3 inch exhaust system on a NA car..makes this any sense [Archive]

MP 245

11-07-2005, 05:03 PM

..thank you so far.

I´m planning to replace the current B230F with a B230FT in 3 - 4 years. At that time I want to do a complete rebuilt of the car including a limited slip diff, the m46 manual gearbox, a few suspension and interior modifications.

Problem is...my old exhaust system is blown and I need replacement. So I considered to use the 3 inch Turbo stainless system. But if things are so like u described it and it wont work with the NA engine, I´ll use a standard Volvo exhaust and use the stainless one when the rebuilding process starts.

Thanks a lot and have a nice day

Mirko

JW240

11-07-2005, 05:15 PM

the stock system with a removed muffler could be a nice upgrade, or a Simmons cat-back system, that sounds very nice.. And they can be had very cheap, even second hand.

MP 245

11-07-2005, 05:25 PM

...sounds interesting, specially concerning that the first muffler is the one which is severly shot, the last one sounds good, but I think I´m going to replace the whole system...with a single muffler upgrade ;-)

Thanks a lot for that hint...

cu

Mirko

BDKR

11-07-2005, 05:41 PM

Do the whole thing. I had my 3" system on for 3 months before starting my +T. The car was quicker, got better mileage, ran cooler, and had a cool mellow tone. Besides, it certainly won't hurt anything.

hockey930

11-07-2005, 06:08 PM

If I remember corectly when I was doing research on my old gle going to 2.5 in was a 5-10ph gain, going to 3in was a 5 hp loss. I have no idea why I recall that or where from.
Eamonn

iThinkergoiMac

11-07-2005, 08:02 PM

A bigger exhaust will reduce the backpressure of the engine, which is bad for NA, good for Turbo...

BDKR

11-07-2005, 10:28 PM

A bigger exhaust will reduce the backpressure of the engine, which is bad for NA, good for Turbo...

That's a myth! LOL! The only engines that benefit from back pressure are two strokes. If there is a loss of something when going to a larger exhuast on an N/A vehicle, it's normally torque or power under the curve. The exact nature of your loss or gain has everything to do with cam timing.

Every single vehicle I've put a larger exhuast system on has benefited in some way. That includes two Yamaha FJ1100's, a 500 intercepter, a '79 Camaro, both of my Subaru Legacy Wagons (both N/A), and my present car before I turbo charged it.

towerymt

11-08-2005, 12:42 AM

A bigger exhaust will reduce the backpressure of the engine, which is bad for NA, good for Turbo...
uh oh

towerymt

11-08-2005, 12:45 AM

I would wait and do the 3" exhaust when you put the turbo engine in. At that time, you can make it fit nicely.

My rear muffler (2.25") rusted out, so I replaced with with a 2.5" muffler. The reason is because I plan to add a turbo and redo the exhaust in 2.5", so I can reuse the muffler.

Poik

11-08-2005, 12:47 AM

That's a myth! LOL! The only engines that benefit from back pressure are two strokes. If there is a loss of something when going to a larger exhuast on an N/A vehicle, it's normally torque or power under the curve. The exact nature of your loss or gain has everything to do with cam timing.

Every single vehicle I've put a larger exhuast system on has benefited in some way. That includes two Yamaha FJ1100's, a 500 intercepter, a '79 Camaro, both of my Subaru Legacy Wagons (both N/A), and my present car before I turbo charged it.
Ditto. Just a myth.

