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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain.


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Old 08-01-2012, 09:03 AM   #71
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Guess I'll have to try again. I couldn't get it to fit in that direction.

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Old 08-01-2012, 09:09 AM   #72
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Originally Posted by xjohnx View Post
I had the same question. flip it the other way around. It's counterintuitive.
Is the part sticking out supposed to face away from the engine. That's counter intuitive to me. And seems to fit, not quite perfect though

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Old 08-01-2012, 09:14 AM   #73
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Originally Posted by vtmike View Post
Is the part sticking out supposed to face away from the engine. That's counter intuitive to me. And seems to fit, not quite perfect though

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yep, that's how it fit in mine as well. been running it for 800+ miles without issue.
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Old 08-01-2012, 09:17 AM   #74
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yep, that's how it fit in mine as well. been running it for 800+ miles without issue.
Okay, good to know.

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Old 08-01-2012, 11:52 AM   #75
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Originally Posted by d1ck View Post
When you pinch off the end of a hose you're creating what's called a nozzle which reduces the cross sectional area which the water has to flow through. This is why the velocity increases. You can determine the velocity through a known opening by doing the following:

Code:
Velocity (ft/s)= Flow Rate(ft^3/s) / Area (ft^2)
However, you're not getting more flow by doing this, that literally makes no sense. Try breathing through a straw and you will know what I mean. It's much easier to breathe through your open mouth or nose which has a larger cross sectional area than a straw.

You're also creating a restriction which reduces the flow rate through the entire system system (Hose). Therefore by pinching the hose off you're increasing the velocity of the water, but also reducing the flow rate. The amount the flow rate is affected depends on the efficiency of the orifice as well as the area.

Now that you've (hopefully) learned some basic fluid dynamics you will understand why what you said has nothing to do with the increase from installing a filter.

That said, I can't explain why that happened, but I'm thinking it could be due to intake resonance which would have been designed with the filter in mind. Unfortunately I don't know anything about this field.

Alternatively it could be a simple artifact in the dyno testing and within the margin of error of the dyno. In this case it would have no significance.
Actually, Hanzo was not totally wrong.

For example, there is a reason street engines that only ever rev up 6k RPM see torque losses with a 3" exhaust. The flow area is, undoubtedly increased, but the exhaust gas velocity has decreased (this is a hypothetical mostly stock NA street car. Not turbo). On the same token, though, a Honda S2000 would probably see some gains by running a 3" exhaust on an otherwise mostly stock setup. At 9k RPM, the engine does not need velocity in the incoming and outgoing air as much as it needs sheer volume in and out.

The same goes for the intake side. A late 80s/early 90s Mustang 5.0 would have smaller diameter and longer intake runners in the manifold than, say, a Honda VTEC motor. With a 5.5k RPM redline, the 5.0 needs, desperately, to keep the incoming at a higher velocity to make any kind of power.

The inner diameter of the intake runners determines what RPM peak horsepower will occur, and the runner length moves the power band around...If the diameter is tuned for peak hp at 7.5k RPM, then longer runners will give you a broader power band up to 7.5k RPM and then the engine will fall flat on its face, whereas shorter runners will make power at or past 7.5k RPM, with consequential loss in power the lower revs.

Also, this may not necessarily account for the findings of filterless vs with a filter gains, but this is how engines work. Increasing flow area, more often than not, actually decreases the engines flow characteristics.

Last edited by DSR2409; 08-01-2012 at 12:22 PM.
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Old 08-01-2012, 01:52 PM   #76
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Quote:
Originally Posted by vtmike View Post
Is the part sticking out supposed to face away from the engine. That's counter intuitive to me. And seems to fit, not quite perfect though

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Yeah I had the same issue with my aFE, I spent about 10 minutes trying to figure out how to shoehorn it in the other way and could never get the box closed... The aFE says "front" on it but has no installation directions and the front actually faces towards the windhshield, not the front of the car.
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Old 08-01-2012, 01:57 PM   #77
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yeah you want the sticking out part facing away as those grooves increase the surface area of which air can run through
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Old 08-01-2012, 02:15 PM   #78
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So which is best sounding and gives best results as far as HP? Looking to buy one.
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Old 08-01-2012, 02:22 PM   #79
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Regarding the K&N drop in filter, there are tons of discussion at every car forums that everyone said NO GAIN in HP/TQ and performance until I see this dyno graph right here. So, there is some gain about 5hp which is a prove in increasing in HP. I have used K&N filter on my other cars for the past 10 yrs at one time cost. It's a good deal for an easy mod.

