get my car tunes to run dryer like that and boost my MPG by 5 or 6 ? also.. I dont understand how less petro with the A/F results in MORE pollution then MORE petro and air.
C02 and water rather then CO and NOX..
anyway. Can I get my car tunes to run dryer like that and boost my MPG by 5 or 6 ? also.. I dont understand how less petro with the A/F results in MORE pollution then MORE petro and air.
6th Gear Member
Joined: Apr 2007
Posts: 10,468
From: California
Leaner a/f ratios produce 2 things that result in greatly increased emissions. 1 is it produces more NOx, which is extremely bad for the environment(probably the worst of all vehicle emissions), the second is it causes the excess O2 to result in the cat favoring the oxidation reactions(converting HC and CO to CO2 and H2O) at the expense of the reductio reaction(converting NOx to N2 and O2). That means that as the car runs leaner and produces more NOx, the cat at the same time is losing the effectiveness to eliminate those NOx emissions. The result is greatly increased NOx pollution, though HC and CO emissions are eliminated completely. The reverse is also true, as you run richer, NOx is eliminated, but CO and HC emissions increase.
Thread Starter
5th Gear Member
Joined: Apr 2004
Posts: 3,026
From: CA
Leaner a/f ratios produce 2 things that result in greatly increased emissions. 1 is it produces more NOx, which is extremely bad for the environment(probably the worst of all vehicle emissions), the second is it causes the excess O2 to result in the cat favoring the oxidation reactions(converting HC and CO to CO2 and H2O) at the expense of the reductio reaction(converting NOx to N2 and O2). That means that as the car runs leaner and produces more NOx, the cat at the same time is losing the effectiveness to eliminate those NOx emissions. The result is greatly increased NOx pollution, though HC and CO emissions are eliminated completely. The reverse is also true, as you run richer, NOx is eliminated, but CO and HC emissions increase.
6th Gear Member
Joined: Apr 2007
Posts: 10,468
From: California
That's why factory tunes often leave a lot of power on the table. They're set up to control AFR and EGT to produce decent power and mileage, but keep the cat operating in it's ideal range for emissions reduction. Running outside that AFR range can also cause the cat to get hot and melt, and emissions laws require cat life as part of the emissions systems to be warrantied for the life of the vehicle.