dragonAMG

Does anyone have experience with the new GTech Pro? How accurate are these devices?

BMWEATR

No. not accurate they suck.

Trevor

I've heard great things about the new ones. The ET is practically spot on (<0.04 off). The trap speed is still high compared to the track but its much closer than the old ones were.

The dyno function is a VERY handy for tuning. I've seen guys get their tunes spot on without even strapping down to a dyno.

45acp

my co-workers have used it (the SS) down the 1/4 and it was about a tenth and about 1.5 mph off thier timeslips (3 runs total). not bad. but the trick is you HAVE to calibrate it correctly-set your rpm's, the weight of the car, the pitch angle (this gets confusing) and redline. once you do that, they are not bad if you don't have any tracks nearby. you want to dead hook as much as possible, once wheelspin occurs it will be off by some.

my w210 55 ran a 13.6 @ 107 on an SS model w/the ESP on. not bad, but i'll be taking it to englishtown for real times.

dragonAMG

I'm going to try out the SS. Checkout their video... looks pretty sweet - http://www.gtechpro.com/test.html

Grumpy666

This is the key for accuracy with these units. Best results are obtained when they are mounted as parallel as possible to the ground.


Wheelspin should not affect the results. These units are based on accelerometers - wheelspin will be detected as reduced acceleration, which will be reflected in the final numbers.

FlyByNight

Grumpy, as we've established I'm an idiot, you'll have to forgive me for not understanding this at all: Wheelspin should not affect the results... but it will be detected as reduced acceleration, which will be reflected in the final numbers...????

If wheelspin = reduced acceleration = reflected in final numbers... how is it that wheelspin will not affect the results?

Well, whatever the explaination, I can tell you wheelspin DRAMATICALLY affects the results on the RR. If I spin the tires past the 12" rollout area, all my numbers drop like anchors thrown out of air balloons. I fiddled with the launches many times. Even the hesitation of traction control going on and off affects the HP / torque figures, as well as times.

"Vehicle pitch / wheelspin / wheelhop / etc: The Gtech cannot
make accurate measurements if the vehicle is incapable of
accelerating smoothly down a straight line"

There are many faqs on their site regarding launches and the importance of no wheelspin or hop... read away at gtechforums.com.

I have the Pro RR, and if nothing else its fun. My K2 regularly gets low 4s 0-60, and I've yet to do a 1/4 anywhere. I got a 3.86 zero to 60 with my best launch (traction control on, slow start, no wheelspin, floored it after .5 seconds, sport tranny, comfort suspension)

The HP / torque measurements are really odd... its not crank hp, not wheel hp, but net horsepower. The only real world benefit is that you can check this HP rating before and after mods for differences... but the figure will be miserably low compared to what you're used to. In other words, you can only compare it to itself, as there's no other dyno measurement that will be comparable other than its own readings. Its very virtual. Here's an example...

• First of all, there is a variance as to the horsepower ratings within a
set of engines from the factory. Your engine may have been
delivered at 310 HP instead of 320 HP
• This 310 HP figure would be as measured in a lab, out of the
vehicle, with no major accessories attached, and perhaps a very low
impedance exhaust (if any exhaust at all.) You can lose about 10%
with the engine actually in the car: 310 * 0.90 = 295 HP left over
• The gearbox may sap a few percent: 295*0.98 = 288 HP left over
• The driveshaft may sap a few percent: 288 * 0.98 = 282 HP left
over
• The differential may sap 4 percent: 282 * 0.96 = 271 HP left over
(this would be higher in an AWD vehicle)
• At 65 mph or more, we may lose another 30 or 40 HP to rolling
resistance and aerodynamic drag, which drops us into the 230 HP
territory
This 230 HP value is the net HP which is left to accelerate the vehicle after all
losses have been accounted for.

I can't remember what mine came out at, but it was around 400 "net" horsepower, with variances in the 300s and 400s (390-440) depending on your run. Its the largest FAQ on their site (why my HP is so low).

Its a fun toy, though. I'm convinced the HP / torque portion is less valuable than the ETs... they seem very accurate... I've had many 1.8 60 foots, and some 2.0 pluses when I had wheel spin. Results are repeatable with impressive accuracy. I'm dying to try a 1/4 mile run. Damn LA, such a long drive just to run a 1/4 miles somewhere.

Note: You don't need to calibrate these things, really. Since August of 03 they've been factory calibrated. All you do is mount it as level / parallel as possible as Grumpy noted... and they include a very versatile mount for doing just that. Then you do a quick et where you go from 0-5mph once, then stop. Bingo, its automatically calibrated.

Hooking it up the first time is easy as pie... car weight (include driver weight) then go through the rpm set up... it works fine on our E55s....



Loren

Grumpy666

My bad. What I was unsuccessfully trying to say:

Wheelspin should not affect the accuracy.

I have owned a G-Tech unit since 1997, so I am intimate with its performance capabilities.

FlyByNight

no worries... simple misunderstanding easily cleared up...



Loren