Good tach recommendation

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jstoezel
Posts: 207
Joined: September 19th, 2010, 6:21 pm

Good tach recommendation

Post by jstoezel »

Hi,

My tachometer bounces quite a bit when the engine RPM goes over 6000. It makes it difficult to shift consistently (or monitor the engine RPM past this point). It might not be so much an issue in FV where ultimately most end up shifting by ear, but I would like to have a better idea of where I am in term of RPMs, for comparison purposes. When I say bounce, I mean oscillating with a 300RPM amplitude.

Would valve floating cause the tachometer to bounce? My engine is not very healthy past the 6000 RPM mark, it seems to float a bit.

Or is it because of a cheap tachometer? I run Pertronix point-less system by the way. I'm running with a $25 tachometer, mainly because that's the only one I could find locally in 2.5" diameter (I have limited dashboard space, like everybody I guess). Could somebody recommend a good quality tachometer, preferably with adjustable shift light?

Thanks,
Jean
Jean-Sebastien Stoezel
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Dietmar
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Re: Good tach recommendation

Post by Dietmar »

Jean:

Have always been happy with AutoMeter.

Dietmar
http://www.quixoteracing.com
jpetillo
Posts: 759
Joined: August 26th, 2006, 2:54 pm

Re: Good tach recommendation

Post by jpetillo »

Same here - I've had Autometer gauges in two cars. I run the Autometer analog tach with an Autometer shift light -the one with the pills to select RPM. The only time I've had a jumpy needle like you described is when I had ignition problems. That's not to say that you have ignition problems, I'm just relaying my limited experience. Also, analog gauges are not always accurate, so 6000 rpm may be higher or lower, in reality. But, they are consistent, so if it shows 100 RPM higher, then it's 100 RPM higher!
SR Racing
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Joined: June 24th, 2006, 1:58 pm

Re: Good tach recommendation

Post by SR Racing »

Jean, Yes the Autometers seem to tbe the best buy for the $. The VDO's are usually ok, but seem to often develop the symptoms you describe.

The valve float won't cause the problem you describe unless it was VERY bad. A faulty ignition can cause this problem on poorly designed tachs (or some data acquisition systems.) A good tach uses a circuit that counts pulses of a certain duration. Some tachs are very sensitive to the duration of the pulse and noise. In those cases a defective condensor can be the cause. Since you are running a Pertronix you don't have the condensor, so I suspect its the tach.
Matt
Posts: 86
Joined: June 24th, 2006, 7:55 pm

Re: Good tach recommendation

Post by Matt »

The tach neddle broke in my AutoMeter on my 20 year old car. I sent it back to Autometer expecting to pay for the repairs.
They sent the repaired tach back with a no-charge bill and they paid the freight.

What more can I say.

Matt
jstoezel
Posts: 207
Joined: September 19th, 2010, 6:21 pm

Re: Good tach recommendation

Post by jstoezel »

Hi:

Thank you for the replies. I checked the Autometer tachs and they are at least 4 times what I paid for the one I'm currently using... I guess I got what I paid for.


Jean
Jean-Sebastien Stoezel
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FV80
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Re: Good tach recommendation

Post by FV80 »

Jean,
Get a data system that has settable shift lights. Some cost no more than a decent tach. You will have a nice indicator for shifting and you have something to look at when you're goofing off after a session :-).
Steve, FV80
The Racer's Wedge and now a Vortech, FV80
brian
Posts: 1348
Joined: June 26th, 2006, 12:31 pm

Re: Good tach recommendation

Post by brian »

I chased a bouncy tach through several tachs and found a worn shaft on the distributor that was causing the issue. Going to a modern data acq. system carries issues as well. Our old ignitions are a real challenge for most systems since many were designed to work with a tach output from the ECU. Our ignition signals are too dirty to run many data systems. Some, like AIM, offer filters but the best approach is to by pass the ignition all together and use a magnet on the front pulley and a halo sensor for the DA system. Go to the Summit Racing website and look at their options for tachs. Summit carries zillions of tachs including inexpensive shift lights.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
jstoezel
Posts: 207
Joined: September 19th, 2010, 6:21 pm

Re: Good tach recommendation

Post by jstoezel »

Hi Steve:

I would love to get one of those data acquisition systems, a Mychron 3 for example, have been looking for that FV package on the SRacing website... Similar to yours would be great. Still a bit more money than I can spend though...

I end up doing more data analysis on iRacing than I do on my FV. The data logger on iRacing comes for free. I built a microcontroller based datalogger that I used for a while on my FV, that stores data on a microSD, with built in accelerometers and 10Hz GPS. But I always end up spending more time debugging loose wires and damaged components. I can built printed circuit boards and program computers, but I can't build reliable and waterproof enclosures to protect them...

Jean

FV80 wrote:Jean,
Get a data system that has settable shift lights. Some cost no more than a decent tach. You will have a nice indicator for shifting and you have something to look at when you're goofing off after a session :-).
Steve, FV80
Last edited by jstoezel on October 24th, 2011, 3:57 pm, edited 5 times in total.
Jean-Sebastien Stoezel
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jstoezel
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Re: Good tach recommendation

Post by jstoezel »

Hi Brian:

Thanks for the suggestion. The engine is at the shop, will have to ask the engine builder to check for a worn distributor shaft.

Jean

brian wrote:I chased a bouncy tach through several tachs and found a worn shaft on the distributor that was causing the issue. Going to a modern data acq. system carries issues as well. Our old ignitions are a real challenge for most systems since many were designed to work with a tach output from the ECU. Our ignition signals are too dirty to run many data systems. Some, like AIM, offer filters but the best approach is to by pass the ignition all together and use a magnet on the front pulley and a halo sensor for the DA system. Go to the Summit Racing website and look at their options for tachs. Summit carries zillions of tachs including inexpensive shift lights.
Jean-Sebastien Stoezel
WCMA FV #0
mthomas
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Joined: November 12th, 2011, 12:19 am

Re: Good tach recommendation

Post by mthomas »

If you haven't given up on the cheap tach yet, try installing a diode in the wire from the neg. side of coil to tach. with the stripe on the diode towards the tach. $.50 cent item, fixed the problem with my cheap tach. Diode #1N4005.

Mike
SR Racing
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Joined: June 24th, 2006, 1:58 pm

Re: Good tach recommendation

Post by SR Racing »

mthomas wrote:If you haven't given up on the cheap tach yet, try installing a diode in the wire from the neg. side of coil to tach. with the stripe on the diode towards the tach. $.50 cent item, fixed the problem with my cheap tach. Diode #1N4005.
Good idea, BUT the pulse from the ignition that the tach generally gets is a Ground (-) thus you want the cathode (banded side) of the diode to be nearest the coil. However, there is enough EMF noise there that it MAY work either way. (Never tried the diode thing in this way, so I am just talking theory.) BTW lots of other cheap things also can work. (a 25 cent resistor/cap circuit, etc.) I did fix an old indy car dash in a F3000 car with a diode and resistor to ground. Prayer can also work. :)
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