Only thing I would change right away is the silver mustache.

 

Very quite but it was a Sunday drive on the track I could not even hear the turbos! I am very glad that I have 6.2 liter rather than 4.0 TT for the sound and it is a much better platform and motor.

 

I'm not telling people to hack up a new car and violate law
You are
That is pompous ego lol

A doctor, teacher, lawyer, etc need a license
A dog needs a license
You need one to drive a car
But not to modify legally mandated systems that have various regulatory approvals
A projectile at 150 mph that possesses 3.2 million ft-lbs of kinetic energy
Plus the energy in the stored fuel

In Germany all mods are submitted by engineers for certification by the TUV a national agency
After they are installed a certified shop must inspect to verify the have been installed per the approved cert

Here any schmoe can 'engineer' a car lol
It would be amusing if not so potentially dangerous

 

You're CERTIFIABLE sir wow! Even when given undeniable facts that refute all your demands of legitimacy... You bark back w/utter jibberish & add more krap to try & justify your ramblings yet again.. Whatever helps you sleep at night

PS what happened to this post, from 2 days ago? Time to take your own advice & save yourself further embarrassment..

 

Your anger shows
No need for calling people mentally ill, it is a real problem for many and their families

You have provided no 'facts'
You said to remove the entire system and replace with straight pipes
In violation of numerous laws

You get 'embarressed' over stuff like this?
I'm sure we have enough foibles in real life to suffer shame over lol
But better to address them than lament and feel guilt
Simmer down Sally it is all good

 

The less amount of work/pressure the turbine section has to fight against to evacuate exhaust gases, the more efficient the set-up and larger power gain. Same deal with the pressure drop in the intake manifold / across intercooler, etc.

Car is not in boost all the time so obviously some trade-off wrt back pressure needs to be made, however most OEM systems are not engineered with efficiency in mind (and in the instance of Mercedes, luxury) and more in line with providing a quieter sound than an off-road only setup.

 

Excellent post

 

As long as the system was designed for a given pressure
The ecu, the turbo, the control system
Less is not always better and usually worse if the system was not designed for it

Most oem systems optimize all parameters
What is the pressure drop of a hipo oem exhaust? 3 psi range
Obviously press drop ~ (Q/area)^2
Difficult to get much lower
What is the exhaust pressure? Similar to the mean eff cyl pressure?
Proportional to the comp ratio?
Both are >>> exh press drop
The largest press drops in the system
Throttle
Intake/exh valves
Frictional losses are moot

If taking the exhaust off did allow the turbine to do more work, it doesn't, it may lose power due to an inefficient operating point or heat of compression

A turbo car with no back press will run like crap on the street
And this is a street car
The turbine must work into a load, think of it as dampening or system capacitance
I read my first text on turbos in a class I took in the 80's
I work with them regularly
Completely remo ing the exh and emission system will hurt performance, drivability and is illegal

 

Assume exh pressure is 100 psi
And exh press drop is 5 psi
So the turbine can do 95 psi of work/compression
Reducing the exh to 0, it now does 100 psi assuming the turbine can use it
Since it is a centrifugal machine it does the sq root of 5% more work or 2.5%
10 psi of boost is now 10.25 minus losses and losses due to heat of compression
Basically nothing
But the turbo uses less than 95% eff and exh dp is less than 5 and can't be reduced to 0

The work the turbo does is mass dependent but press is easier to comprehend
The gas is also compressible so not as sensitive to press drop as a imcompressible liquid

Even if you could build more boost the wastegate will limit it
On this car prgramming will yield more than removing the exhaust
As long as one stays within the devices sweet spot

 

You can run your 1950's mathmatical turbo theory calculations all you want geezer.. But when removing CATS or replacing w/HIFLO CATS & down pipes, it SUBSTANTIONALLY IMPROVES turbocharged cars performance across the board in both HP/TQ & THROTTLE response and SOUND, AFTER being optimized w/AFTERMARKET DYNO RETUNE for said modifications etc etc

EVERY TOP TUNER IN THE ENTIRE WORLD DOES THIS INCLUDING MERCEDES AMG ON THEIR GT RACE CARS... It works on STREET CARS TOO! It doesn't ruin drivability or power delivery.. Quite the opposite.. You need a time out before you have stroke rambling on about PROVEN PERF mods you CLEARLY know nothing about

