Flat Changing In A Manual

[NT TURBO]

I have an auto, but wouldnt you be hitting the rev limiter soon as you tryn flat change (assuming you're using the clutch and holding it flat)

[Turbo6man]

I have an auto, but wouldnt you be hitting the rev limiter soon as you tryn flat change (assuming you're using the clutch and holding it flat)

Yes, of course ... the rev limiter is what allows you to do it without blowing your motor. In the old days, YEP the GOOD OLD DAYS :lol: when you flat changed the valve bounce is what stopped the engine revving any further ....

[KrasH]

most (all) manuals allow changes without pressing the clutch. My XF could do it, My Pulsar SSS could do it, haven't needed to try it on the T though. There is always a certain rev range when you can get it into the gear you want with only minor and sometimes no crunch. On decelleration you can easily pop out of gear without pressing the clutch, just by knocking the gear stick. Only real use for this way of changing is if a clutch cable has broken (happened in the XF about 6 times in the 7 years of driving it and once with the Pulsar SSS) and you need to nurse the car to a mechanic etc.

[Turbo6man]

KrasH> that is all true - but not while doing flat changes which is what this is all about ...

[KrasH]

@ Turbo6man

Fair comment, but just thought I'd meantion that clutchless changes should be used only when necessary ie. when the car is injured and not during flat changes that's for sure.

[Guest Scootre]

I always thought there was a sweet spot for each gear as to the number of revs you needed to be at for a successful flat change??

[Benny]

edo> a flat change is a gearchange with the throttle flat to the floor. You will be hard-pressed to do it in a street car without using the clutch - the syncros simply won't work and you'll be sitting in the middle of the road with a whole lot of mashed up gears and lots of time to watch the traffic going past. The V8 supercars use a Holinger non-syncro close-ratio gearbox and are designed to withstand the clutchless up-changes that you see the drivers doing.

Exactly what he said.

Treat your car with respect. Flat changing will get you no where.

[Turbo6man]

I always thought there was a sweet spot for each gear as to the number of revs you needed to be at for a successful flat change??

well yyes there is but it can't be achieved during a flat change which serves to indicate that you don't really understand the basis of how gears work.

Here's the gen ------

Gears give the engine a mechanical advantage in order to overcome the weight of the vehicle and to allow the vehicle to operate over a large range of speeds.

The higher the numerical ratio then the higher the advantage - on the road this translates to good power but low speed. EG. a ratio of 3:1 gives the engine three times the power but one third the speed of a ratio of 1:1.

Low (high numerical ratio) gears give more power ... high (low numerical ratio) gives more speed.

The more gears that are made available then the more power can be achieved and the more speed can be achieved --- all within practical physical bounds of course.

You will notice when changing up through the gears that with each successive upchange the engine speed drops - if you can't tell by looking at a tacho you should know this by the sound the engine makes. Herein then is the crux of the misunderstanding your statement highlights. It is impossible to match engine revs to gearbox revs (read "car speed") if you flat change - you have to take your foot off the throttle to allow the revs to fall in order to be synchronised for the next gear's required revs at that road speed.

Here it is mathematically:-

1st gear 2.95:1 gives (trust me I've worked it out) 11.5 kph per 1,000 rpm so at 6,000 rpm your car is doing 69 kph.

2nd gear 1.94:1 gives 17.6 kph per 1,000 rpm so at 69 kph your engine will be doing 3,900 rpm.

So you can see that to perfectly syncronise your first to second upchange those are the rev matching points - when you can do this perfectly every time you will no longer need syncros in your gearbox. :lol:

Sorry for the long-winded post but a basic understanding of these things will help our (particularly younger) members understand the mechanics involved and therfore hopefull be more sympathetic in their treatment of their cars (and wallets).

Jeff.

[Paranormal]

I had to change no clutch on my old GSXR750 bike when the clutch blew, passanger had to get off at the lights and push whilst I dropped her into first and chug along till he jumped on, after that it was flat out but would have to back off the throttle a bit to click the next gear. Down shifting would have to punch the throttle a bit to get the load off the box then kick it down. Basically you gotta get the load off the box, either using throttle or clucth that's what their job is, the clutch especially. It definatly would not save you time around a track, it may save a tiny bit of time up shifting just bliping the trottle whilst you slam the next gear but down shifting is another story, dont get the revs right and the box wont slot down a gear. If your comin up to a tight corner at say 160+ and you relying on both breaks and compersion to slow you down and cant get a gear your in a world of trouble. Youes the airline saftey procedure , place hands & head between legs and kiss your ass goodbye cause it will be the next thing going thru your head., end of story USE YOUR CLUTCH.

[junior]

Guys the whole point of the topic was to tell you there is a cutout between changes which confirms what I read.

So you can't flat change anyway and hence no damage was done.

Flat changing was only a way to describe the topic but under no circumstance would I attempt to do it to my T.

Yes I was driving quite spiritedly but that's the whole fun of owning a T