Please excuse my ignorance, and I have searched for this but...

How would I go about modifying the shift points/timing on my EF I6 Auto. I have 3.9 gears in the a** and it is really hard to get a consistent dyno run as it keeps kicking back to second at 1/2 throttle.

Is it even possible??

firstly, how have you corrected the speedo, without messing up the shift points after the diff change?

I changed the speedo drive gear to a black one (23 tooth if remember right). The speedo only 10-12k's out, but that soon to be fixed with police cluster.

Does the drive gear have something to do with it?

yes that would affect shift points. the search function isnt up & running yet which is a shame cause this has been discussed in detail in a couple threads.

basically, if you had left the original speedo gear in after the diff swap, your speedo wouldve been way out, but your shift points would stay correct.

its when you go to correct the speedo with different speedo cogs, or an electronic speedo corrector is when you fixed the speedo reading, but then the ECU sees a modified speedo signal and f**k the shift points.

The problem with an automatic car is the shift points will be thrown out once you correct the speedo with the kit. In theory, you must use 2 speedo correctors, one that intercepts the signal going to the dash to correct the speedo, and a 2nd corrector changing the signal coming from the dash to the ecu. You use the 2nd unit to change the signal back to the original "wrong" signal so the ecu keeps shift points normal.



However my theory is you might be able to get away with one single corrector by cutting the dash speedo output wire and tap into the gearbox wire BEFORE the speedo corrector so it sees the original signal. Only thing is im not sure if the signal is converted when it goes through the cluster, so it will only work if the signal uses the same voltage/frequency for the dash input & output wires.

That last one makes sense... would it help if I put the standard brown cog back into auto and used the police cluster to adjust speedo?? Can I even do this on the police cluster??? Save me a hundred bucks if it cant.

police cluster can only change reading by up to 10%. im not good at maths, but thats not nearly enough to correct an ecu designed for a 3.08 ratio.

plus you would still be mucking the shift points as it leaves the cluster via speedo output wire to the ecu

You really only need one speedo corrector, to correct the speedo. you will need to modify the wiring to pass the uncorrected signal to the ecu though.

When i looked at the wiring diagram for my EB it showed the dash and ecu wired in parallel, so the signal to the ecu is not modified or subject to the dash. So it seems to me that you could just put a single speedo corrector into the dash wiring only.

A question is though, are the shift points really right even by the original signal? Or at least, could they still be better? I put large wheels on my EB and even in sport mode i would have preferred the shifts to create a bit more revving. For someone putting a lower diff ratio in it might be the other way, but then you might be okay to run it in normal mode rather than sport, and use sport if you really want to kick a***. So maybe in that case there is no problem.

[quote="66 coupe
You really only need one speedo corrector, to correct the speedo. you will need to modify the wiring to pass the uncorrected signal to the ecu though.[/quote]

That's exactly what I was thinking. What is the correct/best way to wire in a speedo corrector.

The way we do it is cut both white wires from the cluster, join them together and connect to the input of the corrector, and then connect the output of the corrector back to the input of the cluster.
Our correctors are designed specifically to operate in this configuration as the cluster no longer supplies the required voltages on the signal lines.

Ok, sounds simple enough... where can I get one of these speedo correctors? and are they adjustable as there might be another diff gear change on the cards.

Appreciate all the advise people... THANKS!!

follow the link in my sig

That actually confuses the crap out of me, but i guess i would just work it out if/when i come to it.

With that setup you could play with the speedo drive gear to your hearts content, altering the revviness to suit your needs/desires. I'm getting a bit confused by this, either the drive gears designed for ever larger diff ratios would give more revviness, or those designed for ever smaller ratios would give more revviness. Can anyone justify which?

Last edited by relaxed_diplomacy on Wed Jan 28, 2009 11:44 am, edited 1 time in total.

not entirely correct, if you change the speedo gear to a different one, it will hit the rev limiter before the trans changes up to the next gear.
If you want it to hold gears longer than it does in power / normal mode, then shift manually.

As i try to sort myself out i edited my above post, and now see you have already responded, but i think your response is no less relevant.

In sport mode will full throttle see the trans running all the way to just a fraction below the rev limiter before changing gear? My limited experience says there is a significant gap that could be closed without overstepping the mark, if you are careful.

Even so, you could see it the other way, you have improved normal driving, and when you want full throttle you change manually or just back off the throttle a fraction so you reach the speed required and it changes gear without hitting the limiter. Or just wait for the limiter and then back off a fraction and it should change up.

If there was an issue i think i would only really have concern with it with respect to overtaking.