PMok

I did a few baseline runs a few weeks ago with my G-tech Competition (updated to v4.0 which is equivalent to the G-tech RR model now being sold). I entered a vehicle weight of 3300 lbs which in retrospect is probably too high, with a curb weight of 2950 lbs + my weight it ought to be more like 3150 lbs. Anyways those familiar with the G-tech know that based on the acceleration (G-force) it measures over time and the weight you enter it can estimate your horsepower on a simulated dyno plot. The numbers it generates of course can't be directly compared to an actual dyno since the data is generated from actual runs down an empty road, and thus factors like aero drag, surface traction, etc. result in lower numbers. What it does allow though, is for comparison before and after a modification such as installing an intake or exhaust. Anyways without further ado, the baseline results (best run):

Stock Scion tC (4-spd auto):
0-60: 8.298s
330ft: 6.890s
est max hp: 109.8 hp @ 5070rpm
est max tq: 116.0 ft-lbs @ 4142rpm

I then removed the stock airbox and installed the K&N Typhoon CAI according to the instructions. The only thing different I did was drill a few small holes in the plastic cap covering the lower inlet in the bumper that the cone filter sits right behind. I doubt the holes make much of a difference though.

after driving around for a few days to let the car get used to the intake, I did some more G-tech test runs. To keep the results comparable I stuck with the vehicle weight setting of 3300 lbs. My best run:

0-60: 8.493s
330ft: 7.006s
est max hp: 111.1 hp @ 5427rpm
est max tq: 116.7 ft-lbs @ 4091rpm

my conclusions? looking at the dyno plot the car seems to have lost power and torque in the lower end to gain a little high end power--and not much at that. More test runs will probably be needed to confirm this, but in my mind the gain is hardly worth the loss across most of the usable power band. Sure the intake sounds more aggressive but it's more bark than bite to me. That seems consistent with what I've read from others' posts who installed a CAI but now that I have hard numbers I really have to question whether it was worth it. Sure I may not notice -4hp just as I probably wouldn't be able to feel +4hp but who really wants to pay $200 to lose power just for a cool sound?


G-tech plot results (hosted on Imagestation which requires an acct but if someone wants to download and repost so everyone can see, feel free).

http://www.imagestation.com/album/pi...3094911&idx=16

lildreamah

That's not much for gains but then again it's not being done on a dyno either.

IMO G-tech = Butt dyno

OuterHeaven

ya g-tech may equal butt dyno but what do you think is more realistic.... dyno runs are only on the dyno and not actually on the street. the g-tech does have its merits as it will show you approximiatly how much power you are losing as you increase speed (more drag force) while a regular dyno will not. the g-tech is more real world then a regular dyno in my opinion. I know a real dyno is more consistant, easier to calibrate, and easier to tune on but for bolt ons i think the g-tech is worth using.

Gmoney

something is off there. theres no way in hell a tC put those numbers down on a gtech. something is wrong.

matty-tC

g-tech SUCKS

it doesn't really matter what it says

PMok

why do you find the results hard to believe? I see a lot of rhetoric but nobody has backed up their statements with any facts. Someone convince me that a) the G-tech is unreliable for seeing the results of simple bolt-on mods, or b) the results are inconsistent with what everyone else has seen after installing a Typhoon on their tC.

NoLimitzBuilt

the power numbers dont seem to be right, they seem really low.

TurboMe

gtech isn't accurate but it can be use for precision for gain numbers.

PMok

Thrawn

Sensible questions and request.

Something to consider is temperature differences. When did you do your baseline run? What was the ambient temperature? What about when you tested after the install of the K&N, what were the conditions like? I get the feeling that you were suffering from heat soak at the time you tested the K&N. That's not the G-tech's problem, that's the nature of a long, metal, CAI. If I were to guess, I'd say your results are pretty accurate and more indicative of real world performance gains/losses.

Dr_Isotope

iTrader: (1)

I think many of those discounting the results of the GTech test may be CAI owners...

The test he did is basically valid. So long as he used the same settings on the GTech for both tests, the results are an accurate comparison. He picked up some HP, a little torque, and got slower overall. Sounds about right.

Thrawn

Something else that occurred to me to help standardize the results, along with the ambient temperature, is the road used to do the testing. Would definitely want to be on the same road/parking lot for each test that way road conditions don't skew the results. You may very well have, but, I don't think you specified that in your post (unless I missing it).

