(?) 4x4 with rear cats replaced with straight flow resonators

gr8titan · Apr 24, 2005

I searched and found a few threads started by 4x2 owners where they replaced their resonators with straight pipes, however, I would like some info from 4x4 owners who had replaced their rear pair of cats with resonators.

Reason I'm asking is because I just received the long awaited 2.5" T-304 SS straight flow resonators and would like some 1st hand feedback from 4x4 owners who have done it before I rush to have it installed. Any difficulties, regrets or is it pure adrenalin?

For the technical gurus, any recommendations or suggestions? Will mod this void any warranty? If it does, is it worth the risk vs any power gain achieved? Would the 2 front cat be adequate to pass me the emission tests?

Any info would be appreciated.

HudsonValleyTitan · Apr 24, 2005

If you removed the cat(s) Your SES light will come on and your mileage will be worse. Replacing just a resonator shouldn't pose any problems.

The_Man · Apr 24, 2005

Does anyone think these resos might cure the mild drone from my Flowmaster 70 system?

Mike H. · Apr 24, 2005

I don't see how it could cause a problem. There are no sensors of any kind in the exhaust downstream of the 2nd cats, therefore there is no way for the computer to know they have been removed.

Now as far as passing an emissions test, that may well be a problem.

sleightofhand · Apr 24, 2005

I removed them on my 4x4 and the ses light came on after I drove it a while. When I called jba they said that they would have to be reconnected. I dont know if you could buy some of the sensors that go with the 4x2s resonators but my truck would not accept the missing cats.

Mike H. · Apr 24, 2005

sleightofhand said:
I removed them on my 4x4 and the ses light came on after I drove it a while.

How did it find out? Sneaky little SES light.

sleightofhand · Apr 24, 2005

It must have something to do with the amount of time the gasses stay in the pipe. I was told why buy i think i blocked it out of my mind as loosing the cat was the reason i had bought the jba in the first place.

TitanHauler · Apr 24, 2005

HudsonValleyTitan said:
If you removed the cat(s) Your SES light will come on and your mileage will be worse. Replacing just a resonator shouldn't pose any problems.

Replacing the rear two cats with straight pipe will not trip the SES light. All you have to do is have the shop weld in bungs for the rear O2 sensors and as long as you have no leaks you should be fine. I know one person for sure who has done this on a 4X4 and had no problems. You figure the 4X2's only have the front cats and run fine and presumably will pass emissions, why would a 4X4 be any different? Although the reason for the additional 2 Cats on the 4X4's has been debated, bottom line is you don't need them for the Titan to run fine and benefit from the additional flow. I can't however guarantee it will pass the emissions test if your state has one.

I have alot of miles on mine since removing the resonators and no problems. I had a few leaks at first that tripped the SES light but new gaskets took care of it and I have been SES free for a while now. Personally, I would not remove the rear cats because I live in the socialist state of California but if I lived in the mid-west? Those babies would be gone!

TitanHauler · Apr 24, 2005

sleightofhand said:
I removed them on my 4x4 and the ses light came on after I drove it a while. When I called jba they said that they would have to be reconnected. I dont know if you could buy some of the sensors that go with the 4x2s resonators but my truck would not accept the missing cats.

I bet you had a leak and didn't know it. My SES light came on the very next morning after my resonators were removed but I heard no leak. I contemplated having the resos re-installed all day. I got on it really hard up an onramp to the freeway that evening and bam! The leak was revealed. Had new gaskets installed at the front most flanges and problem solved.

IMHO, JBA techs seem a little ignorant on the Titan. I had one insist that all Titan's had 4 Cats!!! I offered to drive my truck down to San Diego to let him see for himself but he quickly changed the subject. Also, they released the kit (Pre-12/04) with one application for both 2 and 4 wheel drive and marketed it as emissions legal in all 50 states. However, that kit clearly would require the removal of the rear cats on a 4X4. They have since redesigned the kit and as far as I know it fits as good as any out there but does not replace the cats or resos anymore. I honestly just don't think they did their homework in the beginning. Many people are happy with their system and I'm definately not bashing it as it seems to make good power and is well built. But the Titan knowledge of the techs seemed a little deficient to me which turned me off.

gr8titan · Apr 24, 2005

cats changing to resos

Thank you folks for the info.

