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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Tue Jun 18, 2013 9:22 pm 
Fifth Gear
Joined: Wed Nov 12, 2003 12:26 am
Posts: 2266
Location: USA: Portland, OR (Tigard, ~200ft elevation)
Further troubleshooting - for posterity's sake, this is the FCD being troubleshot:
viewtopic.php?f=15&t=52077

free5ty1e wrote:
Oh, snap. You actually have an FCD wired directly into an ECU patch harness - that's nice! That's the way to make a truly plug-and-play FCD, although thats quite a bit more parts and labor involved.

I've never seen one like this before, but I'd imagine it's all wired in to the ECU as it should be if VRG3 made it. Hmm... that'll make it tougher to troubleshoot as well. You'll have to find the ECU pin for the pressure sensor and verify that there is at least a signal going to it with the ignition on. Beyond this, my troubleshooting steps may be of help if you can identify which wire is which on the FCD. May require examining his schematic and the FCD a couple times - trace signals from the chip to the wires and you should be able to figure it out.

If you are able to get on boost, I'm imagining that the chip is still good; the symptom of a bad chip is typically the car cutting power as as soon as you start spooling up the turbo with any decent throttle. It may just be the voltage divider has drifted out of spec or degraded somewhat and is no longer keeping your voltage clamped below 3.9V.

If you are able to figure out which wire is which on the FCD, try wiring the +5v pin directly to the input pin and watch the output. If it goes above 3.9V then that's your problem; you'll need to replace resistors or adjust a potentiometer / knob if it has one and watch this output voltage until it is at 3.9V.


Hope this helps!

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-Chris
91SS 4EAT stock
91SS 5MT awaiting engine rebuild and VF36...
92SS 4EAT - RIP :(
94SS 5MT4.11+rLSD 289k km: RobTune550,TD05-16g @ 18psi,FMIC,3"TBE,Forester lift


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Tue Jun 18, 2013 11:17 pm 
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free5ty1e wrote:
I also note that Vikash's original FCD page is down but Josh has it hosted on the surrealmirage domain here:
http://www.surrealmirage.com/vrg3/fcd/
...I will have to update the http://fcd.chrispaiano.com webpage in order to reflect this. It is still referring to the old page on graphics.cornell.edu. I'm sure I'll get to that at some point.



I talked Vikash a while back about mirroring his old site and he updated the pages to go on my site.

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surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Tue Jun 18, 2013 11:31 pm 
Fifth Gear
Joined: Wed Nov 12, 2003 12:26 am
Posts: 2266
Location: USA: Portland, OR (Tigard, ~200ft elevation)
Oh, awesome -- I was concerned that wealth of useful knowledge might be down. I haven't seen any postings from Vikash in a while, I hope he's doing OK!

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-Chris
91SS 4EAT stock
91SS 5MT awaiting engine rebuild and VF36...
92SS 4EAT - RIP :(
94SS 5MT4.11+rLSD 289k km: RobTune550,TD05-16g @ 18psi,FMIC,3"TBE,Forester lift


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Wed Jun 19, 2013 1:34 am 
Fifth Gear
Joined: Wed Nov 12, 2003 12:26 am
Posts: 2266
Location: USA: Portland, OR (Tigard, ~200ft elevation)
Found the parts list to accompany the schematic for anyone wanting to wire up their own without the PCB (these are DigiKey part #s from the date of the schematic... I would imagine they are all still the same, although there are brief descriptions here that would assist searches):

Part Label: Part Description - DigiKey Part Number
C1: .1uf - 445-2851-ND
D1: 1N4148 - 1N4148DITR-ND
D2: LED red - 754-1274-ND
D3: LED blue - 754-1248-ND
D4: 1N4001 - 1N4001DITR-ND
J1: headerRtAng_5pos - WM4103-ND
P1: housing_5pos - WM1578-ND
Q1: 2N3904 - 2N3904TFCT-ND
R1: 20k - SP043-20K-ND
R2: 20k - 20kQBK-ND
R3: 1k - 1.0kQBK-ND
R4: 4.7k - 4.7kQBK-ND
R5: 47k - 47kQBK-ND
R6: 4.7k - 4.7kQBK-ND
T1: term clip - WM1114-ND
T2: term clip - WM1114-ND
T3: term clip - WM1114-ND
T4: term clip - WM1114-ND
T5: term clip - WM1114-ND
T6: term clip - WM1114-ND
T7: term clip - WM1114-ND
U1: LM224 - 296-7030-5-ND
W1: wire_6ft_5conductor

Edited for readability (tabs aren't showing up in post, and that's what they were originally in my text file).

