LS4 Performance - Catless DP without a tune for a few days?

Well I planned on gettin the DP and LS1 intake on this weekend so I could have Lew work his magic, but the guy modding my OPSU will be gone fishing until Monday. I know the DP will throw a code, but will it cause any problems?

Also I loaded the 91 oct trinity tune, but where is the DOD delete option at? I only had like 10 min to load the tune, so I may have missed it. Also is there a way to make the trinity show gauges that actually matter like trans temp, oil pressure, A/F ratio?

May run rich but that's about all, which isn't a bad thing except for your fuel economy..

I run my CAI and Catless DP/custom 3" catback without a tune. still noticed an increase in economy.

It's not gonna hurt anything, and actually, the catless DP leans you out a little. You'll set a code, but that's about it.

It's not gonna hurt anything, and actually, the catless DP leans you out a little. You'll set a code, but that's about it.

First time I have ever heard someone say running lean wasn't bad... you must enjoy burning up pistons, valve damage, preignition, etc.. I was always under the impression that on newer vehicles they can have a "fail safe" so to speak so that if the o2 sensors arent reading correctly (or not even existent) the computer will compensate by dumping extra fuel to avoid knocking/pinging. Hence the reason why you should change out the o2 sensors every so often along with a tune-up to improve performance and fuel economy. But since I have less than 1,000 posts I must not know what I am talking about.

Whatever, man.

I said a little lean, not dangerously lean. As long as he's not out there beating on it, he'll be fine. Besides, the assumption is that this will be temporary setup for him until he gets a tune.

And if you're going to be a dick about it, I'll point out that at least I didn't give him the wrong information like you did.

Whatever, man.

I said a little lean, not dangerously lean. As long as he's not out there beating on it, he'll be fine. Besides, the assumption is that this will be temporary setup for him until he gets a tune.

And if you're going to be a dick about it, I'll point out that at least I didn't give him the wrong information like you did.

It wont run lean it will run rich. Im not being a dick about anything, just stating facts. But... whatever guy you seem to know everything and want to correct all of my posts on this forum.

The ECU sees that the cat is not working right because of the (or lack of) information it is getting from the O2 sensors. It has no idea the cat is gone. So it throws more fuel into the engine to attempt to heat the converter up, to make it more efficient. Resulting in exactly what I said in my first post. Your wrong, sorry.

Your assumption isn't supported by facts.

Drive around with a scan gauge attached to your car for a while and monitor LTFT after you've removed the cat but before you get a tune and you'll see a lean condition.

As far as me correcting you, sorry. It's not personal. Quit offering your opinion as fact and you won't be corrected.

Im not assuming anything. Its going to give a false lean condition.. meaning its not really lean but the comp thinks it is, therefore dumping more fuel... i dont think we will agree on this, so im just gonna agree to disagree with you and say whatever.

Fair enough.

The intake swap will make it a bit rich, but the cat less DP will lean it out a bit. Its simple science behind that. Your both right. OP is obviously fine without a tune if fubar has been running his untuned for some time.

I have been running mine untuned with a scan tool to monitor my LTFT's since install of the catless DP/custom 3" catback/CAI. you'd be surprised at exactly what i found.

My LTFT's typically stay within +/- 5 all the time. usually under 3 either way. That is the "learned" portion of your vehicle's fueling adjustments. being so close to zero indicates the mods are within the vehicle's margin for fuel adjustments. You will do no harm to your vehicle in this case. Your fuel and/or spark could ALWAYS be optimized for more power...however you are not appreciably losing power from this condition. Optimally you want this to be 0 all the time...indicating aside from STFT adjustments the vehicle needs to make no other changes to your learned fuel maps.

I still saw a roughly 1-2mpg increase after the mods. I'll attribute this to more time spent in 4cyl mode. because of making more power the car doesn't need to switch back to 8 as often.

oh and computers don't think anything. humans do. that's our downfall.

Well I planned on gettin the DP and LS1 intake on this weekend so I could have Lew work his magic, but the guy modding my OPSU will be gone fishing until Monday. I know the DP will throw a code, but will it cause any problems?

Also I loaded the 91 oct trinity tune, but where is the DOD delete option at? I only had like 10 min to load the tune, so I may have missed it. Also is there a way to make the trinity show gauges that actually matter like trans temp, oil pressure, A/F ratio?

there is no option to turn it on or off.. you have to install the correct tune that has it already disabled in the tune... one of the "No DOD" tunes...

there's a 91 Octane No DOD tune, and a Diablo Tune No DOD tune...

no, can't log any tranny parameters... I think there's one for oil pressure, I know there's one for Equivalence Ratio...

