DCT Rev Matching

[Rx7andy]

The new NSX promo video on the NSX site shows a scene where the driver blips the throttle and then double down shifts using the shift pedal going into a turn. I believe NSX specs show it already has rev matching. So is this something you do to help the rev matching when braking really hard? I tried but may be wasn't going fast enough in my F80.

Anyone has insight into this technique on a DCT car?

[jwzimm]

How would you do this? You would be in gear which means that if you attempted to rev match you would simply accelerate. You would have to put the transmission in neutral and then match revs and then put it back in gear. That all defeats the purpose of a DCT as the shift would be many times longer than what the DCT is capable of.

[Rx7andy]

Around 2:10 at

[CanAutM3]

I watched the video and it happens very fast. I think it is bogus marketing.

DCT rev matches automatically in Drivelogic setting 2 and 3 or when throttle is applied in setting 1. There is no need to blip the throttle.

Further, not sure why this is posted in the track section.

[afadeev]

Originally Posted by Rx7andy

The new NSX promo video on the NSX site shows a scene where the driver blips the throttle and then double down shifts using the shift pedal going into a turn. I believe NSX specs show it already has rev matching. So is this something you do to help the rev matching when braking really hard? I tried but may be wasn't going fast enough in my F80.
Anyone has insight into this technique on a DCT car?

F80 DCT has something very similar - you are breaking hard into a turn, downshift to the target gear (e.g: 1st while still doing 60+), and when the RPMs drop low enough to hit it safely, DCT engages the target gear. I use it all the time during autoXs.

NSX, supposedly, will have 9-speed DCT.
AWD, ICE+EV hybrid, with 570+ HP.

More of a GTR super-car performance category, than M3's.
http://www.caranddriver.com/acura/nsx

Should be an awesome $155K coupe!

a

[Rx7andy]

Originally Posted by CanAutM3

I watched the video and it happens very fast. I think it is bogus marketing.

DCT rev matches automatically in Drivelogic setting 2 and 3 or when throttle is applied in setting 1. There is no need to blip the throttle.

Further, not sure why this is posted in the track section.

I thought it was some kind of driving technique.

[neo871]

Originally Posted by CanAutM3

I watched the video and it happens very fast. I think it is bogus marketing.

DCT rev matches automatically in Drivelogic setting 2 and 3 or when throttle is applied in setting 1. There is no need to blip the throttle.

Further, not sure why this is posted in the track section.

What do you do you mean by "it rev matches in dct settings 1 when you apply the throttle"? I mean how does it behave differently
than in setting 2 & 3? I haven't noticed anything in this respect.

[CanAutM3]

Originally Posted by neo871

What do you do you mean by "it rev matches in dct settings 1 when you apply the throttle"? I mean how does it behave differently
than in setting 2 & 3? I haven't noticed anything in this respect.

Downshifting in DriveLogic setting 2 or 3, DCT will open the engaged clutch, blip the throttle to match the revs and engage the appropriate clutch.

In setting 1, downshifting while you are off the throttle, DCT will do a slow downshift slipping from one clutch to the other without rev matching. This is different from settings 2 and 3. However, if you downshift while on the the throttle in settings 1, DCT will in most conditions do a rev match just like in DriveLogic 2 or 3.

[neo871]

Went for a quick drive and it pretty much acts as you say. I am not used to dct setting 1 since I mostly drive on 2.
Setting 3 is way to aggressive even for track use. Actually is quite inefficient on the track.
Setting 2 is the finest

[CanAutM3]

Originally Posted by neo871

Went for a quick drive and it pretty much acts as you say. I am not used to dct setting 1 since I mostly drive on 2.

Originally Posted by neo871

Setting 3 is way to aggressive even for track use. Actually is quite inefficient on the track.

I actually quite like S3 on the track for the crisp upshifts and immediate downshifts. Do you track with DSC or MDM on?. If so, I can understand why you dislike S3, the power upshifts are so sharp in S3 that they almost always get DSC to cut the power, which is quite annoying. S3 can only be really appreciated with DSC off.

[neo871]

I track with MDM on. The reason I dislike the S3 on track is that I feel it makes the car slide outward a little when I am on wot at turn exist. Sometimes you need to change gears begore the steering wheel is fully centered and I felt the S3 upsets the balance in this situations.

[afadeev]

Originally Posted by neo871

I track with MDM on.

Than that's the root cause of your problems

Originally Posted by neo871

The reason I dislike the S3 on track is that I feel it makes the car slide outward a little when I am on wot at turn exist. Sometimes you need to change gears begore the steering wheel is fully centered and I felt the S3 upsets the balance in this situations.

I haven't noticed that at all.
Then again, I always default to S3 and DSC full OFF on track. With DCT, both up- and down-shifts are absolute non-events in S3.
With MDM ON, I can see how sharp upshift could trigger MDM intervention, unsettling the car.

