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Old 16th February 2011, 00:07   #31
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Originally Posted by Sutripta View Post
^^^^
Hi,
My thoughts:
If the spring is made stronger (stiffer) droop will increase. If spring remains the same, and only preload is changed, operating point will shift, but characteristics (droop) will remain the same.
Hi, actually the heavier flyweights in the governor will decrease the droop and the rigid spring provides similar effect. yes the preload provides a fixed additional quantity through out the governing range. hence it will not alter the droop.

by jerk injection pump, you mean inline pump? the main difference with this compared to a VE pump is the plunger draws only the desired fuel that is to be injected where as in VE pump the plunger draws fully and spills the rest after injection.
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Old 16th February 2011, 00:48   #32
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Default Re: FIP Flop

Excellant explanation by DB sir. These are the posts with dollops of crucial information that I always look forward to.

Warm Regards
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Old 16th February 2011, 20:34   #33
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Hi, actually the heavier flyweights in the governor will decrease the droop and the rigid spring provides similar effect.
Hi,
Don't think stiffer spring -> less droop.
Keep making the spring stronger. -> Limiting case when it is a rigid member, rather than spring. -> No governing action then. (equivalent to fuel rack frozen). -> Maximum droop.

Other extreme (no spring) it will operate in bang-bang mode.

Increasing the weight of the balls would, I think, increase the loop gain. Would lead to lower droop, but ultimate instability.

Quote:
by jerk injection pump, you mean inline pump?
Yes. Esp. single element of the inline pump, popularly known as bottle pumps because of their shape. Multicylinder engines had one per cylinder. On large low speed engines, even the cam was separate. Gives a very good feel for what is happening as you can see the governor moving the fuel rack, the engine note changing, the puff of black smoke. These engines used to hunt at idle (couldn't figure out why) and you could see the fuel rack oscillating.

Anyway, time to get back to the topic of diesel combustion.

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Sutripta
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Old 25th February 2011, 06:48   #34
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... In common jargon, this is known as "advance" or "retard". If it is advanced, lots of smoke will come but power will marginally increase. This is what technicians do to give some more life to dead engines. If it is retarded, cooling system demand wil lincrease due to flame front travelling through a larger crank angle. Both are harmful to the engine and the environment. ECU controlled engines save all this hassle as nobody will mess around with them....
In order to comply with BSIV regulations Mahindra may upgrade the MDI3200tc to CRDe with an ECU, or, just introduce a new ECU controlled diesel motor to replace the MDI3200tc, an engine found across much of the Mahindra line.

Many of Mahindra's 4x4 vehicles use the MDI3200tc including the new Thar MDi. If Mahindra goes with an ECU controlled motor, will owners still be able to modify differential ratios and gear ratios of tranny and transfer case? Or, will sensors and ECU be fooled by such mods?
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Old 25th February 2011, 08:29   #35
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Many of Mahindra's 4x4 vehicles use the MDI3200tc including the new Thar MDi. If Mahindra goes with an ECU controlled motor, will owners still be able to modify differential ratios and gear ratios of tranny and transfer case? Or, will sensors and ECU be fooled by such mods?
Hi DD,

The ECU will / should malfunction -> implies more unburnt fuel at the wrong rpm -> Bad for the engine.

Unless, the vehicle is intelligent enough to have a hoard of sensors at various levels and multiple remaps ONBOARD, a change in the FD ratio will screw up things.

Ofcourse, the mahindra experts can elaborate better. I could be completely wrong here!

Last edited by headers : 25th February 2011 at 08:30.
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Old 25th February 2011, 20:12   #36
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The ECU will / should malfunction -> implies more unburnt fuel at the wrong rpm -> Bad for the engine.
I'd think that an ECU malfunction (as opposed to a sensor malfunction) will stop the engine dead in its tracks. And I'd say todays ECUs are quite reliable from the electronics PoV. Waterproofing/ Environmental protection is a matter of cost and philosophy, not technology.

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Old 25th February 2011, 21:08   #37
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I'd think that an ECU malfunction (as opposed to a sensor malfunction) will stop the engine dead in its tracks. And I'd say todays ECUs are quite reliable from the electronics PoV. Waterproofing/ Environmental protection is a matter of cost and philosophy, not technology.
Hi,

Why should the ECU stop the engine dead?

If the sensors give incorrect values, things that come to my mind are:

1. Smart ECUs go into a hunt mode / safe mode if all parameters are beyond acceptable levels and the vehicle can be driven to the nearest workshop or 100 kms or some minimum set parameter before they die!!!

2. No so smart ECUs will move the car at the cost of power/emission.

3. A super smart ECU learns the difference in sensor values and alters its control accordingly.

Ofcourse gurus like vijay reddy [star_aqua], Karthik of race dynamics can give better better inputs here.
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Old 25th February 2011, 21:25   #38
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Hi,

Why should the ECU stop the engine dead?

