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My estimation is based on Corksports baseline dyno of the 2.0l of 118hp in Seattle. With just an SRI and CB they were then making 135hp. I am located in chicago which is significantly closer to sea level than Seattle and I have an exhaust cutout thats a larger diameter than the CS CB. Therefore I feel that my 140hp estimation should be right on the money...hopefully.
 

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My estimation is based on Corksports baseline dyno of the 2.0l of 118hp in Seattle. With just an SRI and CB they were then making 135hp. I am located in chicago which is significantly closer to sea level than Seattle and I have an exhaust cutout thats a larger diameter than the CS CB. Therefore I feel that my 140hp estimation should be right on the money...hopefully.
I'm not sure I believe they made 17hp with just an SRI and exhaust.
 

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Like I said thats just what their website says. As soon as I can get my car dynoed I'll post the results. I'll even try to make a video.

If anyone wants to see and hear my exhaust you can youtube Tim's Mazda 3 w/ qtp exhaust cutout
 

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Could not find ANY dyno run for stock Mazda 3 Skyactiv 2.0. via Google search...:sad 1:

Assuming about 20% drive train loss, 124 HP at the wheel would be an optimistic number. The dyno run should tell whether Skyactiv technology really improves on typical drive train loss.

Maybe a better way to feel more power is to remove the seats, the spare tire, and the insulation. That should reduce couple hundred lbs, right :001_tongue:
 

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My estimation is based on Corksports baseline dyno of the 2.0l of 118hp in Seattle. With just an SRI and CB they were then making 135hp. I am located in chicago which is significantly closer to sea level than Seattle and I have an exhaust cutout thats a larger diameter than the CS CB. Therefore I feel that my 140hp estimation should be right on the money...hopefully.
Im with Dom there's no way it made 17 WHEEL horsepower with just those parts. Maybe 17 at the fly on a really good day but no way at the wheels

If youre just looking for dyno numbers, a good dyno guy can quickly change the parameters to read whatever you want lol

Could not find ANY dyno run for stock Mazda 3 Skyactiv 2.0. via Google search...:sad 1:

Assuming about 20% drive train loss, 124 HP at the wheel would be an optimistic number. The dyno run should tell whether Skyactiv technology really improves on typical drive train loss.

Maybe a better way to feel more power is to remove the seats, the spare tire, and the insulation. That should reduce couple hundred lbs, right :001_tongue:
Insulation is the easiest part. There isnt any haha
 

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I don't care what you put on it. A tune is where the power is at. Even on the speeds. Bolt ons dont get much power. You have to tune. An intake may add 5hp. An exhaust maybe 7-8 at the crank. Whp maybe 5 total. 5hp on the street won't even be noticeable.
 

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Ok lets play with this 20% drivetrain loss idea. The 2.0l no skyactive is rated at 148 hp at the flywheel which with a 20% drivetrain loss means that it will make 118.4 hp at the wheels(exactly what CS said it baselined at).

Now even if the reported 17 hp gain was at the flywheel with the same 20% drivetrain loss the gain at the wheels would still be 13.6 hp.

So when adding that 13.6 whp to the original 118.4 whp and the total whp would be 132 whp. Which while that is 3 hp less than what CS reported I'd still be totally happy with only be wrong on my estimation by 8 whp.

However I've been discussing with the master technician that I work with (tunes subaru's in his spare time and daily drives a 12sec STI on stock Turbo) and he said that with the age and mileage of the car and with how well I take care of the car I should only be seeing a 15% or less loss in the drivetrain. So if I do the same math with a 15% loss through the drivetrain I would baseline w/o modifications at 125.8 whp. Then with a 17 hp gain at the flywheel and a 15% drivetrain loss the wheel gain will be 14.45 whp. That would bring my power to 140.25 whp.

But as with anything it's impossible to throw a number out there and it be completely universal for all cars. So until the car gets on the dyno its a complete toss up on what I'll actually get. I just hope it is only a 15% loss, but I still wouldn't be disappointed if its closer to 130 whp.
 

