CoedNaked

So I have contacted my local exhaust shop, the only exhaust shop in the the city I live in, that has a Mandrel bender, plus they are only a 7 minute drive away, and I've heard they do good work. I just picked up a Borla 2 1/4" muffler. I have the 3vze. My engine is currently bone stock and the exhaust is basically the only mod I have planned for it.

They said that they only have dyes for their mandrel bender in the 1 3/4", 2", 2 1/2", and 3" sizes, I was originally planning to have them do 2 1/4" pipe between the cat & muffler and 2 1/4" pipe on the way out seeing as how I bought the 2 1/4" muffler, and the Borla catback which was made for my truck (which is now discontinued) uses the exact same Borla Turbo Muffler I picked up and all 2 1/4" pipes, before & after the cat.

So I am left with two options. I can go 2" between the cat & muffler, and 2 1/2" from the muffler out, or 2 1/2" before the muffler and 2 1/2" from the muffler out. Again keep in mind this is a 2 1/4" BORLA muffler.

What are your thoughts?

I am kinda leaning towards going to 2 1/2" before and after the muffler. Some say it might kill your torque but I don't think it will kill it as much as people say.

The fact they do mandrel bender is a huge thing for me.

Here is a third option that might make it more of a progressive system.

Have them mandrel bend a 2" mid pipe from the exhaust manifold to the cat,
have them bend 2" from the cat to the muffler and 2 1/2" on the way out. I'm thinking maybe that will help flow better initially as the entire stock exhaust is 1 7/8"

Elton

that will work cant believe they dont have 2-1/4''

CoedNaked

Wow, I'm surprised I only got one reply - Thanks Elton.

I have decided to go with 2" between the Cat & Muffler, and 2 1/2" from the muffler out.

I did some rough measurements of my current exhaust system and then did some volume calculations.

There is 30" of pipe between the cat & stock muffler currently. There is approximately rough 40" of pipe from where the shorter aftermarket Borla Turbo Muffler would be, and to where it would exit.

Using those numbers I plugged in some calculations and performed some reasonable assumptions.

For example
The system described above 2" before the muffler, 2 1/2" after has 290 inches of cubic volume (with 30" before, 40" after roughly)

A 2 1/2" system before & after has 344 inches of cubic volume
A 2 1/4" system before & after has 278 inches of cubic volume

So the 2" before/ 2 1/2" of after is the closest to 2 1/4" which is what I would want to go with.

My main reasoning as far as going with volume calculations was because we know exhaust gasses cool, and that can slow the flow of exhaust gas which will reduce your low end torque until you get things revving which increases the number of exhaust pulses and heats up the pipes (I want low end torque). So a certain amount of reason went behind it that way. I also figured that anything bigger as far as flow is concerned is better than the current stock system which is 1 7/8" pressure bent. The system I will have will have larger pipes, which are mandrel bent, and a higher than the stock flow, reputable 2 1/4" muffler. All plus points as far as getting some exhaust moving and making the engines job easier. I also figured the 2" pipe, 2 1/4" muffler, and then 2 1/2" pipe system would also be progressive in that sense.

rocket

iTrader: (1)

Being that you can't strictly use 2.25"....(your muffler shop sucks)...i think you made the right decision.

CoedNaked

I don't think they suck at all to be honest..... Keep in mind that they have invested in a mandrel bender, a very expensive piece of machinery, and they are a small family run business as far as I know. I don't know of one other muffler shop in the entire lower mainland that has a mandrel bender on site.

For me the mandrel bender alone is a huge thing. I could go to any other exhaust shop and get pressure bent pipes but to me why bother doing an exhaust with pressure bent pipes? I guess I can understand why they might not have 2 1/4" dies for their mandrel bender - when I drive by their shop almost everyday on the way to work, I see lots of custom restored cars having their exhausts done. These exahusts are often dual exhausts, with big displacement carburated motors. Plus I also see quite a few full size/mid size newer trucks there here and there, with big enough displacement motors to need 2 1/2" or 3" exhaust pipes. So things like 2 1/2" and 3" exhaust pipes are probably the norm there and why they have the dies for their mandrel bender for them. Then you got the smaller pipe sizes that they bend, 2" and 1 3/4" for the import car tuners who are much more numerous than guys like us.

