I've been selling gtech's for at least 9months now and everone says the same thing...the pro comp just rocks. The pro comp has a cleaner display, easier to read, more functions. The accelerometer in the pro-comp is much more advanced compared to the orginal, and there are 3 in the pro comp.
I haven't had 1 complaint about them and get nothing but praise in the emails from my customers.
HTH, sorry i couldn't tell you first hand experience...i haven't got around to getting one...but will soon
Unless you have an accurate car weight (w/driver) you won't get good readings. I've never been really happy with my orginal unit. The results are always way slower than it actually is. I've set the weight both under and over what it weighs and still get wacko results. According to the box my car runs like 12s 0-60 and 20+second 1/4 mile times. I know from actually track times its significantly faster than that. The new unit looks like a much better engineered box IMHO.
I have a G-Tech Pro (revised version of the first model). Anyways, a couple things come to mind:
1) Not very accurate for fwd or awd cars (on my unit anyways). Reason being I suspect is that for the G-Tech to start recording, the accelerometer has to start detecting acceleration. It does this by the accelerometer tilting inside the unit when G forces act on it. Now with a rwd car you will get quite a bit of weight transfer and thus pitch. So on my MKII, the G-Tech seems to almost kick in as soon as the hammer goes down (launching easier will give a delay though). On the other hand on my fwd Celica, or my freinds awd Talon, there seems to be a delay of several tenths (even upto 1 sec sometimes), as they don't seem to pitch as much due to their drivetrain layout. This discrepancy throws off the units accuracy, and accounts for the quicker times as some have related above.
2) The initial G-Tech also only has one internal accelerometer, therefore you have to "zero" the unit first before you can start using it. If this is not done properly, it will throw off the results. Although I have gotten good at doing this quickly, sometimes it seems like no amount of tilting the unit will "zero" the damn thing (probably has to due with the units friction hinge loosening or item #5 below). With multiple accelerometers, I would assume the newer G-Tech Competition model is alot more accurate (don't need to zero it), and might have that initial "time delay" thing solved for fwd and awd cars on the drag strip.
3) Accurate weight input is a must.
4) For the reasons mentioned above, the hp values cannot be deemed as gospel either. I tried different launching techniques with my MKII, and got different hp values each time. I would also get different hp values depending on wether I was shifting normally, or speed shifting. The engines hp doesn't change, but depending on how you drive you will get different hp values from the G-Tech (old one anyways, not sure about the newer one). Therefore I would only use the hp function as a method of doing "before and after" tests when installing performance components, and do it from a roll in one of the higher gears (so factors like clutch slip, and shifting "jolt" don't throw the unit off). This won't give you an accurate whp value mind you, but should give you a somewhat accurate hp "gain" or "loss".
5) I don't like the big suction cup used to hold the unit to the windshield. I'm sure the suction cup/s "flex" when the car is bouncing around while accelerating or cornering, which would also throw the results off.
6) Having said all this, it's still kind of a fun toy to have (as long as you don't get carried away with what the results say), and am curious to see how well the new unit works. My 2 cents worth.
And to add to that, some of the Durango owners I've talked to that have this unit also do their "runs" in both directions and average the numbers to get an averaged hp/torque reading. This clears up any error for incline of road and headwind.
Several runs in each direction should give you a good idea of what your vehicle is doing, but definitely not nearly as accurate as a true dyno run.
They are really good for initial tuning and checking new mods, as you don't have to pay for dyno time each time you turn a screw or add a new part, and really should be sold as such IMHO. For your fine tuning visit a dyno shop so all variables are eliminated, and get that extra 5+hp out of your vehicle...
Just my $.02!
with fluids, no driver, 5spd about 3080 for one with sunroof,
with fluids, no driver, 5spd about 3040 with no sunroof. Actual weight will change depending on how much gas is in your tank. Best bet is to find a trucker weigh scale in your area that is left on after hours and weigh it there
The reason why you all are getting different values is that accelerometers only measure acceleration in one direction. It has to be level to accurately measure your actual acceleration. Firm on the floor would be better than moving around on the seat (slight tilt) The amount your car pitches definately would affect it. It makes sense that it wouldn't vary as much on and awd. They dont pitch as much.
The best thing would be to mount it on one of those things they use on boats to keep the compass level. It would be pretty much spot on accurate then.
You can get them from Summit Racing or directly from www.gtechpro.com 139.99 new. I'd like to try out the newest one, the pro Competition. Picks up rpm and can graph power curves! You also don't have to move it to measure lateral G's, but so far I don't have $250 to blow on any neat gadgets lately