The inlet and outlets of my Borla setup is really funky. The openings into the muffler body are the same diameter as the rest of the system. But to attach the pipes to the muffler it appears they swaged the pipe down to fit it inside muffler opening. It looks to me like the inlet can't be more than 1 1/2" ID.



I'd like to bring the size up to 2 1/4" ID, at least on the inlet side. However, trying to grind out the old weld in such an awkward place (Stainless - ugh) is going to be a ***** .

If I grind away the weld here:



Will the muffler pull apart? Or is it welded elsewhere? Anyone ever take a Borla apart? It sure would make the cleanup easier.

Neil

[This message has been edited by sspeedstreet (edited 03-17-2008).]

Nobody can give me some help here?

Well then, on with the monologue.

After considerable cutting I have the two ends apart. Unlike the diagram above, this is the interior layout of the Fiero Borla (The black dots on the pipes represent perforated sections):



The inlet pipe going into the "T" is only 1.75" OD! The straight outlet pipes are 2.00" OD, but neck down to 1.75" OD after exiting the case.

I have some left over 2.00" and 2.25" stainless from the rest of the system. I'm going to replace the whole interior plumbing with that.

I'll post some pictures as I go.

[This message has been edited by sspeedstreet (edited 03-17-2008).]

Is this going on your DOHC? The stock downpipe is 2.5"..

I wouldn't recommend messing with the borla setup too much. Borla unlike other companies actually dyno tunes their mufflers. Bigger diameter is not always better. Notice that on many cars Borla gets more hp out of an engine with a 2" piping, where others make less power with 2.5". Bigger pipes only make things louder, and can decrease the flow rate. It's not backpressure people want, it's the highest possible flow rate within the optimum rpm band.

Either way, experimentation is always good. Remember though, there is a reason Borla decided on the sizes for the pipes it did. Try calling Borla too. See if you can get the technician to explain/recommend a good size. If you're using it for a non Fiero engine, there might be a better fit they could recommend.
When I was shopping for a Cat-back system for my Mazda I talked to Borla technicians (not just sales reps) and the explained everything in total detail to me. It's part of the reason I went with them. They have great customer service and a lifetime warranty.

You can also call Magnaflow to cross reference their advice. Their R&D is great as well.

I gave that a lot of thought before I got into the cutting. I know that bigger is not necessarily better, but this thing necked down to as little as 1.50" ID at the inlet. It wouldn't surprise me if this was set up for a Duke, as small as it was inside. So, I've decided to do $200.00 worth of modifications to it. After I get done, it should look something like this:



OK, I'm gonna buy a Spintec.

quote Originally posted by Austrian Import: I wouldn't recommend messing with the borla setup too much. Borla unlike other companies actually dyno tunes their mufflers. Bigger diameter is not always better. Notice that on many cars Borla gets more hp out of an engine with a 2" piping, where others make less power with 2.5". Bigger pipes only make things louder, and can decrease the flow rate. It's not backpressure people want, it's the highest possible flow rate within the optimum rpm band.

A restricted pipe size necessarily decreases flow in this situation. Ideally the muffler would just not be there, the pipes would flow straight through remaining 2 1/2" from the downpipe without obstructions. This would give maximum flow. Every obstruction the muffler creates reduces flow. The last thing you want is your 2 1/2" exhaust system to have to pass through a 1 1/2" pipe at one point.

quote Originally posted by Austrian Import: I wouldn't recommend messing with the borla setup too much. Borla unlike other companies actually dyno tunes their mufflers. Bigger diameter is not always better. Notice that on many cars Borla gets more hp out of an engine with a 2" piping, where others make less power with 2.5". Bigger pipes only make things louder, and can decrease the flow rate. It's not backpressure people want, it's the highest possible flow rate within the optimum rpm band. Either way, experimentation is always good. Remember though, there is a reason Borla decided on the sizes for the pipes it did. Try calling Borla too. See if you can get the technician to explain/recommend a good size. If you're using it for a non Fiero engine, there might be a better fit they could recommend. When I was shopping for a Cat-back system for my Mazda I talked to Borla technicians (not just sales reps) and the explained everything in total detail to me. It's part of the reason I went with them. They have great customer service and a lifetime warranty. You can also call Magnaflow to cross reference their advice. Their R&D is great as well.

while that maybe true - I would assume their testing is done with a stock 2.8 Fiero. I would expect a 3.4 TDC would benifit from this.

