A Proposed Solution To Gas Increase
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A Proposed Solution To Gas Increase
I just stopped by the arco gas station and noticed that the price of premium gas is up to 4.75/gallon. After being robbed of 75 dollars, I went home and did some research on air to fuel ratio maps for guys who are turboing their lexus. From my understanding, the Apexi Power Programmer regulates air to fuel ratio. Instead of using it to increase the air to fuel ratio, can we use it to decrease it? less air/ fuel= longer time before gas station visit= one happy lexus owner!
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fuel
I just stopped by the arco gas station and noticed that the price of premium gas is up to 4.75/gallon. After being robbed of 75 dollars, I went home and did some research on air to fuel ratio maps for guys who are turboing their lexus. From my understanding, the Apexi Power Programmer regulates air to fuel ratio. Instead of using it to increase the air to fuel ratio, can we use it to decrease it? less air/ fuel= longer time before gas station visit= one happy lexus owner!
Last edited by aristo2369; 06-17-08 at 07:08 PM.
#4
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Our engines run a bit rich from the factory. Adjusting the air/fuel curve may result in higher fuel economy. It's nothing new. Lots of guys with 2jz-gte swaps are getting the same, if not higher fuel economy than the stock 2jz-ge guys. Less air and fuel equates to less power, but not necessarily less fuel consumption. You need to find the optimal A/F ratio for your setup (dont ask me what the magical number is because there is none) and go on from there.
#7
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Theres a lot of hearsay on this topic within the Supra crowd. I think the concensus is that the leanest you can run the motor is around 15.5AFR. I run my car at 15AFR cruise and idle. Some people claim to run up to 17-18:1 AFR or so but they lose power and the engine misses and bucks at that range. The upside is that you save gas
The stock Lexus tune is pretty much spot on where it's supposed to be, 14.7:1 at idle and cruise. You can say it's rich becuase you can go a few ticks leaner to save fuel, but it's at stoich of 14.7 to reduce emissions(that's the rage where the cats are most efficient). The Lexus ecu goes a bit rich at full throttle dipping to the 11.5:1 range or so. Not necessary to be that rich, 12:1 shoud be fine and should gain you a bit of power.
When you're boosted fuel economy isn't exactly on the top of the list...not just a TT swap, I mean really boosted as in big aftermarket turbo, big injectors, engine management, etc. Even having the car tuned to save fuel, one high boost pull will negate almost all of the efficiency and fuel saving of that tank. The best way to save fuel is to just cruise and not gun it. I'll admit it's hard to do when you have all that power under the hood lol. That's why I get 10mpg
The stock Lexus tune is pretty much spot on where it's supposed to be, 14.7:1 at idle and cruise. You can say it's rich becuase you can go a few ticks leaner to save fuel, but it's at stoich of 14.7 to reduce emissions(that's the rage where the cats are most efficient). The Lexus ecu goes a bit rich at full throttle dipping to the 11.5:1 range or so. Not necessary to be that rich, 12:1 shoud be fine and should gain you a bit of power.
When you're boosted fuel economy isn't exactly on the top of the list...not just a TT swap, I mean really boosted as in big aftermarket turbo, big injectors, engine management, etc. Even having the car tuned to save fuel, one high boost pull will negate almost all of the efficiency and fuel saving of that tank. The best way to save fuel is to just cruise and not gun it. I'll admit it's hard to do when you have all that power under the hood lol. That's why I get 10mpg
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#12
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the only thing with this theory is that the ecu will adjust fuel trims to compensate for a rich or lean condition as monitored by your 02 sensor anytime you're in open loop, which is anytime you're driving except at start up and wot.
this is assuming you're only pulling back fuel at low and cruising rpms, i think we all know what would happen if you pull back fuel at wot.
so.... say you pull back 10% fuel. yes, it will lean out your mixture. however, after a few miles of driving, the 02 sensor will see it as lean, send that signal to the ecu, the ecu will then compensate by adjusting the fuel trims up, to get back to the proper fuel map as programmed into the ecu.
so you pull out 10%, the ecu puts back in 10%. you can pull back more and more and eventually the ecu runs into a limit as to how much fuel it can adjust via fuel trims. i think it's 25%. then guess what? you get a cel and code saying something like "bank 1 lean".
this is assuming you're only pulling back fuel at low and cruising rpms, i think we all know what would happen if you pull back fuel at wot.
so.... say you pull back 10% fuel. yes, it will lean out your mixture. however, after a few miles of driving, the 02 sensor will see it as lean, send that signal to the ecu, the ecu will then compensate by adjusting the fuel trims up, to get back to the proper fuel map as programmed into the ecu.
so you pull out 10%, the ecu puts back in 10%. you can pull back more and more and eventually the ecu runs into a limit as to how much fuel it can adjust via fuel trims. i think it's 25%. then guess what? you get a cel and code saying something like "bank 1 lean".
#13
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If you mix lets say 12 parts air to 1 part part fuel your air fuel mix is said to be 12:1. If you run 14.7 parts air to one part fuel you are at 14.7:1 which is the standard target most non boosted cars come from the factory adujsted too.
If you go above 14.7:1 you are said to have a leaner fuel mix than stoichmetric (SP), if you go below like 12;1 you are said to be running richer.
Now you have leaner and richer, but you also have too lean and too rich. Too lean and you will damage your engine, under WOT on a boosted car I would not want to ever get above 12.5:1 and I wouldnt want to get below 11:1 or so. Too much fuel in the cylinders will also harm the engine, it is called cylinder wash.
Hope that helps
Last edited by morris; 06-17-08 at 12:51 PM.
#14
Here is how you get 100MPG! Garage the GS and....
I tell you what, if gas hits $5.00 per gallon, I will be commuting on one of these bad boys... (I will make sure I have a dark tinted full mask helmet so nobody can recognize me)
I tell you what, if gas hits $5.00 per gallon, I will be commuting on one of these bad boys... (I will make sure I have a dark tinted full mask helmet so nobody can recognize me)
#15
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the only thing with this theory is that the ecu will adjust fuel trims to compensate for a rich or lean condition as monitored by your 02 sensor anytime you're in open loop, which is anytime you're driving except at start up and wot.
this is assuming you're only pulling back fuel at low and cruising rpms, i think we all know what would happen if you pull back fuel at wot.
so.... say you pull back 10% fuel. yes, it will lean out your mixture. however, after a few miles of driving, the 02 sensor will see it as lean, send that signal to the ecu, the ecu will then compensate by adjusting the fuel trims up, to get back to the proper fuel map as programmed into the ecu.
so you pull out 10%, the ecu puts back in 10%. you can pull back more and more and eventually the ecu runs into a limit as to how much fuel it can adjust via fuel trims. i think it's 25%. then guess what? you get a cel and code saying something like "bank 1 lean".
this is assuming you're only pulling back fuel at low and cruising rpms, i think we all know what would happen if you pull back fuel at wot.
so.... say you pull back 10% fuel. yes, it will lean out your mixture. however, after a few miles of driving, the 02 sensor will see it as lean, send that signal to the ecu, the ecu will then compensate by adjusting the fuel trims up, to get back to the proper fuel map as programmed into the ecu.
so you pull out 10%, the ecu puts back in 10%. you can pull back more and more and eventually the ecu runs into a limit as to how much fuel it can adjust via fuel trims. i think it's 25%. then guess what? you get a cel and code saying something like "bank 1 lean".
My friend is doing that on his IS300 and he's getting a notable fuel savings every tank.