So far this is what we've gathered: 1. SES light came on on several occasions and the suggested solution is to have better gaskets to prevent leaks. Another possible overlooked cause is not welding a "bung" to reinstall the O2 sensors. After the SES lights were corrected, everything turned back OK.(?) 2. Emission is still questionable. No info as to the actual passing or failing with the rear cats of a 4x4 being replaced with resos. (though 4x2 only have 1 pair of cats & are legal) Or maybe someone has a "friend" that could just "test" off the record?? 3. There is one positive statement on power gain but not very encouraging.

Any other feedback out there? Again the biggest question is: Why would my 4x4 develop a problem having the rear cats replaced with resos when the 4x2's only have a pair of front cats and a pair of rear resos? And just exactly what I'm doing is to convert to a 4x2 type of exhaust!! How about warranty? Any Nissan dealers or service person/s members of TT?

For 4x2 owners that have removed their resos with straight pipes, can you post photos of your OEM resos? I'm just curious about their internal characteristics. Thanks in advance.

Mike H. · Apr 24, 2005

JUST DO IT. Somebody has to be the guinea pig. Might as well be you. Once you get the bugs out, I'll do it.

QShip · Apr 24, 2005

gr8titan said:
Reason I'm asking is because I just received the long awaited 2.5" T-304 SS straight flow resonators

This may be a silly question, but here goes. Why aren't there any flanges on the resonators?

HudsonValleyTitan · Apr 24, 2005

Mike H. said:
I don't see how it could cause a problem. There are no sensors of any kind in the exhaust downstream of the 2nd cats, therefore there is no way for the computer to know they have been removed.

Now as far as passing an emissions test, that may well be a problem.

Correct me if I'm wrong but, (and maybe I'm misunderstanding) there are 4 cats on the Titan.....right?....all of which have O2 sensors (There are 4). Removal of any of the 4 will cause problems for the computer. But the resonators are not monitored so they won't trip the light. Am I missing something?...lol. I haven't modded my exhaust so......I'm not as informed as some of you folks. :ftard:

sleightofhand · Apr 24, 2005

What kind of gaskets did you buy? I have two bad leaks right now that you can see and hear where the cats meet up with the y pipe. The leak has not caused any ses light to come on, and its been leaking for about 4 months now. When i had my cats removed there was no visible or audible leak and my ses light stayed on, seems odd with a bad leak and them installed i get no ses light warning. Let me know about the gaskets you used though as i am changing my exhaust again. It bothers me the pipes i had to get made so the jba would fit up to the cats are not madrel bent.

gr8titan · Apr 24, 2005

QShip said:
This may be a silly question, but here goes. Why aren't there any flanges on the resonators?

I will have the fabricators of my exhaust system install the resonators using identical flanges as a "bolt on" system so I can reinstall the original cats if I needed to.

For those who have not seen my system, here's some thumbnails to give you an idea of how it looks like and why I would like to keep the same overall appearance in the replacement of the cats with these resonators.

Sleighofhand: Gaskets will be provided by the fabricator.
HudsonValleyTitan: There are 4 cats in a 4WD compared to 2 cats + 2 resos in a 2WD Nissan Titan. Why? I would like to know too myself. Anyway, if my goal is to have a 2WD exhaust system (2 cats+2 resos), why would it be any different with visual emission inspections? How do the inspectors even know the difference between the two Titans? Any help or ideas are greatly appreciated.

Thank you again to everyone who have shared info on the cat replacement.

TitanHauler · Apr 24, 2005

HudsonValleyTitan said:
Correct me if I'm wrong but, (and maybe I'm misunderstanding) there are 4 cats on the Titan.....right?....all of which have O2 sensors (There are 4). Removal of any of the 4 will cause problems for the computer. But the resonators are not monitored so they won't trip the light. Am I missing something?...lol. I haven't modded my exhaust so......I'm not as informed as some of you folks. :ftard:

I think what's confusing you is that all 4 O2 sensors are before the last 2 cats on a 4X4 and before the resonators on a 4X2. Unless your exhaust can somehow flow backwards, the O2's will never read conditions in the last 2 cats in order to trip an SES light.

TitanHauler · Apr 24, 2005

sleightofhand said:
What kind of gaskets did you buy? I have two bad leaks right now that you can see and hear where the cats meet up with the y pipe. The leak has not caused any ses light to come on, and its been leaking for about 4 months now. When i had my cats removed there was no visible or audible leak and my ses light stayed on, seems odd with a bad leak and them installed i get no ses light warning. Let me know about the gaskets you used though as i am changing my exhaust again. It bothers me the pipes i had to get made so the jba would fit up to the cats are not madrel bent.

