phu626

iTrader: (1)

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!

morris

iTrader: (2)

Yea but does it work on the V8, 9mpg on premium sucks big time!

aristo2369

iTrader: (2)

I have an Apex fuel mix controller, prior owner said that i can run a -10% mix if racing but said that runing at -5% mix is ok for street driving.? is that correct?

GSteg

iTrader: (15)

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.

morris

iTrader: (2)

What do you mean by -10 or -5? AF ration is normally given as 12:1 or 14:1.

10:1 is rich and 16:1 is lean

Gennady7

iTrader: (4)

I bought the Apexi Neo and am thinking of doing this as well. Please let me know if anyone has done this with a stock 2jz-ge engine.

JeffTsai

iTrader: (1)

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

kit cat

iTrader: (6)

i just turn on the snow mode and keep my revs under 2000.
it sucks not being able to unleash my V8, but oh well...not that I need all 300hp all the time anyways.

morris

iTrader: (2)

Last week I was did a lot of heavy boosting, spent time dialing in the tune. I went from 13mpg to 9 mpg. We are only talkiing 7psi on the 1uz here.

JeffTsai

iTrader: (1)

Don't worry you're still getting better than me. I got 7mpg one time under (25psi)heavy boosting lol. But I run ethanol, so it is consumes a bit faster than gasoline.

phu626

iTrader: (1)

Jeff.... what's the difference btw. lean and rich if you don't mind me asking? Which one is the one that cuases our 2gs motor to go bang bang

19psi

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".

morris

iTrader: (2)

Combustion works by mixing fuel and air in a cylinder, compressing it and then applying a spark.

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

99GS4

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)

JeffTsai

iTrader: (1)

The easy way is to get a Zeitronix wideband unit. It has a function built in called narrowband switching point. Basically, it will feed your stock ecu a slightly skewed O2 signal which will allow you to still use the stock ecu and run richer or leaner. What it does is tell the ecu is 14.7 when in reality the engine is running at 15.5 or so. This will allow you to save fuel during idle and cruise. Under full throttle, the engine reads off the MAF sensor and internal fuel map without referencing the O2 sensor. That is called open loop operation. So in theory using the Zeitronix wideband you can run a tick leaner at idle/cruise and still retain proper fuel at full throttle.

My friend is doing that on his IS300 and he's getting a notable fuel savings every tank.