paulf
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| posted on 10/1/06 at 05:52 PM |
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What sensors to use with Megasquirt?
I am just about to build my Megasquirt and have to decide which coolant and air temp sensors to use. As I understand it I need to adjust the bias
resitors to suit which sensors I am using.What have others fitted?
The designed sensors are american GM ones , would these be the same as Uk spec Vauxhalls? or should I use Bosch or Ford sensors and adjust the Bias to
suit or use easytherm compensate?
Paul.
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suparuss
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| posted on 10/1/06 at 06:05 PM |
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when i did mine i just went to the local motor factors and asked for 2 of the cheapest coolant sensor, they gave me two little bras things (not a clue
what off) for 4 quid each and then i dipped em in water at different temperatures measured the temp and resistance and then used easytherm to changed
the values. one of them was used for the coolant and the other for manifold air temp. you need a multi meter for this though but is really easy.
probably easier than trying to find the right sensors.
Russ.
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rayward
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| posted on 10/1/06 at 06:49 PM |
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your best just to use whichever sensors fit your engine(e.g thread size etc) then use easytherm to set them up in your MS.
Ray
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paulf
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| posted on 10/1/06 at 07:04 PM |
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I am fitting to a crossflow and will have to adapt the water sensor to the block so can use any really or could use the temperature sensor in the head
but suspect this is not ideal.
Looking on the megasquirt forums it seems as if even using easytherm it is advisable to adjust the bias resistors if possible, to make the full range
of the sensor as linear as possible . As I havent started bulding I thought it would be best to decide before i have fitted them and then need to
replace with a different value.
I will drop into the factors tommorow and see what I can obtain. I have a small ntc bead thermistor that I may use for the air temp .
Also need to work out if I need a fast idle output as i intend to use the edis code to run my ignition, and it looks the best output option for
that.
Paul.
quote:
Originally posted by rayward
your best just to use whichever sensors fit your engine(e.g thread size etc) then use easytherm to set them up in your MS.
Ray
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MikeRJ
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| posted on 11/1/06 at 12:51 PM |
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quote:
Originally posted by paulf
Looking on the megasquirt forums it seems as if even using easytherm it is advisable to adjust the bias resistors if possible, to make the full range
of the sensor as linear as possible
Yes, this is quite important, otherwise you can end up using only a small part of the ADC's input range, giving very poor resolution.
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CairB
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| posted on 11/1/06 at 01:10 PM |
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I thought that I may have been able to use the coolant temp sensor that drives the temp guage on a pinto but it of little use lower down the temp
range due to resitance v temperature.
The mechanical mounting is probably one of the main chaoice factors between suitable signal sensors.
There are quite a few posts on the Megasquirt forum regarding sensor choice. I think that someone has listed the calibrations of the most popular.
It is worth trying different series resistor values to ensure that you get the best measured value and use Easytherm to generate new lookup tables.
I made an AIT from a Maplins thermister (69p) mounted in a Nylon bolt.
I thought that I might need the fast idle but I have managed without so far, not been driving much in the cold!. Placing a U (retarded) in the
ignition map at the desired idle rpm helps to stiffen up the idle.
Cheers,
Colin
[Edited on 11/1/06 by CairB]
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bernie955
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| posted on 28/2/06 at 08:27 PM |
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Where can I get a copy of Easytherm?
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BKLOCO
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| posted on 28/2/06 at 08:34 PM |
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quote:
Originally posted by bernie955
Where can I get a copy of Easytherm?
If your using MSII V3 you don't need Easytherm.
It's all built into the basic setup software.
Otherwise Easytherm is at the B&G site under the V2.2 instructions I think.
Sorry to get easytherm you need to log into the megasquirt EFI forum
Youl find it at:
forum index>download database>megasquirt downloads>tuning software>easytherm
There is a link in instruction 53 of the V2.2 assembly instructions.
This is what the instructions say about changing resistors verses using easytherm:
If you want to use other sensors, you can either:
* change the transfer-function files in the ECU processor by using EasyTherm to change MegaSquirt's code to match your temperature sensors),
OR
* switch these resistors, which may be easier in some cases.
Normally, you should use EasyTherm, it's generally more accurate, as the curve is based on three points, rather than the one point of a resistor
swap.
[Edited on 28-2-06 by BKLOCO]
Experience is what you get when you don't get what you want!!! 
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