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> Tachometer rebuild
totle
post Sep 13 2018, 06:27 AM
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Hi,

Anyone that have a DIY description of how to rebuild a 7k Tach to a 10k Tach ?
and from 4 cyl to 6.

I would think that there is someone who has done this.
Any potmeter adjustments, og parts that needs to be replaced ?

I know that NHS does this, but would be nice to do it and just buy a new faceplate
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timothy_nd28
post Sep 13 2018, 06:51 AM
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I have toyed with the idea of doing just this, but I never got into the world of stenciling. The key part of doing this conversion is the faceplate, where would you buy one? Since you can't buy a 10k Porsche faceplate, I think you would be forced to find someone that could redo the artwork on a existing 7k tach.

If you can get past the first hurdle, the electronics would be easy. I would only need to know the angle between each 1k tick mark to be able to calculate the proper gain for the tach drive.
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timothy_nd28
post Sep 13 2018, 08:31 AM
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Trond from Norway has pointed out to me that these 10k dials are readily for sale.

https://www.heiler-tachodesign.de/Tachomete...ithout-red-Area

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If there is any interest from others to convert their tachometer to this 10k version (with new tach guts), I will revisit my DIY tach upgrade post and make updates
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peteyd
post Sep 13 2018, 11:00 AM
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I would be interested in this.

Could you perhaps do one for the 6 cylinders also?

Pete
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timothy_nd28
post Sep 13 2018, 11:26 AM
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The tach drive that I spec'd out in my DIY thread, it can be configured from a 2 cylinder to a 20 cylinder engine.
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totle
post Sep 13 2018, 04:13 PM
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Thanks for sharing the information Timothy
Great DIY thread :-)
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mepstein
post Sep 14 2018, 05:56 PM
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I forgot I have a 10K tach. (IMG:style_emoticons/default/biggrin.gif)


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Mark Henry
post Sep 14 2018, 06:29 PM
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An Ashlock tachadapt will turn a /4 tach into a /6 tach (or 8), just the redline markings would need to be addressed.
It also cleans up tach bounce, MSD issues, etc.
$65 + $3.50 shipping

http://www.ashlocktech.com/

(IMG:http://www.914world.com/bbs2/uploads_offsite/forums.pelicanparts.com-26-1536971529.1.jpg)
(IMG:http://www.914world.com/bbs2/uploads_offsite/forums.pelicanparts.com-26-1536971572.1.jpg)
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PlaysWithCars
post Sep 15 2018, 09:57 AM
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Tach bounce. Now there is something that I would like a DIY solution for. I like the tach scale I have, the tach matches the # cylinders in the engine, but the lazy tach needle and bounce can't keep up with the changes in engine speed. Especially with a lightened flywheel.
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porschetub
post Sep 15 2018, 03:15 PM
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Howard Instruments in Victoria ,Australia do a 10K face if that's any help.
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timothy_nd28
post Sep 17 2018, 08:59 AM
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The Ashlock tach-adapt is the wrong product for what is trying to be done here. The tach-adapt will not re-scale our existing tach to a 10k faceplate. With that said, he does have a product for sale called a "tach-drive module" which is made for re-scaling and could be a good option. Since Ashlock's tach drive replaces all the electrical guts in our existing tach, it still needs to reuse the original movement, so there will still be some needle bounce.

My idea is the same principle as Ashlock's tach-drive module, but you get a new air core motor that replaces the old spring mass movement. New electronics and a new modern style servo motor equals no needle bounce.
Here's my write up: http://www.914world.com/bbs2/index.php?showtopic=216719

So to reinstate the question that was originally asked, can you take a stock 914 tachometer and convert it into a 10k tachometer?

Yes, and there are some company's out there that will gladly do this for you. NHS will take your existing tachometer and convert it for you for upwards of 600 dollars. I think the better question would be "can you convert a stock 914 tachometer to a 10K tachometer for under 100 dollars"?

Either Ashlock's module or my conversion method will have you covered in the electronics department. The new artwork for the face dial is the real issue IMO. It may be worth buying this premade 10k face dial and doing this conversion. But this dial is overseas and might break the 100 dollar budget limit.
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Retroracer
post Sep 17 2018, 12:33 PM
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"can you convert a stock 914 tachometer to a 10K tachometer for under 100 dollars"? is a great question!

Found this thread intriguing; I'm up for trying this with a -4 tach, Tim's updated tach innards (excellent R and D around this Tim, nice work!) and a replacement / hacked 10K face. The German one is a bit pricey but not too bad, noting that the "VDO" label is not present, presumably for legal reasons. I'll investigate the Aussie alternative (thanks Porschetub).

Already stripped the -4 tach, will post progress if anyone has interest. This will be used with a -6 engine running MSD Strassefeuer ignition for the tach output.

- Tony
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mepstein
post Sep 17 2018, 12:47 PM
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Only problem I see with a 10k tach face on a 4 is you are only using 1/3 of the tach face to indicate your rpms and you will have to leave off the redline or it will look dumb having the redline indicated at the halfway point. The 10k tach was for Porsche race engines that actually redlined not to short of 10k. My 3.2 tops out at 6,850.
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timothy_nd28
post Sep 17 2018, 01:29 PM
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Mark brings up a good point. Not many engines rev up to 10k rpm. Perhaps this 10k tachometer is better suited for someone doing a jet turbine project for their 914, so it can show n1 and n2 turbine speeds? (IMG:style_emoticons/default/smile.gif)
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Spoke
post Sep 17 2018, 01:29 PM
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Can a 911 tach be substituted? Don't know if they are the same size as the 914 tach.
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timothy_nd28
post Sep 17 2018, 01:31 PM
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911 and 914 tach sizes are identical
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Retroracer
post Sep 17 2018, 01:43 PM
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QUOTE(mepstein @ Sep 17 2018, 11:47 AM) *

Only problem I see with a 10k tach face on a 4 is you are only using 1/3 of the tach face to indicate your rpms and you will have to leave off the redline or it will look dumb having the redline indicated at the halfway point. The 10k tach was for Porsche race engines that actually redlined not to short of 10k. My 3.2 tops out at 6,850.


My little 2.2l six redlines at 6200, so I do see your practical point Mark! I run a modified 911 tach at the moment:

Attached Image

For me personally though, it's more getting the look to match the factory GT gauge set, as it seems most of them were fitted with 10K tachs (from trawling through the the PBase photos). And yes, I have to change the other gauges to match as well - but much like life, this car is a work in progress....

- Tony
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mepstein
post Sep 17 2018, 02:25 PM
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These just showed up today. I always wanted a set of green gauges and these are from a 66-912. 1/3 the price of green 911 gauges.


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jrblackbox
post Sep 17 2018, 03:42 PM
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QUOTE(mepstein @ Sep 17 2018, 12:25 PM) *

These just showed up today. I always wanted a set of green gauges and these are from a 66-912. 1/3 the price of green 911 gauges.



I assume you are putting them in a 914-4? What is involved? Thanks
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nickg
post Sep 17 2018, 04:42 PM
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QUOTE(PlaysWithCars @ Sep 15 2018, 07:57 AM) *

Tach bounce. Now there is something that I would like a DIY solution for. I like the tach scale I have, the tach matches the # cylinders in the engine, but the lazy tach needle and bounce can't keep up with the changes in engine speed.



I would like to know how to fix the bounce too
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