AFR ratios, whats too lean.

[Mad Hatter]

I have been having some problems with my O2 sensors and several other codes as well. My question is how accurate is the AFR reading you get from the OBDII? I usually record my AFR on my torque videos and at WOT in fourth is goes down to a max low of 10.35 at 5800rpm. Most of the time the AFR is at 11 at WOT and higher rpm. My only engine mods are Kooks LTH and catted xpipe with front grill removed and KN air filter.

I thought that 10.35 would be the opposite of lean?? I will check the plugs tonight and see what state they are in and take some pics.

 

[Shaun@AED]

Below is a screen shot of one of the 5 Wide Open Throttle logs you sent me. All 5 logs showed the same issues.

In this shot you can see the measured air fuel traces for Bank 1 and Bank 2. Lambse commanded is .847, measured on Bank 1 is .879 and Bank 2 is .986. Both banks are lean, bank 2 (if it's reading correctly) is severe engine damaging lean. There is also knock activity in these logs.

 

[Mad Hatter]

Thanks Shaun, I am praying that I have a voltage problem and the readings are not correct!! Any suggestions as where I should start looking? Canceled my events for the next few months...

 

[Mad Hatter]

I guess in other words, relaying on the OBDII AFR ratios was not such a great indicator?

 

[Mad Hatter]

All eight plugs look like this, Too me they look Ok but I am no expert!

 

[steveespo]

Shaun why aren't his fuel trims indicating anything? I would expect that they would be trying to richer the mixture to get to the commanded value. Air leakage at the intake tube or the manifold? Or bad fuel pump?
Thanks for posting, your input is always welcome.
Steve.

 

[Mad Hatter]

Could the new error code P0451: Evaporative Emission Control system Pressure sensor Range/Performance

Have something to do with running lean? maybe the pump cannot get enough fuel from the tank with a vacuum? This error first appeared March 22, I noticed it was hard to fill the tank at the pump station.

 

[Shaun@AED]

Shaun why aren't his fuel trims indicating anything? I would expect that they would be trying to richer the mixture to get to the commanded value. Air leakage at the intake tube or the manifold? Or bad fuel pump?
Thanks for posting, your input is always welcome.
Steve.

When the ECU detects O2 faults it ignores O2 input at WOT.
A good reason to never race a vehicle when there are O2 fault codes.

 

[Mad Hatter]

When the ECU detects O2 faults it ignores O2 input at WOT.
A good reason to never race a vehicle when there are O2 fault codes.

Does that happen when the fault code is present and check engine light appears?? I always clear the codes before I go on the track or leave the track if they appear. Some times the O2 cel did not appear for days.

Here are the pics of all eight spark plugs, doing a compression test and the shop will be scanning the sensores etc.

 

[Shaun@AED]

Clearing the codes does not 'fix' the problem, and the ECU will still ignore the O2 data until it sees they are working properly via the test the ECU does to check the O2's and make sure they are functioning correctly.
IE, you were racing the the road course with NO O2 correction and running Lean with low fuel quality.

Iridium spark plugs in these engines normally do not come out dark brown like that. Without seeing the plugs with my own eyes looking for details very closely, I'd say those plugs look cold, likely from a lack of ignition timing, which is another indication of knock activity / low fuel quality as the ECU's in these cars can pull 15 degrees timing MAX when knock is detected.
This retarded ignition timing will not only limit the heat the spark plugs see, but will cause overheating of the exhaust as the air/fuel will not finish burning when the exhaust valve is opened up. (Headers will glow red hot).

 

[Mad Hatter]

Well, trying to look on the bright side....Once I fix my engine, I will have more power!! Car is in the Shop and hopefully its not too damaged.

My team mates are not having these problems apparently..... I talked to all the other prepped cars and only a few add some Sunoco 104 octane race gas to their tank for safety. It costs about 100 bucks for a 20L can here in Chile. So far out of the 20 odd high power cars in our class, none have the symptoms I have, A few bent valves and busted turbos etc., One Honda crx with 275HP did bust a block though. Includes three 800hp GTR's. In my class we have three ZL1's, Three Mustangs and one Camaro SS. All are using the same gas. The Camaro SS is running race cams etc and has about 570Hp. Recently had the engine apart after a bent valve. Everthing looked good inside. Makes me think I have a specific problem to my car.....

If In the future would a canned performance tune for 91 octane be a safer way to go for me?? I had left the tune stock because I thought it was the safer way to go.... :-\

 

[azazell64]

Is your CEL caused by your Kooks exhaust? Do you have the Green cats that are supposed to be able to run without a tune or are you running the ones that require a tune and are opting out of an aftermarket tune?

