I just had a brilliant Idea (vis a vis Gtech testing your car)

I'm sure that all of you are familiar wit acceleration testers such as the Gtech and others that are on the market. Now then, we all know that because you're doing the tests on the street, your not going to get the most accurate representation of the power ur putting down because it factors in things like wind resistance and other natural elements. My plan: In my dealership we have a dyno (well its a pretty basic set of rollers that we use for e-testing cars, the machine doesn't read HP). Now, by putting up a car on a dyno, and running the Gtech tests on that for hp and whatnot, one would be able 2 better simulate a real dyno experience would he not? (now that wind and the elements don't need to be factored in). the only flaw i see in this would be finding out what correction factor to use for the rolling resistence of the dyno rollers. your thoughts?

Personally to me a real world gtech run that DOES factor in wind resistance etc is a more useful way to see what your car can do. Dynos are cool and all, but real world time figures are the best IMO. Which is something to be careful with on the gtechs. If the wrong data is inputted the resultant figures can be off by quite a lot. Which of course leaves the drag strip and your favorite circuit course as the ultimate way to judge your performance IMO. As an example of this i ran my neighbors custom 240SX intercooled turbo car last night, and though he had it dynoed just two weeks ago at 350crank HP in a light 2700lb car(suggesting real world ETs in the high-mid 12 second range), i blew his doors off(really, really badly, lol) from a standing start because he just couldn't get it too hook off the line. He was talking up his car every day since he got it dynoed, but when it came to the real world race, all that extra HP did was dissolve into a cloud of tire smoke and result in a 8-10 car length loss to a 350lb heavier P-car with probably 25 less HP. LOL.

What are you trying to accomplish by increasing HP in your car? Obviously, you want quicker acceleration. So, why not forget about measuring power and simply time test you acceleration? Establish an accurate way to measure your acceration and you have no need to know what HP you have, only whether you have improved your acceleration or not. HP figures, especially on boards like this, are grossly exagerated and many increases claimed never translate into a quicker car. BUT, some DO like to wave their dyno graph at you as they turn down an offer to run against you. I guess it like a guy putting a sock in the front of his pants, looks good to the woman, but he can't deliver

^ LOL @ the sock analogy, brilliant.

The car has to be able to move for the Gtech to work.

I really don't understand the disdain toward Dyno machines on this board. I feel that both the Gtech, Dyno, 1/4 track, road coarse have their value. Gtech- great for Do it yourself performance measuring. Example, you purchase the EVO intake but prior to putting it on your car you go to your favorite spot at your favorite time to do a baseline run. Install your Evo go back to your favorite spot during that time (assuming the weather hasn't changed much). You now can say whether your Evo purchase was worth it to you. Dyno's are the same as the Gtech but in a more controlled environment so you can come almost on any day and time to get relatively the same results without the possiblity of getting a traffic ticket. Of course the dyno doesn't illustrate 0-60 and 1/4 mile time. 1/4 track is worse than the previous two because of the weather. 9 times out of 10 you will have to wait 30 mins to 1 hr until your next run. Then there is drivers error, track may need to be heated, maybe a longer burn out is necessary, etc.. Road Coarse, is the same as the 1/4 and you will probably never get the exact same time on a lap. Any error can occur but mostly driver's error. Nothing is measured but time and maybe speed. Gtech performance IMO, is the best bang for your buck since it can test all of the above for $99 and a bit of deserted road or parking lot, but being at the track or dyno show with fellow club members is priceless..

As Steve pointed out, you need to have something accelerate to use an accelerometer to measure it If the car is stationary and the wheels are turning you have no acceleration.

as the other guys mentioned, the g-tech is an accelerometer so it has to move. instead, get a pda/scanner and some performance software. it hooks straight up to the OBDII port, measures engine speed and wheel speed and then calculates HP (after all variables have been inputted). use the gtech only for acceleration figures and not HP. too many variables come into play. WOW, it looks like i'm the only 100+ poster to pay for a rennlist membership

NAH, it's not disdain from this board, it's only from a certain few. dyno's are great, especially when you want to see HP #s that are least affected by environmental variables. of course dynos are also susceptible (much, much less though) so the KEY is to have the SAME operator with the same setup to see reliable changes. hell, you don't even have to dyno to get HP numbers. if you don't rust the HP #'s then use a dyno for acceleration #'s then.

who are yo referring to 1999Porsche911/JustAnotherPorsche ?