I've noticed an approx 15% HP discrepancy in the new GTECH Competition Pro vs the older GTECH pro unit. I own both the new one and old one, and in fact even went out and got another GTECH competition Pro just to make sure I wasn't stuck with a faulty unit. Dozens of calibrations, firmware updates, and road tests had me convinced that the new gtech pro HP readings were way way off from real life dyno numbers. I know, because I've spent lots of hours and $$$ tuning on several different dynos.
I called tech support at the GTECH company, and eventually worked my way up to one of the vice presidents there. We went into indepth discussion on this issue, and they're looking into it further. Still waiting to hear back from them.
Has anybody else had similar experience? When I compared the old Gtech vs the NEW Gtech side by side in the same car at the same time, the new one ALWAYS read about 15% lower HP than the old one, while the old Gtech was always DEAD on with actual dyno readings to within a few HP. Ie/ on a stock MCS, the old gtech pro will read around 135-140RWHP, which is dead on to the actual factory rated 138RWHP. On the other hand, the new Gtech competition Pro will always read way lower in the range of 115-120RWHP.
The tests were performed over a course of a couple weeks, with multiple calibrations to ensure it wasn't due to this. In fact, I even got another brand new Gtech competition pro, and still got the same results.
i don't have a lot of confidence in mine either. the G measures time and acceleration and then does a calculation for HP and using the weight you input and velocity. my discrepancies have been with track times for the 1/4 vs the g times. 15% is about 2 seconds in the 1/4, but I havenn's seen it that far off, more like 1/2 second. mine even recorded 125mph in the 1/4 once, but i got no trophy for that one.
So for with mine its been about Dead on. I also have bother versions the old and new pro. After a few runs with current set up the G-Tech pro said that i could do 14.7 and had a HP rating of 156whp. At the last Drag run i did. I ran a 15.1 never leaving out of 3rd which topped out way before the 1000 ft mark and did a dyno run there which said i pulled 153 whp.
For the races to try and keep a consistant time. I would take off in 1st. at 3k. and just before redline shift to 3rd and let it run to the limiter which was giving me constant 15.5's
02 MCS DS/W (Totaled November 02 on Fall Folage Run)
03 MCS DS/W (See my MINI Profie for extensive list of mods)
Wow...mugami, you get consistent readings with your Gtech Competition Pro and the Dyno?
My old Gtech Pro and the dyno are dead consistent. I've tested them time and time again over multiple runs, and the Gtech Pro is dead on with HP measurements. However, the Gtech Competition Pro is a different story...always 15% off. I'm not sure what the problem is, but I got the exact same results with other Gtech Comp Pros tested in MANY different vehicles, so I believe this would be the same with ALL Gtech Competition Pro units.
I'm surprised to hear that your Gtech Comp Pro is giving you consistent readings though. How many HP runs have you performed, and have you ever tried doing HP runs with both the old and new Gtech mounted in the car at the same time? I'd be very interested to hear about your results!!
Not only are the trap speeds way off with G-Tech's formulas, but the company outright lies about the cause of that innacuracy:
Even with a 95 mph trap speed where I stayed on it til 100+ mph, the 60-ft beam only saw about a 1.2 mph change in my speed. Also, if G-Tech knows this, why don't they just average their speed between 1260 ft and 1320 ft? It should be simple enough to do by changing their integration method.
I've used G-Tech's and AP-22's in other vehicles and found them to be little more than toys. Logging average rear-wheel speeds using the car's ABS sensors has proved to be EXTREMELY accurate (with 0.05 seconds AND within 0.1 mph) when used at the dragstrip.
wont aruge with what Andy said about the top speed cause it is a bit off.. the Test i run are 5 runs at a local closed down airport runway. and take the avg. of the 5 for stating times. One thing i did notice even though they say its self leveling. Its not. Take the time to level the machine just before the run Even if the bar is showing just a little on the right side it can throw the readings off. After makeing a run at the 14.7 i bump the machine a little for the next run as to where it has some black bar showing on the right hand side. on that run i did (according to G-Tech) 14.0 then after releveling it was back down to 14.7's . The 5 good runs that day were 14.69 14.72, 14.68,14.71, and 14.74
I just download there software so i can play with it on this machine. if i get it to work ill post a run or two with the G-tech comp pro.
Also dont know if it really make a diff.. but i also tried setting the rpms by driving the car to the 2k and 5k spots instead of just reving in the parking lot. With that way of setting it.. i was able to get the 15.5 for the 1/4 in stock trim. which was right inline with what C/D and many others mags.. said the car would do stock.
