[im_srini]

Originally Posted by nukeblitz

Results are a bit surprising but my math seems solid to me given the assumptions and the idealized nature of the numbers.
https://docs.google.com/spreadsheets...it?usp=sharing
...
- Air density is taken as 1.2kg/m^3.
- Drag coefficient of swift is taken as 0.32.
...

Congratulations on your new Swift

Just curious, how did you arrive at the frontal area for the Swift ?

Your post reminded me of a similar effort a long time ago, hence the query.

Full details here...
.

[Sutripta]

^^^
For approximating retarding forces, measure your coastdown.

Transmissions are actually pretty efficient. Nowhere near the figures bandied about! Major loss is actually the tyres rolling resistance. Approx 1% of vehicle weight.

Wind resistance is not linear.

Regards
Sutripta

[nukeblitz]

Originally Posted by im_srini

Congratulations on your new Swift

Just curious, how did you arrive at the frontal area for the Swift ?

Your post reminded me of a similar effort a long time ago, hence the query.

Full details here...
.

Height multiplied by width. I didn't bother about ground clearance as I figured that would have been taken into account while measuring drag coefficient. I found the drag coefficient somewhere on the internet - not 100% of it's veracity. The schematic says that the ORVMs are not included in the width dimension but I figured that's negligible for the kind of accuracy I'm looking at.

Originally Posted by Sutripta

^^^
For approximating retarding forces, measure your coastdown.

Transmissions are actually pretty efficient. Nowhere near the figures bandied about! Major loss is actually the tyres rolling resistance. Approx 1% of vehicle weight.

Wind resistance is not linear.

Regards
Sutripta

Hmm, I suppose the only real way to measure power at wheel and transmission loss is to take it to a dyno - never done that myself. Besides the power and torque curves are crude approximations at best - especially the diesel. The low end torque is too high as I didn't account for turbo lag and there's no real way to guess it using the known points of max power and max torque, the mid range is probably a bit stronger as diesels tend to hold their peak torque for a bit, and I can't really properly plot out drop off past peak power point

Could you explain the wind resistance bit? I used this formula
Resistance = 0.5 * frontal area * drag coefficient * air density
I assumed that wind speed was 0.

What I found really interesting from my math is that the strong mid range found in the diesel swift can provide more torque to the wheels especially at low (<60 kph), when compared with the petrol even when the petrol's greater rev range, shorter gearing and more outright power are considered - enough so that it even negates the weight advantage the petrol has

PS. Fun fact, by my calculations, good shift points for the swift diesel are at 40, 70, 105 and 140 kph. Petrol? Redline it in every gear

PS2. Another Fun fact, a 75PS Multijet engine cannot have peak torque of 190Nm from 1750 to 3000 like that advertised by Tata on the Vista - 190Nm at 3000rpm is well above 75PS and, if that's true, the engine's power rating needs to be higher

[im_srini]

Originally Posted by Sutripta

Transmissions are actually pretty efficient.
Nowhere near the figures bandied about !

Hello Sutripta, glad you're joining the discussion.
I'm not sure where I found the following data, but 15% to 20% appear to be reasonable estimates, correct ?

Originally Posted by Sutripta

Major loss is actually the tyres rolling resistance.
Approx 1% of vehicle weight.

True, rolling resistance works out to ~1% of the vehicle's weight.
However it appears to be quite small compared to aero-drag, particularly as the speed increases :

Originally Posted by nukeblitz

Height multiplied by width.
I didn't bother about ground clearance as I figured that would have been taken into account while measuring drag coefficient.

The coefficient of drag is independent of frontal area.

Originally Posted by nukeblitz

Could you explain the wind resistance bit ?
I used this formula : Resistance = 0.5 * frontal area * drag coefficient * air density
I assumed that wind speed was 0.

Since drag is a function of speed squared (among other things), it's not linear with speed :

[nukeblitz]

Originally Posted by im_srini

The coefficient of drag is independent of frontal area.


Since drag is a function of speed squared (among other things), it's not linear with speed :

Hmm, that should have made more sense to me the first time around. Resistance is proportional to v^2. Thanks for clearing that up.

I'm not quite sure how to work with calculating drag. I've used the same formula in the spreadsheet and the drag coefficient is probably okay but what frontal area should I be using.

I'm getting interested in working on a better spreadsheet - but I need to know where my errors are and what and how to fix it... I already plan to add in rolling resistance.

