'03 3.0 2WD exhaust, improving efficiency while maintaining reasonable noise.

[bhgl]

Howdy folks,

Preface: The goal for my build is fuel economy, and highway driving comfort. Spending any amount of money for the potentially microscopic improvements in fuel economy is typically foolish, and debatable, however given the pretty restrictive system currently on the truck I know some improvements can/need to be made from the headers back. I'm looking for answers and recommendations, and ways I can go about pricing a header-back system. It's also a fun project that's seen some good results already, that being said.

The vehicle isn't going to be tuned any time soon, it currently has an upgraded ignition with an MSD Coil, and Gapped plugs but that's it, and aside from some potential modifications to the intake that's how it is likely to remain.

Problems with the current setup:

Restrictive flow: The stock diameter overall isn't the worst I've seen at 2-2.25 inches, however the system overall does appear to be more restrictive than it ought to be. In-gear coasting results in a very significant slow down, even when the engine should be able to either maintain speed, or otherwise shed speed less quickly in its highest gear.

When quickly revving in park, there's a noticeable almost backfire type sound, 3 almost knock (but not engine knock) like noises, I imagine if there wasn't a muffler in the way these would be much louder. I haven't been able to replicate it while driving so I'm assuming it's as a result of the engine trying to bring its revs back down while fighting with the pressure from the exhaust, I'm imagining the CAT may be in some part clogged. Less backpressure should in theory allow me to coast in gear longer while scrubbing less speed, and using less fuel.

Current state of the stock system:

I can't say the system currently has any leaks, but it's lived a life in Northern Ontario Canada, and will most certainly be crusty at best, that's why I'm more partial to removing everything from the headers back, and starting from scratch, that alongside the age of the CAT. O2 sensors are in reasonable condition, but could do with replacement.

I need to confirm the condition of the headers as far as leaks go, but I'm pretty confident that they're doing just fine given that the truck doesn't show any symptoms of a leak at the headers, and the truck's current mileage of only 87 000 KMs.

Sound:

This is probably one of the least important categories for me, but I do have some considerations.

I will say, as much as I am partial to the sound of this V6 as is, given my use case I wouldn't mind actually hearing it even less. With around 100 hours of driving over 20 days slated for the end of the year, exhaust drone, and noise overall really affects your ability to keep moving after hours on the road.

Overall I'm happy with the stock sound in general, but wouldn't mind less drone, as the engine spins between 2750-3000 RPM at highway cruising speeds.

What I'm looking for:

1. Recommendations on products/managing the CATS and o2 sensors, since they are required where I live I will in fact be putting one on, but that is the minimum requirement. I am seeing products that include a front, and rear catalytic convertor, I'm wondering how the PCM may react to only having one CAT in front of its 02 sensor, in either of these configurations:
   
   
   
   
   
2. Opinions on single exit vs. dual exit systems. Pros of single exit being better scavenging, and overall lower cost vs. in theory better flow from a dual setup.
3. Diameter for pipe sizes throughout the system, I'm partial to making the post muffler section at 2.5, or potentially throughout.
4. Product recommendations: I'm going to avoid complete systems short of a really good deal, as I have access to the tools needed to purchase and bend my own tubing. I'm looking mainly for mufflers, CATs, and other fasteners/parts that might make the job easier. Depending on how creative I get, I will most likely have to scavenge some flanges from the front end of the old CAT/s, but that shouldn't be too much of a job.

 

[franklin2]

I think you need to spend your time and money elsewhere. If you are indeed looking for economy, the engine will be turning so slow the stock system should not be a restriction. High flow pipes are for rpm, a area you will not see for economy correct?

 

[pentode]

I'm definitely not an engine guru but having the same truck and drivetrain as you, I'm interested in your project.
A few things are rattling around in my head from your post: backfires, excessive engine braking, exhaust drone, possibly clogged cat.
Isn't engine braking related mainly to manifold vacuum as much as anything else? And am I wrong to think that a clogged cat might explain the backfires? And possibly the drone as well?
I took a 1000 mile road trip in my truck last winter, all highway miles, and I thought the truck was surprisingly quiet- I didn't notice any drone on the stock exhaust.
Isn't there a way to test for backpressure with a vacuum gauge? Or is my memory faulty yet again? I'm just thinking that if you could solve all your problems with one or more new cats, would that be preferable? Or maybe you're looking for a project.

 

[bhgl]

I'm definitely not an engine guru but having the same truck and drivetrain as you, I'm interested in your project.
A few things are rattling around in my head from your post: backfires, excessive engine braking, exhaust drone, possibly clogged cat.
Isn't engine braking related mainly to manifold vacuum as much as anything else? And am I wrong to think that a clogged cat might explain the backfires? And possibly the drone as well?
I took a 1000 mile road trip in my truck last winter, all highway miles, and I thought the truck was surprisingly quiet- I didn't notice any drone on the stock exhaust.
Isn't there a way to test for backpressure with a vacuum gauge? Or is my memory faulty yet again? I'm just thinking that if you could solve all your problems with one or more new cats, would that be preferable? Or maybe you're looking for a project.

Great reply,

This is my first Ranger, and actually my first time owning body on frame, RWD truck, and also the oldest vehicle I've ever owned, so it's hard for me to figure out what is working on the vehicle as perfectly as it would in stock/perfect/brand new condition, I just have to use my previous experience with FWD small cars and sedans and go from there. All that being said, the truck is in good working order, if I weren't working looking for things to fix/improve or didn't care I wouldn't notice these issues I mentioned.

I wouldn't quite call them backfires, but it does sound like some amount of unburnt fuel is getting into the exhaust situation somewhere, it happens more often when the truck is cold.

