Received the g-tech meter on Friday, just 2 days from order for $50.00. Thanks for the link.

Ok, I can brake at .96 G's, accelerate at .31 turn at over 1.2 ..

What can you do??????

I know you 6 boys will have me in acceleration...but.....
I am running falken azenis 205.50.15's at 28# on all 4 corners.....175 # rear springs, 23mm front bars and both sway bars....

Lets see what you got!!!

herb

braking at 3x accel is pretty typical.
i'm skeptical of your lateral number tho...
was that a steady-state skidpad number ?
i could believe a sudden, transient-type turn, but i'm not sure i'm ready to accept 1,2g on DOT tires...

also not sure why you think 6's are faster in accel. size for size, the 4's low-range torque tends to give it better accelleration until the 6's high-end takes over. stock 2,0 /4 vs stock 2,0 /6, the /4's quicker under 70 as many AX wins attest. still, there's more to life than the stoplight Grand Prix and i ain't givin' up my 6 :-) ...

What are your 0 to 60 mph and 1/4 mile times? Those numbers will give us a very good idea if the g-tech is being truthful.

Okay Herb, you made me interpret my own accel graph.
I can do 0.57g in 1st, 0.37g in 2nd. That was before
I had the carbs worked out, and on the street tires
205/55. If I had a sequential modern box I could save
tons of time on accel but hey it's fun to own an
old car.

Those are the numbers that I got the first drive with the g-tech.....I need to do a complete skid pad, accel test, etc....


The braking is real. Repeated several times. Accel and laterial need more confirmation.

Still, I want to corner at over 1g.....

You're killin' me. My g-tech should be here this week and I'm dyin' to know how accurate it is. Get out there and do the acceleration tests.

it's a 2-axis accellerometer, yes ?

each axis needs its own calibration and correction factors. since you're confident in the braking number, try mounting the device in a succession of 90-degree change of position. the numbers should be independent of orientation ...

(everybody wants to corner at >1 g :-) ...)

Mine came in on Thursday. The teener isn't drivable now though!

Can you share the link again I have been away for some time.

G TECH

Guys, I'm curious - what is the G-tech really good for? How does knowing acceleration improve your tuning or driving (road course, not burn-outs)?

as with all instruments, Step Zero is establish a baseline.
then, after each change, re-run and compare to baseline conditions.
if things get worse, un-do what you did and see if you're back on the baseline. (if not, you perturbed something else...) if yes, the change you made was not effective.

can you pull more g's through a corner with more or less tire pressure? tighter or looser antiroll bar settings. softer or stiffer damper settings ?

i don't find the braking number very helpful unless you're fiddling with brake bias. the accel number of course helps you determine if that jetting, or timing, or air filter change really netted you a measurable performance improvement. (assuming all the other variables - like temperature, humidity, fuel load, driver weight... - remained constant too...

I ordered one but I can't help but feel a little skeptical because the price seems too good to be true. G-TECH sell it on their web site for $140 so how can this guy sell them on ebay for $50? I hope they've been properly calibrated and are accurate.

It will also tell you your drive wheel hp which is good to know when tuning or modifying your car. This might help you to get your motor's settings in the ballpark before you take it in for proper dyno tuning.

I just ordered one. For $50 it's sort of a no-brainer for me. I do like the look of the competition model though. I wonder if it's possible to hack a serial port into the cheap one and get a laptop doing datalogging to deduce fun stats. Might be possible to combine the megasquirt data with the Gtech data........??????

Anyone got any cool ideas? Is it possible to get a datastream out of this thing?

Fiid.

I got mine....in factory box with instructions....never opened, etc....I think that they can't move them for $139.

After playing with it, it is worth ~$50.00

I am looking at it for the baseline vs. improvement factor.

change brake pads, what happened.

Put in a v-8, what happens....

herb

That's exactly what I'm thinking. Also - I can run it in my girlfriend's miata to see how it stacks up to the 914 in the corners.

It will be interesting to get a quantitative analysis to go with the "ass-in-seat" accelerometer.

