Aftermarket Tach

[Preloader]

If you're suggesting I'm not enjoying the hell out of my build, you really need to catch up on some reading.

Because so far nothing I have done is ridiculous.

 

[theenico]

The 1.4t will out run the tach in 1st gear even bone stock. I thought something was wrong with my car when I first got it because, under WOT acceleration, I would hit the rev limiter even though the tach was only saying 6000rpm. In second gear the acceleration rate of the engine was slow enough that it wasn't a problem.

As you increase the ability of the engine to accelerate quicker (tune, lighter car, gear ratios, etc.), the tach lag just gets worse. I'll bet your car is to the point now, where the engine can outrun the tach in second gear also.

 

[Preloader]

Don't forget lighter flywheel. And I think I might be outrunning the rev limiter, I know that sounds impossible, but between 1st and 2nd, when its winding up, cutting out the spark doesn't instantaneously stop the crank momentum.

 

[Swordsmith]

Of the two, B. But how about C: on top of the speedometer cluster (not the tach, the speedo). That's where I keep my UG mount and I think it interferes least with visibility and doesn't draw my eye away from the prize when I'm glancing at it.

Or D, over top of the current tach, which I still think is a plan, despite finding more and more things that are on that tach cluster.

(edit to add) and then there's the time when I outran my speedometer. Really messed it right up there! Those two semis are NOT going 96mph, they just aren't.

 

[laborsmith]

Unless you are in Texas. They convoy and communicate and drop their speeds as if they know there are radars up ahead. The drive from Fort Bliss to Texarkana is unholy long but tracking with the semis helps it pass quickly.

Uh, quickly used as a relative term.


Laborsmith

 

[Preloader]

C

D

D will not work with this monstrous tach, It almost touches the steering wheel.

But I do like C, there is a nice valley behind the Speedo for it to rest in.

I may put these 3 options in the form of a poll. Not that fuqs will be given, but just curious what the majority thinks.

 

[sx sonic]

C- Has my vote by a mile. Might need to cover up the stock tach to keep your eyes from trying to track all the movement.

 

[Wong]

B has my vote....but put the light on the other side, down by the zero.

 

[mitdr774]

A or C.


Even my weak ass 1.8 can overrun the ability of the tach in first. I would have figured that GM could have solved this issue by now.

 

[wasteoffilm]

Hate to be negative, but can we even hook up a tach to these coil packs? If you are only getting the signal from one coil, your tach is going to read 1500 RPM at 6K. Don't mind me if I'm out of line, I'm used to carburetors.

 

[wingman]

C with the light mounted at 5k

 

[Preloader]

Hate to be negative, but can we even hook up a tach to these coil packs? If you are only getting the signal from one coil, your tach is going to read 1500 RPM at 6K. Don't mind me if I'm out of line, I'm used to carburetors.

It can be done. Just not as simple as hooking a wire like on a standard coil distributor.

When I figure it out. The next guy won't have to.

 

[rdss]

Each pin has a job and four individual pins on that plug will signal an event to fire for each plug. It will just take a diagram or some time probing.

 

[Preloader]

That is what I'm hoping.

 

[RS Turbo]

Tach input comes from a 60X crank sensor. There are 58 triggers per rpm to the ECM. It is very accurate and Fast. The problem is the tool reading the info update rate is slow so you can see it. This is refered to as a buffered baud rate. The ECM has a Tach output wire that converts the RPM to a usable signal. The problem is I can not locate the wire color or position. I will Attempt to get this from Engineering for you. The reason there is 58 inputs per RPM is used for accuracy in VVT from the cam phasers, Fuel delivery, and Ignition timing. Again the numbers change faster that you can read them. The Ecm sends the rpm from the high speed lan to the BCM that sends it to the Cluster on the Low speed lan data bus... Mystery Solved for all that wondered

 

[RS Turbo]

Do not use Ignition coil inputs.... They usually fire on both compression and exhaust strokes for each cylinder

 

[$ub$onic]

So the plugs ignite for both compression and exhaust?

 

[RS Turbo]

Yes they have for years!

 

[RS Turbo]

They ignition cassette is connected to 2 plugs per coil just like other engines that have coil packs, It is actually 2 small coil packs.

 

[rdss]

Thanks for the input RS Turbo! I'm sure Derp looks forward to any update on the ECM pin out for the tach.