Turbo & restrictor
Turbo & restrictor
(OP)
Hello. How restrictor on turbocharger changes power and torque? In my opinion, restrictor increase air flow speed in turbo and decrease pressure (venturi effect), so ammount of air will be the same because speed was increased or not? And why on high rpm power drops with restrictor on turbo?
Thank You for answers
Thank You for answers





RE: Turbo & restrictor
Mike Halloran
Pembroke Pines, FL, USA
RE: Turbo & restrictor
RE: Turbo & restrictor
A "restrictor" serves the function of reducing flow, and nothing else.
Putting a "restrictor" in front of a turbo compressor with the sole function of being a pressure-drop device, so that the turbo has to work harder, at a higher pressure ratio which means it has to spin faster to achieve a given boost pressure, is never going to be a good thing to do. NEVER.
RE: Turbo & restrictor
RE: Turbo & restrictor
That is required by the rulebook for LIMITING the power. The rulebook somewhere will require that all of the engine's intake air has to be drawn through something with either X mm diameter or X square millimeters in area (I don't know what X is, it is "a number").
It's a rounded venturi shape because that minimizes the restriction. It's right at the turbo inlet because that's where the effect of that restriction is "least bad".
But make no mistake, that engine would make more power and be capable of higher boost and would be less prone to blowing up the turbo if that thing were removed and the diameter of the turbo intake duct were no smaller than the diameter of the turbo inlet itself.
It only exists because the rulebook requires it to be there. It's a nice, rounded, aerodynamic shape because minimizing the "bad" effects of what the rulebook says they have to do, is what race engineers do.
RE: Turbo & restrictor
http://www.sonicperformance.com.au/productimages/8...
RE: Turbo & restrictor
RE: Turbo & restrictor
I.e., there may be some actual technical function associated with the features pictured, or they may be a marketing function.
Mike Halloran
Pembroke Pines, FL, USA
RE: Turbo & restrictor
The restrictor "caps" air massflow at the choked flow value and essentially makes these "constant power" engines ie very flat power curve - falling gradually with rpm as friction and airflow (VE) losses increase.
je suis charlie
RE: Turbo & restrictor
RE: Turbo & restrictor
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Turbo & restrictor
That is a load of crap. Unless the car is operating at high speed and has a functional aerodynamic intake scoop, the only driving force causing air to flow through the restrictor is the pressure difference created by the turbo. Engine torque is proportional to mass flow, and for a given mass flow, a larger pressure difference will be required with the restrictor present. This means the turbo will be operating at a higher pressure ratio, and using more energy, creating backpressure and limiting output. Velocity of the airflow through the restrictor is irrelevant.
I think what this article is missing is this:
For a given engine, with a given maximum intake pressure limitation, there exists a certain size of turbocharger that will produce maximum peak horsepower. This configuration will have reduced low end torque due to the inefficiency of the large turbocharger at low mass flows. Let's say for argument sake on a given car that this 'optimal' turbo has a 67mm inducer.
If we then make a rule that this engine must be fitted with a 50mm restrictor near the turbocharger inlet, the 67mm turbo will go in the trash and we will fit something with a 50mm inducer, or maybe slightly larger. Now we have a smaller, faster spooling turbo which will make much more low end torque but run out of steam at high mass flow rates. We will make more low end torque, but much less peak power. For a high revving engine, this could in fact mean that peak torque is increased but peak power decreased.
In other words, the increased torque is not due to the restrictor, it is because the restrictor forces the team to fit the engine with a smaller turbo.
RE: Turbo & restrictor
No, the inducer will not be smaller, in fact for a given power output (same massflow), the restricted engine will need a larger inducer since the compressor intake air density is lower.
je suis charlie
RE: Turbo & restrictor
The reference being discussed clearly states 40% drop in peak power.
RE: Turbo & restrictor
. . . and in that context I would assume they are referring to a given engine and turbo combination with restrictor added. Funny (I just did the calculation) a choked adiabatic restrictor produces a 40% drop in air density.
je suis charlie
RE: Turbo & restrictor
Hi, i find out for what reason this holes are in turbo's, it's "anti-surge" or "ported-shroud" housing.
"A Ported Shroud compressor is a feature that is incorporated into the compressor housing. It functions to move the surge line further to the left by allowing some airflow to exit the wheel through the port to keep surge from occurring. This provides additional useable range and allows a larger compressor to be used for higher flow requirements without risking running the compressor into a dangerous surge condition. The presence of the ported shroud usually has a minor negative impact on compressor efficiency."
http://www.turbobygarrett.com/turbobygarrett/surge...