Team-BHP (https://www.team-bhp.com/forum/)

-   Technical Stuff (https://www.team-bhp.com/forum/technical-stuff/)

-   -   Air-con sucks up too much power : Maruti A-Star (https://www.team-bhp.com/forum/technical-stuff/142796-air-con-sucks-up-too-much-power-maruti-star.html)

I have noticed the problem in our 2009 A-Star vxi that when the air con compressor is turned on, the low end torque decreases drastically. Even at 45-50 kmph the car struggles in 4th gear. But without A.C. the car pulls cleanly in 3rd gear from speeds as low as 20 kmph. With A.C. even if I shift to 2nd gear at <15 kmph speeds the car accelerates very slowly upto 25-30 kmph after which it gains momentum rapidly. Of late, when the a.c. compressor is switched on it makes a kind of muted diesel clatter type of sound. When I showed it to the MASS, they told that the sound is normal and there is nothing to worry about it. Other k10 engined car owners please comment on the power delivery with respect to the ac on or off.

Anybody know what kind of AC compressor is found in Astar, Swift etc; is it Wobble plate, Rotary or Scroll?

Petrol engine delivers quite a feeble torque at low RPMs.
AC compressor eats up whatever feeble torque your engine is producing.
The result is what you are experiencing.

I would recommend you to please use the accelerator pedal (to race the engine) and the gear shift (to downshift). They have a purpose.

I never understood the tendency of most of the Indian drivers to be extremely feeble footed on the accelerator pedal and the tendency to up-shift in milliseconds, whether the engine is capable or not (of producing enough torque at that RPM).

***

The AC compressor would never make the "diesel clatter" so this looks like a potential problem.

Agree with Alpha 1. You need to downshift to allow the engine perform at optimum levels. Airconditioners use power from the engine. Dowshifting will make up for the loss of power required for the wheels.

Dear Sankar,

Maruti uses AC systems from two OEMs; SUBROS and SANDEN. All SUBROS compressors are Swash Plate type (Wobble Plate Type). Two out of the three compressors manufactured by SANDEN are Wabble Plate Type and one is Scroll Type. It would be advisable to see which brand and which type of compressor is installed in your car.

Alternatively, if you give your car's VIN to the local Maruti Dealer Workshop, their Spare Parts Manager would be able to tell you the exact type used in your car.

Happy Driving!:)

The ECU is supposed to compensate a bit when one switches on the AC.

Estilo/Alto K10/AStar uses the same engine. People should have complained about the power loss by now.

Parryontheprowl, much appreciated! If the OEM compressor is of the swash/wobble plate type i want to convert it to a scroll type compressor with lesser capacity. I have read that scroll type are very energy efficient and a lower CC scroll can effectively do the job of a larger swash/wobble. Since i drive with AC on always using a efficient compressor can gain me better fuel efficiency and also some more power to the wheels.

Any idea which car has a scroll type compressor in India? Tata Nano's is a 60cc rotary vane type.

Dear Sankar,

The scroll and the rotary type are one and the same. They are useful for low cubic capacity engines and suitable for low NVH (Noise, Vibration & Harshness) and also boast of low power consumption. This would explain their use in TATA Nano.

I do not know of any specific car in India using this compressor other than the one you have mentioned. However, it would be a good idea to speak to the local SANDEN representative in your city to find out which car comes with a rotary/scroll type compressor.

Happy Driving!

I would suggest you look at the surface first-
1) ensure the air filter is clean so that the engine breathes better.
2) Check Tyre Air pressure

Once this is done then check and see if you find a difference in the way the car behaves.

How loud is the noise? Audible from the cabin? AC compressors don't make as much noise as you seem to be facing.
Mostly Subros compressors - all are reciprocating swash / wobble plate type. A few Behr and Sandens were installed in some Maruti models, not sure if any came in the A-Star. Scroll compressors, AFAIK, are common across all VW/Skoda models - don't know what make of compressor.

The compressor unit on the A-Star is of Subros make. I always upshift at much higher rpms(of course by hearing the engine sound as the Vxi doesn't have a tacho). But with the AC on the car struggles to pull even at 10 kmph in 2nd gear. After 25 kmph the problem vanishes and the car pulls cleanly. Shifting to first at speeds between 10 to 15 is'nt very pleasant as the motion becomes jerky. Driving without AC is impossible in the hot and sultry Bhubaneswar. Can Swift owners throw light on whether there is any perceptible drop in performance with AC on?
@SS-Traveller - The clattering noise is only heard when the compressor button is switched on during idling. This is also audible inside the cabin.

Has this power delivery issue always been there in your 4 year old car? Or has it recently cropped up?

If the former, well, that's just the bane of small petrols with poor low end torque. Your only option is to downshift.

You might also want to try some mild performance mods that enhance the low-rpm torque delivery. Sure made a world of difference to my Civic.

This is most certainly not a normal noise from any AC compressor. Please prevail on the MASS people to have this attended to, especially if you are within warranty.

Parryontheprowl, There are rotary scroll type and rotary vane type compressors, rotary scroll has a spinning spiral meshed inside a stationary spiral and rotary vane compressor works like a wankel engine. I suppose both these must be more efficient than the swash plate type. Between scroll and rotary i don't know how their efficiency compare. I wish nano has a scroll type rotary instead of a vane type rotary!

Btw if anyone is interested in AC compressor downsizing check out the attached article - Reducing AC Power Consumption By Compressor Downsizing on a Sports Utility Vehicle by D. Srinivasan & Prasad Phadke, Tata Motors Ltd.

Abstract
Reducing AC power consumption in an automobile is one of the key challenges for climate control engineers. The AC compressor consumes power from the engine which directly affects fuel economy and vehicle drivability. The main objective of this study is to reduce front end auxiliary drive (FEAD) load on engine by compressor downsizing, without compromising on cooling performance of the AC system. The study has been carried out on a sports utility vehicle (SUV) which has twin evaporator AC system. The three compressors under study have been critically evaluated at three levels a) Component level b) System level and c) Vehicle evel. The study has been conducted in two phases 1) downsizing from 170 cc/rev reciprocating piston compressor to 130 cc/rev compressor and 2) further downsizing from 130 cc/rev reciprocating piston compressor to 90 cc/rev rotary scroll compressor. The results of this study demonstrate that AC power consumption and refrigerant quantity are reduced by 25% and 5% respectively.

I have been thinking about compressor downsizing ever since i read this article, but have not taken any initiatives towards this. Seeing the post made by 100kmph has sparked the interest yet again.

I just got off the phone talking to a car AC shop in Trivandrum. He said Tata Nano has Behr compressor, can any Nano owners confirm? I would be meeting them soon to discuss the possibility of transplanting a scroll type compressor in my Swift.

Sanden Vikas has a scroll compressor in their line-up so that is an option as well!
http://www.sandenvikas.com/tr-scroll.html