Magnaflow Employee on the IS350 exhaust

[JBrady]

Just found this post. Very good information and worth learning.

http://www.clublexus.com/forums/showthread.php?t=258720&page=2

"OK- Ill shed some light on the subject- I work for Magnaflow-

1. For the most part, dynos are fun, but they dont tell you much unless the dyno shop has paid the big money to create an actual controlled environment-

Some of the variables that need to be taken into consideration are-

1. Head temperature- most dyno shops dont check
2. Coolant temperature- most dyno shops dont check
3. Oil temperature- most dyno shops dont check
4. humidity
5. air temperature

Our R&D center can actually change dyno results on a 200hp car by as much as 4-5 hp just by manipulating head temperature and collant temperature-

Heat soak into the heads is the biggest reason for a loss of performance-

Cars will also dyno differnent numbers at different times of the day due to humidity and temperature as well-

Also the "learning curve" of a cars computer needs to be looked at as well- as in order to effectively guage a mod, you need to let the car learn the new mod in order to fully understand how that mod effects the vehicle-

Lets look at the options for a stock IS350

1. True Dual Exhaust- no cross over
2. X pipe Dual
3. H pipe dual
4. Single Exhaust

An X pipe exhaust will outperform a true dual, or H pipe due to scavenging, so lets concentrate on single vs X pipe exhaust-

The first big factor is that due to firing order, a V6 will not take advantage of an X pipe in the same way a V8 will- hp wise- the X pipe will however provide the car with a more exotic sound quality, and will also help with interior noise-

the reason behind that is the faster acceleration of the gasses through an X-pipe causes them to flow in a linear fashion parallel to the walls of the tubing rather than tumbling. This "laminar" flowing gas is much quieter than tumbling gas, resulting in an exhaust tone up to 8 decibels quieter than a traditional H-pipe


Each one has disadvantages-

X pipe- i

ncreased friction of exhaust against pipe due to larger surface area of 2 smaller pipes compared to one larger pipe-

not enough back pressure?



Y pipe into single-

turbulences caused by forcing the two pipes into one

too much back pressure?

The first thing to consider is what kind of power to we want?

peak hp? peak tq? power under the curve?

In order to gain the most power- our goal should be to increase the total area under the hp/ tq curve by the largest amount possible-

Peak gains sound impressive and help sell product, but not if they sacrifice power in other places of the RPM range-

If product A averages 7rwhp throught the RPM range, peaking at 8rwhp gain

and Product B averages 5rwhp through out the RPM range peaking at 10rwhp

one might think B is better then A, because it has a higher peak-

however A is better then B, and in a drag race A would beat B-

After testing oh 100s of V6 motors, I can tell you based on the past-

A is a single exhaust on V6 motors

B is a dual exhaust using a cross over-

dual exhaust "might" provide a few more peak hp, but for overall gains a single is the way to go-

In fact if you look at the Nissan VQ series, you see all of these companies making "dual" kits using catch phrases like "X pipe" and so on-

But if you look at the system Nismo Japan made, its a single exhaust-

There is a good reason behind this-

Remember- Magnaflow does not make intakes, exhaust, suspension parts, exc- we spend 100% of our company resources on understanding exhaust theory-


Now I know we dont make a cat back for the IS350- however- so this doesnt apply- but for those that want to know more-


To take this a step further, in order to design a real exhaust system, you need to look at how the air flows through the muffler and design the internal preforations of the muffler on a straight through design to best take advantage-

We actually use extremely expensive testing equipment designed specifically only for exhaust that lets us look at how the exhaust pulses flow through the muffler so that we can change the size, shape, and number of preforations internally inside the muffler to make the most power, while reducing noise-

basically custom designing a muffler specifically to the car for optimal power-

OK- i think Ive bored everyone enough-"

 

[ed_ma61]

an X-pipe causes them to flow in a linear fashion parallel to the walls of the tubing rather than tumbling. This "laminar" flowing gas is much quieter than tumbling gas

X pipe- increased friction of exhaust against pipe due to larger surface area of 2 smaller pipes compared to one larger pipe

contradiction and makes no sense

i dont think any flow in any engine system, intake or exhaust, could ever be called laminar anyway?