Dan242tic

11-08-2005, 12:48 AM

A bigger exhaust will reduce the backpressure of the engine, which is bad for NA, good for Turbo...
Its just a matter of tuning for the exhaust, if you put a big exhaust with no other changes, you may lose hp. Everything works together, cam, fuel curve, ignition timing, port sizes, intake. If you are really going to a F+T eventually, buy the 3" and make it work.

olov

11-08-2005, 12:55 AM

I´m planning to replace the current B230F with a B230FT in 3 - 4 years. Problem is...my old exhaust system is blown and I need replacement.
ok, well 3-4 years is a long time, so if i were you, and i had a little $ saved for a new exhaust, i'd get the cheapest 2.5 system i could find(most likely crush bends) and maybe buy a new muffler yourself so you know it's a decent quality and will sound good. then use the extra $ for other mods. a full 3inch mandrel bent system will be A) hard to get because places think it won't fit under there B) pretty expensive compared to other NA mods C) might be too much exhaust for a stock 4cyl.

so search around here, and check out the usual places online for prices for a system for your car

good luck

Dan242tic

11-08-2005, 01:00 AM

deleted for your protection

Dan242tic

11-08-2005, 01:00 AM

ok, well 3-4 years is a long time, so if i were you, and i had a little $ saved for a new exhaust, i'd get the cheapest 2.5 system i could find(most likely crush bends) and maybe buy a new muffler yourself so you know it's a decent quality and will sound good. t
good luck
This is probably good advice, a lot can happen in that long of a time. You could even use a stock 240 turbo exhaust as its larger than the NA exhaust. Remove the last muffler and run stright pipe out the back. You could make a 3" work, but it is alot of money and effort to make it work on a NA car. Why so long till you turbo it? Doesn't cost that much and doesn't take too long with all the parts readily and cheaply available,

MP 245

11-08-2005, 04:48 AM

hi guys..

thanks a lot for your answers! After all I´ver read I think I´m using either the stock 2´ without first muffler or the original turbo system with one muffler too. Each versioan sounds good. Taking into account that I´m going to swap the engine, I think it´ll be the turbo setup. Sure I´ll post the results of my "experiments".

Thanks again and have a nice day

Mirko

Captain Bondo

11-08-2005, 05:02 AM

do you have a stock exhaust manifold/downpipe? If so either get a cheap, basic, or even used stock exhaust system if you can, then wait and do it right.

A nice setup is to get a downpipe from an 1984 DL (B21A if you got them in your market). They have no front resonator and are just a straight pipe with a slipjoint. Replace your blown muffler with a piece of pipe. No sense spending any more money than necessary on something that only need to work for the short term.

An NA system designed for proper gas-speed may exhibit some degree of backpressure as a necessary evil or result or side-effect, but backpressure in and of itself is NOT a good thing and there is not enough crack in the world to convince any reasonable person otherwise.

Forg

11-08-2005, 06:23 AM

Ditto. Just a myth.
The myth part is the usage of the term "backpressure" to describe why oversized exhausts hurt performance. The real reason is the gases slow down & get all swirly, actually causing more "backpressure".
B230's are capable of using a lot of fuel(+air), so I can see it being possible a 3" exhaust isn't too large ... 2.5" wasn't too large for my 1.6L Corolla (but then, it had the same power as a B230F ... and 2.5" felt like the upper limit, it really needed 3.5k on board before it went anywhere).

BDKR

11-08-2005, 07:07 AM

The myth part is the usage of the term "backpressure" to describe why oversized exhausts hurt performance. The real reason is the gases slow down & get all swirly, ....

Exactly. Just didn't feel the need to venture into it.

B230's are capable of using a lot of fuel(+air), so I can see it being possible a 3" exhaust isn't too large ...

Well, I'm inclined to say "I know from experience" that it isn't a problem. HOWEVER, my system expanded to 3 inches just after the last merge of the N/A header. There could've been a sizeable drop in torque had I went to a header with larger runners.

11110000

11-08-2005, 09:15 AM

2.25" works great on the NA redblock. I had the ipd Sport Exhaust on my B23F for ~8 years. It just broke two weeks ago. It consists of the 240 turbo parts from the underaxle pipe on back, with a coupler pipe taking the place of the resonator. You can assemble one like that cheaply.

Here's another option. As mentioned, my ipd exhaust just broke (muffler pipe cracked off/out), and I needed something to get me through a few months until my +T project is realized (at long last.) I got a 27" x 2.25" Cherry Bomb from Pep Boys ($18), and plumbed it in to what was left of the ipd system. Despite all the negative press these things have received over the years, mine sounds great. It is not much louder than the ipd system under throttle, and I think it's even quieter under cruise conditions.

