Cutouts, headers and backpressure- what's the scoop?
#1
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Cutouts, headers and backpressure- what's the scoop?
All-
So I'm no engineer, but I'm curious to find out the answer:
If one were to run a 4.6 3V mod motor with long tubes and electric exhaust cutouts, would there be an issue with backpressure loss? Would a supercharger complicate issues (as it needs pressure to build power)? I know a TON of backpressure isn't good, but I also know that too little can cause power loss.
Thanks in advance-
Jim
So I'm no engineer, but I'm curious to find out the answer:
If one were to run a 4.6 3V mod motor with long tubes and electric exhaust cutouts, would there be an issue with backpressure loss? Would a supercharger complicate issues (as it needs pressure to build power)? I know a TON of backpressure isn't good, but I also know that too little can cause power loss.
Thanks in advance-
Jim
#2
open headers, or cutouts will not hurt your power. superchargers need pressure to build power but they build this pressure in the manifold. A cam with a great deal of overlap (both intake and exhaust valves being open simultaneously for a short time) will hurt boost by allowing the boost to blow through. But long tubes and reducing restriction in the exhaust will only help make more power. I have heard of backpressure helping low end torque, but in a racing application you are not looking for torque at 1500 rpm since you will usually be launching at higher rpms than that and staying in the powerband. Think of the motor like a big air pump. the more air you pump, the more power you make (as long as you can mix that air with the right amount of fuel, and make it blow up real good). reducing restriction in the intake, and exhaust path are the most basic ways of finding hidden power in your motor.
#3
I agree with Faber to a point: If you are racing and at high rpms the backpressure probably isn't needed, but simply eliminating it [say you go with open headers], you will definitely lose low end torque. For myself, my car is a daily driver so the low end is really needed for my style of driving.
Just my opinion.
Mike E
Just my opinion.
Mike E
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Ok- well I thought doing a set of electric cutouts after long tubes would be the way to go to put together a good street/strip car without buying a full exhaust.
How is that WMS CAI treating you? I have had my eye on that unit for some time, and it looks like it could be better than other CAI's, just a little more difficult (and not to mention pricier) to install.
Mr. Bell's little pressure box is looking like the best bet for some decent power, w/o having to beef up the bottom end...
-Jim
How is that WMS CAI treating you? I have had my eye on that unit for some time, and it looks like it could be better than other CAI's, just a little more difficult (and not to mention pricier) to install.
Mr. Bell's little pressure box is looking like the best bet for some decent power, w/o having to beef up the bottom end...
-Jim
#9
#10
Ok- How is that WMS CAI treating you? I have had my eye on that unit for some time, and it looks like it could be better than other CAI's, just a little more difficult (and not to mention pricier) to install.
Mr. Bell's little pressure box is looking like the best bet for some decent power, w/o having to beef up the bottom end...
-Jim
Mr. Bell's little pressure box is looking like the best bet for some decent power, w/o having to beef up the bottom end...
-Jim
Mike E
#11
I've tested my car with full exhaust, open exhaust and with bullets attached to my longtubes and i found my car doesn't run any quicker or slower. it just sounds louder and dropping the exhaust lost me about 75lbs. I'll probably try it again after I build the new engine just to see if it makes a difference then but I doubt it will be substantial.
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Essentially, a little pipe with a door activated by a switch in the cabin. Once the switch is flipped, the door opens and the exhaust comes straight out the headers instead of going out the rear.
I'll look for an image here shortly.
Here you go: http://www.lmperformance.com/2899/73.html
I'll look for an image here shortly.
Here you go: http://www.lmperformance.com/2899/73.html
#14
Electric cutouts are devices that are installed to "cut out" your mufflers and over axle pipes and let the exhaust out right at the end of the headers. If you run a restrictive exhaust for the street and want to run open on weekends without the hassle of having to remove all those components then cutouts are what you will be looking for. electric ones take it a step further and let you do it at the push of a button (like at a stoplight when you need to drown out a fart can muffled dirt bike engined ricer)
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Electric cutouts are devices that are installed to "cut out" your mufflers and over axle pipes and let the exhaust out right at the end of the headers. If you run a restrictive exhaust for the street and want to run open on weekends without the hassle of having to remove all those components then cutouts are what you will be looking for. electric ones take it a step further and let you do it at the push of a button (like at a stoplight when you need to drown out a fart can muffled dirt bike engined ricer)
#17
When I had my 01 Stang I had a magnaflow X pipe and cat back and my number were 260hp / 302tq NA (IIRC). I then put on BBK LT headers with X pipe w/cats. My numbers didnt change but +/- 1 hp/tq but it accelerated faster with the lower back pressure and the better flowing of the LT headers. So I wouldnt worry about the back pressure.
#18
How it works...
http://www.speedunlimited.com/cgi-bi...l?p_catid=3904
http://www.quicktimeperformance.com/QTEC/index.php
http://www.pypesexhaust.com/accessories.html (life time warranty)
http://www.racereadyperformance.com/ (life time warranty)
http://www.speedunlimited.com/cgi-bi...l?p_catid=3904
http://www.quicktimeperformance.com/QTEC/index.php
http://www.pypesexhaust.com/accessories.html (life time warranty)
http://www.racereadyperformance.com/ (life time warranty)
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