Wideband O2 with Stock ECU <- will it work?
07-08-13, 10:46 PM
#1
Rotary Newb
Thread Starter
Wideband O2 with Stock ECU <- will it work?
My O2 sensor tests bad. Under acceleration and deceleration it reads 0 volts. When it gets back to idle it read .5v and slowly drops to .2v. I bought a $15 sensor that I have to cut the connector off the old sensor and crimp onto the new one.
Now I'm thinking that I should have bought a wideband O2 sensor, but my question is will it work with the stock ECU? If so is it worth doing?
Getting 16.7MPG highway and about 10MPG in the city.
Now I'm thinking that I should have bought a wideband O2 sensor, but my question is will it work with the stock ECU? If so is it worth doing?
Getting 16.7MPG highway and about 10MPG in the city.
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Spider2k (12-25-22)
07-08-13, 11:45 PM
#3
Wideband o2 sensors require a controller to function. Some of those controllers have a narrowband output that allow you to give the ecu the signal it needs. Last I checked these controller/sensor combos were going for 2-300usd.
The o2 sensor's function in the fc is optimizing mixtures during closed loop operation (low load constant speed). If your fuel economy is that poor than you need to stop hot-rodding your car all over town or you have a different problem.
The o2 sensor's function in the fc is optimizing mixtures during closed loop operation (low load constant speed). If your fuel economy is that poor than you need to stop hot-rodding your car all over town or you have a different problem.
07-09-13, 12:26 AM
#4
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You did the right thing. Even if you got a wideband O2 sensor that could emulate a narrowband output, your car would not run any better.
To test your gas mileage, do so on a freeway trip, and try to keep the car as close to 55mph as possible, as this was the original highway design speed of the car. The problem with city driving is that the acceleration eats into the gas mileage depending on how aggressively you drive the car. Also, as mentioned earlier, the O2 sensor only adjusts the air-fuel mixture during cruise.
Common things that can reduce gas mileage:
- More weight
- Driving on an incline
- Headwind
- Hot, humid weather
- High altitude
- Rough road surface
- Improper tire pressure
- Tires with a smaller diameter or more grip (or width) than original
- Taking short trips in which the engine does not have much time to warm up
- Rapid acceleration, or driving in a lower gear
- Car often sits at idle (stuck in traffic, drive-through windows, letting the engine warm up, etc.)
- Driving at high speed (drag increases exponentially at the square of speed)
- Drag caused by a spoiler, or a dirty/unwaxed exterior surface
- Ethanol-enriched fuel
- Engine worn or has deposits
- Thick engine oil (for example, using 20W-50 in the winter)
- Catalytic converter or mufflers clogged
- Installing a custom "cold air" intake that is sucking in hot air from the radiator
To test your gas mileage, do so on a freeway trip, and try to keep the car as close to 55mph as possible, as this was the original highway design speed of the car. The problem with city driving is that the acceleration eats into the gas mileage depending on how aggressively you drive the car. Also, as mentioned earlier, the O2 sensor only adjusts the air-fuel mixture during cruise.
Common things that can reduce gas mileage:
- More weight
- Driving on an incline
- Headwind
- Hot, humid weather
- High altitude
- Rough road surface
- Improper tire pressure
- Tires with a smaller diameter or more grip (or width) than original
- Taking short trips in which the engine does not have much time to warm up
- Rapid acceleration, or driving in a lower gear
- Car often sits at idle (stuck in traffic, drive-through windows, letting the engine warm up, etc.)
- Driving at high speed (drag increases exponentially at the square of speed)
- Drag caused by a spoiler, or a dirty/unwaxed exterior surface
- Ethanol-enriched fuel
- Engine worn or has deposits
- Thick engine oil (for example, using 20W-50 in the winter)
- Catalytic converter or mufflers clogged
- Installing a custom "cold air" intake that is sucking in hot air from the radiator
07-09-13, 12:00 PM
#5
Rotary Newb
Thread Starter
Wow thanks for all the great feedback!
