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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > GTech-Pro Install and RPM Calibration



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      08-16-2007, 12:04 AM   #1
roy@gambitmotorsport
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GTech-Pro Install and RPM Calibration

I just hooked up my GTech-Pro and am loving it!

I did a hardwire install using the included screw-in bracket, but on the dash trim with industrial-strength double-sided tape, since I didn't want to block my front view at all (pics below). Then I ran the chord down behind the glovebox and rigged something up to a fuse tap you can buy from Autozone which I read about on a radar detector hardwire install DIY here. I lost the functionality of the driver's cup holder, but hey, that's just for us Americans, right? It looks incredibly sweet with matching aluminum trim and red/orange backlights.

I had the typical RPM calibration issues folks talk about and went with manual map #18 as suggested on another thread here. This worked good for me, but only over a couple of thousand RPMs in 3rd gear. I found that once you got to this point, they stayed proper even if you backed off down into second gear sometimes. I figured something variable was up, rather than just super line conditioning by BMW, performed a couple of tests, and found it to be the "smart" A/C. You know, when you floor it, the A/C reduces (at least in low gear), I suppose to provide full strength to the engine. Well, this has the effect of leveling out the electrical system. When I turn off the A/C, even my revs out of gear are picked up well. Not that I'm going to be doing that soon with the 100 degree weather currently in SoCal, but it's good to know what the issue is and to put it to rest, so I thought I'd pass it on.

Can't wait to take a few runs up the local twisties and compare. I'm still at around 400 miles, so I'm not going for the best 0-60 runs right now, though I did once last night (unrecorded) when a guy in a G35 tried to race me; "tried" being the key word.
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      08-16-2007, 01:24 PM   #2
Vince@ V K Motorwerks
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I just bought some jumpers and hooked up my Gtech ss to the battery but I still cant get it to configure completely right. But I only messed with it about 2 times so far. Fun little gadget isnt it. The funny thing is I placed mine in the same location as yours.
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      08-17-2007, 04:14 AM   #3
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You can contact Tesla, but I am pretty sure that you can't have the display angled towards you when you make the run. Do you turn it straight forward when you make the runs?
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      08-17-2007, 04:18 AM   #4
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what do you have to connect the gtech to in order for it to function properly? not talking about hardwiring though....
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      08-17-2007, 04:27 AM   #5
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Quote:
Originally Posted by that guy nico View Post
what do you have to connect the gtech to in order for it to function properly? not talking about hardwiring though....
You mean to be able to measure rpm? I would like to know that well..
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      08-17-2007, 12:52 PM   #6
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Quote:
Originally Posted by hotrod182 View Post
You can contact Tesla, but I am pretty sure that you can't have the display angled towards you when you make the run. Do you turn it straight forward when you make the runs?
Not to disagree, but I'm almost positive it can be angled in any direction. The thought did cross my mind, too. But, the manual (which I read in its entirety) doesn't state this and there is an "orientation" phase you take it through, which is simply a first-time straight-line drag run, so it can gather which direction is forward.

Accelerometers with the proper driver software could definitely handle the task. At a physical level, I believe they pick up changes in direction the same way throughout 3D space. Going off on a total tangent, if anyone's interested, many laptops have an accelerometer built-in nowadays. If it senses a quick change in direction, it "parks" the hard drive, to protect from head crashes in the event it has been dropped and is about to be jarred hard.
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      08-17-2007, 01:04 PM   #7
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Quote:
Originally Posted by that guy nico View Post
what do you have to connect the gtech to in order for it to function properly? not talking about hardwiring though....
It just needs power. It picks up G forces (acceleration, braking, turning) directly with its accelerometer. It deduces speed based on changes in G forces. It calculates HP/Tq based on these and the vehicle weight you enter. It does its best to "sense" the RPMs by power fluctuations in the vehicle's electrical system. My findings are that the variable-rate air conditioning makes the RPM pick-up extremely hard for it at low revs. But, thanks to _ulises 335i_ here, manually selecting RPM map 18 matches things up well.
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      08-17-2007, 01:23 PM   #8
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Is that a suction cup mount? I actually have a GPS that I'd like to mount in that location, but the suction cup doesn't work on the aluminum trim...
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      08-17-2007, 02:43 PM   #9
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Quote:
Originally Posted by roy@gambitmotorsport View Post
Not to disagree, but I'm almost positive it can be angled in any direction. The thought did cross my mind, too. But, the manual (which I read in its entirety) doesn't state this and there is an "orientation" phase you take it through, which is simply a first-time straight-line drag run, so it can gather which direction is forward.

Accelerometers with the proper driver software could definitely handle the task. At a physical level, I believe they pick up changes in direction the same way throughout 3D space. Going off on a total tangent, if anyone's interested, many laptops have an accelerometer built-in nowadays. If it senses a quick change in direction, it "parks" the hard drive, to protect from head crashes in the event it has been dropped and is about to be jarred hard.
I think it needs to be straight too because I'm not sure if the g-tech has that capacity. But what you can do is try it angled and try it straight and see if the numbers are significantly different.
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      08-17-2007, 04:09 PM   #10
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Quote:
Originally Posted by nj335i View Post
Is that a suction cup mount? I actually have a GPS that I'd like to mount in that location, but the suction cup doesn't work on the aluminum trim...
The GTech comes with a suction cup mount and a permanent screw-in mount. After deciding that I'll probably never really want to take it off, I used the screw-in mount, but with industrial strength two-sided tape instead of screws. If your suction cup is shallow enough, I imagine you could use the tape, too.
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      08-17-2007, 04:33 PM   #11
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Quote:
Originally Posted by hunter399 View Post
I think it needs to be straight too because I'm not sure if the g-tech has that capacity. But what you can do is try it angled and try it straight and see if the numbers are significantly different.
I've sent the manufacturer an email about it and will let you guys know what they come back with. They sometimes take a while... However, I think if the angle was important it would be mentioned repeatedly throughout the docs (which are quite extensive) and I found no word of it, although there are tons of cautions for all other sorts of things.

After a run up the Angeles Crest today, I can say that my left and right cornering Gs are near identical, although that's not proof and forward acceleration could be handled differently. If I'm right, I guess there will be one bummed Ford F150 Lightning owner out there.

http://www.f150online.com/forums/showthread.php?t=28437
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