open exhaust okay? - Mustang Evolution

Go Back   Mustang Evolution > 1979-2015 Mustang GT || Tech and Talk > 2011-2014 Mustang GT



Reply
 
Thread Tools Search this Thread
Please support our sponsors and let them know you heard about them here!
Old 07-25-2013, 07:00 PM   #1
Registered User
Newbie
 
BAS433's Avatar
 
Join Date: Jun 2013
Location: Charlotte
Region: North Carolina
Posts: 13
With a little modification, I have hooked up my catalytic converters on my 13 GT to where they are now removable for track only use. The O2 sensors are disconnected right there after the cats. The exhaust is fully exiting out of the stock manifolds. Insanely loud? You have no idea but the benefits on track are greater. The car is track exclusive but I am keeping it street legal so the cats can go back on.

My question for those with experience is whether there is any risk or danger with running the open exhaust during DE or TT sessions? I have the tune to account for the open exhaust. I just don't want ignorance to cause any harm to the car. My hearing is a small sacrifice I'm willing to make.
BAS433 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 07-26-2013, 09:36 AM   #2
Registered Member
Regular
 
Joyride's Avatar
 
Join Date: Sep 2012
Region: Florida
Posts: 297
Damn, could you make a Gopro vid of them open like that! I'm not sure what could be bad about that but I have a feeling it could be pretty bad...
Joyride is offline   Reply With Quote
Old 07-26-2013, 11:24 AM   #3
Registered Member
Regular
 
Join Date: Dec 2011
Region: Canada
Posts: 2,976
If you're tuned for the open headers fine; at least that way you aren't burning up your exhaust valves, which you will if you aren't compensating on the fuel side. I wonder how your tuner accounted for this and what dyno cell allowed you to run open headers indoors to tune this up.

Everybody must just love you on the start line crew also.

You might find you're not gaining much, if anything from this, other than premature deafness. Running full open headers with shorties like this means you short-circuit the evacuation plan designed into the headers. These kind of work like a tri-Y used to, in that the balance of cylinder pulses is used to draw exhaust gases out of adjacent cylinders. You uncork the end completely and you pretty much kill that effect. I expect a significant drop in torque production off the bottom balanced by some mimimal gains in the high rpm.

Full, LT headers may see a bit of a gain from this but a shorty blasting at the firewall, not likely. Why don't you go the middle way and put in some test pipes where the cats were? This way you aren't risking gassing yourself to death, probably take no hit to power production and get all your low and mid torque back.
5LHO is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 07-26-2013, 11:40 AM   #4
Registered Member
Regular
 
Evil2014GT's Avatar
 
Join Date: Mar 2013
Location: Northern VA
Region: Alabama
Posts: 1,579
Quote:
Originally Posted by 5LHO View Post
If you're tuned for the open headers fine; at least that way you aren't burning up your exhaust valves, which you will if you aren't compensating on the fuel side. I wonder how your tuner accounted for this and what dyno cell allowed you to run open headers indoors to tune this up.

Everybody must just love you on the start line crew also.

You might find you're not gaining much, if anything from this, other than premature deafness. Running full open headers with shorties like this means you short-circuit the evacuation plan designed into the headers. These kind of work like a tri-Y used to, in that the balance of cylinder pulses is used to draw exhaust gases out of adjacent cylinders. You uncork the end completely and you pretty much kill that effect. I expect a significant drop in torque production off the bottom balanced by some mimimal gains in the high rpm.

Full, LT headers may see a bit of a gain from this but a shorty blasting at the firewall, not likely. Why don't you go the middle way and put in some test pipes where the cats were? This way you aren't risking gassing yourself to death, probably take no hit to power production and get all your low and mid torque back.
+1. Im not understanding the point of running open shorties either. As 5LHO already said, you aren't gaining nearly anything up top, and losing a ton of torque down low since you literally have no back pressure.
__________________
2014 Mustang GT Base MT82 -Stock 3.73s, Roush axleback, Steeda 93R tune, Steeda Hi-flow X-pipe, 19" Charcoal AMR's, smoked front and rear side markers, 20% tint, quarter window louvers, Steeda Ultralite springs, Koni Str.t shocks/struts, MM camber plates, J&M adjustable panhard bar, BMR LCAs and relo brackets, Barton shifter and 2-post bracket, Black Modern Billet Grilles
Evil2014GT is offline   Reply With Quote
Old 07-26-2013, 02:53 PM   #5
Registered User
Newbie
 
