Im not sure I understand how to properly select gears for a turbo setup. As I can gather, greater engine load leads to greater exhaust flow to spool the turbos. How exactly does a 3.27 gear place more load on the motor in comparison to a 4.56? I guess to simplify this, we can look at a 4th gear pull with a 1:1 ratio. A 3.27 gear will require 3.27 turns of the motor while the 4.56 requires 4.56 turns in the same time. doesnt it seem like more turns will require more energy?
Gears, load, and turbo
- Thread starter TheGord
- Start date
Think of the gears as a lever. By adding length the lever, the car is easier to move. The 4.56's are the same as lengthing a lever.
After thinking about it, If you had a 1:0 gear ratio the motor would turn once to turn the gear once. With the 3.27 the motor gets to turn three times to turn the gear once. This essentially means three turns to do the same work as one turn, thus each turn does 1/3 of the work.
Now, how does this relate to turbo spool? does the 1 loaded turn produce more exhaust than the 3 turns?
Now, how does this relate to turbo spool? does the 1 loaded turn produce more exhaust than the 3 turns?
A numerically higher gear will move you through your gears faster. With a turbo it is normally advantageous to stay in one gear as long as possible. So a numerically lower gear will be better for a turbo.
Think about hammering the car when the rpm is low, it takes a while for the car to accelerate. With lower (numerical) gears the car will have a greater load on the motor for a longer length of time compared to a higer geared car that will spin up more quickly. We are talking about slight differences but the load put on with the lower (numerical) gears will produce more exhaust gas quicker to accelerate the turbo turbine quicker producing boost quicker. That was how it was explained to me and may be wrong but sounded good at the time
TheGord said:
Essentially this last sentence is logically correct. Think of it as your engine exhaling into the turbine wheel, one long hard breath is going to create more pressure to spool the turbo rather than three short puffs. Of course a 1.0 gear isn't particularly practical for launches, but you'd be screamin' on the top end assuming all other things are equal to the task.
This is why you often see turbo guys "back up" to 3.55 - 3.90 gears when they were running 4.10+ on an n/a set up.
Btw, is that HAL in your sig pic?
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TheGord said:
Thank you, Dave!
:lol1:
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