109 replies to this topic

[Simply Volvo]

Hello everyone!

Well im not really sure if this belongs, in cosmetic, Maintenance or here, but i decided here would be my best bet.

So im looking to maybe do an exhaust on my NA. I am by no means looking for performance. Let me say that again, i am not looking for performance. I know i cant gain 10000hp with an exhaust on an NA. Basically im just looking for a better sound. Instead of gaining performance id like to maintain the power i currently have but achieve a nice tone.

So lets start off with back pressure. What is the hype with back pressure and these NA engines. Ive read all over the forums that these engines love back pressure and require it to make torque. All over the web i've read that back pressure is a hype and a myth and it is better to have less back pressure. Does anyone have any first person experience with back pressure and these engines? Hoping i can get a little more info.

Basically I was thinking of just taking out the muffler and replacing it with regular old pipe. This will definitely get me that 5 cyl NA sound, but it might be obnoxiously too loud. Aftermarket muffler suggestions? It will also free up the exhaust and decrease back pressure. How will this affect my engine? This is how i think of it. Basically the less backpressure, the more free flowing exhaust. If i were to purchase a cam timing tool and set a little more overlap, the intake and exhaust would be open at the same time and this would effectively charge the cylinder. Less resistance in exhaust, more cylinder charging. Correct me if i am wrong. So hmm performance and sound? Somethings sound a little fishy. What have other people done? Hopefully Johann can chip in.

Next, i am looking for exhaust pipe sizes.

I have been able to figure out that the pipe going from the cat all the way back is 1.75in. What is the size going into to cat? Is the whole system 1.75?

Hope i can get some help here or some ideas.

Many thanks!

~Simply

[Deimos]

There is no reason for an engine to have backpressure, unless it's a side effect of effective scavenging. I went to 2.25" from the cat all the way back with a single borla muffler in the rear. Kinda wish I had gone for a second muffler, gets a bit loud.

[Simply Volvo]

Did you cut the weird ball joint clamp off the cat? Also what size pipe is the pipe coming out of the cat?

[Deimos]

Did you cut the weird ball joint clamp off the cat? Also what size pipe is the pipe coming out of the cat?

I didn't touch any up to the cat, and have 2 1/4" from the cat to the back.

And yes, it's welded to the cat, I cut off that silly thing.

[Simply Volvo]

I didn't touch any up to the cat, and have 2 1/4" from the cat to the back.

And yes, it's welded to the cat, I cut off that silly thing.

Still a little confused, so you kept the stock cat in place.. but what did you do with the weird ball joint that connects the end of the cat to the rest of the exhaust? Did you cut it off(the ball joint) and weld 2.25" pipe?

Ok nevermind you answered my question in your edit.

Thanks!

Is the pipe coming from the cat 2.25in?

[IkeaBox]

I've heard in many places that some back pressure helps torque down low in normally aspirated engines and that not enough back pressure can lead to burning valves. Don't quote me on that, just thought I'd put it out there if you want to look into it some more. That being said, my s70 t5 sounds gnarly with just straight pipe cat back so if you want to do it go for it. The NA will probably sound a little different as its a higher compression engine but still not bad. Just be aware that the sound will be fairly loud and raw and not pleasant when hungover. I get some drone around 2200-2500 rpm on the highway but I've learned to ignore it. Other than that I just hope you drive a manual, and don't forget to clutch in when you pass by cops

[Deimos]

This explains it rather well...

http://www.carforum....k-pressure.html

And yes, I have a 2.25" pipe from the cat to the muffler.

The N/A is ridiculously load with a straight pipe.

[Simply Volvo]

This explains it rather well...

http://www.carforum....k-pressure.html

And yes, I have a 2.25" pipe from the cat to the muffler.

The N/A is ridiculously load with a straight pipe.

So is the stock exhaust 1.75in? Or 2.25in? Just want to clear this up. Is the cat pipe 2.25in or 1.75in

[Deimos]

Do you mean from the engine to the cat? I don't remember... I made this exhaust like 5 years ago. I think the pipe into the cat was wider than the pipe out originally... but I'm not sure. Best you measure it all.

