Do dumps give you more horesepower?
- Thread starter Pokageek
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earleys94gt
Active Member
HP, I don't know, but I would guess it would affect torque somewhat.
In the same way an "x" pipe 'favors' high rpm, where as an "h" 'favors' low rpm.
In the same way an "x" pipe 'favors' high rpm, where as an "h" 'favors' low rpm.
hollywoodstang
Active Member
- May 23, 2006
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I read an exhaust tuning article a good while back where they tested various lengths of exhaust. They picked up 2-5hp with tailpipes, but made 14-15lb.ft more torque with dumps.
I don't remember what car this was, or if it was an engine or chassis dyno. I'll see if I can find that article again when I get time.
I don't remember what car this was, or if it was an engine or chassis dyno. I'll see if I can find that article again when I get time.
zenboy99
Founding Member
Totally depends on the application. Pretty much all the NMRA racers are running something similar to dumps, except those classes that have to have the exhaust exit past the axle like Pure Street.
95Vert
New Member
And what proof might you have of this.
I once asked the same question and the answer I got was,
Jay Allen; said:
Same applies for length of exhaust.
blksn955.o
Founding Member
I do not know about power but they give me headaches....too much drone and echo in the car for me. Unless they give you 40+rwhp not worth it IMHO...plus our cars and LX/Notch fox's look 100x's better with some nice chrome/SS tips out back.
95Vert
New Member
Yeah, I get what you mean. I love my dumps though. Maybe when I get older, I'll install my side exhaust Borlas and be done with it, but for now, I'll have a loud mofo.
I would say in a basically stock, or modest bolt on Mustang, there will be little to no horsepower/torque gain from dumping the exhaust in front of the axle. At least nothing that'll make itself apparent in "real world" testing. The few horsepower you may, or may not gain up top, will probably show an equal amount of torque loss down lower in the bottom end regions of the power band.
If you're moving a lot of air through the engine via some sort of power adder or large displacement bump (which you are) and are reaching the flow limits of the average 2 1/2" diameter aftermarket exhaust system, then yes probably a fair amount of power at the mid to upper end of the power band could be picked up.
Not only are your reducing the exhaust length by cutting it short, but you’re also reducing the turbulence of the system by taking a 180* bend out the tubing and out of the pathway of the exhaust, thus further reducing backpressure.
If you're moving a lot of air through the engine via some sort of power adder or large displacement bump (which you are) and are reaching the flow limits of the average 2 1/2" diameter aftermarket exhaust system, then yes probably a fair amount of power at the mid to upper end of the power band could be picked up.
Not only are your reducing the exhaust length by cutting it short, but you’re also reducing the turbulence of the system by taking a 180* bend out the tubing and out of the pathway of the exhaust, thus further reducing backpressure.
DDSTANG94
New Member
ya but its not a a race car... how often do race cars drive on the street where tq counts...race cars see 4000 rpms and up, they dont need or USE low end torque
I had them on my car and it felt a little softer down low, but i couldn't tell a difference up top, maybe a little stronger
I think it really depends on the application like stated above
My car is nasty loud at stop lights but it is quiet driving. I had to cut the tailpipes to get the panhard bar on. I intend to put them back on.
BaBysARM
Founding Member
both my cars have dumps. If i wasnt such a tight wad then i would surely have tailpipes. In stock form you are probably going to lose power due to loss of backpressure. My opinion would be keep the tail pipes!!
95Vert
New Member
DDSTANG94
New Member
So you're saying we NEED backpressure?Can you explain why?
the back pressure makes the cylinders fill up with air faster
95Vert
New Member
More back pressure will cause more heat and create more detonation. Like someone told me, try sticking a potato in your exhaust to see what backpressure does.
So you're saying we NEED backpressure?
Reduced backpressure is fine, but there are drawbacks to reducing it as well....especially if you go overboard.
More back pressure will cause more heat and create more detonation. Like someone told me, try sticking a potato in your exhaust to see what backpressure does.
It's true, backpressure will contribute to raised cylinder and exhaust temps, but that's not necessarily a bad thing. A hotter exhaust will aid with scavenging thus improving torque production at lower RPM levels. This will also help to maintain in town fuel economy, that would be reduced otherwise. Not to mention that added heat will provide you with over all cleaner emissions.
There's a reason most factory Mustangs only came with a 2 1/4" exhaust. Although there is a performance benefit to increasing exhaust diameter on a deeper breathing configuration that warrants its use (more cubes, power adder, freer breathing heads/intake), there are trade off's to having a larger, or freer breathing exhaust system when it's not warranted , as I mentioned above.
Very true, scavaging will be greatly reduced.... You would be surprised how much HP can be made with 2.25" exhaust.
DDSTANG94
New Member
More back pressure will cause more heat and create more detonation. Like someone told me, try sticking a potato in your exhaust to see what backpressure does.
..that's ONE of the two reasons headers are offered in ceramic
1 reason- looks and durability
1 reason- traps in the heat and and speeds the exhaust gasses up
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