Why Did My Z, Keep Revving? Video.

370Zsteve · 02-05-2010, 12:59 PM

Quote:

Originally Posted by semtex

My SRM works just like Modshack's. It doesn't blip until I push it into a lower gear. And that is exactly how I want it. But you know, this does explain something to me. Sometimes I read car mag writeups and they talk about how cool it is to make the throttle blip while they're waiting at a light by moving the shifter around in neutral. I always wondered what they were smoking and just chalked it up to ignorant journalists talking out of their proverbial a$$e$. Well now I know differently. So here's what I don't get. Say you're in 4th gear, you move the shifter into neutral and it immediately blips. Well, how does it know your intent is to downshift to 3rd rather than upshift to 5th? This is why I say my SRM is working exactly the way I want it. I don't want it blipping until I've moved into the gate for a lower gear.

I wonder how many of the issues in the thread are caused by simple mis-shifts, I'll confess to having an unintended rev or three since I bought it. My learning curve on this car has been focused completely on dropping the urge to blip the throttle when downshifting and just shifting into a lower gear with the same motion as an upshift. My SRM works exactly the way I want it to, and it let's me know in no uncertain terms when I screw up.

spearfish25 · 02-05-2010, 01:07 PM

Quote:

Originally Posted by semtex

My SRM works just like Modshack's. It doesn't blip until I push it into a lower gear. And that is exactly how I want it. But you know, this does explain something to me. Sometimes I read car mag writeups and they talk about how cool it is to make the throttle blip while they're waiting at a light by moving the shifter around in neutral. I always wondered what they were smoking and just chalked it up to ignorant journalists talking out of their proverbial a$$e$. Well now I know differently. So here's what I don't get. Say you're in 4th gear, you move the shifter into neutral and it immediately blips. Well, how does it know your intent is to downshift to 3rd rather than upshift to 5th? This is why I say my SRM is working exactly the way I want it. I don't want it blipping until I've moved into the gate for a lower gear.

My experience with SRM is that it pre-blips and then does another final blip when you engage the gear, depending on where you are shifting. I think of the gates not only as individuals for each gear, but also based on pairs of gears with respect to the three neutral positions (between 1/2, 3/4, and 5/6).

Here:

1 3 5
|-|-|
2 4 6

If you're in 6 and go to neutral but keep the shift knob to the far right without passing into the middle neutral gate, you'll get a 5th gear blip. If you instead go from 6th to 'full' neutral between 3rd and 4th gears, you'll get a 4th gear blip as you pass from far right neutral into the middle neutral zone. If your next move is to 3rd gear, you'll get a second blip for the 3rd gear RPM. So, in my experience SRM looks not only at individual gear selection but also which neutral gate you're passing through. Passing a neutral gate gets a blip for the highest gear (2nd or 4th) that you can enter from that neutral position. To get a blip for the lower gear in that position, you have to commit to that gear (1st, 3rd, or 5th).

An attempt to answer the mystery of how SRM determines to blip or not blip from 4-3 vs 4-5. More conjecture along the three neutral zone gate theory: If you're in 4th, SRM may look for the 3rd gate to trip before blipping. So a shift from 4-5 won't blip as you never commit to 3rd. It seems SRM will blip under one of two conditions. Condition #1: a shift to a lower gear that crosses from one neutral gate to the next (neutral between 5/6 to between 3/4) which gets a blip for the highest gear of the neutral gate you are entering. Condition #2: a shift from a neutral gate INTO the lower gear of the neutral gate pair (5/6 neutral up into 5, 3/4 N up into 3, or 1/2 N up into 1).

ChrisSlicks · 02-05-2010, 01:13 PM

Quote:

Originally Posted by semtex

My SRM works just like Modshack's. It doesn't blip until I push it into a lower gear. And that is exactly how I want it. But you know, this does explain something to me. Sometimes I read car mag writeups and they talk about how cool it is to make the throttle blip while they're waiting at a light by moving the shifter around in neutral. I always wondered what they were smoking and just chalked it up to ignorant journalists talking out of their proverbial a$$e$. Well now I know differently. So here's what I don't get. Say you're in 4th gear, you move the shifter into neutral and it immediately blips. Well, how does it know your intent is to downshift to 3rd rather than upshift to 5th? This is why I say my SRM is working exactly the way I want it. I don't want it blipping until I've moved into the gate for a lower gear.

