If so what did you go with? was it a direct fit with a flange connection?
Thanks,
Nick

 

Are you running headers? Larger Y-pipe?

 

yup,the X is currently apart doing the Thorley header and Y install

 

In my opinion, your not going to notice much more hp or torque.

I had my exhaust done by a shop that has a great reputation with v10's and diesels. They talked me out of a higher flow cat.

They claim that the stocker has a good flow rate and also the V10 needs a little restriction to run properly. If you add the a straight pipe or a higher flow cat with Ypipe and headers she will probably have a drone, lose low end torque etc.

Just my 2 cents, I really trust my exhaust guys!

PS. After the cat you can do whatever you wish without problems. I ran dual 3in pipes after the mufler.

 

Thanks LL for the info I'm think the FM SUV and dual 3" tails

 

I eliminated my cat on mine with a 4in exhaust into the Banks muffler and it did create some drone but I can feel an increase in pick up on the highway not sure about any torque loss on the low end, but seems to run just fine but the drone and noise is getting annoying as it did increase exhaust noise considerably! Noticed a very slight increase in MPG as well.

 

My OEM one came apart and started rattling so I put a Magnaflow stainless one on mine. I noticed a difference with no cat and just a straight pipe while I was waiting on the new one to arrive - but not really with the new one on.

 

Are you running headers and larger y-pipe?

If your not, that would be fine, but that larger y-pipe mod without a cat I'm pretty sure you would lose some low end torque.

That's the reason I had asked first.

 

Yeah I've got the Banks Power Pack on my truck with the headers and y-pipe as well!

 

Good to Know, I guess if my cat gets mauled by the dog, I would try a High flow cat since the OEM cat is so ridiculously priced. Meow

 

Ok guys let’s put this backpressure myth to bed.

Gas engines do NOT need backpressure to function properly and or create optimal torque. I can understand why people think that is the case but the answer to what is really going on is more complicated than that.

I’ve done quite a bit of research on backpressure because I was thinking of experimenting with a turbine based HHO generator on a small car. My idea was based on the backpressure myth. I figured if an engine needs backpressure that you could remove all other sources of back pressure like the CAT and muffler and put a turbine in place. The turbine would run a generator which would power a HHO electrolysis cell. The concept was that if the car needed backpressure that you could harness power while creating backpressure to increase fuel economy.

The problem is that backpressure is a myth. I used to strongly believe in it, here is why:

Have you ever had some small crap car with a rusted out muffler or broken exhaust line? If so did you ever try to drive it anyway, say up a hill for example? If you did, you’d notice right away that it had no power. Now most people just assume that it doesn’t have the needed back pressure to run correctly.

Well after doing a lot of reading on the subject I have found out that it isn’t about backpressure at all. It is all about proper flow. The best example of why proper flow is important is manifolds vs headers. Everyone agrees that headers improve performance. Interestingly enough most people know why but they forget about it when it comes to the rest of the system. Headers improve performance because they provide a discrete path for the exhaust gasses from each cylinder. This is very different from a manifold which just kind of dumps all the exhaust gasses into a collector in which the gasses swirl and move aimlessly about until they happen to be forced out of the hole into the exhaust pipe.

Here is the real key, the longer it takes for the exhaust to get out of any part of the exhaust system or the exhaust system as a whole the cooler and therefore denser it gets. Cooler denser gasses move slower and make the exhaust system less efficient.
I am stating that open headers are the most efficient exhaust system there is. The second most efficient system would be a straight pipe setup, but only if the pipes are exactly the right size. A small pipe or pipes will restrict flow too much, that is obvious. If the pipe or pipes are too large it will cause a cooling effect and the exhaust will be allowed to hang around and spin back on itself.

A nice aftermarket muffler not only improves the sound but they improve the flow, so those are great.
The CAT is a tricky subject, as noted above the stock CAT on the Excursion has pretty good flow. Some aftermarket high flow CAT may be better but eliminating the CAT all together in the correct way is the best.

Don’t gut the CAT. I had a gutted CAT on my old ’97 F250HD CC 7.5L it droned a lot! Well think about what is going on in there. Just like a manifold but worse, all the exhaust gas dumps out of a 3” pipe into a big oval shaped box, where it cools and spins and bounces around front to back and side to side. This could be worse than a restrictive CAT that has a clear path from one end to another.

Furthermore the larger 4” pipe mentioned above was said to drone. Well at some point after the Y the 3” pipe had to turn into 4” and right at the point where that happens the gasses push in to the center of a wider opening where some gasses are allowed to sort of fold back around the edges. Also remember that it is not a constant stream of gasses, it is pulsating as the cylinders fire one by one. So the best way I can visualize it is like smoking a cigarette and blowing smoke rings, you push the smoke out and suck back and the ring forms. That is what is happening when the small pipe goes into the large one, or when the small pipe goes into the gutted CAT. It becomes a big echo chamber full of gasses in various stages of cooling and density all smashing into each other.

Anyway, I am tired, I’ll stop ranting now. Think about it though. Oh yea, and can someone tell me one good reason why the exhaust valve needs pressure on it to push gasses out? No, you can’t because it makes no sense.

So let’s all try to better understand just exactly what is going on inside the exhaust system so that we can all do whatever modifications we need to in order to keep the exhaust gases as hot as possible and flowing as quickly as possible.

Good night!

 

Great post Computer Cowboy. You explianed it alot better then I normally do. I think about what people do in motorsports. NHRA/Nascar they want the most power they can get. How are there exhaust ran. NHRA runs stright headers off each cyclinder. While Nascar runs exhaust pipes to the passenger side infront of rear tire to move the Carbon monoxide away from the drivers compartment. Thats the way I look at it

 

Go for it and post results!

 

Great Post! You explained it very well. Can you expound on this part a bit more? Referencing the pressure on the exhaust valve. Are you referring to the valve spring or cylinder pressure, or? I am curious.

 

I don't know, I'm not a mechanic or an engineer. My point is that the job of the exhaust valve is to push out exhaust gas. How would pressure in the opposite direction help exhaust gas to get pushed out?