Should help a lot with sway bar settings and the like.

Does yours have any sort of computer interface?

Fiid.

here's my question - how can an accellerometer-based device produce valid data when it's not solidly mounted to the vehicle in question. even when i see the videos, it looks like it swings around on that suction-cup mount like a pendulum do. so what you've got is an accel in an accel - how stable can that be ?

unless the whole design concept is to have a position reference -inside- the box, measuring the motion of the case around it... in which case i think there'd be way too many variables (e.g. suction-cup rubber stiffness...) for the data to be valid...

i understand the suction-cup plumb-bob mounting is convenient - but how can it possibly be giving you valid data in transient maneuvers ?

what does the mounting information suggest? must it be flixibly mounted ? can you bolt it to the frame for improved accuracy ?

I just got one of these, waiting on a cable for my Kyocera smart phone to use it.

www.pdyno.org

Connects to the palmpilot (or palmphone in my case) and logs data. The mini sells for $149, but he has them on ebay for $49. Audiworld left a nice review : click here

Not affiliated with Hamilton, but I thought the cool factor was worth mentioning.

-DMA

When I watch MotorWeek on the Speed channel and they test the cars through the slalom I can see that they have a similar device mounted to the windshield.

Are your acceleration times a secret?

heres a g-circle of a session at Lime Rock. This info tells me I turn left and right at basically the same limits( to low), and that I brake to hard!!! LOL and that my car acclerates at almost .5G

Not a lot of data at this point....but now that I am playing with buttons....

0-60 times, 11+- seconds. HP--77.

Sounds like a tired 2.0!! Looking at some stock dyno runs, not too far off, I know my engine is tired.
I need an engine!! Lets see, 150hp will just about double what I got now....heh heh....

turning is .85+
braking is .95+

How about those who have large cylinders and cams....what hp # do you get??

0.85g of lateral acceleration is good. The key to getting accurate drive-wheel hp figures is to enter the true weight of your car. Jake Raby says he gets 150 (flywheel) hp from his 2270 motors.

Guess I'm still a little skeptical as to how you can compare apples to apples on baselines vs improvements.

ie, It's nice to know what your cornering g's are, but isn't the real question what is your AVAILABLE traction circle (per given chunk of pavement / pavement temperature / tires / tire temperature / suspension setup)? To find that, you'd have to repeatably run exactly the same line in the same corner, step over the limit (ie slide), and record your accels at the onset of the slide.

Once you had that, then you could divide your subsequent accels *in that corner* and get an approximation of how aggressive / conservative your cornering is.

Nice doodad factor, but no surprise their eBay price is so far below their MSRP.

The tool is most use on a track where you are running multiple laps throughout the day. Basically you can use it lap after lap to help smooth out corners so that you are running the minimal Gs on the car. Theoretically, you can then speed up your run on that corner when you have the better line.

When you are at the track for a whole day or weekend, constantly tweaking your line, any sort of performance feedback you can get is meaningful, because in my opinion - whatever you think about which laps were faster is probably wrong. Only quantitave analysis tells you what is actually improving your driving.

Same is true of suspension mods. If you are tweaking your swaybar slowly through the course of a day, you can look at how the peak cornering Gs alter with those adjustments.

Used right, it can be quite an awesome tool. And it's probably pretty good at what it was designed to do. Don't hammer screws in.

Fiid.

yes, but ...

what you -really- need for that is track maps and segment times, because the classic novice mistake is trying to go too fast in the slow parts, and too slow in the fast parts.

pulling lots of lateral g in a place you should be going straight looks good on the friction circle but it is not the fast way around the course.

i agree 'it's just a tool' and must be applied correctly. i'm in the business of making 'just a tool' software too.

i don't get the feeling this product has time stamps and lap markers so you can correlate individual g ratings with individual turns across multiple laps. there are products that do that, but not for these prices.