What is ideal cruising RPM for best mileage?
Originally my exhaust smelled very rich at idle. After adjusting TPS is got better. After installing cats the smell changed to funky cat smell.
I read in a post around here someone recommend to get a wideband because they're down to $80 now. Is that true without a controller?
Eventually I'm going to get a Megasquirt or Adaptronic ECU so a wideband is in my future. Read on here someone was getting 25MPG with Megasquirt.
My 10MPG city estimate is based on my first tank of gas (91 octane) where my trip counter got stuck and I had to reset it. I was driving like a mad man around town getting a feel for the car. My last tank of gas (16.7mpg using about 9 gallons of 85 octane) was 30% city miles shifting between 3000-3500 RPM and moderate acceleration. The 70% highway miles was 70-75MPH and RPMs around 3000.
- More weight
(AC has been removed, no cargo)
- Driving on an incline
(All flat roads)
- Headwind
(No high winds)
- Hot, humid weather
(Hot, but no humid)
- High altitude
(SLC is around 4500feet)
- Rough road surface
(Nice smooth roads)
- Improper tire pressure
(New tires properly inflated)
- Tires with a smaller diameter or more grip (or width) than original
(tiny bit larger diameter 205/55/16)
- Taking short trips in which the engine does not have much time to warm up
(handful of trips to the coffee shop, 2 miles)
- Rapid acceleration, or driving in a lower gear
(no rapid acceleration on last tank of gas, tried keeping RPMs at 3000 on highway and less in the city)
- Car often sits at idle
(no letting engine warm up, mild driving until warm, ignition off waiting at coffee shop drive-up)
- Driving at high speed
(70-80 MPH highway, 3000-3200 RPM)
- Drag caused by a spoiler, or a dirty/unwaxed exterior surface
(no spoiler, clean car, but not waxed)
- Ethanol-enriched fuel
(First tank 91 octane, read low octane is better in rotary. Last tank was 85 octane. Does CostCo sell ethanol enriched fuel?)
- Engine worn or has deposits
(Engine was rebuilt and broken in 2000 miles under 3000 RPM)
- Thick engine oil (for example, using 20W-50 in the winter)
(No idea what previous owner used. He did say not to use synthetic based on oil being burned by engine. What is ideal oil for Summer 10w30?)
- Catalytic converter or mufflers clogged
(New CatCo cats, previous cats were hollowed out. Mufflers and Y pipe are custom and not super quiet. No idea if they're clogged, but car drives fast and isn't obgged down.)
- Installing a custom "cold air" intake that is sucking in hot air from the radiator
(Stock air box with K&N filter)
What is ideal cruising RPM for best mileage?
Originally my exhaust smelled very rich at idle. After adjusting TPS is got better. After installing cats the smell changed to funky cat smell.
I read in a post around here someone recommend to get a wideband because they're down to $80 now. Is that true without a controller?
Eventually I'm going to get a Megasquirt or Adaptronic ECU so a wideband is in my future. Read on here someone was getting 25MPG with Megasquirt.
My 10MPG city estimate is based on my first tank of gas (91 octane) where my trip counter got stuck and I had to reset it. I was driving like a mad man around town getting a feel for the car. My last tank of gas (16.7mpg using about 9 gallons of 85 octane) was 30% city miles shifting between 3000-3500 RPM and moderate acceleration. The 70% highway miles was 70-75MPH and RPMs around 3000.