The SRM does nothing at all while you are waiting at a light. The SRM can only set the engine speed based on gear ratio, if vehicle speed or transmission speed is too low then SRM is disabled. e.g. If you are crawling along in 1st at 5 mph and then try to stick it in 6th SRM isn't going to try and match RPM's to 200 rpm and stall your car.

If you are in 4th gear and shift to neutral the rpm's won't blip any higher, they will hold at the 4th gear rpm until you either select 3rd or move to another neutral position lining up under a different gear pair. Likewise if you are in 6th and move to the neutral position above 6th it will hold the current rpm until you move the shifter to the neutral position above 4th, at which time it will blip to match 4th gear, and blip higher still if you move to 3rd gear.

With all of these movements if you leave the shifter position still for about 1500-2000ms with the clutch in then the rpm's will drop to idle (or whatever your right foot is otherwise commanding).

semtex · 02-05-2010, 01:19 PM

Quote:

Originally Posted by ChrisSlicks

The SRM does nothing at all while you are waiting at a light. The SRM can only set the engine speed based on gear ratio, if vehicle speed or transmission speed is too low then SRM is disabled. e.g. If you are crawling along in 1st at 5 mph and then try to stick it in 6th SRM isn't going to try and match RPM's to 200 rpm and stall your car.

Okay, so I was right about automotive journalists being morons. Go figure, right?

On a more serious note though, I'm slightly confused about your last sentence about going from 1st to 6th. You say that SRM isn't going to try to match the RPMs to 200 rpm and stall your car. Well, doesn't that go without saying? SRM only blips on downshifts, not upshifts. Right? Or have we just uncovered yet another behavior of SRM that applies to some Zs and not others???

ChrisSlicks · 02-05-2010, 01:20 PM

Quote:

Originally Posted by spearfish25

I can't answer your question about how SRM distinguishes between 4-3 vs 4-5 and blipping vs not blipping. All I know is that anytime I'm slowing down and shift to neutral, I'll get a blip. Any time I'm accelerating and upshifting, it doesn't blip. Just SRM magic?

For up-shifts it doesn't blip because you don't pass through the neutral zone of a lower gear. You are either staying in the same neutral zone (3-4, 5-6 shift) or going through a higher neutral zone (2-3, 4-5).

m4a1mustang · 02-05-2010, 01:20 PM

Quote:

Originally Posted by semtex

Okay, so I was right about automotive journalists being morons. Go figure, right?

On a more serious note though, I'm slightly confused about your last sentence about going from 1st to 6th. You say that SRM isn't going to try to match the RPMs to 200 rpm and stall your car. Well, doesn't that go without saying? SRM only blips on downshifts, not upshifts. Right? Or have we just uncovered yet another behavior of SRM that applies to some Zs and not others???

SRM will blip on an upshift if you take too long and let the revs drop too low for the next gear.

ChrisSlicks · 02-05-2010, 01:23 PM

Quote:

Originally Posted by semtex

Okay, so I was right about automotive journalists being morons. Go figure, right?

On a more serious note though, I'm slightly confused about your last sentence about going from 1st to 6th. You say that SRM isn't going to try to match the RPMs to 200 rpm and stall your car. Well, doesn't that go without saying? SRM only blips on downshifts, not upshifts. Right? Or have we just uncovered yet another behavior of SRM that applies to some Zs and not others???

SRM works on up-shifts as well. The term "blip" implies an increase in RPM and so you would only have that in a down-shift situation. On an up-shift the RPM's are held where they are and then lowered to match the target gear (negative blip).

Modshack · 02-05-2010, 01:50 PM

Meh...Whatever you guys find acceptable. I'm convinced mine is working perfectly as designed and described by Nissan. If you guys like all those blips and blurps with random stick movement that's great! If my car did that I'd turn the damn thing off....

semtex · 02-05-2010, 01:51 PM

Quote:

Originally Posted by m4a1mustang

SRM will blip on an upshift if you take too long and let the revs drop too low for the next gear.

This I've experienced.

Quote:

Originally Posted by ChrisSlicks

SRM works on up-shifts as well. The term "blip" implies an increase in RPM and so you would only have that in a down-shift situation. On an up-shift the RPM's are held where they are and then lowered to match the target gear (negative blip).

