Odd hesitation

[HunterStang]

So i changed my exhaust and got rid of my cats and resonator. Its 2.5 inch piping. The axle back is still 2.25. In order to prevent the cel from the 02 sensor i used spark plug non foulers to basically raise the 02 sensors. I do not have a cel. Now when i drive the car everything is fine at all time except for when im wot. Specifically at 2900 rpm as im wot in any gear, the car hesitates almost as if the fuel is cut off for about .5 of a second. After that slight hesitation it continues accelerating normally. AFR is completely fine while that hesitation happens. If anyone might know what my issue is, please let me know.

Thank you.

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[GT Pony]

How are you measuring the A/F ratio? If it's with the virtual dash gauge, it may not be fast enough to see a short glitch like that.

 

[HunterStang]

How are you measuring the A/F ratio? If it's with the virtual dash gauge, it may not be fast enough to see a short glitch like that.

Yes it is with the virtual one. Why would have my AFR changed from doing exhaust. Im thinking its a tuning issue due to the fact that its a less restrictive exhaust and is bigger piping. So that means the engine can let air out faster and easier which means it could take in more. But i dont know how to really check for that. Any ideas what else it could be?

 

[astolt12]

Catless systems are a mess for the negligible gain you get from it. Your car has two sensors that measure their efficiency and the one mounted closest to your engine being the one that determine your A/F for the respective bank (left/right).

The digital gauge, although nice is a combined air fuel and is more of a novelty item than a real tool.

try and get some data logging done when you got WOT and see if your A/F on one side or both is dipping low. The last thing you want to do is find out you're lean on one bank and toast half your motor.

I ran 2.5" full exhaust and had no issues when i dropped a gear, a sensor is most likely stopping you.

 

[HunterStang]

Catless systems are a mess for the negligible gain you get from it. Your car has two sensors that measure their efficiency and the one mounted closest to your engine being the one that determine your A/F for the respective bank (left/right).

The digital gauge, although nice is a combined air fuel and is more of a novelty item than a real tool.

try and get some data logging done when you got WOT and see if your A/F on one side or both is dipping low. The last thing you want to do is find out you're lean on one bank and toast half your motor.

I ran 2.5" full exhaust and had no issues when i dropped a gear, a sensor is most likely stopping you.

Thank you for the reply. But the odd thing is that my sensor aren't actually getting any of exhaust through them since I raised then away from the pipe not to trigger cel from no cats. I might have to do some data logging. I'll try that out. It's strange since It happens at specific rpm and in any gear.i guess if the sensor are getting something then maybe the exhaust flow speed at that moment may be off or something on the lines of that.

When you did your exhaust did you tune the car?

 

[zackmd1]

Thank you for the reply. But the odd thing is that my sensor aren't actually getting any of exhaust through them since I raised then away from the pipe not to trigger cel from no cats. I might have to do some data logging. I'll try that out. It's strange since It happens at specific rpm and in any gear.i guess if the sensor are getting something then maybe the exhaust flow speed at that moment may be off or something on the lines of that.

When you did your exhaust did you tune the car?

Unfortunately this is a symptom of a catless setup on the 15 V6. Believe me, I know.... SD fuel calc is off causing a momentary lean condition around the 2800-3000rpm range. The only way to fix this is a tune... Unfortunately there are no tuners for the V6 that can tune for no cats... Right now anyways. Try lund as they are SUPPOSE to be tuning for lethal performance's cat deletes.

 

[astolt12]

Thank you for the reply. But the odd thing is that my sensor aren't actually getting any of exhaust through them since I raised then away from the pipe not to trigger cel from no cats. I might have to do some data logging. I'll try that out. It's strange since It happens at specific rpm and in any gear.i guess if the sensor are getting something then maybe the exhaust flow speed at that moment may be off or something on the lines of that.

When you did your exhaust did you tune the car?

When you say sensor are you talking about using anti foulers bored out to fit the H02S and then screwing it back into the port? they still will measure emissions but essentially what does is allow more air to be read by them tricking your PCM into thinking its correct.

if that is the case only do those on the downstream sensors, as there is no need to back them out of the upstream ones.

When i did this all it was on my 11GT and yes it was tuned. even with anti foulers ad high flow cats I would get an issue, so I just had them turn the sensors off in the tune.

 

[HunterStang]

Unfortunately this is a symptom of a catless setup on the 15 V6. Believe me, I know.... SD fuel calc is off causing a momentary lean condition around the 2800-3000rpm range. The only way to fix this is a tune... Unfortunately there are no tuners for the V6 that can tune for no cats... Right now anyways. Try lund as they are SUPPOSE to be tuning for lethal performance's cat deletes.

That's unfortunate, so I can't get this correctly tuned with the sct?

 

[HunterStang]

When you say sensor are you talking about using anti foulers bored out to fit the H02S and then screwing it back into the port? they still will measure emissions but essentially what does is allow more air to be read by them tricking your PCM into thinking its correct.

if that is the case only do those on the downstream sensors, as there is no need to back them out of the upstream ones.

When i did this all it was on my 11GT and yes it was tuned. even with anti foulers ad high flow cats I would get an issue, so I just had them turn the sensors off in the tune.

Yes that's what I mean. I did it only in the downstream sensors since those are after the cat. So basically a tune is the only solution.

 

[zackmd1]

That's unfortunate, so I can't get this correctly tuned with the sct?

Currently no. Unleashed doesn't have a car to build the correct tune as I am 800 miles away from them.

Lund, according to lethal performance, is suppose to be building a tune for catless setups. It concerns me though because I have yet to get a straight answer from lethal on the issue.

 

[HunterStang]

Currently no. Unleashed doesn't have a car to build the correct tune as I am 800 miles away from them.

Lund, according to lethal performance, is suppose to be building a tune for catless setups. It concerns me though because I have yet to get a straight answer from lethal on the issue.

This is all very upsetting news. Anyone know how much lund tunes are?

 

[zackmd1]

This is all very upsetting news. Anyone know how much lund tunes are?

Their EB tuning services run $200 so I would expect near the same. It is very concerning that lethal sold you the delete pipes without warning you of the issue.

 

[HunterStang]

Their EB tuning services run $200 so I would expect near the same. It is very concerning that lethal sold you the delete pipes without warning you of the issue.

Yeah I had no idea this would happen. I didn't have this issue on my 12, but that's because Diablo sport had a tune. Unleashed told me that they can give me a tune so that there won't be a cel from the catless exhaust.

 

[zackmd1]

Yeah I had no idea this would happen. I didn't have this issue on my 12, but that's because Diablo sport had a tune. Unleashed told me that they can give me a tune so that there won't be a cel from the catless exhaust.

Torrie can give you a tune that will make the hesitation much less noticeable but it will still be there. I have moved to highflow cats and I still have the issue. If you are anywhere near St. Augustine, Florida then I would highly suggest meeting up with Torrie so he can properly dyno tune it. You will also be helping me out! Haha

Another reason why this wasn't an issue on previous gen 3.7 was that they were MAF and not MAP. MAF is more adaptable then the current MAP sensor.

 

[HunterStang]

Torrie can give you a tune that will make the hesitation much less noticeable but it will still be there. I have moved to highflow cats and I still have the issue. If you are anywhere near St. Augustine, Florida then I would highly suggest meeting up with Torrie so he can properly dyno tune it. You will also be helping me out! Haha

Well less noticeable is something. Haha yeah i wish I could but ik from NYC. A tad bit far away.

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