BAS433's Avatar
 
Join Date: Jun 2013
Location: Charlotte
Region: North Carolina
Posts: 13
It has always been my understanding that everything in your exhaust restricts the exit of exhaust gas thus reducing power and efficiency. Auditory factors excluded, why do people install aftermarket exhaust systems? They flow better, exhaust the gasses better, and in turn reduce backflow increasing HP, torque, and mpg. I'm no mechanical engineer but logic and deduction seem to indicate that reducing all restrictions behind the manifolds would be extremely beneficial. Main thing? Cats are expensive thanks to the platinum and racing burns them out exponentially quicker.

About the tune, I pulled a data log with my laptop and sent it to the tuner who made the adjustments based on prior tuning on my car.

I have thought about just putting some test pipes in place there.
BAS433 is offline   Reply With Quote
Old 07-26-2013, 03:11 PM   #6
Registered Member
Regular
 
Evil2014GT's Avatar
 
Join Date: Mar 2013
Location: Northern VA
Region: Alabama
Posts: 1,579
Quote:
Originally Posted by BAS433 View Post
It has always been my understanding that everything in your exhaust restricts the exit of exhaust gas thus reducing power and efficiency. Auditory factors excluded, why do people install aftermarket exhaust systems? They flow better, exhaust the gasses better, and in turn reduce backflow increasing HP, torque, and mpg. I'm no mechanical engineer but logic and deduction seem to indicate that reducing all restrictions behind the manifolds would be extremely beneficial. Main thing? Cats are expensive thanks to the platinum and racing burns them out exponentially quicker.

About the tune, I pulled a data log with my laptop and sent it to the tuner who made the adjustments based on prior tuning on my car.

I have thought about just putting some test pipes in place there.
People UPGRADE exhaust to improve air flow, not REMOVE it completely. You need to be able to burn the gas properly, and create back pressure. By running open shorty headers you are killing your low end torque. Yes, cats are restrictive, thats why so many people remove them, but i suggest you look into getting a set of longtubes if you want to run open headers. Longtubes, and some straight through bullet style mufflers will help get you some of your low end torque back by increasing back pressure, and perform even better at higher rpms. Not to mention, help your hearing..... A little bit anyway.
__________________
2014 Mustang GT Base MT82 -Stock 3.73s, Roush axleback, Steeda 93R tune, Steeda Hi-flow X-pipe, 19" Charcoal AMR's, smoked front and rear side markers, 20% tint, quarter window louvers, Steeda Ultralite springs, Koni Str.t shocks/struts, MM camber plates, J&M adjustable panhard bar, BMR LCAs and relo brackets, Barton shifter and 2-post bracket, Black Modern Billet Grilles
Evil2014GT is offline   Reply With Quote
Old 07-29-2013, 11:18 AM   #7
Registered User
Newbie
 
BAS433's Avatar
 
Join Date: Jun 2013
Location: Charlotte
Region: North Carolina
Posts: 13
Quote:
Originally Posted by Evil2014GT View Post

People UPGRADE exhaust to improve air flow, not REMOVE it completely. You need to be able to burn the gas properly, and create back pressure. By running open shorty headers you are killing your low end torque. Yes, cats are restrictive, thats why so many people remove them, but i suggest you look into getting a set of longtubes if you want to run open headers. Longtubes, and some straight through bullet style mufflers will help get you some of your low end torque back by increasing back pressure, and perform even better at higher rpms. Not to mention, help your hearing..... A little bit anyway.
I really appreciate the candid feedback. My next question, since you seem to have great experience and knowledge on this matter, is what if any difference would it make if I were to install a couple of down pipes for running the open exhaust? They would be 3" diameter and about 4-5" in length. Again, thank you.
BAS433 is offline   Reply With Quote
Old 07-29-2013, 11:50 AM   #8
Registered Member
Regular
 
Join Date: Dec 2011
Region: Canada
Posts: 2,976
Ok, you need something of a primer on header design, here it is:

What you propose won't do anything, as the collector in the header is too short and not fully the length of the stub stack. This header is a short, modified tri-Y style and is dependent, by its design, on an extant exhaust past the collector or it won't work at all. It needs to have the end closed to allow the variation in the pressure pulses to pull the exhaust from the alternating cylinders.

