Racelogic's PERFORMANCE BOX vs G-TECH PRO RR

[A80Avant]

Im thinking of purchasing one of this gadgets...They seem to have the same potential and do almost identical calculations such as 0-60 0-100, quarter mile etc as well as power measurements.
Their true difference is the way they calculate this.The performance box uses a sensitive GPS sensor whille the G-tech an accelometer and g-meter.

Im not interested in dynoeing the car anymore as itself does not take into account all factors in power production and on the other hand,different dynos,give different measurements and sometimes no reference can be found in between them.

The only difference between the 2 gadgets is the price.
performance box:560euro
g-tech pro rr:360euro

i would like to know if anyone has any experience with these and if the first justifies the 200euro more in payment.

cheers
Vasilis

[Error404]

I used to have a G-Tech Pro, but an earlier version. The times and power calculations were pretty accurate, about what I expected.
I would suggest just based on the actual workings of the devices the G-meter based system will be more accurate simply because it is not relying on any external input... GPS can only be as accurate as the information it receives, and the frequency with which it receives it.

[EspenW]

This article could probably be of help:

http://www.caranddriver.com/article.asp?section_id=4&article_id=9380

You can get the G-Tech Pro RR for approx. 170 Euro on Ebay.

I have a unit called Mr. Dyno. Similar features to the G-Tech Pro RR, but it has two very helpful additional features: you input temperature, elevation, barometric pressure, etc, and it will correct the horsepower to the SAE 1349 standard. Without correcting the numbers, you can't compare results made on days with different temps, etc. For example, on a 3 deg C day I tested at 335hp at the wheels corrected to SAE 1349. Uncorrected (as would show up on a G-Tech) was 355hp. This way I can compare runs made in the winter to runs made in the summer.
Also, it has an input for aerodynamic drag, so it corrects for power lost to wind resistance (easy calculation based on frontal area and Cd of the car).
I don't bother with dynos either, the results are not consistent between different types. Turbo Magazine tested the same car on a number of dynos, and got results ranging from 228hp to 265hp. Worthless numbers and a waste of money.

http://www.turbomagazine.com/tech/0306tur_turbo_magazine_dyno_dash/index.html

http://www.turbomagazine.com/tech/0402tur_dyno_tricks_problems/index.html

This is the power produced at the wheels, which is actually measured, and should be pretty much dead consistent between the brands. It gets even worse when they start guessing flywheel power, as is common in Europe.

With the Mr. Dyno, I always test from the same spot on the same road, and get perfectly overlaying graphs from back to back runs. Makes it easy to evaluate adjustments to such as igntion timing and cam timing, and evaluate mods.

[A80Avant]

MR dyno is a third option then?
only thing about the GPS signal that racelogic box is that it is very very accurate as done laps in the nurburgring and silverstone,it pinpointed the whole route even the way the corners where taken.
true what you say about the signal though,it is an external source nonetheless

[dest]

While I agree with what you say about using different rollers and getting different figures... there is nothing wrong with using the same one every time so atleast there is some degree of relativity in the results!
Also, unless you are checking the fueling is correct then I see no point in running a car anyway, therefore you only really need to run it on rollers after making or adding modifications to see their gains/losses.
Remember the quality of the rollers, and the operators experience also play a part in it too!
The ones I used regularly (my old car was used for technical features in a magazine and had ALOT of runs with various mods) was always consistent.
Eg, if back to back testing over-ran our time, we would continue another day, taking a final run and then comparing it to the first run on the next session, the figures were never more than 3 or 4bhp different

[A80Avant]

i read that article.It seems that the older AX22 was the ost accurate at the time although it relied more to the GPS rather than the accelometer.
On the other hand,if the GPS signal is used,is it really needed a temperature input?If the car performs less in the summer it will show up on the speed and distance covered,which will be less,if there is ignition retardation,therefore will produce less hp figures.right?

[A80Avant]

dest,i agree in using one roller all the time.The problem is that even that roller by the time it is fully adjustable,you can get different results depending on the owner experience and attitude!Here in Greece everyone is keen on becoming the most 'strict' dyno in the world and program their rollers to produce lower results so that you are not satisfied with the results.On the other hands,those that are programmers themselves make it look as the car they programmed produces better results! how convenient!!

Finally im more keen on seeing what the car does on road condition rather unplugging the tyres to fit hub dynos,or use roller drums that have lots of different ways to tamper with while on everydyno i know everyone says that either the air supply to the front is NEVER the same as in real time experience travelling at 200kms per hour and also there is no air drag at all.
I dunno,the way i see it,this way i can perfom a modification and see the result right there,if there is any or not.

[EspenW]

The Mr. Dyno is no longer available, unfortunately, only option would be to find one on Ebay, etc.
I would be tempted by the Race Logic too. Having the GPS input is very nice indeed, as it cancels out factors such as vehicle squat and road grade

[EspenW]

i read that article.It seems that the older AX22 was the ost accurate at the time although it relied more to the GPS rather than the accelometer.
On the other hand,if the GPS signal is used,is it really needed a temperature input?If the car performs less in the summer it will show up on the speed and distance covered,which will be less,if there is ignition retardation,therefore will produce less hp figures.right?

Temp/pressure,elevation, etc. input is only used for horsepower measurements.
Cold air produces more power, since it is more dense, and a cooler charge allows more igntion timing and boost before knock occurs. A test run in the summer might yield 320hp, while the same engine would yield 350hp on a cold winter day. That is why results must me corrected to SAE or DIN standards.
What makes the matter more confusing is that these correction factors mostly apply to naturally aspirated engines. A waste gate controlled turbocharged engine will make up for about half of the power loss due to altitude (and days with low barometric pressure).

[A80Avant]

but what is the point of corrections?i want to see how much actually the car produces in the summer and winter

[EspenW]

but what is the point of corrections?i want to see how much actually the car produces in the summer and winter

The point of the corrections is to make the numbers that you generate on different days/time of the year comparable.
Say that you get 350hp on a 10 degree day in the spring, then the car spends two weeks in the garage while you install a bigger turbo, intercooler, whatever.
Then you go out a re-test on a day with 25degs outside, and you still generate 350hp.
If the numbers aren't corrected, it will seem that you did not make any gains, but you did, since 350hp now was generated under less favorable conditions.

There is approx 10% less power generated on a 30 deg summer day vs. a 0 degree day in the winter.

[A80Avant]

that is true.i didnt think of it that way...

[gtiteen]

I think the question here is what you want it for.

If you are performing mods over a long time and wish to track the increase in power you need the one with which you can input corrections.

If you just want to see what power your car puts out at a specific time, summer or winter, the one without corrections will do.

I didnt realise these were this cheap, if i get round to getting a car i might buy one asi didnt know that rolling roads were so inaccurate.

[A80Avant]

well,truth is that the corrections do have a point,but i have heard the G-tech is not that good for power figures,as the GPS unit is...I dont know...

[EspenW]

well,truth is that the corrections do have a point,but i have heard the G-tech is not that good for power figures,as the GPS unit is...I dont know...

The GPS units definitely have their advantages. However, repeatability is the main concern here, and the G-tech should do that quite well.
Note: there are online calculators for finding corrected power, for example this one:

http://www.csgnetwork.com/relhumhpcalc.html

Plugging the test conditions into this will give you corrected power for that day.
However, the advantage with the units that calculate this internally is that you can overlay graphs.