drive by wire and rev-matched downshifting...

4MLA1FN · 01-14-2003, 06:33 AM

there was a thread, i think on the impreza forum, about the sti using dbw and how that will make heel-toe near impossible? supposedly this is because the throttle is managed when the brake is applied. in other words, you can't blip the throttle under breaking. is this the case?? man, i sure hope not. me, like probably most of us, match revs when shifting.

CloNeGTS · 01-14-2003, 01:56 PM

I sure can't believe that would be true on what is being touted as the ultimate daily driven race car. I sure haven't heard of such complaints on other cars with DBW, such as the M series from BMW.

Jeff_DML · 01-14-2003, 02:05 PM

Our 3 series wagon has drive by wire and I can blip the throttle while breaking to heel-toe downshift with it. I assume the STi will be the same, it better be

Jeff

Marine06 · 01-14-2003, 04:42 PM

It depends on how Subaru implements dbw. I was bummed when i read that it had this "feature." Personally, I don't think Subaru overlooked dbw in its implementation.

Anonymous · 01-15-2003, 10:18 PM

Bahh DBW is almost always worsethen regualr mechanical throttle. It cost more and has no real benefits.

My 2 cents.

4MLA1FN · 01-16-2003, 12:30 AM

fwiw here's the thread the prompted my question:

http://forums.nasioc.com/forums/show...;highlight=dbw

thebigshow · 01-16-2003, 07:51 AM

could anyone b so kind as to givin me a crash course in rev matchin? thanks.

alfredob1 · 01-16-2003, 07:56 AM

My best explanation is when downshifting you giving it gas before engaging the clutch after shifting to the lower gear. The amount of gas you give should be sufficient enough to match the RPM's you were doing in the previous gear. That way the car doesn't lurch when you completely let out the clutch.

If someone has a better explanation please share.

thebigshow · 01-16-2003, 07:59 AM

ok, i kinda thought that. now this is just what u do when u're slowin down, right? in that case, i just brake a little and let the clutch out slow. if u're referrin to downshiftin when u're passin or whatever, then that's something else entirely. thanks.

4MLA1FN · 01-16-2003, 11:17 AM

as you note, heel-toe isn't really necessary is your coming to a stop. it's best for taking corners in a spirited manner. you can brake, shift smoothly into the gear you need to for getting out of the corner, and it also keeps the engine in the power band so you can jet after the apex.

i definately rev-match when downshifting to accelerate past someone. when done right, the feeling of "instant" acceleration is awesome. on a road trip, i had a friend following me. at one point, to get around a slow car, i downshifted and accelerated. once we reached our destination, he said he was stunned how quickly my little se-r i pulled away because he didn't see the car dip/lurch the way it would when a normal downshift is done to accelerate.

in general, rev-matching it much easier on the clutch disc since it minimizes slipping due to a rotational difference between the engine and the tranny.

there is a thread about this in the "off-topic" forum:

http://www.imprezawrxsti.com/postnuk...opic&t=805

Agent Chobos · 01-16-2003, 10:09 PM

Quote:

Originally Posted by alfredob1

My best explanation is when downshifting you giving it gas before engaging the clutch after shifting to the lower gear. The amount of gas you give should be sufficient enough to match the RPM's you were doing in the previous gear. That way the car doesn't lurch when you completely let out the clutch.

If someone has a better explanation please share.

I think before shifting would be the more proper way. You can do it after the shift, but before letting out the clutch, like you said, but doing it before popping it into gear would also be easier on the tranny & synchros, not just the clutch. This is also the idea behind double-clutching.

BHODGES3 · 01-17-2003, 07:45 AM

What is "granny shifting" and "double-clutching"?

Agent Chobos · 01-17-2003, 05:18 PM

The way Mr. Quarter-Mile-at-a-Time used it, he meant "granny" shifting as just normal shifting: clutch in, shift, clutch out.

Double-clutching is essentially clutch once to shift into neutral, clutch again to shift it into gear (while matching revs). The trick of course is to do it quickly.

Why anyone would actually double-clutch during a DRAG race is beyond me, though. Likely just more movie BS, a la "Motec system exhaust".

BHODGES3 · 01-21-2003, 06:54 AM

Why would you need to double clutch then? Wouldn't you just clutch, go into neutral, match rev's, shift, and then de-clutch? And for the life of me... has anyone heard of Mashimoto ZX tires? heh. My only thought is that they *might* be some kind of street-racing tire popular with the Japanese Import Crowd. Good call on the F & F question by the way.

4MLA1FN · 01-21-2003, 07:52 AM

Quote:

Originally Posted by BHODGES3

Why would you need to double clutch then?

i don't think people need to double-clutch anymore. we've got synchros that make changing gears effortless. i guess double-clutching would make life easier on the synchros, in theory.

01-14-2003, 06:33 AM	#1
4MLA1FN hatin' ovals Car: 04 subaru wrx sti Location: alexandria, va Posts: 2,460 Join Date: Jun 2002 Trader Rating: (0)	there was a thread, i think on the impreza forum, about the sti using dbw and how that will make heel-toe near impossible? supposedly this is because the throttle is managed when the brake is applied. in other words, you can't blip the throttle under breaking. is this the case?? man, i sure hope not. me, like probably most of us, match revs when shifting. This ad is not endorsed by this member. Please register or login to hide this ad.

