08-29-2014, 08:53 AM
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#1
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Registered User
Join Date: May 2008
Location: Newport, KY
Posts: 202
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Downshifting
After reading a blog on another site about downshifting I am a little confused. I fully admit I have never raced nor am a I mechanic, but have driven manual shift vehicles nearly my entire 42 years of driving.
The blogger made the statement, and several other posters agreed, that you should never blip the throttle to rev match when downshifting with the clutch disengaged (pedal to the floor) because it will cause premature wear and damage to the throw out bearing. My question is, "Isn't that exactly what you do when you heel toe?" The left foot pushes the clutch pedal to the floor while the right foot depresses the brake and rolls over to blip the throttle.
So, what it the difference? Why would heel toe not hurt the TOB But downshifting by simply rev matching (in situations where you want to keep the rpms up but are not necessarily braking (up hills, off ramps, turning corners) cause damage?
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Greg
2002 Triple Black, Desnorkled, Bumper Plugs, LN IMSB Upgrade
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08-29-2014, 12:03 PM
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#2
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Registered User
Join Date: May 2011
Location: Miami florida
Posts: 1,591
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They are wrong. In a double clutch heel and toe downshift, which is what I think they are talking about, you put the clutch in, shift to neutral, let the clutch out and with the clutch out, blip the throttle to rev match and then quickly put the clutch back in and downshift.
This is the preferred way to downshift as it puts the least amount of strain on the synchros and leads to maximum gear box life. (Its actually the only way to shift old Alfa Romeos because the synchros come worn from the factory and if you don't double clutch, it will just grind and not go into gear). I suppose with the clutch out there is less wear on the TOB, but I would guess the difference is minimal. What double clutching does is save the gear box, primarily.
On our cars, the synchros are so robust that double clutching is almost overkill, but rev matching definitely helps preserve the gear box and really cuts down on clutch wear.
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Current car
2000 Boxster 2.7l red/black
Previous cars
1973 Opel Manta
1969(?) Fiat 850 Convertible
1979 Lancia Beta Coupe
1981 Alfa Romeo GTV 6
1985 Alfa Romeo Graduate
1985 Porsche 944
1989 Porsche 944
1981 Triumph TR7
1989 (?) Alfa Romeo Milano
1993 Saab 9000
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08-29-2014, 12:16 PM
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#3
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Registered User
Join Date: Jul 2014
Location: Tacoma
Posts: 429
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08-29-2014, 01:00 PM
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#4
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Registered User
Join Date: May 2008
Location: Toronto
Posts: 2,656
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Bloggers.
:troll:
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08-29-2014, 02:48 PM
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#5
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Certified Boxster Addict
Join Date: Nov 2010
Location: Los Angeles
Posts: 7,669
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Quote:
Originally Posted by san rensho
They are wrong. In a double clutch heel and toe downshift, which is what I think they are talking about, you put the clutch in, shift to neutral, let the clutch out and with the clutch out, blip the throttle to rev match and then quickly put the clutch back in and downshift.
This is the preferred way to downshift as it puts the least amount of strain on the synchros and leads to maximum gear box life. (Its actually the only way to shift old Alfa Romeos because the synchros come worn from the factory and if you don't double clutch, it will just grind and not go into gear). I suppose with the clutch out there is less wear on the TOB, but I would guess the difference is minimal. What double clutching does is save the gear box, primarily.
On our cars, the synchros are so robust that double clutching is almost overkill, but rev matching definitely helps preserve the gear box and really cuts down on clutch wear.
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+1 ^^ What he said. ^^
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08-29-2014, 05:51 PM
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#6
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Rennzenn
Join Date: Feb 2005
Location: Virginia
Posts: 1,369
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Thank you, Flaps10.
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Rennzenn
Jfro@rennzenn.com
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08-29-2014, 06:49 PM
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#7
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Registered User
Join Date: Apr 2014
Location: new orleans
Posts: 249
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san rancho got that right. alfa gearboxes love to get scratchy quickly if you are not cautious. generally from 1st to 2nd within 20k without double clutching.
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2005 Porsche Boxster S, 2000 Porsche Boxster 2.7L Base, 2000 Mazda Miata LS Supercharged, 2010 Toyota Tacoma TRD Off Road
Previous Vehicles: 2005 Ford Mustang GT, 1986 Alfa Romeo Spider, 1971 Alfa Romeo GTV, 1999 Ford Mustang
1977 Toyota Celica GT
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08-30-2014, 07:00 AM
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#8
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Registered User
Join Date: Aug 2014
Location: Toronto, Ontario. Canada
Posts: 73
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Double clutching is different than heel and toe.