- More weight
(AC has been removed, no cargo)
- Driving on an incline
(All flat roads)
- Headwind
(No high winds)
- Hot, humid weather
(Hot, but no humid)
- High altitude
(SLC is around 4500feet)
- Rough road surface
(Nice smooth roads)
- Improper tire pressure
(New tires properly inflated)
- Tires with a smaller diameter or more grip (or width) than original
(tiny bit larger diameter 205/55/16)
- Taking short trips in which the engine does not have much time to warm up
(handful of trips to the coffee shop, 2 miles)
- Rapid acceleration, or driving in a lower gear
(no rapid acceleration on last tank of gas, tried keeping RPMs at 3000 on highway and less in the city)
- Car often sits at idle
(no letting engine warm up, mild driving until warm, ignition off waiting at coffee shop drive-up)
- Driving at high speed
(70-80 MPH highway, 3000-3200 RPM)
- Drag caused by a spoiler, or a dirty/unwaxed exterior surface
(no spoiler, clean car, but not waxed)
- Ethanol-enriched fuel
(First tank 91 octane, read low octane is better in rotary. Last tank was 85 octane. Does CostCo sell ethanol enriched fuel?)
- Engine worn or has deposits
(Engine was rebuilt and broken in 2000 miles under 3000 RPM)
- Thick engine oil (for example, using 20W-50 in the winter)
(No idea what previous owner used. He did say not to use synthetic based on oil being burned by engine. What is ideal oil for Summer 10w30?)
- Catalytic converter or mufflers clogged
(New CatCo cats, previous cats were hollowed out. Mufflers and Y pipe are custom and not super quiet. No idea if they're clogged, but car drives fast and isn't obgged down.)
- Installing a custom "cold air" intake that is sucking in hot air from the radiator
(Stock air box with K&N filter)
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07-09-13, 07:47 PM
#8
Rotary Newb
Thread Starter
Today had a mechanic install my new $14 Boche O2 sensor and a new fuel filter. The air filter is clean and there are new spark plugs and wires. Still failed emissions even with new cats.
I've got a running thread in the newbie forum trying to figure out why my emissions are failing. It's injecting too much fuel. The petrol smell has been replaced with catalyst smell and the metal on the cats has turned orange. The pipe going to the first cat is turning blue and purple like those titanium tipped mufflers look.
Failed emissions- '90 FC3S NA
Would it be possible for a moderator to move that thread to this forum so I can get more attention with it? Don't want to go off topic in this thread.
I've got a running thread in the newbie forum trying to figure out why my emissions are failing. It's injecting too much fuel. The petrol smell has been replaced with catalyst smell and the metal on the cats has turned orange. The pipe going to the first cat is turning blue and purple like those titanium tipped mufflers look.
Failed emissions- '90 FC3S NA
Would it be possible for a moderator to move that thread to this forum so I can get more attention with it? Don't want to go off topic in this thread.
Last edited by orion411; 07-09-13 at 07:50 PM.
07-09-13, 07:54 PM
#9
Rotary Newb
Thread Starter
By the way. The mechanic said the new O2 sensor is giving out same bad readings as old sensor. I'll double check that when I get home to my voltage meter.
Back on topic. Wideband isn't going to improve anything without an ECU replacement, right?
I'd drop cash on a Megasquirt or Adaptronic and a Wideband O2 sensor if it's going to get me 5MPG better mileage. It will eventually pay for itself. Plus I've got project to convert this car to multi-fuel, which will require new ECU.
Back on topic. Wideband isn't going to improve anything without an ECU replacement, right?
I'd drop cash on a Megasquirt or Adaptronic and a Wideband O2 sensor if it's going to get me 5MPG better mileage. It will eventually pay for itself. Plus I've got project to convert this car to multi-fuel, which will require new ECU.
07-10-13, 08:27 PM
#12
A standalone like the Adaptronic will definitely get you better gas mileage than stock as you can lean the engine out. However you have another major issue somewhere. Did you replace your fuel pump recently? Maybe you have a fuel leak somewhere, like on your sender unit. I would also confirm all off your coils are working, and your cas is set correctly. Furthermore I would get your fuel injectors cleaned. If all those check out, it's possible you have a sensor stuck in a cold range, making the ecu run very rich. If you still want an ecu we are currently running a special if you buy a select range model you get a free lc-1 wideband...
07-10-13, 09:41 PM
#13
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The three above posts cover all of the trouble-shooting items that I would have mentioned.