The first session on a new track I am usually with MDM ON to learn the line. That produces unpredictable under-steer on turn entry, and inability to rotate the rear and put the power down through the turn and turn exit. The more speed you build up, the more unpredictable the interventions seam to become. With either MDM or DSC, you are learning to drive around the limits and peculiarities of traction control programming, not the limits of your abilities, or the car's.

Originally Posted by CanAutM3

S3 can only be really appreciated with DSC off.

Amen to that.

a

[///Machiavelli]

Originally Posted by neo871

I track with MDM on. The reason I dislike the S3 on track is that I feel it makes the car slide outward a little when I am on wot at turn exist. Sometimes you need to change gears begore the steering wheel is fully centered and I felt the S3 upsets the balance in this situations.

Full disclosure: I haven't ever tracked with this platform so I don't have any experience with the gearing

But shifting in a turn is not desirable. As smooth as the dct is, obviously it is still upsetting the balance of the car in your situation. So, maybe you could stay in a higher gear and use the massive torque available at low rpm's to accelerate out of the apex and that way avoid running out gear before finishing the turn?

[neo871]

Originally Posted by afadeev

Than that's the root cause of your problems

I haven't noticed that at all.
Then again, I always default to S3 and DSC full OFF on track. With DCT, both up- and down-shifts are absolute non-events in S3.
With MDM ON, I can see how sharp upshift could trigger MDM intervention, unsettling the car.

The first session on a new track I am usually with MDM ON to learn the line. That produces unpredictable under-steer on turn entry, and inability to rotate the rear and put the power down through the turn and turn exit. The more speed you build up, the more unpredictable the interventions seam to become. With either MDM or DSC, you are learning to drive around the limits and peculiarities of traction control programming, not the limits of your abilities, or the car's.

Amen to that.

a

I don't have enough experience on a track to go with DSC off, so, for the moment, I can't agree, nor disagree with the "DSC-off-is-best theory". I have euro MDM and I feel that it's permissive enough. I think some people are are underestimating. Of course, real racing entails zero nannies, but I am only a track day enthusiast. As others have said, there is no point in risking that much. And honestly, I am getting some pretty good times with MDM, but I still have a lot of techniques to work on.

The S3 transmission shock I am talking about is upsetting the car, but not THAT much to have the MDM to kick in.

Originally Posted by ///Machiavelli

But shifting in a turn is not desirable. As smooth as the dct is, obviously it is still upsetting the balance of the car in your situation. So, maybe you could stay in a higher gear and use the massive torque available at low rpm's to accelerate out of the apex and that way avoid running out gear before finishing the turn?

You may be right. I will further analyze this next season

[CanAutM3]

Originally Posted by ///Machiavelli

Full disclosure: I haven't ever tracked with this platform so I don't have any experience with the gearing

But shifting in a turn is not desirable. As smooth as the dct is, obviously it is still upsetting the balance of the car in your situation. So, maybe you could stay in a higher gear and use the massive torque available at low rpm's to accelerate out of the apex and that way avoid running out gear before finishing the turn?

Having the ability to shift mid turn is one of the great benefits of DCT. Through the various sensors, the ECU are smart enough to detect when the car is under lateral load and the DCT will execute a butter smooth shift by progressively slipping one clutch on the other.

I have been so conditioned of avoiding shifting mid corner when I was driving MT cars, that it took a lot of self convincing for me to pull that paddle mid turn on my previous E92. Once I did though, I was amazed on how seamless the shift was. And I have used that benefit of DCT ever since.

That being said, with power/torque curve of the S55, it is a bit trickier. On the E9X, upshifting always resulted in less torque at the wheels. With the F8X, it is not necessarily the case, where you get at least as much torque at the wheel in the higher gear and sometimes more. However, once aware of that quirk, nothing prevents upshifting mid-turn with a DCT F8X .

Your point about leveraging the torque remains valid though. I often tell students that if they cannot be WOT going through a turn in the higher gear, there is zero benefit of being in that lower gear.

[aboulfad]

Originally Posted by CanAutM3

Downshifting in DriveLogic setting 2 or 3, DCT will open the engaged clutch, blip the throttle to match the revs and engage the appropriate clutch.

In setting 1, downshifting while you are off the throttle, DCT will do a slow downshift slipping from one clutch to the other without rev matching. This is different from settings 2 and 3. However, if you downshift while on the the throttle in settings 1, DCT will in most conditions do a rev match just like in DriveLogic 2 or 3.

very interesting ! I downshift (S mode) with throttle on all the time, so that means the DCT will rev match in any drivelogic level in my case. But what does it do when driving in "D" mode, aka "automatic" mode, is it the same behavior or it rev matches throughout all the drivelogic levels regardless of throttle position ?

