[4MLA1FN]

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]

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]

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]

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]

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.

 

[4MLA1FN]

fwiw here's the thread the prompted my question:

http://forums.nasioc.com/forums/showthread.php?s=&threadid=298918&highlight=dbw

 

[thebigshow]

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

 

[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.

 

[thebigshow]

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]

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/postnuke/modules.php?op=modload&name=phpBB2&file=viewtopic&t=805

 

[Agent Chobos]

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]

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

 

[Agent Chobos]

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]

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]

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.

 

[new_sti_lvr]

Ever driven a manual trans without synchro's? SM465 is an old cast GM transmission used in their 3/4 and 1 ton trucks during the 70's mostly (although used before and after for a bit as well). In any event, double clutching is a way of life with those, its certainly easier on todays synchro's as well because there work is for the most part elminiated. Driving an SM465 and not having the gears grind between 2nd and 3rd (there's 4 gears, but the first is a granny that you never use unless offroad) is a challenge. Give it a try sometime, its certainly an experience compared with the wonderful transmissions we have now a days. I've got an old '78 1 ton to play around in and pull the car trailer.

 

[pgetchell]

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.

that is what I have heard, you really do not need to, you can simply match the revs and let the synchros do the trick. makes it quicker than the clutch-neutral-unclutch-rev-clutch...or whatever.

But, on the other hand, double clutching may theoretically be easier on the tranny's innards.

 

[SnowbordrWRX]

I split off the F&F idiocies discussion into Off-Topic if you were looking for it. Splits oughta have shadows...

 

[Goose]

As stated, double clutching is essential when the synchro is crap or not there at all... I drove a escort cosworth in Ireland that had the worst synchro I've ever seen... (What do you expect from a ford) You couldn't down gear without double clutching...

 

[CloNeGTS]

Double clutching IS essential in some cars, but it does serve a very real purpose in today's cars as well.

Now, this doesn't mean you need to double clutch going UP the gears as stated in FnF and in that damn RSX-S commercial. All that does is make lots of cool engine noise.

Down shifting is a different story. You save your synchros a great deal of wear by double clutching. This isn't the same as rev matching. Double clutching gets all of the gears in the transmission up to speed so that when you do rev match as you shift into gear, everything meshes perfectly. Otherwise, the synchro is responsible for spinning up your entire transmission (not just the gear you are going into).

This pic should help.

If you are in gear, with the clutch disengaged, all of the gears in the transmission are spinning at the speed of the wheels. This is why you can't get into reverse cleanly when rolling. With the clutch disengaged and not in gear, the gears are free to spin down. If you are out of gear with the clutch engaged, the gears will spin at the speed of the engine. This is where double clutching is great. Spin those gears up, get back into the right gear without using the synchro, and then match the engine to the tranny's speed.

Ahhh.....there is nothing like a perfectly executed double clutch downshift.

Oh yeah, and when you are good at it, it doesn't take but an instant longer...but you should be slowing down if you are down shifting anyway, so why does it matter? You can keep braking.