What do you guys think of an 2 inch exhaust catback?
Engine is totally original. Only a few small mufflers.

I like to know all the cons and pro's on this. Possible engine damage when driving hard for a long time?

 

Good question and the answer is always the same. The better you can remove the exhaust byproduct from an internal combustion 4-cycle (stroke) engine, the better it will perform and the more efficient it will be.

It takes energy to push the exhaust from an engine and reducing the expended energy (via enlarging the cross-sectional diameter of the exhaust, removing restrictions (headers, porting, etc.), the easier the engine will cycle and perform. Pushing the exhaust from a cylinder through the exhaust valve, the head, the exhaust port and manifold and subsequently through the down tube, cats, piping to the exhaust outlet takes power. Making the exhaust gasses flow easier, no matter where, will always result in using less power, therefore improving the engine's performance, although it may seem negligible considering you aren't increasing the exhaust from the exhaust port all the way out.

Anything you can do to make an engine inhale or exhale (intake/exhaust) more easily will always benefit the engine. The fuel management system should respond by making the minor adjustments, depending on the fuels you use and how much is changed.

***DISCLAIMER***: The only way to truly see or realize any benefit would be to run a baseline dyno pull three times, average your end results then change the exhaust, run it for a few days to account for adjustments in fuel management then take three more pulls on the dyno to see any improvements.

Hope this helps. I'm sure there are many more guys and gals here who know far more than I do about it.

~Andy

 

Thanks for your reply.
I am asking this because Its already under my car. I havent thought this all over before installing it. Very stupid I know.

The setup on this moment: Straight piped and I lost the middle cat. Original cats are still there. At the end I have 2 mufflers with internal tubes and vavles to open and close. See picture.
When the valves are closed in the silent mode the diameter of the tube inside that muffler is 44.5mm. I,m quite scarred about this because I dont want to have to much back-pressure and hurt my engine with this mod.

 

Clean setup! I don't think there's an issue with back pressure, only that it will change drastically whenever you open the cutout (bypass) or close it and that will create issues with the LS computer trying to manage differing values between the front and rear O2 sensors in each bank. Fuel trim is an issue too, and whenever there is a significant differential in the exhaust pressures (open vs. closed system, open, shut, open, shut....), it tells the fuel management system to lean or enrich the trim and mixture. This can produce readings that may cause your CEL to come on periodically or worse, cook an O2 sensor and I assure you, the rears are not the most fun to change out...

The only thing I would suggest would be to try it out and see how your engine and mileage goes if it's already installed. Likely, the mufflers you have installed have near equal back pressure and restriction to flow so there's not going to be much harm in leaving them in place. The issue only likely will arise when you open the cutouts then close them again, over and over.. causing the system to adjust and possibly cooking an O2 sensor, though this may be highly unlikely (I'm certain more people here know far more than I do about the fuel management system in the LS430 than I do).

I had a setup like this on my 2011 CVPI (Ford Interceptor) and found my engine management didn't like it at all. The constant changes killed my mileage and low-end torque and while it sounded awesome, performance dipped by a few TQ/HP due to the sudden reduction/restriction in back pressure from the open/shut cutouts and no chance for the fuel management system to adjust. Now when I left the system open for a day or two and ran it full throttle into the redline like I usually do in that car, the system would level itself out and run great but, one cannot run around town with an OHC V8 at redline with open exhaust for long without getting eyeballed by the law... y'know?

I hope this helps, and again, low-end torque may suffer slightly with an open system but mid-range and top end power and mileage will thank you for the reduced back pressure.

~Andy

 

Thanks for the explanation!

These mufflers are deleted now and I have some Simons Big 51's to test if they are silent (for the silent mode) but they are LOUD + they sound really deep and I hat that! Even louder then straight piped... The drone is killing me. Now I gave order to a manufacturier to make the most silent muffer they can make so I can make a bypass and a tube around it.

 

One correction about O2 sensors. Pre catalytic converter sensors do all the important work managing the fuel to air ratio. Post cat sensors are sniffers only, for the cats themselves.

Also some back-pressure is important. You will loose power if you go too big.

 

Then I am very happy with my 2 inch setup.
I already made a complete new setup in 2 inch but ill post all the details later in my build topic. I've putted massive loads of time and money on this now.