Adapt to Factory Tach????

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Apr 5, 2007 | 03:44 PM

67rsss

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Adapt to Factory Tach????

We are intending to use an aftermarket tach we happen to have on the 4cyl setting while we are getting the engine up and running (LS1 into 67 Camaro). At some point, we want to hook the factory tach back up though. Has anyone done this? If so, how?

Apr 5, 2007 | 06:22 PM

01WS6/tamu

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From: somewhere in TX

Is it a cable tach like the early vettes or electric. I am assuming it is eelectric I'm gettin rsty on old iron. I believe It is the same signal that gm used all of their tachs up until they went to the gen three motors and if thats the case the signal can be changed internally in the pcm using a tuning suite like hptuners etc.

Apr 5, 2007 | 11:00 PM

Rodder

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It's electric. You can rescale the tach output in the PCM using any standard tuning software (I used HPTuners), or if you are farming out your PCM tuning you can tell your tuner to scale it for a standard 8cyl tach.

If you get it hooked up and the tach bounces, you may need to put a filter on it like this one: http://www.camaros.net/techref/electrical/tachfilter/

If you don't get any output, you might try a tach adapter like the Mallory #29078 (figure B wiring in the instructions).

Apr 6, 2007 | 11:00 PM

G-Body

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You can either use HP Tuners or EFI Live7 to change the tach output.

There are also a few places that make adapters, dakota digital is one of them. I don`t really see an adapter being advantageous in your situation though since you will need to change other parameters in the PCM with HPT or EFIL7. If the price of those programs scares you off, you can also have the PCM reprogrammed by someone else. Both Speartech and jesse at wait4me reprogram PCM`s for conversions.

Apr 7, 2007 | 08:31 AM

67rsss

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At this point in the game, whats another $1K??? I am much more worried about us getting into the computer and screwing something up. I imagine the cheap handhelds won't do what we want to do, they seem to be for changing the shift points in the A4. The guy we bought the engine from did reprogram for us, but we didn't even think about this parameter. He would be happy to make changes for us, but we do know that at some point we are going to have to learn how to do it ourselves....

Apr 7, 2007 | 08:47 AM

glock73110

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At this point in the game, whats another $1K???.............lol yes that is what I say my swap camaro is a b.o.a.t break out another thousand.........I changed mine to auto meters

Apr 7, 2007 | 10:21 AM

Rodder

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Quote:

Originally Posted by glock73110

At this point in the game, whats another $1K???.............lol yes that is what I say my swap camaro is a b.o.a.t break out another thousand.........I changed mine to auto meters

been there, done that

. I'm $24.5k into my $8k swap project on my Camaro.... maybe we should start telling newbs to figure 3X instead of 2X?

Quote:

Originally Posted by 67rsss

I am much more worried about us getting into the computer and screwing something up.

One of the great things about being able to program it yourself is that you can easily undo any changes you made. HPTuners even keeps a running change log so you can see exactly which parameters you messed with and when you messed with them. The only way you can hurt the PCM is to turn it off in the middle of uploading a tune that includes a full OS flash, and worse case there is you pick up another PCM off ebay for $100 or send your PCM off to someone to unsolder/burn/resolder the flash chip. And normally you don't flash the full OS, just the calibration, and HPTuners can recover from a failure during a calibration upload. As far as hurting the rest of the engine, the two categories of things that could hurt the engine are spark advance and mixture. With spark advance, the knock sensors will probably save you if you go a little too far. With things that affect mixture, just be careful and don't mess with them unless you have a wideband O2 sensor installed.