The confusion around all this is rampant.
Here's by far the best video to slowly and articulately explain it all:
http://m.youtube.com/watch?v=X3288FKOe_M
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08-30-2014, 08:00 AM
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#9
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Registered User
Join Date: May 2011
Location: Miami florida
Posts: 1,591
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Quote:
Originally Posted by Jim Rockford
Double clutching is different than heel and toe.
The confusion around all this is rampant.
Here's by far the best video to slowly and articulately explain it all:
http://m.youtube.com/watch?v=X3288FKOe_M
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The difference is really pretty easy. Heel and toe is what you do if you brake while rev matching while downshifting.
__________________
Current car
2000 Boxster 2.7l red/black
Previous cars
1973 Opel Manta
1969(?) Fiat 850 Convertible
1979 Lancia Beta Coupe
1981 Alfa Romeo GTV 6
1985 Alfa Romeo Graduate
1985 Porsche 944
1989 Porsche 944
1981 Triumph TR7
1989 (?) Alfa Romeo Milano
1993 Saab 9000
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09-03-2014, 08:36 AM
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#10
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Registered User
Join Date: Apr 2008
Location: Southern New jersey
Posts: 1,054
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I have rev-matched both ways, double-clutching, or with a single clutch movement. I call it a pseudo double-clutch downshift, you just don't let it out in neutral.
It won't matter as far as the throwout bearing, it will be accelerated to the same RPM in either case. It may have more pressure on it while single-clutching, but that's what they're built do do....
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09-03-2014, 11:01 AM
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#11
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Registered User
Join Date: Aug 2009
Posts: 1,466
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2003 Black 986. modified for Advanced level HPDE and open track days.
* 3.6L LN block, 06 heads, Carrillo H rods, IDP with 987 intake, Oil mods, LN IMS. * Spec II Clutch, 3.2L S Spec P-P FW. * D2 shocks, GT3 arms & and links, Spacers front and rear * Weight reduced, No carpet, AC deleted, Remote PS pump, PS pump deleted. Recaro Pole position seats, Brey crouse ext. 5 point harness, NHP sport exhaust
Last edited by jsceash; 09-03-2014 at 11:09 AM.
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09-03-2014, 11:23 AM
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#12
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Registered User
Join Date: Jun 2012
Location: Peoria IL
Posts: 529
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Clutches are for sissies. Just rev it slightly to pop it out of gear, then rev it a bit more and slide the shifter down a gear.
P.S. Does anybody know of a place where I can buy new synchros?
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09-03-2014, 02:04 PM
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#13
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On the slippery slope
Join Date: Mar 2014
Location: Austin and Palm Springs
Posts: 3,797
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Quote:
Originally Posted by CoBeerToad
Clutches are for sissies. Just rev it slightly to pop it out of gear, then rev it a bit more and slide the shifter down a gear.
P.S. Does anybody know of a place where I can buy new synchros? 
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We don't need no stinkin clutch!
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2004 Boxster S 6 speed - DRL relay hack, Polaris AutoTop DIY
2004 996 Targa Tip
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2014 Porsche Performance Driving School
2020 BMW X3, 2013 Ram 1500, 2016 Cmax, 2004 F-150 "Big Red"
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09-03-2014, 03:02 PM
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#14
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Registered User
Join Date: May 2011
Location: Miami florida
Posts: 1,591
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Quote:
Originally Posted by jsceash
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Because they are not double clutching since the gear boxes have synchros, just like our cars. You don't have to double clutch, its just the technique for downshifting that puts the least wear on the synchros and gear box.
Heres a" from the testicles point of view" video of double clutching alternating between just a straight double downshift to a heal and toe double clutch.
https://www.youtube.com/watch?v=Vw-MewZRsAM
__________________
Current car
2000 Boxster 2.7l red/black
Previous cars
1973 Opel Manta
1969(?) Fiat 850 Convertible
1979 Lancia Beta Coupe
1981 Alfa Romeo GTV 6
1985 Alfa Romeo Graduate
1985 Porsche 944
1989 Porsche 944
1981 Triumph TR7
1989 (?) Alfa Romeo Milano
1993 Saab 9000
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09-03-2014, 03:46 PM
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#15
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Registered User
Join Date: Oct 2007
Location: Midwest
Posts: 1,746
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Quote:
Originally Posted by flaps10
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I'll bet I've watched that video 100 times, 23 seconds is pure sex. He's a bit heavy on the throttle for rev matching but it honestly MADE the video lol.