A lot of the guys who are like us, who own 4x4's, that are modded or slightly modded, tend to be guys who do a lot of the work ourselves, are in most cases frivilous to some extent. These are the guys who don't see the value in mandrel bent pipes,most dont' even know what they are, just a cheap aftermarket muffler and pressure bent pipes, as long as it's done reasonable and inexpensive, will do. So a guy like me, who wants mandrel bent pipes, who has taken literaly a year to figure out what I want to do, who finally found an exhaust shop that does mandrel bending, who took the time to order in a Borla Turbo Muffler when I could get any other 2 1/4" muffler today from the local stores, are probably quite rare to them. Part of me frequenting them is also because they took the time to invest in a piece of equipment that will help them specialize and master the market they sell and deal in. I give them full credit.

I'll let you guys know how things turn out.

rocket

iTrader: (1)

I only meant they "suck" for the fact they can't bend 2.25" pipe which is about as common as anything. Good luck and i hope your happy with the final outcome.

ovrrdrive

2.5" pipe will slip right over the 2.25" muffler without any adapters and make for nice clean welds...

If you pay extra for mandrel bends and then use 2" pipe it will negate the mandrel bends you paid for as far as flow. They will still look nice but I think flow is the objective.

Personally I think having the tubes mandrel bent is a waste of money unless you have a show truck anyway though. If your new exhaust gives you a 10 hp increase with the mandrel bends, do you really think it would much less than that with regular bends in the pipes?

If so, and you really think the bends restrict the pipe that much in the bends all you would have to do would be to run bigger pipe in the corners and that would offset the lack of flow. But like I said, I don't think there are any real gains from paying for mandrel bends.

Sure does look nice though... No argument there at all.

If it were me though and I had to choose between 2" and 2.5" I'd go with the 2.5" anyday. You're paying for, and wanting better flow. The 2.5" is fine on the V6's... I have 2.25" on my 22re and it runs great. The extra displacement of the 3.0 can use a slightly bigger pipe...

But that's just my $.02 of course...

Joyota

Have you thought about asking them if you can strike some kind of deal, such as maybe buying them a 2-1/4" dye, in exchange for some or all of the work, depending on the cost? Just a thought.

pcmentor

I did the exhaust on my 85 22RE Motorhome 3 months ago. I put the headers on and had the rest put on. The hi flo cat was bigger pipe than the Turbo muffler I think. I was a little irritated at this because I thought they should be the same size pipe. But I had them put on. Between the cat and muffler we put a 3 " expansion tube just to try it. The resulting exhaust was about 7 feet shorter than original. Before it was out behind passenger side rear wheels now out before driver rear wheels. It's not a tinny sound but has good low humms but sometimes sound like I have a problem with engine, at idle. I was going to get some TRD stickers to put by the exhaust so people appreciate the noise. Pete

CoedNaked

Well I already got the truck in today. I'm doing 2" between the cat/muffler and 2 1/2" after the muffler. I thought about something like that, but I have no clue what a diehead would cost, and I don't think they do that much 2 1/4" 304 S/S.

I figure if I'm going to do an exhaust system, I might as well do it right. I bought the Borla Muffler. I am having it done in 304 MARINE grade Stainless steel, and since I'm going that way, the a little more pricey way, I might as well have it mandrel bent seeing as how the shop by my house is also the only shop that has a mandrel bender on site in all of western Canada.That was my reasoning. Maybe Mandrel bending won't make a huge differerence, but if I pick up an extra few horsepower then it's worth it considering the cost difference would probably be negligeable to a pressure bent system in the same 304 S/S pipe with the same Borla Muffler. Even if it's a $100 difference I still think it's worth it to go with the mandrel bent system over the pressure bent.

Rocket - they can bend 2 1/4" pipe - he said in a reluctant tone they could pressure bend it if I want to (he said it that way because they have a mandrel bender on site). Any shop can pressure bend 2 1/4" pipe. But only one shop in my city can mandrel bend pipe, they just don't have the 2 1/4" dies.

Flow doesn't come from having super large pipes. Flow comes from having the right size pipes and the right volume in those pipes. I've done a little bit of reading on the subject, and there is also some reasoning there, and flow comes from having pipes that move the exhaust out in a way that makes your engines job easier. A big part of this has to do with volume. If you have too much volume in your pipes, then the exhaust gases cool which means the engine has to work harder to push it's exhaust out until you rev the crap outta it which gets exhaust hot and flowing because of the increased number of exhast pulses now flowing the exhaust in the larger pipes. Hot exhaust flows, because when molecules are hot, they are very active, and pressurized. When gases cool they lose their pressur eand condense. The compromise I went with had just a slightly larger volume than 2 1/4" before/after the muffler so as far as flow goes, and I'll find out tommorrow, I think I'll be fine.

