So do you shift into 2nd while you're going 55mph, or start in 2nd from a stop? I just want to be sure I do this correctly.
Accept the fact that the engine and transmission controls will NOT let you break anything .................read the service manual on transmission controls protocol.
If your car is in otherwise good mechanical condition .......... Find a clear, deserted stretch of highway/open road. Pull to the shoulder and place the stick in 2 (This action says "This is my preferred gear"). Traffic all clear ??? Ease onto the road and, from a slow rolling start, stick the gas pedal through the firewall
and leave it there.The car will accelerate in 1st and at redline it will shift to 2nd and continue to accelerate. Just before the 2nd gear redline - ~6300 rpm - flip your foot off the gas pedal and allow the engine to brake the car down to < 20 mph. The transmission will downshift as necessary to keep the engine rpm in the proper band. Miss the 2nd gear redline and upshift ?....... Coastdown and do it again. Lots of smoke and crap out the tailpipe first time ?? Do it again......... You'll get to about 80 mph or so at the foot-off-the-gas point.
Why did we put the stick in 2 ???? Because that forces the downshift at high rpm coastdown: The theory behind the "WOT" is to load and heat the pistons and rings to the max during forced acceleration - then radically unload them with high vacuum during the coastdown. This load-heat-unload-cooldown chips away carbon flakes and allows the piston rings to work in their grooves, further shedding carbon buildup.
Where does some carbon buildup come from ??? Granny, grandpa and city driving. Gears - the 4T80E will always protect itself and the engine - neither allowing an over-rev or excessively high rpm downshift. You can, if you have the track room, take the car to speed limiter cutoff with the stick in 1st - upshifts will occur ONLY at full load redlines. I know for an absolute fact that my STS will do at least 143 with the stick in 1 - that's also just above where the 3 - 4 redline shift occurs. Yes, these cars (VIN 9) will do over 130 in 3rd.
......... and that procedure explained by
dkozloski is an old, time-honored method of cleaning piston tops......... DO NOT spray any solid water - mist only, and know that the procedure is not as effective in a throttlebody-long runner-center log intake manifold system as it is in a down-the-throat carburetor system. Large reciprocating aircraft engines have used water injection for high power application demands for a very, very long time.......... it slows down the combustion process and keeps max combustion pressure in the cylinder for more rotation duration - as well as cleaning the piston tops.
Of course, we could always read back through the entire thread - and post #9 - to get further insight ........... and, in answer to the original thread title, there's a sticky just above this thread which talks about the GM ring cleaning procedure using potent chemicals.