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-Chris
91SS 4EAT stock
91SS 5MT awaiting engine rebuild and VF36...
92SS 4EAT - RIP :(
94SS 5MT4.11+rLSD 289k km: RobTune550,TD05-16g @ 18psi,FMIC,3"TBE,Forester lift


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Fri Mar 07, 2014 11:33 am 
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Hi everyone. Spent an interesting time reading through the thread - seems some of the links to products are dead since its a pretty old thread, but a really interesting read.
I saw the page some time ago and a couple of mates wanted FCDs but were shocked by cost of commercial ones so asked me to make a couple from the design - I have done this but definitely seem to have done something wrong, or misunderstood.
I made 3 of the adjustable types - and they clamp perfectly but output does not follow input - its actually higher. I'm not great at electronics so I cannot see what I have done wrong despite several hours of checking, and it appears I'm no good at following institutions either.
Has anyone had similar problems or possibly point me in the correct direction?

Chris


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Sun Mar 09, 2014 2:49 am 
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Hi Chris,

I know I pointed you to the site and this thread specifically.

Any chance you could take some hi res close up pictures of the FCD's you built? That would allow others to look at what you did to compare it against Vikash's diagrams.

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surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Sun Mar 09, 2014 2:27 pm 
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Josh,

Many thanks for that and the reply. All as per the eagle files and board below - appologies for quality of soldering but all checked for good connection despite scruffy looks.


Image
Image
Image
Image

Chris


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Mon Mar 10, 2014 12:29 am 
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Chris,

I've looked at your schematic and it looks correct. My question would be is your variable POT resistor around the 20k ohms called for in the schematic?

I guess my other comment is regarding the assembly; it's hard to tell in the diagram, but are you sure you have the diode installed in the proper direction? There are some large solder blobs on the back of the board. Are you sure that the solder blobs aren't making connection with other traces on the board?

Lastly, where are you getting 5v from, the MAP sensor wiring from the ECU?

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Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Mon Mar 10, 2014 1:50 am 
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Hi,

Thank for taking a look - I must have done something fundamental wrong here, and have spent longer trying to figure it out than they took to draw, route, mill and make!! Feeling like a bit of a dimwit as reading the thread everyone seems to have got them working with no issues and I have 3 that dont.

Yes the pot is exactly 20k, I bought them especially. I did check several times about the diode as black line is hard to see and even checked it out on the internet as I thought I was going mad! I have checked none of the blobs are making unhelpful contact but its really not a problem as where the copper is milled away it does not flow or stick. I made 3 and they are all the same.

I have not got so far as fitting them to cars as wanted to prove to myself that they were working as they are supposed to first. I made 3 and all are exactly the same which is why I thought I must have made an error in the schematic or my wiring.

For testing to ensure they function correctly I ran it from a 12v bench supply and generated the 5v from a 7805 regulator and simulated the signal from a pot off the 5v, which I can vary between 0 and 5v. Then measured the input and output with DVMs. Output exceeds input but appears to clamp perfectly.

regards.


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Mon Mar 10, 2014 6:00 pm 
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Hmm,

In reading through this thread, have others primarily built the adjustable or non-adjustable ones?

Everything you've done sounds correct. You've exceeded my level of expertise on the circuit.

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Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Mon Mar 10, 2014 6:40 pm 
Fifth Gear
Joined: Fri Jun 20, 2008 8:17 am
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Location: Lakewood, Wa 98439
Ive always made the non adjustable.

Sent from my SGH-T889 using Tapatalk

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92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
98 LGT 4EAT
98 LGT Wagon 4EAT


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Wed Mar 12, 2014 5:29 pm 
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Chris,

If it's possible, you may want to try and modify one of them to be non-adjustable and see if it responds properly.

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Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Wed Mar 12, 2014 6:26 pm 
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OK. Thanks. I'll try that and see what happens.


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Wed Mar 12, 2014 9:11 pm 
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OK. Just built a fixed one and tested it. Voltage clamped at 4.13 volts but output is not equal to input.

I'm convinced due to the wonders of Eagle that I must have the design right and am wondering if either:-

a:- My test procedure is not correct?
b:- I have misunderstood the function of this device?

