150$ summit racing exhaust

[maclgallant]

http://www.summitracing.com/parts/SUM-680032/

what do you guy's think?
anyone have experience with summit racing exhaust?

 

[snoranger]

IIRC, Summit sells reboxed IMCO exhausts.

 

[maclgallant]

i noticed that the exhaust uses 3" tubing... would that be too much? has anyone ran 3" piping on the 4.0?

 

[maclgallant]

from what i read on the forums 3" piping seems to be too much on a 4.0, can anyone with experience with them confirm it?

 

[alwaysFlOoReD]

No experience here, but everything I've read from sources I trust say the engine is an air pump. So any restrictions you can remove is a good thing. That said, if you aren't racing, a cheaper system would probably be sufficient.

Richard

 

[a31ford]

Engines Being the "air Pumps" that they are (Fact), "Tuned pipes" (intake, tunnel rams, 2 cycle exhaust, headers, old bellows church organ, etc. etc. etc.)

The resonate frequency of a "standing wave" can be used to enhance or detract from the resonate frequency of a length of pipe. (singing in the shower is a good example of the resonant points of the shower enclosure and the steel tub).

With all that said, the larger the pipe (and longer) the lower the resonate frequency of it. So, if you are looking to simply empty the exhaust from the engine, and you are NOT worrying about headers and such, Bigger IS better, the trade off to this is that the O2 sensor might read lean because of the lack of some back pressure, and waste gas because of this.

CB radios use "SWR" to tell if the antenna is tuned correctly SWR, Standing Wave Ratio, higher frequency, BUT exact same resonate frequency stuff.......

 

[alwaysFlOoReD]

@a31ford;
Sounds like you know much more about this stuff than I do. I hadn't considered the o2 when wrote last time but my feeling is that the cat would provide sufficient back-pressure [shielding the o2] using the OP's exhaust system linked above. My point was that he could probably achieve equal results using cheaper components if he isn't racing.
Many years ago I did some research for building my own ram air intake [carbed] and headers tuned to specific rpm. I also looked into turbo charging...all this this was 30 years ago tho. I've forgotten most of it....
I'm still into learning and glad you responded.
Cheers,

Richard

 

[GoGoggansGo]

from what i read on the forums 3" piping seems to be too much on a 4.0, can anyone with experience with them confirm it?

2.5 seems to be the sweet spot

 

[a31ford]

If it's dual 2.5 how long ? (total length behind catalytic ?)

Here, I'll give you an example:

2.5" divide by 2, equals 1.25 times 1.25 times 3.1415 equals 4.908 square inches for every foot of pipe (one pipe) there are 4.908 times 12 equals 58.904 cubic inches.

Therefore, if the exhaust was roughly 5 feet long, there would be 58.904 times 5 equals 294.524 cubic inches. a normal "sub box" for say a sony explod 10" speaker is about a cubic foot, and is tuned to about 160 hz. a cubic foot is 12 times 12 times 12 equals 1728 cubic inches. So, 1728 divided by 294.524 is 5.86 times that of 160 hz. (we now move into "octaves" and the roughly 6th octave of 160hz. is.... 160,320, 640, 1280, 2560, 5120 there abouts or so). #A (standard pitch) on a piano is 440hz), the last white in the 5th set of three blacks, starting from the left, so the resonate note of your 5 foot tailpipe is the last white on a keyboard (to the right) and 5 keys MORE (last right white is 4180 hz).

The pipe will resonate "loudly" on the following notes:

1318 (68th key)
659, (56th key)
329, (44th key)

and quietly on the following:

82, 20th key
and 41, 8th key

(count the keys starting from the left as being 1 and 88 on the far right)

So, knowing the resonate points, we can derive the rpm's that it will "sing" at....

Idle is about 850 give or take rpm, a 4.0L is a v6, so 850 divided by 2= 425 (4 cycle so there are only have the amount of firings for a given rpm).

Going off the cuff at this point, 980, 2200, 3300, 4400 are the sweet spots.

2200 is the engines torque peak, so this is where it will actually gain some from a single 2.5" ID exhaust pipe,

Even if you go duels, the 980 to 2200 rpm point will benefit. but it will sing sweet at 2200 rpm, and sound "gutsy" at 1100.

Greg