[im_srini]

Originally Posted by nukeblitz

...
I'm not quite sure how to work with calculating drag.
I've used the same formula in the spreadsheet and the drag coefficient is probably okay but what frontal area should I be using.
...

Frontal area is usually not mentioned in a vehicle's specifications, but this is what I did...

1) Took this image I'd gotten from somewhere :



2) Created this 'mask' so to speak :



3) Wrote a small program to count all the black pixels in the 'mask'

Using the count of pixels in the mask, the count of total pixels, & the real-world dimensions they correspond to, the frontal area was computed.

[Sutripta]

Originally Posted by im_srini

Frontal area is usually not mentioned in a vehicle's specifications, but this is what I did...
...
Using the count of pixels in the mask, the count of total pixels, & the real-world dimensions they correspond to, the frontal area was computed.

You have way too much time on your hands! BTW, is that an Alto or a Swift?

Originally Posted by im_srini

Hello Sutripta, glad you're joining the discussion.
I'm not sure where I found the following data, but 15% to 20% appear to be reasonable estimates, correct ?

My thoughts
http://www.team-bhp.com/forum/techni...ml#post2385389
and also elsewhere on the forum.
Gearboxes are very efficient. So much so that the amount of energy absorbed to that transmitted is so small it is difficult to measure reliably.
So that leaves the CV joints, and in case of a RWD, the hypoid.

True, rolling resistance works out to ~1% of the vehicle's weight.
However it appears to be quite small compared to aero-drag, particularly as the speed increases :

True. Statement was made wrt tyre rolling resistance being the major component of 'Transmission Loss.'

Originally Posted by nukeblitz

PS2. Another Fun fact, a 75PS Multijet engine cannot have peak torque of 190Nm from 1750 to 3000 like that advertised by Tata on the Vista - 190Nm at 3000rpm is well above 75PS and, if that's true, the engine's power rating needs to be higher

The advertising copy normally reads something like
'between rpm1 and rpm2 xx% of peak torque (of nn Nm) is available.' Which is OK.

Originally Posted by nukeblitz

I'm getting interested in working on a better spreadsheet - but I need to know where my errors are and what and how to fix it.

Easier if you first list out what your assumptions are. Clear thinking behind the assumptions is important.

Haven't gone through your spreadsheet formulas, but from the charts looks like you are doing a piecewise linear model, with two known data points, Max torque@rpm1 and Max power@rpm2. What is your assumed value for torque for the two extreme points.

Regards
Sutripta

[im_srini]

Originally Posted by Sutripta

You have way too much time on your hands !

Actually I already had code for dealing with images & masks as part of an image processing program - I just 're-purposed' it.

Originally Posted by Sutripta

Is that an Alto or a Swift ?

It's an Alto.

Originally Posted by im_srini

...
I'm not sure where I found the following data, but 15% to 20% appear to be reasonable estimates, correct ?
...

Yay ! I found out where I'd gotten the data, knew only CPH could've mentioned Seicento here

Originally Posted by Sutripta

Gearboxes are very efficient.
So much so that the amount of energy absorbed to that transmitted is so small it is difficult to measure reliably.
So that leaves the CV joints, and in case of a RWD, the hypoid.
True. Statement was made wrt tyre rolling resistance being the major component of 'Transmission Loss.'

Oks, got it - so 'Rolling Resistance' should've been rolled into 'Transmission Loss' & not considered as outside of it - correct ?
Considering 0% 'Transmission Loss', there's a 7% discrepancy between the theoretical 'Maximum Speed' of the Alto (167 Kmph) & the empirical one (156 Kmph).



Is this 7% an acceptable value for 'Transmission Loss', if yes, how does one reconcile the values mentioned by CPH ?

[Sutripta]

Originally Posted by im_srini

I'd gotten the data, knew only CPH could've mentioned Seicento here
...
Is this 7% an acceptable value for 'Transmission Loss', if yes, how does one reconcile the values mentioned by CPH ?

Not to cast aspersions, but I think CPH is a tuner.
Some other people had also posted some information on transmission losses. Can't find it now. Maybe you can.

Oks, got it - so 'Rolling Resistance' should've been rolled into 'Transmission Loss' & not considered as outside of it - correct ?

Other way round, but ignoring aero drag losses.

Considering 0% 'Transmission Loss', there's a 7% discrepancy between the theoretical 'Maximum Speed' of the Alto (167 Kmph) & the empirical one (156 Kmph).

For these figures to have any meaning, one should have the coast down figures. And what are your views on manufacturers figures?