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Old 08-01-2012, 02:34 PM   #80
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What I want to know; which of these filters actually filters the air best???
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Old 08-01-2012, 03:40 PM   #81
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Quote:
Originally Posted by DC-FRS View Post
So which is best sounding and gives best results as far as HP? Looking to buy one.
As far as results go, each filter generally performed the same.

The sound of each filter didn't really vary either. It is all just an increase in engine noise. Each filter is slightly louder than the stock exhaust and all sound great still!

Really, it is all down to a matter of preference for these filters

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What I want to know; which of these filters actually filters the air best???
I am not sure on that, but can assure you each filter will do no harm to your engine. I am sure contaminants are down to a factory tolerance on all these filters.
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Old 08-01-2012, 04:34 PM   #82
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I think I will order the HKS filter...just because it is a sexy green. Is it reusable like the K&N?

A good filter can make HP. It is easy to understand how and thus, I am always confused when people argue against them.
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Old 08-01-2012, 06:21 PM   #83
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Originally Posted by DSR2409 View Post
Actually, Hanzo was not totally wrong.

For example, there is a reason street engines that only ever rev up 6k RPM see torque losses with a 3" exhaust. The flow area is, undoubtedly increased, but the exhaust gas velocity has decreased (this is a hypothetical mostly stock NA street car. Not turbo). On the same token, though, a Honda S2000 would probably see some gains by running a 3" exhaust on an otherwise mostly stock setup. At 9k RPM, the engine does not need velocity in the incoming and outgoing air as much as it needs sheer volume in and out.

The same goes for the intake side. A late 80s/early 90s Mustang 5.0 would have smaller diameter and longer intake runners in the manifold than, say, a Honda VTEC motor. With a 5.5k RPM redline, the 5.0 needs, desperately, to keep the incoming at a higher velocity to make any kind of power.

The inner diameter of the intake runners determines what RPM peak horsepower will occur, and the runner length moves the power band around...If the diameter is tuned for peak hp at 7.5k RPM, then longer runners will give you a broader power band up to 7.5k RPM and then the engine will fall flat on its face, whereas shorter runners will make power at or past 7.5k RPM, with consequential loss in power the lower revs.

Also, this may not necessarily account for the findings of filterless vs with a filter gains, but this is how engines work. Increasing flow area, more often than not, actually decreases the engines flow characteristics.
What you're talking about is related to the air flow being laminar or turbulent. This is where the myth of "backpressure" comes in.

Basically, for any engine you want the intake and exhaust velocity to be as high as possible at all times. However, once the gas reaches a flow rate where the flow becomes turbulent the friction losses increase significantly. The turbulence of the gas is measured by using something called a reynolds number.

Any ways, getting back to the backpressure myth. Basically, a smaller exhaust will have high velocity laminar flow at a lower engine speed than a larger exhaust. (High velocity exhaust flow is good for scavenging, while high velocity intake flow is good for cylinder filling.) That means the exhaust will be more efficient at lower RPM, but will choke off the engine at high RPM. Likewise, a larger diameter exhaust will have high velocity, laminar flow at a higher engine speed. This will increase peak power. However, this larger exhaust will have a lower exhaust gas velocity at lower engine speeds. This will reduce the scavenging effect.

The situation in the intake is very similar. Smaller ports (intake and head) will be most efficient at lower engine speeds, but when the flow becomes turbulent the friction losses will increase, decreasing cylinder filling.

This is why the 5.0L mustang has such small ports. Low RPM coupled with lower power levels and 8 cylinders mean there's not much air flowing into each cylinder. When tuned for this the intake runners will be small diameter. If you were to modify that engine to much higher levels you would want to increase the diameter of the ports to allow laminar flow of the increased air volume.

I believe the length of the intake runners has more to do with the resonant frequency of the cylinder pulses which happen in the intake as the valves open and shut. When tuned to the proper frequency the pules will experience constructive interference which will increase the intensity of the pulse as the valve opens. This also affects cylinder filling.

To be honest I can't see how having a filter in will increase horsepower do to air velocity. This is because immediately after the air passes through the air filter it's going to enter the back of the airbox which has a very large cross sectional area. This decreases the air velocity until it begins to enter the rest of the intake where the area reduces and the are velocity will increase again.
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Old 08-01-2012, 07:33 PM   #84
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5 hp gains from drop-ins on a non-boosted four banger? Seems a bit optimistic. And yet these guys get a free pass...double standards much?
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