Is there really power loss with LMs?
10-12-2006, 03:22 PM
#11
1st Gear Member
Thread Starter
Join Date: Mar 2006
Posts: 117
RE: Is there really power loss with LMs?
ORIGINAL: bl1nkage
There is a huge thread about this from a couple months ago where a few of the forums best car guys (who also happen to be engineers in one thing or another) say that backpressure isnt good and that straight pipes will almost always provide -more- power than chambered systems by allowing the exhaust to flow more freely, providing that the pipes dont get too large because then it will slow down the exit velocity. In other words, straighter, appropriately sized pipes, with less obstacles blocking the exiting of the exhaust fumes are optimal.
Personally I dont believe any axle backs will cause you to lose power, but at the same time it wont cause you to gain power either (under normal N/A conditions.) On a blown system it will certainly be a larger factor to have a more freely flowing exhaust setup.
There is a huge thread about this from a couple months ago where a few of the forums best car guys (who also happen to be engineers in one thing or another) say that backpressure isnt good and that straight pipes will almost always provide -more- power than chambered systems by allowing the exhaust to flow more freely, providing that the pipes dont get too large because then it will slow down the exit velocity. In other words, straighter, appropriately sized pipes, with less obstacles blocking the exiting of the exhaust fumes are optimal.
Personally I dont believe any axle backs will cause you to lose power, but at the same time it wont cause you to gain power either (under normal N/A conditions.) On a blown system it will certainly be a larger factor to have a more freely flowing exhaust setup.
10-13-2006, 08:30 AM
#13
3rd Gear Member
Join Date: Aug 2006
Location: North East Texas on the Red River
Posts: 886
RE: Is there really power loss with LMs?
In an MAF Fuel Injection car, any flow improvement or loss is automatically compensated for. Anyone who believes that improving exhaust flow will lose horsepower is probably an old school guy that put headers on his carbureted car without recalibrating the carburetor and indeed lost power. He lost the power because the headers leaned it out and he did not compensate for that.
In the case of our Mass Air Flow injection system, improved exhaust flow will be measured by the MAF and compensated for. NOW, that said, at wide open throttle you are running in open loop mode where the MAF and O2 measurement may not come into play, so a different tune will be necessary for your wide open throttle operation.
You don't get something for nothing.
In the case of our Mass Air Flow injection system, improved exhaust flow will be measured by the MAF and compensated for. NOW, that said, at wide open throttle you are running in open loop mode where the MAF and O2 measurement may not come into play, so a different tune will be necessary for your wide open throttle operation.
You don't get something for nothing.
10-22-2006, 10:26 PM
#14
Join Date: Oct 2006
Posts: 1
RE: Is there really power loss with LMs?
Now I just installed Borla Axle Backs and I noticed a major decrease in power. I could smell something burning in the drivers side muffler. I put the OEM muff's back on and everything was fine. Thinking that something was wrong with the Borla muffs, I bought some Bassani Axle Backs... Same damn thing... Bogging...and burning smell...
The only other MOD I have is a GMS CAI w/MAF.
Anyone have this problem?
[IMG]local://upfiles/52246/AD8F2A350AA74B27A3807655C0A84F4C.jpg[/IMG]
The only other MOD I have is a GMS CAI w/MAF.
Anyone have this problem?
[IMG]local://upfiles/52246/AD8F2A350AA74B27A3807655C0A84F4C.jpg[/IMG]
10-22-2006, 11:13 PM
#15
RE: Is there really power loss with LMs?
Backpreasure is bad, however, once you loose a certain velocity that the gases are flowing out then you loose power, the reason people think that you loose power is cause you gain HP, which is the top end, so your off the line stays the same but pulls harder up top, i have never witnessed a car loose power cause of a freeer flowing exhaust
10-23-2006, 12:01 AM
#16
1st Gear Member
Join Date: Sep 2006
Posts: 60
RE: Is there really power loss with LMs?
IMO they cant loose hp. Backpressure effects all engines differently. For example in a 3.0 v6 that they put in rangers, the headers and exhaust modifications are pretty much pointless because those engines are built to get their torque from the backpressure. But anyway there is no way that an axleback can cause a 4-7 hp loss. I would have to see the dyno done in person for me to believe it.
10-30-2006, 03:59 PM
#17
3rd Gear Member
Join Date: Feb 2006
Location: Florida
Posts: 716
RE: Is there really power loss with LMs?