I emailed you earlier with a Word doc that has all the parameters listed that you can log, and where to find them.


when logging to get a tune, there are only certain ones that I need logged:

Air Fuel Ratio (Equivalence Ratio) = Under FUEL menu

Long Term fuel trim bank 1 = under FUEL menu

Spark Advance = under IGNITION menu

Intake air Temp = under INTAKE menu

MAF Sensor Mass Air Flow = under INTAKE menu

MAF Sensor Frequency = under INTAKE menu

Total Knock Spark Retard = under MISFIRE menu

Engine Speed (RPM) = under PERFORMANCE menu

Commanded Throttle position = under THROTTLE menu


those are the only ones you need to select to log... the less items you log, the better the log will be, because it will have a faster sampling rate with less parameters needed to be logged, so you'll get more rows of data...

I have been running mine untuned with a scan tool to monitor my LTFT's since install of the catless DP/custom 3" catback/CAI. you'd be surprised at exactly what i found.

My LTFT's typically stay within +/- 5 all the time. usually under 3 either way. That is the "learned" portion of your vehicle's fueling adjustments. being so close to zero indicates the mods are within the vehicle's margin for fuel adjustments. You will do no harm to your vehicle in this case. Your fuel and/or spark could ALWAYS be optimized for more power...however you are not appreciably losing power from this condition. Optimally you want this to be 0 all the time...indicating aside from STFT adjustments the vehicle needs to make no other changes to your learned fuel maps.

I still saw a roughly 1-2mpg increase after the mods. I'll attribute this to more time spent in 4cyl mode. because of making more power the car doesn't need to switch back to 8 as often.

oh and computers don't think anything. humans do. that's our downfall.

That is really interesting to me.. I know that the o2 sensor after the cat wont have anything to do with adjusting the a/f mixture and only throw a code if its out of whack (saying sumthin is f'd up with the cat) thats the job of the o2 sensor before the cat (yes?) so in theory without it, the cars a/f mix should run as if it is always cold, and as everyone knows cars run very rich on start up to heat up the cat... etc etc, so confused. Sorry I just wanna know for sure so im not givin out bad info..

That is really interesting to me.. I know that the o2 sensor after the cat wont have anything to do with adjusting the a/f mixture and only throw a code if its out of whack (saying sumthin is f'd up with the cat) thats the job of the o2 sensor before the cat (yes?) so in theory without it, the cars a/f mix should run as if it is always cold, and as everyone knows cars run very rich on start up to heat up the cat... etc etc, so confused. Sorry I just wanna know for sure so im not givin out bad info..

The O2 in the rear manifold controls fuel mixture. The post cat O2 is simply there to verify catalyst efficiency.

If you flat out remove the cat or eliminate the O2 without computer tuning on SOME post 01 cars it MAY get stuck in a diagnostic loop where it commands pig rich and expects a specific response if the cat is in good shape. If it doesn't see the correct response it can get looped BUT it is only on SOME cars not ALL...this may be the rich condition you are referring to...fortunately I have yet to experience this on my 08 GXP and also did not on my pre 2001 vehicles.

Otherwise...despite the P0420 code for catalyst system efficiency below threshold you should experience no ill effects from a cat removal...but id use a scan tool to verify. You can get a cheap bluetooth obd2 reader on ebay for 25 bucks and Torque for android headsets is only abour 4.80...and it works well!

Thanks a lot guys. It Will only be that way for a week or hopefully less. I think the DP is going to be a bigger headache than the intake swap. I feel a breaker bar and a drill will be coming in handy tomorrow. Looked at it tonight and decided not to bother with it. Especially since it'll be in the dealer for a new wheel bearing tomorrow morning. Using up every last bit of that 5 yr powertrain warranty.

It's not bad. Only 4 bolts. If you have a hard time put plastic wrap around the bolts, seal the ends with tape, and poke the straw from a wd40 bottle inside the plastic wrap and spray until you can see the fluid, and let the wd40 sit in there for a good half hour or longer and they'll come right out

The O2 in the rear manifold controls fuel mixture. The post cat O2 is simply there to verify catalyst efficiency.

If you flat out remove the cat or eliminate the O2 without computer tuning on SOME post 01 cars it MAY get stuck in a diagnostic loop where it commands pig rich and expects a specific response if the cat is in good shape. If it doesn't see the correct response it can get looped BUT it is only on SOME cars not ALL...this may be the rich condition you are referring to...fortunately I have yet to experience this on my 08 GXP and also did not on my pre 2001 vehicles.

Otherwise...despite the P0420 code for catalyst system efficiency below threshold you should experience no ill effects from a cat removal...but id use a scan tool to verify. You can get a cheap bluetooth obd2 reader on ebay for 25 bucks and Torque for android headsets is only abour 4.80...and it works well!

Sorry for thread jackin lol.. but yes thats exactly what I was thinking. Thanks for clarifying that for me, i feel better now ;)