Lightweight flywheels and SyncroRev Match

semtex · 02-01-2009, 04:16 PM

I've been driving around this weekend with SynchroRev turned off (as I do like to heel & toe just for the pleasure of it) and I got to thinking that the 370 could use a lighter flywheel. But then I started to wonder -- how exactly does SynchroRev work? More specifically, is the weight of the stock flywheel programmed into the computer algorithm that determines how much to blip the throttle in order to achieve the correct revs? If so, then won't getting a significantly lighter flywheel screw up SyncroRev Match? Because any given amount of throttle will rev a lighter flywheel higher than a heavy one. Any thoughts? Anyone understand the technical intricacies of how SynchroRev Match works?

M.Bonanni · 02-01-2009, 04:43 PM

You are absolutely correct. I am curious myself to see what happens. It all depends on what parameters are actually read by the system and which are calculated.

RCZ · 02-01-2009, 04:59 PM

Quote:

Originally Posted by semtex

I've been driving around this weekend with SynchroRev turned off (as I do like to heel & toe just for the pleasure of it) and I got to thinking that the 370 could use a lighter flywheel. But then I started to wonder -- how exactly does SynchroRev work? More specifically, is the weight of the stock flywheel programmed into the computer algorithm that determines how much to blip the throttle in order to achieve the correct revs? If so, then won't getting a significantly lighter flywheel screw up SyncroRev Match? Because any given amount of throttle will rev a lighter flywheel higher than a heavy one. Any thoughts? Anyone understand the technical intricacies of how SynchroRev Match works?

Its very funny that you put this thread up. I mentioned this to DDM earlier in a PM. I thought about the same thing you did, however I had a different take on it. I have no technical information about this, but if you ask me... 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"

Crash · 02-01-2009, 05:11 PM

There is another thread about this on this board. I'd bet my money that the light-flywheel will NOT screw up the rev matching. The rev-matching is done by realtime math calculations, not a predefined table of speeds.

semtex · 02-01-2009, 05:12 PM

^^ I hope that's how it works! It would be awesome if that's how it works. Even quicker blips? Oh yeah, I'd be all over that!

Crash · 02-01-2009, 05:18 PM

Nissan would be crazy to use a static table for that. If one motor is even slightly off from what the factory specs are (which is VERY common) then there would be endless issues with the system. The only way to achieve what they have is to use real-time calculations.

RCZ · 02-01-2009, 05:41 PM

Quote:

Originally Posted by Crash

Nissan would be crazy to use a static table for that. If one motor is even slightly off from what the factory specs are (which is VERY common) then there would be endless issues with the system. The only way to achieve what they have is to use real-time calculations.

+1 we agree.

rbratton · 02-03-2009, 10:29 AM

I'm sure they have a feedback loop in the control system that operates the rev-matching. IMO, changing the flywheel would not cause any issues.

Crash · 02-05-2009, 06:28 AM

Agreed. The resolution on the RPM sensors are so high now that they don't need even a quarter of a rotation to detect the RPM. The computers are fast enough to control the motor's fuel and air to some serious precision. It's actually very impressive. Something as clumsy as a combustion engine with less than predictable fuels and explosions can be controlled with such automation... Very cool technology.

juld0zer · 11-10-2013, 07:44 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.

Riptide67 · 11-10-2013, 07:50 PM

Well I know for a fact that a UD pulley that is lighter than factory does not mess with the SyncroRev. I'd be willing to wager that a lighter flywheel would not cause issues either.

Chuck33079 · 11-10-2013, 08:16 PM

Quote:

Originally Posted by Riptide67

Well I know for a fact that a UD pulley that is lighter than factory does not mess with the SyncroRev. I'd be willing to wager that a lighter flywheel would not cause issues either.

It doesn't.

takjak2 · 11-11-2013, 08:23 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, 08:36 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, 08:59 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

02-01-2009, 04:16 PM	#1 (permalink)
semtex A True Z Fanatic Join Date: Jan 2009 Location: Behind enemy lines Age: 54 Posts: 5,995 Drives: People to drink Rep Power: 32	Lightweight flywheels and SyncroRev Match I've been driving around this weekend with SynchroRev turned off (as I do like to heel & toe just for the pleasure of it) and I got to thinking that the 370 could use a lighter flywheel. But then I started to wonder -- how exactly does SynchroRev work? More specifically, is the weight of the stock flywheel programmed into the computer algorithm that determines how much to blip the throttle in order to achieve the correct revs? If so, then won't getting a significantly lighter flywheel screw up SyncroRev Match? Because any given amount of throttle will rev a lighter flywheel higher than a heavy one. Any thoughts? Anyone understand the technical intricacies of how SynchroRev Match works? __________________ "There are no small accidents on this circuit." -- Ayrton Senna 316.8whp & 248 ft/lbs (Dyno Dynamics) \| 319whp & 256 ft/lbs (DynoJet) (04/23/10) Stillen G3 CAI, CBE, Pulley / F.I. LTH / GTSpec Ladder Brace / Setrab Oil Cooler / UpRev-tuned by Forged Perf.

