Aircond compressor and RPM
#1
Aircond compressor and RPM
Just to share a myth/fact that ive heard ever since i drove a car.
Is it true that wenever u choose to WOT, u have to switch off the a.c first to avoid the compressor from being damaged. With my older cars, wenever i switch the a.c after i drive, the compressor screeches. But never had this experience with the Lex. I do know for a fact that it robs HP wenever u switch on the a.c but then again i dont know wat advances are made regarding a.c in cars.
Anyone can enlighten me over this coz the price of one compressor is unbelievable for the IS.
Is it true that wenever u choose to WOT, u have to switch off the a.c first to avoid the compressor from being damaged. With my older cars, wenever i switch the a.c after i drive, the compressor screeches. But never had this experience with the Lex. I do know for a fact that it robs HP wenever u switch on the a.c but then again i dont know wat advances are made regarding a.c in cars.
Anyone can enlighten me over this coz the price of one compressor is unbelievable for the IS.
#2
The A/C compressor in the IS is a variable displacement design. It uses some clever engineering that increases or decreases the piston's stroke on-the-fly. By changing the displacement, it is able to vary both cooling capacity and engine load from full capacity to near zero. Under heavy engine load such as WOT, the computer simply reduces the displacement of the compressor to reduce parasitic load on the engine -- no need to switch it off.
Incidentally, the variable displacement design is why you don't hear the compressor cycle on and off, and why leaving it on has a minimal effect on fuel mileage during mild weather.
Incidentally, the variable displacement design is why you don't hear the compressor cycle on and off, and why leaving it on has a minimal effect on fuel mileage during mild weather.
#4
When one of the car magazine (R&T?) tested the IS350 on a scorching S. CA day they noted that the A.C. doesn't make very much cold air at WOT. Which jibes with what Bichon said. And all that wonderful technology undoubtedly makes the compressor more expensive.
#5
I remember my buddy telling me that his 1994 Supra has a OEM feature that shuts off the compressor while you are nailing it or Wide Open Throttle. It then engages back when the computer senses a lower RMP. Not sure if the gen 1 IS has this for the OP. I never noticed it on the gen 1 in my 4 years of ownership, but then again, it was not the turbo (2JZGTE) but rather (2JZGE).
#6
Ahhh the wonders of engineering. Great info now i dont have to worry about switching it off again. At least the price is now justified and i dont have to worry wenever i floor it. I guess the sweat from the hot afternoons really didnt improve my mileage LOL.
Thanx for the info.
Thanx for the info.
#7
The original poster has a 2IS. The IS300 is a current model in his country (Brunei): http://www.lexus.com.bn/lexus_cars/i...s300/index.asp
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#8
The original poster has a 2IS. The IS300 is a current model in his country (Brunei): http://www.lexus.com.bn/lexus_cars/i...s300/index.asp
Type 3.0 liter V6 Four Cam 24-Valve (3GR-FE)
Piston Displacement 2995
Maximum Output (kW/rpm) 170(228bhp)/6400
Bore x Stroke (mm) 86x86
Maximum Torque (Nm/rpm) 300Nm/4800rpm
Fuel System Electroninc Fuel Injection
#9
Kind of a dissapointment in HP though for a larger displacement. Thanks for the post.
Type 3.0 liter V6 Four Cam 24-Valve (3GR-FE)
Piston Displacement 2995
Maximum Output (kW/rpm) 170(228bhp)/6400
Bore x Stroke (mm) 86x86
Maximum Torque (Nm/rpm) 300Nm/4800rpm
Fuel System Electroninc Fuel Injection
Type 3.0 liter V6 Four Cam 24-Valve (3GR-FE)
Piston Displacement 2995
Maximum Output (kW/rpm) 170(228bhp)/6400
Bore x Stroke (mm) 86x86
Maximum Torque (Nm/rpm) 300Nm/4800rpm
Fuel System Electroninc Fuel Injection
As for why they released it that way, I believe it's because the fuel quality in China, Brunei, the Middle East and other markets where the car is sold is inadequate for direct injection.
#10
The reason the power bump is unimpressive relative to the IS250 available here is because the engine in the 2nd gen IS300 has port fuel injection instead of direct injection. (At least the folks in Brunei won't be complaining about the loud ticking at idle. ) That same engine, equipped with direct injection, put out 245 horsepower when it was offered in the '06 GS300.
As for why they released it that way, I believe it's because the fuel quality in China, Brunei, the Middle East and other markets where the car is sold is inadequate for direct injection.
As for why they released it that way, I believe it's because the fuel quality in China, Brunei, the Middle East and other markets where the car is sold is inadequate for direct injection.
#11
I remember my buddy telling me that his 1994 Supra has a OEM feature that shuts off the compressor while you are nailing it or Wide Open Throttle. It then engages back when the computer senses a lower RMP. Not sure if the gen 1 IS has this for the OP. I never noticed it on the gen 1 in my 4 years of ownership, but then again, it was not the turbo (2JZGTE) but rather (2JZGE).
#12
#13
The reason the power bump is unimpressive relative to the IS250 available here is because the engine in the 2nd gen IS300 has port fuel injection instead of direct injection. (At least the folks in Brunei won't be complaining about the loud ticking at idle. ) That same engine, equipped with direct injection, put out 245 horsepower when it was offered in the '06 GS300.
As for why they released it that way, I believe it's because the fuel quality in China, Brunei, the Middle East and other markets where the car is sold is inadequate for direct injection.
As for why they released it that way, I believe it's because the fuel quality in China, Brunei, the Middle East and other markets where the car is sold is inadequate for direct injection.
#14
You are mistaken. The IS250 does have direct injection. It has a 4GR-FSE engine, where the "SE" suffix means direct injection. (And a forum search for "ticking noise" will turn up dozens of posts from IS250 owners concerned about the sound of their injectors)