That is a little complicated because it depends on the power required and power available, and I am not aware of any specific statistics on this. Generally, driving at 55mph in 5th gear should yield a good fuel economy, and the economy will get worse as the speed increases. Other than this, I am not sure what speed/rpm/gear combinations yield the best gas mileage.
Just make sure that you do accelerate past 3,800rpm on a regular basis so that the secondary fuel injectors do not get clogged.
Your car is rated for 87 octane. The 85 is probably OK for your high altitude, but be sure to switch to 87 if driving down to lower altitude areas. Gasoline blends are determined by the local area regulations, so you will need to check with Costco to see what kind of blend they are using. Also, your local area probably specifies a different blend in Summer than in Winter.
The ideal oil is determined by the temperature range in your local area. You can look this up in the Owner's Manual, Factory Service Manual (links in the FAQ), and there is also a list on a sticker under the hood but it is not very clear.
Typically, the best tuning for gas mileage on a 2Gen RX-7 is accomplished by an experienced tuner setting up an aftermarket ECU in "open loop" mode, which means the ECU does NOT use the O2 sensor to actively tune the engine. He may use an O2 sensor to initially set up the ECU tuning, but after that the O2 sensor is not necessary. Therefore, the car owner does not usually need to buy a wideband AFR meter because the tuner will tend to use his own equipment, which may even be an EGT meter and/or 5-gas analyzer rather than a wideband O2 meter.
A good tuner can typically get 25-30mpg highway from a standalone EMS tuned open-loop. However, as mentioned previously, it sounds like there is something wrong with your car that needs to be fixed first. I'm not sure what kind of fuel you plan to use, but just keep in mind that ethanol sucks. Unfortunately, you will not find a lot of hydrogen or LPG experience on this forum.
That is a little complicated because it depends on the power required and power available, and I am not aware of any specific statistics on this. Generally, driving at 55mph in 5th gear should yield a good fuel economy, and the economy will get worse as the speed increases. Other than this, I am not sure what speed/rpm/gear combinations yield the best gas mileage.
Just make sure that you do accelerate past 3,800rpm on a regular basis so that the secondary fuel injectors do not get clogged.
The ideal oil is determined by the temperature range in your local area. You can look this up in the Owner's Manual, Factory Service Manual (links in the FAQ), and there is also a list on a sticker under the hood but it is not very clear.
A good tuner can typically get 25-30mpg highway from a standalone EMS tuned open-loop. However, as mentioned previously, it sounds like there is something wrong with your car that needs to be fixed first. I'm not sure what kind of fuel you plan to use, but just keep in mind that ethanol sucks. Unfortunately, you will not find a lot of hydrogen or LPG experience on this forum.
08-14-13, 01:40 PM
#14
Rotary Newb
Thread Starter
orion411
Took my car to the dealer for diagnostic. They did compression test, which is ok.
Dealer says I need a new Air Control Valve, which is out of stock.
part # N350-13-990A
Any ideas where I can find a used one?
Or should I pay $357 for a new one from MazdaPartsUnlimited?
My compression is:
Bank One: 90 psi, 83 psi, 92 psi
Bank Two: 83 psi, 87 psi, 87 psi
Dealer says I need a new Air Control Valve, which is out of stock.
part # N350-13-990A
Any ideas where I can find a used one?
Or should I pay $357 for a new one from MazdaPartsUnlimited?
My compression is:
Bank One: 90 psi, 83 psi, 92 psi
Bank Two: 83 psi, 87 psi, 87 psi
12-25-22, 02:21 PM
#16
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A standalone like the Adaptronic will definitely get you better gas mileage than stock as you can lean the engine out. However you have another major issue somewhere. Did you replace your fuel pump recently? Maybe you have a fuel leak somewhere, like on your sender unit. I would also confirm all off your coils are working, and your cas is set correctly. Furthermore I would get your fuel injectors cleaned. If all those check out, it's possible you have a sensor stuck in a cold range, making the ecu run very rich. If you still want an ecu we are currently running a special if you buy a select range model you get a free lc-1 wideband...