Any exhaust leaks after the last two O2 sensors will not trip the SES light. The most common leak is at the flange after the first two cats and before the 2nd set of Cats/Resonators because the second O2's will sense the leak. Any leaks at the flanges after that will not trip the SES light because there are no sensors to communicate that anything is wrong. I have no idea what kind of gaskets the shop used to correct the leaks. All I know is they were metal core.

TitanHauler · Apr 24, 2005

gr8titan said:
Anyway, if my goal is to have a 2WD exhaust system (2 cats+2 resos), why would it be any different with visual emission inspections? How do the inspectors even know the difference between the two Titans? Any help or ideas are greatly appreciated.

That is a good question Gr8 but you would be surprised what will pop up on their screen when they enter your VIN number (at least in CA). I can't imagine that if 4 Cats weren't required to pass emissions on a 4X4, Nissan wouldn't have bothered. My theory on the 4 Cats is that 4X2's will likely stay in metropolitan areas and see very limited off-road duty where as a 4X4 will likely venture off the beaten path to rural areas. The EPA might have pressured them to keep the nature air cleaner. Just a theory. The only way to know for sure if the cats will prevent you from passing emissions would be to go down and get tested. If you fail you have plenty of time to reinstall the CATS before you test again for real.

NorCal 4x4 · Apr 24, 2005

TitanHauler said:
That is a good question Gr8 but you would be surprised what will pop up on their screen when they enter your VIN number (at least in CA). I can't imagine that if 4 Cats weren't required to pass emissions on a 4X4, Nissan wouldn't have bothered. My theory on the 4 Cats is that 4X2's will likely stay in metropolitan areas and see very limited off-road duty where as a 4X4 will likely venture off the beaten path to rural areas. The EPA might have pressured them to keep the nature air cleaner. Just a theory. The only way to know for sure if the cats will prevent you from passing emissions would be to go down and get tested. If you fail you have plenty of time to reinstall the CATS before you test again for real.

While the EPA idea might be possible because of Fed BLM land use, etc., in general California rules are more lax in rural counties. In fact we don't even have to smog check our vehicles, unless we sell them, (even though many of us commute to the counties that do require the checks). Also, I believe the rural counties use a higher polluting/better gas mileage blend of gas. [Costs more where I live so I buy the city blend].

RockyMtnTitan · Apr 24, 2005

I just got my Dynomax bullet resos (thanks M95roadster) and O2 bungs to do my rear cat replacements on my 4X4. No one I've found in Colo will touch the cats cuz of EPA regs/fines. I'm driving to Cheyenne, Wyo on Friday to get it done.

Here's my take on the reason why 4WD has 4 cats, based on talking to a couple different muff shop owners. The 4WD model due to it's added load on the motor, esp in 4WD mode, will not burn as clean as a 4X2. Nissan must have added the extra cats do get the 4WD models to comply with EPA standards, although I'd bet in 2WD mode, it'll burn as clean as a 2WD, or close to.

As far as failing emissions, I think there's a chance of failing the visual part. The emissions tech may see a flag or something on the comp screen when they punch in the model/vin of the vehicle noting the quantity of cats...don't know. That's why I'll be keeping my factory cat sections so I can pop 'em back in come emissions time.

On the SES issue, as TH said, you will not get a light unless you develop a leak before the rear O2 sensor. The only reason that rear O2 sensor is there is to monitor the performance of the foreward cats. The ecm compares the readings of the O2/af ratio sensor in the exh manifold to the O2 sensor before the rear cat or reso. If it sees that emissions are reduced to the correct levels, then it knows the primary cats are working, if not, it'll generate a SES. There is no monitoring of the secondary cats.

(?) 4x4 with rear cats replaced with straight flow resonators

gr8titan

Attachments

HudsonValleyTitan

The_Man

Mike H.

sleightofhand

Mike H.

sleightofhand

TitanHauler

TitanHauler

gr8titan

Mike H.

QShip

HudsonValleyTitan

sleightofhand

gr8titan

Attachments

TitanHauler

TitanHauler

TitanHauler

NorCal 4x4

RockyMtnTitan

Top Contributors this Month

Recommended Communities