Greg, regarding your driving, your method is exactly how I've been driving for 35 years. I use to do the double clutching thing occasionally to amuse myself, too much work. Besides, our method is the lazy way to impress the uninitiated.........
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09-03-2014, 07:00 PM
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#16
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Certified Boxster Addict
Join Date: Nov 2010
Location: Los Angeles
Posts: 7,669
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Quote:
Originally Posted by jsceash
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This makes me really want a sequential gearbox!
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1999 996 C2 - sold - bought back - sold for more
1997 Spec Boxster BSR #254
1979 911 SC
POC Licensed DE/TT Instructor
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11-15-2019, 05:38 PM
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#17
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Registered User
Join Date: Sep 2009
Location: toronto
Posts: 2,668
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Quote:
Originally Posted by thstone
+1 ^^ What he said. ^^
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Do any double de-clutch down shift on the track to save wear? Never did this on track myself but do do it in my Jeep all the time
How about double clutching on up shifts for second to third....which can really notchy when things get hot?
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986 00S
Last edited by jaykay; 11-15-2019 at 05:46 PM.
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11-19-2019, 04:25 PM
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#18
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Registered User
Join Date: Jan 2014
Location: New Jersey
Posts: 1,631
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Transmission internals are beyond my full comprehension, but if you don't double clutch, will the throttle blip spin the gears to make the rev match as you downshift? In other words, does blipping the throttle with the clutch pedal to the floor make any of the transmission gears spin? It seems to me that anything going on in the transmission in this instance is coming from the differential and driveshaft in a non-transaxle car.
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Current: 2022 718 Cayman GT4, PDK bone stock (the dark side).
Former: 2003 S, 3.6 LN Nickies, ARP rod bolts, under-drive pulley, Fabspeed sport headers, Softronic tune, 987 airbox 987 motor mount, Function-First Sport motor mount insert, Ben's short shifter, Nine8Six projector headlights & center caps, ROW M030, stainless flexible brake lines, B-K rollbar extension & fire extinguisher mount, hardtop
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11-19-2019, 07:29 PM
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#19
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Registered User
Join Date: Feb 2017
Location: NY
Posts: 32
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Quote:
Originally Posted by PaulE
Transmission internals are beyond my full comprehension, but if you don't double clutch, will the throttle blip spin the gears to make the rev match as you downshift? In other words, does blipping the throttle with the clutch pedal to the floor make any of the transmission gears spin? It seems to me that anything going on in the transmission in this instance is coming from the differential and driveshaft in a non-transaxle car.
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When down shifting, the engine RPM is actually slower than it will be when you engage the lower gear. The blip will speed up the engine before the clutch engages so the car doesn't abruptly slow as the clutch is let out. Smoothes out the downshift and doesn't upset the balance of the car.
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11-20-2019, 04:47 AM
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#20
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Registered User
Join Date: Jan 2014
Location: New Jersey
Posts: 1,631
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Quote:
Originally Posted by lmnsblu355
When down shifting, the engine RPM is actually slower than it will be when you engage the lower gear. The blip will speed up the engine before the clutch engages so the car doesn't abruptly slow as the clutch is let out. Smoothes out the downshift and doesn't upset the balance of the car.
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Ok thanks. So if we don’t double clutch we’re just getting the engine speed up to smooth the downshift, not getting the lower gear spinning faster to match the engine speed, we’re letting the synchros do that work. I learned to drive a manual in a 1960 Austin Healey Sprite with questionable synchros on second through fourth and an unsynchronized first gear, so I still double clutch when down shifting.
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Current: 2022 718 Cayman GT4, PDK bone stock (the dark side).
Former: 2003 S, 3.6 LN Nickies, ARP rod bolts, under-drive pulley, Fabspeed sport headers, Softronic tune, 987 airbox 987 motor mount, Function-First Sport motor mount insert, Ben's short shifter, Nine8Six projector headlights & center caps, ROW M030, stainless flexible brake lines, B-K rollbar extension & fire extinguisher mount, hardtop
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