02 MCS DS/W (Totaled November 02 on Fall Folage Run)
03 MCS DS/W (See my MINI Profie for extensive list of mods)
Why would RPM have any effect on the 1/4 mile ET calculation? Their calculation is pretty simple:
Acceleration is measured by the sensor(s) in g's. 1 g = 9.81 m/s^2. They are sampling, say, every 0.1 s. By multiplying the acceleration times the the time slice, you get the speed. By multiplying the speed times the time slice, you get the distance travelled. Add up each of the distances you travelled until you get to 1/4 mile (about 403 meters). For both the ET and trap speed, the only two variables needed are time and acceleration. The vehicle weight, rpm, etc. are only needed for their dubious "horsepower" calculation. The problem with their horsepower calculation is, in their own words:
This, like their trap speed measurement, isn't comparable to any of the standardized methods of measuring horsepower. What they are failing to do, is measure the power absorbed by the road, air, tires, etc. By leaving this out, they are missing a large component of horsepower. Here's more information on a better and more accurate way to do it:
Andy since part of the question is abaout HP readings as well as the ET. After checking a few of the runs that didnt seem right on the G-Tech.. i noticed that the first 2k wasnt being read by the G-Tech and on the good run it was. for this point setting the thing correctly does matter. Its possible since it has to set where the max is by it sampling if it read 0 rpms during the run the error may cause the rest to be off. Since i dont know the programming itself i cant say if what i stated is true or not. This is your area of expertise not mine. Therefore im just making observation of what i found during the runs. Im not saying its the greatest toy there is or that its dead on all the time. Not everyone is lucky enough to have a truely flat 1/4 to run on for testing the darn thing. Any tilt up or down will mess with the readings. Since when i run i do them by the Numbers as in shift points and take offs and rpm at 1/4 mark. I use this to check on the G-tech. When those reading where withing 200 + / - of my marks i would beleive it a bit.. but at same time when there were as much at 1.5k off the time and other reading would also be off.
Some of the off reading could also be from how drastic the Heartbeat during the shifting as well as how soft the suspension is since the car will tilt back more with a softer suspension than a stiff one. As you stated there are alot of varibles not included in the readings. After lowering mine with sticker tires than stock the times slowed according to G-Tech even throu the RPM at the end of the 1/4 were higher so the car itself was going faster.
Hope this helps answer some of the question for what i was stating. I have the Ut most respect for both Andy and JLM, They are tops in there fields and truely know what there talking about. For me im just a grassroots redneck who reports what he sees and not afraid to admit when hes wrong.. Which seems to be alot.
02 MCS DS/W (Totaled November 02 on Fall Folage Run)
03 MCS DS/W (See my MINI Profie for extensive list of mods)
Mugami, I hope I didn't come across as critical of you, I just wanted to clarify some info about how the G-Tech works. You make some excellent points about the road conditions, this can affect accuracy A LOT.
Are you planning to run at E-Town on Friday? I'm kicking myself for not showing up last Friday (I really thought it would rain!).
I'm just wondering if you, or anyone else on this board, has had a chance to run the GTECH competition Pro at the same time as the older GTECH Pro, and compare the HP readings side by side.
My findings, and that of others seems to indicate an approx 15% discrepancy between the newer and older models, with the old units being very close to what you'd get on a real dyno. Obviously, I wasn't too happy about this, since you'd expect the newer GTECH to be more ACCURATE than the old one, and in many ways it is. The tech gurus at GTECH are working on figuring this one out, and I'll update you guys with the results. The only speculation at this point, is that the older GTECH Pro unit may have had some fudge factors in the alogrithms to compensate for the aerodynamic losses, which represents the most significant loss. Whatever it was, the older GTECH worked like a charm, always within a few HP of my dyno runs, over and over again.
It is not possible for either the new or old G-Tech to calculate horsepower (at least the kind of horsepower that can be compared with dyno figures) accurately since neither uses a coast-down as part of their procedure.
apexi yes i have run both side by side the main part between the two i could tell from last night is back to the shifting and leveling of both. The old G-tech would give the same reading even if it was off being lvl but the new one wouldnt. Also shifts did make a difference as well .. the smoother pwr shifts i made the closer the two became. On the first couple of runs (looking at G's at shifts) the first shift would be about 1inch heartbeat and the others about 1/2 inch heart beat. would give about a 10-12% difference between the two. These shifts were at about 6.5k standard style of lift foot off gas whilep pressing clutch shifting then releasing clutch while flooring it. Later i used true pwr shift technique the Heartbeats were 1/4 for 1st to 2nd and rest was 1/8 or less which put the two G-tech with in 1-5% of each other. In this technique the thottle never leaves the floor. pressure is left on the shifter while engaging clutch so its moving as soon as enough pressure is let off (normally about 1/4 way down the clutch) at this time the foot slips off the side of the clutch. Which allows the shift to happen without hitting the rev limiter even at 7k shifts if done right.
Since i dont know the sampling rate and sensitivity between the two but if the old one is slower and or not as sesitive to this particular change then it would make sense. why the two are off.
Andy E town is a 4-5 hour drive for me.. when i went to Helix to get the pulley changed.. it was 3hr 49min to get there.. and 8 hrs to get back.. i hit the washington traffic on the way back. Im keeping an eye on the "I did a little drag racing last night" thread. If i get the wild hair up you know where and you guys are planning on racing that night i may just pay you guys and unexpected visit. I'd love to see Minime's and the other guys 13's. As well as go do a run at the strip with the temp on the tack isnt in the Mid 90's
02 MCS DS/W (Totaled November 02 on Fall Folage Run)
03 MCS DS/W (See my MINI Profie for extensive list of mods)
I have a GTech/Pro and can't comment on the accuracy compared with a dyno. However, I would be very surprised if it matched the dyno as the GTech does not take into account the power needed to overcome air resistance. I get readings that are typically 30hp less than I others are getting on the dyno and consider this reasonable - I usually run the tests in 2nd gear and max hp comes close to 60mph. 30hp is about right for the power needed to push the car through the air at that speed.
I consider the GTech to be a great tool for comparing before and after results from mods but it will never give absolute power numbers accurately.
2007 DS/W MCS LSD, sport suspension, Enkei RPM2 wheels
2002 EB/W MCS Sport package, Rogue intake, Borla exhaust, 15% pulley & Madness sway bar
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