Redline bad for GS350?
07-25-18, 07:19 PM
#16
Lexus Test Driver
First, the Toyota/Lexus 6400 redline is very conservative for a V6 of 3.5L with 94mm bore x 83mm stroke. It could easily rev another 1000 RPM if there were cams and head work to support the air flow required.
Second, carbon builds up an almost any engine except racing engines or propane, hydrogen or compressed natural gas engine. During low speed operation, the carbon can accumulate on the tops of the pistons, inside the head's combustion chamber and on the valves stems. Carbon sheds heat poorly so it can lead to a hot spot. This hot spot can cause the air/fuel mixture to prematurely detonate while the piston is still rising in the cylinder. This causes extreme loads on the rod and pistons. You will hear it. It is pretty loud at the extreme.
The way to combat low speed carbon build up is the exercise the engine by hitting redline from time to time. The much higher velocities will often break up the carbon and you will see a black cloud behind you to indicate you've done what we call back home an Italian tuneup. Unfortunately, this really only helps the pistons and combustion chambers. Once carbon builds up on the valve stems, it is very difficult to get off while the engine is still assembled.
Second, carbon builds up an almost any engine except racing engines or propane, hydrogen or compressed natural gas engine. During low speed operation, the carbon can accumulate on the tops of the pistons, inside the head's combustion chamber and on the valves stems. Carbon sheds heat poorly so it can lead to a hot spot. This hot spot can cause the air/fuel mixture to prematurely detonate while the piston is still rising in the cylinder. This causes extreme loads on the rod and pistons. You will hear it. It is pretty loud at the extreme.
The way to combat low speed carbon build up is the exercise the engine by hitting redline from time to time. The much higher velocities will often break up the carbon and you will see a black cloud behind you to indicate you've done what we call back home an Italian tuneup. Unfortunately, this really only helps the pistons and combustion chambers. Once carbon builds up on the valve stems, it is very difficult to get off while the engine is still assembled.
Free winding it out of gear doesn't produce the high cylinder pressures and uses very little fuel. You might see some black smoke but usually minimal unless the motor is so sooted up it looks like a diesel rolling coal.
If you do it in 2nd or 3rd gear, the engine load is greater and the velocities are higher, resulting in a more energetic combustion that is more likely to loosen carbon. The carbon is brittle and breaks apart under the higher pressures than it was formed under.
If you do it in 2nd or 3rd gear, the engine load is greater and the velocities are higher, resulting in a more energetic combustion that is more likely to loosen carbon. The carbon is brittle and breaks apart under the higher pressures than it was formed under.
I'll give you a couple more points to ponder. One, use only Tier 1 gasoline of the octane recommended so you are sure to get the additive package which helps keep carbon from accumulating on the valves and pistons, and helps keep the injectors clean. Many off-brands of gasoline do not receive the additive packages that Tier 1 gasoline brands do. Also, many regular octane Tier 1 gasoline brands do not receive the additive packages that the premium octane Tier 1 gasoline brands do. If you want the best - buy Tier 1 gasoline and use the highest octane. Second, when you give your car a WOT burst in 2nd or 3rd gear look at your rearview mirror. Knucklebus said you might see a cloud of black smoke/soot. You might, but that is telltale of a rich air/fuel mixture, which doesn't happen with today's fuel injection engines. What you'll probably see in your rearview mirror is a grey cloud - this is your carbon buildup being dislodged and blown out along with probably a little bit of condensation. Do it a second time and you won't see much of a cloud of grey...and do it a third time and you won't see any cloud. Now your engine is tuned like a purebred Italian race car on the roads outside of Maranello, Italy.
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jonathancl (07-27-18)
07-25-18, 07:26 PM
#17
07-25-18, 07:44 PM
#18
Lexus Test Driver
07-26-18, 08:18 AM
#19
First, the Toyota/Lexus 6400 redline is very conservative for a V6 of 3.5L with 94mm bore x 83mm stroke. It could easily rev another 1000 RPM if there were cams and head work to support the air flow required.
Second, carbon builds up an almost any engine except racing engines or propane, hydrogen or compressed natural gas engine. During low speed operation, the carbon can accumulate on the tops of the pistons, inside the head's combustion chamber and on the valves stems. Carbon sheds heat poorly so it can lead to a hot spot. This hot spot can cause the air/fuel mixture to prematurely detonate while the piston is still rising in the cylinder. This causes extreme loads on the rod and pistons. You will hear it. It is pretty loud at the extreme.
The way to combat low speed carbon build up is the exercise the engine by hitting redline from time to time. The much higher velocities will often break up the carbon and you will see a black cloud behind you to indicate you've done what we call back home an Italian tuneup. Unfortunately, this really only helps the pistons and combustion chambers. Once carbon builds up on the valve stems, it is very difficult to get off while the engine is still assembled.
Second, carbon builds up an almost any engine except racing engines or propane, hydrogen or compressed natural gas engine. During low speed operation, the carbon can accumulate on the tops of the pistons, inside the head's combustion chamber and on the valves stems. Carbon sheds heat poorly so it can lead to a hot spot. This hot spot can cause the air/fuel mixture to prematurely detonate while the piston is still rising in the cylinder. This causes extreme loads on the rod and pistons. You will hear it. It is pretty loud at the extreme.
The way to combat low speed carbon build up is the exercise the engine by hitting redline from time to time. The much higher velocities will often break up the carbon and you will see a black cloud behind you to indicate you've done what we call back home an Italian tuneup. Unfortunately, this really only helps the pistons and combustion chambers. Once carbon builds up on the valve stems, it is very difficult to get off while the engine is still assembled.
07-26-18, 08:34 AM
#20
Instructor
When I first test drove my car, knowing the sales lady well, she just flips me the keys to anything I want to drive has me check the gas. Once I got it up to operating temps, I merged into traffic on the Interstate at WOT to test acceleration. Big black carbon/soot cloud behind me. Got off the Interstate and got back on the opposite direction and repeated. A little cloud this time. Now that I own it, it never carbons up any more. None of my cars make soot clouds because they all see regular jaunts to redline. If it won't pull to redline, I either fix it or get rid of it.
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jonathancl (07-27-18)
07-27-18, 06:16 AM
#21
Racer
I do love my occasional WOT jaunts. Even sometimes mid throttle surprises me: north of 4k, the car loves to pull.
07-27-18, 07:47 AM
#22
Lexus Test Driver
07-27-18, 07:52 AM
#23
Instructor
07-27-18, 08:48 AM
#24
Lexus Test Driver
Ken Block goes WOT all the time - No carbon buildup in his engine!
07-27-18, 08:49 AM
#25
Lexus Test Driver
I am Speed!
07-27-18, 08:54 AM
#26
Lexus Test Driver
I think the only time the engine will hit the rev limiter is when you rev the engine out-of-gear - when in-gear the ECU's parameters automatically upshifts the transmission before reaching the rev limiter so there will be no hesitation/stumble/bog/floating due to the rev limiter kicking in.
07-27-18, 09:23 AM
#27
I think the only time the engine will hit the rev limiter is when you rev the engine out-of-gear - when in-gear the ECU's parameters automatically upshifts the transmission before reaching the rev limiter so there will be no hesitation/stumble/bog/floating due to the rev limiter kicking in.
The driving portion starts around 13:10. It's the IS350, but the engine and tuning should be identical to the GS.
07-27-18, 10:58 AM
#28
Lexus Test Driver
If you disable the traction/stability control does the transmission no longer automatically upshift? Is that why the rev limiter [appeared to] hit in the video? Why was the driver in the video using the paddles to upshift...unless by disabling the traction/stability control it prevented auto upshifts?
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