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Others on this forum have mentioned a loss in perforamance when upgrading to completely free flow exhaust. I have friends that also have expressed concern about me installing an GWR exhaust without back pressure for the turbo.

What is the real deal?..
 

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Others on this forum have mentioned a loss in perforamance when upgrading to completely free flow exhaust. I have friends that also have expressed concern about me installing an GWR exhaust without back pressure for the turbo.

What is the real deal?..
I have the full GWR exhaust and it has clearly provided an increase in performance - right along the lines of what Brian claims with his dyno readout on his site. The turbo spools up faster and stays spooled longer leaving the car in the "sweetspot" longer making it much more enjoyable to drive.

One very knowledgeable user on this site, sharkcohen, did only the GWR mid-pipe and muffler delete (had a problem getting the original cross-pipe off) and had a performance decrease which is counter to what Brian states should happen according to his web site.

I am not an exhaust engineer so I'm not sure how increased restriction (i.e "back pressure") on the turbo would increase its performance. My observation is that reducing the restriction and thereby increasing the flow of the exhaust has increased the performance which is consistent with the goal of exhaust "improvements" on other cars.

I'm a big fan of the full GWR exhaust both sound and performance. Your mileage may vary...
 

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I've just finished installing that system and all I can say is I don't understand what there talking about. My car runs better, sounds better and my gas mileage is a tick better even running the car harder. This weekend I put 200 miles on the system running backroads and hwy. speeds of 75 and my average gas mileage was 33-34 mpg. Opening up the system is better for a turbo car. Go for the GWR system.
 

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I have the full GWR exhaust and it has clearly provided an increase in performance - right along the lines of what Brian claims with his dyno readout on his site. The turbo spools up faster and stays spooled longer leaving the car in the "sweetspot" longer making it much more enjoyable to drive.

One very knowledgeable user on this site, sharkcohen, did only the GWR mid-pipe and muffler delete (had a problem getting the original cross-pipe off) and had a performance decrease which is counter to what Brian states should happen according to his web site.

I am not an exhaust engineer so I'm not sure how increased restriction (i.e "back pressure") on the turbo would increase its performance. My observation is that reducing the restriction and thereby increasing the flow of the exhaust has increased the performance which is consistent with the goal of exhaust "improvements" on other cars.

I'm a big fan of the full GWR exhaust both sound and performance. Your mileage may vary...

I agree completely with these comments. I have the full GWR system and love the performance and sound improvements.
I am not sure why Sharkcohen had his loss of performance and also do not pretend to be an exhaust system engineer myself,...but perhaps the issue was related to the fact that Sharkcohen attached the large diameter GWR midpipe to the small diameter stock crossover pipe. Perhaps that affected the flow negatively??? dunno.

But I do love my full GWR system, and I fully trust the Brian's posted dyno results.
 

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The real deal is this...

Others on this forum have mentioned a loss in perforamance when upgrading to completely free flow exhaust. I have friends that also have expressed concern about me installing an GWR exhaust without back pressure for the turbo.

What is the real deal?..

Especially at the 8 minute mark. The GWR exhaust is fine. I'm going with the duel resonators exhaust delete from AutoRicambi.

Not Sure.:)
 

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by the way is the Abarth muffler and output pipes calvanized or stainless. Due to noise restriction here, I heard the Ricambi with resonators and sounds good and not too loud. If ever I change it, as of now it will be this one.
 

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Some Numbers? ;)


The EU Abarth has a valve in the RM exhaust, with closed valve, it isn`t able to reach the factory topspeed numbers on German Autobahn. (about 230km/h) it stops at about 215km/h (like the F124)
With open Valve it managed to achieve his factory vmax.

That is what you can see on the dynochart. A free muffler gives you more top end power, but a too much unrestricted system after cat will course in high torque and power loss in lower regions.

btw. The 1,4l reacts significant to fuel quality. With 98ROZ (Super Plus) it has more low range power.
 

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The subject of exhaust back pressure is really complex.

