jetlude

How accurate are they?

rorik

Is that the one that picks up your rpm signal through your cigarrette lighter? Or is that the "Pro" version.. how the hell does that work? (or does it work?)

If it really could do that, could you use its graphs of your torque curve to tune your ignition without using a dyno?

RC000E

I've actually used G-tech for years now due to the lack of a dyno in my area. Here's the lowdown....

The Gtech is a highly accurate deal, but you have to understand what you can take from it based on how it measures the information, and how it presents it to you. Is it a tuning tool....absolutely. I'll elaborate though to be clear.

Gtech is DEAD ***** accurate on 1/4 mile et's, 60', 1/8th mile...basically all your acceleration timing, etc. It is also dead ***** accurate with lateral loads and braking distances, etc.

The mph is very close to accurate, but is effected by vehicle squat or nose lift, but there is a thing called pitch factor that allows you to "tune" for accuracy. Worst case, your mph in a 1/4 mile run will be +/- 3 mph, but tuned properly they can be dead *****.

Now, on to the hp and tq curves, measurement, etc. The issue with Gtech is it bases it's calculations on acceleration, vehicle weight, the rpm signal, and speed. Your vehicle during a hp run is affected by wind, uneven pavement, uphills, downhills, and more importantly wheelspin. You also lose power due to rolling friction, aerodynamic losses, etc. All these are things that a dyno controls because it keeps the car stationary.

The fact is though, that if you can do a pull in a gear with no wheelspin, on a generally flat road, and do your testing, tuning on that same stretch of road in similar conditions, you can tune with it. It will give you a very accurate tq and hp curve from which to tune. You cannot take the numbers to heart though, as they are very low due to the losses I mentioned earlier.

If you can learn to be as consistent with the Gtech as possible, and keep the runs objective as far as the location goes, then it can be used to do SOME ignition tuning...I've done it MANY times.

The rpm signal issue is pretty simple actually. Yes, it does get the rpm from the cigarette lighter. To put it simply, the Gtech unit listens to your alternator. You ever here a person have speakers in their car and when they drive they sound like an audible tachometer....same thing. It picks up the signal and requires you to do a calibration to match it.

I have the Gtech RR and overall I'll tell you, I love the thing. Am I saying it can take the place of a dyno....hell no. It CAN though help you tune, get you pretty damn accurate et's and mph (based on the road your on...if it's flat), and for suspension tuning and braking tests it's awesome. The RR also datalogs and there is a mapmaker program that'll map out a road track or cone course based on the Ginfo the Gtech records.

In the end, for the money it's worth it. For your final tune though, hit a dyno.

RC000E

If I can remember how to do screenshots I'd show you some stuff more familiar to Honda people versus the chevy's and all that crap that they have on the site. Also, I'll show you real world stuff, versus the pretty perfection the site shows.

I can't ever remember how to do a screenshot though....gonna go google.

rorik

that's really cool. I guess it's the ignition system rf interference the unit picks up for the rpm signal. I wonder if it works with coil packs..

RC000E

Yeah, it works on coilpack cars as well. Sometimes the calibration procedure is a little more complicated, but it works. I've had cars that it wouldn't pick up the rpm at all though. You lose the "versus rpms" points, but you can still see hp vs time, speed, etc.

So here's the breakdown...a little work for ya.

First off keep in mind, like I said you can't do a comparison between cars (hp/tq wise) unless your SURE the weights you enter are accurate. So, for any of the following, unless I show you a comparison in the same screen, I wouldn't consider it comparable. Now the acceleration times is time vs speed, so that's all certainly comparible between cars.

So, first off a JDM dual cam ZC in a EF hatch...just a hp pull. You would ignore any 1/4 mile info in the upper left due to the fact a hp pull is just that, a pull, not a launch with quick shifts. The hp pull is done differently....all you would find out in the directions with the unit.



Next is an EG hatch with a B20/GSR tranny combo doing a 1/4 run...keep in mind this is on the street, not a sticky drag strip. Look to the upper left for your times, then you can see the rpm vs time scale....this can show you your shift speed.



Here is a 2001 (or 2000...can't remember) Eclipse GT that I installed an N.O.S. kit on running a 60 shot. The comparison is the before and after results on the same piece of road, etc. The following screenshot is a hp vs time view. You can view the hp numbers this way if you do an acceleration run and not a dedicated hp pull. Also look off to the right and see acceleration times per 10mph.





Here is an example of a car with a TON of wheelspin. This was a car I tuned a while back. FWD DSM with an SB50 and 660's. Times reflect the lack of traction, but you can still view some info. The curves are very jagged, which is an indication of the loss of traction (i.e. loss of g pull, which the gtech uses to calculate hp/tq).



Here is a 00 EK I tuned with a Y8 and a 57 trim ebay turbo on 7psi



Here is a 95 Civic with a Z6/14b combo I tuned. Here I show the first pull on my basemap, with a pull after about thirty minutes of street tuning. This is pretty much after I leaned up/stabilized the fuel map, no real ignition tuning yet. REMINDER: You cannot take these NUMBERS as gold, just tune from the curves. This shows the curve difference, letting you see your tuning reflected in an actual curve.



Here are some braking runs my friend did to get the most from his setup. Just in the three runs you can see the improvement and feel he got from the numbers.



Finally, this is some skidpad stuff we did in a wet parking lot. It wasn't raining, but the ground was still wet from an earlier rain. This really requires playback to get the full effect, but you can see the comparison of the first versus second if you look at the curves. The screenshot is taken right as we spun out.



Hope that helps your decision man....it's a fun tool that isn't too expensive in my opinion.

EDIT: Just to be clear, I have the Gtech Pro RR, not the SS. The RR adds the PASS software and datalogging ability. Check all the differences on the Gtech site.




Modified by RC000E at 11:26 AM 9/20/2007

standbackimapro

i have a gtech pro rr,and the only difference between the RR and the ss is that the rr u can plug in with the serial cable

If you read the gtech site it shows all the sensors that it uses

but when u program it u put the cars dry weight in plus a passengr, it asks you to hold the car at different rpms and such..

RC000E

That is NOT the only difference between the RR and SS, I have news for you. The RR has a far larger memory capacity for datalogging, has many more features, and has a different graphical display versus the SS.