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Old 17th November 2011, 00:10   #1
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Default RPM meter for XD3P (Mahindra) diesel engine

How to go about installing a rpm meter in 550 xd3p engine.The wiring is different from that of the Bolero or a THAR. So friends please help me out with this.I think this will help many other fellow BHPians who own 550s.
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Old 17th November 2011, 06:56   #2
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Default Re: rpm meter for xd3p

IMHO &AFAIK there is only one way to fit an RPM meter to a diesel engine -- an electronic meter taking pulse from alternator .

on many modern day alternators there are roughly three wire connections , check along with your electrician

1) A thicker wire of all , current output

2) a smaller wire , from switch to alternator field

3) another smaller wire - Pulse for electronic RPM counter . if you check the voltage by multimeter it will show some 6 to 7 volts only --- this is the major differentiating factor in identifying this wire -- above two wires will show 12+ volts

4) another wire if provided will be earth wire - easily identifiable

I have fitted one such meter to my old landy here
http://www.team-bhp.com/forum/4x4-te...l-meter-2.html (Accelerator (pedal travel ) meter)

check my posts # 25,27 for pics

I have chosen a meter ( electronic ) from the Tata Cummince parts range.

When I fitted a new alternator . will shortly send a wiring diagram

Sudarshan
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Old 17th November 2011, 19:07   #3
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Default Re: RPM meter for XD3P (Mahindra) diesel engine

Hi,
Hope these threads help you
http://www.team-bhp.com/forum/techni...mbassador.html (RPM Meter for Isuzu Ambassador)
http://www.team-bhp.com/forum/techni...kes-tacho.html

Regards,
Ilango
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Old 17th November 2011, 20:57   #4
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Default Re: RPM meter for XD3P (Mahindra) diesel engine

@ ilangop ---Is it possible to tap the old alternator ? can you explain some more on the whole thing here also ? I have checked the & links thanks for that
My Jeep has the old A 115 alternator , below Pic with only two wires ( field & output/ supply ) will be interesting to have a RPM meter for it too

RPM meter for XD3P (Mahindra) diesel engine-dscn3150.jpg

Also here is a pic of my New Alternator on Landy It has 4 wires provided , one of them ( W terminal ) is used for RPM pulse , but again I had to re calibrate the dial , as pulley sizes ( crank & Alternator ) differ from original ratio for meter . Also the alt .is from one vehicle & the meter from another , obviously they were not going to match .

Dear all check this pic for my earlier reference to the 4 wires , if you have the new gen alternator , then half of the worry is solved .

RPM meter for XD3P (Mahindra) diesel engine-dscn3154.jpg

Sudarshan

Last edited by Sudarshan : 17th November 2011 at 21:03.
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Old 21st November 2011, 15:16   #5
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Default Re: RPM meter for XD3P (Mahindra) diesel engine

Quote:
Originally Posted by Sudarshan View Post
@ ilangop ---Is it possible to tap the old alternator ? can you explain some more on the whole thing here also ? I have checked the & links thanks for that
My Jeep has the old A 115 alternator , below Pic with only two wires ( field & output/ supply ) will be interesting to have a RPM meter for it too

Sudarshan
The exploded view of A115 is available in the below link.
http://escort.mk3.pagesperso-orange....s/0686-05a.pdf
You will have to remove the black plastic cover on the rear side of the alternator.
The below link gives the connection schematic of components inside the alternator.
ME08
You will have to tap one of the 3 phase wires to have the "W" output in your alternator. I am yet trying to figure out if a DIY can tell the number of AC pulses are produced per revolution of the Alternator shaft.
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Old 9th March 2013, 11:38   #6
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Default Re: RPM meter for XD3P (Mahindra) diesel engine

@ Sudharshan -

Slightly OT: What is the redline of the landy?

This setup works but IMO is not linear above a certain rpm.
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Old 9th March 2013, 11:55   #7
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Default Re: RPM meter for XD3P (Mahindra) diesel engine

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Originally Posted by headers View Post
@ Sudharshan -

Slightly OT: What is the redline of the landy?

This setup works but IMO is not linear above a certain rpm.
Max RPM they have given is 4200 ( if I remember correctly ) but mine does not cross 3700 at full pedal .

I had to re calibrate the meter ( dial ) , I counted the front flywheel ( pulley ) speed with non contact RPM meter & re marked the dial accordingly . It was a Long process as I had to fix a temporary accelerator cable to front bumper then keep the engine speed fixed at certain reading then marking the dial in cabin

Now dont ask if I had calibrated the RPM meter ( non contact one ) for accuracy

Sudarshan

Last edited by Sudarshan : 9th March 2013 at 11:56.
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Old 13th March 2013, 10:44   #8
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Default Re: RPM meter for XD3P (Mahindra) diesel engine

Quote:
Originally Posted by headers View Post
This setup works but IMO is not linear above a certain rpm.
Quote:
Originally Posted by Sudarshan View Post
Max RPM they have given is 4200 ( if I remember correctly ) but mine does not cross 3700 at full pedal .
Thats what I had mentioned - I had a Yezdi Roadking in 1993 with the RPM meter [electronic] from pricol installed in a similar fashion, but it would max out at a particular limit - Investigations revealed that the diode rectifier unit of the alternator has a current limitation and this current is used to drive the rpm. Hence after a particular rpm when the current maxes out, the rpm needle does not move even if the engine revs higher.

This is not a popular conversion too.
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Old 13th March 2013, 17:18   #9
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Default Re: RPM meter for XD3P (Mahindra) diesel engine

Quote:
Originally Posted by headers View Post
Thats what I had mentioned - I had a Yezdi Roadking in 1993 with the RPM meter [electronic] from pricol installed in a similar fashion, but it would max out at a particular limit - Investigations revealed that the diode rectifier unit of the alternator has a current limitation and this current is used to drive the rpm. Hence after a particular rpm when the current maxes out, the rpm needle does not move even if the engine revs higher.
Headers, I doubt if this would happen because I have rebuilt the rpm meter in my car and I am aware of how the circuit works.
The current generated by the alternator is far more than what is required for the rpm meter. Secondly, it is not the magnitude of the current but the no of sparks per unit time that drives the meter. Did you have a CDI in your bike?
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Old 13th March 2013, 17:56   #10
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Default Re: RPM meter for XD3P (Mahindra) diesel engine

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Headers, I doubt if this would happen because I have rebuilt the rpm meter in my car and I am aware of how the circuit works.
The current generated by the alternator is far more than what is required for the rpm meter. Secondly, it is not the magnitude of the current but the no of sparks per unit time that drives the meter. Did you have a CDI in your bike?
Yes I did sir.

What was happening if I remember was the diode was the limiting factor in the circuit.

You could always refresh my memory
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Old 22nd March 2013, 22:10   #11
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Default Re: RPM meter for XD3P (Mahindra) diesel engine

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Originally Posted by headers View Post
Yes I did sir.

What was happening if I remember was the diode was the limiting factor in the circuit.

You could always refresh my memory
Most probably used a retriggerable monostable, with too large a pulsewidth for the given incoming trigger pulse frequency.

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Sutripta
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