Here is another way to look at it. This is a bit oversimplified, but it's correct in principle and may help with understanding. Exhaust flows faster through a smaller pipe, that helps with scavenging. But if it's too small it's restrictive and all the exhaust can't escape fast enough to make up for the size restriction. On the other hand, if the pipe is too big, you lose velocity, and scavenging.

Generally speaking, if the pipes are too big you lose power at the low end of the rpm range, but too small and you lose some high end. Now, there are some limitations here. You can't just go bigger and bigger and keep gaining at the high end. At a certain point, going bigger does nothing, because the restriction is nearly zero, but it hurts the low end more and more. Of course the opposite is also true, but it's not relevant since nobody is going to offer an aftermarket systems that's smaller than stock.

The whole trick with exhaust design, from a performance perspective is to keep the velocity high enough for good scavenging, without being restrictive. Pipe sizing plays a big part here, but so does muffler selection, collectors (except on a turbo or supercharged car), bends, section lenghts and so on. The best systems take all of this into account.

Greg
 

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The subject of exhaust back pressure is really complex.

Here is another way to look at it. This is a bit oversimplified, but it's correct in principle and may help with understanding. Exhaust flows faster through a smaller pipe, that helps with scavenging. But if it's too small it's restrictive and all the exhaust can't escape fast enough to make up for the size restriction. On the other hand, if the pipe is too big, you lose velocity, and scavenging.

Generally speaking, if the pipes are too big you lose power at the low end of the rpm range, but too small and you lose some high end. Now, there are some limitations here. You can't just go bigger and bigger and keep gaining at the high end. At a certain point, going bigger does nothing, because the restriction is nearly zero, but it hurts the low end more and more. Of course the opposite is also true, but it's not relevant since nobody is going to offer an aftermarket systems that's smaller than stock.

The whole trick with exhaust design, from a performance perspective is to keep the velocity high enough for good scavenging, without being restrictive. Pipe sizing plays a big part here, but so does muffler selection, collectors (except on a turbo or supercharged car), bends, section lenghts and so on. The best systems take all of this into account.

Greg
Great explanation. Didn't know that the power delivery vary with RPM. Does that mean dual mode system like the Record Monza give best of both world (in theory)?
1. In low RPM range: valve = close = higher restriction = higher power delivery
2. In high RPM range: valve = open = lower restriction = higher power delivery
 

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What goes into the system also has to go out of the system. ;)
A less restrictive exhaust can cause power loss with OEM Software and Engine power but will provide significant improvements if you also increase the power output of the engine. Engineers always look at the complete system not only just on one part or section.

So, the right way would be to design an exhaust specific for the engine output or you are designing a system who fits both worlds. Stock and modified but it always would be a compromise.
There isn`t just one right way and fluid- and thermo dynamics isn´t as easy as we would wish. Trust me. ;)
 

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Great explanation.
Thanks

Didn't know that the power delivery vary with RPM.
It absolutely does. The Fiat 1.4 turbo puts out A LOT more power at 5000 rpm than it does at 1500rpm. That power comes largely from burning more fuel, thus creating more exhaust. More exhaust means a relatively larger optimal exhaust pipe size.

Does that mean dual mode system like the Record Monza give best of both world (in theory)?
Probably not. A muffler is usually a different type of restriction than a decrease in pipe diameter. In any case, it's too far back to have much effect on scavenging. That said, I think the Record Monza is really cool, and I like the dual mode feature, but I doubt it would outperform the Remus system or some of the other quality systems.

Greg
 

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Discussion Starter #12
The subject of exhaust back pressure is really complex.

Here is another way to look at it. This is a bit oversimplified, but it's correct in principle and may help with understanding. Exhaust flows faster through a smaller pipe, that helps with scavenging. But if it's too small it's restrictive and all the exhaust can't escape fast enough to make up for the size restriction. On the other hand, if the pipe is too big, you lose velocity, and scavenging.

Generally speaking, if the pipes are too big you lose power at the low end of the rpm range, but too small and you lose some high end. Now, there are some limitations here. You can't just go bigger and bigger and keep gaining at the high end. At a certain point, going bigger does nothing, because the restriction is nearly zero, but it hurts the low end more and more. Of course the opposite is also true, but it's not relevant since nobody is going to offer an aftermarket systems that's smaller than stock.