The bottom line is when I turn the key tommorrow and drive it off, I'll get home and give you guys a report on how things faired.

89934runr

If you're going to all the trouble to build a system like this, why haven't you explored the idea of buying 304 J-bends and U-bends, along with some straight pipe? Toy exhausts have tons of room- very easy to make using sections of pre-bent pipe. It'll probably be an extar-3-5 welds, but it doesn't sound like that's an issue.

I'd really encourage you to go with 2.25" vice giving in to the 2", while trying to reassure yourself it will work OK. It's alot easier to restrict flow than it is to open it up once you build a system. Your volume / cooling #s seem reassuring, but overall section volume has little to do with ability to handle pulsed-flow from an engine. Something to remember about smaller pipe- more friction due to higher speeds = power loss. Now, if you don't spin the engine past 5K much, it might not be an issue. But, if you drive 'spirited', you're looking at putting more heat back into the engine.

Either way, it sounds as if you're making a compromise in a 'no-compromise' system.

PS- for those of you that don't know, a good set of dies (which only apply to one size/wall thickness of pipe) can run $2K-3K. I know- I just went halfsies' on a 4" setup.

NCSU-4runner

how much are they asking for the work? i called a local place about my truck and they wanted $700+ for a complete custom mandrel bent system from my turbo-downpipe back. I bought my own 3inch mandrel bends from summit for < $150 and cut/tacked them together myself with some straight tube i also got from summit and had an exhaust shop finish the welds for a couple bucks. I couldnt justify the extra cost for at best a 5% performance gain.

Joyota

One thing sticks out in what I've read about your installation. You said, you were going to use 2" pipe between the cat and muffler. This seems to me to be where a bottlebeck will take place. There's absolutely no sense in having the rest of the exhaust 2-1/2", if you have 'even one' section that's smaller. These are the observations I've made based on experience as a firefighter and certified pump operator, educated on water flow. Air flow doesn't seem like it would be any different.

ovrrdrive

It would be very hard for me to believe that the same size pipe with mandrel bends would net a 5% gain alone by itself over a regular bent system...

If the gain could even be measured I bet it would be closer to <1% unless the pressure bends were kinked or something. Especially on a 22RE or 3.0 like most here have.

It's mainly for looks IMO...

dcg9381

He's probably better off doing that than doing a full 2.5" system... Why spend money on an exaust system that's going to result in a power loss?

CoedNaked

Well I got the truck back. They did a pretty solid job bending, the welds look good, overall I'm impressd! The 2" pipe slides right inside the 2 1/4" muffler, the 2 1/4" muffler outlet slides right into the 2 1/2" pipe, all welded. The did a good job on the hangers as well. Cost me $350 Canadian funds for all the work (parts/labour excluding muffler), another $135 for the Borla Turbo Muffler

As far as performance goes, the truck rev's more freely, and it doesn't fight me when I try and rev it past 3200 RPM's like it did in the past. Torque feels the same from about 1000 to 2200 RPM's. From about 2200 RPM's to about 4500 RPM's is where I noticed a bit of a difference. I mean we're not talking night & day, but you can tell the truck has some more pep behind it. The sound is actually extremely good. It is exactly like stock, only deeper. No Drone what so ever at any RPM's. That was one of my worries but I heard the Borla is pretty good for not droning.

I'm just curious, if some of you are concerned that I now have a 2" mandrel bent pipe between my cat & muffler, on this catback exhaust I just had done, what do you call the 1 7/8" pressure bent midpipe, between the Manifold & cat?

AH64ID

Gone

I think thats part of the reason I hear that cat-back isnt really worth in on a 3.slow unless you do the headers.

Glad you had good luck with yours.

Chapman88SR5

i disagree. my cat back is really good. its just a magnaflow highflow cat and a flo pro muffler and it helped. granted headers would help a lot more.

AH64ID

I am just going off of what I have read on here. Personally I did header, cat, and flowmaster on my 22RE, WOW

NCSU-4runner

for naturally aspirated i agree, but mine is turbocharged. Reducing backpressure is much more critical. Depending on how extreme the turbo setup is exhaust alone can change the HP numbers by more than 10% easily (meaning stock vs a very nice/big/mandrel setup)