I figured out how to dyno a quattro on a 2 wheel drive dyno :) (long post!)
01-13-2001, 01:14 PM
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I figured out how to dyno a quattro on a 2 wheel drive dyno :) (long post!)
<center><img src="http://pictureposter.audiworld.com/10966/haldex.jpg"></center><p>OK. i think i figured out how to dyno a TT quattro on a 2wd dyno 
First, some background on the Haldex system used in our TT's which i obtained from Haldex's website:
"The unique design of the Haldex LSC comprises three functional parts:
- The hydraulic pump driven by
- the slip between the axles/wheels.
- The wet multi-plate clutch.
- The controllable throttle valve
- with its electronics.
The unit can be viewed as a hydraulic pump, where the housing and an annular piston are connected to one shaft and a piston actuator connected to the other.
The two shafts are connected via the wet multi-plate clutch pack, normally unloaded and thus transferring no torque between the shafts.
When both shaft are rotating at the same speed, there is no pumping action. Immediately as a speed difference occurs, the pumping and starts to generate oil pressure. As a piston pump there is virtually instant reaction with no low speed pumping loss.
The oil flows to a clutch piston, compressing the clutch pack, braking the speed difference between the axles. The oil returns to the reservoir via a contollable throttle valve, which controls the oil pressure and the force on the clutch package.
In traction/high slip conditions a high pressure is delivered, while in tight curves, i.e. parking, or at high speeds a much lower pressure is provided."
OK...now after reading this and some other technical information, it got me thinking....
maybe i can disable the Haldex unit so that it won't transfer power to the rear wheels. There is a connector to the unit that provides power and data communication with the rest of the car. I thought to myself...disconnect this...and no 4wd...
so while doing research on this i came across someone who works for Haldex Traction. He is a software engineer and was involved with developing the software that controls our haldex units...so i emailed him about my theory and this was his reply to me:
"There is an electrical pump inside the unit, building a base pressure which is necessary for the unit to work. Without power supply, there will be no base pressure, and therefore no torque transfer. This is why a car with the Haldex AWD system can be towed with one axle in the air. So, if you disconnect the Haldex unit at the connector, you will have no AWD function and should be able to run your 2WD dyno.
Note that when you disconnect the Haldex unit, the ESP unit (if present) will probably scream (turn on a warning light and probably set an error code). From what I know, this shouldn't be any problem, since you hopefully will not need ESP while on the dyno.... Once you connect the Haldex again, you will have back both AWD and ESP functionality. There may be an error code left in the ESP error memory (I do not know), but that should not cause you any problems."
So folks..i'll probably be the first one to test my theory as soon as i get a chance...disconnect the power supply to the Haldex unit and strap her down to the dyno!
Rukman
First, some background on the Haldex system used in our TT's which i obtained from Haldex's website:
"The unique design of the Haldex LSC comprises three functional parts:
- The hydraulic pump driven by
- the slip between the axles/wheels.
- The wet multi-plate clutch.
- The controllable throttle valve
- with its electronics.
The unit can be viewed as a hydraulic pump, where the housing and an annular piston are connected to one shaft and a piston actuator connected to the other.
The two shafts are connected via the wet multi-plate clutch pack, normally unloaded and thus transferring no torque between the shafts.
When both shaft are rotating at the same speed, there is no pumping action. Immediately as a speed difference occurs, the pumping and starts to generate oil pressure. As a piston pump there is virtually instant reaction with no low speed pumping loss.
The oil flows to a clutch piston, compressing the clutch pack, braking the speed difference between the axles. The oil returns to the reservoir via a contollable throttle valve, which controls the oil pressure and the force on the clutch package.
In traction/high slip conditions a high pressure is delivered, while in tight curves, i.e. parking, or at high speeds a much lower pressure is provided."
OK...now after reading this and some other technical information, it got me thinking....
maybe i can disable the Haldex unit so that it won't transfer power to the rear wheels. There is a connector to the unit that provides power and data communication with the rest of the car. I thought to myself...disconnect this...and no 4wd...
so while doing research on this i came across someone who works for Haldex Traction. He is a software engineer and was involved with developing the software that controls our haldex units...so i emailed him about my theory and this was his reply to me:
"There is an electrical pump inside the unit, building a base pressure which is necessary for the unit to work. Without power supply, there will be no base pressure, and therefore no torque transfer. This is why a car with the Haldex AWD system can be towed with one axle in the air. So, if you disconnect the Haldex unit at the connector, you will have no AWD function and should be able to run your 2WD dyno.
Note that when you disconnect the Haldex unit, the ESP unit (if present) will probably scream (turn on a warning light and probably set an error code). From what I know, this shouldn't be any problem, since you hopefully will not need ESP while on the dyno.... Once you connect the Haldex again, you will have back both AWD and ESP functionality. There may be an error code left in the ESP error memory (I do not know), but that should not cause you any problems."
So folks..i'll probably be the first one to test my theory as soon as i get a chance...disconnect the power supply to the Haldex unit and strap her down to the dyno!
Rukman
01-13-2001, 02:20 PM
#2
My service tech. told me an easier way to disable the Haldex...
Lift the parking brake a notch or two, until the light comes on.
The Haldex is then disabled.
It's not engaging the rear parking brakes yet.
He sez the "kids" do this to get the front wheels to spin and smoke.
The Haldex is then disabled.
It's not engaging the rear parking brakes yet.
He sez the "kids" do this to get the front wheels to spin and smoke.
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