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

 

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.

 

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

 

PS I forgot to add that I have a CAI from WMS with a Brenspeed tune to take advantage on the stock exhaust...

 

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

 

I am installing electric cutouts at the ends of my longtubes simply for scaring ricers.

 

 

I have the Electric cut outs and they rock!!! Scares the cr@p out of ricers...car sounds real nice too when you start it and when you down shift.

 

which ones do you have? where did you install them at? any problems with exhaust leakage?

 

I like the WMS and it wasn't that hard to install, but to each his own. personally, I think the tune makes the biggest difference, but the air filter being larger and a little more direct [shorter inlet pipe] can't hurt either. I have the "ram air plate" too, so it has some vents to front edge of the hood. This is all covered in some posts a while back along with pics of the install.
Mike E

 

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.

 

What are electric cutouts??

 

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

 

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)

 

The force is strong with this one.

 

Yes. Do or do not. there is no try.

 

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.

 

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)

 

Do they still work with lets says JBA LT's and H-Pipe? How much does an install run for. These look AWESOME!

 

I couldn't really tell you, but I have a feeling some cutting and welding is required.

Hopefully somebody will clarify.