victor25

Ok, So I just figured out it is possible to build what I am looking for, and for not too much $$$. Awsome 10 Hz updates GPS chip for $40, G-force output board for $20, and $30 for a USB controller board to bring it all together for USB to my laptop. Now if I was just went to school to write a computer program for this kind of stuff... OH Wait, I did LOL. Too bad that was 25 years ago and everything I learned then is pretty much useless and forgotten now.
BTW a Bugatti Veyron from 0 to 60 is pulling 1.55G and a top fuel drag car is about 4G. So a 3G accelerometer should work just fine.
I ordered that accelerometer to see what the output looks like with the shark tuner. I'll let you know in a week or so

John Speake

The Analog inputs of the ST are high resolution, but you input signals must be 5v maximum. You will loose some resolution with the 3v output level of that accelerometer, and the fact you will be using only using a small part of its available range....

victor25

I didn't see a 5v version, so I went ahead and got the 3v. If anyone spots one let me let know or made something up to 7 at max by voltage.
John, whats the max input, and do you have a recomendation

John Speake

The max input into the ST aux inputs is 5v.

76FJ55

What about using something like an LM-2 as the interface for the accelerometer. This would give the ability to data log your RPM mixture and up to 4 additional 5V parameters. You could then easily plot accel vs RPM or any other parameter you have configured to log. Could also export to excel for further data analysis. Won't give you speed directly, so you’d have to play with the data for that but may be a convenient interface/logging tool.

victor25

Hey Guys... I recieved my accelerometer boards today and just couldn't resist doing a quick preliminary test.
I soldered it all together, ran 5v to it from a USB output on my laptop, connected it to the sharktuner, and ran a couple logs. Here is what it looks like
I think with a little work, we could do something cool with this. To me it looks just like a torque curve. This was a 2nd gear pull on a stock GTS.
I am running the filter on 5, I think if I went for 4 it would react a little quicker

victor25

I had some free time after returning from Florida today, plus the roads were dry and clean. So I decided to try out the accelerometer on the supercharged car and do some comparisons. As you can see the 2nd gear pull in the supercharged pulled way more g-force than the GTS... so I did a chart showing both side by side starting at 2000 rpms and running up to 5200. Wow what a difference in time, and also the supercharged car obviously puts way more air through the MAF. obviously more air through the MAF means more HP. I kept the setting exactly the same for both cars.
I want to do it again soon with different settings on the accelerometer so it shows a wider band on the graph, and thus shows smaller changes in HP
you can also see how the GTS gforce flattens out from 3400rpms to 4800rpms then drop off as it climbs tward 6000. And with the supercharged car the g-fors just keeps climbing with the rpms

inactiveuser1

Back in the 1990's used a DOS program that once you knew the 1/8 or 1/4 mile
It would figure out the rest as in G's and other info.I still had some sheets laying around of what it figured out back in those days.
Was trying to see what the difference was between an S4 and a GTS car back then.Knowing the estimated 1/4mile time,weight of car
with driver and horsepower it would estimate the rest.This is a sheet from the quarter junior way back from the mid 1990's on it.
It shows G's so maybe knowing the percentage you are pulling more than the stock GTS would give you G's you supercharged car is
pulling from the data you have so far.I used it on my other car that was running 11.10 in 1/4mile and 0-60 in 2.8 seconds and it gave
1.2's as G force when it left the line.The "s" next to .62 g meant it would spin some on take off.
Not sure what quarter junior looks like today on the software but link is:
http://quarterjr.com/
Program like this now most likely is:
http://quarterjr.com/quarter_pro.htm
There might be others out there like this that once you get your 1/8th or 1/4th.
Know today they had some for engine components cam changes etc.