It is my understanding that the voltage gets clamped at the maximum weather thats set on the fixed item or variable on the adjustable one. That works fine. The question comes to if I am misunderstanding the fact that the output to the ECU should in unclamped state equal the input - we are not looking to alter the signal just pass it through if less than clamp and fixed it at clamp if above?

Spent so long on this now that:-

1:- I dont want to give up
2:- I could have bought the 3 that we need at full retail price!!! lol

Many thanks for anyones help.

regards


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Thu Mar 13, 2014 5:09 am 
Fifth Gear
Joined: Wed Nov 12, 2003 12:26 am
Posts: 2266
Location: USA: Portland, OR (Tigard, ~200ft elevation)
Chris t wrote:
....the output to the ECU should in unclamped state equal the input - we are not looking to alter the signal just pass it through if less than clamp and fixed it at clamp if above?


This is correct.

Sent from my SAMSUNG-SGH-I337 using Tapatalk 2

_________________
-Chris
91SS 4EAT stock
91SS 5MT awaiting engine rebuild and VF36...
92SS 4EAT - RIP :(
94SS 5MT4.11+rLSD 289k km: RobTune550,TD05-16g @ 18psi,FMIC,3"TBE,Forester lift


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Thu Mar 13, 2014 5:49 pm 
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Chris,

Can you provide a quick table of the input & output voltages you are seeing up to the clamp voltage and beyond? You may have mentioned this before, but I can't seem to find it. A simple table would help visualize it for me.

Thanks

_________________
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Thu Mar 13, 2014 8:21 pm 
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ADJUSTABLE

Input Output

0.00 0.00
0.50 0.82
0.75 1.45
1.00 2.08
1.25 2.63
1.50 3.05
1.75 3.39
2.00 3.68
2.25 3.92
2.50 4.10
2.75 4.27
3.00 4.40
3.25 4.51
3.50 4.61
3.75 4.70
4.00 4.78
4.25 4.85
4.50 4.91
4.75 4.96
5.00 5.00

The clamp can be set on the adjuster from 2.5v to 5v, in which output never exceeds the set clamp value but still follows the table until it hits the clamp setting when it goes flat and never rises any further.

Image


Last edited by Chris t on Fri Mar 14, 2014 1:51 am, edited 2 times in total.

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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Fri Mar 14, 2014 1:33 am 
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FIXED VERSION

Input Output

0.00 0.00
0.50 0.80
0.75 1.39
1.00 1.95
1.25 2.44
1.50 2.81
1.75 3.15
2.00 3.42
2.25 3.67
2.50 3.88
2.75 4.05
3.00 4.13
3.25 4.13
3.50 4.13
3.75 4.13
4.00 4.13
4.25 4.13
4.50 4.13
4.75 4.13
5.00 4.13

Graph at:

Image


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Fri Mar 14, 2014 6:09 pm 
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Chris,

I believe what you are experiencing may be a result of how the circuit works. The thing is, it really doesn't matter. The first gen turbo Legacy ECU is rather stupid and only uses the MAP sensor for fuel cut protection. So as long as you stay below the fuel cut threshold the ECU is happy and non-the-wiser. If these ECU's were smarter or were MAP based then you wouldn't be able to use this circuit as it would be providing a higher reading for the MAP sensor then the actual reading.

So I would say everything looks good and to hook up the FCD's to the car to test them out and tune the fuel cut point.

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Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Sat Mar 15, 2014 2:31 am 
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Thank you for all the help - that's really rather disappointing and suggests the device is totally pointless? If the actual reading does not matter then why not just fit 2 resistors as a divider for less than a penny rather than all this effort? Only 1 was required for a Legacy so we had hoped that as both the write up on the web page and this forum suggest the signal passes through unaltered.
Was educational building it just a shame it does not appear to do anything at all unless I have missed the point?

I am very grateful for your help.

regards


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 Post subject: Re: Cheap Electronic FCD - Revised
PostPosted: Mon Mar 17, 2014 6:39 pm 
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Chris,

In regards to the voltage being higher than the input, please keep in mind I am only making a guess that this operation is normal. Vikash would have to provide input on this. I should also clarify my previous post in that the MAP sensor on the turbo Legacy is also used for barometric pressure readings. So having its reading being significantly off certainly could affect the engine's performance.

Rather than me speculating on things, let me see if I can get Vikash to weigh in on things.

Thanks

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Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm


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