Harry's GPS Suite Forum

Is it normal for there to be a big spike in lineal acceleration after first gear? It almost seems as if the car had some kind of turbo boost for a quick second (which is not the case). I've attached some screenshots of the first run (stock car, 6.26s) against the reference run (exhaust manifold with high flow cats, 6.14s). The best run (in red) shows greater overall lineal acceleration but it doesn't have the same big increase in lineal acceleration between 65km/hr to 85 km/hr. I recall that was a just bit of wheel spin half way through first gear in the black line run and for the red line with the best time, there was lots of wheel spin in the first gear. I'm using the XGPS 160 external GPS device.

Should I get an OBD II device to use with the XPS 160 for improved accuracy?

Thanks

Result The black line is stock. The red line has a modded exhaust manifold Is the big increase in the black line normal? I don't see the same for the red line. There was just a bit of wheel spin in the black line and for the red line there was lots of wheel spin through first gear.

The acceleration peak occurs for both lineal and lateral acceleration (dotted line). So this looks like a general shake of the car. Acceleration (recorded by IMU sensors) is not used to measure performance, it is just about speed development (GPS or OBS). OBD will add better responsiveness for speed development but will not change measurement of acceleration.

- Harry