IMO they've found their price point. if you want to measure HP improvements, the safe & proper way is to go check out the local dragstrips and compare 0->60 and quarter-mile times, and trap speed. this is a decent lateral-g tool and there isn't really anything else in this price range that is. i think it probably leads to socially inappropriate behaviour on public roads, but i can't much blame the maker for that, and the marketer only to a slight degree...

I was wondering about this. If you could get a datasteam from one of these things and also from a GPS into a laptop, you could do some damage.

System could lay several laps you have done (or other people have done) on top of yours and show you how each technique you have tried is panning out.

This stuff isn't all that hard - I suppose it would have appeal for anybody who is spending time on the track, which ought to make it quite marketable.

Fiid.

Mike Valentine used the time he couldn't make radar detectors after leaving Cincinnati Milacron to design the g-Analyst, but i understand it hasn't been available for years. here's a similar accel-recording device

BelTronic Vector webpage to the g-tech.

i've seen data-acq systems that do it all, you don't really -need- GPS since if you've got precision accel's you can do inertial-nav just fine ... but nowadays it'd be pretty simple to provide a standard GPS-stream interface for them's that's got one - and it'd be a decent track of elevation change - although the portable GPS's i've seen update ~ 1Hz which is not going to provide a lot of resolution at racing speeds - track map is probably a much better source...

and then there's Extreme GEEZ that use a Palm Pilot for the core CPU acquiring data from their 3-axis accel device. this site was dormant for a while but i note it has recent updates now ...

anybody here a current SCCA member ? the current data acq companies used to advertise in SportsCar all the time ...

that magazine was my favorite part of being an scca member.

You could take the variables out by making a false steering wheel lock, accelerating to a given speed, locking the wheel, then slamming on brakes, all on a big flat piece of ass-fault.

I don't think it's a good idea in traffic, but you can cause repeatable events, just ignore everything else.


M

The unit I use to tell me what a crappy driver I am uses GPS, and 2 accelerometers to produce track maps, graphs, you can use a wheel speed sensor to further increase the accuracy of the measurements (the algorithm will interpolate with 4, instead of 3 data inputs). You can place markers on the trackmap at any location you want, then analyze your progress through that section as you change driving techniques or setup

Here is a shot at Lime Rock entering the braking zone for turn 1

you can tell Im braking way to early

in this screen shot, Im exiting the downhill turn, turning and on the gas, which is good. I used to tap turn thenget on the gas for this turn. Now I lift turn and gas, Im exiting the turn about 8 mph faster just changing that

sitting shotgun with other better drivers, getting more seat time, and using this logger Ive knocked my times at LRP from about 1:08 to 1:01-02's this year.... Im not even close to the top of the pack with the big guns in PCA

Limerock.. I saw that place on TV. What are you, some kind of movie star?

Why are there ants in the pits?



M

got more details on the hardware and software you are using.
Is it affordable for the average joe?

But this is exactly what the G-TECH Pro does best. It can very accurately measure acceleration times, speed and hp. I also seem to remember getting an email from Performance Products where they were advertising a similar unit made by Escort.

Here it is http://www.performanceproducts.com/Product...&producttype=10 .

I use a DL90 data logger, I bought it when the product was launched, cost me about $480, I then upgraded to a better antenna,5Hz sampling rate GPS for an additional $180. It aint cheap, but the amount of info it provides is amazing!

Affordable is relative, I had some mad money from my income tax return, probably should have used it for something more practical.

another fellow has just put together some software that overlays the DL90 output over video....kinda like the speedvison displays....

Ants in the pits WTF LOL

and it is clearly marketed as doing that ON PUBLIC ROADS.

Street racing is stupid!

street 'performance testing' is only marginally less stupid.

all these performance doo-dads know only two things - accelleration, and time.

it can only approximate a 0-60 time. it has no idea how much you car, as tested ACTUALLY weighs, and that's key.

every dragstrip has an accurately surveyed, safe quarter-mile with a safe shutdown area. and scales.

i acknowledge that there are places where 0->60 runs can be made on public roads in RELATIVE safety.
you want a dyno - go find a dyno - it's not hard. you want a dragsstrip - go find one - they're all over.
you want to do 0-60 runs on public roads ? well - i just think that's not very smart.

