BOXMAN

I also have a Gtech pro. These are my results.
Info you should know

Car 05 Tc 5spd
Mods: 2 1/4 cat-back custom into a 4 inch free flowing muffler/ and K&N drop in filter
car has 2200 miles on it and the temp was 72F
weight entered 3300 due to friends
I also live at 5900 ft above sea level.

I acchived an average HP reading of 125. If i was to calculate that to 0 ft above sea or what SAE is i am looking at around 145-150 range. Not bad for just my own exhaust and a drop in. I will keep you updated when my Injen cold air arives on friday and then next friday its AW header and CC S pipe.

matty-tC

then why is the G-tech about 20hp off? I've seen auto's dyno at 130-140whp with similar mods.

BOXMAN

I think this kids Gtech might be off cause as you can see my results are way closer to a roller dyno

Thrawn

Matty, you seem to be missing the point.

1) The Gtech's numbers are affected by far more factors than a chassis dyno, as was described in detail earlier. Factors that cannot be corrected for by the unit w/o it knowing some really detailed info such as ambient temp, wind speed, drag coef. of the car, road conditions, and so on. Just as there are factors a dyno cannot correct for such as exact gearing info, exact losses through the transmission, data on the flywheel, rims, tires, and so on. All of which result in lower numbers then what is measured by the manufacture at the crank. The more factors that cannot be corrected for by the unit, Gtech, dyno or otherwise, the lower the numbers will be. However, that does not diminish the effectiveness and usefulness of them, but more on that later.

2) Just like a chassis dyno, it was not made to accurately measure absolute power. Just like a dyno, it cannot accurately measure absolute power, they both make guesses based on pre-set calculations and formulas.

By absolute powerI mean power that the engine is actually making before any drive train losses, before losses due to rims/tires, before any losses due to bad roads, or any losses due to drag. The point of the Gtech, just like a dyno, is not to say "Ok, I'm making xxx hp." You'll never get true results on a chassis dyno or a Gtech. For example, take your car to a Mustang brand dyno, do several pulls, stabilizing the inlet and coolant air temperatures in-between each run. Now, take it over to a Dynojet brand dyno, on the same day, nearly the same time, and your results will be different. Results will very from dyno to dyno due to various reasons including how they interface with the vehicle. A perfect example is a dyno that straps right to the wheel hub (Dyno A), and a dyno that has rollers that get moved by the tires (Dyno B). Dyno B's HP and Torque estimations are affected by the weight and diameter of the wheel's, tires, calipers (weight), and disc/drums on the car, while Dyno A's estimations are not. This will result in quite different results even when using the same smoothing factor and SAE correction. The Gtech goes a step further, and it's calculations are effected by even more factors that have an impact on performance.

Back to point 2, neither Gtech's nor chassis dyno should, or can reliably, be used for measuring true power. What they are good at, is for measuring changes in power to find the affect of a modification. If care is taken by the operator to standardize as many factors as possible, for dynos and Gtech like products, then the difference in results can be an accurate way of measuring relative changes in HP. Whether a Gtech or dyno says I start at 150 or 75, I dont care. I care about the difference between where I started and where I finished. If a Gtech says the mod I added took me from 75hp to 100, and a chassis dyno says I went from 150 to 165, I could care less about the starting and ending numbers, I just care about the fact that I made 15hp with the mod. Although, measuring increases/losses in percentages would probably be more accurate especially if comparing results from a dyno to a Gtech.

On a side note, I wouldn't want to tune on a Gtech, I'll keep that on the dynos.

matty-tC

So with all that text you just put there, you just basically proved its worthless at calculating power and it's a very expensive, fancy, stopwatch.

Thrawn

I guess you still don’t get it. By your logic then, chassis dynos are equally worthless, since, as I described in great detail above, there are several factors preventing them from calculating true power. But, as I said, anyone that's using a dyno or Gtech for what they're good at wont care, they care about how they measure changes in power.

BOXMAN

Or how about the fact Car And Driver used to test with them??!!!!

