Syncro shifting, bad?

[T-Bird]

get a B&M powerglide they have them with more gears now and they don't say Chevy anywhere on them
Like the Chevy guys using Ford 9 inchers on their cars.

[mit5005]

Originally Posted by T-Bird get a B&M powerglide they have them with more gears now and they don't say Chevy anywhere on them Like the Chevy guys using Ford 9 inchers on their cars.

I haven't heard of those yet. Definitely something I have to look up. I mean our C6 is good but it soaks up more hp than a powerglide does.

[T-Bird]

Yeah B&M makes some good shit, sadly their website is somewhat vaque on some details.

[SFDMALEX]

Originally Posted by mit5005 Correct me if I am wrong, but it doesn't seem power shifting would give you an advantage over regular shifting during a race. I mean, you are still disengaging the engine from the drivetrain, so you are still losing power during that time.

Power shifting is this:

Your in 3rd at the redline or what ever. You shift to 4th just by pressing the clutch and moving the gear lever to the right slot with your foot FLAT on the thottle.

During the time that tranny is disconected from the engine with your foot on the floor your engine will hit the limiter and bounce. Hitting the limiter is not healthy.

In a race drivers have a very different strategy. They never rev the engine high. They have good 500rpm in reserver because if they drove a 3 hour race at the redline the engine would blow up after an hour or so. Im talking FIA GT here. So going to the redline while powershifting has zero advantages.


Lastly power shifting has no real advantage. If you properly lift you will change gear faster. If you would try to power shift on a non syncro transmission you would never change gear.

When you shift you up, the revs required for the next gear are lower then the gear that you are in. Depending on the gearing, but usualy in a race car(GT) lets say 3rd and 2nd are very close together. So if you want to shift from 2nd to 3rd you will theoreticaly need to drop about 800rpm from the redline in order to get the next gear up. That gear being 3rd if you are switching from 2nd.

The bottom line is that power shifting has zero advantages. Its just a fast way for inexperianced drivers(ricers) to switch gears fast on a syncro 'box.

[Vansquish]

SFDMALEX wrote:

The bottom line is that power shifting has zero advantages. Its just a fast way for inexperianced drivers(ricers) to switch gears fast on a syncro 'box.

That's not entirely true actually...consider a standing start acceleration run...in order to get the best off-the-line performance, you don't drop the clutch from the highest point in the rev range, nor do you normally accelerate from idle speed...then consider what would happen if you didn't have a flywheel on the engine, so when you pressed the clutch on a one-two upshift, the revs fell to idle speed...then you popped the gear in place and started running again...not the fastest way to go.

I'm trying to explain what I'm thinking, but having a little trouble expressing myself hehe.

Basically when you do a flat shift (powershift...etc...whatever you wish to call it) you're dropping the clutch from the redline each time you change gears...the difference between this and a standing start, redline-clutch drop is that the tires in effect have more grip...so that extra torque and power that is generally available higher in the rev range tries to act on the drive mechanism for the car. It DOES increase performance in acceleration tests because even if that extra power mostly goes to waste, some of it does find its way to the ground.

The best example of this in action is something I read a few years ago in Motortrend (I think it was MT at any rate it was some American auto mag). They had been testing the 405bhp Corvette ZR1 and couldn't get beyond the 5-secoind barrier in 0-60mph performance tests and Chevy had quoted the time as 4.9 or 4.7 or something like that. MT called Chevy, Chevy subsequently sent a test driver out and he "showed them how". He flat shifted each shift, and sure enough, the times were right on par with what the Corvette was claimed to be able to do.

In other words, flat-shifting does work, it can improve performance times, but it is severely detrimental to the internals of the engine and transmission, not to mention the rest of the drivetrain.

[SFDMALEX]

I agree with you. But I still think that a lighting fast lift (one we cant do ) will change gear faster then a flat shift. Just because of the fact that the next gear need lower rpm.

[coombsie66]

^^ Dude, actuall shift time has nothing to do with whether its a flat shift, or if you are lifting to rev match for the next ratio, the shift time is the time that the positive drive through the drivetrain is disengaged, flat shifting will cause the clutch to slip when you change gear into the next ratio, untill the revs are at the applicable level for that next gear ratio, so by flat shifting, you are actually transfering the increased inertia of the flywheel and engine parts (that are being overrevved compared to the gear that you have changed into) to the road, via the slippage of the clutch. So there is no difference in 'shift time' between a flat shift or normal shift if the clutch is disengaged for the same amount of time!
Flat shifting (as has been said does increase acceleration) and the FIA GT porsches sit on the friggin limiter all day long! They were on the limiters at the start of the LEMANS 24 hrs!!!!! They are so reliable they can withstand slamming the rev and pit lane speed limiter all the time.

And, the nascars and other racecars speculated about do clutchless gearchanges due to them having dog box's theh synchro's have massive teeth compared to the smaller road car syncros. This is why the race car boxes are soo noisy when they are idling or searching for 1st gear in the pits!

[SFDMALEX]

coombsie66- In FIA GT they dont flat shift All cars(most) are equiped with software that lifts for them. All they do is keep their foot flat. Some of the cheaper teams have a switch on their gear lever to cut the throttle when they shift.

And being on the subject of fast shifts you would think that in F1 they want to achieve the fastestest shifts no? Well tell me one time when you dont hear the throttle lifting when they upshift

[Vansquish]

As far as the rev-limiter is concerned, the reason it's in place is to prevent engine damage, so in all likelihood, if you're sitting on the limiter all day, you'll likely end up with a perfectly serviceable engine at the end of the day, the only problem is that because of the higher engine speeds there's just a bit more wear and tear associated with it. Overrevving is something that is far more dangerous, as at that point you're actually approaching the physical limits of the engine internals.

[coombsie66]

Originally Posted by SFDMALEX coombsie66- In FIA GT they dont flat shift All cars(most) are equiped with software that lifts for them. All they do is keep their foot flat. Some of the cheaper teams have a switch on their gear lever to cut the throttle when they shift. And being on the subject of fast shifts you would think that in F1 they want to achieve the fastestest shifts no? Well tell me one time when you dont hear the throttle lifting when they upshift

In the FIA morgan its a dog box, so you lift as you change gear, without use of the clutch (on the way up). And yes most have software that 'lifts' for them, but this is all integrated into what are pretty much automated sequential boxes (or are in the porsche GT3 RSR's i have seen).
And how are you gunna hear if the throttle is lifted in an F1 car!? They: 1. have such low mass flywheels/clutch etc that you wouldnt hear wether there was a lift, or that was the engine just being slowed to the speed relevent to the new rato.
2. Are pretty much a completely different ball game compared to the normal shifting debate we are having here.

All i am saying is that shift 'speed' is surely just the amount of time that the clutch is disengaged juring the shift, which is mutually exclusive from wether the shift is being done with the throttle flat or with a lift!?!
And yes flat shifting is detrimental to the longevity of the vehicles drivetrain, but u have to admit it increases the acceleration of the vehicle!?!?!