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I'm a bit confused on the real performance gains on a cat back system with or without muffler delete.

Flyin' Miata over on the Miata Forum has a thread titled "Flyin' Miata Fiat 124 dyno thread!". They tested the 124 with various exhaust deletes and even with a full delete, came up with small HP and TQ gains. In the order of around +8 hp and +10 tq.

Goodwin states there full cat back is worth +15 hp and +50 tq.

Not trying to stir things up. I'd just like to hear from vendors (or others) on how there can be this big of a discrepancy. If you go by Flyin' Miata, $1250 for an exhaust system isn't worth it from a performance standpoint.
 

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I have the Roadster sport 3 piece and I can believe the claims. The car is much quicker and the torque is noticeably greater.
 

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Remember this Turbo 1.4 is NOT a new motor..there are YEARS of dyno reports out there on what happens when you let it breath. As for FM's work, their high altitude compensation challenges are not new (see folks asking about that in that same miata.net thread).

If you do look around at Abarth 500 results (Dart, Jeep, etc), the argument will not be about whether this engine responds to exhaust flow mods, it will be whether we should have gone 3 inch instead of 2.5 inch.

We decided 3 inch was too much to neatly fit under the car, would be only marginally better than 2.5, and 2.5 is working great. I expect some will do 3 inch custom but we wanted something that could be neatly installed by shops and customers everywhere without much challenge. The Crosspipe is key to the flow and 2.5 is the max that fits cleanly with the manual transmission, 2.25 inch is max to fit clean around the bigger automatic transmission.
 

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I'm a bit confused on the real performance gains on a cat back system with or without muffler delete.

Flyin' Miata over on the Miata Forum has a thread titled "Flyin' Miata Fiat 124 dyno thread!". They tested the 124 with various exhaust deletes and even with a full delete, came up with small HP and TQ gains. In the order of around +8 hp and +10 tq.

Goodwin states there full cat back is worth +15 hp and +50 tq.

Not trying to stir things up. I'd just like to hear from vendors (or others) on how there can be this big of a discrepancy. If you go by Flyin' Miata, $1250 for an exhaust system isn't worth it from a performance standpoint.
I am not going to comment too much on a specific vendor's system, because I don't think that will be appropriate. I will say that I think that all the systems currently on the market for this car look good.

1. Power gains. We tested the car with a high flow crossover dumping just after the firewall. It sounded terrible (there is a video of this on my site). This was in an effort to find the maximum possible gains with an impractical, but theoretically best case system. Our findings very closely matched those mentioned in this thread from Flying Miata.

2. One European manufacturer shows gains of about 4hp on a Euro 124. When you consider that they were testing on a lower powered model and sort of extrapolate the results to a higher powered US car, those numbers make sense with what I have seen.

3. This car, especially when modded is very difficult to dyno. Power at the high end will typically indicate lower than actual.. Power at the low end can be made to vary by controlling how much time you give the turbo to spool up. That means that the gear used, and exactly when you hit the throttle can have a huge effect. The car also runs MANY different boost maps, so unless you log everything run to run, it's impossible to know if the changes in power are due to the ECU switching maps, or if they are gains from the modifications. In other words, it's really easy to dyno this car and get results that are not representative of reality.

4. On the 500 Abarth, which has about the same engine with about the same amount of power, the two best systems are the Super Super Sprint system and the EL Gato system. I don't think either of these systems quote power numbers, but both have been on the market for a long time and in my experience they give about 8hp/10tq on a stockish car.

5. 50 torque would be a huge gain. As a percentage I don't know of any cat back system that gives gains that great on any car.

6. Depending on how your want to read factory data, the Record Monza rear exhaust gives 0-4 flywheel horsepower on an Abarth.

7. Exhaust upgrades can offer a lot more than just power increases. They can reduce weight, improve sound, and enhance appearance. Often those factors will weigh more heavily on a person's decision making than the 1-3 horsepower difference typically seen between them. I think that's part of the reason people buy the Record Monza system. Clearly it's going to be behind Goodwin or Remus in power, and it's really expensive, but it has some other qualities that some people find desirable. Personally I would probably get one of the other two choices.

I hope this helps.

Greg
 

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We decided 3 inch was too much to neatly fit under the car, would be only marginally better than 2.5, and 2.5 is working great. I expect some will do 3 inch custom but we wanted something that could be neatly installed by shops and customers everywhere without much challenge. The Crosspipe is key to the flow and 2.5 is the max that fits cleanly with the manual transmission, 2.25 inch is max to fit clean around the bigger automatic transmission.
Have you considered building something using oval tubing? Too expensive/ rarefied to productize?
 

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I fear some are taking the 50 number out of context. It is only 15 peak hp gained for complete system as noted on our site and our posts, chart again is below. That 50 number was simply taking note of the benefit of quicker spool from less restriction, about 50 torque way down off idle about 2000 rpms if you mash the pedal from same point (notice lowest and highest lines are starting exactly same rpm). To put it another way, you are simply getting that torque earlier than you would on stock system because the turbo spools faster. The actual gain in torque at peak torque production point in our testing was just about 18 as you can see on the chart, which is at about 3500 rpms. Our change for just muffler to muffler delete pretty well matched the factory claims for the Monza.