Dr_Isotope

iTrader: (1)

Okay matty, there's a point when skepticism just becomes ordinary denial. Chassis dynos are only accurate at measuring gains or losses from a baseline. The numbers they provide do nothingt indicate the actual power the engine is producing, only the changes from point A to B to C.

And the GTech is similar in many aspects. But the GTech can provide a more "real world" picture-- it uses basic math: if the car takes X seconds to get to 60mph, and weighs X amount of pounds, the unit can extrapolate how much force was required to move that mass to that speed in that time. That's essentially all a chassis dyno does; is figure out how much force is required to get the rollers moving at X speed in X amount of time.

The GTech has been proven accurate time and again-- to within less than a tenth in the quarter mile. So until you can make a run down the lanes and then guess your ET within a tenth, the GTech will continue to be more accurate than you are. The K&N CAI showed an increase in 0-60 time, with a reasonably accurate real-world indication of increased power numbers at the top. It happens. Welcome to reality.

matty-tC

so you're saying, that the G-tech shows we lose 50hp between the crank and the wheels?

tell me exactly what it is the G-tech does so well?

Dr_Isotope

iTrader: (1)

You're still not getting it. Whether the stated HP number is 100 or 1000, the only thing that matters is how long it takes you to go from 0-60, or the starting line to the finish line.

Discount his power numbers all you want-- it doesn't matter. The car got slower, and you could have proven that with a GTech, a stopwatch, a radar gun... hell, with two white lines painted on the ground and some simple math.

K&N typhoon on unmodded auto tC = slower than unmodded auto tC with OEM airbox



So what's the argument?

matty-tC

So you're sayings the hp measurement is just useless (based on your facts) and that it functioned as a stop watch?

matty-tC

My original argument was that the G-tech is horribly inaccurate. There is NO WAY that we have 35% drivetrain loss as the G-tech says.

You chimed in with that it's just as accurate as a dynamometer.... ehh.. you have an argument there but it's nowhere near what others have shown on true dynomometers

Dr_Isotope

iTrader: (1)

No, you're saying they're useless, I'm saying they don't matter. The real-world gains shown by adding the Typhoon are in-line with K&Ns generous estimations. The losses in acceleration are to be expected. The CAI moves the powerband around-- more power up past 4k RPM, as much as 20% less power from idle to 3k.

A chassis dyno gets its numbers from the "perfect" spot in the graph-- no load, minimal trans losses, WOT. The car, in the real world, has to overcome drag, friction with the road, drivetrain losses. changes in temperature, etc, etc.

What I'm saying is that the GTech is more indicative of reality, and the dyno is more suited to tuning. If the readout was 100hp or 150hp, and it still took him 8 seconds to 60mph, what's the difference?

matty-tC

also, i haven't seen an AFR with/without the intake so it could even be that the ECU is still in a learning period if it was reset or that an CEL was being thrown and the timing was backed off and the fuel increased.

matty-tC

I AGREE WITH ALL OF THIS UP HERE ^ ^ ^ ^ That's logical and makes sense. I'm not trying to argue this point.




It's a stopwatch. ADMIT IT! LOL

silversciontc

Yes the G-Tech is basically a stopwatch...

But it does all the complicated math that no one wants to do....

matty-tC

lol
thanks

PMok

among other things, yes it is a stopwatch. But it is also a 3-axis accelerometer. The timer starts automatically when it detects movement, and can determine mathematically when you've reached 60mph, 1/8 mi, 1/4 mi. So it's also a really long ruler or yardstick. It also reads engine RPMs from your cigarette lighter. It acts as a tachometer with programmable shift lights. It measures lateral Gs and can be set to warn you with blinking lights when you reach or exceed a set cornering G limit. And with the Comp or RR versions it is also a data logger, recording all this data in real time and allowing you to download it and play it back.

Rivulent

Best. Stopwatch. Ever.

acasanova

OMG enough already..lol im getting a headache lol im taking off my Injen short ram..lol