2019 Straight Pipe-Surprising Result and Sound Clips

[C.E.Divine]

Mornin' Y'all!

I just finished a one week trial of my straight pipe and resonator delete, and I have to say that straight pipe life is the only life for me.

I knew I would be happy with the sound, but there has been another, very surprising benefit. As we all know, there is a common perception that straight piping can reduce low end torque.

Let me preface this by saying this is only butt dyno results, but I've put 50k on the truck and am pretty familiar with how it feels and drives.

I'm pretty sure I actually gained a significant amount of torque from idle to around 2300 rpm. On my daily drive, which is around 110 miles round-trip, I've noticed the truck holding on to eight gear for a lot longer, and it actually doesn't skip down to 7th or 6th gear on moderate inclines. It just chooches right up the grade.

I have also noticed no decline in economy even though I'm getting into the throttle more from a dead stop and am running with mds off now that it is straight piped. I can only attribute this to a need for less throttle when cruising.

As most of us would expect, there was also a good top-end gain. There are a couple passing zones I frequently use to get around semis, one of which is a downhill stretch where it's fun to fly. Before straight pipe, I would be back in my lane at 80-ish mph. I have used the same passing zone twice in the last week, and have found myself hitting 95 mph when I'm finally back in my lane.



None of this is remotely scientific, I don't have any dyno numbers or 0-60 times before and after. I'm just a real guy giving my genuine perception. And my genuine perception is that everyone should be straight piped.

 

[SB09]

Mornin' Y'all!

I just finished a one week trial of my straight pipe and resonator delete, and I have to say that straight pipe life is the only life for me.

I knew I would be happy with the sound, but there has been another, very surprising benefit. As we all know, there is a common perception that straight piping can reduce low end torque.

Let me preface this by saying this is only butt dyno results, but I've put 50k on the truck and am pretty familiar with how it feels and drives.

I'm pretty sure I actually gained a significant amount of torque from idle to around 2300 rpm. On my daily drive, which is around 110 miles round-trip, I've noticed the truck holding on to eight gear for a lot longer, and it actually doesn't skip down to 7th or 6th gear on moderate inclines. It just chooches right up the grade.

I have also noticed no decline in economy even though I'm getting into the throttle more from a dead stop and am running with mds off now that it is straight piped. I can only attribute this to a need for less throttle when cruising.

As most of us would expect, there was also a good top-end gain. There are a couple passing zones I frequently use to get around semis, one of which is a downhill stretch where it's fun to fly. Before straight pipe, I would be back in my lane at 80-ish mph. I have used the same passing zone twice in the last week, and have found myself hitting 95 mph when I'm finally back in my lane.



None of this is remotely scientific, I don't have any dyno numbers or 0-60 times before and after. I'm just a real guy giving my genuine perception. And my genuine perception is that everyone should be straight piped.

Sounds great. Did you use a kit or just make something up yourself?


Sent from my iPhone using Tapatalk Pro

 

[Grape_Ape]

I see you got the ghost trailer hooked up! lol just giving you a hard time. It sounds really good man!

 

[C.E.Divine]

Sounds great. Did you use a kit or just make something up yourself?


Sent from my iPhone using Tapatalk Pro

I've got a muffler shop that has done several bits of good work for me in the past.

 

[C.E.Divine]

I see you got the ghost trailer hooked up! lol just giving you a hard time. It sounds really good man!

And it's loaded to max towing capacity!

 

[Chippy]

Sounds tamer than most Borla that everyone ends up selling because too loud for the old lady or neighbour?

 

[C.E.Divine]

Sounds tamer than most Borla that everyone ends up selling because too loud for the old lady or neighbour?

I haven't heard a borla in person, but my ring doorbell captured this this morning. I don't see how Borla could be louder than this. The cold start is HELLACIOUS. I have to pretty much let it idle as I accelerate away or I'll wake the neighborhood.

 

[silver64]

Your top end speed increase shouldn't be a surprise. Any fears about the lack of back pressure since this will likely reduce engine performance below 2,000 or 2,500 RPM, making your vehicle a little slower to launch from a stoplight? Your engine may show more horsepower on a dyno – and might even finish the quarter mile a little faster – but it won’t be faster on the street. If you’re driving a vehicle on the street, your average RPM is going to range between 1,500 and 4,500 RPM. Most of the time, your engine is going to be at about 2,000 RPM. As a result, your vehicle’s stock exhaust system is sized (and tuned) to facilitate scavenging between 1,500 and 4,500 RPM. When a race team gets their hands on a stock vehicle, the first thing they’ll do is replace the factory exhaust with a bigger after-market system that doesn’t have a muffler. They do this because race cars spend most of their time driving around at high RPMs. A large, unrestricted exhaust is a great idea when you’re trying to maximize top end performance. You want an exhaust system that facilitates scavenging when the engine is going as fast as it can. Aside from the noise levels, straight pipes are not normally a good idea on a street truck. Theses comments are not to say that its wrong for everyone but its just generally a good idea to support the RPM levels you are driving at most often to maximize the engines output within those RPM ranges.