 

[Mad Hatter]

The cel started about 3 months after I installed the kooks regular catted exhaust.. I thought its was cat related but now worried it might be something else. I was looking for a aftermarket tune but that might have to wait till this gets sorted out. Shaun has been very helpful but would perfer not to tune a car down here due to fuel concerns and the state of my logs.

 

[azazell64]

The reason I ask this is the "Green cats" state that:
3" Stainless Steel Green Catted H Pipe
Includes Kooks 49 State EPA Legal Ultra High Performance Green Cats
2 3/4" Outlet For Use With OEM Exhaust
Outlet For Factory Sidepipes Or Kooks Sidepipes
No Check Engine Lights
Must Be Used With Kooks Long Tube Headers
as where the non "green cat" makes no mention about not causing a CEL which leads me to believe it requires a tune as per their writeup:
3" Stainless Steel Catted X Pipe
Includes Kooks High Flow Race Cats
2 3/4" Outlet For Use With Aftermarket Exhaust
Must Be Used With Kooks Long Tube Headers
These products are not legal for sale, installation, or use on licensed vehicle in the state of California. And they do NOT meet CARB compliance.

I know it's the difference between and H-pipe and an X as well in the above statement but I can't see that having an effect on the CEL. I'm sure Shaun will know the answer to this immediately. This is just my $.02 and I am also waiting to hear what Shaun has to say.

 

[Shaun@AED]

Probably the safest tune you could be running with your setup like this would be the stock tune as it has a few key features that have likely saved your engine from blowing itself apart on the race track:
1. Aggressive fueling enrichment based on exhaust temperature. Even though you are running lean compared to commanded lambda, the commanded lambda in the stock tune gets VERY rich when exhaust temps increase (.68 lambda is not uncommon). This is why on the road course you were reading air fuels in the mid/low 10's.
2. Active and appropriately sensitive knock sensors that can pull up to 15 degrees.

If you were running the Track key tune, the engine would likely have not survived as Ford Racing commands a much leaner mixture at WOT and de-sensitizes the knock sensors to the point they do very little.

Unfortunately with the stock tune you are WAY down on power, especially when the ECU richens the mixture so much and pulls a bunch of timing a few laps in on race day.

In order to have a 'proper' full performance Road Course tune, you will need to run higher octane fuel. Adding Octane boost or going with a 50/50 mix is not a good idea IMO. Full race gas when on the race track and you can have a properly fast car with a tune to match.

Otherwise, stick to the stock tune and hope for the best. Its already saved this engine IMO.

And never race this car with any CEL light.

 

[Mad Hatter]

Ok! busily trying to get a good deal on some race gas. Thanks for being so patient Shaun, this has been very educational for me!

 

[F.D. Sako]

Off topic and possible an ignorant question for Shaun.

I've been adding a bottle of Lucas octane booster when at the road coarse for extra assurance, since I run the track key. In your opinion is it better for me to mix a few gallons of 100 octane with the 93, or stick with the octane booster?
Is 100 octane considered race fuel, or do race fuels have other additives in addition to the higher octanes?

 

[Shaun@AED]

Ok! busily trying to get a good deal on some race gas. Thanks for being so patient Shaun, this has been very educational for me!

Do you have access to E85 or E98?
E85 would be an ideal fuel for the Road course, and if can't get E85 but can order 54gal barrels of E98 you can mix your own to 15% gasoline and 85% Ethanol.

 

[Shaun@AED]

Off topic and possible an ignorant question for Shaun.

I've been adding a bottle of Lucas octane booster when at the road coarse for extra assurance, since I run the track key. In your opinion is it better for me to mix a few gallons of 100 octane with the 93, or stick with the octane booster?
Is 100 octane considered race fuel, or do race fuels have other additives in addition to the higher octanes?

Octane boost is not a replacement for Race Gas. Octane boost does not actually raise the octane of the fuel, it raises the RVP (vaporizing point) of the fuel to make it less prone to detonation with higher temperatures / cylinder pressures.

IMO the Track Key tune should be run with Straight 100 octane unleaded for safety. That tune is very aggressive and the knock sensors to very little if anything. There are more than a few Boss's who have damaged their engines on the road course with the track key tune.

At AED we recommend all our customers run Real Race Gas when on the road course. It's what we call 'cheap insurance'.

 

[ArizonaBOSS]

Octane boost is not a replacement for Race Gas. Octane boost does not actually raise the octane of the fuel, it raises the RVP (vaporizing point) of the fuel to make it less prone to detonation with higher temperatures / cylinder pressures.

IMO the Track Key tune should be run with Straight 100 octane unleaded for safety. That tune is very aggressive and the knock sensors to very little if anything. There are more than a few Boss's who have damaged their engines on the road course with the track key tune.

At AED we recommend all our customers run Real Race Gas when on the road course. It's what we call 'cheap insurance'.

+1

It's a lot cheaper than a new engine in the long run...ask me how I know.