If the accelerometer produces accurate numbers (and everything that I have read indicates that this is the fact), the math involved is rather simple and will allow you to calculate speed, distance and hp with great accuracy. You can input your car's weight and then the device will also calculate your drive wheel hp with great accuracy.

"G-TECH/Pro is a very accurate machine, and the trap speed result that you get from the G-TECH/Pro is actually more accurate than the racetrack. Reason is that the racetrack averages your speed over a 60 feet stretch between two beams and G-TECH/Pro measures your speed at the exact 1/4 mile point."

http://www.gtechpro.com/gtechpro.html

never did i say it was not accurate -- IF you know your exact weight.
(how do you propose to find your exact as-tested weight? number-one answer: go to a racetrack...)

i said trying to do this kind of testing on public roads is stupid.

since you haven't addressed that issue and keep harping in accuracy, i gather you think street racing is just fine. stay off my street - i already have enough people thinking my street is start/finish at Le Mans.

Rich,

I take it you feel the same way that I do about street racing.

The data logger I use calculates rolling resistance, and CdA, its up to you to input vehicle mass.. the more accurate the info in, the more accurate the output.. as would be expected.. I dont really give a crap about 0-60

I want to preserve as much speed as I can, and use the brakes as little as necessary and always have my foot holding the accelerator pedal on the floor.. all on the track of course..

You did say "it can only approximate a 0-60 time" which is true but it can approximate this time with great accuracy. And, you're safe since Philadelphia is much too far away for me to drive there anyway.

The idea that an accelerometer-based device needs to
have any idea of the weight of your vehicle to determine
time-to-speed or -distance, is false.

The G-tech derives its speed readings by mathematically integrating its accelerometer outputs. Their accelerometers are good, but not perfect, and they add error to the integration. The longer you look, the bigger the error. That's why they talk about the drag strip (short time frames) not road courses (long time frames). For accurate speed on a road course, you need either a wheel sensor or GPS. The DL90 supports both, but they advertise the GPS because it saves you the trouble of installing sensors (which can be a royal PITA). The GTech FAQ promised "road course software" "later this summer". Don't hold your breath.

Mark, I think they were talking about needing the car's weight to get HP figures, not times.

did i say that? i don't think so... i agree of course.

for a power approximation, obviously a mass estimate is required.
how the device can tell the difference between mass and drag (aero and mechanical) is beyond me...

i just think this particular device is a SWAP - a Solution Without A Problem.
assuming your mass is invariant (?) it can tell you -- ahh -- pretty much what a stopwatch will tell you over the same repeated stretch of road ... if you were determined to do this kind of thing on a road.

which is also what a couple of pulls on a chassis dyno will tell you, or a couple of runs on the local dragstrip.

the lateral accel is interesting and probably worth the $50 it's actually selling for.

Your Mileage May Vary, your HP may vary, your mass may vary, and as long as they do it in a safe, sanctioned location, i'm okay with that ...

sometimes I just love when threads take these turns.... people state their positions, and defend them no matter what...others could have some enlightening input..

Rich I may have been reading your post wrong, whatever as
long as conclusion is the same.
SS6, I agree the errors will accumulate, and this type of thing
is more a toy. I've been into the cheapo logger concept for
a while since I like monkeying with electronics, but even for
short autocross I can't see getting the data to line up
enough to help you (without radio start-finish and/or GPS).
Like I'm going to wade through 6 or 8 runs of an AX course
and try to plot the stuff, and then remember what I was
doing each time through

Your point is perfectly valid. A reduction in drag (all else remaining the same) would increase the acceleration of the car and this would be calculated as an increase in power at the driving wheels. Made me go back and look at my old physics book. Apparently they measure acceleration on a "frictionless table". A chassis dyno would also have some drag associated with it and this may be the same as the drag produced by the road. The difference would be the aerodynamic drag. If I'm not mistaken, the power that the G-TECH Pro records should be the same as the chassis dyno minus the power lost due to aerodynamic drag.