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| F40 with 4.9...VSS Question (Page 2/3) |
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Spadesluck
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FEB 03, 02:29 PM
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| quote | Originally posted by Will:
The Fiero speedometer needs a sine wave signal. If you're going to run the Fiero speedo from the 4.9 ECM speedometer output, you'll need to build a signal conditioning circuit to turn the square wave output from the ECM into a sine wave signal.
Here's how to build the circuit: https://www.fiero.nl/forum/Forum2/HTML/139415.html
Alternatively, use the aftermarket stuff to produce the right signal in the first place. That might involve having a Dakota Digital unit with two different outputs... one to the ECM and one to the Speedo.
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Appreciate that link, I knew the parts and had the schematics to build the circuit, but that picture is worth a thousand words. I plan on using the Dakota Digital to correct the F40 VSS to go to the Caddy ECM. I couldn't find that if the Dakota Digital allowed for a second signal to be output to go to the C203 connections. If it did that, that would make it a much easier job. Not that the circuit is difficult to build though. ha
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lou_dias
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FEB 03, 02:44 PM
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The sensor has 2 wires... A ground and a signal. I would imagine the ground is the VSS low and the signal is the VSS high.
There's not a proper file for recompiling a cadillac bin file in TunerPro. There is one for displaying output from the ALDL but not a full reprogramming...
HP Tuners is what was used to tune my 4.9 but I didn't do it myself, I had to pay someone so I'm not familiar with the available values...but OBD 1/1.5 should be pretty similar.
But again, your Cadillac PCM should be able to use the 60k signal just fine as long as you can set that speed rate from 24000 to 60000 like I did with the 7730. ECMs use vehicle speed to turn certain features on like highway lean cruise, etc... For instance, if you are not moving, it will engage the idle controller differently...
You don't need to convert it in advance unless you can't reprogram the Cadillac ECM.
The other value: I/P divisor is for converting that incoming signal into the 4000 [and/or 2000] PPM signal for the speedo.
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lou_dias
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FEB 03, 03:08 PM
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With a stock Fiero, it's the Fiero speedo that converts the expected 4000PPM analog signal into a digital signal for the ECM. So that return VSS signal from the speedo is no longer needed when doing a swap.
I believe the Fiero speedo also sends a 2000PPM signal to the cruise control unit...but don't quote me on that and that's why when they integrated more options onto ECMs as a whole after the Fiero ECM was designed some things are still carry-overs from legacy hardware and IC chips.
Without any reprogramming you can directly feed the ECM with the F40 VSS and the internally computed vehicle speed will be 2.5x faster. It can be an issue if for instance the speed governor is set at 110mph so now it would kick in at 40ish mph.
You should speak with someone that owns HP Tuners software. You'll most likely have to pay them to download the Cadillac module for that generation. But then they can tell you what you can and can't do.
I do strongly suspect that 2nd VSS output is the 2000ppm signal in case someone chose to use an external CC module... That would be the one to use for an extra 2x division needed...along with the divisor setting of 7 or 8 as I described before.
Here is a reference from Dakota Digital on 2000ppm cruise control units... So this lends further credence that the 2nd VSS 4000PPM output is actually 2000PPM since it didn't work right and is used for external CC modules:
https://www.dakotadigital.com/pdf/sgi-5a.pdf
Who knows...perhaps there is even a setting in the ECM programming that tells that 2nd signal to use 2000 or 4000 and/or to be used at all...[This message has been edited by lou_dias (edited 02-03-2022).]
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fieroguru
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FEB 03, 05:23 PM
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The 2nd VSS output from the caddy ecm is probably for ABS.
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Spadesluck
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FEB 03, 05:38 PM
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| quote | Originally posted by fieroguru:
The 2nd VSS output from the caddy ecm is probably for ABS. |
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That would certainly make sense.
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lou_dias
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FEB 04, 05:01 PM
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I talked to the guy who did my tuning and he sent me this screenshot :
Looks like it is like the 7730...more of a question now if the 2nd VSS output is 4000PPM or 2000PPM...
I had it set to 4000PPM a long time ago from a guy who tweaked my original tune because he too had an Allante intake and I was running way too rich with the Bosch Design 3 Ford injectors...[This message has been edited by lou_dias (edited 02-04-2022).]
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Spadesluck
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FEB 05, 10:43 AM
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Those Bosche injectors where not a direct replacement?
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lou_dias
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FEB 05, 05:59 PM
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| quote | Originally posted by Spadesluck:
Those Bosche injectors where not a direct replacement? |
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They flowed much more than stock.
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Spadesluck
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FEB 07, 08:57 PM
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| quote | Originally posted by lou_dias:
They flowed much more than stock. |
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I know at one point I was looking at these. Boch III 4.9
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Raydar
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FEB 07, 11:31 PM
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| quote | Originally posted by Spadesluck:
I know at one point I was looking at these. Boch III 4.9 |
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Pretty sure those are what I have in mine.
They run just like the stockers, only they don't stumble and misfire.
19# injectors.[This message has been edited by Raydar (edited 02-07-2022).]
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