[vina]

Originally Posted by dhanushs

Yes, can get an OBD reader without voiding the warranty. The Figo's OBD port is somewhere beneath the steering. Its there to give us info, and hence will not void the warranty.

You can get cheap OBD readers tru ebay. They throw a hell lot of info, like Intake Air Temperature, Coolant temperature, throttle position, instantaneous fuel consumption, voltage across the terminals, pressure, speed, rpm and what not..

Here's a snap of heads up display on the windshield. You will need a symbian/android (preferably android) to read the values.
Attachment 541319

Thanks Dhanushs

I checked on ebay, two units are available but none seems to need a android phone (or even symbian).

here's one: eBay India: Professional Grade OBD-II + EOBD Code Reader + Scanner (item 300502203474 end time 06-Jun-2011 13:23:06 IST)


Also is there any chance at all that using such a unit could cause damage to the ECU?


By the way, your image shows that the unit is giving a value for power (hp) how does it do that, is there any torque meter there in the engine?

[dhanushs]

Originally Posted by vina

... two units are available but none seems to need a android phone (or even symbian)...

Vina, check on ebay.com, not ebay.in.

Here are some random links. Search around and I'm sure you will find one much cheaper.

NEW ELM327 OBD2/CAN/OBDII USB SCAN/Scanner/Code Reader | eBay
NEW ELM327 OBD2/CAN/OBDII Bluetooth Scanner/Code Reader | eBay

Originally Posted by vina

Also is there any chance at all that using such a unit could cause damage to the ECU?

I dont think so, because all we are doing is reading what the port is giving out. Its like listening to the sound from a laptop through headphones. With these readers, I doubt we can program/send commands to the ECU (No Write, only read).

Originally Posted by vina

By the way, your image shows that the unit is giving a value for power (hp) how does it do that, is there any torque meter there in the engine?

No idea, there must be a sensor on the crankshaft. The power values I get are realistic, but torque values are not.

[vina]

Originally Posted by dhanushs

Vina, check on ebay.com, not ebay.in.

Here are some random links. Search around and I'm sure you will find one much cheaper.

NEW ELM327 OBD2/CAN/OBDII USB SCAN/Scanner/Code Reader | eBay
NEW ELM327 OBD2/CAN/OBDII Bluetooth Scanner/Code Reader | eBay

I went to ebay.com immediately after writing my previous post - found a lot of stuff. Thanks.

Originally Posted by dhanushs

I dont think so, because all we are doing is reading what the port is giving out. Its like listening to the sound from a laptop through headphones. With these readers, I doubt we can program/send commands to the ECU (No Write, only read).

well, on the internet they ask you to avoid some of the cheap Chinese ones because they caused the engine to refuse to start - also the same port apparently can be used to program the ECU, so a malfunctioning unit can play havoc (in theory). Headphone example is very relevant in general except that (1) headphone is a passive device (2) the port is purely output - no input so it really can not do any damage to the laptop BUT even for that a bad headphone connector can damage the laptop's connectors.

I think I'll get one from US next time I'm there.

Originally Posted by dhanushs

No idea, there must be a sensor on the crankshaft. The power values I get are realistic, but torque values are not.

Returning to this (and the original subject of the thread):

This is surprising, did you try rpm*torque = power equation? at the very least that should be consistent.

In general measuring power would actually entail measuring rpm and torque, and I don't know how the torque is being measured internally (it is not impossible, for example you could put a torsional spring between engine shaft and driver shaft and measure its distortion, or measure the strain on the existing shafts using a strain gauge ... but impractical to do so with any accuracy)

Another method would be putting some hypothetical efficiency figures and then solve equations for heat flow (mass of exhaust air and temp.) out of the engine, coolant temp. , fuel consumption etc. and arrive at some rough number for power being generated - this method will give good enough results in very rare cases.

[vina]

Originally Posted by dhanushs

Vina, check on ebay.com, not ebay.in.

Here are some random links. Search around and I'm sure you will find one much cheaper.

NEW ELM327 OBD2/CAN/OBDII USB SCAN/Scanner/Code Reader | eBay
NEW ELM327 OBD2/CAN/OBDII Bluetooth Scanner/Code Reader | eBay
.

