LS1 VDO Tach

[macloft]

Help. I have connected my VDO tach up to the wire from my LS1 PCM that is the engine speed signal wire. But I get no reading. Anyone out there with a LS1/ VDO Tach? How have you connected it up? I am told I could use a feed from the alternator. Is this correct?
Thanks
Bruce

[tony martin]

Tach Adapter From Msd:d

[BMK]

tony martin

Tony,

Did you make the Run n Gun this year?

All well at BDR?

[cobbindale]

Hi Bruce,

Had the same problem with mine. Sent it back to Howard instrument to be recalibrated. The square wave voltage output is lower than the standard set up of the gauge at about 5 volt from memory. The standard gauge is set at 8-9 volts minimum.
If you speak to Roger about this, he will know whats going on as I sent him a printout of the wave form generated from the ECU (PCM).

Hope this helps

Dale.

[sideshow]

i sell tacho boostes for 60 bucks

much cheaper than msd ones

i work with problems like this much more than anyone else around

as i wire up many weird stuff into weird cars

so just pm me if u have any elect speedo probs or tacho probs


also set yr tacho to 4cyl for an ls1

[boxhead]

My tacho is reading low, I am guessing this is for the same reason?

If so would one of these "Tacho boosters" help me?

[sideshow]

no yr tacho must be set to 4 cyl

[GlynMeek]

I followed similar 'advice' about buying the 'tach adapter'...and did. No use at all...waste of money, gathering dust. Turned out that all that was wrong was I had the microswitches on the back of the VDO tach set incorrectly. Before you spend ANY money on 'tach adapters' or 'boosters' from anyone, experiment with these microswitches a little bit. Sorry Sideshow, the tach adapter MUST be set to 8, sometimes the switches make it look like 4, but it's just the way the documentation (online if you need to get it!!!) makes it look!

let us know when you solve this!

Glyn

[sideshow]

i just wired up a tacho today on a vt vx ls1
had to set it to 4cyl 2pulse engine otherwise the tacho read 400 rpm at idle
instead of 800 rpm

and every other ls1 i have fitted tachos too u have to set it to 4cyl and not 8 cyl for it to be accurate

anyway see if yr gettin a pulse to the tacho
if u r and its still not accurate then u might need one

i do not have a database of what tacho needs one or not and for which engine i just keep them in stock and use them when i want

but the msd one os 150 bucks wich is a rip off compared to how many i sell
u would make no money on the msd ones at 150 each

[boxhead]

Thanks Sideshow, I will slide out out tonight and take a look.

We posted at the same time,
Mine is reading about 400 at idle, so I reckon your right.

[Aussie Mike]

Originally Posted by GlynMeek

Sorry Sideshow, the tach adapter MUST be set to 8, sometimes the switches make it look like 4, but it's just the way the documentation (online if you need to get it!!!) makes it look!

let us know when you solve this!

Glyn

Hi Glyn, When using any tach with an LS1 the tach definitely needs to be set for 4 cylinder. The LS1 uses 8 individual coil packs each with it's own in built driver circuit. The ECU runs them in 2 banks and only takes the tach pulse from one bank hence the 4 cylinder setting.

On a conventional V8 with a distributor, yes set the tach to 8 cylinders. The LS1 is a bit of a different animal.

I'm using an Autometer 5" monster tach and it has no trouble running off the lower signal level.

Cheers

[boxhead]

Thanks Mike, I will now how mine is in about 20 minyutes (how long it takes to get home, crawl under dash, flick the button and start the car)

[Aussie Mike]

Cool. I might have to fire mine up tonight too. It's been a week or two since I heard it.

Cheers

[boxhead]

Yep, my tacho now reads correctly

[GlynMeek]

Mike...Sideshow...mea culpa, I stand corrected. I was speaking from the position of an American Ford 302, and like a complete wally, didn't read that you were talking about an LS1. I shall remove my Americanized pommie a$$ from this thread and apologize for interfering in Antipodean threads!

Forgive me, I was trying to help!

Regards and good luck

Glyn

[Aussie Mike]

No problem Glyn, we apreciate your input.

We do some funny stuff with Cobra power plants down here.

Cheers

[GlynMeek]

Thanks Mike...as a former pom, my recollection is you do funny stuff with LOTS OF THINGS down there...rofl!

Glyn

[macloft]

SORTED
I have had a number of people contact me asking if I had fixed this problem.
Well thanks to sideshow I went down the road and brought a 680ohm resistor from Dick Smith for 4 cents and soldered this between the 12v ignition wire and the tacho input wire which basically jumps a 5v signal upto 9v and there you go a tach signal.
Thanks sideshow. THIS IS WHATS MAKES THE COBRA SITE WORTH WHILE WHEN YOU GET HELP LIKE THAT.

[Tenrocca]

tried that - and still no luck . howards are going to recal my tach - but I just wonder if the tach signal is different between the LS1 ECu and the E38?

[sideshow]

e38 u might need the retune the ecu the resistor trick wont work on an e38

there is another little trick some dont know about the e38 and tacho signal

u have to find out if its set to crank or frequency

depends if its a usa based tune or an aussie tune

another thing we have come across is

we found one booster that works well with the e38

unfortunatey its 130 bucks

ive tried my cheaper 60 dollar tacho boosters but they didnt work

the l76 into a boat needed this tacho booster

the e38 has very very weak signal


like justin and i told u


we have done alot of research on the e38 and most tuners out there only know how to get power out of them

most dont know the problems with the throttle and the fans and the tacho

anyway see how u go but tell howards its a bloody weak signal