gmathews

I don't recall your prior post in particular, but I suspect, in a third to second shift, the events as you do them are as follows: clutch in, shifter moved from third all the way to second, REV HERE, clutch out.

While the drivetrain is separated from the engine flywheel (clutch in) blipping the throttle will raise engine speed, and if raised to the correct speed to match the rest of the driveline, then nearly all of the weight transfer issue (I think) can be mitigated. So, what is the difference? I was taught that true "double clutching" differs in that by re-engaging the clutch while in neutral, and then revving, the pressure plate and clutch also rev up in connection with the engine. With a clutch in and rev situation, the clutch disc and pressure plate are disconnected from the driveline and disconnected from the engine. So, the disc and pressure plate (once clutch pedal is pressed in) is kinda at driveline speed but slowing down a bit since it "got disconnected" from the driveline when the clutch pedal was pressed.

Getting into territory that I really am not as sure about at this point, and this is my reason for my comment about "I've got some more experimenting to do". I'm willing to learn if that is what is needed. However, in the past, it was more than important to reconnect the clutch disc and flywheel to the engine before blipping, but maybe "things have changed". Perhaps the weight of the disc and pressure plate is far lighter on this car than "older cars".

Please do share when you get a chance Chris88. I just know I've got some reading and some experimenting to do.

gmathews

Alright. I was ignorant, and now I am less so. It seems that I have been doing more than necessary with my shifting. I will be adjusting my shifting technique going forward so that a "double clutch" is no longer part of the mix. The good news is that the new way is easier. If I ever drive a car that doesn't have full synchromesh, I likely will be able to do heal and toe (with double clutching) - so, I have skills!

Also, a correction to some of the above about drivetrain connection between engine, clutch, and the rest of the driveline. The flywheel and pressure plate are bolted to the engine, so both of those increase in conjunction with the engine when the throttle is blipped. The only parts of the clutch assembly that do not are the disc and throw out bearing. So, I am getting nothing beneficial by double clutching the GT3 that I can't get just by blipping the throttle with the clutch in. As mentioned in other posts, I just will need to time the blip to happen after I have selected the lower gear so that I don't run into issues with the electronics thwarting the throttle blip.

This was one of several videos that I found to be helpful while researching. There were others on 4.0 6 speed street cars (one with Hurley Haywood) which showed the same shift technique as in this video.

iphilips

Why were people double clutching to begin with? I don't understand the need for this in a modern manual gearbox?

gmathews

My first cars were old Datsun 510's and 240z's, which actually do have transmissions with full synchromesh (except reverse), however, they were old even when I started driving them. Typically, the second gear synchros in those cars (or for any that are still running around) have moderate to a lot of wear. Double clutching can still be of value when down shifting in cars with full synchromesh if the synchros have a lot of wear (mainly 2nd or 1st). It would be more applicable in an autocross or similar type of competitive event vs. street driving.

Inherently in the double clutching process, there is also a rev match via throttle. That is how I learned the process to rev match to avoid destabilizing any car during a down shift. I first learned of the concept of double clutching from reading a car magazine in the 80's. So, likely the audience included drivers of cars without full synchromesh gearboxes at that time.

In all my cars up to the GT3, there were never any negative consequences to performing double clutch down shifts, so I never found the need to revisit my knowledge on the subject. So... now I have.

RudyP

Due to worn synchros, my 993 requires double clutching on the first 1-> 2 shift of the day. After it warms up, it’s fine but I still don’t rush that shift.

iphilips

Thanks for the context, I learnt to drive in the 90s so I learnt the single clutching method but did teach myself to double clutch just for fun but, I've never double clutched in anger. I could see why that would be problematic (but not required) in the GT3.