From a member on THEMUSTANGSOURCE.COM:
Im looking at the issue of MM&FF where they do the Sn197 GT Exhaust Shoot-Out [In NO particular order...] This shows the loss of power by running no mufflers (SLP Loudmouth)
Stock Mufflers Made-289.9rwhp & 313rwtq...16 lbs each...Idle Noise 68dba...Cruise 2Krpm: 96 dBa
Bassani Race AB Made- 292.7rwhp & 314.rwtq...7.5lbs each...Idle Noise 71 dBa...Cruise 2Krpm: 98 dBa
Flowmaster AB Made-292rwhp & 314.5rwtq...16lbs each...Idle Noise 72 dBa...Cruise 2Krpm: 97 dBa
FRPP Stinger AB Made-292.7rwhp & 314.9rwtq...7.5lbs each...Idle Noise 71 dBa...Cruise 2Krpm:96 dBa
UnMuffled (SLP Loudmouth)-290rwhp & 311.2rwtq...0 lbs...Idle: 73dBa...Cruise 2Krpm:99 dBa
JBA AxleBack-289.5rearwhp & 313rearwheeltq...11 lbs each...Idle: 71dBa...Cruise 2Krpm: 98dBa
Magnaflow AB -290.2rwhp & 311.8rwtq...14lbs each...Idle: 66dBa...Cruise 2Krpm:98 dBa
(NOT Magnapacks
And if anyone would like to disagree with any of the info...I will be happy to scan the entire article up to prove you wrong
Stock Mufflers Made-289.9rwhp & 313rwtq...16 lbs each...Idle Noise 68dba...Cruise 2Krpm: 96 dBa
Bassani Race AB Made- 292.7rwhp & 314.rwtq...7.5lbs each...Idle Noise 71 dBa...Cruise 2Krpm: 98 dBa
Flowmaster AB Made-292rwhp & 314.5rwtq...16lbs each...Idle Noise 72 dBa...Cruise 2Krpm: 97 dBa
FRPP Stinger AB Made-292.7rwhp & 314.9rwtq...7.5lbs each...Idle Noise 71 dBa...Cruise 2Krpm:96 dBa
UnMuffled (SLP Loudmouth)-290rwhp & 311.2rwtq...0 lbs...Idle: 73dBa...Cruise 2Krpm:99 dBa
JBA AxleBack-289.5rearwhp & 313rearwheeltq...11 lbs each...Idle: 71dBa...Cruise 2Krpm: 98dBa
Magnaflow AB -290.2rwhp & 311.8rwtq...14lbs each...Idle: 66dBa...Cruise 2Krpm:98 dBa
(NOT Magnapacks
And if anyone would like to disagree with any of the info...I will be happy to scan the entire article up to prove you wrong
10-30-2006, 05:07 PM
#18
2nd Gear Member
Join Date: Jul 2006
Location:
Posts: 355
RE: Is there really power loss with LMs?
ORIGINAL: 555*
From a member on THEMUSTANGSOURCE.COM:
From a member on THEMUSTANGSOURCE.COM:
Im looking at the issue of MM&FF where they do the Sn197 GT Exhaust Shoot-Out [In NO particular order...] This shows the loss of power by running no mufflers (SLP Loudmouth)
Stock Mufflers Made-289.9rwhp & 313rwtq...16 lbs each...Idle Noise 68dba...Cruise 2Krpm: 96 dBa
Bassani Race AB Made- 292.7rwhp & 314.rwtq...7.5lbs each...Idle Noise 71 dBa...Cruise 2Krpm: 98 dBa
Flowmaster AB Made-292rwhp & 314.5rwtq...16lbs each...Idle Noise 72 dBa...Cruise 2Krpm: 97 dBa
FRPP Stinger AB Made-292.7rwhp & 314.9rwtq...7.5lbs each...Idle Noise 71 dBa...Cruise 2Krpm:96 dBa
UnMuffled (SLP Loudmouth)-290rwhp & 311.2rwtq...0 lbs...Idle: 73dBa...Cruise 2Krpm:99 dBa
JBA AxleBack-289.5rearwhp & 313rearwheeltq...11 lbs each...Idle: 71dBa...Cruise 2Krpm: 98dBa
Magnaflow AB -290.2rwhp & 311.8rwtq...14lbs each...Idle: 66dBa...Cruise 2Krpm:98 dBa
(NOT Magnapacks
And if anyone would like to disagree with any of the info...I will be happy to scan the entire article up to prove you wrong
Stock Mufflers Made-289.9rwhp & 313rwtq...16 lbs each...Idle Noise 68dba...Cruise 2Krpm: 96 dBa
Bassani Race AB Made- 292.7rwhp & 314.rwtq...7.5lbs each...Idle Noise 71 dBa...Cruise 2Krpm: 98 dBa
Flowmaster AB Made-292rwhp & 314.5rwtq...16lbs each...Idle Noise 72 dBa...Cruise 2Krpm: 97 dBa
FRPP Stinger AB Made-292.7rwhp & 314.9rwtq...7.5lbs each...Idle Noise 71 dBa...Cruise 2Krpm:96 dBa
UnMuffled (SLP Loudmouth)-290rwhp & 311.2rwtq...0 lbs...Idle: 73dBa...Cruise 2Krpm:99 dBa
JBA AxleBack-289.5rearwhp & 313rearwheeltq...11 lbs each...Idle: 71dBa...Cruise 2Krpm: 98dBa
Magnaflow AB -290.2rwhp & 311.8rwtq...14lbs each...Idle: 66dBa...Cruise 2Krpm:98 dBa
(NOT Magnapacks
And if anyone would like to disagree with any of the info...I will be happy to scan the entire article up to prove you wrong
10-30-2006, 05:17 PM
#19
3rd Gear Member
Join Date: Feb 2006
Location: Florida
Posts: 716
RE: Is there really power loss with LMs?
Pretty much. I'm curious what the dyno graph actually looks like though. Is there more hp in some areas of the RPM rangs vs lower in other areas compared to stock? *still waits for a graph*
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