02-01-2009, 04:43 PM	#2 (permalink)
M.Bonanni The370Z.com Sponsor Join Date: Nov 2008 Location: Las Vegas Posts: 2,575 Drives: Fast Rep Power: 1321	You are absolutely correct. I am curious myself to see what happens. It all depends on what parameters are actually read by the system and which are calculated. __________________ MikeBonanni.com Twitter: http://www.twitter.com/MikeBonanni Facebook: http://www.facebook.com/MBonanni36 Function > Form

02-01-2009, 05:11 PM	#4 (permalink)
Crash A True Z Fanatic Join Date: Dec 2008 Location: Los Angeles Posts: 1,853 Drives: 02 Corvette Z06 Rep Power: 589	There is another thread about this on this board. I'd bet my money that the light-flywheel will NOT screw up the rev matching. The rev-matching is done by realtime math calculations, not a predefined table of speeds. aesthetk1 likes this. __________________ 2002 Corvette Z06 - Totaled 2003 Corvette Z06 50th Anniversary

02-01-2009, 05:12 PM	#5 (permalink)
semtex A True Z Fanatic Join Date: Jan 2009 Location: Behind enemy lines Age: 54 Posts: 5,995 Drives: People to drink Rep Power: 32	^^ I hope that's how it works! It would be awesome if that's how it works. Even quicker blips? Oh yeah, I'd be all over that! javi370z likes this. __________________ "There are no small accidents on this circuit." -- Ayrton Senna 316.8whp & 248 ft/lbs (Dyno Dynamics) \| 319whp & 256 ft/lbs (DynoJet) (04/23/10) Stillen G3 CAI, CBE, Pulley / F.I. LTH / GTSpec Ladder Brace / Setrab Oil Cooler / UpRev-tuned by Forged Perf.

02-01-2009, 05:18 PM	#6 (permalink)
Crash A True Z Fanatic Join Date: Dec 2008 Location: Los Angeles Posts: 1,853 Drives: 02 Corvette Z06 Rep Power: 589	Nissan would be crazy to use a static table for that. If one motor is even slightly off from what the factory specs are (which is VERY common) then there would be endless issues with the system. The only way to achieve what they have is to use real-time calculations. __________________ 2002 Corvette Z06 - Totaled 2003 Corvette Z06 50th Anniversary

02-03-2009, 10:29 AM	#8 (permalink)
rbratton Base Member Join Date: Jan 2009 Location: Vine Grove, KY Posts: 89 Drives: 2009 370Z Rep Power: 16	I'm sure they have a feedback loop in the control system that operates the rev-matching. IMO, changing the flywheel would not cause any issues.

02-05-2009, 06:28 AM	#9 (permalink)
Crash A True Z Fanatic Join Date: Dec 2008 Location: Los Angeles Posts: 1,853 Drives: 02 Corvette Z06 Rep Power: 589	Agreed. The resolution on the RPM sensors are so high now that they don't need even a quarter of a rotation to detect the RPM. The computers are fast enough to control the motor's fuel and air to some serious precision. It's actually very impressive. Something as clumsy as a combustion engine with less than predictable fuels and explosions can be controlled with such automation... Very cool technology. __________________ 2002 Corvette Z06 - Totaled 2003 Corvette Z06 50th Anniversary

11-10-2013, 07:50 PM	#11 (permalink)
Riptide67 A True Z Fanatic Join Date: Jul 2013 Location: Oak Harbor, WA Age: 37 Posts: 1,610 Drives: 09 Nismo #0483 PW Rep Power: 69	Well I know for a fact that a UD pulley that is lighter than factory does not mess with the SyncroRev. I'd be willing to wager that a lighter flywheel would not cause issues either. __________________ 2009 Nismo 370Z and 1975 Datsun 280Z 2+2 - PNW_INC - Legacy_Ohana Follow me on Instagam @s3zero_z3four

11-11-2013, 08:36 PM	#14 (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.

01-22-2014, 08:59 AM	#15 (permalink)
MoulaZ Base Member Join Date: Jun 2013 Location: Sydney, Australia Posts: 230 Drives: '09 Z34 BP Turbo V2 Rep Power: 25	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 09:04 AM.

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