MACH FYV

11-09-2005, 11:01 PM

3" is overkill. 2.5" on a hard tuned NA motor is fine, 2.25" on a bolt-on NA. If all you have is an intake, keep it stock. No need for the noise unless it's making power, and it won't make much on a stock NA engine.

745 TurboGreasel

11-10-2005, 03:04 AM

NOT a myth.any increase of exhaust flow capability moves the power cuve into a higher RPM range...
Go to far, and you'll loose the bottom end you never even knew you had.

I went to a lot of trouble to put dual stacks on our dump truck(350 ci), and after that, it woldn't climb the hill into the yard with a load on.
Swapped the old 2-1 pipe, and it was fine again.
That said, OEM is almost always on the restrictive side of OK, so a measured step up will help.
If you have other mods supporting higher output, you will see more of a gain.

MACH FYV

11-10-2005, 03:17 AM

Aftermarket exhaust systems for a 6.0L Corvette Z06 are not even 3". What makes you think a 4 cyl Volvo would require more flow than a Z06? Think about it. ;)

stylngle2003

11-10-2005, 03:22 AM

because a Z06 isn't turbocharged, where backpressure (or lack thereof) becomes of utmost importance

BDKR

11-10-2005, 10:53 AM

One more time as this is obviously a semantics issue.

1) Backpressure for the most part is bad. If it's not, feel free to explain.

2) 3" is overkill for most N/A engines. It's overkill for most Turbo applications as well in terms of outright power production (as the goals of some are not that lofty to begin with). However, let's not forget the positive effect less backpressure has on the turbines ability to spool and maintain boost in the upper reaches of the rev range.

3) Putting a larger exhaust on a particular engine may/will alter the characteristics of it's power production, but whether or not that's a bad thing has a lot of dependencies.

You guys need to realize that just becuase the power characteristic of the engine changes a little (it's going to take a lot more then the exhaust to get it to change a lot) doesn't mean backpressure is good. All it means is that depending on your cam timing or some other fixed physical characteristic of your engine, a larger exhaust may highlight certain parts of the rev range or bring to light others that were previously lackluster. Probably both.

Somebody earlier in this thread said that putting larger pipes on a vehicle would have the effect of moving the power up in the rev range. That may be so, but how does that translate to "brackpressure is good"?

And larger doesn't mean noisier either. There are a lot of variables there so you can't simplify this kind of thing with simple maxims.

Lastly, the difference in the cost of building (NOT BUYING) a 3" over a 2.5" system is negligible.

zombiewoof

11-10-2005, 11:59 AM

Another vote for 240 Turbo exhaust. Cheap, easy, not noisy, effective performance and gas mileage gains.

JE Jr

11-10-2005, 01:12 PM

You should consider something a little less restrictive, but mayba a 3" would ba a overkill, and it might be hard to get it to fit well and not scrubbing when going over speed bumps.

As I mentioned somewhere before Volvo did offer a "GT 60mm exhaust" for 240 that increased the peak power of an B23A with 10Hp @5500rpm (~112Hp stock...)

I think that a stock "Turbo" exhaust would be a good compromise.

If possible to get in Croatia you could get a Swedish "Simons" 2,5" exhaust for your Volvo, but it might be costly to import it??

www.ray.se

stylngle2003

11-10-2005, 01:42 PM

thanks for the link

seth

11-10-2005, 09:31 PM

http://auto.howstuffworks.com/engine1.htm

Here is a good engine animation people might use to help them explain their positions on the subject.

From what I've heard taking the exhaust off a old N/A volvo will cause it to run poorly. Is this because the exhaust valves aren't closing fast enough between stages 1 & 2?