Could you get a Borla muffler (maybe from the Pro-XS line) that's rated for the flow numbers required for a 3.4?

Does Borla make a muffler for the Lumina? You could use that as a guide which muffler to use for the Fiero.

quote Originally posted by Austrian Import: Could you get a Borla muffler (maybe from the Pro-XS line) that's rated for the flow numbers required for a 3.4? Does Borla make a muffler for the Lumina? You could use that as a guide which muffler to use for the Fiero.

There are like four cross-flow mufflers available that can fit in a Fiero at all from any manufacturer I'm aware of. There's a Borla, a Flowmaster, a Spintech, and a Magnaflow. The Borla and Magnaflow are pretty much the same; straight through with fiberglass packing. The Flowmaster is a 40-series chambered/baffled muffler and the Spintech is a spiral-baffled muffler.
The Lumina uses dual single-inlet single-outlet mufflers.

I would not mess with it.

I will tell you that system is one of the really bad systems we rejected, we ended up sending them back to Borla. The not so bad ones we sold as seconds at 40% off. The rest were later sold to Bob for $100.00 - $150.00 each, by Borla.

quote Originally posted by fieroparts.com: I would not mess with it. I will tell you that system is one of the really bad systems we rejected, we ended up sending them back to Borla. The not so bad ones we sold as seconds at 40% off. The rest were later sold to Bob for $100.00 - $150.00 each, by Borla.

I bought it from you a couple of years ago . . . . .

quote Originally posted by Steven Snyder: There are like four cross-flow mufflers available that can fit in a Fiero at all from any manufacturer I'm aware of. There's a Borla, a Flowmaster, a Spintech, and a Magnaflow. The Borla and Magnaflow are pretty much the same; straight through with fiberglass packing. The Flowmaster is a 40-series chambered/baffled muffler and the Spintech is a spiral-baffled muffler. The Lumina uses dual single-inlet single-outlet mufflers.

Almost correct: Both Borla and Magnaflow refuse to use Fiberglass because it disintegrates over time. (chemical reaction with exhaust gasses). They both use steel wool spun around the straight through pipes. (part of the reason they are much more expensive than ricer mufflers) You're right, they are pretty much the same though. The only difference I could find is: Magnaflow is made from a heavier gauge metal, than Borla, which is - I think - what causes Magnaflow to be bass-ier than Borla when punching the throttle.

Spiral baffles, sounds cool. I would love to see a picture of the inside of that setup.

So the Lumina has a dual pipe setup then? or are the two mufflers in series?

[This message has been edited by Austrian Import (edited 03-19-2008).]

quote Originally posted by Austrian Import: Both Borla and Magnaflow refuse to use Fiberglass because it disintegrates over time.

This Borla had the SS packing around the pipes, but also had fiberglass mat between the SS packing and the case.

quote Originally posted by sspeedstreet: This Borla had the SS packing around the pipes, but also had fiberglass mat between the SS packing and the case.

Interesting.. That sux. Wonder if they changed from using fiberglass in recent years, or the sales reps lied to me. Good to know though. Thanks for posting. Could you post pictures of the inside? I really want to see now what the Borla muffler actually looks like on the inside now. Both Borla and Magnaflow's promo shots conveniently didn't show the fiberglass, IIRC.

quote Originally posted by Austrian Import: So the Lumina has a dual pipe setup then? or are the two mufflers in series?

Dual pipes.

quote Originally posted by Austrian Import: Interesting.. That sux. Wonder if they changed from using fiberglass in recent years, or the sales reps lied to me. Good to know though. Thanks for posting. Could you post pictures of the inside? I really want to see now what the Borla muffler actually looks like on the inside now. Both Borla and Magnaflow's promo shots conveniently didn't show the fiberglass, IIRC.

im thinking of changing my exhaust it currently has full flowmaster kit from heads on back but its a single system i want true duals with cherrybombs and 90* downs right after em like the old hotrods lol i had a 2.8 s10 i did this on and it sounded surprisingly deap and throaty especially when reved would this be better for a turboed 2.8 that my flowmaster kit currently on the car?

quote Originally posted by sspeedstreet:

Thanks for the pics. That muffler is tiny!!

The Borla I had on my Mazda was 19" long (basically the longest that would fit into the mounting location) and that was for a regular KLDE 170hp Mazda engine. I can see how this muffler would be way too small for a TDC.