install headers without tune

[L8APEX]

I have an appointment to install my long tube ARH headers (without cats) tomorrow. Can I drive it without a tune? I have a tune for the car but the box the tuner was shipped in got lost my UPS and I should have a replacement coming by next week monday. The shop that is installing it is only 7 miles from my house

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[L8APEX]

Just to clarify, once I have the headers installed...I will drive home 7 miles and park the car until the tune arrives

 

[Ebm]

Just to clarify, once I have the headers installed...I will drive home 7 miles and park the car until the tune arrives

Nothing is ever guaranteed but death and taxes, but you should be fine. The computer will read the small change in AF made by the improvements in air flow and adjust your fuel trims accordingly to get the proper AFR driving normally(cruising). That's what it was designed to do. The tune will change WOT parameters , so you may run rich until then. Just avoid WOT and you will be fine.

 

[EFI]

The computer will read the small change in AF made by the improvements in air flow and adjust your fuel trims accordingly to get the proper AFR driving normally(cruising). That's what it was designed to do. The tune will change WOT parameters , so you may run rich until then. Just avoid WOT and you will be fine.

But if the computer can make adjustments to part throttle fueling, why can't it make the same at WOT (eg. you're saying it will run rich)?

The O2 sensors are widebands, and the tune is based on lambda. Thus regardless of what is going on in the engine, the computer will always target a certain lambda at WOT. If it seems more airflow from the headers and thus a leaner condition, it will add fuel to achieve the same lambda as before so it should not run rich or lean or whatever unless the change is so significant that the computer can't keep up or shove enough fuel.

 

[Ebm]

But if the computer can make adjustments to part throttle fueling, why can't it make the same at WOT (eg. you're saying it will run rich)?

The O2 sensors are widebands, and the tune is based on lambda. Thus regardless of what is going on in the engine, the computer will always target a certain lambda at WOT. If it seems more airflow from the headers and thus a leaner condition, it will add fuel to achieve the same lambda as before so it should not run rich or lean or whatever unless the change is so significant that the computer can't keep up or shove enough fuel.

You could have just said he will be fine running headers without a tune lol

 

[Nonsequitur]

But if the computer can make adjustments to part throttle fueling, why can't it make the same at WOT (eg. you're saying it will run rich)?

The O2 sensors are widebands, and the tune is based on lambda. Thus regardless of what is going on in the engine, the computer will always target a certain lambda at WOT. If it seems more airflow from the headers and thus a leaner condition, it will add fuel to achieve the same lambda as before so it should not run rich or lean or whatever unless the change is so significant that the computer can't keep up or shove enough fuel.

Short answer: The wideband O2 sensors are in a different position than stock. This will affect your AFR. The tune will make the necessary corrections so your ECU can make the proper adjustments to the AFR.

 

[thelostotter]

Short answer: The wideband O2 sensors are in a different position than stock. This will affect your AFR. The tune will make the necessary corrections so your ECU can make the proper adjustments to the AFR.

Is it harmful to run without a tune, or just not optimal? I guess my question is does the different location of the O2 sensors cause the ECU to adjust to an overly lean or rich AFR? I've been considering catted headers but I already have the Ford Performance PP2 tune and am not really thrilled about throwing that money away for another tune.

 

[Nonsequitur]

Is it harmful to run without a tune, or just not optimal? I guess my question is does the different location of the O2 sensors cause the ECU to adjust to an overly lean or rich AFR? I've been considering catted headers but I already have the Ford Performance PP2 tune and am not really thrilled about throwing that money away for another tune.

It's not really a question of lean or rich... well, actually both. Being that the widebands are further downstream on LTHs, there will be an increased delay in AFR measurement. If the ECU is not informed of this increased delay, it will essentially be trying to chase a moving AFR target. I'm not familiar with the Ford Performance PP2 tune but I would recommend getting a nice custom tune from a reputable tuner.

 

[L8APEX]

So I had the headers installed, car drives great and its much meaner. No CEL or anything the first day of driving it. I put maybe 30 miles on the car. Today I drove it and got a CEL, the car drives perfectly though and the temps all seem fine. I went into engineering mode and no codes were given. I am guessing I am having the CEL because I no longer have cats?

 

[ENPhoto]

If you have a way of checking the code that was given, then posting it up would be best to have someone help assist.

These cars have multiple tables in HP Tuners regarding the wideband 02's and no cats. I would advise a tune, mainly to turn off the cat protection tables and adjust for the new flow rate of exhaust gasses, but I'm sure that some people run without a tune. I'm don't see how HPT's Transport Delay table being in stock form would throw a code. The calibration should be able to correct the delay, with the sensor being further downstream. With the Cat Overtemp Protection (dumping more fuel to cool it), I'm really not sure.

No exhaust leaks upstream from the rear o2 sensor? That would be my first check, after finding what the code is.

I'm not sure where you are...but maybe find an autozone or parts store that offers Engine light checks? Or a buddy that has HPT or SCT and can quick scan for you?

 

[L8APEX]

The code is p0420

 

[Performance nut]

Thousands of miles (think around 14,000) on my 2016 Mustang with Kooks 1 7/8 headers and green cats without a tune. All the changes were positive: lower engine bay temps, bump in performance, and more aggressive sound. My fuel efficiency went down but I think that had more with me getting too happy with the go pedal. I took dozens of logs... idle, in traffic, at speed, fast acceleration... everything looked good.

Some folks did warn about racing it without a tune though which may be valid. I never did race it so I can't say yes or no there. For normal and spirited driving, I never had an issue.

 

[Nonsequitur]

The code is p0420

No cat and without a tune will get you that code. You'll need to pull the rear O2 sensor out of the exhaust stream by welding on an extension. An exhaust shop should be able to do that for you. As always YMMV. I still strongly recommend you get a tune not only for the peace of mind but also to get the most out of your LTH.

 

[L8APEX]

No cat and without a tune will get you that code. You'll need to pull the rear O2 sensor out of the exhaust stream by welding on an extension. An exhaust shop should be able to do that for you. As always YMMV. I still strongly recommend you get a tune not only for the peace of mind but also to get the most out of your LTH.

I am waiting for my tune to arrive in the mail! Thanks everyone for their help.

For the record, I took my car to the road course....no issues.

 

[paulm1]

Didnt want to start a new thread. Has anyone done catted headers without a tune? If so what do you think the HP gain was? Wondering if its possible to get to 500 crank hp and keep the warranty.

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