Fairfax 4.0T

But it is really boost, so who knows???

As to the cause of the spin, I believe my initial indication of a lift was wrong. I created a video with the throttle position showed compared to the video. It shows that the back in started to come out, and very shortly after the back end broke out, he lifted. The lift wasn't the cause but an effect. It seems like it was only about 2/10 of a second for him to lift after the spin.

In view of the overlayed video, I now believe the cause was him achieving full boost at the end of the turn, greatly increasing horse power/torque, and cause the rear wheels to have to much power.

Fairfax 4.0T

I have the boost logging set to have a max of about 14 psi, and a minium (at idle) of about negative 9 psi. When the motor is stalled/off, the boost gauge reads zero. What must have been happening is that the car was near stalling due to the spin and tire skid. That near stalling cause the loss of vacuum at idle, which would bring the boost closer to zero. In the desplayed graph, you see the boost climbing towards zero PSI, and not vaccum, because of the near stall. The graph I posted doesn't display the boost scale.

As to the throttle position, there is a sensor on the 944 on the throttle bottle which feeds to the CPU the throttle position. I just tapped into that wire for the data logger.

Wind-n-Water

but glad you figured it out. To really investigate the manifold pressure (ie: boost/vacuum), it should be look at along w/ RPM and throttle butterfly valve position. In addition to accessory rpm 'kick-ups', one has to be careful of what goes on between pedal position and butterfly valve, esp w/ the newer throttle-by-wire cars now a days.

Also, do you know if the 'boost' gauge is a relative or absolute pressure gauge? ('relative' to static atmospheric)

This brings back a point at work that we drill into our young engineers' head.

<i>"A graph is <b>USELESS</b> unless it shows scales &amp; their units"</i>

Start paying attention to this and one soon will realize how much 'tuner' literatures are littered with useless graphs.

Potomac-Greg

Yeah, that was my reaction. Throttle induced oversteer. Getting off the gas made it a tank-slapper.

arob

Your car sounded nice on the track, Ryan. Consdier track wheels if you plan to continue doing DEs.

Fairfax 4.0T

In the first instructor track session, I went out alone when all of the cone works were standing around.

I should have offered a ride to you guys, but I wasn't thinking, sorry. Next time, please ask as my brain sometimes doesn't work too well.

Thanks for helping out with everything.

Also, Roger, thanks for the heads up on the speed traps on the way home. Much appreciated.

Jimax

I'm glad.

I picked up eight cops on the drive home. My V1 was going nuts every few miles. It was crazy. I figured, let me call to give you guys fair warning.

Wind-n-Water

blow past the cops. Drawing/screen all 8 of them out after you there by leaving the road clear for everyone behind! P

BlueDog

when they know the motorcycle guys are at the track. They were over on Shenandoah, while the Kart Club was on main.

Roger @ CA

Good to see you too, hope you had a great time and come out more often. BTW, ygm too.