The exhaust sound is perfectly reasonable and quiet considering its age, again I wouldn't change it if I didn't want to, and it has no real drone. I do very long road trips across Canada as my vacation, and I swear that driver comfort is just as important as how much gas you burn, so even less noise is appreciated. It's something that would be nice to improve, but I have some sound isolating material to install.

Engine braking is also affected by backpressure from the exhaust, that's what Exhaust braking is. When you want to slow down using the engines you induce a restriction in the exhaust. Both intake vacuum, and exhaust backpressure gives the engine more work to do on each full power stroke, vacuum pulling against the piston on the intake stroke, back pressure works against the piston as it's trying to push exhaust gases out. Usually an intentional exhaust brake is only used in commercial/heavy duty towing setups.

There is a way to check what the backpressure is via an adapter for a vacuum gauge, but uh... I need to find that adapter...

I'll most likely have to fab that y pipe+CAT setup though if I want to reduce backpressure over stock, I haven't found too many premade ones online.

You're definitely right that either the front Y cats, or the rear cat could be clogged, or restricted and changing them could improve all the things above. I'll most likely have to fab the CAT sections if I want to reduce backpressure compared to stock, I haven't found too many flow cats for these trucks yet.

 

[pjtoledo]

according to my 2000 owners manual engine braking only happens when OD is turned off.
does a 2003 operate the same way?

 

[pentode]

I’m familiar with exhaust braking - Jake brakes etc. I’ve just never heard of issues with exhaust restrictions in a street car causing excessive engine braking barring extreme damage.

 

[bhgl]

I think you need to spend your time and money elsewhere. If you are indeed looking for economy, the engine will be turning so slow the stock system should not be a restriction. High flow pipes are for rpm, a area you will not see for economy correct?

If I wasn't looking for a project I'd agree with you completely, but this is the research stage.

At highway speeds this truck is actually running within it's power band since I'm in 4.10 gearing. By turning off overdrive I can keep the engine turning in its sweet spot of 2750-3250 RPM this range and above has the leanest section in the fuel curve with stock tunes, and it can breathe freely. Aside from gains in general combustion efficiency, the only improvement would be from on throttle coasting downhill/uphill sections where I need to balance throttle input with speed. The less resistance in the engine from backpressure means less throttle/air/gas on those downhill sections.

Likewise when moving uphill less speed being scrubbed from engine resistance at the same throttle position means I can coast in throttle up hill longer, both super important for long distance fuel economy.

Since I don't typically need engine, or exhaust braking in my use case it's a fair trade off and I think I'll see some efficiency gains by decreasing backpressure just enough.

 

[pentode]

according to my 2000 owners manual engine braking only happens when OD is turned off.
does a 2003 operate the same way?

What I’ve noticed with my 5R44 is that the trans is pretty smart and will hold it in gear when appropriate. I haven’t owned many automatics and almost no “modern” automatics but I’d have to say this one is impressive despite any criticisms. Probably not super strong but seems efficient.

 

[pjtoledo]

I'll have to look at the tachometer sometime when I slow down.
if revs drop faster than the speedometer then there isn't much engine braking.
if anything, I would venture a guess the transmission would coast more than brake.

 

[pentode]

I'll have to look at the tachometer sometime when I slow down.
if revs drop faster than the speedometer then there isn't much engine braking.
if anything, I would venture a guess the transmission would coast more than brake.

Yeah, in my experience you get very little engine braking from an automatic. It takes a clever transmission to understand the situation and stay locked in gear. If the torque converter isn’t locked up it’s just going to spin anyway right?

Other than this truck, the only automatics I’ve owned were 70s-80s GM products, no lockup torque converters

 

[pjtoledo]

getting back to the original issue of manipulating the exhaust system.....
check for parts availability, the Y pipe for a 2000 3.0 without cats is no longer in stock anywhere.
and when you break the seal between the Y pipe and the main cat rust 'n deterioration will
probably prevent it from being reassembled.

 

[bhgl]

I'll have to look at the tachometer sometime when I slow down.
if revs drop faster than the speedometer then there isn't much engine braking.
if anything, I would venture a guess the transmission would coast more than brake.

If my recollection of the drive I had 1.5 hours ago I would say that sounds about right, it is in fact an auto, I think this is where my time driving small cars is informing me, I find this truck engine brakes substantially more than those cars manual and auto, and if I can reduce that I should be able to drive a bit more efficiently.

I know intake and exhaust pressure still affect power/efficiency even through an automatic, I think the 4.10 in the back also factors in.

getting back to the original issue of manipulating the exhaust system.....
check for parts availability, the Y pipe for a 2000 3.0 without cats is no longer in stock anywhere.
and when you break the seal between the Y pipe and the main cat rust 'n deterioration will
probably prevent it from being reassembled.

If I couldn't find the Y pipe my idea was to scavenge the flanges, or new ones if they're too crusty and weld them up to a couple small cats instead.

 

[pentode]

Any chance that you’re noticing the engine braking more in the Ranger because the trans is staying locked in gear where your small car automatics just spun freely due to non-lockup transmissions?

 

[bhgl]

Any chance that you’re noticing the engine braking more in the Ranger because the trans is staying locked in gear where your small car automatics just spun freely due to non-lockup transmissions?

That could be it frankly, but I do know even non locking torque convertors impart some momentum or resistance on the engine short of being completely mechanically disconnected, those forces are most present when dealing with gravity in both directions and wind drag so it's still in play.

I don't think these trucks have locking torque convertors though?

 

[pentode]

Definitely a lock up torque converter. Maybe some auto trans guy will want to chime in but this is a fairly sophisticated transmission.
Mine gives a tiny little shudder occasionally under certain torque loads and situations. Just to say it’s not just but old fashioned slush box.