You have to click my link to know what stages 1 & 2 are fyi. ;-)

stylngle2003

11-10-2005, 11:14 PM

Darkness

11-10-2005, 11:32 PM

simply untrue

maybe if you take off the o2 sensor and manifolds...but otherwise it runs just fine with open dump.....

ask Mayday, or better yet, ask me :rofl:

An NA motor will run better with a smaller exhaust because it will help "stack" the charge. It may "run fine", but you will loose power. Now, cam timing will definitely help/ hurt you here. I would think a high overlap cam would run like poo with a huge exhaust and standard cam timing. You would be loosing intake charge at low/ mid RPM into the exhaust. With an open header/ no header, this effect would be crippling to peak power output. A lower duration/ shorter lift cam would work better, but would affect your ability to load the cylinder before closing.

stylngle2003

11-10-2005, 11:38 PM

An NA motor will run better with a smaller exhaust because it will help "stack" the charge. It may "run fine", but you will loose power. Now, cam timing will definitely help/ hurt you here. I would think a high overlap cam would run like poo with a huge exhaust and standard cam timing. You would be loosing intake charge at low/ mid RPM into the exhaust. With an open header/ no header, this effect would be crippling to peak power output. A lower duration/ shorter lift cam would work better, but would affect your ability to load the cylinder before closing.

ok dude

mAydAy

11-10-2005, 11:50 PM

You want no backpressure. A Volvo with an open manifold dump gets scavenging, which is what happens when you have no backpressure, but its unbalanced and sucks the charge out of the chamber. BTDT. Optimal is going to be open header. You don't want backpressure, but you're usually safer siding with a slight bit of it to prevent scavenging.

My 240 ran perfectly with just open downpipe. So armed wtih that, what I'd do in your spot if you want to do the 3", is just keep your stock manifold, downpipe and cat, and do a 3" catback. Anything behind the cat doesn't matter, a 2.25" cat iwll provide WAY MORE than enough backpressure. What I'd realistically do is grab a 240 Turbo exaust, they work very well.

As for the V8 thing, thats utter crap. My Suburban runs a 3" catback and it could have gone 3.5" without any losses. I gained massive low end torque and gains all across the board with it. The thing about the Vette is it uses duals. Dual 2.25"s flow similarly to a single 3" (Area of dual 2.25"s is slightly larger, but have to account for losses because of alot more surface area and all).

Darkness

11-10-2005, 11:53 PM

ok dude

Yeah, whatever huh? Anyway, I've BTDT. More power with a 2.5 in straight exhaust than the open DP. Ever noticed why "tuners" don't sell very many NA 3 in kits for sub 2.5l engines?

Darkness

11-10-2005, 11:55 PM

You don't want backpressure, but you're usually safer siding with a slight bit of it to prevent scavenging.

Yeah, that's what I was eluding to. Too much creates cross flow which results in a dead charge. And scavenging is good - in moderation.

mAydAy

11-10-2005, 11:59 PM

Yeah, that's what I was eluding to. Too much creates cross flow which results in a dead charge. And scavenging is good - in moderation.
Exactly, which is why to run no backpressure header construction and design is critical. Scavenging is beyond good, its excellent.......in moderation. Moderation being the key there. Too much and you're in major trouble.

745 TurboGreasel

11-10-2005, 11:59 PM

3" catbackYou have a Cat? There is more backpressure than any tailpipe you could buy. Added to that, you pipe is over 9 feet long.

mAydAy

11-11-2005, 12:05 AM

You have a Cat? There is more backpressure than any tailpipe you could buy. Added to that, you pipe is over 9 feet long.
Actually I have two 2.25" cats.
Lots of people run them without cats and have no problems. Lots of people actually run them no cats and dump em under the beds of their trucks, and lose no power. I have cats still, I'll be swapping them out to high flow metalcore race cats when I put on headers.

