i agree... if you're rev matching it correctly and then gassing it (exiting turn).. you shouldn't be engine braking...

 

It came out the wrong way. I didnt mean for it to sound like you should only blip the throttle to use the engine to brake or slow down, that is completely wrong. I meant more so in terms of when you perform the ''heel-toe'' that the engine helps slow you down while you are down shifting and braking into a corner. I am not saying you should rely on the engine to brake, i am merely saying that would help while you are braking and if you do it correctly there are no pitch or rolls and you would be able to stay in gear while gassing it through the corner and out.

 

Does anyone know if this event will take place everyday of SEMA (Tues. - Fri.) & hours each day?

 

It's only Tuesday through Thursday, 9-5.

Javier

 

Where did you get this info? Autolies, err I mean Autospies said Tues - Thurs only but they just showed the main website (listed earlier) as their source. I couldn't find any info on there. The reason I'm asking is b/c I am trying to see if I can take off on Friday so I can go to SEMA on Friday & also test drive the IS-F (assuming test drives are available Friday).

 

I'm registered and confirmed for a test drive... Thursday is the last day.

Javier

 

Thx for the info!

 

Exactly it is like double clutch shift on a manual, a lost art in a world where manuals are like hens teeth. On a manual box, it is a synchronizer saver, double clutch properly and you can extend the life of synchros tremendously. On an true automatic I think it is all about stability and control.

 

Exactly. Double clutching was used in early cars that did not come with synchros. The synchros essentially match the ground speed to the engine speed while downshifting. So that there is no need to double clutch.

Without going into details, rev-matching and double clutching however are related, but different things.

The question must be, if synchros do the rev matching, why rev-match (or better yet, heal-toe downshift in corners)?

Simple answer is that synchros are not very strong and have to work extremely hard to match the speed of the engine to the ground speed of the car and they cannot match speed as fast as the clutch can be released (that is why a jerk will be felt while releasing the clutch suddenly without rev-matching).

Hence, it is important to rev match while downshifting in order to extend the life of the synchros and transmission as well as making sure the downshift is fluid and smooth.

 

1. Synchros do nothing of the sort. They only brake the gear to the speed of the shaft it is spinning on. It could be the input shaft, the output shaft, or the countershaft depending on the gearbox design. It is only remotely related to road speed.

2. Synchos have nothing at all to do with the jerk felt while releasing the clutch. The reason for the jerk is the engine flywheel and clutch pressure plate are spinning at a different speed than the friction disc on the transmission's input shaft. If the synchros are not doing their job, you hear a grinding sound from the gearbox, you don't feel a jerk when releasing the clutch.

3. Double clutching or rev matching to save synchros is hogwash. They're going to do what they do regardless of your clutching technique. Again - rev matching is ONLY to prevent upsetting the chassis on downshift - not to save one single part in the gearbox.

It's pretty obvious there is a serious misunderstanding of how a modern constant mesh fully synchronized gearbox works. Suffice it to say, the synchros have one purpose in life - to apply a braking force to the selected gear so the gear which is free spinning on a shaft can match its rotational speed to the shaft's rotational speed and allow the teeth on the synchro hub's outer ring to engage the dogs on the selected gear without grinding.

I just gave a live demonstration of this whole process with the synchro hubs, synchros, and gears I removed and replaced in my Getrag 233 (Toyota V-160) for a friend of mine this weekend. It's not complicated, but its not entirely intuitive either.

 

^^^^

Hmmm..thanks for clarifying. I read in an article, if you don't rev-match when you downshift, the synchro life will be shortened greatly. Guess it may not be true.

 

If you want to shorten synchro life quickly, downshift into first at 15 or 20 mph. There is nothing you can do that is more stressful to your first gear synchro.

 

Or shift without using the clutch.

 

Even if someone wanted to do it, he would not (without double-clutching) since the first gear gets locked out once the speed exceeds approx. 5 mph.

 

My old 5spd Manual Solara SE V6 had a lockout of first gear while in motion. I believe it was 5mph.

Speaking of the IS-F trans shift...it is VERY quick. So quick it impressed the pro-drivers that were tossing us around in it.