A full race, open header design blends the 4 tubes together into a single collector and the length of this blending and the subsequent single pipe determines how the header works. A way to figure out how long this pipe needs to be is to draw a wax crayon line on the collector pipe and where the wax stops melting, that's your collector pipe end.

You haven't accounted for the other factor other than flow that determines exhaust system effectiveness, thermal expansion. This factor is, on an NA car, a good 1/3 of the ultimate effectiveness of the system, more on FI. Harnessing that otherwise wasted energy and using it to move exhaust downstream is very important. This is a lot of the reason why changing axle-backs doesn't add any power. By the time the exhaust reaches the axle-back, it's slowed down so much that nothing much restricts its exit.

Your logic and deduction is lacking in the necessary knowledge to actually make it true. It's not as simple as more-in-more-out.
5LHO is offline   Reply With Quote
Old 07-30-2013, 08:35 AM   #9
Registered Member
Regular
 
ddinn25's Avatar
 
Join Date: Jul 2013
Location: Lebanon
Region: Ohio
Posts: 164
Your motor isn't to the point were it needs a completely OPEN exhaust. You need a bit of back pressure. You run the risk of burning up valves when running open shorties! I'd run at least long tubes and dump after the collectors. There are electric exhaust cut outs that can be welded in the mid pipe that I've seen work pretty good. I've raced cars and built my fair share. I've NEVER heard of anything GOOD from running open manifolds! In fact it's BAD! Yes there are cars (like derby cars) that run the zoomies but those are at least equal length and are still longer than the stock manifolds. The stock manifolds on these coyotes are NOT headers. There just a tubular manifolds. I WOULD NOT run open after the stock manifolds! Get some long tubes and run exhaust cuts out if that's you plan. Your not making enough power or moving enough air to benefit from open headers. In fact I would think it would run worse?
__________________
2013 5.0 m6 base 3.31's tint 20in Shelby razors 255/35/20 falken fk 452's koni srt.t's sr springs j&m phb gt500 mounts upr rear billet lower ca's upr brackets upr adjustable upper ca flowmaster at classics steeda cat deletes airaid cai premium st brace jlt catch can MGW shifter and blk ball. Currently bama tuned 400hp 383tq. Zex blackout kit w/msd digital window switch, fpss, zex bottle heater, bottle opener, blow down, and purge with a dyno tune coming soon..
ddinn25 is offline   Reply With Quote
Old 07-30-2013, 08:46 AM   #10
Registered Member
Regular
 
ddinn25's Avatar
 
Join Date: Jul 2013
Location: Lebanon
Region: Ohio
Posts: 164
Even on drag cars that run open long tube headers the collector had to be "tuned". If the collector is to long it will effect the way the car runs. Same if its to short. I usually start long (about 8in) and drawl lines with a grease pen. Fire the car up and let it reach operating temp. Look at the grease pen lines. Were the line hasn't burned/melted off is were I cut it. If the motor is set up/tuned rite both collectors will be of the same length and achieve the same temp. Also the headers point out to the sides of the car. I/we do this because the gases are still burning when they leave the heads and I wouldn't want a fire ball under my a$$! Also don't want to fill the car with exhaust gases! I'm no exhaust expert by any means! I know what has and has not worked for me in the past
__________________
2013 5.0 m6 base 3.31's tint 20in Shelby razors 255/35/20 falken fk 452's koni srt.t's sr springs j&m phb gt500 mounts upr rear billet lower ca's upr brackets upr adjustable upper ca flowmaster at classics steeda cat deletes airaid cai premium st brace jlt catch can MGW shifter and blk ball. Currently bama tuned 400hp 383tq. Zex blackout kit w/msd digital window switch, fpss, zex bottle heater, bottle opener, blow down, and purge with a dyno tune coming soon..
ddinn25 is offline   Reply With Quote
Old 07-30-2013, 08:48 AM   #11
Registered User
Newbie
 
