Alright Well I am going to redo my whole exhaust.

I have 4 stock cats. I want to run a little bigger piping off the headers. Now to do so I have to get rid of the stock cats. I still want cats. I have 3 02 sensors, 2 before the cats, and the last one after 3 of the cats. I was thinking of doing a little bigger piping, and having 2 highflow cats before that last o2 sensor.
Will this effect performance in a bad way because there will be 1 less cat before that last o2 sensor?

Any suggestions to help improve my idea, or go another way? Thanks again!!

-Jared

 

Depends, do you have smog testing in your state? my town you don't even have to have an exhaust.

Ford to meet exhaust standards jus throws on another cat until it makes emissions. I think as long as you keep howevor many cats you have 02 sensors for, you'll be good. I don't undestand 3 02 sensors heh, but whatever. Take off the last one.

Oh yah, they're all high flow cats. Not like they slow down the exhaust flow or anything...

Aaron

 

if im not mistaken arent all those cats there because it doesnt meet emissions while the cats are cool? im just thinking what would be wrong with just one cat?

 

First off, Cats don't do anything but hurt performance. They are on there as a smog control device. Ford put three on there to get emissions as low as possible. Would you be okay removing one, probably. Replace them with high flow cats and your performance will be improved but your emissions will go up as well. It all depends on where you live and what your laws are.

Here in California we have the strictest emissions standards in the country and doing anything with the cats is technically against the law unless the OEM cats fail. then and only then you are allowed to replace it with something similar to the OEM cat. Does this prevent people from running catless or putting in hi flow cats, not really.

IF you remove your cats you'll probably need to install a device to eliminate the Check Engine Light that will come on. This is easy and the cost is minimal. (in most cases)

So to answer you question in short:

No Cats - Best performance, higher emissions, may not be street legal

Hi Flow Cats - Compromise between maintaining emissions and performance, may or may not be street legal.

OEM Cats - no performance gains (performance restriction really) but totally legal.

 

on ford rangers:
Hi Flow Cats = OEM cats...





I think the point you are all missing here is that jared has a supercharger. he wants to do bigger piping all the way through t get the most out of the super charger. Jared, doug can tune out the 02 sensors for you if you were looking to run straight pipes. and apparently if you have a friend in the business, or buy a friend in the business you can get past emissions. i wouldnt know because I have never had to do emissions on my truck cause of where its regstered...



EDIT: also no cats doesnt necessarily mean best performance either. some backpressure is needed for torque...

 

But superchargers and Turborchargers make TQ and the small amount of tq that you lose by freeing up the exhaust is more then made up for.

With forced induction tuning and performance you want to have as much free flow as possible. With Forced Induction, Backpressure is bad. in N/A applications it is good to have some backpressure because it's more difficult to make TQ then with forced induction.

yes, I should clarify, there are cases where removing all restrictions in the exhaust will result in a loss of TQ if you don't have other supporting mods to make up for it. You'll get more HP, but TQ is what gets you moving.

 

that is correct!

 

There are 2 oxygen sensors in the Y-pipe upstream of all the cats. Your 2003 has a 3rd O2 sensor between the 3rd and 4th cats for the Catalyst Monitor.

You need to keep the front O2s to control the closed loop mixture. You could eliminate the rear O2 sensor and your truck will still run fine but get ready for a perpetual CEL. That CEL should fail you at any state IM test.

The two small front cats in the Y-pipe are called light-off or preheater cats and their purpose is to get the big rear cats up to temperature sooner and to keep them hot during periods of idling or very low speed operation. The rear 2 cats, due to their much larger substrate area do the great majority of the actual exhaust cleanup.

You could probably get by on an emission test with just the 2 large underbody cats IF you can keep the temps high enough to allow high conversion efficiency. If you have a state IM emission test, you may not be able to pass it if it is preceded by a long idle period. You would definitely not pass a real FTP chassis rolls test as done by the EPA to certify a car or light truck for sale.

From your description, I wasn't sure if you were going to stay with a Y-pipe and two cats in series or do true duals with the cats in parallel. Either way you do it, you will need to have the rear CMS O2 sensor sampling both banks. With true duals this would require an X-pipe or a short H-pipe.

 

You sir are the freaking MAN!!!

Now my question is.... I want to be able to pass my IM test when the time comes.

My whole reason for asking this is because I want to be able to open my exhaust up enough since i installed the supercharger. Im not sure on the size of the piping, But it is small and i want to go the next size up, maybe more.

SO any suggestions on how to keep it in Emmissons. without worrying if its hot enough.

I do not want to do true dual.... i like how it is set up now, just I want bigger pipes.

do they make PRE highflow after market cats or what?

ANy info would be awesome!

 

You are correct on most but not all, you want some backpressure for a turbo to spool it up off the line. There is a fine line to walk here but you do want some, it will help with lag.

As far as the third O2 on the GM vehicles it does have some play in the fueling of the vehicle in closed loop operation. Also unless he has a O2 eliminator then he will never be in closed loop becuase of the CEL. Not sure if Ford is the same and I imagine it would not be too far off but Bob is the Resident Ford man here so he would be the most knoledgable on the Ford end of it.

 

Are you kidding? You need to be sure the up-pipe isn't too big so that you create velocity at first, but after the turbo is irrelevant.

 

Ford's stock cats are considered high flow. How about if you got the stock light off cats from a late model with a larger displacement engine and larger inlet/outlet tubing? Maybe even cobble up the complete Y-pipe to fit. Then add whatever you want for high-flow rear cats. From an emissions point of view, you'd have the rough equivalent of what you have now and it should pass the test without problems.

Another thought. Do you know what your maximum exhaust gas temperature is? Most common cats deteriorate more rapidly when the substrate temp exceeds 1650F. To stay below 1650F means that you need a maximum exhaust gas temp into the cat of about 1450~1500F. If your blower is making the temperatures go sky high, you can expect shorter cat life, especially the light offs. If it hits 2200F, you're in danger of melting the substrate.

 

Do you understand the lag you would have if you did not have exhaust on the car?

I found this and you are absolutely correct on the up pipe, not all cars have up pipes though.

Pre-turbo exhaust velocity is critical to boost response. Improperly oversized header and up-pipe systems lower exhaust velocities slowing spool up for larger turbos decreasing power and increasing boost lag.

If you have some backpressure then it will aid if the up pipe was too big.

Back on topic of Jareds exhaust.

 

No. I don't understand. AFTER the TURBO is of no matter.. Adding any restriction isn't going to help, only hurt performance. Boat applications, where turbo lag is a HUGE issue they don't run anything other than a 3" long 45 degree elbow to divert the exhaust flow upward.

P.S. Turbo applications don't use "header(s)" ... They are manifolds..

 

This is absolutely correct.

You want to build velocity in the Turbo Manifold and get the gasses through the turbine quickly and then have as little restriction as possible once the exhaust gasses are through the turbocharger.

End threadjack...

 

That information that you PS about was copied from another site, this is done. We have different opinions and that is all, you do what you want with turbos and I will do what I want. They will both work in the end.

 

In this case, it appears that headers and a catback exhaust is your best bet. The best part, you can do both of those and still be 50 state legal as long as your headers are carb approved, and it looks like carb approved headers exist.

 

2.5" pipe is the best! the bigger pipe make the exhaust sound deeper.