Project Scion FR-S Part 2- Uncorking the exhaust with GReddy

By Mike Kojima

The more time we spend behind the wheel of Project Scion FR-S, the more dear it is becoming to our hearts.  This car is really fun to drive.  What really puts a damper on things is that it simply just doesn't have enough power.

If power is the FR-S' weak point then that's what we are going to address first. To help us get more power, we turned to our friends at GReddy who supplied us with their new Evo 3 exhaust for our evaluation.  We chose the Evo 3 because of its large 70mm piping diameter.  Although this might not be the optimal diameter for our initial basic bolt ons, we have big plans for Project FR-S in the future and we wanted something with a lot of flow potential. 

We were a little worried that the big tubing might cause a loss in gas stream velocity and hamper low end power on the little 2 liter boxer engine but read on to check out our test results.

For More on Project Scion FR-S click here!

The Evo 3 features quality all stainless steel construction.  The tail pipe section consists of a smooth flowing merge to twin rear exhausts.  The mufflers are perforated core straight through absorption type for excellent flow.  These types of mufflers are loud and the Evo 3 comes with dual butt plugs, restrictors which help quiet things down.  On our small engine they did not hurt power but if you were rocking forced induction or NOS, you would want to leave them out for best power output.
To reduce costs, Greddy uses robotic welding in areas that are not easily seen.  Although it is not as beautiful as hand TIG welding done by a skilled operator, robotic welding is functionally fine and a good way to reduce costs to the customer.  The large 70mm mid pipe also uses a perforated core pre-silencer to reduce high frequency resonance.
Our exhaust came with decent quality zinc plated hardware and OEM quality gaskets.



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Thursday, November 15, 2012 7:27 AM
what are those rectangular cards or targets right in front of the exhaust cans on the suspension on the top pic on page 3?
Thursday, November 15, 2012 10:51 AM
Just out of curiosity, what made you go with Greddy over something like Perrin? I've been following their blog on how they are designing their parts and it looks like their stuff does really well.
Mike Kojima
Mike Kojimalink
Thursday, November 15, 2012 11:31 AM
The rectangular things are brackets for our rear diffuser.

If you read the article, it tell you that we chose the Greddy because of it's large tubing diameter which will better support things that we have coming in engine development.

Also at the time when we started this project, there were not as many choices for exhaust systems. We still would have went with Greddy due to the 70mm pipe diameter though.
Der Bruce
Der Brucelink
Thursday, November 15, 2012 12:27 PM
Nice to see some power levels increasing right off the bat ;-)

Now, I thought the Toyobaru ECU needed a little help from the likes of Eric and the homeboys over at COBB to really utilize mods? PS, I don't think Justin mentioned the Motoiq FR-S running the GTA...........?????
Thursday, November 15, 2012 4:39 PM
I like the touch of hollow hangers, except that its weight savings is entirely defeated by the exhaust splitting into 2 at the end, the pipe diameter looks the exact same as the single, which means its not necessary at all to exit into 2, that section of pipe and second muffler adds far more weight than having solid hangers ever would...
Thursday, November 15, 2012 6:09 PM
Anyone know the science of what it is exactly that causes the power increase with a larger diameter exhaust? Yea, Yea, I know better flowing. The motor's an air pump and if you give it bigger pipes its able to pump more air and hence more power. But beyond that simple description what exactly is the cause of that power increase. I'm just wondering because I think tuning is done rather hap hazardly for street cars. Sure in things like F1 its highly scientific. I was just wondering whether I don't know a more rigorous scientific approach to tuning street cars could be done.
Thursday, November 15, 2012 6:41 PM

Most of the power gains from this particular mod are going to be coming from improved scavenging of the exhaust gasses. The Greddy kit's smooth bends, better split section and all-around superior fabrication allow the exhaust gasses to flow at a higher velocity. That's why the guys where so worried about the large diameter as normally that would cause a drop in the speed of the gasses. However it seems that Greddy's good design and fabrication has managed to overcome that issue.

The faster exhaust stream creates a stronger suction that pulls the exhaust gasses from each cylinder. It also helps to pull fresh air into the cylinders during the intake/exhaust valve overlap cycle. This creates cooler, more oxygenated conditions inside the cylinders which makes each individual combustion event that little bit more energetic. Thus the engine is able to produce more torque. THIS is the more 'mysterious' action of the exhaust because improved lower-end torque is pretty surprising given the large diameter of the Greddy kit.

Improvements in top-end horsepower on the other hand come from exactly what you describe: reduced pumping losses. Its a simple increase in efficiency. The engine spends less power pushing the exhaust out and so more power is left over to drive the wheels.
Thursday, November 15, 2012 8:11 PM
I see. So what you want with a good exhaust system is one that directs the exhaust gasses in such a way that those gasses create some sort of suction effect. Less bends, smother bends, and some other stuff helps that out. In this sort of engine, given an ideal exhaust system, what sort of hp increase could be expected?
Thursday, November 15, 2012 8:17 PM
What is the most hp we could expect to gain with an ideal exhaust system is the question I'm asking.
Der Bruce
Der Brucelink
Thursday, November 15, 2012 8:25 PM
Pedro - There are so many variables to your questions, but the most HP for street cars is typically found with Turbo Charged vehicles.
Thursday, November 15, 2012 8:44 PM
I thought you were going to go with a Nameless Exhaust? Drove an FRS for the first time yesterday. It honestly felt like a 240, lol. I liked it. Still keeping the G35 Coupe though (thought of switching it out for a BRZ/FRS) and my 240 for a play thing.
Friday, November 16, 2012 12:50 AM
I completely agree with Kenkura. Dual muffler and split tubing seem a bit unnecessary, and just add weight.
I think Greddy does sell the single tip...
Friday, November 16, 2012 3:29 AM
According to the GReddy website, their single tip RS exhaust saves 13.5 lbs over the Evo3's twin exit...same 70mm piping.
Friday, November 16, 2012 7:01 AM
I don't see a lot of people buying a single tip to save 13.5 lbs, and in the process destroying the visual balance of the rear valance.
Friday, November 16, 2012 3:40 PM
Keep in mind, two mufflers should be quieter than one while not hurting power much if at all.
Sunday, November 18, 2012 3:32 PM
"and in the process destroying the visual balance of the rear valance."
Yeah...better watch out not to destroy the visual balance....omg where did we end up!?!?!
Who cares if the single muffler is a big more loud! Aren't we into sport cars?
Mike Kojima
Mike Kojimalink
Sunday, November 18, 2012 10:41 PM
At the time, this was the only Greddy exhaust available. Would still probably pick it though because it looks good to me.

Eventually we will go to a custom rear section and blow above the diffuser with it.
Friday, November 23, 2012 10:07 AM
I don't like the idea of twin mufflers on a car with a single exhaust pipe. It has always seemd a bit ricey to me. If doing it this way can cut the sound without cutting the power however it doesn't seem so bad.
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