A 3.4 DOHC Build then... F40 Turbo (Page 10/57)
Fierobsessed MAR 19, 01:48 PM
Can you give me a link? I tried searching for it without any luck.
Joseph Upson MAR 19, 03:00 PM

quote
Originally posted by Fierobsessed:

Can you give me a link? I tried searching for it without any luck.



http://www.fiero.nl/forum/A...130314-2-113809.html
Fierobsessed MAR 19, 07:11 PM
Thank you!

I see that you basically set yours up to create a 4K PPM input system. If I read it correctly, you used OUT4 (Open Collector) which natively divides the 60,000 PPM of the F40 by 32, then your multiplier factor of 2.024 sets you up with a 3795 PPM output, or about 4K.

I plan on using it in a different manor, as a straight divider. You will always need to use the pullup if you are coming out of OUT2, OUT4, or OUT5 as they are "Open Collector" meaning it just grounds the wire to trigger a signal.

OUT1 and OUT3 are AC output, they shouldn't need any pullup resistor, or circuit, they should simulate a VSS.

Screw what the manual tells you to do. Read past that nonsence.
It seems like SW3, doesn't effect OUT1 (AC) and OUT2 (OC) they are always going to put out the factored ratio of the input directly, between 4X to 1/4X.

With SW3 off, It natively divides the input by 2 for both OUT3 (AC) and OUT4 (OC), and divides by 4 for OUT5 (OC) All changeable by a factor of 4X to 1/4X, Good for cutting down pulse counts reasonably.
With SW3 on, it divides by 16 for OUT3 (AC) 32 for OUT4 (OC) and 64 for OUT5 (OC) All changeable by a factor of 4X to 1/4X So you'd use this setting if you REALLY need to cut down the pulse count by a substantial factor.

So I plan on using OUT1, all switches OFF and running a multiplier of .386 (10 Corse, 6 Fine) to straight divide the number of teeth from 78 to 30.1, Ideally I would need 30.
OR I can use OUT3, all switches OFF and a multiplier of .771 (14 Corse, 10 Fine) to first divide the pulses in half, then factor that by .771 to arrive at 30.1 ish again.

With this, no mods should be needed to the Road Speed Constant or I/P Divisor. It will be recieving the same 24k PPM that TGP ($8F) is used to seeing, at least I hope. But, It's all talk till I can prove it, right?

Good call on the twisting of the pairs for the VSS. I should have done that, not too late though. I've used a SGI-5 before (SGI-5B, Metal case) in the past, and it did exhibit some extreme twitchiness on the speedometer that seemed somehow related to the engine RPM, while I was not moving. Plus this time my VSS and crank sensor leads are in the same bundle, so twisting the pairs would probably be a wise thing to do.

[This message has been edited by Fierobsessed (edited 03-19-2013).]

Fierobsessed MAR 20, 04:04 AM
Looking at Fuel pumps, I felt it was obvious that a 255 LPH pump should flow in the range needed for my engine. They generally can support around 500 hp or so.
In the 255 LPH flow category we have a lot of options, at really good prices. Everyone runs the Walbro's. Many complain of noise, and some of reliability issues.

I was doing a bunch of research on each of the available 255 LPH pumps, and the truth is that its not easy to do. No one does an honest side by side comparison of this category of pumps. I was going nuts trying to find the "best" pump. So much so that my girlfriend started researching too. She actually found one that has a lifetime replacement warranty, promises to be quiet and had an independent test, which also sited the Walbro f2000169.

HFP Brands, HFP-343


Walbro f2000169


And for $79, seems like a winner. This looks like this is the same pump that is supplied by TRE Performance.
darkhorizon MAR 20, 11:33 AM
Why do you have a dakota converter? Why not just feed 60k into the ecu?
Fierobsessed MAR 20, 03:17 PM
Although you can set the road speed constant to display speed correctly inside the ECM, the I/P pulse divisor in obd1 ecms only has a few valid settings, none of which are compatible with 60k ppm. They can only do 8 potential divisor rates. So, without it, I would have no speedometer or odo.
Joseph Upson MAR 20, 04:32 PM

quote
Originally posted by Fierobsessed:
Although you can set the road speed constant to display speed correctly inside the ECM, the I/P pulse divisor in obd1 ecms only has a few valid settings, none of which are compatible with 60k ppm. They can only do 8 potential divisor rates. So, without it, I would have no speedometer or odo.



I tried all of the I/P divisors and recall only 0 and 1 work properly, or at all. When I entered the other divisors it shut the odometer down for a few minutes before it would start working again.
Fierobsessed MAR 20, 06:42 PM
The digital IO extender chip "U10" on ALL 7749/7730/7727 based ECMs are physically wired to output the pulse divisor to digital outputs 5, 6, and 7.

The input byte is configured by the high 3 bits of a byte.

So it looks like this:
Divisor A = Bit 7
Divisor B = Bit 6
Divisor C = Bit 5

76543210
00000000 = 0
00100000 = 32
01000000 = 64
01100000 = 96
10000000 = 128
10100000 = 160
11000000 = 192
11100000 = 224

So the working divisor bits should simply be increments of 32, up to 224.
Joseph Upson MAR 20, 07:48 PM

quote
Originally posted by Joseph Upson:
I tried all of the I/P divisors and recall only 0 and 1 work properly, or at all. When I entered the other divisors it shut the odometer down for a few minutes before it would start working again.



That should read several, including some of the values you posted. I stopped experimenting when the temporary disabling of the odometer that resulted suggested something that could possibly damage the odometer electrically was occurring as I had already had prior incidents where the odometer needle swung violently to the point of coming off the gauge.

The road speed constant helped fine tune the odometer once the appropriate pulse divisor was selected. The bits don't show up in the 8F code mask in TP5 the way you have them posted but they do in Code59.

[This message has been edited by Joseph Upson (edited 03-20-2013).]

fieroguru MAR 20, 07:53 PM
You can run the VSS wired right to the ecm and enter 60K for the ppm. This will make the ECM see the right speed. Then you can splice into the Yellow VSS wire to drive the Dakota Digital box and use it to run only the Fiero speedo. The best thing about this method is that the common "noise" (where the speedo randomly jumps to 20mph) the Dakota Digital box produces at low vehicle speeds will not be sent to the ECM, which can change idle speeds and cause other drivability issues.