Spinning DSM (4G63) CAS in reverse

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DJpowerhaus
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Spinning DSM (4G63) CAS in reverse

Post by DJpowerhaus »

For 10 years now, I've been working on putting [DOHC] 4G63s into RWD cars. One of the earliest problems was the clearance between the firewall and the CAS on the back of the head. After 10 years of finding other solutions (cutting the firewall, moving engine forward, 95, 96 style cam / crank triggers), I figured I'd finally give moving the sensor to the front a shot. I was inspired by someone else who had done it, but with a 4 tooth trigger and no home to worry about syncing. Making a bracket and coupling seems easy enough.

http://projectzerog.com/images/members/ ... G_2607.JPG
http://projectzerog.com/images/members/ ... G_2608.JPG
http://projectzerog.com/images/members/ ... G_2609.JPG

Now I really want to figure out this trigger disc.

Using the composite logger I have logged the OEM sensor spinning the stock direction which recognized the correct rpm as expected with no sync errors:
http://projectzerog.com/images/members/ ... .06.46.png
BenchTestOEM.csv
I've also logged the sensor spinning backwards with the disc flipped and the MS recognized the correct RPM with no sync errors.
http://projectzerog.com/images/members/ ... .05.46.png
BenchTestFlippedreverse(FrontMount).csv
Comparing the two however reveals that the signals do not match, one is offset, most likely do the the offset of LEDs in the Mitsubishi CAS.
http://projectzerog.com/images/members/ ... seBlue.png
Can I correct this offset with any settings in Tunerstudio?


Ideally, I'd like to solve it be having new trigger discs laser cut so that it will work with the OEM ECU. I scanned the trigger disc into the computer at the highest resolution possible and traced it out in Sketchup (I <3 Sketchup).

Scan (PNG):http://projectzerog.com/images/members/ ... 20disk.png
Sketchup Drawing:http://projectzerog.com/images/members/ ... ploded.skp

I can export it as a .dxf to laser cut at the local hacker space (Baltimore Node). First I need to figure out what I need to do to modify it. I can rotate the 4 outer trigger slots relative to the center key as well as the inner trigger slots to .1 degree in Sketchup. How can I figure out how many degrees and which direction?

Thanks for any help you can give.
Mike Bowman
aka DJpowerhaus
http://www.projectzerog.com
jsmcortina
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Re: Spinning DSM (4G63) CAS in reverse

Post by jsmcortina »

For use with Megasquirt I would suggest using an aftermarket trigger disc (12-1) if you are going to the trouble of dismantling the CAS.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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DJpowerhaus
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Re: Spinning DSM (4G63) CAS in reverse

Post by DJpowerhaus »

The goal is to have a front mounted CAS that works with the OEM ECU.

I may upgrade to a disc with finer resolution though once I get this sorted out.
Matt Cramer
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Re: Spinning DSM (4G63) CAS in reverse

Post by Matt Cramer »

If OEM compatibility is needed, you'd need to flip the disc upside down.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
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Re: Spinning DSM (4G63) CAS in reverse

Post by jsmcortina »

DJpowerhaus wrote:The goal is to have a front mounted CAS that works with the OEM ECU.
Why are you posting in a Megasquirt forum then?

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
DJpowerhaus
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Re: Spinning DSM (4G63) CAS in reverse

Post by DJpowerhaus »

With a little measuring from my drawing in Sketchup and then rounding* I come up with this as my 2 triggers:

60, 30, 60, 30, 60, 30, 60, 30
30, 150, 70, 110

*I can't imagine the engineers who designed this would use arbitrary angles, so I'm not too scared rounding them to the nearest 5th degree since at most its 1 degree from my measurements which can only be so accurate considering manufacturing tolerances, my scan's accuracy, my tracing of that scan.

Image

With these 2 patterns locked, I can rotate them independently pretty easily in Sketchup. Seems as though they are about 5 degrees off from where they would line up in 2 spots. I'm eyeballing my datalogs and guessing that my OEM sensor pattern and flipped/reverse pattern are off around 25 degrees (less than 30, more than 15). Not sure which direction. Will see if I can get some prototypes laser cut so I can benchtest and log.. think about.. dial in again.

Is there a way to put in Tunerstudio an offest of 25 degrees and see what kind of signal it generates? Would be nice to figure out the angle in software before I have to do it in hardware.
DJpowerhaus
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Re: Spinning DSM (4G63) CAS in reverse

Post by DJpowerhaus »

Thanks for checking the thread guys. I appreciate the input.

James, the Megasquirt / Tunerstudio seems to be a pretty good tool to see what's going on in the computer. Visibility I wouldn't have with an OEM computer. I did post in the OEM hardware section, is there a better spot? If I get this right, I should be able to put in any computer OEM or aftermarket without having to specify much more about the CAS than that it is a 4G63.

Matt, I wish it was as easy as flipping the disc over. That would work if the inside and outside sensors were in line, but they are not. Flipping & spinning backwards gets really close / synced, but there is an offset presumably caused by the offset of the 2 LEDs in the CAS. Might be a good idea for me to disect one, photograph / scan it and see how many degrees those LEDs are.
Healey3000
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Re: Spinning DSM (4G63) CAS in reverse

Post by Healey3000 »

DJpowerhaus wrote:Thanks for checking the thread guys. I appreciate the input.

James, the Megasquirt / Tunerstudio seems to be a pretty good tool to see what's going on in the computer. Visibility I wouldn't have with an OEM computer. I did post in the OEM hardware section, is there a better spot? If I get this right, I should be able to put in any computer OEM or aftermarket without having to specify much more about the CAS than that it is a 4G63.

Matt, I wish it was as easy as flipping the disc over. That would work if the inside and outside sensors were in line, but they are not. Flipping & spinning backwards gets really close / synced, but there is an offset presumably caused by the offset of the 2 LEDs in the CAS. Might be a good idea for me to disect one, photograph / scan it and see how many degrees those LEDs are.
Hi,

Something to watch out for, depending on the CAS model - many have an oil seal on the shaft. Unfortunately, the seal is designed for counterclockwise rotation only. I have taken apart several CAS versions, made by both Mitsubishi and Hitachi and I think that a seal is used if the CAS is horizontally mounted. The vertical ones sometimes have a machined seat for a seal but one isn't installed. If yours has one and you spin it backwards, the seal may fail.
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