wolverine

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I'm just starting to really appreciate what this amazing device can do. With the proper calibration, I think you can get some very accurate acceleration readings. I've been experimenting with the 'pitch factor', and I think I've found an ideal way to calibrate it. Just wondering if there are other members who would like to share data and tips?

This product is great for evaluating mods, driving techniques, and if you're a gearhead, it's just fun to play around with. Here's a set of quarter mile runs I did (on a deserted stretch of road):



Anyone else running Gtech Pro RR with your M5??

0700700

great 0-60mph times... now do some 0-62.5mph for us europeans

w8pmc

Nice results & perhaps i need to invest in one of those.

What's the cost? where can i get one from? are they easy to set-up/install etc?.

wolverine

I can't remember exactly, but I think around $300 - just check out their website. I have the RR, which is the top line model - I would highly recommend this product if you are experimenting with mods and techniques.

Setup is simple, but calibration takes some time, as I've said in other posts. I think this is a superb device for comparing mods, different octane gas, different shift times, and especially the best launch method. The repeatability is excellent, I'm not convinced of the absolute accuracy in terms of time and speed. With proper calibration of the 'pitch factor', I think the speed and time accuracy can be quite good though.

tachyon

What tips do you have to calibrate the pitch factor? I'm curious about how to set it up for my 550i.

wolverine

Speeds at redline in gears for the M5 are 44mph 1st gear, 66mph second gear, 97 mph third gear. I'm not sure what they are for the 550, but you should be able to find out pretty easily. Do a few runs where you shift right at redline, and use the Speed vs time Gtech graph to measure the speeds that the shifts take place (if you've shifted right, they should be very close to redline). I then set the pitch factor so that the highest speeds in 1st, 2nd and 3rd gear are as close as possible to 44, 66, and 97 mph respectively. If you are driving an auto, then try to note exactly what rpm the shifts take place, and calculate the theoretical speed from the ratios.

The idea is that if your tire rolling diameter is within a percent or so, then the tach and gear ratios should be pretty much dead-on, and your true speed at redline should be pretty darn close to the maximum theoretical speeds in each gear. If you set the pitch factor so that your gtech indicated speeds match the theoretical speeds at redline, you should be pretty close to measuring actual speed. The best way to calibrate the pitch factor is to use your trapspeed at a dragstrip, and compare it to your indicated speed. I think this is the next best way to do it.

znod

He can switch his display to metric and get all the metric results you want--even more when his data are downloaded to Pro RR documents.

znod

The pitch factor makes very little difference provided one is in the ballpark. If you have the sport package, then I'd use 1.9--which is what I use. grogan545 uses 2.0 because he dosn't have the package. We are using 1.9/2.0 because Escort had good results with a slightly higher setting for a roughly comparable, but somewhat softer suspended, Audi.

How is the testing going? Do you have any results yet? I forget; which meter did you buy? Let me know if I can help. Just post on the 5er discussion, and I'll reply.

znod

I think you have a clever idea--trying to get accurate MPH readings from your car and then calibrating the Pro RR accordingly. I have been trying to think of a way to make things work hopefully a little better along the lines you are thinking. Consider the possibility of:

(1) measuring an actual 1/4 on your "strip" (possibly using the knowledge that at 60 MPH you will cover 1/4 mile in 15 secs and having someone else start a timer when you signal the beginning of the 1/4 with you noting the end of the 1/4 when 15 secs is signalled by your aider and abettor );
(2) making, say, 5 or more passes and noting your 1/4 terminal velocity via your corrected "analog" speedo values (see below) on all of them as best you can--but particularly on the ones where you get the kind of start, etc., that you think is "optimal;"
(3) using your average terminal velocity on your "optimal" runs as your "true" 1/4 mile speed; and
(4) calibrating your Pro RR to yield the average terminal velocity at what it "thinks" is the end of the 1/4 (which, of course, may differ from the end of the actual 1/4 slightly--use the Pro RR distance indicator function to see how well your two 1/4 indicators agree--physical versus Pro RR).

Then, perhaps, your Pro RR ET's would be pretty accurate at least on the passes where you get what you consider to be a good start. Note that you will need to get into the Pro RR downloadable data to find your actual end of 1/4 Pro RR teminal velocities since the 1/4 speed given by the Pro RR is trap speed. Also, if you can get to your "true" speedo on the M5, as we can do on the 545i/550i, etc., then you can compensate for your "analog" speedo error in determining your average terminal velocity. In general, you would want to use your corrected "analog" speedo values for all determinations of terminal velocities for your passes because the true speedo, at least on my car, is so hard to read.