So my alternate idea is to do a full custom system with 49 state high flow cats and dual 3" pipes with a cross over that both feed into a Flowmaster 50 series Big Block. That has a Single 3.5" out and due to its size, would require me to have the exhaust exit at the stock location or use a turndown. The challenge with that idea is that the Powerboost has a 3" exhaust component near the battery. I do not know what it is, but I believe that it is a heater for the cool loop so that the battery can heat up in the cold (best guess, I welcome other ideas or actual knowledge). It is certainly not another O2 sensor, as those are clearly visible. My 2 ideas for dealing with that are 1) have dual 3" pipes with one flowing through the "heater" and the other bypassing it or 2) using the "heater" as the crossover. The drawback on idea 1 is that I could increase the time for my battery to warm up in cold weather, presuming that I have correctly identified the part. The drawback of 2 is that if it is a heater, it likely is not open pipe, and thus I will not only have a 3" venturi in my otherwise dual 3" setup, but also a 3" venturi with internal obstructions, which may completely negate all of my other efforts.

I'm not messing with any of this until my powertrain warranty is out, so probably 3 years, but I do appreciate all of the help hashing out ideas. Maybe it will help others as well.

 

If you're doing all this to the Powerboost (and for the love of $DEITY don't do stacks... talk about a douchey brodozer move), and that "heater" you're discussing really has to do with the battery, you're likely endangering your battery warranty by modifying it. Thermal management is critical to battery longevity and failing to properly manage the battery temp can result in early failure or overcharging/battery fire.

 

Agreed. The closest that I was willing to do was bypassing it with half of the exhaust and leaving it alone otherwise. My understanding is that cold reduces the charge capacity of a lithium battery, but that heat is what can cause thermal runaway and damage. To that end, the worst case scenario should be "battery takes longer to heat up in the cold", which would require that I either wake up the truck before using it, garage it, or just put up with the engine staying on longer on cold days. However, I agree with your concern, and I'm curious what the actual flow penalty would be for having a 2.5" long section where the dual 3" pipes merge into one 3" pipe. If doing so doesn't negate the benefit of a custom exhaust, keeping things stock is my strong preference.

And yes, the "brodozer" look was my chief reason for being wary of stacks at all. As crazy as it sounds, I think that what I had in mind would've been subtle-appearing and quiet enough that I could've avoided that. Most casual observers would not have realized that the truck had a stack exhaust. Of course I may be nuts and would've actually turned my truck into an 1991 S-10 with a rusty trashcan in the bed, in which case thanks for saving me from the Good Idea Fairy.

 

Unfortunately, my concern would be that the dealer would see any mod to the exhaust (assuming you're right and this is some sort of heater or something) and say "nope, denied"... throw Magnuson-Moss around all you want, you likely don't have the legal horsepower it would take to fight that battle.

I'd love for someone who knows more about this "heater" system to chime in... there would have to be some sort of thermostat in there, as you wouldn't want the batteries getting heated when you're already in the middle of August in south Texas or Arizona.

 

The other relevant question is: what is the practical benefit of increasing the exhaust pipe above the stock 3" vs keeping the stock single 3" pipe and replacing the cats and muffler with high flow units? Specifically, If I can just chop off the resonator, replace the muffler with a Flowmaster 50 Series Big Block and replace the cats with 49 state units and get 80% of the flow increase, why bother all of the extra trouble? I plan to add a "cold air" intake and a thicker intercooler, but I'm not getting bigger turbos or an aggressive tune.

The heater might also be fore the cab and not the battery system. It is physically close to the battery and charge controller, but tracing wires and trying to guess at what they do is my entire basis for reasoning at this point.
Here is a thread on the mystery part:
https://www.f150gen14.com/forum/thre...-5eb-too.4776/

 

There is no practical benefit to any of this. You may gain some decreased turbo spool time... but once the turbos light off the engine power is largely controlled by the wastegate and timing tables. Its not like you have a NA engine and are trying to fine tune the exhaust for scavenging.

 

I keep coming back to this thread to see pics of stacks and am let down everytime..........

 

Same here...

 

I mostly run the thing in ECO mode and I'm actively trying to figure out if 87 octane gives me a lower cost/mile vs 93. The craziest thing that I've done or will do was accelerate pretty quickly in Sport mode up to 70 MPH after leaving a rest stop in rural West Texas. The 10R80 is supposed to be designed for 590 ft lb, so adding a ton of power could give me transmission issues down the line while failing to increase my brake limited towing ability.

I think the main practical benefits are 1) from high flow cats and 2) chiefly manifest in reducing back pressure and therefore heat transfer within the turbos. Point one is why I'm not just putting a cat back on it....it would have to be glass-pack loud to do any good. My ultimate goal is to be able to run turbo blankets, and that is directed at keeping heat out of the engine compartment (where there are a million inaccessible plastic connectors that all want to bake into brittle twigs) without cooking the turbos. I realize that peak power can't improve without a tune and probably larger turbos, but I don't particularly want higher peak figures (towing is brake limited as is and the stock motor makes more torque than the Duramax did when I was growing up). Rather, my goal is to protect the engine compartment form heat, avoid baking the turbos in the process, and keep power available even under adverse conditions (i.e. while towing, though I will likely be towing only in high temperature, low altitude, high humidity climates in the SE where the radiators work plenty well) by limiting heat soak. Finally, the small turbos that Ford specced the engine with from the factory work great for me as they are already designed to spool fast rather than slowly built to massive boost like Jay Leno's turbine powered motorcycle.

So the end goal is getting exhaust out of the truck as fast as possible while staying within 1) Federal and state laws 2) the bounds of safety for whoever is in the truck and 3) keeping the noise down to stock or nearly stock levels (I don't care what the exhaust sounds like as long as I can't hear it in the cab). If I can get all of that by removing the resonator and replacing the muffler and cats while leaving the rest of the pipes alone, I'm thrilled. Most of the exhaust pipe calculators that I've seen put the stock motor's 387 HP pipe requirement at 3.07", and spec 410-420 HP at 3 1/4" pipe. Stock is 7 in^2 vs 8.3 in ^2, or 85% of the recommended pipe.

 

It was only ever going to be one stack, and I think that you were going to be pretty let down by a salt bath nitrided vertical 3.5" pipe on a black truck. Fortunately, others were able to convince me that even that would've been pretty BroDozer.

Maybe I will remake the thread so that I don't get anyone's hopes up of seeing me turn my truck into Jethro Frankenstein's monster.