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I have the QUAD exhaust and love it. My question is , does adding the midpipe add any more HP?. I really don't want to add the crosspipe due to a lot of the install issues I have read about.
 

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Know one has experience with this?.
I have the full GWR exhaust with the crosspipe.
I am not convinced that the midpipe by itself would add much if any horsepower.
There are two main obstructions in the stock system. One is at the factory muffler and the other is at the bend in the crosspipe. I would think the added diameter of the midpipe would only be a benefit once you had removed the other two points of obstruction.
 

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I lost performance when I installed the GWR midpipe and muffler delete. I replaced it with the Remus catback and got it all back and then some.
 

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When you delete the muffler, I think you loose some back pressure.
 

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There's not a lot to adding the crosspipe. I did it as well. I went about it a bit differently at the connection to the mid-pipe though. Instead of using the supplied gasket, I used a doughnut-style gasket for a Honda Passport. It fit perfectly. If you want the added performance of the exhaust, you will definitely want to include the cross-pipe.
 

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When you delete the muffler, I think you loose some back pressure.
Which should help, I would think, but there are other forces at work, too.

Back pressure is only useful right after a header that is specifically designed for scavenging. On a turbo, the real concern is keep gas velocity and laminar flow as high as possible. Sharp bends, changes in diameter, even changes in temperature (pipe bend that goes in and out of air flow under the car), etc., all contribute to turbulence. If you do a muffler delete, you're best off keeping the same diameter as the pipe in front. As the gas cools, it takes up less space. If you combine that with a larger tail than mid pipe, you'll lose velocity and generate turbulence. I don't have any experience with GWs or any other muffler delete, so don't read anything into what I just said as if it relates to theirs specifically.

I've been looking at doing a muffler delete for race only, but haven't found anything I like yet.
 

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I have done a full Goodwin exhaust on my Abarth. the only mistake was I did not get the resonated midpipe. the installation was simple. it was done in my driveway using ramps and jack stands. there were no dyno pulls, so I could not verify the claimed power gains. but the sound was magnificent but a bit too loud for the neighbors. so I have on order the resonated midpipe. in the mean time, while I wait for delivery of my new midpipe, I have reinstalled the factory muffler to tame the sound level. after doing a side by side comparison, it becomes clear the Goodwin system will increase flow, due to being a fully mandrel bent system with no pinches in the turns. installation was simple using only standard hand tools. once installed the car did seem to have a bit more power, but it may have been a placebo effect based on the sound improvement....
 

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I could see how the non-resonated exhaust could be a bit too much, especially for the passengers (and your neighbors). Even the resonated unit is at the limit of comfortable for me when I want to converse with the passenger without changing my driving style too much around town.

If you didn't reset the ECU (disconnect the battery when working on the O2 sensor), I suggest you do so now. I've not heard Brian comment on this, but these cars seem to be sensitive and I'm one of those that got a CEL and some odd performance issues after a couple hundred miles after install. Did get a pending CEL even after I reset the ECU but no odd performance issues. I'm happy to report the pending CEL has now cleared on its own. Anyway, I think your ECU will adjust to a full cat back exhaust change better when starting from a clean slate. YMMV.

Enjoy!
 

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I did the non resonated as well and am considering getting the resonated mid pipe. It's too loud.
Though we are certainly happy to sell anybody the other midpipe....note another option is just having your local muffler shop weld in a 4 inch diameter resonator of your choice to the midpipe you already have.

It should be a pretty easy addition for most muffler shops, just be sure to use a stainless resonator like we do so it lasts, etc. A 10 to 12 inch long is super easy, something like a Magnaflow 10416 is likely about the max length and diameter that could be fit.... and those are all stainless and about $65 delivered.
 

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Thanks Brian. Madness did the install here in LA. I can have them add a resonator. I am pretty happy with the exhaust overall. It definitely improved the response of the car and I have no intention of changing it out. It also sounds great in the canyons and with the roof down, but on long trips on the highway with the roof up is where it bothers me most.

The noise issue has more to do with what I want. My friends all love it and don't want me to do a thing.

I had a Lotus Elise last, which was a track car first and road car second. Was making 240hp with only 1980lbs full tank. I swore to the lady I would build something more streetable this time. Which is code for quieter and not so stiff. And working air conditioning and a stereo you can hear.
 

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Thanks Brian. Madness did the install here in LA. I can have them add a resonator. I am pretty happy with the exhaust overall. It definitely improved the response of the car and I have no intention of changing it out. It also sounds great in the canyons and with the roof down, but on long trips on the highway with the roof up is where it bothers me most.

The noise issue has more to do with what I want. I had a Lotus Elise last, which was a track car first and road car second. I swore to the lady I would build something more streetable this time.
I hear you....;)

With my wife we talk about the mods that are 'wife approved' and those that are not. My cars tend to slowly side into race car status as the years pass. For those reading along at home, my suggestion is start with our midpipe with resonator as the 'wife approved' selection.

One interesting thing about the midpipe here is that you actually have two big spots for resonators...because the Miata version of this car has a second converter that the Fiat does not have. The Fiat still has the big space where that cat normally lives. Thus, even somebody with our resonator midpipe could add a SECOND resonator if their significant other really wanted the whole setup toned down even more. This might get more relevant once highflow cats are available, which raise the whole system sound.
 

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I did find an interesting workaround. Turning off sports mode on the highway reduces the noise level for cruising.

Also, to the original poster, I would recommend getting the full exhaust. Having looked at the stock crosspipe, it is terrible. As Brian describes, it pinches in. This is the part I was most interested in changing when doing the exhaust. I know on my setup there is a definite improvement in turbo response. I did a lot of "testing" on the same mountain roads. I care a lot about mid throttle response. The top end is better too. I did the DV+ at the exact same time.
 
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