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The reason I believe my exhaust will make more power than the CS exhaust is because of its location (in place of the rear cat and resonator) and because of its turn down to increase cylinder scavenging. The great thing about my exhaust setup is the faster I'm driving down the road the harder it'll pull the air through the cylinders thus at creating more and more hp.
 

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The reason I believe my exhaust will make more power than the CS exhaust is because of its location (in place of the rear cat and resonator) and because of its turn down to increase cylinder scavenging. The great thing about my exhaust setup is the faster I'm driving down the road the harder it'll pull the air through the cylinders thus at creating more and more hp.
Your probably right. Your exhaust will make way more power!
I'm sure this will be taken the wrong way but oh well. On an NA mazda 3 there isn't much power to be made. I don't care if you do an intake, exhaust, and headers you may make 10-15 hp. You have to tune the car to make power. Period! Even a speed don't make much power with bolt ons. You have to tune the speed for the bolt ons to make power. Besides an NA car runs better with some back pressure on the engine.

You need to tune it for the extra air. Just because the air goes out the back faster doesn't mean it comes through the front faster. That's only turn on a turbo car as the intake is driven by the exhaust. You need to tell the MAF to bring in more air.
 

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The reason I believe my exhaust will make more power than the CS exhaust is because of its location (in place of the rear cat and resonator) and because of its turn down to increase cylinder scavenging. The great thing about my exhaust setup is the faster I'm driving down the road the harder it'll pull the air through the cylinders thus at creating more and more hp.
Everyone always says something like this but it is never true. If there was magic to be had by putting an exhaust on an NA car we would all have high HP monsters. Guaranteed your exhaust does not add any more power than any other exhaust.

Damn you Gran Turismo and Need for Speed, you taught us an exhaust is worth 10HP alone.
 

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The reason I believe my exhaust will make more power than the CS exhaust is because of its location (in place of the rear cat and resonator) and because of its turn down to increase cylinder scavenging. The great thing about my exhaust setup is the faster I'm driving down the road the harder it'll pull the air through the cylinders thus at creating more and more hp.
Scavenging is accomplished mostly at the header, not the remainder of the exhaust. Theres 2 common approaches, a 4-2-1 header setup with (relatively) long primaries, OR a 4-1 header with a properly designed merge-plate in the collector. Primary length is very important either way.

If the header is not well-designed, nothing you do post-header will have any notable effect on scavenging, UNLESS there is a *significant* deficiency/obstruction in the post-header exhaust... The Skyactiv 3 simplely isnt that bad.

Of course, when you go forced-induction, all that goes out the window :)
 

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The reason I believe my exhaust will make more power than the CS exhaust is because of its location (in place of the rear cat and resonator) and because of its turn down to increase cylinder scavenging. The great thing about my exhaust setup is the faster I'm driving down the road the harder it'll pull the air through the cylinders thus at creating more and more hp.
The only real place to make power in an exhaust system is in the header. Thats where scavenging actually occurs in a proper design. After the collector the pipe just needs to be the right size and free of restrictions to maintain the velocity and volume for the intended powerband.
This is why race motors have completely custom made exhaust headers and also why V8s with log style manifolds make such easy power with a pair of headers
What youre describing is the same theory as putting a vacuum on your tailpipe to suck out the exhaust. Yes it'll suck out the exhaust but it doesnt make it more efficient since the header is still the same and thats where the choke point in flow and scavenging is

Your probably right. Your exhaust will make way more power!
I'm sure this will be taken the wrong way but oh well. On an NA mazda 3 there isn't much power to be made. I don't care if you do an intake, exhaust, and headers you may make 10-15 hp. You have to tune the car to make power. Period! Even a speed don't make much power with bolt ons. You have to tune the speed for the bolt ons to make power. Besides an NA car runs better with some back pressure on the engine.