Regards
Sutripta

[Sankar]

3rd Free Service done
Items replaced:
Oil filter - 340.61
Oil drain plug - 74.24
MGDO 5W40 Castrol - 1730.05
Screenwash - 4nos - 52.4
VAT 14.5%
Total - Rs2516/-

[Sridhar K]

Originally Posted by Sridhar K

I did my 40k service for my ZDI at Maruti service masters Chennai recently and here is the break up of the bill
...
10) Caliper assy grease: RS 55

I was getting the brake caliper noise (a tung tung noise when driving on broken roads, which vanishes if one press the brakes slightly) before the service and asked them to fix it. They had repacked the caliper assembly with grease but the problem did not go away after the service. I took the car back to them and they repacked the stuff again but advised me to change the caliper pin next time. However, the noise increased and it was really annoying. The mechanic also mentioned that it is a common issue in Swift/Dzire and they repack the disk at every service.

Finally got the issue fixed outside at a mytvs center whose owner suggested a solution that he used on his car i.e. they took the caliper and the pin to the lathe and added a sleeve to keep the pin from vibrating. The total cost was Rs 1.5K but he mentioned that I shouldn't worry for the next 50k kms at least.

MSM also failed to identify the link roads which were gone and I got them replaced for Rs 1.8 K (Rs. 680 X 2 rods + 400 odd labor). The vehicle was making not taking pot holes well even at low speeds and the replacement of the link rods fixed the issue.

[coolboy007]

Originally Posted by Sridhar K

MSM also failed to identify the link roads which were gone and I got them replaced for Rs 1.8 K (Rs. 680 X 2 rods + 400 odd labor). The vehicle was making not taking pot holes well even at low speeds and the replacement of the link rods fixed the issue.

Did you not have extended warranty? From what i know, Maruti does cover suspension parts under warranty till 50k kms so the repair would have been covered under warranty.

What were the improvements post link ros change and call you tell the symptoms of a worn out link rod.

[Sridhar K]

Originally Posted by coolboy007

Did you not have extended warranty? From what i know, Maruti does cover suspension parts under warranty till 50k kms so the repair would have been covered under warranty.

What were the improvements post link ros change and call you tell the symptoms of a worn out link rod.

I initially thought (I have the extended warranty) so but was told that the link rod is not covered under warranty as it can get damaged due to hitting potholes at high speed. At least, that was told by the SA at MSM to my friend, who had come with me for 20k service of his dzire. He had recommended that the link rod in his vehicle was weak and should be changed at the next service and cost would be around 600 odd per rod.

Since I was not satisfied with MSM's work on the caliper pin and they will charge charge me for the break caliper clip, I thought I could change them at MyTVS near my home. That is when the owner suggested the sleeve option for the brake caliper pin. During the work, I asked them to check the link rods and we found that both the front rods were worn out on one side. Was wondering whether I should take it to MSM to see if they will replace them under warranty or alternatively pay 1600 odd to Mytvs and get it done there. Finally got it done at MyTVS to avoid the hassle of going to MSM the third time and I was not confident that they will agree for a warranty replacement.

As for the symptoms, the suspension was not smooth when going through pot holes or cuts in the road even at very slow speeds. The wheels would fall into the pot holes with a thud. However, they were pretty ok when going over speed humps or uneven roads. I had got used to this phenomenon and even did not realize the issue until I drove another Swift. After the link rod replacement, my vehicle just glides over potholes.

[ghpk]

Need to take off the meter panel console of Maruti Swift Dzire (VDI)
tried finding its garage manual but unable to find it.

Need to do some custom DIY work behind the meter panel, the place I need to work on is hard to reach from foot pedal well, so best option would be to take out the speedometer console, I am assuming one can take out the meter panel itself without taking off the entire dashboard hope i am not wrong.

Please suggest.

[a4anurag]

Originally Posted by ghpk

Need to take off the meter panel console of Maruti Swift Dzire (VDI)
tried finding its garage manual but unable to find it.

Need to do some custom DIY work behind the meter panel, the place I need to work on is hard to reach from foot pedal well, so best option would be to take out the speedometer console, I am assuming one can take out the meter panel itself without taking off the entire dashboard hope i am not wrong.

Please suggest.

I am not sure but I guess the top panel needs to be removed but getting that out separately is doubtful. It may need a dashboard removal!

Any FNG can do it for you. Find a good quality FNG in your city (Look up the Directory on Team BHP).