BAS433's Avatar
 
Join Date: Jun 2013
Location: Charlotte
Region: North Carolina
Posts: 13
Quote:
Originally Posted by ddinn25 View Post
Your motor isn't to the point were it needs a completely OPEN exhaust. You need a bit of back pressure. You run the risk of burning up valves when running open shorties! I'd run at least long tubes and dump after the collectors. There are electric exhaust cut outs that can be welded in the mid pipe that I've seen work pretty good. I've raced cars and built my fair share. I've NEVER heard of anything GOOD from running open manifolds! In fact it's BAD! Yes there are cars (like derby cars) that run the zoomies but those are at least equal length and are still longer than the stock manifolds. The stock manifolds on these coyotes are NOT headers. There just a tubular manifolds. I WOULD NOT run open after the stock manifolds! Get some long tubes and run exhaust cuts out if that's you plan. Your not making enough power or moving enough air to benefit from open headers. In fact I would think it would run worse?
Good advise. I actually bought some electric exhaust cutouts but the way the stock exhaust is laid out on the 11-14 GT, they butted the cats almost completely up against the manifolds. There is only a very few inches of pipe between the manifolds and cats. The cutouts are about 18" so with clamping, I would have needed about 20-21". Definitely no room foe that. I had to just return them. I have a muffler shop fabricating a couple of test pipes to go in place of the cats. Flowmaster makes a good ball flange kit which is being used for ease of taking the test pipes on and off when I need to put the cats back on for emissions testing.

Thank you for the feedback. As I said in my original post, the last thing I want is for my own ignorance to potentially destroy something.
BAS433 is offline   Reply With Quote
Old 07-30-2013, 09:15 AM   #12
Registered Member
Regular
 
tc x 4's Avatar
 
Join Date: Jan 2012
Region: Indiana
Posts: 3,783
Quote:
Originally Posted by ddinn25 View Post
Even on drag cars that run open long tube headers the collector had to be "tuned". If the collector is to long it will effect the way the car runs. Same if its to short. I usually start long (about 8in) and drawl lines with a grease pen. Fire the car up and let it reach operating temp. Look at the grease pen lines. Were the line hasn't burned/melted off is were I cut it. If the motor is set up/tuned rite both collectors will be of the same length and achieve the same temp. Also the headers point out to the sides of the car. I/we do this because the gases are still burning when they leave the heads and I wouldn't want a fire ball under my a$$! Also don't want to fill the car with exhaust gases! I'm no exhaust expert by any means! I know what has and has not worked for me in the past
What temp grease pencil you using?
tc x 4 is offline   Reply With Quote
Old 07-30-2013, 09:16 AM   #13
Registered Member
Regular
 
Join Date: Dec 2011
Region: Canada
Posts: 2,976
Jegs sells test pipe kits for these cars already pre-fabbed.

JEGS Performance Products 30580 Off-Road Cat Delete Kit : Amazon.com : Automotive

Pulling the cats will require adjustments to the tune and likely shutting off the rear O2s to avoid a CEL. Or you could try using a defouler and see how that goes.
5LHO is offline   Reply With Quote
Old 07-30-2013, 09:38 AM   #14
Registered User
Newbie
 
BAS433's Avatar
 
Join Date: Jun 2013
Location: Charlotte
Region: North Carolina
Posts: 13
Quote:
Originally Posted by 5LHO View Post
Jegs sells test pipe kits for these cars already pre-fabbed.

