[GeneralJazz]

Originally Posted by fiat_tarun

ABS valves are designed to release pressure and not hold pressure. Sure they can hold for short durations, but if this is done on a regular basis (like in the case of hill hold), the valves will fail and this is why it cannot be done with ABS.

I have to disagree. They do both during ABS working. Either way, the brake pressure applied by the driver during a typical hill start (considering a reasonable slope) is way lower than that during a panic braking. At such low pressures, the valves wont have any issues.

Link

Just take a look at any of the Maruti AMT's with only ABS & Hill Hold and you will see that the hydraulic unit is actually an ESP, and you can trust Maruti to find the most economical solution.

An ESP unit requires an additional ESP pump motor and separate hydraulic pathways, adding quite a bit to the cost and complexity. Having an entire ESP unit, and then not using it doesnt make any sense.

My point is, HH can be achieved via ABS just fine. Knowing Maruti, it doesnt make sense why they would insert the costly ESP unit just for this basic HH function, and not use the ESP for its actual purpose. Wouldn't it be a huge selling point for them to actually have the feature?

[fiat_tarun]

Originally Posted by GeneralJazz

I have to disagree....

When ABS or EBD is operational the closing and releasing is in microseconds and the system is continually transferring driver braking input to the wheels, just distributing basis requirement and releasing to prevent lock up. Holding a vehicle on a slope for 2-3 seconds continuously is a whole different pressure level and the system has to work on all slopes (not only reasonable slopes). My knowledge is for passenger car systems and I cannot comment on the 2W systems, so that example is not really comparable.

I say all this as I am in this very line with direct knowledge and access to development of these systems. I have verified everything I've said with product experts, just to be sure.

There is no separate ESP pump motor over ABS, the complete hydraulic unit for ABS is replaced by a hydraulic unit for ESP which has the required valves, a bigger motor, an optional integrated yaw rate sensor (most cases nowadays) and of course the relevant ECU.

For the Maruti case, I kindly request you to take a look inside the engine bay of a vehicle with hill hold and without and compare the size of the hydraulic unit. The price differential is also not as much as one thinks. To quote David Ward from GNCAP, it should not be more than $50 (Link)

Why they don't offer full ESP is anyone's guess, more so since the export versions get the full deal. I can only think of the savings from not adding a steering angle sensor and the fact that Maruti isn't the poster boy of offering safety features proactively.

[nightraven]

Originally Posted by ron178

..I don't understand how a yaw rate sensor would help detect inclination..

Originally Posted by fiat_tarun

..The yaw sensor will detect the plane on all 3 axis' - X, Y & Z and hence is the sensor used for Hill Assist as well...!

I agree with ron. If we are keeping the argument purely technical, then ESP and Hill-hold work on different sensor inputs at the fundamental level.

Excluding the steering angle sensor out of the discussion, basic ESP works based on the yaw rate sensor, which is a gyroscope. It measures angular velocity around its vertical axis (X,Y plane) i.e. rotation of the car around a vertical axis including our Ecosport Tarun. Advanced ESP systems also provide Roll Stabilty which have an additional gyroscope (Roll rate sensor) to detect rotation of a car around the horizontal axis (Y,Z plane). (Ecosport S in India doesn't get Roll sensor hence no RSC, while global models have it in addition to ESP)

Hill Hold function works by measuring tilt angle using accelerometers. Most, if not all, car manufacturers package all vehicle dynamics sensors in a single module/assembly/PCB for ease and its easy to confuse one with another or assume that one wouldn't work without the other sensor.

Originally Posted by GeneralJazz

Strictly speaking, Hill Hold is possible without ESP....

Originally Posted by fiat_tarun

..Just take a look at any of the Maruti AMT's with only ABS & Hill Hold and you will see that the hydraulic unit is actually an ESP...

Basic Hill-hold (where car holds for 2-3 secs after you lift off the brake pedal) should be possible on a basic ABS car just like in some bikes in theory. Why it is not offered is anyone's guess. I assume could be due to safety reasons such as in case of valve failure or brake pressure relief somewhere accidentally, the car will just roll. This can be negated atleast for a certain time or extent on ESP cars as the High-pressure pump in the ESP/ABS assembly can apply excess pressure as needed without the driver having to manually apply brake.

I have no experience with Maruti but it seems illogical that Maruti is using HCU from a ESP system but haven't enabled ESP on Brezza. It wouldn't take long or lot of money for a vehicle dynamics engineer to calibrate the car for ESP. Going by Tarun's information Maruti should have offered ESP. It would have been a huge selling point.

Originally Posted by fiat_tarun

..an optional integrated yaw rate sensor (most cases nowadays) and of course the relevant ECU.

AFAIK most yaw rate sensors (i.e. sensor assembly) are not integrated and are located at the center of the dash or console preferably near vehicle's center of gravity. In case of ES, sensors are part of the Restraints Control Module (RCM), under the hand brake assembly, that controls the airbags and seat belts restraints.

[fiat_tarun]

Originally Posted by nightraven

I agree with ron. If we are keeping the argument purely technical, then ESP and Hill-hold work on different sensor inputs at the fundamental level.

