For those who don't have Riceburners HUD unit, GET ONE! My installation is different than most as I cut into the upper rear of the guage pod and recessed the HUD unit in the pod. Now the wiring to the unit is completely inside the pod and doesn't show. Since the angle for reflecting the speed is tricky, I chose instead to mount a small piece of glass 1" x 1 1/4" at the point where the front of the left speaker panel meets the dash. For those of you slower drivers who don't need all three digits of the display, a piece of glass 1"x1" will do. This installation causes the HUD unit to be permanent and non movable, so you must take time to adjust the glass so the angle allows the reflection directly at eye height. Because of the angle of the speaker panel, the glass does not sit in a straight line with the HUD, but slightly left of it. The top photo was taken from outside and the bottom one from inside. Hopefully, the photos will make everything I have said, clear. Your speed is visible except for bright sunlight and is very bright at nite. (it has a dimmer adjustment) This is one of the more clever and useful gadgets you can add to your Fiero. Ed
IP: Logged
06:10 AM
PFF
System Bot
Firefighter1 Member
Posts: 452 From: Southold,NY USA Registered: Apr 2003
OK- one more try at a photo. I placed a towel over my windshield to reduce the sunlite. You can see the HUD unit on the back of the upper gauge pod. The read out of zero (0) is reflected on the piece of glass. The unit also reads out your speed if you are backing up. Not sure how to use that information yet?
I wish Riceburner would fix the issue with 85 model Fieros so i can get mine to work..........
:-(
well, I'm looking for a newer 120 speedo to fix my 1985 speedo problem. I dont think there going to be a solution for the brown wire/green wire differance.
IP: Logged
08:41 AM
Paul Taylor Member
Posts: 383 From: Reading, Berkshire, ENGLAND Registered: Oct 2002
It doesn't work with the 120mph one either??? That's not good... I finally installed one in my '86SE (had a brown wire) and it's working good.. I also (FINALLY!!) made it to the junkyard before closing time and pulled an '85 cluster and some wires, so I can swap that into my '86 and test. I think I'll be wiring that up tomorrow (Tuesday), and see what the hell is going on with those.. But about the 120mph cluster --- is that from an '85, or later car?? As far as I've heard so far, it's just the '84/'85 cluster that isn't working.. Maybe it's something with the '85 car *and* the speedo??? Or the computer?? I have a feeling I'll have to create a divide-by-2 circuit and ship it to you.. And then get them made in case anyone else needs them.. Now that I have a running Fiero, tesing should be a little easier. Just need a long extension cord so I can drag the Ocilliscope out to the driveway!
IP: Logged
10:34 PM
PFF
System Bot
Aug 26th, 2003
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
the main clue for me is the fact that the signal wire is brown, not green/white. the VSS signal from the trans is the same, its the filtered signal from the speedo to the ECM & Cruise Control, which the HUD gets its signal, that is different somehow. specs on that signal are needed.
IP: Logged
09:18 AM
Riceburner98 Member
Posts: 2179 From: Natick, Ma, USA Registered: Apr 2002
Here we go! I plugged the '85 speedo into my '86, and no HUD.. Plugged the '86 speedo back in, HUD. So, I hooked the '85 up on the bench. My scope is dying slowly, and only lasts about 30 minutes before it shuts down... But in that time I found that the '85 speedo is outputting a signal of .6v max. I wasn't able to take out my '86 speedo to test it on the bench (and can't get the 'scope to the car just yet) so I'll have to check out the signal from an '87 cluster tomorrow night. (have a spare with my project car...) The "good" news is, with just a resistor and a diode, I got the HUD to work with the '85 speedo. Wish my ancient 'scope would work better so I could see exactly what's going on, but it should be an easy fix. I'm guessing the '85 computer internally pulls the signal up, or something like that. I'm not 100% sure how the modification will attach (probably more clip-on things?), but it shouldn't be very difficult to do. From now on I'll ask if it's going on an '84 or '85, and attach the parts before-hand if it is. So... Some good news! Just have to figure it out 100% tomorrow with the '87 speedo. (want to make sure the modified signal doesn't mess with the '85 computer too!) - Bob (EDIT: LOL -- I just cranked up the pulse generator to simulate 120mph, and at or above 120mph, the '85 speedo does circles!! No pins to stop it, so it just spins! Guess that lets you know you're going too fast!)
[This message has been edited by Riceburner98 (edited 08-26-2003).]
IP: Logged
10:04 PM
Aug 27th, 2003
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
-- I just cranked up the pulse generator to simulate 120mph, and at or above 120mph, the '85 speedo does circles!! No pins to stop it, so it just spins! Guess that lets you know you're going too fast!)
[This message has been edited by Riceburner98 (edited 08-26-2003).]
yeah, I found that out the fun way! when the speedo wraps back to 0, it spins. Freaked me out the first time, thought something went wrong.
anyways, so it just lower voltage? can the hud be made more sensitive? or will we need a small amp on the line?
