Yes a BMW

Volvord · **Posted:** Fri Feb 24, 2006 6:00 pm

Ok I know "a BMW" but it is one of my favourite videos.
http://www.supercarchallenge.nl/video/Assen-bmwSTW.wmv

Tha VZA · **Posted:** Sat Feb 25, 2006 12:28 am

god that thing sounds horrid...nails on chalkboard FTL...

cool vid though

EDIT: how does that tranny work exactly...like internally...those sequential tranny's (i think that's what this is) kinda confuse me... :oops:

ciao

Edicius · **Posted:** Sat Feb 25, 2006 3:56 am

hes just killing everyone. I'm definately impressed, I want to know if he catches up to the guy in first.

Ugly Duck · **Posted:** Sat Feb 25, 2006 8:50 am

That's one noisy differential. I mean, racing BMWs seem to have really noisy rear ends, but that one's exceptionally loud.

Volvord · **Posted:** Sat Feb 25, 2006 12:00 pm

Actually the noise is the straight cut sequential gearbox. All the gears in the trany are straight cut which increases their strength and does not produce any sideload like helical gears, the down side is the NOISE

Ugly Duck · **Posted:** Sat Feb 25, 2006 5:19 pm

But the pitch increases with road speed, not engine speed. If it were strictly the transmission, wouldn't it vary with engine speed? I've never driven a car with straight-cut gears, so I can't say for sure, but that's the way I envision it.

RaZ · **Posted:** Sun Feb 26, 2006 2:43 am

there are different kinds of sequential boxes, there are dog boxes, and the other kind I forgot.

None the less, the entire rotating assembly that is the transmission going into the output shaft spins. It spins faster and faster as you go up in speed (like your diff) and yes, it makes that noise.

Its the tranny.

Ugly Duck · **Posted:** Sun Feb 26, 2006 8:39 am

Yes, Raz - I know the entire output shaft spins at driveshaft speed, but since the input shaft and the entire countershaft spins at engine speed, and since the number of teeth (and therefore the frequency of tooth engagement) is different for each gearset on the mainshaft, I would expect some variation in the pitch as you go up thru the gears. The gears that drop power from input shaft to mainshaft are constant and forever linked to engine speed, and you don't hear these at ALL in this car. If it were the transmission, I'd expect to hear at least some engine speed related gear whine.

There's also almost always a 1:1 gear in the transmission, where power flows straight thru the input shaft to the mainshaft without the use of gears. In most transmissions that's fourth, but in BMWs it's fifth. In that gear, transmission noise is almost nonexistant. That never occurs in this car's case.

That's why I thought it was the differential.

Tha VZA · **Posted:** Sun Feb 26, 2006 6:51 pm

Matt...stop knowing so much...like is there and "Automobile Jeopardy" or sumthin??

i also here this 'whine' in the scooby do's which rally in wrc...i thought it was electrical interference with the intercom system audio...but now i am thinking it relates to the tranny...only it's not near as loud as this BMW

ciao

RaZ · **Posted:** Sun Feb 26, 2006 7:40 pm

Ugly Duck wrote:

Yes, Raz - I know the entire output shaft spins at driveshaft speed, but since the input shaft and the entire countershaft spins at engine speed, and since the number of teeth (and therefore the frequency of tooth engagement) is different for each gearset on the mainshaft, I would expect some variation in the pitch as you go up thru the gears. The gears that drop power from input shaft to mainshaft are constant and forever linked to engine speed, and you don't hear these at ALL in this car. If it were the transmission, I'd expect to hear at least some engine speed related gear whine.

There's also almost always a 1:1 gear in the transmission, where power flows straight thru the input shaft to the mainshaft without the use of gears. In most transmissions that's fourth, but in BMWs it's fifth. In that gear, transmission noise is almost nonexistant. That never occurs in this car's case.

That's why I thought it was the differential.

Man, did I ever get owned

Heineken makes me brave on posting, sorry Matt

None the less, straight cut gears ftw!

Ugly Duck · **Posted:** Mon Feb 27, 2006 8:24 am

Well as I originally said, I've never driven one so I don't know for sure. That was just my thought process. Don't consider yourself owned, 'cause I'm probably wrong.

Ian?

Volvord · **Posted:** Mon Feb 27, 2006 10:53 am

I have never driven a straight cut sequential but I have driven straight cut conventional and they are noisy. I agree with Matt that the noise should reduce when in the 1:1 but probaly because there are 6 straight cut gears spinning away the noise is just there

RaZ · **Posted:** Mon Feb 27, 2006 11:32 am

I less than three straight cut tasticness

Tha VZA · **Posted:** Mon Feb 27, 2006 12:05 pm

RaZ wrote:

I less than three straight cut tasticness

what?

ciao

Ugly Duck · **Posted:** Mon Feb 27, 2006 12:56 pm

less than three = <3 = heart

Yes a BMW

Who is online