This is known as “flat shifting” as no clutch or lifting of the throttle is required during the gear change!įor 2wd YB cosworth powered cars, we usually recommend using a Quaife 60G 6 speed sequential gearbox for power outputs up to 450bhp, and its bigger brother the Quaife 69G for power outputs of 500bhp and above! Available with several gear ratio options, ratios can be chosen suitable for road and track day use, as well as ratios suitable for circuit or rally use. The result is a gearshift of near instant selection (typically 0.06 of a second) with the only driver requirement of pulling the gearstick. At this exact moment the ecu reduces engine load by a combination of fuel cut and ignition retard, whilst the driver keeps his foot firmly to the floor. In conjunction with a suitable ecu such as the AEM Infinity, rather than lifting slightly on the throttle, a strain gauge is added to the gear lever, indicating to the ecu when the driver is pulling the gearstick. This allows clutch less upshifts and speeds up gear changes to around 0.2 of a second. All that is required to change gear is to pull the gear lever and lift slightly on the throttle to reduce load on the dogs. The gears are engaged using a ring of dogs, machined in a manner that keeps the gear engaged under load. This type of gearbox features a gearstick that moves only forward or backward, in a “pull” to change up, “push” to change down format. The only recommended solution for these high output engines is to use a sequential dog engagement gearbox. In addition as power outputs go up, we start to experience gearbox failures such as stripped gears on high bhp cars, or damaged synchros due to forced “crunched” gearchanges. A traditional syncho gearbox struggles with this increased demand, often baulking or crunching, in an attempt to change gear quickly at high rpm. This results in gear changes that need to be made at both higher rpm’s and in a quicker time, so as to keep the turbo or cams “on song”. Often along with these higher rpm’s the power band becomes a little narrower, either due to the lairy nature of “race” cams or by the late spooling of large turbochargers. Usually as we increase the power output of both turbo and N/A engines, the extra power is made at higher rpm’s.
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