 

It's from the 1700's
The laws of thermodymics
They have not been repealed
No need to get upset and sling insults child lol

Anyone who thinks that the turbine adds energy/force to the exh stream to help propel/accelerate it does not have the tools to understand the machines operation
It would take external energy like a shaft motor to do so
The exh can't increase its total energy after it leaves the cylinder lol
The energy comes from the exh stroke which is powered by inertia and corresponding power strokes, not to mention expansion due to combustion

I still do not agree with
Removing the entire exh system
Violating federal and state law
And definitely not with violating the laws of physics

Do you even know how a turbine works?
Slow gas path and long one causing a diff press across the blades
Much like lift but constrained so the pressure rotates it
The inverse of a pump or the compressor side
Ever hear of a geezer named Newton or Bernoulli? Lol

 

In the instance of lowering turbine outlet pressure, Less *is* always better. Higher pressure differential between inlet and outlet = more work on the turbine, in turn driving the compressor and resulting in faster spool, greater area under curve and so on.

Using your 100 psi example, if a restrictive exhaust introduced 5psi of backpressure, then the cumulative pressure is 105. Pressure differential as explained above increases and power drops off as a result.

Pressure drops (read: restrictions) pre-inlet are bad (intake, intercooler, intake/exh valves, manifold. The whole point is to build up as much pressure as possible increasing the pressure drop across the turbine.

It will do more work. With increased pressure ratios the turbine caps out at a pre-determined efficiency (glance at any turbine map will confirm this). It's not like the compressor which needs to stay within a certain island of efficiency, and even then that central island allows for a good 10 psi / 50HP of leeway on average before compressor efficiency drops off.

 

Sigh it's the Ideal Gas Law not the original four laws of Thermodynamics. Please get the corresponding law right

 

No it isn't
Although it applies to the combustion cycle

http://link.springer.com/chapter/10....-642-27518-0_2

Thermodynamic Characteristics
Some essential thermodynamic characteristics of gases are needed to know in the turbocharging. They have been usually applied to the turbocharging of engines, where the charge air and exhaust gas are assumed as compressible ideal gases.

The gas is assumed to conform to the ideal
The math/physics are the area of thermodynamics
Just like you have statics and dynamics for mass/motion/etc

 

Lol wait for it..................... Wait for it........................ Old man ranting in 5-4-3-2-1...

Lol a scorchingly fast 2 min record from Turbo-Tard....

 

LOL...

I am tired of for today and will move on to next topic now...

 

Lowering the discharge press drop is not always better
Most cases worse unless many other changes are made
And with stock turbos maybe not even then

If exh press is 100 it can't be higher
It is deductive due to losses
100 at the valve
10 in losses to the turbo
Say 80 across the turbo
10 in the exhaust
0 at the exh tip ( actually a bit of residual vel press)

The eff point on a compressor chart is a circular region
If you spool it beyond that region you may lose power
That is why they change turbo size
If it is at its optimal point it can't do more work, eff decreases
A properly sized turbo does not have 10 psi of headroom
Beyond a certain point all the turbo does is add back pressure not power

 

Sounds like I have emotional control over you
I don't want it lol
Do you hate older people?
How about your parents? Grandparents?

You don't need to worry about getting old though
Darwin
Or more likely with your attitude someone will punch your clock
Enjoy your mediocrity

 

One more shot to illustrate why replacing an oem hipo exh (AMG, M, Quattro) is ,in my opinion, pointless or detrimental. Modern systems made by suppliers like Arvin-Meritor and others are efficient, both in power production and fuel efficiency, which in this case are mutually inclusive. I need to use math, I know people hate it, but it illustrates much more succinctly than words if you can 'read' the language.

P drop for a typical modern oem hipo exh system:
NA 3 psi AT REDLINE
FI 2 psi (cats are the same as is piping since fuel mass/exh Q is the same for a given power output, but the muffler can be a bit smaller)
Drop is ~ to the square of Q and Q ~ power/torque
We'll evaluate at 80% of redline (7000 rpm, evaluate at 5600, basically mid-point of T and P). To use redline is silly since <1% of the operating time is >90% redline.

