mitssn

I am toying with the idea of putting mechanical or electric cutouts on my car mainly for sound. I plan on putting them just in front of the mufflers, after the stock h-pipe (that I plan in replacing in the future with an O/R Xpipe).

I have read that cutouts on this car

a. decrease HP and torque
b. increase HP but decrease torque
c. just kick *** all around

Does anyone have actual experience with cutouts on our cars? Like I say, it's mainly for sound, but if I am going to lose power, forget it!!

Thank you.

Furinox

I have them on my V6. No noticeable change in power and sounds awesome.

Videos

http://media.putfile.com/V6-mustang-with-cutouts-Reving

http://media.putfile.com/V6-Mustang-Cutouts-Launch

CrazyAl

OK, as a general rule for most cars: An open exhaust (such as when your cutouts are open) will increase HP and torque.

HP and Torque always increase (or decrease) together. This is becasue they are mathematically related. HP is simply Torque * RPM * constant. (This is why on dyno graphs the HP and torque curves always cross at 5252 rpm in American units) It is mathematically impossible for a mod--ANY MOD--to "give you HP but decrease torque" simultaneously.

(As a side note, what most people mean when they talk about engines is "low RPM torque" and "high rpm HP"..but this is not technically accurate.)

Now then back to your car. The stock mufflers on the new Stang are quiet, but they are free-flowing. They aren't costing you much, if any, HP. So, if you install cutouts and open them up, they aren't really gaining you anything except noise.

(Now then, on a DIFFERENT car where the stock mufflers are usually highly restrictive, then the cutout could give you some HP)

I would think that your HP gains would be zero. I don't think you're going to loose power either.

Furinox

added my vids for you to see. the v8 will sound a lot different though.

Menace

Your engine needs some backpressure if you're N/A, to be able to make anything. My exhaust setup right now is free floating, no cats and no mufflers. It's loud, but it only sounds good at different RPMs.. I'm hopefully fixing this shortly with some resonator's welded before the mufflers, which will give some back pressure and make the car sound a little quieter/deeper.

Sleeper05

very well described, but i disagree with gains. on many cars, and with proper placement and installation, cutouts are good for quite a bit of power. you see plenty of threads about how an offroad x-pipe got 10hp here and 15 hp there, and long tube headers reliably get that or more. those component simply make air flow through the exhaust easier. cutouts will allow the same effect, if installed close to the headers, because it lets the air escape from the exhaust system. you will possibly lose torque (and hp) down low before enough air flows to cause measuruable backpressure, but up high in the rpms you can see quite significant gains (esp with a dyno tune for using it at the track).

this is not to say that bolting them in will get you 20+hp, but with a proper track tune for them, i see no reason that could not *easily* be achieved (above and beyond a good tune for stock exhaust), even on the stock headers...which flow pretty well compared to past years. cutouts also sound awesome, did i mention that?

88BlueGT

^^^ +1

mitssn

Thanks for the input. Does anyone have sound clips of a V8 with cutouts?

CrazyAl

That is not exactly true.

Long-tube headers make HP for two reasons. First, they reduce restriction, that's true. But that is relatively minor reason-especially on our new Mustangs. The OEM manifold actually has very smooth passages and merges in it. The real reason why LT headers make a lot of HP is becasue they improve exhaust scavenging by proper timing and routing of the individual exhaust pulses. This can literally suck the intake charge into the cylinder. That's the whole point of the tubes being "long" in addition to smooth. On a flowbench, a proper set of shorty or longtube headers will flow the same amount of air. It's not just about the flow, it's about the resonance characteristics of the header--which is very complicated. It has to do with the diameter and length of the primaries, which are matched to the specifics of the engine. The headers aren't simply "long". They have a very specific length. This is why a *REAL* set of race headers, such as Burns Stainless, etc, require you to fill out a very long form listing all your engine, cam, and ignition timing specs before they make you a set of headers.

The reason why Off-road exhaust pipes give you HP is becasue they eliminate a major restriction--the stock Cats.

If you are putting Cutouts on an otherwise stock car in the location that mitssn described, the ONLY thing that cutout will be bypassing is the stock muffler. We already know that the stock muffler is not appreciably restrictive. That's why I said that the HP gains would be minimal--in this location the cutout isn't bypassing anything.

Now then, let's say you put the cutouts before the cats (keep in mind, this is NOT what mitssn asked--and there's not enough room) THEN you'd be bypassing the restrictive stock cats, and we'd be talking about a good drop in backpressure, and a HP gain. However, this situation is also complex. On these cars you have to tune in order to get the most out of your gains. If you have a "Stock tune" and then open your cutouts, you won't be seeing most of the possible gain becasue the tune isn't right. Or, if you tuned for the cutouts, then your tune would be wrong when you had 'em closed and were just driving around town. Perhaps you could bring your tuner and only fool with the cutouts when you were at the track and had time to retune before and after leaving the strip...but IMHO that is much more of a pain than it is worth. The cost of cutouts would be much better spent on, say, drag tires.

Furinox

the cost of cutouts are $22 ea.

That is not going to get you anywhere close to the cost of drag tires.