With as many factors standardized as possible, as PMok stated, the Gtech should be a pretty good tool to measure relative performance gains/losses. The same goes for a dyno, they shouldn't be used to measure absolute power, just relative changes in power from mod to mod. Unless your on an industrial one that measures power at the crank, of course. I doubt many people have access to those.

matty-tC

explain to me exactly how it precisely measures horsepower?

PMok

both before and after test runs were done at the same location and at night when the air was cooler (around 68 degrees). I basically would start the car (engine was cold), drive to the location which was 5 min away and do the test runs. So I don't think that would really be enough time to heatsoak the CAI. In any event I did what I could to ensure that conditions were the same in all test runs. I did not do any brake holds, from a complete stop I would just floor the throttle.

one thing I thought about trying was removing the plastic cap from the lower bumper inlet completely. I bet that the cold air coming directly into the filter would help some, but of course I would not run the car that way every day.

matty-tC

it's still about 20hp off...

zoltiz

I'm with PMok on this one. Newer G-Techs are pretty reliable, at least when it comes to 0-60 times, and that's what matters.

I'm back to stock airbox with TRD drop-in after about a week with K&N CAI - if anything the car felt bogged down. Intakes should be in Sound/Looks section, not performance, especially with the tC.

Thanks for doing the research!

PMok

the G-tech has 3 (x, y, and z-axis) accelerometers that measure movement or acceleration in any direction. It also reads your engine RPMs. The computer can take the measured acceleration, combined with elapsed time and RPMs to calculate distance, speed, HP and torque. The only additional variable you need to enter is the vehicle weight (which I sort of overestimated as I mentioned earlier).


I am no scientist so I will leave it to the people at G-Tech to explain it:

The Gtech's ability to measure horsepower and torque is one of the product's most exciting features, but also one of the most confusing and frustrating to use unless you understand how to make the measurements and how to interpret the results. This page is a collection of links of information that pertain to horsepower and torque measurements.

First some background on shop chassis dynamometer measurements:

When you take your car to a shop to run it on a dyno, there is a prescribed driving technique. For example, many dyno shops have you (or more commonly, a shop technician) roll the car through the gears until you're in 4th gear (or whichever gear has the lowest drivetrain loss). Then in this gear you run your car through the RPM range, and the TQ & HP are measured as the car accelerates through a wide RPM range in this gear.
With a shop dyno, you should not expect to get numbers that match a manufacturer's published numbers, since published values are typically the engine output at the crank, not delivered to the wheels. A chassis dyno measures the power delivered to the wheels, as the torque delivered to the wheels is what works against the inertia of the rollers on the dyno. Typically, a chassis dynamometer measures how the spin rollers are accelerated by the vehicle's torque that is delivered to the wheels, and HP & TQ are calculated from this. Many dynos can also apply one or more "correction factors" that basically just adjust the shape and values of the curve to account for factors such as temperature, humidity, estimated drivetrain loss, etc...
Results vary from shop to shop, due to calibration variances, a multitude of correction factors, and the varying levels of expertise and experience at the shop. For this reason, when doing tuning, it is important that you find a shop that you trust, and then stick with that shop, as the results you get over time can be compared to each other directly (if the shop is worth its salt, you should be able to assume any differences you see from one visit to the next are due to changes in your vehicle, not the shop).
Basically, a chassis dyno measures torque by seeing how vehicle accelerates the rollers, and then (with knowledge of RPMs) calculates HP from torque, since

HP at a given RPM is
equal to:

Torque * RPM
----------------
5252


The Gtech, on the other hand, does just the opposite.... it calculates HP from velocity, acceleration and vehicle weight, and then (with knowledge of RPMs) calculates TQ from HP, using the same formula listed above.


http://www.gtechprosupport.com/support/HP1.htm

Dr_Isotope

iTrader: (1)

It does indeed help. The CAI draws air from a worse location than the OEM piping IMO, in that it puts the inlet closer to the opening that faces the exhaust manifold. Drawing air from outside the vehicle drops cruise intake temps by 3-5º, and reduces idling intake temp by over 20º. And running it that way every day seems to be no problem-- mine is ducted directly from that point to the inlet on the K&N equipped airbox...

matty-tC

that's all fine and dandy but unless it knows gear ratios, weight, etc. it's not accurate

zoltiz

You are kidding, right? When was the last time you plugged the gear ratios in the dyno software before doing a pull?

Actual numbers do not matter. The difference matters. 0-60 matters. And G-Tech is pretty good for it.