This I haven't. If anything, I think the rpms take too long to drop due to the heavy flywheel, making upshifts jerky if done too quickly. It would be nice if SRM would force the rpms down though, as that would mitigate my desire to buy a noisy lightweight flywheel. I put a JWT flywheel in my 350. I loved what it did to the performance in terms of taking away some of the 'rpm-float' during upshifts, but I hated the rattling noise it made.

m4a1mustang · 02-05-2010, 02:03 PM

Hmm, yeah, I can't say I've experienced it forcing the RPMs lower.

spearfish25 · 02-05-2010, 02:10 PM

It doesn't force the RPMs lower. Just drive along in 4th, make the move to 5th but keep your foot on the clutch with the gear lever engaged in 5th. SRM will keep the revs at the lower 5th gear RPM for you.

Modshack · 02-05-2010, 02:14 PM

Quote:

Originally Posted by m4a1mustang

Hmm, yeah, I can't say I've experienced it forcing the RPMs lower.

Obviously you don't shift at the speed of light...

semtex · 02-05-2010, 02:20 PM

Quote:

Originally Posted by spearfish25

It doesn't force the RPMs lower. Just drive along in 4th, make the move to 5th but keep your foot on the clutch with the gear lever engaged in 5th. SRM will keep the revs at the lower 5th gear RPM for you.

Right. It'll prevent the revs from dropping too low if you're really slow to let off the clutch for some reason.

ChrisSlicks · 02-05-2010, 02:29 PM

Quote:

Originally Posted by m4a1mustang

Hmm, yeah, I can't say I've experienced it forcing the RPMs lower.

Force is perhaps the wrong word, let's say it adjusts the RPM for the higher gear. It can't lower RPM's as quickly as it can raise them so it can overshoot a little on a quick shift.

TheWeatherman · 02-05-2010, 05:30 PM

Quote:

Originally Posted by semtex

Hey TW, instead of completely deleting your video on YouTube, I'm wondering if it'd be a good idea to re-post it under the heading 'Synchro Rev Match malfunction' or something like that. My thinking is that it could serve as a future reference for anyone who suspects they have a problem with their SRM. Your vid could be an example of a symptom of SRM going awry. Just a thought.

Yeah, that's a good idea. I'll try that when I have a little free time. I have to re-upload it. Good suggestion Semtex. Hey, by the way, I really didn't think of taking it out of SRM. Again, I'm not sure why. I think my mind was elsewhere restarting the car in the middle of two major intersections, not knowing if it would even start again and once it started, how was I going to release the clutch. I was in the busiest part of my parents' hometown. Hope ya understand. If I could do it again, I would've tried that in a heartbeat.

02-05-2010, 01:50 PM	#128 (permalink)
Modshack A True Z Fanatic Join Date: Mar 2009 Location: Greenville NC Posts: 2,883 Drives: 370Z Sport Rep Power: 976	Meh...Whatever you guys find acceptable. I'm convinced mine is working perfectly as designed and described by Nissan. If you guys like all those blips and blurps with random stick movement that's great! If my car did that I'd turn the damn thing off.... __________________ Steal my car! (SOLD)...Now Porsche Cayman S Oil Cooler DIY: Here!

02-05-2010, 02:03 PM	#130 (permalink)
m4a1mustang A True Z Fanatic Join Date: Feb 2009 Location: Northern VA Posts: 55,385 Drives: on two wheels Rep Power: 6962	Hmm, yeah, I can't say I've experienced it forcing the RPMs lower. __________________ - Steve Zs & Coffee - Saturdays at 10AM in Fairfax, VA and Columbia, MD (Click the banner!) LIKE us on Facebook!

02-05-2010, 02:10 PM	#131 (permalink)
spearfish25 A True Z Fanatic Join Date: Mar 2009 Location: Naples, FL Posts: 4,117 Drives: to work Rep Power: 1856	It doesn't force the RPMs lower. Just drive along in 4th, make the move to 5th but keep your foot on the clutch with the gear lever engaged in 5th. SRM will keep the revs at the lower 5th gear RPM for you. __________________ 2013 Cadillac V-Wagon, RIP Z

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