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Originally Posted by Buzz1167
Turbo spooling ideas...
Maybe Im just crazy, but why does everyone say the turbo spooling is so greatly dependant on the gearing, I figure it will spool to whatever rpm your at. - Are you saying that long gears are better becuase the turbo can "keep up" with the increase in RPM, where as it cant spool fast enough if you have a high gear, becuase of the time it takes to increase rpm is less?
I would figure, that when idling (off the start) you'd want a very short gear to get it spooled (and just give that one away), then when you drop down to the next gear, it will already be spooling fast enough for the drop into a long gear.
I think of this mostly becuase when your sitting at the start, your not going to drop the crap out of first in a fwd car, so the turbo wont keep up anyway, so just keep it as short as possible and use it to your advantage in the other 3 gears whitch could then be signifigantly longer w/o loosing anything.
So basically what Im saying, is that you wouldnt want a long first gear becuase the turbo would basically be going from a stop and trying to start there, with a larger mechanichal disadvatage.
I pose it as a question, because I dont have a turbo, yet, so I'm really just thinking about what should be happening, and If Im wrong could ya just help me out?
My 
Buzz1167
Jon N |
Ok, I didn't get much sleep,so sorry if it sounds confusing. Okay, I think the basic Idea is that witrh longer gearing, you stay in the optimal Turbo-RPM band longer. Shorter gearing means you have to shift quicker, longer gears you can go longer between shifts. Since you don't have to shift as soon, you spend a little more time in the turbo friendly rPM. Turbo's don't kick in really until a cetrain RPM, when they are spooled enough to creat more power. This is what cases "turbo lag." Basically, longer gears keep you in the turbo-friendly RPM band longer, this means you don't shift out of it as quick. The result is that you stay in the turbo-rpm band longer, so you get basically get a little longer out of your boost before shifting. Shifting puts you out of the rpm band, you need to wait till the proper engine rpm is hit to spool the turbo before making boost again. Since shorter gear ratios shift sooner, you shift out of the turbo rpm band sooner. Basically, longer gears leave you in the band a little longer. This allows you to make better use of the HP the turbo produces at full boost, since you arn't as quickly shifting out of the optimal turbo rpm band and having to let the turbo re-spool. The turbo will still have to respol when you shift, but you won't have to shift as quick with longer gears as shirter gears. Basically, longer gears like the LS are good for turbo's, shorter gears like the type-r rock for NA. The type-r, being a highly tuned NA motor, has nice short gearing. What gearing is best depends on idf you are going turbo or NA, but if you aere going turbo, you can read above and see why the longer gearing is better suited for turbo-apps. Because it keeps you in the rpm band for a longer time period, resulting in more time to use the HP created by the boost before having to shift and let the turbo-respool.