[Eliotg]

I made an ss exhaust for my NA. I did 2-1/2" from the header back. Im running the obx ss header. Originally I used a Magnaflow highflow cat, a 14" oval body Magnaflow in the stock spot and a pypes m80 by the fuel tank. I adjusted my cam timing with the ipd tool. Now running a dynomax vt in place in of the magnaflow. Quieted it dow n a bit and reduced the drone on the highway. I think if you have an auto you'll find you have to slam the throttle to have decent acceleration from a stop. If you have a manual you can have a one tire fire anytime you want. I've been buying exhaust parts from jegs and have been happy. They also have those ball swivel joints if you need it. I can get part numbers for what I used if you need.

[Simply Volvo]

Yes it would be great if you could get me a part number for the ball swivel joint thing. And what is the size of the pipe coming out? i believe its 1.75in.

[Deimos]

I made an ss exhaust for my NA. I did 2-1/2" from the header back. Im running the obx ss header. Originally I used a Magnaflow highflow cat, a 14" oval body Magnaflow in the stock spot and a pypes m80 by the fuel tank. I adjusted my cam timing with the ipd tool. Now running a dynomax vt in place in of the magnaflow. Quieted it dow n a bit and reduced the drone on the highway. I think if you have an auto you'll find you have to slam the throttle to have decent acceleration from a stop. If you have a manual you can have a one tire fire anytime you want. I've been buying exhaust parts from jegs and have been happy. They also have those ball swivel joints if you need it. I can get part numbers for what I used if you need.

Needs moar LSD

[Eliotg]

Yes it would be great if you could get me a part number for the ball swivel joint thing. And what is the size of the pipe coming out? i believe its 1.75in.

#555-30695 is Jegs part number for 2-1/2. I don't think they have smaller than that. The tube on mine was 2-1/2" on the header side of the cat and 2-1/4" on the swivel side of the cat. I think your going to have to measure the tube where you plan to cut.
I've done a couple exhausts for P80 cars and the tube sizes have been different based on Turbo/NA or if it had the stock muffler or cat replaced with certain OEM/aftermarket direct fit replacements.

Needs moar LSD

I would love one. It's on the short list for the next time I have to pull the transmission.

[Kevin.]

have any of you looked into the stainless steel headers for the N/A 850/X70's?

http://www.ebay.com/...80f2737&vxp=mtr

and

http://www.ebay.com/...941587a&vxp=mtr



I might get one in the coming months just to see if I notice any differences

[Eliotg]

I'm using the OBX one.
It's well made and fit well. The tubing is mandrel bent and slightly larger than the stock manifold.
The stock tubing was bent on a regular tube bender and had some cross section change in the bends.
Mine does not have mounts for the heat shield and has a bung you'll have to plug if you don't have EGR.

Forgot to mention to get new OEM gaskets and bolts. The ones that come with the OBX are garbage.

Edited by Eliotg, 31 July 2012 - 01:28 PM.

[Kevin.]

what about the other brand exhaust manifold? it looks to be of comparable quality and it comes with a plug for the EGR port. $140 is a good deal IMO

[Simply Volvo]

#555-30695 is Jegs part number for 2-1/2. I don't think they have smaller than that. The tube on mine was 2-1/2" on the header side of the cat and 2-1/4" on the swivel side of the cat. I think your going to have to measure the tube where you plan to cut.
I've done a couple exhausts for P80 cars and the tube sizes have been different based on Turbo/NA or if it had the stock muffler or cat replaced with certain OEM/aftermarket direct fit replacements.

I would love one. It's on the short list for the next time I have to pull the transmission.

Sounds good to me, thanks! I always thought the pipe coming out of the cat was 1.75in but i must be wrong! Ill do some measuring.

[Eliotg]

what about the other brand exhaust manifold? it looks to be of comparable quality and it comes with a plug for the EGR port. $140 is a good deal IMO

$140 is a good deal for 304 stainless. I think i paid $175 shipped for mine.The EGR bung looks a little longer, it has the heat shield bracket and the collector looks shorter and less contoured than the OBX but they look the same otherwise.

[Kevin.]

if I pay $50-$60 less for that, I would still be happy

[Deimos]

If I was to redo mine, I'd get one of those headers... I can't tell any difference between them by looking at them.

Then again, I've got the silly Denso engine, I probably won't bother.