Author Topic: More tachometer questions/options (Read 2909 times)

somepunk22 · « **on:** May 04, 2008, 09:35:52 am »

Is there a different alternator pulley size between AC and non AC cars?
How about swapping the vacuum pump for a distributor and running manual brakes?
Or would it be possible to run an electric speedo and also run a tach off the 020 MK3 hall sender?

RabbitJockey · « **Reply #1 on:** May 04, 2008, 05:16:17 pm »

there are different pulley sizes... but honestly if you just convert one like in the faq, it's easy enough to tune them in, theres only 1 adjustment

Baselyne · « **Reply #2 on:** May 06, 2008, 06:36:30 pm »

i was wonering this also about the dist in place of the vac pump and just use the regular sending lead for dc current

no need to w terminal and could leave out buying a converter

burn_your_money · « **Reply #3 on:** May 06, 2008, 07:02:55 pm »

I don't know a whole lot about gassers and their tachs but you would also need a coil and all the wiring mess right?

TedV · « **Reply #4 on:** May 07, 2008, 08:48:21 am »

Quote from: "Baselyne"

i was wonering this also about the dist in place of the vac pump and just use the regular sending lead for dc current

no need to w terminal and could leave out buying a converter

I thought about that but wasn't legal for my autocross class. the intermediate shafts have different gears between a gasser and diesel. You might be able to use a gasser shaft and a hall effect dist to get a pulse from. Not sure if you would need to boost the signal or if the signal from the hall trigger would be square enough for the tach. When I saw the dist would not mesh with the diesel shaft and it rotated the opposite direction, I stopped thinking about it.

regcheeseman · « **Reply #5 on:** May 08, 2008, 12:41:42 pm »

convert the gasser tacho as per my FAQ

Easy to get a w term signal from an alt that doesn't have one.

somepunk22 · « **Reply #6 on:** May 08, 2008, 10:24:42 pm »

I'm basically looking for other options besides the W terminal. I will be using an aftermarket tach and speedo. I already have the MK3 electronic vehicle speed sensor. It is a hall sender. Why not use it for both?

Vincent Waldon · « **Reply #7 on:** May 08, 2008, 10:38:00 pm »

The MK3 Vss sensor *is* a hall effect transducer, but it is reading vehicle speed off the final drive. Not related to engine RPM.

Or perhaps I'm not understanding what you're trying to do ??

In terms of replacing the vac pump with a distributor... besides the fact that the gears won't mesh there's the issue that disk brakes *must* have a brake booster. The last VW that didn't need vacuum assist was the 65 Beetle which had all drum brakes... a favorite for EV conversion in the 90s because of this fact.

Actually, that's what you could do... remove the vac pump, swap IM shafts, oil pumps, add a distributor, fake an ignition signal, and run an aftermarket vacuum pump used for EV conversions.

If you want the aftermarket look there's a VDO tach that's compatible with both gas and diesels... one wire to your alternator.. done.

Autometer also makes a diesel-compatible aftermarket tach with a sensor that straps on to the alternator.

somepunk22 · « **Reply #8 on:** May 09, 2008, 03:06:48 pm »

Thanks for clearing that up. Not really going for the aftermarket look, just want more gauges then the stock set up. Radio will be gone, and I'm laser cutting a piece of aluminum for my dash. Hopefully work on a few templates tonight to figure out how many I can fit on there.