Re: Shutting car off while in gear
 

I've run it by my dad a few times.. he doesn't seem to think it's a great idea lol, so I ran it by you guys instead!

I use the B&M Hammer which is a ratchet shifter so I can only go one gear at a time which makes up to neutral impossible. It's not a huge deal I do run an o2 sensor in the collector that records the entire run and that has helped tremendously in tuning but my next objective is to get each individual plug reading the same which is a great perk of EFI.

Re: Shutting car off while in gear
 

For what it is worth ATI doesn't recommend it at all - even with a Clean N. Once for a plug reading, okay that is cool. But the guys that do it ever pass are just reducing the life of the unit. In the pits, on the track, doesn't matter. When the engine is stopped, the transmission pump is not moving any fluid to lube the gearset that still being spun by the driveshaft.

Re: Shutting car off while in gear
 

I've been told in a TH400 clicking it into neutral causes the driveshaft becoming the driver and the way it multiples will cause one of the drums to spin to 20000 rpm+ and it can go boom.

Re: Shutting car off while in gear
 

Could somebody explain what "clean neutral" means. I have a reasonable understanding of automatic transmissions and have heard this term many times but never an explanation. Thank you, Louis Jeffery

Re: Shutting car off while in gear
 

Clean neutral valve bodies dump the forward clutch and keep the direct clutch applied so all the gear train rotates at the same speed. The engine has to be kept running (idling) to keep the direct clutch applied.

Jim Mantle V/SA 6632

Re: Shutting car off while in gear
 

I've put many runs on both a Coan XLT-350 and a Pro-flite with clean neutrals shutting off above 10,000 RPM. Never had an issue with either, tear down at end of season shows no signs of unusual wear. I have noticed it seems to take longer for the T-350 to "let go" of the engine not sure why but never caused a problem.

Re: Shutting car off while in gear
 

The reason it takes so long to dump the clutch at high rpm is due to the fluid in the clutch drum. As the drum spins the fluid is centrifically forced to the OD of the drum and effectively creates a higher pressure on the clutch piston. The feed for the clutch is closer to the centerline of the piston. When you want to dump the clutch, a valve opens and exhausts this feed channel, the problem is that the spinning drum keeps high pressure at the OD of the piston, and limits how much oil can be moved to the centerline of the piston. Most pistons or drums have a small check ball that is machined close to the OD of the drum. When the clutch pressure drops to a designed value the check ball comes off its seat and exhausts the clutch oil. At high rpm the clutch centrifical oil pressure may be too high to unseat the check ball and basically keeps the clutch on. Some tranny builders know this and drill a small hole (constant bleed) near this check ball, That is a "fix" to try and get the clutch off quickly, and is unaffected by rpm.