IP: Logged
03:41 PM
Riceburner98 Member
Posts: 2179 From: Natick, Ma, USA Registered: Apr 2002
The HUD is purposley not super-sensitive, in order to filter out high-voltage spikes that can occur in Automotive environments.. Better to be safe than sorry, right? The "fix", is to isolate the 2,000 ppm output from the speedo, and pull it up with a weak resistor to 12v. The '85 speedos seem to be putting out a "-" signal really, so it will pull down the 12v line from the resistor, creating a 12v Sin wave for the HUD to read. It seems to work on the bench, I'm going to hook up the 120mph '87 speedo in a few minutes to see what its signal looks like. Just got home from working on the Fiero, didn't get much done due to a sudden surge in the mosquito population... Must have had a busy week of mating or something! They're vicious... Ok... "Edit / update": I hooked up the '87 cluster on the bench. Guess what? The signal looks exactly the same as the '85 speedo. It's only about .6v. The '86 and higher ECM's must pull up the signal, that's all I can think of.. BUT - if that's the case, why wouldn't the '85 cluster work in my '86 car, while my '86 cluster did work??? Hmm... In either case, I got both of them working on the bench with the addition of 2 resistors. 1 is a 100K ohm going between the speedomter 2,000 pulse output and +12v (turns the wave into something useful), the other is a 50k ohm from the 2,000 pulse output to the input of the HUD. For some reason it wouldn't work just connecting the HUD to the VSS wire after the 100K ohm was installed.. Needs a resistor inline with it. (Even though it already has one on the HUD circuit board?!?!) Anyway, I'm going to hook the resistors up in my car to make sure it's not going to toast the ECM or anything.. (shouldn't, it's really high resistances, so not much of anything can short or go wrong) Looks like this is the fix though, I can either send out the resistors (free of course) or you can get them locally, it would probably be quicker... Or, I could sell the resistors on eBay for $29.95 and call them "20HP computer chips"!! That would be cool... NOT. LOL
[This message has been edited by Riceburner98 (edited 08-28-2003).]
IP: Logged
09:58 PM
Sep 26th, 2003
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
Woah.. been a while since this one was up.. The latest "news" is that I thought I had it working for the '85 speedometers, but nope, it didn't work. For some reason, when I installed the resistors in my own car (86SE) with an '85 speedometer, the HUD worked. (didn't work without the resistors) So I thought I had it nailed, and sent some resistors to Paul in England. He installed them, and poof, no-go. Still nothing on the display. The plan now is to create a divide-by-two circuit to drop the 4,000 pulse signal from the VSS down to 2,000 pulses. Easy, right? Nope... The circuit works perfectly with a signal from my signal generator on the bench, but I just cannot get it to work *at all* with the HUD circuitry. I have no idea what's going on with it. The pulses from my generator look identical to the HUD signal pulses, but it just won't work. I've tried several different circuits, with different chips and different filters on the input of them, and it still won't work. As far as I know, Paul also has also tried an '86 120mph speedo in his car, and it didn't work with that. So... the probelm may be being caused by a combination of the speedo *and* the '85 computer. I'm not sure what to do now for the '84 and '85 cars... Paul reported that it works (but twice as fast) when connected directly to the VSS signal, so the circuitry in the HUD itself should work OK with that. The software just needs to be fixed to work 100% with the 4,000 pulse signal. I have a version that does work, but still only has 1/2 the top speed. (tops out at 70-something mph) I've got to build one and get it shipped off to Oliver, so he can finish modifying the code if he gets the time. Time is the problem - neither of us seem to have any at the moment. As for the last question above - yes, the HUD can do MPH and KPH, for KPH a (removable) jumper is installed in the side of the box. The tach option is still a thought, but nothing has really been done on that yet. Since getting laid of a while back, what little free time (and $$) I had to work on stuff has gone out the window. I'm in school 5 days a week, and usually out on the weekends.. Oh yeah - prices are Red/Green/Amber/Blue - $55/$58/$58/$67, and $2 extra if using Paypal. I'll get one of these things shipped out to Oliver in the morning, if it takes 'till 3am to finish building! - Bob
This installation causes the HUD unit to be permanent and non movable, so you must take time to adjust the glass so the angle allows the reflection directly at eye height.
No pins to stop it, so it just spins! Guess that lets you know you're going too fast!)
As far as I know, Paul also has also tried an '86 120mph speedo in his car, and it didn't work with that. So... the probelm may be being caused by a combination of the speedo *and* the '85 computer. I'm not sure what to do now for the '84 and '85 cars... Paul reported that it works (but twice as fast) when connected directly to the VSS signal, so the circuitry in the HUD itself should work OK with that. The software just needs to be fixed to work 100% with the 4,000 pulse signal. I have a version that does work, but still only has 1/2 the top speed. (tops out at 70-something mph) I've got to build one and get it shipped off to Oliver, so he can finish modifying the code if he gets the time. Time is the problem - neither of us seem to have any at the moment. As for the last question above - yes, the HUD can do MPH and KPH, for KPH a (removable) jumper is installed in the side of the box. The tach option is still a thought, but nothing has really been done on that yet. Since getting laid of a while back, what little free time (and $$) I had to work on stuff has gone out the window. I'm in school 5 days a week, and usually out on the weekends.. Oh yeah - prices are Red/Green/Amber/Blue - $55/$58/$58/$67, and $2 extra if using Paypal. I'll get one of these things shipped out to Oliver in the morning, if it takes 'till 3am to finish building! - Bob