Greg was kind enough early on to explain that these motors do not like a two-wheel dyno. He looked at our results and suggested we are likely doing better in reality at the top end than we know. He suggested we check our O2 readings for going pig rich after about 4300 rpms. Sure enough, from where the horsepower line goes flat at that point the car goes very rich...when it is on a two-wheel dyno. Our only local four-wheel dyno is a mechanical linked Mustang unit with big parasitic drag to power the front wheels using the rear wheels. We have a date soon with the same high end four wheel dyno that the Madness guys use which can spin the fronts at a speed that perfectly matches the rear without having the car provide the power to spin the front roller. That dyno is a bit of road trip from here in San Diego but hungry to see our true top end performance with this setup. I hope it will change the shape of our chart and reveal more top end than we have shown on the chart here. More on that soon...

The next cool exhaust bit coming is highflow cat, spools the turbo even earlier and makes gains start to finish. Have not posted that chart yet, don't want to get anybody worked up until we can solve one thing with it. What is holding that up is that adding a highflow cat results in immediate code for cat efficiency. I have talked with the various makers of ECU reflash, including Greg at EC, about their ability to prevent that second O2 sensor code. As soon as one of them can do it, we will move forward with the highflow cat and recommend it be paired with the reflash that can prevent the code you otherwise would get. So, if anybody out there has that solution....please contact me!

 

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Have you considered building something using oval tubing? Too expensive/ rarefied to productize?
Yep, as you guessed, that oval option exists but complicates the production costs, too rare and too little additional benefit to be worth it for our purposes. Will somebody do it who is actually racing this car in a series? Very possible, already had a few Pros call us about using this car in Continental Tire Series or similar and for effort at that level it would likely pay off, but that's a whole other level of seriousness where every HP counts.

For street customers diminishing returns set in quick here, going from effective 1.7 inch of factory crunch bent Crosspipe to clean 2 inch makes a nice return on the investment (and similar with factory crunch bent midpipe, second pic below). Going from clean 2.0 to 2.25 gets a little more, going from 2.25 to 2.5 gets a tiny bit more, and beyond that 2.5 it is hard to measure any benefit and increasingly expensive to fit. Entrance to stock Crosspipe below, notice where it is crushed in right after the entrance. Somebody in one of the other threads noted that the stock bits looked like something that fell off on the freeway, and I think that captures the reality of crunch bent stock parts pretty well. The factory does crunch bends because it is cheap and fast, everything is made to very tight budget, factory needs to make profit and still sell these cars at relatively low price point despite very high relative costs of dedicated sportscar platform, etc.





Comparison of stock crunch bent Crosspipe in the background with clean flowing 2.5 inch prototype.
 

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Yeah, forgot about those. Should try it to see if it can avoid ECU hackery.

IIRC it worked with Hondas, Subes, and Fords back in the day. Will probably fail visual in California though but I'm no expert on that. Just trying to recall old memories.
 

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Hi Brian,

Is there any chance that, given sufficient demand, you might do a midpipe compatible with the Record Monza system? I ask because while clearly the full Goodwin setup is the best performing system, some of us would like, as Greg has mentioned, the coolness factor that comes with a dual-mode Italian exhaust. Getting to have that along with the performance gains from your system would be the best of both worlds.
 

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Hi Brian,

Is there any chance that, given sufficient demand, you might do a midpipe compatible with the Record Monza system? I ask because while clearly the full Goodwin setup is the best performing system, some of us would like, as Greg has mentioned, the coolness factor that comes with a dual-mode Italian exhaust. Getting to have that along with the performance gains from your system would be the best of both worlds.
My guess is they kept stock size inlet.... and not clear to me without more dyno testing how much of the benefit of upstream 2.5 inch system we give up if we pinch flow down to mate cleanly with the Monza. Thus, cannot say that game is worth the candle for us...or you. But I expect there will be a 2.5 inch aftermaket muffler with valve.

We designed a valved setup, our design included a planned retail well under the Monza...with less weight too. Some other vendor will do it. We skipped it because it proved unnecessary to the sound result we wanted, see the reviews and note that those with the resonator version midpipe report the full system is plenty tame when just cruising...so why would we add a valve that will eventually wear out and break if it does not add any additional function? The OEM use of those valves has led to a high rate of warranty service department repair and replacement for them, we include a LIFETIME WARRANTY so we are wary of including a mechanical valve in the design that will wear out. We use a resonator design with no moving parts that is very gas speed sensitive without a valve (the more pedal you give, the more sound you get...and more linear in effect than the mechanical valve). I have done 400 mile trips in a day in our Fiat 124, no sound fatigue issues because the wind noise is louder if just in cruise mode (top up or down). With our resonated setup pushing the pedal more reduces sound absorbing efficiency and gets you more sound on demand, no sudden dumps of sound from a valve, smooth linear increase. Gadgets are cool...until they break, so we dumped the valve design early in the testing process. K.I.S.S. right?
 

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Thanks Brian for the informative response. I was not aware that the Record Monza was having issues. Researching it more reveals that the spring valve seems to be a particularly finicky part, with some on the FIAT 500 forums reporting issues in as little as 400 miles. Definitely will have to think about this....
 
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