By the way, did Maruti 800 (2005 model) have OBD ports?

[dhanushs]

Originally Posted by vina

By the way, did Maruti 800 (2005 model) have OBD ports?

Was the '05 800 MPFi?. If so yes.

Another thing Vina, is that, these OBD readers arnt compatible with all ECU's. You might wanna check out before you buy. For eg: Most of these readers arnt compatible with Swift D.

[vina]

Originally Posted by dhanushs

Was the '05 800 MPFi?. If so yes.

Another thing Vina, is that, these OBD readers arnt compatible with all ECU's. You might wanna check out before you buy. For eg: Most of these readers arnt compatible with Swift D.

thanks, I'll be buying for my Figo (got two of those now), and let us see if it works on the M800 as well - if it doesn't - no problem.

I checked on torque sensors - they are hard to put and very expensive, so cars don't have them. The ECU uses an algorithm to figure out power levels based on rpm, air flow and fuel intake (probably some assumed efficiency formula) no wonder your numbers feel inconsistent.

[vina]

a further question on turbo-lag:

usually (i.e. on dicussions on team bhp and elsewhere on the internet) it has been said that the turbocharger needs to be spinning at a certain rpm before which it'll not generate enough pressure.

While that is obviously true, I have been thinking - Even is the engine rpm is correct wouldn't there be a time lag invloved too?

i.e. time taken for the turbo itself to start spinning (even if exhaust gas pressure is sufficient) and also, time taken for enough air to be delivered and compressed (even after the turbo is spinning fast eough)?

I guess this will be important for 0-100 times (and that kind of things) only

any comments on that?

[Sutripta]

^^^
Hi,
Yes, there is a time component. That is why it's called 'lag'. Else it would be no different from 'coming on the cam'.

If a turbo has spooled down for any reason, to spool up it needs energy from the exhaust gases, (and time to overcome mechanical inertia). The exhaust gases are generated from the inlet charge. Which is insufficient initially because the turbo has gone off boost. Building up boost takes a bit of time, the lag.

Regards
Sutripta

[vina]

Originally Posted by Sutripta

^^^
Hi,
Yes, there is a time component. That is why it's called 'lag'. Else it would be no different from 'coming on the cam'.

If a turbo has spooled down for any reason, to spool up it needs energy from the exhaust gases, (and time to overcome mechanical inertia). The exhaust gases are generated from the inlet charge. Which is insufficient initially because the turbo has gone off boost. Building up boost takes a bit of time, the lag.

Regards
Sutripta

Well lag need not be on time, e.g. lead-lag compensator (it is the phase in frequency domain, not time directly). Also most people (including on this thread) never mention the time component- for them it is like "once you reach 1700-2000 rpm on a swift the engine becomes a rocket".

Going by this, if one is moving down on a decline, with the gear engaged, but pedal totally free, (car still moving on a good rpm, because of the speed) - will there still be the time lag component if I suddenly depress the pedal?

I mean the exhasut gases would have very little excess energy for some time in this case, given that I had been coasting so the turbojet shouldn't really have had much to spool up on for a while.

Am I (even partly) correct?

[Sutripta]

Originally Posted by vina

Well lag need not be on time, e.g. lead-lag compensator (it is the phase in frequency domain, not time directly).

Am I (even partly) correct?

Hi,
Are you in chip design, or control engineering?

You are correct. Measureable by seat of the pants? You tell me.

Would be interesting to compare the power/ torque curves of the same engine measured on a inertial dyno and a brake dyno. (Pls. no discussions on the merits/ demerits of various dynos, and the foolishness of comparing figures obtained under different setups)

Regards
Sutripta

[vina]

Originally Posted by Sutripta

Hi,
Are you in chip design, or control engineering?

Analog designing sirji, so basically I'm into everything; that is why I keep poking you

I have sort of seen the stuff happening on my Figo - can't be sure I'm not confusing it with something else.

