I was reading about your work on skitime's history page and I am very impressed. One of my favorite mods is the sunbird turbo tach. Can you guys, or anyone else for that matter, be of some assitance in helping me mod it for a v8? I want to use it on my 4.9T project. I saw an article on how to mod a fiero tach for a v8...but is this universal?
i'm gonna be picking mine up from Jim in the next week or so...whenver i can get outta all this damn snow....i want to make an install webpage or something for the modifications in the speedo/tach housing. maybe I can get together with Jim and Dave to setup a webpage or maybe Cliff can add it as a tech article on the forum....
------------------ Eric '87 GT 5-speed Gold/Tan NOW with a 4.10 4-speed 3.1 TDC + other goodies coming summer of '03 -2.8 aluminum head crank, 6" SBC rods, 3.4 pushrod pistons (8.8:1), T3/T4, custom built headers and Y-pipe, 36#/hr injectors OR -2.8 aluminum head crank, 6" SBC rods, N* pistons (11.5:1), 96+ heads, home built equal lenth headers, custom tunnel ram intake manifold, 24 #/hr injectors, and a 100 shot of N20 :)
choices....
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10:08 PM
FieroGTT Member
Posts: 489 From: Hard Hittin' New Britain, CT Registered: Oct 2002
Hey coinball let me know if you want a hand on the webpage, ny email addy is battledroid53@yahoo.com anyone have a pic of this tach, or why it is so special?
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11:58 PM
Feb 20th, 2003
skitime Member
Posts: 5765 From: Akron, PA, USA Registered: Aug 2000
Here's a picture of a whole cluster conversion (unfinished at this pic) that Erwim Adams did. The special thing about the tach is that it contains the Boost Gauge.
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11:08 AM
coinball Member
Posts: 1526 From: Raleigh, NC, USA Registered: Apr 2002
Ski - can you send me those pics you have of the cutting to get the tach to fit? my email is strcture32@aol.com thanks!
WMac - you can just put the tach/boost gauge in the fiero cluster, it does require some cutting but otherwise its a bolt in...no need to put in the entire cluster from the sunbird...
FWIW the other GM TURBO guys have strong opinions on those guages.... inconsistant inaccurate only goes to 15 lbs (because of the 2 bar sens.) so it wont show spikes
Its the first thing they lose when they get serious
I'd stay away
------------------ 84 Fiero Turbo Vortec 4300 Phantom GT L35 block Syclone Intake and ECM T04B H3 Turbo http://www.cardomain.com/id/vortecfiero "Any significantly advanced technology is indistinguishable from magic"
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06:25 PM
Feb 21st, 2003
TennT Member
Posts: 1523 From: Humboldt, Tenn Registered: Nov 2002
Why do you need a 2 bar map when it only goes to 15psi? Isn't that just 1 bar? What would happen if you used a 1 bar map?
Because you have -1 bar of vacuum and 1 bar of boost. Engine off is technically 1 bar (atmospheric pressure) but that is considered 0 boost.
Full vacuum is -1 bar from atmospheric pressure. One bar of boost is +1 bar. Thus, 2 bar map.
The 20 PSI gauge in the TTA takes a 3 bar map. Stock Fiero only uses a 1 bar map. Vacuum to atmospheric pressure. I'm using "vacuum" to mean -1 bar from atmosphere.
I found that once I set the center of the gauge, it read pretty damn close although it wouldn't read full vacuum until I rescaled the gauge and reset the center.
They aren't certainly a precision gauge. But cool enough for our use. I check the true boost with a better meter and watch where that is on the tach/boost gauge. It's repeatable.
[This message has been edited by TK (edited 02-23-2003).]
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09:18 PM
FieroGTT Member
Posts: 489 From: Hard Hittin' New Britain, CT Registered: Oct 2002
The directions mention cutting the traces to Pin 3 and 11 of the thinfilm resistor. But when you look at the tach, there IS NO trace to Pin 3. That lead me to believe the directions are incorrect.
Skitime said he couldn't get the tach to work with these directions, and had modified the tach differently with a friend's help.
I need CLEAR directions from someone who has done the modification. Please post them here. Thanks...
------------------ 1987 GT www.fierosound.com 2002/2003 World of Wheels Winner & Multiple IASCA Stereo Award Winner
[This message has been edited by fierosound (edited 06-07-2003).]
From memory, find the 25054339 chip. Find pins 5 and 8. Follow them to a cap and then on to the resistor pak. Cut both traces to the pak after the cap. Solder a 1M pot across the cap. Adjust at the highest RPM you can (at least 3-4K RPM). They aren't precision meters. If you adjust it at idle it will be way off at the top end.
Pins 3 and 11 of the resistor pak do stick in my head but I can't confirm it. Maybe I'll get one of my SB tachs out and look later.
Here's a picture of a whole cluster conversion (unfinished at this pic) that Erwim Adams did. The special thing about the tach is that it contains the Boost Gauge.
damn that is a really cool setup i think i might have to do that also just totally wicked setup..what year is that from? and could a semi intelligent person do something like that?
I just helped V8Dreamer install one in his car. If you have the gage like the one pictured above with the bold numbers and it just says 'TURBO', it will have an open spot on the board for R14. Just solder the Pot in the R14 position and cut the trace at pin 4 of the resistor chip and you're set. If you have the other style gage that looks more like the Fiero gages, thinner numbers, more graduations on the scale, and says 'TURBO BOOST', it will not have a spot on the board for R14. Just solder the 1M pot across pins 5 and 8 of the tach chip (IC1) and cut the trace to pin 4 of the resistor chip.
On Ryan's car the gauge is very inaccurate. it shows max 5 psi boost, we easily got 10 psi on a mechanical gauge. Same with the vacuum, it's not showing as much vacuum as the mechanical gauge. I haven't looked into how to adjust it.
