The 240 is up and running great just t let everyone know. It is now my DD and gets better gas milage then my hog of an explorer. Question is, Does anyone know what ohm resistor to put inline with the tach wire to convert it to my 4 cyl tach? I probed my wires and found out which ones connect, when I finally got it my 4cyl tach read 4.2k and idle LoL. The guy that did my programming briefly mentioned something about a 56... 52... ohm resistor. I dont remember exactly. Thanks guys pics and vids will be up soon!

 

LS1 tach signal output is 4 cylinder by default.

 

Can the ECU be programmed to give 8 cylinder output for tach? When I first hooked mine up I put my Sun tach on the 4 cylinder setting and it read double, changed it over to 8 cyl and it is right on now. Is it possible my ECU programmer (Speartech) set it to 8 cy for me? Whatever the case I am hapy with the way it is working, now if I could just get my darn Dolphin electric speedo to work right.... It stays about 10 mph slow no matter how I set it.

Pat

 

Interesting I think Speartech will have to chime in on that.

 

With HPT I was able to adjust the tach signal to output the correct signal for the stock 3rdGen gauges (8 Cyl). Not sure if Speartech would have set it up that way without asking. As to your speeedometer did that get reprogrammed with the correct gear/tire size?

 

Whatever he did with the tach signal suits me just fine. As for the speedometer, he had the correct gear ratio and tire diameter. I think the issue there is with the gauge. I have been working with the Dolphin folks, but apparently it is an older model and they are having to dig the documentation out of the archives.

Pat

 

Like was said above, the LS1 tach output is already 4 cylinders.

You can't just add a resistor to change the signal. The tach signal is a 5V squarewave signal that gives 2 pulses per engine revolution.

Your tach may be like some other Japanese cars where it runs off voltage instead of frequency.

 

For my '88 BMW/LS1/6/T56 I had North Hollywood Speedometer and Clock build a small converter so my stock, 4 cyl BMW tach would read the LS1 signal. An aftermarket tach set to 4 cyl worked fine but I wanted to run the stock tach and that required a converter.

 

I believe you're all taking the wrong tack on this one. Dakota Digital makes speedometer adapters and tachometer adapters to match strange outputs to normal instruments.

Their speedo adapter changed my transmission output set for a 2.47:1 differential to match the new 3.07:1 diff in my Mercedes. It took maybe ten minutes to install the unit behind the instrument cluster, another fifteen to find the right wire for the speedometer (instructions from a friend were wrong), then down the road with a GPS unit to adjust the Dakota so my speedometer is perfect.

That unit will adjust the 4L65E output to the Mercedes speedometer and whatever the LS6 wants to give me for a tach signal, I'll use the Dakota adapter to make it read right on the Mercedes tach. It's easy to do this. If it was me, I'd give them a call to verify if their equipment will fix your problem.

http://www.dakotadigital.com/index.c...cat/cat287.htm

 

It is possible that speartech changed the tach output if he knew you were swapping it into an older car.

For the speedo does it need a sine wave AC input or a square wave DC input, and where are you connecting it? The speedo output from the computer is square wave DC, if you need to feed the speedo sine wave AC then you will have to tap into the VSS output before it gets to the computer.

 

I just used EFILive to change my tach signal to read correctly very simple. Also I changed the speedometer signal by inserting my tire size and gear ratio. The gear ratio is calculated by EFI and mine states 3.73 which is a good thing as I suspected it was that ratio as my axle stamp states 2.71 from the factory. Now my speedo is an Autometer and is self calibrated so I now need to drive a measured 2 miles and recalibrate it again.

So get your PCM adjusted for the tach by having someone else set it or you purchase one of the tuning packages LS1Edit, HPTuners, or EFIlive. The formula in EFI is P=24/(N*2) where N is unitless. In mine N was set to 6 I had to change it to 4 to get my tach to match what EFI stated it was reading. I could change it from 1 to 16 so I could compensate for any tach if there were some kind of inherent error. So I could have done 4.2 or something to try and get it spot on.

I personally went for EFILive as they seem to be keeping up with changes and after you purchase they give you all software updates free for life all downloadable from their website.

They all should be good packages to use. Just for a side note John at SpearTech was in on the ground floor in helping develope LS1Edit so that should tell everyone something of his expertise.

 

My Speedometer is an aftermarket unit from Dolphin Gauges/EZWiring. It receives an electronic signal input, and has 8 dip switches on the back to adjust it. When I was using it with my T350, I had a signal generator plugged into the speedometer cable socket on the trans. I have been assured by the Dolphin people that it will work accurately with the LS1 ECU signal once we have the settings correct. The problem is my unit is an older one and the documentation that they need to give me the proper dip switch settings is not immediately available. They are digging it out of their archives. As for the Tach, I may have mentioned to John what my plans were. At any rate with it in the 8 cylinder setting it seems to work perfectly. My shift points are right on too, so he has the gear ratio and tire diameter correct. Sorry to hijack the thread from the original posters question. And thanks to everyone for their suggestions.

Pat