Exhaust opinions / Mandrel bent 2.5 or 3" / Input?

[Backtobasics]

Next modification on my Dart Lite, is exhaust.

Currently has single system, that Y off into 2 or 2.5 dual, 12" glasspacks, and crushed tailpipes that rattle and bang on everything.

My local customer will bend me 2.5 or 3" (these are the sizes they can mandrel bend). They will come off the manifold with 2-2.5 and step up at the bellhousing under the car, with a flange so I can remove to fab turbo tubing, and re- install to drive as needed or wanted.

If I go 2.5 I can get the muffler and tip free (vendor rep).

If I go 3" I have to buy the muffler and tip, or I can have it turned down just behind the bumper for stealth look.

I know both sizes are overkill for a N/A /6. However, this car will sprout a turbo over the winter. (Grand National Turbo, Front mount intercooler) I think the 2.5 would work since it is mandrel bent would be OK for the turbo system, but I am leaning more towards the 3" system.
Opinions? Input from some of the turbo guys?

 

[JCNathan]

Sounds like a neat project. I'd go with the 2.5" tubes. While everyone thinks 3" pipe are cool, they weigh a little more and don't fit as well. Also, I would make sure that nothing, NOTHING is welded unless absolutely necessary. I work part time in a muffler shop and you can't believe how many classic muscle cars I see with rusted exhaust. (Rust always starts where the pipes are welded). Regular muffler clamps work great and you can rotate stuff to adjust it. If you can afford it, tti and other exhaust companies make these really cool "band" type clamps. Once installed you can hardly see them!!

Anyway...you asked!!!

Jerome

 

[dusterdon]

personally the mandrel bent tubing 2.5 will probably flow as well as the 3" if its not mandrel bent. If you're going out the back with it the 3" will be tight between the gas tank and the spring too.

 

[Backtobasics]

Let me clarify.
They can mandrel bend either 2.5 or 3" He thinks he can get either one over the axle.

 

[memike]

I have been asking the same ?, And I will be doing a 2 1/4 off the flange
and running it to a single muffler with dual out lets with two 2" down pipes at the bumper.
Not allot of hp, 170/ offey Holley 390 .

I think the 3'' is over kill and takes up to much room.
I am waiting to see a good dual exhaust for a 170/. {low deck}.:clock:

 

[JCNathan]

Backtobasics,

I agree with MEMIKE, 3" is overkill even for a motor with a supercharger. Your "bender" may say he can get it over the axle but my experience with "A" bodies is that there is not a lot of room under there: shocks, brake/fuel lines, fuel tank, springs, etc. You certainly can "muscle" those 3" pipes back to the bumper but at the expense of some additional weight and aggreviation. Again, 2.5" will work out just fine.

But hey...it's your car...

Jerome

 

[Thrashard340]

A single 3" would be plenty for a single turbo /6.

Are you goiing with true duals or a split system?

 

[Backtobasics]

It will be a single system, from trans to bumper. I am considering the 3" to the muffler, and 2.5 out, but we will see. My gut says 3" to keep backpressure down as much as possible once the turbo is installed. The 3" may be way too much for NA but it forces me to follow through with the turbo....

 

[AdamR]

With a turbo and a good amount of boost your going to want the 3" pipe. 2.5 would be plenty if you werent going to run the turbo.

 

[Prine]

^ What Adam said.

330hp is the choke point on a single 2.5" pipe.

If your /6 HP goal is higher than 330, go with a single 3" pipe,...it does not choke until 600 Hp.

:read2: :cheers:

 

[abodyjoe]

i say 3" and a turn down definitely looks better.

 

[Keith Mopar]

I don't want anybody laughing at me but I biult a 3" system for my 2.5 turbo 4. Just made the sytem myself because the exhaust place here that does mandel bending told me it can't be done under that car, and that was 2.5!!!
The cost is about 1/4 of getting them to do it. I cut off the old brakets off the old system and welded on my new exhaust.

If your going turbo go 3.

 

[Bigmacdak]

Keith Mopar, kudos to you on your home-made system. Looks like a package deal! You should go into the buisness! lol! The black turndown looks SICK!!

I would go with 3" as well. I think 3" is the norm for anything turbo.

 

[Backtobasics]

Keith Mopar, that is very close to what I am having done, but the muffler is pre-axle. The guys doing it are a semi-local muffler shop (hour drive for MPG Experiment) but they can mandrel bend. So they are going to build it from mandrel bent sections, much like yours.

 

[Keith Mopar]

Keith Mopar, kudos to you on your home-made system. Looks like a package deal! You should go into the buisness! lol! The black turndown looks SICK!!
I would go with 3" as well. I think 3" is the norm for anything turbo.

Thanks. My stock exhaust was 2.5 leaving the motor, but before it got to the muffler they had it down to 1 3/4 . ( comparison pic)
I built the exhaust when the car was on my hoist, so if you were doing the work with a car on jack stands it could be done just a little slower.

Backtobasics, your system will probably look a little better than mine when you get it back, it sure does make a nice looking peice. I painted mine with hi heat paint to try and presurve it. My car dosn't have many miles on it but it still looks good.

 

[Bigmacdak]

1 3/4! WoW. My 34 hp Ford tractor has that soda straw exhaust on it. Cant blelieve it was on a turbo car... Nice work!

 

[Prine]

Heh, ya its far cheaper IMO, to purchase 3" Mandrel Bends, flanges, and whatever else you may need and find a buddy or shop that will let you use a Mig Welder and make your own exhaust system.

Here is what I did when I upgraded from 2.5" - to 3" on my turbocharged 4 banger:

BTW, there was one heck of a decrease in back pressure, and a super increase in Flow.

 

[Backtobasics]

I thought about doing it myself, I have the welder, and they will provide me the bends (I am designing up the turbo system in my head, counting bends, etc that will come from them) but I am going to have them do it for a couple reasons:

• Fishing 3" (still undecided) on an A body is probably best left to a professional
• I want to set it and forget it, so I can focus on the turbo area, and know that this is fixed, and turbo ready
• It is only costing me 50.00 more then the bends themselves for them to do it....the bonus of being a supplier for some of the stuff they need.

It looks like this SATURDAY! =P~

 

[Nick M.]

as the former owner of a 2.3 turbo ford, i can tell you that most run a 3" mandrel bent system with a straight thru style muffler. lower backpressure improves spool time noticeably.

 

[Backtobasics]

Sadly, it is not going to be this weekend. Holiday weekend and all, they decided to close for the long weekend. I will try to reschedule for another time.