[CanAutM3]

Originally Posted by aboulfad

very interesting ! I downshift (S mode) with throttle on all the time

Really ?

What do you do when approaching a turn?

Originally Posted by aboulfad

But what does it do when driving in "D" mode, aka "automatic" mode, is it the same behavior or it rev matches throughout all the drivelogic levels regardless of throttle position ?

I don't have much experience with D2 and D3 as I usually us S-mode for spirited driving and only use D1 in Stop-and-Go traffic. But my limited experience tends to indicate the behavior is the same in S1 vs D1 and S2/3 vs D2/3. It barely ever rev matches in D1 when not on throttle.

[aboulfad]

Originally Posted by CanAutM3

Really ?
What do you do when approaching a turn?

My comments were for normal day to day driving not track! So it depends what i want to do, lets say i am approaching slowly a curve and i want to accelerate (for fun?), in order to pick up more speed, i would downshift but my foot is still on the throttle. I don't let off the throttle momentarily as in a MT during the gear shift. Is that bad ?

I didn't mean that i keep my foot planted on the throttle in all scenarios ALL times during downshifts.

But back to the point at hand, i was more curious about the DCT behavior in D mode, as i drive very often in traffic in D1, and if the DCT doesnt rev match on downshift (throttle off) and it slips the clutch, that's no good. Especially in stop and go traffic, where often you are in 2nd gear, and as the car is slowing down to stop, it downshifts to first ...

So conclusion: for stop and go traffic, wouldn't it be better to be on Drivelogic 2, so we benefit from rev matching ?

[aboulfad]

Ok took two videos, by the look of it, DCT does revmatch even with throttle off. The rpm needle is quite noticeable in D2 when it rematches on downshift, but less so in D1, but nonetheless it seems it does.
UPDATE: in first level of drivelogic, there is no revmatch, what i saw in the video was that the rpm went higher due to lower gear. You have to hear the blip.

Drive logic D1, here I show only when the car is decelerating and downshifting:
Drive Logic D2: here I accelerate then let the car decelerate and downshift

[CanAutM3]

Originally Posted by aboulfad

Ok took two videos, by the look of it, DCT does revmatch even with throttle off. The rpm needle is quite noticeable in D2 when it rematches on downshift, but less so in D1, but nonetheless it seems it does.

Drive logic D1, here I show only when the car is decelerating and downshifting:

Drive Logic D2: here I accelerate then let the car decelerate and downshift:

I am not sure you can conclude that it rev-matches in D1 from that video. From my driving impressions, mostly based on engine sound and perceived deceleration, I am pretty sure it does not rev match off-throttle in D1.

On a rev-matched downshift, you will have a slight pause in deceleration while both clutches are disengaged and the throttle is blipped. On a non-rev-matched downshift, you will feel a slight momentary increase in deceleration as the vehicle's forward momentum is used to increase the engine revs. I guess it is more difficult to perceive in D1, because the transmission will only downshift off throttle at very low revs. But try it in S1 and S2 where you can induce an off-throttle downshift at higher revs. You will be able to better feel what I describe above.

[CanAutM3]

Originally Posted by aboulfad

My comments were for normal day to day driving not track! So it depends what i want to do, lets say i am approaching slowly a curve and i want to accelerate (for fun?), in order to pick up more speed, i would downshift but my foot is still on the throttle. I don't let off the throttle momentarily as in a MT during the gear shift. Is that bad ?

I didn't mean that i keep my foot planted on the throttle in all scenarios ALL times during downshifts.

But back to the point at hand, i was more curious about the DCT behavior in D mode, as i drive very often in traffic in D1, and if the DCT doesnt rev match on downshift (throttle off) and it slips the clutch, that's no good. Especially in stop and go traffic, where often you are in 2nd gear, and as the car is slowing down to stop, it downshifts to first ...

So conclusion: for stop and go traffic, wouldn't it be better to be on Drivelogic 2, so we benefit from rev matching ?

Even on the daily drive, I always downshift before entering a turn to be in the right gear coming out. The downshift should be done while decelerating, so one is either coasting or braking at that point which implies being off throttle.

Bear in mind that the clutch slip in minimal in such downshifts and is done with very little load (the rear wheels accelerating the engine). That is nothing compared to a WOT upshift at redline. Further, bear in mind that those are wet clutches and a portion of the slip is taken by the shear forces in the fluid. The transmission is designed and programmed for that, wear on such downshifts should not be a concern.

[aboulfad]

CanAutM3 I was nicely sitting comfy in my sofa as I read your posts above, my head hurt, so I got up and drove. Pretty cool when you feel and hear the difference. In the first level of drive logic, there is no blip, just that the rpm's are higher in the lower gear which confused me in the first vid as I couldn't hear it. In the second level of drive logic, you hear the blip. I did also notice some difference regarding the deceleration but it was too subtle for me to understand. Thanks