Downshifting?

[CleanAzzE30z]

this is gonna get good.

[misterlance]

Downshifting is part of driving a manual transmission correctly. There are also safety concerns that make downshifting a good idea. Say a semi-truck loses its brakes behind you coming to a stop light. You could either be prepared or not.

Mainly its about keeping aware and prepared to deal with whatever may happen on the open road. You certainly want to be in the correct gear for your speeds when say using a highway exit ramp that goes from about 60 MPH to 25 MPH. And coasting in neutral or with clutch "in" changes the handling characteristics of cars, especially RWD ones. Making uneven sufaces and wet sufaces tretcherous if you dont know how to keep the driveline settled.

It is just safer to be in gear and rolling than to have your clutch in a lot or to roll in neutral. You also have more spontaneous control. And if you are concerned about MPG, Wise use of the throttle coupled with minimal braking saves MPG.

And furthermore, I have seen studies that compare fuel used at idle and the fuel used in a downshifting situation. And the thing is, when you are downshifting, the raised RPMs are caused by driveline momentum, not throttle or spark. Therfore the used fuel is virtually the same. You could turn your car off and still use the engine for braking.

Oh, and one more thing. Downshifting aids in engine cooling. Which of course is always a good idea with BMW cooling systems.

[markseven]

oh damn my bad, really? i never knew that...so are you saying when you let off the accelerator...your not using any gas? i thought engines had to inject fuel and a spark in order to rev....

What? If you are in neutral, the engine is at idle - if you down shift, your engine doesn't shut off, does it? Fuel is consumed in both scenarios.

No, silly! I never said coasting didn't consume fuel.

[markseven]

Downshifting is part of driving a manual transmission correctly. There are also safety concerns that make downshifting a good idea. Say a semi-truck loses its brakes behind you coming to a stop light. You could either be prepared or not.

Mainly its about keeping aware and prepared to deal with whatever may happen on the open road. You certainly want to be in the correct gear for your speeds when say using a highway exit ramp that goes from about 60 MPH to 25 MPH. And coasting in neutral or with clutch "in" changes the handling characteristics of cars, especially RWD ones. Making uneven sufaces and wet sufaces tretcherous if you dont know how to keep the driveline settled.

It is just safer to be in gear and rolling than to have your clutch in a lot or to roll in neutral. You also have more spontaneous control. And if you are concerned about MPG, Wise use of the throttle coupled with minimal braking saves MPG.

And furthermore, I have seen studies that compare fuel used at idle and the fuel used in a downshifting situation. And the thing is, when you are downshifting, the raised RPMs are caused by driveline momentum, not throttle or spark. Therfore the used fuel is virtually the same. You could turn your car off and still use the engine for braking.

Oh, and one more thing. Downshifting aids in engine cooling. Which of course is always a good idea with BMW cooling systems.

Hey Dude! :D The OP was inquiring as to whether one downshifts when coming to a stop. I agree with your statements but do feel engine braking for the sole purpose of slowing the car to a stop is conducive to premature drivetrain ware.

[vivalegreg]

oops

[doucy2]

i put the clutch in and go into neutral, then initate a gear after sitting at the light for a minute.

[misterlance]

Hey Dude! :D The OP was inquiring as to whether one downshifts when coming to a stop. I agree with your statements but do feel engine braking for the sole purpose of slowing the car to a stop is conducive to premature drivetrain ware.

Hey Man! I saw your thread for the SSK. Search here, I think the guys here have used every stock Z shifter in their 30's.

And if you match your shifts, I cant imagine there being any premature wear. But I will say when I am cruising in traffic and coming to my hundreth stop light, I will only downshift as far as third (If I can even go that fast).

[markseven]

Hey Man! I saw your thread for the SSK. Search here, I think the guys here have used every stock Z shifter in their 30's.

Yeah, Lance I saw that thread - I'm still considering all options. What are you using? Stock or SSK?

[misterlance]

Yeah, Lance I saw that thread - I'm still considering all options. What are you using? Stock or SSK?

