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Discussion Starter #1
Hey there guys! I saw these nice custom gauges for the Supra at www.speedhut.com and I want to get some. They offer two types of speedos, one goes to 280kph and one goes to 240 kph. Mine currently goes to 240kph (1987) and I want to get the 280 one. So what do I have to change to make mine compatible with it? Do the post 89 supras go to 280? I figure I just have to swap the speedo gear or something. Let me know if you have any info. Thanks alot guys!

Deep_Blue
 

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helps you jump higher
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I don't think it's going to be that easy, chances are it's going to be more work than it's worth, it's not like speedo's are that accurate 120+ I was clocked at 134 when my speedo was at 140 (MPH)
 

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AZmkiii said:
I don't think it's going to be that easy, chances are it's going to be more work than it's worth, it's not like speedo's are that accurate 120+ I was clocked at 134 when my speedo was at 140 (MPH)

that could possibly be b/c youarent running stock tire size /rims
 

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You will need at least the speed sender (whatever its called) that mounted in the tranny and in all likeliness the actual speedo unit. Shouldn’t be too hard to swap at all, especially considering that you are taking the cluster out anyway.
 

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doesn't the speedo just react to how fast the speedo cable is spinning? so if you upgrade the speed sender unit in the tranny it will effect the output rate and thus effect the speedo readout?

AZMKIII, there is also something called CD. the faster you go, the more inaccurate the speedo will be. CD=Coefficient of Drag
 

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edmiston9- what does Cd (Cd is the proper way to expres Coefficient of drag, BTW;))have to do with your spedometer? Cd is a mesure of air resistance, and thus has nothing to do with the mechanicals of the spedo.. Also ma71 recently posted all the gear ratio's and RPM's - MPH conversion chart. you can see how inacurate your spedo is that way. mine is off by about 1.5 mph at 75 mph. but I also have custom wheels, which might have changed the rolling radius. I am just way to tired to figure it out right now:cool:
 
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lmao...can't believe that I actually read that.

What does Cd have to do with speedometer accuracy? Unless you are talking about the drag on the needle as it swoops towards 140...lol.

Seriously though, tire size has a lot to do with it. If you change from the stock 225/50-16 to say a 275/40-17 like a lot of the guys do, your gauge will be WAY off, but it would be the other way around, you would be doing say 130 when you are showing 115.

Back to changing the speedo... I don't think it would be a problem, but you need to ask if the (larger?!) speedometer has a different scale compared to your stock one, or if it just adds more to the end.
 

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AZmkiii said:
I don't think it's going to be that easy, chances are it's going to be more work than it's worth, it's not like speedo's are that accurate 120+ I was clocked at 134 when my speedo was at 140 (MPH)
Thats 4.5% inaccurate -- not terrible for a stock gauge. Most factory speedometers are about 5% optimistic anyway.
 

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Wouldn't the differential be the prime suspect in the difference of speedos between the pre 89s and post 89s?

The gear ratio is different in the back so that would spin the speedo cable differently.


btw...speedhut.com is a nice website, allows you to create your own gauges.
 

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Discussion Starter #11
It's funny but I feel somehow that my thread has been jacked... and I still don't have an answer to my question!!! Is there anyone that actually has experience with this, or do I have to find out the hard way? I'll ask just a simple question that I really need an answer to: do the post 89 gauges go up to 280 kph (or however many mph that is) please let me know. Thanks guys!

Deep_Blue
 

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:scratch:
Damn, I could have sworn that Cd had an effect on the speed that was read on the speedo. I can't even write down how I came up with it now either. :dunno: Oh well, back to the drawing board.
 
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