JEGS Performance Products 30580 Off-Road Cat Delete Kit : Amazon.com : Automotive

Pulling the cats will require adjustments to the tune and likely shutting off the rear O2s to avoid a CEL. Or you could try using a defouler and see how that goes.
I have the tune adjusted for the removed cats and test pipes in their place. This Jegs delete kit would work great but to be able to put the cats back on the car for NC emissions test, I had to modify the piping after the cats. In stock trim, there was another 3 feet of pipe after the cats before you came to another connection joint. I had a muffler shop use a ball flange kit to make a connection point about 6 inches after the cats so I don't have to remove 4 feet of cats/pipe to remove the converters. In short, the cat delete kit would not fit so I have to have one fabricated.
BAS433 is offline   Reply With Quote
Old 07-30-2013, 09:51 AM   #15
Registered Member
Regular
 
Join Date: Dec 2011
Region: Canada
Posts: 2,976
???I don't geddit....the test pipes from Jegs just bolt to the manifolds and the factory H, right? So what's the big deal putting the cats back in? Why would they need to be modified at all?

http://www.jegs.com/InstallationInst...0580_30581.pdf
5LHO is offline   Reply With Quote
Old 07-30-2013, 10:27 AM   #16
Registered Member
Regular
 
ddinn25's Avatar
 
Join Date: Jul 2013
Location: Lebanon
Region: Ohio
Posts: 164
I used either a crayon or grease marking pen. Not sure "what temp" pen it was?
__________________
2013 5.0 m6 base 3.31's tint 20in Shelby razors 255/35/20 falken fk 452's koni srt.t's sr springs j&m phb gt500 mounts upr rear billet lower ca's upr brackets upr adjustable upper ca flowmaster at classics steeda cat deletes airaid cai premium st brace jlt catch can MGW shifter and blk ball. Currently bama tuned 400hp 383tq. Zex blackout kit w/msd digital window switch, fpss, zex bottle heater, bottle opener, blow down, and purge with a dyno tune coming soon..
ddinn25 is offline   Reply With Quote
Old 07-30-2013, 10:36 AM   #17
Registered Member
Regular
 
Join Date: Dec 2011
Region: Canada
Posts: 2,976
You can use cheap spray paint as well. Where it stops burning off, that's roughly your collector length. Drive the car the way it is intended to be driven for this.

However, this is really unnecessary since lots of others have done a lot of thinking for us on this platform. Do a little research and follow the path others have blazed. There are people running 8,9 second quarters on these cars with full exhaust.
5LHO is offline   Reply With Quote
Old 07-30-2013, 10:45 AM   #18
Registered Member
Regular
 
ddinn25's Avatar
 
Join Date: Jul 2013
Location: Lebanon
Region: Ohio
Posts: 164
Should have just installed the cat delete pipes then had the cut outs welded in the mid pipe and called it a day. If the size of the stock mid pipe is of concern then buy a ford racing mid pipe which bolts up to the stock cat or deleted pipes. It's 2.75in dia. The weld the cut out to the mid pipe. This way you can swap out the cat pipes for e-check. There are shorty headers on the market that are better than stock too. If e-check is a concern then that's what I would do

---------- Post added at 11:45 AM ---------- Previous post was at 11:44 AM ----------

5LHO: AGREED!
__________________
2013 5.0 m6 base 3.31's tint 20in Shelby razors 255/35/20 falken fk 452's koni srt.t's sr springs j&m phb gt500 mounts upr rear billet lower ca's upr brackets upr adjustable upper ca flowmaster at classics steeda cat deletes airaid cai premium st brace jlt catch can MGW shifter and blk ball. Currently bama tuned 400hp 383tq. Zex blackout kit w/msd digital window switch, fpss, zex bottle heater, bottle opener, blow down, and purge with a dyno tune coming soon..
ddinn25 is offline   Reply With Quote
Old 07-30-2013, 12:03 PM   #19
Registered Member
Regular
 
Charged13's Avatar
 
Join Date: Aug 2012
Region: Texas
Posts: 64
Quote:
Originally Posted by Evil2014GT View Post

+1. Im not understanding the point of running open shorties either. As 5LHO already said, you aren't gaining nearly anything up top, and losing a ton of torque down low since you literally have no back pressure.
+1
Charged13 is offline   Reply With Quote
Reply

Lower Navigation
Go Back   Mustang Evolution > 1979-2015 Mustang GT || Tech and Talk > 2011-2014 Mustang GT

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


» Like Us On Facebook



04:17 AM


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0

MustangEvolution.com is in no way associated with or endorsed by Ford Motor Company.