The idle rpm is roughly 800, at if I keep foot on the pedal slightly depressed (2nd gear for all of the discussion here, assume car is already moving very slowly) it growls and picks up slowly till 1000, then a little faster then at 1200-1400 it feels like my seat is pushing me forward. The whole thing takes a few seconds.

On the other hand at speed brakers when I slow down and start again, sometimes the rpm drops to 900-1100 range, and the power is almost instantly available, even at the 900-1000 range.

I think I asked about this elsewhere too, but nobody responded.

Originally Posted by Sutripta

You are correct. Measureable by seat of the pants? You tell me.

Would be interesting to compare the power/ torque curves of the same engine measured on a inertial dyno and a brake dyno. (Pls. no discussions on the merits/ demerits of various dynos, and the foolishness of comparing figures obtained under different setups)

Regards
Sutripta

I don't know what is inertial/brake dyno - will check before poking again.

However I was thinking about your response on another thread (don't remember which one) regarding air flow, and I have another question:

(this is my understanding - may be wrong) Most of the time the torque/rpm curve is measured by letting the engine run at a whole lot of rpm values and measuring the peak torque available at each of those rpms while the engine is doing steady state.

Now on road, the rpm may not be steady state (e.g. under overtaking) - is it possible to momentarily (say for 3-4 seconds) get an rpm boost by playing around with clutch/pedal etc.? some sort or "create the air ram by pressing the clutch and increasing the rpm"

- I may be talking absolute BS here , so please do have some fun I wouldn't mind

[Sutripta]

Originally Posted by vina

Analog designing sirji, so basically I'm into everything; that is why I keep poking you
So Bob Pease your guru.


However I was thinking about your response on another thread (don't remember which one) regarding air flow, and I have another question:

(this is my understanding - may be wrong) Most of the time the torque/rpm curve is measured by letting the engine run at a whole lot of rpm values and measuring the peak torque available at each of those rpms while the engine is doing steady state.

Now on road, the rpm may not be steady state (e.g. under overtaking) - is it possible to momentarily (say for 3-4 seconds) get an rpm boost by playing around with clutch/pedal etc.? some sort or "create the air ram by pressing the clutch and increasing the rpm"

I would say that if you are facing anomalies in the Figo, either there is something wrong with the car, or your butt is waaay more sensitive than mine!

You can get an engine into its powerband quickly by slipping (and burning) your clutch.

Regards
Sutripta

[vina]

Originally Posted by Sutripta

I would say that if you are facing anomalies in the Figo, either there is something wrong with the car, or your butt is waaay more sensitive than mine!

You can get an engine into its powerband quickly by slipping (and burning) your clutch.

Regards
Sutripta

Sir, Bob Pease, Barry Gilbert, Paul Gray, you, SPIKE ... you name it + the guy in the mirror , I learn from everybody.

No anomalies in my car as far as I know, it is just that being a new driver I keep doing stupid stuff and being who I am keep observing. This was one observation I had regarding the turbo, so at first I thought turbolag was time lag. Later people (kind of) convinced me it was rpm lag. Now I believe it is both.

Today while driving back from work I almost replicated the 1100 rpm thing - but now I'm thinking the car's momentum may have something to do with it too.

As far as clutch slipping goes, I'm usually guilty of releasing it too fast (and having major problems on inclines etc. where slipping is desirable) - not exactly a clutch rider.

[dhanushs]

Originally Posted by vina

... Now I believe it is both ...

Yes, its a combination of both, but during normal driving the time lag is very little compare to the rpm lag, and hence neglected.

While drag racing a turbo diesel, usually during the start, engine is kept in the turbo boost rpm and never really allowed to go below it, even during shifts.

[vina]

Originally Posted by dhanushs

Yes, its a combination of both, but during normal driving the time lag is very little compare to the rpm lag, and hence neglected.

While drag racing a turbo diesel, usually during the start, engine is kept in the turbo boost rpm and never really allowed to go below it, even during shifts.

well, that makes sense.

Another question:

the residual energy from the hot exhaust from the engine is what turns the turbo. In case a car is coasting, there will not be too much of residual energy in the exhaust to begin with. Does the turbo keep spooling in such a case (even though rpm may be high)?