If you work it out, a single 3" for a 350ci engine is a good size, it actually still will have backpressure.

stylngle2003

11-11-2005, 12:29 AM

Yeah, whatever huh? Anyway, I've BTDT. More power with a 2.5 in straight exhaust than the open DP. Ever noticed why "tuners" don't sell very many NA 3 in kits for sub 2.5l engines?

i would never suggest running anything bigger than 2.5" on an NA volvo 4 cyl...that's just silly

i was originally referring to the "An NA motor will run better with a smaller exhaust because it will help "stack" the charge. It may "run fine", but you will loose power" and "With an open header/ no header, this effect would be crippling to peak power output." statements, since, especially at high rpm, you want no restriction at all, and having no (well, very little) backpressure aids in making peak horsepower, albeit at higher rpm. your cam timing comments were on the money, however

MACH FYV

11-11-2005, 12:46 AM

because a Z06 isn't turbocharged, where backpressure (or lack thereof) becomes of utmost importance...

Dude, read the thread...it says NA, not Turbo.

stylngle2003

11-11-2005, 12:51 AM

Aftermarket exhaust systems for a 6.0L Corvette Z06 are not even 3". What makes you think a 4 cyl Volvo would require more flow than a Z06? Think about it. ;)

while we're arguing semantics, and derailing this somewhat decent thread, YOU didn't state whether the "4 cyl Volvo" was NA or Turbo...and it does make a difference

3" on an NA Volvo.....stupidly oversized

2" on an NA Volvo....stock, undersized

2" on a Turbo Volvo (we'll keep it to Turbo Redblock...) waaaaaaaaaaay too small

3" on a Turbo Volvo (ssdd)....Just right :-D

i get what youre saying, i just don't think it was important to the development (and my partially causing the derailment) of this thread

SwedishFish

11-11-2005, 01:35 AM

Aftermarket exhaust systems for a 6.0L Corvette Z06 are not even 3". What makes you think a 4 cyl Volvo would require more flow than a Z06? Think about it. ;)

Hey poo-head, that's TWO, count em, TWO 2.5" pipes. Can we add...?

That makes 5".
So...
Yeah, a 4 cylinder N/A Volvo doesn't need 5" of exhaust flow.

745 TurboGreasel

11-11-2005, 01:58 AM

funny thing is....probably the only rason cars come with restricted exhaust is because the MFR saves $.07/car by using pipe one size too small, and another $.09 by putting some crappy kinks in it. Then to buy a Corvette with a decent unkinked exhaust, they charge an extra $16,000/car...

I have also observed that a gutted cat has about the same muffling properties as my Flowmaster.

Mayday, with dual cats, it might be worth looking into an Xpipe, they do some interesting stuff. My car that has one is louder below 3000 RPM than above, which I find kind of strange, but performance is noticably improved over 2-1 with a 3" dump(no cat or muffler) after the tranny. I'm not satisfied with the exhaust note yet, and have to swap mufflers some more....I may have a sickness.

MikeHardy

11-11-2005, 02:36 AM

problem is the simons cat back isn't as good as the simons full non cat system. catback still leaves ya with the crappy downpipe section with it's bad 2-1 merge

MACH FYV

11-11-2005, 03:03 AM

while we're arguing semantics, and derailing this somewhat decent thread, YOU didn't state whether the "4 cyl Volvo" was NA or Turbo...and it does make a difference...

My bad...seeing that the title of the thread was 3 inch exhaust system on a NA car , I figured it was self-explanatory.

And yes, most V8's use dual pipes. But common sense alone when you see fire-breathing turbocharged cars making ~500 and ~600hp are using single 3" systems (it seems some of the Supra guys claiming in the 1,000hp range use 4" single), that an NA Volvo with an intake doesn't need it. That's all. ;)

seth

11-11-2005, 08:57 PM

Will a completely stock 240 with stock cam timing lose power when the exhaust is removed? My buddy knocked the exhaust off his B21F right after the downpipe and he lost a bunch of power. When he repaired it the power was back. What could explain this? Loss of scavenging power? :???:

MACH FYV

11-11-2005, 09:55 PM

It will lose torque and become much slower in the "streetable" RPM ranges. If you normally spent your time between 5000-7000 rpm, it wouldn't be that bad. It's just a sacrifice...you pick up a few HP up top, and lose a grip of TQ down low.