I am rebuilding my E30 and havent got to that portion yet. It was stock, but when done, will not be. I read on here that the Mz3 shifter isnt as knotchy as the Z4, but I dont look forward to finding one.

https://secure15.nexternal.com/shared/StoreFront/default.asp?CS=bimmerworl&BusType=BtoC&Count1=400768458&Count2=317908883&CategoryID=56&Target=products.asp

Looks like B&m has a few versions out as well.

[markseven]

I am rebuilding my E30 and havent got to that portion yet. It was stock, but when done, will not be. I read on here that the Mz3 shifter isnt as knotchy as the Z4, but I dont look forward to finding one.

https://secure15.nexternal.com/shared/StoreFront/default.asp?CS=bimmerworl&BusType=BtoC&Count1=400768458&Count2=317908883&CategoryID=56&Target=products.asp

Looks like B&m has a few versions out as well.

Thanks for the link - bimmerworld: "The fundamentally finest shifter for the pure BMW enthusiast"... maybe I should start a new thread or add to the other one and end this hijack ;)

[Rennsport]

wow, i thought this thread was about shifting, not shifters....

lol, anyways, i r3v match downshifts all the time. just the wat i was tought to drive a stick.

[808BMW]

So what you are saying is the engine knows you have downshifted and cuts fuel delivery?

No fuel = engine not firing = no power steering, no power brakes...

I think you are mistaken

When you let off the throttle, the engine will cut fuel. If your rpms are up (being in gear, like while downshifting) the rpm's will keep your motor going. If you are in neutral, the engine will cut down until it hits idle, then the ecu will inject fuel.

If you rev up your car, turn off the key, let it rev down, and turn the key back on before it dies, your car will run. The engine is already spinning, and will continue to do so until it slows down to 0. How can the fuel be injecting while its revving down if your key is off?

The engine doesn't need to fire to spin. PS and brakes are spun by the engine, whether its injecting fuel or not.

oh damn my bad, really? i never knew that...so are you saying when you let off the accelerator...your not using any gas? i thought engines had to inject fuel and a spark in order to rev....

Yes, no gas pedal= no gas (until you hit idle, then motronic takes over). They need spark and fuel to rev, but your not revving it, your downshifting.

[808BMW]

anyone here have a clutch stop ?? im pondering getting one....but cant really think how it works?? is it where you kinda set it at a certain engagement point and prevent the pedal from going all the way to the floor, for quicker shifts? wouldn;t that increase wear on a clutch?

also who here when comming to a stop, before rolling off, keeps their car in gear with the clutch pushed in...even sitting at a red light....does that create any wear on a clutch?? as opposed to just putting it in neutral...until the light turns green then putting it in gear??

Clutch stops are adjusted slow the clutch will FULLY disengage. It's just there to stop the dead travel behind it. If you need to only push your clutch down 4 inches, then why go all the way to 7, just put a stop at 4.

Sitting in gear at a red light doesn't wear your clutch, but does wear your throwout bearing. Better idea to wait in neutral.

[markseven]

When you let off the throttle, the engine will cut fuel. If your rpms are up (being in gear, like while downshifting) the rpm's will keep your motor going. If you are in neutral, the engine will cut down until it hits idle, then the ecu will inject fuel.

If you rev up your car, turn off the key, let it rev down, and turn the key back on before it dies, your car will run. The engine is already spinning, and will continue to do so until it slows down to 0. How can the fuel be injecting while its revving down if your key is off?

The engine doesn't need to fire to spin. PS and brakes are spun by the engine, whether its injecting fuel or not.

Yes, no gas pedal= no gas (until you hit idle, then motronic takes over). They need spark and fuel to rev, but your not revving it, your downshifting.

Cool, my mistake - learn something new everyday.

[nando]

So what you are saying is the engine knows you have downshifted and cuts fuel delivery?

No fuel = engine not firing = no power steering, no power brakes...

I think you are mistaken

it is you who are mistaken

the ECU will cut fuel when the RPMS are above a certain level and it detects that the throttle is closed (via TPS). once the RPMS drop to a certain level it will begin to meter out fuel again to keep the engine running. if you are coasting with your foot off the gas and in gear, there is no fuel going to the engine. as soon as you open the throttle though, the ECU will begin firing the injectors again.