Assumptions:
atm P 14.7 psi
pressure ratio 2.2 ~ 18 psi boost (similar to the AMG and M)
oem exh drop at redline 2.5 psi
a/m drop 1 psi (remove cats, resonators, muffler and increase pipe size 20%)

oem:
exh P drop at 80% redline = 0.64 x 2.5 = 1.4 psi
inlet pressure = 2.2 (14.7+1.4) = 35.4 psi
psig (or gauge/abs) = 20.7
exh portion 1.4
turbo drop 19.3

a/m:
exh P drop at 80% redline = 0.64 x 1 = 0.64 psi
inlet pressure = 2.2 (14.7+0.64) = 33.8 psi
psig (or gauge/abs) = 19.1
exh portion 0.64
turbo drop 18.5

Result: less than 1 psi advantage, assuming it can be utilized if the ECU/boost control is modified...it does increase VE a bit also, but really moot
probably not measureable on a ramp dyno, perhaps a few HP on a steady state one, will be lost in the noise for timed runs...

disadvantages:
streetability/driveability
fuel economy
fuel smell/fumes (don't start it and idle in a garage with a gas water heater lol)
power may actually decrease depending on ECU mods
cost
legality
sound: loud, booming, drone, not sonorous or tonal (no muffler remember?) and legality re: noise ordinances

advantages:
can't think of any

This does not consider the turbo selection, operating region, etc., only the exh system influence.

This is not to say if the exh system is highly restrictive or malfunctioning replacing/repairing it won't bring back the choked/lost power, but on a system like the AMG's (or M, quatttro, etc.) there is no advantage. This is why you seldom see gains with cat back systems, and may see power and/or torque loss. The oem are that good now.

It's your $$$, no skin off my nose, no dog in this fight, but these mods are generally better for the seller than the buyer, hey I'm a capitalist/consumer, I know the game and have no issue with it, but be informed, by being so the market improves the product. If you significantly increase exh Q by bigger turbo or displacement increase it may be worth considering, but if power gain is less than 25% (4 to 5 psi of net manifold pressure/boost) or so, no real need imho. The reason being Q has increased so much friction loss in the pipe may become a factor near redline. But either way only a few percent are gained: but at a cost, nothing is free, everything is a compromise or trade-off.

I know there are varying opinions, these are mine, I hope I conveyed my reasoning.

thanks, sorry, peace, etc

 

I said 10psi of leeway not headroom. Also, go look at the compressor maps for gt30, gt28, etc. Calculate from the middle island (Pressure Ratio around 2 (14.75). You clearly have another .5 PR (7.375 psi) in each direction before dropping off the central island.

2.5PR = 22.125 psi
1.5PR = 7.375 psi

These turbos are more in line with the power our cars are putting out, so don't want to hear about TD05, GT25, etc.

 

Redline is not silly, if PSI drops off at redline then there is a flow limit. Higher outlet pressure at redline = lower pressure differential and less work/boost done by the turbocharger.

1 psi only is generous at best, using 2.5psi restriction for an OEM system. I tend to think that would be a higher number. Even a 2psi increase is easily a good amount of power, and you are neglecting the advantages that occur on the compressor side from this change. 250-500RPM earlier spool translates into greater responsiveness and area under the curve from a power perspective.

If people want to run a straight pipe, so be it. I actually did this for a few months then the noise got to me after a while. No fun driving around with the windows up. Plenty of backfires though

 

It is less than 1 psi
With losses closer to 0.5 psi, a few % increase in torque
Providing the fuel and boost control are modified
On a turbo set-up closer to 2 psi drop not 2.5 which takes it below 1/2% torque increase
Negligible

NA are getting below 3 psi drop
Arvin-Meritor posts the numbers
The old e46 M3 header back was less than 3 excluding the header
300 mbar from head to tip 4.4 psi including the header!!!
the headers were >1.5 psi alone
At 8000 rpm
At 4000 1.1 psi including headers to tip

As I said it's your $$$

A good deisel set up is getting 30" WC
That is a little > than 1 psi
With catalyst, muffler and DPM