Just picked up a G-Tech Pro and started setting it up yesterday. Have it completely programed with the exception of the RPM pickup, which I'm having trouble with. Has anyone else had any luck calibrating RPM with the G-Tech on their LNF?

Weather sucks around here right now so I haven't really been able to play much. Will post graphs when things clear up.

 

Those things kinda suck from the tests I've seen

I know the original G-Tech Pro I had was awful at being accurate

 

Yeah... I did a lot of reading before I purchased one. I'm pretty confident that I can get consistent results with it. The majority of complaints were about consistency, but once you become familiar with the settings and variables that can affect consistency they seem to be working pretty well for people.

If I can just get this RPM thing figured out, then I can move on to hitting the road with it.

 

I've got the exact one. Made it work NO PROBLEM in my truck... can't, for the life of me, make it read the RPM in the balt.

 

They rely on picking up ignition pulses through the electrical system and some cars control EMI/RFI very well and it can be difficult for the G/Tech to read anything over the cigarette lighter/accessory plug. There's not a ton you can do but on some cars people have had luck with loading the electrical system by turning on the headlights and rear window defroster while trying to get the G/Tech to read rpm.

Thinking of how it should be working to pick up a rpm signal, if that doesn't work I thought of an idea but never had a chance to try it since I never upgraded to the newer G/Tech. The idea is to inductively provide a path between the primary side of the ignition coil wiring to the the cigarette lighter. To do that you could pick up some 18-gauge wire. You'd then find the positive wire going to one of the ignition coils and wrap the wire around the outside insulation of that wire two or three times to start with. You would not want to splice or cut any wires, instead only wrap the plastic/rubber insulation of your wire around the outside insulation of the coil wire. Electrical tape it in place (I prefer 3M Super 33+), run it into the car, and repeat it on the positive wire for the cigarette lighter.

To do this safely the best bet would be to use an oscilloscope to make sure you aren't getting a large inductive voltage spike on your signal wire. With only a couple "coil" twists it shouldn't cause any issues but I can't guarantee it. And for a couple other disclaimers, I can't say for certain that this would be enough to get the G/Tech to read and it does have the potential to introduce EMI/RFI into the other electrical systems. So proceed at your own risk.

 

If it's trying to read a spark signal, it will be very tough. Dyno couldn't get an accurate read on mine...or if it did, then it meant the car is sparking twice under heavy boost after 4000 rpm or so. Anyone know if it may do this?

 

OK, I just set up the G-Tech in my 95' GMC Jimmy. To answer the first question, the G-Tech is pretty amazing. Works like a charm and seems to be very consistent. I have made 5 runs in Drag mode now and they seem to be very reliable. The features of the latest G-Tech are pretty extensive which is exactly what I was looking for... not just a nice read-out.

Still having the RPM issue with the Balt, however. I will try the ignition coil suggestion and see if I have any luck.

Someone on another forum also suggested running a 12V cigarette accessory directly off the alternator.

 

The one thing that always threw off the original G-Tech was body roll, I wonder if they manage to fix that.

 

Not sure... the one thing that seems really unclear is how the G-Tech handles elevation changes as well. Not sure if either of these are a big issue for road racing. Seems to me that they would affect your acceleration performance data and horsepower data, but even G-Tech claims that the proper method of measuring horsepower is in drag mode where there would likely be no elevation change or body roll. Apparently there was an issue with pitch change from hard acceleration where the front of the car will raise. They have provided a calibration to adjust for this effect, as well as a method for measuring your pitch factor.

 

pitch factor = body roll; but yea, an un-level surface would affect it too. With a sensitive enough accelerometer and a good calibration you should be able to come up with consistant and accurate results.

 

Here is a comparison of 3 quarter-mile runs with the G-Tech in the Cobalt.







This is a close up of the launch. Here you can see exactly where the difference in times occur.



Now if I can get the RPM to work properly, I'll be extatic. Honestly, I'm really impressed with the accuracy and consistency of the G-Tech. Did notice that the speedometer in the Cobalt is slow at speed.

 

I like how much faster your car is than mine! I have a Gtech Pro RR meter too. Would you be able to send me some of your run files by e-mail? Gtech used to have a forum where people could exchange run data, but the forum isn't working now.

 

I'm kinda shocked they don't have an OBDII interface cable on those things by now. Getting the real VSS, RPM and other data would be a snap instead of relying on inductance and such.

 

+1! I couldnt get mine to work either....some sort of interference from the car caused erratic RPM readings. I had bought the Gtech ProRR a couple years ago for my Corvette and it worked pretty good, but when I tried it in the Balt nothing.

 

I like your idea and I may try it. But, I have one question. You said ..."wrap the plastic/rubber insulation of your wire around the outside insulation of the coil wire. Electrical tape it in place (I prefer 3M Super 33+), run it into the car, and repeat it on the positive wire for the cigarette lighter"

Where should the other end connect in the car (for the 1st wire)? I am assuming that it would attach to any grounded piece of metal.

You said to repeat it on the positive wire for the cigarette lighter. So, you would have both the ground and the + cigarette lighter wire both inductively wrapped around the same ignition wire and taped into place so it doesn't fall off?

 

The idea was to try to get some of the ignition pulse noise (which the G/Tech-Pro detects and uses to determine rpm) onto the wire where the G/Tech gets power. To do that I was thinking about wrapping a few loops of wire still in its insulation (not the bare wire) around one of the leads to one of the coils. Then run that wire into the car and into the dash or console cigarette lighter area to whichever one you use to power the G/Tech. Then wrap the insulated wire around the positive lead to that outlet.

I'm not even sure that would work but it should be cheap and easy to try. Since you're essentially making an inductor I'd start out with a just a few turns of wire around the ignition coil and cigarette lighter wires and increase it by a couple turns at a time. Potentially this could induce some noise in radio or other onboard electronics.

To get around that you might also run a new power wire just for the G/Tech and bypass the factory wiring harness where the lighter outlet receives it's power. I'd have to check a wiring diagram to see if there is any noise trap or filter between the power distribution block and the interior harness and cigarette lighter, but if there was that could easily be filtering the already quiet ignition background noise. Find a spot at the distribution box or another underhood positive voltage source and run that directly into the car to power the G/Tech. Just make sure to use a grommet in the firewall and fuse the wire close to the point you tap into.