Official Nissan 370Z Synchro Rev Match Transmission thread

[AutoX Z]

Originally Posted by Philipp

When lapping at the race track, I often hit the Rev-limiter will downshifting... Besides the "wheelhopping" effects, I do not understand why this will cause a blown engine???
Done this more than 300 times on my previous car without any engine issues... Is the Rev Matching disabling the engine cut-off sensors???

I think we're confusing down shifting with up shifting. 1-2 upshift, 2-1 downshift. Going from 2-1 it is possible to force the engine to over-rev because of the speed the wheels are turning. No amount of fuel cut will keep engine from exceeding the rev limit when there is a mechanical link to the wheels. That is a money shift and will definitely lead to major engine damage in some fashion.

[Philipp]

Originally Posted by AutoX Z

I think we're confusing down shifting with up shifting. 1-2 upshift, 2-1 downshift. Going from 2-1 it is possible to force the engine to over-rev because of the speed the wheels are turning. No amount of fuel cut will keep engine from exceeding the rev limit when there is a mechanical link to the wheels. That is a money shift and will definitely lead to major engine damage in some fashion.

AutoX
Sorry if i didn't translate properly my thinking... English isn't my first language.
Wheelhooping does occur under hard breaking when the rear of the car is going slower than the axle (due to brake compression on the wheels). It doesn't happen during acceleration...
Hope this clarify my comments. Also, hitting the rev-limiter is "NORMAL" when downshifting under braking before entering a tight corner/apex. This driving habit may also due to my rotary engine history where the power band was at high (very high) RPM levels.

[Modshack]

Originally Posted by Philipp

Also, hitting the rev-limiter is "NORMAL" when downshifting under braking before entering a tight corner/apex. This driving habit may also due to my rotary engine history where the power band was at high (very high) RPM levels.

It's not "Normal" unless you're downshifting too soon. Scrub off some speed with the brakes so your downshifts fall into the RPM range that the engine is happy with. Forcing an over-rev with gearing is a classic reason for Valve damage on the track. You could get away with it on the rotary because there are no valves to float. Downshifting, Wheel hopping and over-reving does not sound smooth at all. You can probably better your times if you get smoother... That, and you don't even want to know what it will cost to replace bent valves on a VVEL motor..

[!xoible]

Originally Posted by Philipp

AutoX
Sorry if i didn't translate properly my thinking... English isn't my first language.
Wheelhooping does occur under hard breaking when the rear of the car is going slower than the axle (due to brake compression on the wheels). It doesn't happen during acceleration...
Hope this clarify my comments. Also, hitting the rev-limiter is "NORMAL" when downshifting under braking before entering a tight corner/apex. This driving habit may also due to my rotary engine history where the power band was at high (very high) RPM levels.

actually wheelhopping is @ acceleration, burnouts, hardshifts 1-2, 2-3.

[Modshack]

Originally Posted by !xoible

actually wheelhopping is @ acceleration, burnouts, hardshifts 1-2, 2-3.

Actually it's very easy to do on deceleration too where engine braking exceeds tire traction. Since the rear wheels can't spin up due to engine drag they hop when they lose traction. High end performance motorcycles now employ "slipper clutches" that slip just enough to prevent this kind of thing, like an ABS for track deceleration..

[AutoX Z]

Originally Posted by Modshack

Actually it's very easy to do on deceleration too where engine braking exceeds tire traction. Since the rear wheels can't spin up due to engine drag they hop when they lose traction. High end performance motorcycles now employ "slipper clutches" that slip just enough to prevent this kind of thing, like an ABS for track deceleration..

I've seen it done on a solid axle firebird braking HARD with R-comps. The weight transfered to the front enough to severely unload the rear axle. This caused the rear brakes to lock and activate the abs. Everytime the wheels locked the axle jumped cause there was so little weight on it.

[kannibul]

FWIW, synchro-rev works on the 7AT, I noticed it today on both ends - downshift AND upshift.

[shabarivas]

synchro rev does not exist on the 7AT - you have a torque converter

[kannibul]

Originally Posted by shabarivas

synchro rev does not exist on the 7AT - you have a torque converter

LOL - ok, try again.

[Matt]

[370Zsteve]

Originally Posted by AutoX Z

I think we're confusing down shifting with up shifting. 1-2 upshift, 2-1 downshift. Going from 2-1 it is possible to force the engine to over-rev because of the speed the wheels are turning. No amount of fuel cut will keep engine from exceeding the rev limit when there is a mechanical link to the wheels. That is a money shift and will definitely lead to major engine damage in some fashion.

Not with the rev-limiter it won't. The damage you risk is to the clutch and the transmission.

[370Zsteve]

Originally Posted by Modshack

Actually it's very easy to do on deceleration too where engine braking exceeds tire traction. Since the rear wheels can't spin up due to engine drag they hop when they lose traction. High end performance motorcycles now employ "slipper clutches" that slip just enough to prevent this kind of thing, like an ABS for track deceleration..

and my MV Agusta goes a step further and uses what they call an Engine Braking System. No slipper clutch needed! Rather than me try to explain it , here's the official line:

The Magneti Marelli 5SM ECU manages the widely acknowledged EBS system (Engine Brake System) that is fitted to MV Agusta engines. The concept is based on a solenoid-activated by-pass valve on cylinder N° 2 intake duct. The by-pass is situated downstream from the feed throttle that has a suitably shaped air intake. This device allows cylinder N°2 to produce torque even under deceleration (when the feed throttles are closed) thanks to a signal sent by the Marelli ECU.

[Matt]

Be careful, Steve. This thread is like 9 months old, haha! Necro'd by a spammer.

[370Zsteve]

Originally Posted by Matt

Be careful, Steve. This thread is like 9 months old, haha! Necro'd by a spammer.

lmao I just saw it, reported

[SkyZ]

Prepping for race wars i see. Well u'll need 2 of the big bottles.

Originally Posted by Zlips

Nope...LOL I need NOS haha.