01-15-2003, 10:18 PM	#5
Anonymous STI Driver Posts: 238 Join Date: May 1978 Trader Rating: (0)	New subaru articles found on the web Bahh DBW is almost always worsethen regualr mechanical throttle. It cost more and has no real benefits. My 2 cents.

01-14-2003, 01:56 PM	#2
CloNeGTS S204 Racer Car: Solo II, WRC Location: Overland Park, KS Posts: 2,776 Join Date: Oct 2002 Trader Rating: (1)	I sure can't believe that would be true on what is being touted as the ultimate daily driven race car. I sure haven't heard of such complaints on other cars with DBW, such as the M series from BMW.

01-14-2003, 02:05 PM	#3
Jeff_DML Amateur STI Driver Location: San Diego Posts: 14 Join Date: Jan 2003 Trader Rating: (0)	Our 3 series wagon has drive by wire and I can blip the throttle while breaking to heel-toe downshift with it. I assume the STi will be the same, it better be Jeff

01-14-2003, 04:42 PM	#4
Marine06 Junior STI Driver Car: WRC Fav Mod: Network Admin/Student Location: Southern California, USA Posts: 192 Join Date: Apr 2002 Trader Rating: (0)	It depends on how Subaru implements dbw. I was bummed when i read that it had this "feature." Personally, I don't think Subaru overlooked dbw in its implementation.

01-16-2003, 12:30 AM	#6
4MLA1FN hatin' ovals Car: 04 subaru wrx sti Location: alexandria, va Posts: 2,460 Join Date: Jun 2002 Trader Rating: (0)	fwiw here's the thread the prompted my question: http://forums.nasioc.com/forums/show...;highlight=dbw

01-16-2003, 07:51 AM	#7
thebigshow Junior STI Driver Car: Running 12's...for now Fav Mod: Subaru Supremacist Location: South Central PA Posts: 64 Join Date: Jan 2003 Trader Rating: (0)	could anyone b so kind as to givin me a crash course in rev matchin? thanks.

01-16-2003, 07:56 AM	#8
alfredob1 The Next Petter Solberg Car: 03 Evo VIII Fav Mod: Track days Location: Somewheres in CA Posts: 872 Join Date: Nov 2001 Trader Rating: (0)	My best explanation is when downshifting you giving it gas before engaging the clutch after shifting to the lower gear. The amount of gas you give should be sufficient enough to match the RPM's you were doing in the previous gear. That way the car doesn't lurch when you completely let out the clutch. If someone has a better explanation please share.

01-16-2003, 07:59 AM	#9
thebigshow Junior STI Driver Car: Running 12's...for now Fav Mod: Subaru Supremacist Location: South Central PA Posts: 64 Join Date: Jan 2003 Trader Rating: (0)	ok, i kinda thought that. now this is just what u do when u're slowin down, right? in that case, i just brake a little and let the clutch out slow. if u're referrin to downshiftin when u're passin or whatever, then that's something else entirely. thanks.

01-16-2003, 11:17 AM	#10
4MLA1FN hatin' ovals Car: 04 subaru wrx sti Location: alexandria, va Posts: 2,460 Join Date: Jun 2002 Trader Rating: (0)	as you note, heel-toe isn't really necessary is your coming to a stop. it's best for taking corners in a spirited manner. you can brake, shift smoothly into the gear you need to for getting out of the corner, and it also keeps the engine in the power band so you can jet after the apex. i definately rev-match when downshifting to accelerate past someone. when done right, the feeling of "instant" acceleration is awesome. on a road trip, i had a friend following me. at one point, to get around a slow car, i downshifted and accelerated. once we reached our destination, he said he was stunned how quickly my little se-r i pulled away because he didn't see the car dip/lurch the way it would when a normal downshift is done to accelerate. in general, rev-matching it much easier on the clutch disc since it minimizes slipping due to a rotational difference between the engine and the tranny. there is a thread about this in the "off-topic" forum: http://www.imprezawrxsti.com/postnuk...opic&t=805

01-17-2003, 07:45 AM	#12
BHODGES3 Professional STI Driver Fav Mod: Computer Programmer Posts: 438 Join Date: Jan 2003 Trader Rating: (0)	What is "granny shifting" and "double-clutching"?

01-17-2003, 05:18 PM	#13
Agent Chobos Grassroots STI Racer Location: Los Angeles, CA Posts: 542 Join Date: Apr 2002 Trader Rating: (0)	The way Mr. Quarter-Mile-at-a-Time used it, he meant "granny" shifting as just normal shifting: clutch in, shift, clutch out. Double-clutching is essentially clutch once to shift into neutral, clutch again to shift it into gear (while matching revs). The trick of course is to do it quickly. Why anyone would actually double-clutch during a DRAG race is beyond me, though. Likely just more movie BS, a la "Motec system exhaust".

01-21-2003, 06:54 AM	#14
BHODGES3 Professional STI Driver Fav Mod: Computer Programmer Posts: 438 Join Date: Jan 2003 Trader Rating: (0)	Why would you need to double clutch then? Wouldn't you just clutch, go into neutral, match rev's, shift, and then de-clutch? And for the life of me... has anyone heard of Mashimoto ZX tires? heh. My only thought is that they might be some kind of street-racing tire popular with the Japanese Import Crowd. Good call on the F & F question by the way.