These are quick and dirty tables to figure correct exhaust sizing
Easy Way To Estimate: Your intake system needs to flow 1.5 CFM per engine horsepower, and your exhaust system needs to flow 2.2 CFM per engine horsepower.

Good Way To Estimate: Take engine RPM x (5.7) engine displacement, then divide by two. This is the intake volume. Use this same volume of air for the exhaust system, but then correct for thermal expansion (you need to know exhaust temps to figure things out).

Exhaust Pipe Size Estimate: A good section of straight pipe will flow about 115 CFM per square inch of area. Here’s a quick table that shows how many CFM each common pipe size will flow, as well as the estimated max horsepower for each pipe size:

Pipe Diameter (inches)​	Pipe Area (in2)​	Total CFM (est.)​	Max HP Per Pipe​	Max HP For A Dual Pipe System​
1 1/2​	1.48​	171​	78​	155​
1 5/8​	1.77​	203​	92​	185​
1 3/4​	2.07​	239​	108​	217​
2​	2.76​	318​	144​	289​
2 1/4​	3.55​	408​	185​	371​
2 1/2​	4.43​	509​	232​	463​
2 3/4​	5.41​	622​	283​	566​
3​	6.49​	747​	339​	679​
3 1/4​	7.67​	882​	401​	802​
3 1/2​	8.95​	1029​	468​	935​

NOTE: These numbers are just estimates. All pipes are assumed to be 16 gauge steel.

The table above is probably over-estimating pipe size, but you can see that a 400 hp vehicle with a dual exhaust system only needs 2 1/4 – 2 1/2 inch pipes. Anything larger is overkill.

My advice is Buy a tuned system if you can afford it. A tuned cat-back system is a great upgrade, as it’s dyno-tested and proven. They’re also usually built to OEM specs and RPM ranges based on the engine and trans combo's.

Sorry for the long post its probably information overload for most people!

 

[C.E.Divine]

Your top end speed increase shouldn't be a surprise. Any fears about the lack of back pressure since this will likely reduce engine performance below 2,000 or 2,500 RPM, making your vehicle a little slower to launch from a stoplight? Your engine may show more horsepower on a dyno – and might even finish the quarter mile a little faster – but it won’t be faster on the street. If you’re driving a vehicle on the street, your average RPM is going to range between 1,500 and 4,500 RPM. Most of the time, your engine is going to be at about 2,000 RPM. As a result, your vehicle’s stock exhaust system is sized (and tuned) to facilitate scavenging between 1,500 and 4,500 RPM. When a race team gets their hands on a stock vehicle, the first thing they’ll do is replace the factory exhaust with a bigger after-market system that doesn’t have a muffler. They do this because race cars spend most of their time driving around at high RPMs. A large, unrestricted exhaust is a great idea when you’re trying to maximize top end performance. You want an exhaust system that facilitates scavenging when the engine is going as fast as it can. Aside from the noise levels, straight pipes are not normally a good idea on a street truck. Theses comments are not to say that its wrong for everyone but its just generally a good idea to support the RPM levels you are driving at most often to maximize the engines output within those RPM ranges.

These are quick and dirty tables to figure correct exhaust sizing
Easy Way To Estimate: Your intake system needs to flow 1.5 CFM per engine horsepower, and your exhaust system needs to flow 2.2 CFM per engine horsepower.

Good Way To Estimate: Take engine RPM x (5.7) engine displacement, then divide by two. This is the intake volume. Use this same volume of air for the exhaust system, but then correct for thermal expansion (you need to know exhaust temps to figure things out).

Exhaust Pipe Size Estimate: A good section of straight pipe will flow about 115 CFM per square inch of area. Here’s a quick table that shows how many CFM each common pipe size will flow, as well as the estimated max horsepower for each pipe size:

Pipe Diameter (inches)​	Pipe Area (in2)​	Total CFM (est.)​	Max HP Per Pipe​	Max HP For A Dual Pipe System​
1 1/2​	1.48​	171​	78​	155​
1 5/8​	1.77​	203​	92​	185​
1 3/4​	2.07​	239​	108​	217​
2​	2.76​	318​	144​	289​
2 1/4​	3.55​	408​	185​	371​
2 1/2​	4.43​	509​	232​	463​
2 3/4​	5.41​	622​	283​	566​
3​	6.49​	747​	339​	679​
3 1/4​	7.67​	882​	401​	802​
3 1/2​	8.95​	1029​	468​	935​

NOTE: These numbers are just estimates. All pipes are assumed to be 16 gauge steel.

The table above is probably over-estimating pipe size, but you can see that a 400 hp vehicle with a dual exhaust system only needs 2 1/4 – 2 1/2 inch pipes. Anything larger is overkill.

My advice is Buy a tuned system if you can afford it. A tuned cat-back system is a great upgrade, as it’s dyno-tested and proven. They’re also usually built to OEM specs and RPM ranges based on the engine and trans combo's.

Sorry for the long post its probably information overload for most people!

Yeah, I'm aware of the scavenging thing. Like I said, it's just my perception. And in the end, perception of how it feels is the final word in having fun.