Yes, purely from a technical point an acceleration sensor will do the job for hill hold, but there is no product that exists with this combination (as far as I know). Most countries have moved to standard ESP over the last decade and India is probably the only large market still with high ABS volumes. Additionally this requirement of ABS with hill hold is unique to India and more so Maruti. You will need ESP valves in a ABS HU plus addition of an acceleration sensor. Developing such a product just for India will make it cost more than a ESP unit!

Advanced ESP systems also provide Roll Stabilty which have an additional gyroscope (Roll rate sensor) to detect rotation of a car around the horizontal axis (Y,Z plane). (Ecosport S in India doesn't get Roll sensor hence no RSC, while global models have it in addition to ESP)

Roll stability is a value added function of ESP and the systems I work with need no additional sensor apart from the yaw rate. Roll over mitigation needs additional calibration and that's it. I'm not very familiar with the Ecosport system but I know Ford uses a different strategy. The ESP system is without a integrated yaw rate sensor but the Airbag ECU is a high end unit with a yaw sensor which ESP also uses. When the Airbag ECU has a yaw sensor it can detect roll over crashes which very few regular cars can claim. And no, the Airbag ECU cannot use the signal from an integrated yaw sensor in an ESP unit.

Basic Hill-hold (where car holds for 2-3 secs after you lift off the brake pedal) should be possible on a basic ABS car just like in some bikes in theory. Why it is not offered is anyone's guess.

As mentioned earlier, ABS valves are not designed to close completely for such a long duration when there is no driver brake input.

... It wouldn't take long or lot of money for a vehicle dynamics engineer to calibrate the car for ESP.

In the auto industry, OEM's will fight to reduce even 1 rupee from a component's price, so eliminating a sensor is a big deal, especially if the OEM believes the general public really doesn't care about ESP. Hill hold is something that can be demonstrated and sold quite easily.

AFAIK most yaw rate sensors (i.e. sensor assembly) are not integrated and are located at the center of the dash or console preferably near vehicle's center of gravity. In case of ES, sensors are part of the Restraints Control Module (RCM), under the hand brake assembly, that controls the airbags and seat belts restraints.

What you are saying was correct till about 8-9 years back and most if not all new generation ESP systems come with integrated sensors as it is more cost efficient compared to having a separate sensor. You need to reference the mounting point from the CG of the vehicle so the right inputs are received. Some examples like Ford (not all cars) and higher end vehicles have it in the Airbag ECU.

[GeneralJazz]

A few points from my side.

Originally Posted by fiat_tarun

Holding a vehicle on a slope for 2-3 seconds continuously is a whole different pressure level and the system has to work on all slopes (not only reasonable slopes). My knowledge is for passenger car systems and I cannot comment on the 2W systems, so that example is not really comparable.

Hill holds donot work on all slopes. They do have a limit on the maximum slope that can be supported. And yes, there are passenger cars with just ABS (and not ESP), that have Hill hold feature.

I say all this as I am in this very line with direct knowledge and access to development of these systems. I have verified everything I've said with product experts, just to be sure.

Just to let you know I'm not a troll, I work on development of such systems myself! There are platforms (4W) with ABS+HHC combinations. Several low cost/older platforms have included HHC for newer models/facelifts. [/quote]

There is no separate ESP pump motor over ABS, the complete hydraulic unit for ABS is replaced by a hydraulic unit for ESP which has the required valves, a bigger motor, an optional integrated yaw rate sensor (most cases nowadays) and of course the relevant ECU.

Oops, my bad! That was what I meant! Yes the ESP motor replaces the ABS unit.

For the Maruti case, I kindly request you to take a look inside the engine bay of a vehicle with hill hold and without and compare the size of the hydraulic unit. The price differential is also not as much as one thinks. To quote David Ward from GNCAP, it should not be more than $50 (Link)

I'll leave it to your expertise in Maruti platforms in this case

Why they don't offer full ESP is anyone's guess, more so since the export versions get the full deal. I can only think of the savings from not adding a steering angle sensor and the fact that Maruti isn't the poster boy of offering safety features proactively.

Even the SASs arent that expensive for bulk buyers. Its truly crazy why MS is doing this!

[VPJ74]

I am looking for a safe and reliable hatchback primarily for Mumbai city usage and have shortlisted the 2022 i20 SPORTZ CVT (2 Airbags, NO ESP) costing ~ 10L OTR. The top CVT variant Asta(O) comes with 6 Airbags AND ESP costing about 12.5 OTR.

Is the ESP worth having in a new car in 2022? I don't know much about the real benefits of an ESP or the quality of the ESP in the i20 but is it a feature one would pay 2.5L extra to have? I was sort of on the fence with the 6 airbags (vs 2) but now am really thinking whether the Asta(o) with 6 AB and ESP is a better buy? I am thinking Mumbai roads and Maharashtra ghats in monsoon and skid protection.


The i20 would primarily be used as a city runner / a 2-passenger car but would be driven on the highways occasionally to Nashik/Pune/etc. I would rarely ever use it for the family with kids.

Interestingly, the Jazz does not come with an ESP but the Maruti swift and Baleno also do