740Weapon

11-12-2005, 02:44 AM

2 cents

im pretty sure if your running a cam without overlap (m) bigger exhaust is always better.

also on a 16 valve car bigger is sometimes not better.

Forg

11-12-2005, 05:26 AM

TWO 2.5" pipes. Can we add...?

That makes 5".
I assume that's a joke? :)

klr142

11-12-2005, 05:50 AM

Aftermarket exhaust systems for a 6.0L Corvette Z06 are not even 3". What makes you think a 4 cyl Volvo would require more flow than a Z06? Think about it. ;)
Andy already pointed it out I guess, but yeah, it has more than one exhaust pipe...
Yeah, whatever huh? Anyway, I've BTDT. More power with a 2.5 in straight exhaust than the open DP. Ever noticed why "tuners" don't sell very many NA 3 in kits for sub 2.5l engines?
Because most people who would buy an exhaust off the shelf don't have engines that are custom built to require a 3" exhaust or no exhaust at all. The people who have developed their engine that far will make their own exhaust one way or another.
i would never suggest running anything bigger than 2.5" on an NA volvo 4 cyl...that's just silly
Are you sure about that? You might want to re-phrase that to say "on most NA volvo 4 cyl" engines... Phil S. needs a 3" short (side exit) exhaust for his 2.2l b20... The current longer exhaust is causing him problems actually with his setup. But yeah, I'm just saying you can't say all volvo NA engines can't use a 3" exhaust. :-P (just givin ya a hard time;-) )

For my case, on a 91 b230F attached to an automatic, I'm modding my airbox, tossing in a V15 NA cam, other minor things, and later on maybe some more major things, and am planning to run IPD's "sport"(stock turbo) exhaust for the NA cars. I'd rather have something custom done up with fewer bends and mandrel piping(is the stock turbo piping mandrel bent?) and known free flowing mufflers. One smaller one for dampening nasty resonations, and then another larger one farther back for the real sound dampening. Oh well, I'll settle for the IPD Sport exhaust with the stupid S tailpipe cut off to be straight back.

swedefiend

11-13-2005, 10:00 PM

Because most people who would buy an exhaust off the shelf don't have engines that are custom built to require a 3" exhaust or no exhaust at all. The people who have developed their engine that far will make their own exhaust one way or another.

Trust me. There are few and far between sub 2.5 liter engines requiring more than 2.5 inch exhausts. There are sooo many other makes that have kits up to 2.5 for the respective popular engines (VW, Nissan, Etc...). Yeah, I had my own made, but I wasn't necc. refering to Volvos. I was making a generalization. Even when modded the norm for sub 2.5l 4 bangers is 2.5 inch.

klr142

11-14-2005, 01:54 AM

Trust me. There are few and far between sub 2.5 liter engines requiring more than 2.5 inch exhausts. There are sooo many other makes that have kits up to 2.5 for the respective popular engines (VW, Nissan, Etc...). Yeah, I had my own made, but I wasn't necc. refering to Volvos. I was making a generalization. Even when modded the norm for sub 2.5l 4 bangers is 2.5 inch.
I was just saying, you can't say that there aren't any. Just being a bugger. ;-) We're on the same page.

DaButcher

11-14-2005, 03:02 PM

Well, you are all comparing inches, only inches here.
* Are the pipes mandrel bent?
* How is the flow thru the muffler?

Dont go simmons, I would rather go JT-Superflow or SuperSprint.
On the B19a, with stock exhaust, but 1 x simmons 2.5", the sound was crappy.. way too much bass in the exhaust..

Now, with the volvo 960 engine, 3" jt superflow all way, custom collector, removed cat, the sound is OH-SO-COOL, and NO WAY that I've lost any power doing this!

The simmons also made a positive effect on the B19A,but the sound-level was not pleasant.. It made sounds at a way lower frequency than the jt-superflow does on the b6304.

I use the 3" jt superflow made for 240 N/A, which *claims* 10hp gain I think.
Go JT rather than Simmons.

other cheap mods, include:
* electric fan