air fuel gauge reading?

[zerq]

i bought my dsm recently with a bad o2 sensor to the already installed Innovate A/F gauge, it just flashed "7.4". i replaced the sensor and was told it should idle at 14.7 and full boost should show 10/11. Well I idle at 10/14 and at half boost (5/6psi) its already flashing 7.4 and doesnt show anything lower. My mod list is up to date and im just assuming my cars ratio is just off. Im a newbie looking for knowledge, more fuel? more air? Normal with my mods? The boost gauge and the o2 sensor are all I've done to it personally, besides the sound system.. Could that be taking too much power from the fuel pump (subwoofer)? i havent done the pump rewire yet, though i plan to soon.

 

[nightstocker99]

Check the signal source wire to Innovate A/F gauge. They it might not be hooked up, or just installed wrong. I am not sure if you have yet.

Here is some base knowledge about a/f ratio.

Stoichiometric mixture of 14.7:1 is considered perfect.

Any mixture less than 14.7 to 1 is considered to be a rich mixture; any more than 14.7 to 1 is a lean mixture – given perfect (ideal) "test" fuel

7.4:1 is extremely rich. too much fuel.

12:1 mixture is the perfect ratio for max power before a rich misfire occurs

I would say check your maf sensor it could be going out depending on how old it is. You cant really add more air, all the air must pass the maf sensor or it is considered an air leak...which would result in a lean mixture, not your case here. Unless your Maf sensor is bad. If you have a DMM (digital mutlimeter) check the voltage readings. I am not sure what the 1gs reading are but the Signal wire should be around 0.5 volts at idle and 4.5 volts at WOT. The source voltage should be a constant 12 volts, and the ground side of the maf should have .5 volts if grounded correctly.

Your new exhaust could be the problem if you didnt install the gaskest or torque the bolts down correctly. The O2 sensor read the a/f ratio coming out of the engine. if any air escapes the exhaust the pcm will think something is wrong because the mixture is diluted and will add more fuel. it only knows that so much fuel was injected with this much air and it should get the same amount out of the engine and out passed the O2. or just make sure the o2 sensor is screwed in the exhaust the whole way.

Check you Spark Plugs thats easy to do and they could simply be old and not strong enough to create a complete burn.

Three easy things to check. if you dont have a dmm then atleast check the spark plugs and check out the O2 sensor to see if it is loose.

if you dont have an O2 sensor then we can move on to other component.

 

[WES_393]

10.9-11.1 is the ideal A/F ratio for pump gas. 12:1 is much too lean. But it seems to me your maxing out your gauge (pegging at 7.4) so it's possible you are running even richer than you think. Make sure all couplers/hoses are clamped down good and free of leaks. Also check your injectors to see if they appear stock or possibly aftermarket.

 

[LiquidX]

First thing I would do is adjust the sweep range do its more accurate. Your usable range is 9.0:1-20:1.

Also,reading the guide will help you out.

If you feel it's the sensor, test it by having it in open air with it on. It should show max lean. Put brake cleaner on a rag and wrap the sensor. It should go max rich.

Leaving it there it should not throw a code. Pull it off and it should go to max lean again.

 

[nightstocker99]

this is from a book called

How to tune and modify - engine management systems by Jeff Hartman

In Chapter 1: Understanding Fuel Delivery, pg 21

air/fuel mixture and characteristics

afr - 6:1 rich burn limit (fully warm engine)
afr - 9:1 black smoke/low power
afr - 11.5:1 approximate rich best torque at WOT
afr - 12.2:1 safe best power at WOT
afr - 13.3:1 approximate lean best torque
afr - 14.7:1 stoichiometric (chemically ideal)
afr - 15.5:1 lean cruise
afr - 16.5:1 usual best economy
afr - 18.0:1 carbureted lean burn limit
afr - 22+:1 eec/efi lean burn limit

That is a creditably reference.

Depending on what your cars tune setup is well determine what your AFR should be.

 

[zerq]

I'll check for leaks, and check the injectors, though i doubt they're aftermarket, previous owner has a set of 560cc that he was gonna put on his second engine to build then install so he left this engine fairly stock.

also something i forgot to mention, though im not sure it matters, the gauge is hooked to an o2 sensor that was moved to the down pipe area under the engine near the firewall. he had to do this due to the housing not having enough clearance with the aluminum radiator and fan. do you think his bung could be bad? the housing bung was capped and doesnt look dirty so i dont think thats leaking.

i was hoping to build myself a MBC. looks like I've got other things to focus on haha

 

[nightstocker99]

As long as the O2 sensor you are getting your signal from isnt after the cat it shouldnt matter where it is placed in the downpipe. Make sure that the power and ground wires are not spliced into wires that require a certain voltage. Before checking anything else I would personally make sure that the O2 gauge is installed correctly with a good power and ground and that the signal wire in getting its signal reference from the correct source.

You problem is not going to be between the maf and throttle body. If it was the pcm would calculate for the correction.

I'll check for leaks, and check the injectors, though i doubt they're aftermarket, previous owner has a set of 560cc that he was gonna put on his second engine to build then install so he left this engine fairly stock.

also something i forgot to mention, though im not sure it matters, the gauge is hooked to an o2 sensor that was moved to the down pipe area under the engine near the firewall. he had to do this due to the housing not having enough clearance with the aluminum radiator and fan. do you think his bung could be bad? the housing bung was capped and doesnt look dirty so i dont think thats leaking.

i was hoping to build myself a MBC. looks like I've got other things to focus on haha

here is what I have read.

ecu/pcm adjustments are set too high (bad tune)
tps calibrated incorrectly
leaky injectors
excessive fuel pressure (with no tune to adjust for higher flow rate)
nonfunctional temperature sensor
bad ecu/pcm

How to tune and modify - engine management systems by Jeff Hartman

In Chapter 14: EMS Troubleshooting , pg 167

 

[zerq]

ok. I'll check the wires. I will also see about having it tuned. It seems to drive fine so i wasn't sure if it was bad numbers or a bad tune.

 

[nightstocker99]

Check the wires before you get a tune. Always look at the things that a free to do first before spending any money. If the car feels like it drives fine and doesnt misfire then that could leave it to just one thing the a/f gauge.

ok. I'll check the wires. I will also see about having it tuned. It seems to drive fine so i wasn't sure if it was bad numbers or a bad tune.

 

[zerq]

Check the wires before you get a tune. Always look at the things that a free to do first before spending any money. If the car feels like it drives fine and doesnt misfire then that could leave it to just one thing the a/f gauge.

right, quick tell tale, how many miles should i see out of a tank of 91? i got about 220 with spirited driving 91oct w/10%E and 240 with Ethynol Free 91. does that sound normal?

 

[WES_393]

12:1 on 91 octane with no way to see knock, control timing, or even log the A/F ratio is just a bad idea. I never said it can't be done, but it's not the best idea. I would advise staying close to 11.1:1 for now. And I'm speaking from personal experience, not a book.

 

[zerq]

I'm not seeing anything wrong with my wires or intake... Couldn't i just raise the boost to say, 15psi and even it out?
I'm not really understanding what im supposed to do with the ratios you guys are putting out. I don't have a logger or DSMlink or anything like that. Lets pretend im a probationary member that just bought his first DSM haha GOO GOO GAGA

 

[jed344]

i tune for 11.1 at wot and usually tapper it to 10.8 or so by redline just little richer.