You need to tune it for the extra air. Just because the air goes out the back faster doesn't mean it comes through the front faster. That's only turn on a turbo car as the intake is driven by the exhaust. You need to tell the MAF to bring in more air.
I feel like you know what youre trying to say but dont know how to say it haha so ill help you. The MAF sensor doesnt let air in, it only measures it. The throttle body is what lets air in. When something is done to an engine that allows more air in it needs to be tuned to know what to do with that extra air that it can bring in otherwise it just does its normal thing and leans out which is never good
 

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The only real place to make power in an exhaust system is in the header. Thats where scavenging actually occurs in a proper design. After the collector the pipe just needs to be the right size and free of restrictions to maintain the velocity and volume for the intended powerband.
This is why race motors have completely custom made exhaust headers and also why V8s with log style manifolds make such easy power with a pair of headers
What youre describing is the same theory as putting a vacuum on your tailpipe to suck out the exhaust. Yes it'll suck out the exhaust but it doesnt make it more efficient since the header is still the same and thats where the choke point in flow and scavenging is



I feel like you know what youre trying to say but dont know how to say it haha so ill help you. The MAF sensor doesnt let air in, it only measures it. The throttle body is what lets air in. When something is done to an engine that allows more air in it needs to be tuned to know what to do with that extra air that it can bring in otherwise it just does its normal thing and leans out which is never good
Yea bad wording. That's about what I meant but I ain't a mechanic. I just understand how the engines work.
 

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Scavenging is accomplished mostly at the header, not the remainder of the exhaust. Theres 2 common approaches, a 4-2-1 header setup with (relatively) long primaries, OR a 4-1 header with a properly designed merge-plate in the collector. Primary length is very important either way.

If the header is not well-designed, nothing you do post-header will have any notable effect on scavenging, UNLESS there is a *significant* deficiency/obstruction in the post-header exhaust... The Skyactiv 3 simplely isnt that bad.

Of course, when you go forced-induction, all that goes out the window :)
Not entirely. A good manifold on a turbo engine helps a lot with spool.
Its also possible for the exhaust post turbo to outflow the capability of the wastegate to control boost which results in boost creep. Thats usually a problem only on internally gated turbos which is what most factory stuff is
 

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The placement of my cutout has alot to do with the scavenging effect. because it is literally directly after the factory exhaust manifold it will scavenge. Not as well as if I had an aftermarket header which I am planning on getting in the very near future but with it being so close its probably as efficient as it can possibly get on the stock manifold. And I completely agree that the only way to truly unlock my engines full potential will be to get a tune the factory parameters are enough to compensate for this current setup w/o causing the engine to go too lean. As I've said earlier I have data logged and fuel trims are fairly consistent with no knock or detonation. And an engine never needs back pressure. This is a myth. It needs a proper balance of flow and velocity. Too much of either can cause you to make no power of even lose some but if its done just right large gains can be made from an exhaust. Because I have the electronic valve in the cutout I keep it closed partially on take off and open gradually as I increase my speed. If I start with it fully open I will lose low end torque so I use the length of the factory exhaust to my advantage for this reason.
 

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Dammit @Keto I just basically said what you said lol. I guess I shouldnt have started writing then went to the kitchen mid response haha
LOL... sorry :smartass:

Not entirely. A good manifold on a turbo engine helps a lot with spool.
Its also possible for the exhaust post turbo to outflow the capability of the wastegate to control boost which results in boost creep. Thats usually a problem only on internally gated turbos which is what most factory stuff is
Agreed. I only meant that the dynamic is a bit different than a N/A setup. I would say, generally, on a *good* turbo setup, large diameter is better post-turbo. On the few turbo bikes I've tuned, all but one preferred the 'stubby' config post-turbo, short and fat pipe, lol. But then again, they all had well-optimized header/manifold setups despite their compactness.
 

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The placement of my cutout has alot to do with the scavenging effect. because it is literally directly after the factory exhaust manifold it will scavenge.
How did you make this determination? In a 'typical' 4-1 setup, secondary/collector length/diameter (i.e. the initial '1') where pulse convergence occurs is typically designed to create a slight low-pressure condition in the primaries. That helps scavenging. If not done properly, it can hurt scavenging.

Because I have the electronic valve in the cutout I keep it closed partially on take off and open gradually as I increase my speed. If I start with it fully open I will lose low end torque so I use the length of the factory exhaust to my advantage for this reason.
So its a power-valve setup. OK.

And just exactly how do you control it?
 
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