Lightweight flywheels and SyncroRev Match

juld0zer · 11-10-2013, 06:44 PM

Quote:

Originally Posted by RCZ

I think I remember hearing in the Nissan videos that the car uses throttle position, sensors in the shifter and speed and G sensors to calculate the optimal RPM. I think it just blips the throttle and gets it to a predetermined RPM (as a function of data from the sensors) rather than taking the weight of the flywheel into account. If I'm right, a lighter flywheel would mean even quicker rev matches. If you think about it from Nissan's point of view, its much easier to calculate the necessary RPM's and then just say "100% throttle until you reach that RPM, then hold and revise every millisecond using data from the sensors"

Thread revival!

You're pretty much on the mark.
Here are the sensors that make it happen:
1- Clutch pedal sensor (the same one that allows you to start the car, ie. detect pedal is fully depressed)
2- Crank angle sensor (on the bell housing)
3- Neutral position sensor/gear lever position sensor
4- Input speed sensor (on the rear left hand side of the gearbox. Not far from the reverse sensor)
5- rear wheel speed sensors (on the diff). This one i'm not 100% sure about as #4 should suffice for smooth shifting.

1 tells the system to wake up
3 tells the system what gear you are currently in & what gear you are entering
4 tells the system how fast the (output i think) shaft in the gearbox is rotating. Automatic gearboxes use an input speed sensor for the same purpose - to enable smooth shifting.
2 is obvious - i tells the system what RPM the engine is rotating at and the system calculates the target engine speed based on the signal from #4 and #3.

Since the ECU can respond to throttle inputs that quickly, i'd assume if you swapped in a lightweight flywheel and lightweight underdrive pulley, the system would not overrev the engine. It will back off once the target RPM is reached.

PS. I'm not an expert.

takjak2 · 11-11-2013, 07:23 PM

Quote:

Originally Posted by juld0zer

Thread revival!

You're pretty much on the mark.
Here are the sensors that make it happen:
1- Clutch pedal sensor (the same one that allows you to start the car, ie. detect pedal is fully depressed)
2- Crank angle sensor (on the bell housing)
3- Neutral position sensor/gear lever position sensor
4- Input speed sensor (on the rear left hand side of the gearbox. Not far from the reverse sensor)
5- rear wheel speed sensors (on the diff). This one i'm not 100% sure about as #4 should suffice for smooth shifting.

1 tells the system to wake up
3 tells the system what gear you are currently in & what gear you are entering
4 tells the system how fast the (output i think) shaft in the gearbox is rotating. Automatic gearboxes use an input speed sensor for the same purpose - to enable smooth shifting.
2 is obvious - i tells the system what RPM the engine is rotating at and the system calculates the target engine speed based on the signal from #4 and #3.

Since the ECU can respond to throttle inputs that quickly, i'd assume if you swapped in a lightweight flywheel and lightweight underdrive pulley, the system would not overrev the engine. It will back off once the target RPM is reached.

PS. I'm not an expert.

Source? Clutch pedal switch is not used.

juld0zer · 11-11-2013, 07:36 PM

Nissan's SynchroRev Match System Explained - The Heel and Toe Robot

I guess the easy way to test would be to disconnect the lower clutch pedal sensor and go for a drive.
The upper sensor tells the cruise control to cut.

I might be wrong about which of the two sensors but in theory, it should be the lower one.

MoulaZ · 01-22-2014, 07:59 AM

Have used the JWT 16lb Flywheel, and the Southbend DXD Race 19lb Flywheel. Currently still have the latter installed.

If anything, I'd say Synchro-Rev performance actually improved, the most with the JWT. It was easier to trick with the Stock Flywheel. And it's actually easier now to bounce between gears, up or down with the lighter Flywheel. The VQ37VHR itself is incredibly responsive and 'zippy', but just due to it's high level of NVH, Nissan chose to just dampen the heeeell out of it with a 32lb Dual-Mass Flywheel.

Downside to going Single-Mass Flywheels though still exist, the horrible chatter at idle in neutral (can largely be combated with thicker Gearbox Oil, and the reason I swapped out from the JWT to the DXD), slight rattle on standstill take-off (you'll learn to very slightly adjust how you take-off), and difficulty taking off uphill without adding to Clutch-riding.

JWT Install, when I first drove it home and first learned of this 'cement mixer' noise:
370Z Gearbox/Transmission Rattle Noise - YouTube

Still on JWT at this point, but I learned that thicker Gearbox Oil could help. I went with full Redline MT-90 and got this:
370Z Gearbox/Transmission Rattle Noise Improvement (Cold Start) - YouTube
However, be warned, thicker Oil does take a toll on shifting ability. Expect to use significantly more force to select gears for a couple of minutes on cold starts.

MoulaZ

esfourteen · 01-22-2014, 10:39 AM

Quote:

Originally Posted by juld0zer

Thread revival!

...

i'd assume if you swapped in a lightweight flywheel and lightweight underdrive pulley, the system would not overrev the engine. It will back off once the target RPM is reached.

PS. I'm not an expert.

I'm not sure why this thread got bumped to speculate, we already know for a fact that flywheel and pulley does not affect SRM. the only thing that affects SRM is final drive ratio (and transmission ratios if one were to actually change those out). ecutek has a mechanism to adjust the SRM offset, uprev currently does not.

/endthread

01-22-2014, 07:59 AM	#4 (permalink)
MoulaZ Base Member Join Date: Jun 2013 Location: Sydney, Australia Posts: 230 Drives: '09 Z34 BP Turbo V2 Rep Power: 26	Have used the JWT 16lb Flywheel, and the Southbend DXD Race 19lb Flywheel. Currently still have the latter installed. If anything, I'd say Synchro-Rev performance actually improved, the most with the JWT. It was easier to trick with the Stock Flywheel. And it's actually easier now to bounce between gears, up or down with the lighter Flywheel. The VQ37VHR itself is incredibly responsive and 'zippy', but just due to it's high level of NVH, Nissan chose to just dampen the heeeell out of it with a 32lb Dual-Mass Flywheel. Downside to going Single-Mass Flywheels though still exist, the horrible chatter at idle in neutral (can largely be combated with thicker Gearbox Oil, and the reason I swapped out from the JWT to the DXD), slight rattle on standstill take-off (you'll learn to very slightly adjust how you take-off), and difficulty taking off uphill without adding to Clutch-riding. JWT Install, when I first drove it home and first learned of this 'cement mixer' noise: 370Z Gearbox/Transmission Rattle Noise - YouTube Still on JWT at this point, but I learned that thicker Gearbox Oil could help. I went with full Redline MT-90 and got this: 370Z Gearbox/Transmission Rattle Noise Improvement (Cold Start) - YouTube However, be warned, thicker Oil does take a toll on shifting ability. Expect to use significantly more force to select gears for a couple of minutes on cold starts. MoulaZ SOUTH-BRONX likes this. Last edited by MoulaZ; 01-22-2014 at 08:04 AM.

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11-11-2013, 07:36 PM	#3 (permalink)
juld0zer Enthusiast Member Join Date: Nov 2012 Location: Sydney Posts: 428 Drives: 11 Nissan 370Z MB M6 Rep Power: 139	Nissan's SynchroRev Match System Explained - The Heel and Toe Robot I guess the easy way to test would be to disconnect the lower clutch pedal sensor and go for a drive. The upper sensor tells the cruise control to cut. I might be wrong about which of the two sensors but in theory, it should be the lower one.