The whole trick with exhaust design, from a performance perspective is to keep the velocity high enough for good scavenging, without being restrictive. Pipe sizing plays a big part here, but so does muffler selection, collectors (except on a turbo or supercharged car), bends, section lenghts and so on. The best systems take all of this into account.

Greg
Greg,

Maybe some insight into the GWR (Full System) vs. the Abarth MagnaFlow you sell?

GWR, no muffler and includes the cross pipe

MagnaFlow, muffler and no cross pipe.

Curious, as GWR posts gains, while I can find nothing on the MagnaFlow. Which makes me wonder if the MagnaFlow is all about sound and looks, and not any performance gains.

Just trying to make sense of it all. ;)
 

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The Magnaflow is similar in design to the Remus, except that the Magnaflow is 2.5", whereas the Remus is 60 mm. I can tell you that the Remus catback is awesome, it sounds and performs great.
 

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Inside Stock Muffler

Has anyone opened and seen what the inside of the stock muffler looks like. I've been researching on line and found many resonaters are just hollow chambers which makes me wonder if you could gut a Abarth stock muffler then reseal it. Believe me there is a lot of science that goes into muffler design. I've been reading it and now I'm burned out. I was looking to save a few bucks for throatier sound. Thanks.
 

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Can be done and I have driven a A124 with this done and it was LOUD !!!!!
Thanks for the info. LOUD is what I don't want. The Ragazzon Evo Line may be the way for me to go as I'm just looking for an axel back.
 

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Has anyone opened and seen what the inside of the stock muffler looks like. I've been researching on line and found many resonaters are just hollow chambers which makes me wonder if you could gut a Abarth stock muffler then reseal it. Believe me there is a lot of science that goes into muffler design. I've been reading it and now I'm burned out. I was looking to save a few bucks for throatier sound. Thanks
Brian at Goodwin Racing cut a stock muffler (from a classica I think) open. It's a mess. I think you can find the pic on his site.
 

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Greg,

Maybe some insight into the GWR (Full System) vs. the Abarth MagnaFlow you sell?

GWR, no muffler and includes the cross pipe

MagnaFlow, muffler and no cross pipe.

Curious, as GWR posts gains, while I can find nothing on the MagnaFlow. Which makes me wonder if the MagnaFlow is all about sound and looks, and not any performance gains.

Just trying to make sense of it all. ;)
In the 500 Abarth world, this would be an easy question, because I have heard all the various exhaust systems, installed some and looked at all of them up close. In the 124 world it's much more difficult. I just haven't seen these systems yet on the 124, let alone really been able to compare them. I'll do the best I can here.

I really like the Remus system. I like their bends, pipe sizing (for a stock turbo car) and their exhaust tips. We don't offer the Remus system, and I don't think any vendors here do. If I was to buy a system for my car right now, as long as I didn't plan on going to a bigger turbo this is the system I would buy.

We sell the Magnaflow system. Magnaflow makes very good products. I don't know why they didn't put out dyno results. Often manufacturer's don't, usually it's a marketing choice as dyno results often create more arguments and hostility than they solve. I am 100% confident that the gains with the Magnaflow system will be essentially the same as with any other system with similar pipe diameter.

For a rear section only, I like Auto Ricambi. Adding just the rear section makes a lot of sense for some people. It gives you the look, sound, and some performance benefit, at a relatively low price, with easy installation, and minimal chance of screwing something up. They also have what in my opinion is the most aggressive looking tip design.

Another rear only option I like is the Record Monza, but in my view it's way too expensive compared to the other options out there.

Those are the only systems I feel comfy discussing at this time.

Greg
 

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Great feedback ... BTW, 2.5" is 63.5MM...
 

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Discussion Starter #20
Thanks Greg.

Still don't quite get the muffler or not to have a muffler options and the pros and cons.

I do like the bigger tips on the MagnaFlow. Remus does not offer a dual tip that fills the Abarth openings yet.

It does seems that the cross pipe is a choke point and solved by GWR. The complications though are off-putting.

Super Sprint is developing one as well.
 
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