 

[4000GT]

I seriously dont understand his point about head and coolent temps and dyno operators not checking them... you look at the engine temp to make sure its in a normal range sure, but what is he suggesting that they should be corrected if abnormally low or high?

 

[JBrady]

"Originally Posted by JBrady
an X-pipe causes them to flow in a linear fashion parallel to the walls of the tubing rather than tumbling. This "laminar" flowing gas is much quieter than tumbling gas

X pipe- increased friction of exhaust against pipe due to larger surface area of 2 smaller pipes compared to one larger pipe"


contradiction and makes no sense

i dont think any flow in any engine system, intake or exhaust, could ever be called laminar anyway?

Just for those not certain, the above quote was from my post but was NOT my quote but from the Magnaflow employee. While I agree with the general points he makes that I posted in my thread I am not globally endorsing every word or point.

Ok, on to the 2 points which I am guessing are in reverse response.

"contradiction" I am guessing would be in reference to surface area? If so then actually there is no contradiction. If you take 2 smaller pipes with a combined cross section that is equal to 1 large pipe... the large pipe will flow better. Why? As stated there is more total surface area for the 2 smaller pipes and that increases flow friction.

For simplicity lets use OD. Two 2" pipes vs. one 3" pipe. The 3 inch has 7.065 sq/in cross section and 9.42 pipe surface area. The twin 2" pipes have a combined 6.28 sq/in cross section and 12.56 pipe surface area. Less cross section but more surface area.

Regarding laminar flow I believe there are many examples in any engine along with other examples including turbulent and tumble. One obvious laminar flow would be in the MAF.

http://en.wikipedia.org/wiki/Laminar_flow

 

[JBrady]

I seriously dont understand his point about head and coolent temps and dyno operators not checking them... you look at the engine temp to make sure its in a normal range sure, but what is he suggesting that they should be corrected if abnormally low or high?

When comparing dynos that have a small difference such as say 5% (eg: 10hp on 200hp) every detail can effect the outcome. Trying to judge a single component or system (such as exhaust) with such a small difference would require everything be stabilized and equalized in order to pass judgement on the gain or loss. Engine temperature definitely will influence output and head temperature is one of the most important parts of engine temperature.

His points are valid under the conditions expressed. For anyone to "claim" a gain or loss this small without complete variable control the outcome is more marketing than science.

 

[4000GT]

Why would the head or coolent temp be any different? Every car is well warmed up before it runs at load. The normalising calculations take into account ambient temp...

 

[JBrady]

Why would the head or coolent temp be any different? Every car is well warmed up before it runs at load. The normalising calculations take into account ambient temp...

Several ways one of which you just noted. A cool engine run on the dyno vs. the same engine heat soaked after multiple pulls. Another would be changing thermostat temperature with another "mod" and concluding it was only the "mod" and not considering or disclosing the thermostat temperature change. There are of course MANY potention and malipulable variables and these can be ignored rendering the results vague or worse or they can be intentionally manipulated to "sell" a product.

 

[4000GT]

Yup, so every time you run it on the dyno it gets heat soaked after multiple runs. So the condition isnt any different between dyno sessions. Ambient temp is corrected for as mentioned...

If you change thermostat temperature its a modification like any other that changes the characteristics of the motor. If you consider that changing the thermostat makes more power (though plausibly very little if at all), then how is that different from changing the exhaust or cams?

My point is that without making a change to the motor yourself (like any other mod), and ambient temp is corrected for, there really isnt any reason it would be different from what I can see or have been told so far.

 

[ed_ma61]

wha? youve totally missed my point?

i captured/quoted two sentances which completely contradict each other. why would i be bothered to bicker about area and pipe vol etc?

the 'contradiction' to spell it out - he firstly says that X pipe is quieter due to laminar flow. then he says there is increased friction. you cant have both

if there is increased friction there will be more heat and noise. not less. if there is increase friction, there is even less chance of there being laminar flow (not that there was any chance to start with)

 

[JBrady]

wha? youve totally missed my point?

i captured/quoted two sentances which completely contradict each other. why would i be bothered to bicker about area and pipe vol etc?

the 'contradiction' to spell it out - he firstly says that X pipe is quieter due to laminar flow. then he says there is increased friction. you cant have both

if there is increased friction there will be more heat and noise. not less. if there is increase friction, there is even less chance of there being laminar flow (not that there was any chance to start with)

The friction occurs near the wall of the tubing due to the relative viscosity of the gases. Aerodynamic friction (drag) and laminar flow are definitely not exclusive. In fact the smaller the relative cross section the lower the volume required for laminar flow.

