Exhaust system question

[RP-CLMBR]

Thanks for that link rh77 I looked over my exhaust sestem today and it has the stock hf small manifold cast iorn then fact cat then is where they went t 2 1/4 " stainless my 87 looks like 1" mabe 1 1/4 " like a go cart I think at first I am going to ex perment by changing to a smaller tip and see where my 1700 rpm power goes I like the artical but it failed to mention the aspect of the re ingestion of nox during valve over lap to cool or stabalize the burn on the older FE engines I think that my head temp is probably to hot do to the small to large the exhaust is probably stagnating I wonder what size oem was
may just run a staight pipe that could be my tattle when I am suffering from size 11d disease,Thanks Paul

[99clipsgst]

I know that on my eclipse when I got rid of my cat and put a 2.5" downpipe to a 3" cat back system I gained about 1.5 mpg.

[whokilledthejams]

In general, OEM exhausts are optimal. Less restrictive systems open up some high end power, but at the expense of low-end driveability, so unless you always shift at 5k and drive like a retard, such a thing doesn't do you any good.

In the GMC Sonoma (S10 clone) I used to have, I had an ongoing fight with the exhaust system, and concluded that I needed it to be intact not only to be quiet, but to preserve my already-meager low-end torque. If low-RPM power is missing, you are forced to shift later, thus killing your FE and ability to drive sensibly.

[wagonman76]

I tried a Magnaflow glasspack on my 6000 wagon once. First it was way too loud, second I lost my low end torque. The only way to keep up the torque in OD was to get on the freeway and go 70. Later on I changed it for a Holley Flowtech 304 turbo style muffler, which was much better. Both that and the Celeb have an aftermarket cat, Holley Flowtech 304, and 2 1/4" pipe all the way back which is stock size but mandrel bent, everything is 304 stainless. Both perform great and Ive got a lot of low end torque. Also saved money in the long run since I havent had to dink with either exhaust since, its been many years.

[RH77]

Back in '97, I put a "MagnaFlow" muffler on a base '97 Civic DX coupe. It wasn't much louder, and starting off required considerably more throttle. Torque suffered.

In a snowstorm, an "off-road" snow event ripped the seam in the muffler (it could have been snow on a hot muffler = rapid expansion/contraction and split). It sounded like an '83 Omni with a straight-pipe.

I kept the stock muffler and had it re-installed. Immediately, I noticed better, low-speed driveability. My Mom drove the car and independently mentioned that the car had a "LOT more power" and it immediately "went when you hit the gas". This essentially was a single-blind test, since she didn't know the muffler was replaced to stock.

I don't hold much faith in the "butt-dyno", but in this case, it was noticeably measureable.

Muffler choice, in this case, effected performance dramatically.

RH77

[RH77]

Originally Posted by BlackDeuceCoupe

Nice mileage on that Teg, bud!

I got Teg floormats...

Speaking of great mileage, look at yours! Great work. The floormats likely add at least 5 MPG

I once had a Black '99 Si Coupe -- honesly the best car I've owned. Not nearly the FE, though. The 'Teg would easily beat it in the vehicle history, if it was a 5-speed. The slushbox makes it a challenge.

40 from a B16A2. Good stuff.

RH77

[kdmy0]

Here is my setup in my car. (it has helped mpg)

4-2-1 Header (good for low-end power)
2.5" Exhaust (good for hi-end power)
Magnaflow Hi-Flow Cat.

It ended up being a very good combo. Tool'n around town it is nice because Ill have decent power under the power curve. And if I ever need to surpass 3k, Ill have power up there too. It has been actually very friendly to my gas tank!

[Ferr3t]

Okay, I have a similar question to the OP. What if you were to replace the OEM piping with the same size piping, but mandrel bent instead of crush bent, then had a free flowing muffler to top it off. Wouldn't your pulse width be the same, just able to move out of the exhaust more easily?

[malibuguy]

basically, a stock exhaust is good for typical hypermilers, since most don't pull much RPM & load

now you can gain mileage with an exhaust if your normally putting a big load on the engine & pulling alot of rpm all the time

it really depends on the vehicle, how its used, etc

our mandrel bent exhausts are typically lighter then most stock exhausts, our stainless is .055" wall & our aluminized is .065 wall (16 gauge), typical muffler shop crush bent crap is 14 gauge...which is much heavier, & the crush bends alone kill exhaust gas pulse energy by constricting them down into a small area (crush bend) then expelling back out in a bigger area thru multiple bends just kills the momentum of the exhaust gas pulse

i can go on on with my ideas/theories, especially since i'm obsessed with exhausts & do i do high-end, mandrel-bent exhaust work for a living, basically that exhaust basics link on that integra site is just about right

check out our site, most of the pics in the gallery are of my work
www.mandrelbend.com

[Ryland]

I don't under stand why people think small piping is restrictive, your exhaust is not a steady flow, it is pulses and if you have a larger pipe it is going to take longer for those pulses to reach the end, it's not the same math you use for pluming water in a house, it is the same math as you use for musical interments, if you wanted a true free flowing non restrictive exhaust you would remove the piping all together, but if you do that your engine will hardly run!
It's still bitterly cold out but after replacing my exhaust with oem honda pipe my torque went up (the feel of more power) and my gas mileage went up, I will not have a clear reading on this untill I can compare the last 2-3 years of running a larger pipe, and the size might not seem that drastic going from a 2" down to a 1 3/4 but check out the volume of the two, BIG difference.