Removing CATS for MPG

[Kevin Lang]

The parts & labor for "hacking" off the OEM Y-pipe's pre-cats

The original post didn't say anything about the Y-pipe though. In fact, it only says "converter", and if you're only hacking off one, the one past the O2 sensor requires nothing but a new piece of pipe to be put in.



So I'm taking the "hate" because my assumption was different from your assumption on the original post? :unsure:



Anyhow, +1 to the ScanGauge II. It is awesome, and you can set it to match the green interior color scheme to boot.

 

[TrainTrac]

So I'm taking the "hate" because my assumption was different from your assumption on the original post?

:huh: What "hate"? Not sure what you meant by that. The original post said:

Lets just put all that aside for the moment and try ot see if we the result of removing them.

That, and the somewhat desperate-sounding tone of the full post led me to presume that Towtrac was considering the drastic step of removing all the cats in an attempt to save a few $$$ on gas. If you recall, the Y-pipe has four pre-cats between the exhaust manifolds and the two main cats on the exhaust pipe. No worries, KL. Guess you and I just interpreted Towtrac's original post differently.



However, you did say:

if you're only hacking off one, the one past the O2 sensor requires nothing but a new piece of pipe to be put in.

Not entirely true. If you replace the two main cats with a piece of "test" pipe, you'll need a new tune to prevent throwing a CEL code, which will mean ~$400 for an XCal3 + tunes. The only cats that can be totally removed without throwing a code are the four pre-cats on the Y-pipe. That's why the R/T Y-pipe is a direct bolt-on, plug-and-play part.

 

[Gavin Allan]

Its a TRUCK, not an economy car.



If you want better MPG, get a smaller car.

 

[Kevin Lang]

Not entirely true. If you replace the two main cats with a piece of "test" pipe, you'll need a new tune to prevent throwing a CEL code, which will mean ~$400 for an XCal3 + tunes. The only cats that can be totally removed without throwing a code are the four pre-cats on the Y-pipe. That's why the R/T Y-pipe is a direct bolt-on, plug-and-play part.

4 precats on the y pipe? I thought there were only 2.



I am fairly confident that the last cat in the exhaust on the ST is past the last 02 sensor, so test pipe can go in there effortlessly. Also, I said that one--that one beyond the cats--could be removed, and you're taking about replacing two cats, which as you say requires additional work, though I'm not convinced that only the xcal has the power to eliminate the 02 sensor.



*The original post first talks about removing one. So it says one definitively, then implies more than 2, so what is there to do but bicker about semantics and assumptions :huh:



While I'll probably pick up the Y pipe somewhere down the line, the fact that it (and all car parts) cost so much for being just a simple bent metal tube is ludicrous. All the people developing microprocessors are in the wrong business as their products are incredibly complex and deal with precision in nanometers and represent the technological evolution of thousands of years...and cost about the same as a Flowmaster muffler which advertises that it is accurate to within 0.001 inches (wheras a nanometer is 0.00000003 inches), or a third of a freaking bent hunk of metal.

 

[Richard L]

Removal of the Cats is not going to be worth all the trouble and headache of dodging the law, especially if Florida cracks down on vehicles meeting the Federally mandated polution standards. In the end any MPG gain will be so small that you will probably not even notice any improvement.



If you want to save gas, get a trip computer or a Scan Gauge that shows instantaneous mileage. You can actually watch your gas mileage and see how acceleration, and other driving habits effect your gas mileage.



My MB has such a trip computer that allows you to see how you accelerate from a traffic light effects your gas mileage. If I accelerate quickly, I can see my gas mileage drop about 1 tenth of a MPG every 20-30 feet as long as I am holding the gas pedal at that position. If I start out slowly I can see the mileage drop 1 tenth of a MPG every 250-300 feet.



The heavier the vehicle the more load there is to get moving and the faster you try to move that weight, the more HP and gas it takes to do that



My MB is rated at 18 MPG city and 25 MPG highway. My total mixed driving is 24.7 MPG for the last 21K miles and I have gotten as much as 31.8 MPG on long trips of 800-1200 miles.



People think they drive to save gas, but a computer or Scan Gauge can quickly show you which driving habits are saving you gas and which habits are wasting gas.



...Rich

 

[Johnny O]

With the exhaust, K&N, and (for what it's worth) Mobil 1 0w-30 oil, I got 22 mpg if I kept it to 65 on a flat road. Truck is rated at 19 hwy. Saw as high as 23 mpg in Florida where it's really flat. MPG seems to be a bit down now with the new A/T tires though.

 

[TrainTrac]

4 precats on the y pipe? I thought there were only 2.

It's been quite a while since I removed mine and installed the R/T y-pipe, so my recollection isn't clear on exactly how many cats are on the y-pipe. Could be two or four. I guess it doesn't really matter in this discussion.

I am fairly confident that the last cat in the exhaust on the ST is past the last 02 sensor, so test pipe can go in there effortlessly.

At the aft end of the y-pipe where it comes together into the single exhaust, there are indeed two catalytic converters in the exhaust pipe. And the O2 sensor is just aft of these converters. If you look at the picture of the R/T high-flow cat on the Zabteck website, you can see the bung for the O2 sensor just aft of the cat, and this is the exact same position as on the OEM cat pipe. So eliminating these cats with a test pipe will require a tune to prevent throwing a CEL code.

I'm not convinced that only the xcal has the power to eliminate the 02 sensor.

Vendors who write tunes for XCal3, Diablo Predator, etc. (like Torrie) do it all the time for folks who go with a straight exhaust. As far as I know, that's the only way to do it and not get a CEL code.

 

[Richard L]

JohnnyO,

22.5 MPG is what I could get driving a steady 65-70 MPH in mixed terrain between Texas and Ohio, on both of my Sport Tracs, and I only had a K&N drop in filter.



My point is not the engine modifications that are returning better gas mileage, it's driving habits that really makes the difference. You often cannot control the terrain you drive in, how much traffic there is, or your route to and from work, etc, but some simple modifications to your driving habits can return a very substancial savings in gas mileage.



If you vehicle is tuned properly, tire inflated properly, and you are driving to save gas you will get respectable gas mileage for the weather and traffic conditions where you drive. If you are getting poor mileage, just learn how to drive to conserve fuel. Something like an accurate Scan Gauge or trip computer can point out what are good and bad driving habits in a very simple and understandable language...Instantaneous MPG !



...Rich