This is observable in many ways but one very good one is during the porting of exhaust ports. A turbulent port is a noisy port on the flowbench. Creating a port that flows smoothly quiets the port considerably. The resulting port is much more efficient.

A good X pipe or merge collector (as you are probably aware) has less total area than the pipes feeding the nozzle area. This creates an increase if gas speed and has many effects some of which are described above.

The aerodyamic friction is relatively quiet.

A little "rocket science" http://exploration.grc.nasa.gov/education/rocket/boundlay.html

 

[ed_ma61]

of course tubulent flow creates noise. its what it does! are you saying it doesnt? im not clear on your stance? i agree on drag not being exclusive with laminar flow - obviously.

i just dont buy the sentiment described above stating that an x-pipe, with its "faster acceleration of the gasses" causes laminar "flowing gas" despite the stated downside which is "increased friction".

theres 300 things that can explain your quiet exhaust port, boundary layer flow separation being a very likely one

 

[JBrady]

of course tubulent flow creates noise. its what it does! are you saying it doesnt? im not clear on your stance? i agree on drag not being exclusive with laminar flow - obviously.

i just dont buy the sentiment described above stating that an x-pipe, with its "faster acceleration of the gasses" causes laminar "flowing gas" despite the stated downside which is "increased friction".

theres 300 things that can explain your quiet exhaust port, boundary layer flow separation being a very likely one

Ed, I thought I was very clear about turbulence creating noise.

Laminar flow DECREASES drag per the image I posted above.

Separation of the boundary layer creates turbulence and noise so that is opposite your above statement. Or maybe you meant to say by fixing the boundary layer separation you will quiet the exhaust port?

Again, as I already described, the larger the cross section of a pipe the higher the volume required to overcome turbulent flow. This is one of the functions of a merge collector. By smoothly reducing volume you increase velocity with one goal being creating laminar flow.

The "increased friction" aka "drag" is another description of the increase in backpressure needed to accelerate the gasses.

These explanations are obviously simplified as you could get very technical if desired. I posted the above because I thought the author (Magnaflow employee) did a good job with a basic description and that saves me the trouble of doing the same.

I notice at Toymods you have recently spent substantial money creating very nice headers complete with merge collectors. I am assuming you specified those and therefore understand their advantages. Maybe we are just having trouble communicating. I don't know.

 

[JBrady]

Yup, so every time you run it on the dyno it gets heat soaked after multiple runs. So the condition isnt any different between dyno sessions. Ambient temp is corrected for as mentioned...

If you change thermostat temperature its a modification like any other that changes the characteristics of the motor. If you consider that changing the thermostat makes more power (though plausibly very little if at all), then how is that different from changing the exhaust or cams?

My point is that without making a change to the motor yourself (like any other mod), and ambient temp is corrected for, there really isnt any reason it would be different from what I can see or have been told so far.

As the engine heat soaks the internal dynamics change but this has NO effect on "ambient" air temperature. There can be some effect recorded by the engines the manifold air temp sensor but that is NOT the same as the temperature of the intake ports and inter-cylinder temperatures and dynamics. The point I believe the author was making and one of the values I found in posting it is that MANY things can effect dyno numbers and therefore dyno numbers CAN deceive.

That is certainly not to say that dynos are worthless but if someone is buying one product over another due to a relatively small increase in power it is worth considering IF this gain is REAL or CREATED with manipulation.

Some "tuners" are even unaware that the gains they THOUGHT they made were due to dyno variables and therefore do not translate into real world performance improvements. Dyno testing creates results. Without controlling ALL the variables comparisons are dubious.

Even controlling all the variables still leaves any gains or losses subject to theoretical interpretation and this so often is incorrect. An example of incorrect "theory" being big exhaust pipes and loss of low speed power. MOST jumped to the conclusion that engines somehow "NEED" backpressure for low rpm power :smashfreakB:

The actual reason is not so easily understood.