If the sensors give incorrect values, things that come to my mind are:

1. Smart ECUs go into a hunt mode / safe mode if all parameters are beyond acceptable levels and the vehicle can be driven to the nearest workshop or 100 kms or some minimum set parameter before they die!!!

2. No so smart ECUs will move the car at the cost of power/emission.

3. A super smart ECU learns the difference in sensor values and alters its control accordingly.

Ofcourse gurus like vijay reddy [star_aqua], Karthik of race dynamics can give better better inputs here.
Yeah, this is my understanding. Another name for "safe mode" is "limp mode".

What I am afraid of is that these new ECU controlled engines will just handcuff any attempts to mod the vehicle.

I can not picture M&M installing a super smart ECU as original equipment....my Invader only has one freaking key operated door lock. It is on the driver's door. The passenger door has no key hole. Would you belief that cheap cr*p??? They aren't going to put much of an ECU in anything, methinks.
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Old 26th February 2011, 00:10   #39
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Vikram, you DD and sutripta all are correct. its finally the oem which decides how smart the ecu should be which reflects how smart the vehicle is because its the brain of the vehicle. some regulations will force the ecu to be smart when it comes to emissions and passenger safety. there are some sensors and actuators which can cause life threat when they fail. these sensors are double checked and monitored very closely. limp home comes into picture only when these sensors fail. limp home is not a punishment. there are punishment modes or inducement modes which will come into picture only for emission related failures. this will either reduce the power or consume more fuel which will cause inconvenience to the driver. US will not approve any vehicle for road release or road legal until unless the critical sensors are monitored for errors and limp home works when it should work.
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Old 26th February 2011, 20:06   #40
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Originally Posted by headers View Post
Hi,

Why should the ECU stop the engine dead?
Malfunctioning ECU.


Quote:
3. A super smart ECU learns the difference in sensor values and alters its control accordingly.
Adaptive to sensor malfunctions!? Can it be done?

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Old 27th February 2011, 08:51   #41
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Malfunctioning ECU.
The limp mode is there to get back incase of ECU malfunction!!



Quote:
Adaptive to sensor malfunctions!? Can it be done?
BTW, why do you sound so similar to a friend of mine on this forum
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Old 27th February 2011, 12:06   #42
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I have one Question for DB Sir or Spike ( others can also answer )

How to re-start a CRDe or ECM ( etc ) controlled vehicle ,after the tank goes empty & we re fill it ( there can be any reason for such situation )

I know a thing or two in older vehicles ( non CRDe/electronically controlled ) about bleeding the system & priming it etc . But what about the above ?

Sudarshan
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Old 27th February 2011, 12:13   #43
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The limp mode is there to get back incase of ECU malfunction!!

BTW, why do you sound so similar to a friend of mine on this forum
AFAIK, limp mode invoked by a functioning ECU which detects an engine malfunction. Idea is to maintain mobility without damage.

Your friend sounds like a kindred spirit. Introductions are in order.

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Old 27th February 2011, 13:04   #44
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How to re-start a CRDe or ECM ( etc ) controlled vehicle ,after the tank goes empty & we re fill it ( there can be any reason for such situation )
Fill diesel -> Crank -> If starts immediately then drive away OR if it doesn't start immediately some amount of priming will be required through the hand primer positioned on top of the fuel filter assembly. That's it, let me know if you need a photographic description of the same.

Quote:
Originally Posted by headers View Post
The limp mode is there to get back incase of ECU malfunction!!
Are you sure it is for ECU malfunction? Is the probability of a ECU malfunction higher compared to various sensors?

Quote:
Originally Posted by Sutripta View Post
AFAIK, limp mode invoked by a functioning ECU which detects an engine malfunction. Idea is to maintain mobility without damage.
Dada, correct

Spike

Last edited by SPIKE ARRESTOR : 27th February 2011 at 13:05.
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Old 27th February 2011, 13:21   #45
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Originally Posted by SPIKE ARRESTOR View Post
let me know if you need a photographic description of the same.
most welcome . (a fuel circuit chart will also do )

AFAIK, the sequence in conventional/old engines ( Non CRDe & Electronics ) is > Fill/connect supply>Hand Prime ( of any kind ) This includes bringing diesel supply to FE/distributor pump> Bleed FE/Distributor pump ( trying to start the vehicle without bleeding damages the FE pump )

Now with this reference what is the position in CRDe & electronically controlled units ? Is the Bleeding part important or its simply not there ? (Can do without that ? )

I am asking because this ( running out of fuel & restart ) happens with everyone , may be once in lifetime of vehicle .

Sudarshan
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