What we are saying is that we do not experience this. There is no terminology debate, engine braking simply does not exist. It feels like stock in the lower gears and there is almost a sort of push in the higher gears.

 

Taking your foot off the gas to decelerate should slow the car down faster w/ pulley/flywheel because of reduced rotational weight makes the drivetrain more responsive to gas and brake.

Engaging the clutch to decelerate should slow the engine down slower because of reduced rotational weight not being a burden on the motor. A more open exhaust has the same effect. When you downshift there is no longer a sudden lurch.

One way, the engine is already engaged and you are slowing down the car with the gearing and weight of the car. Its very close to 1:1 as the rotational weight is reduced. So let off the gas and your car lurches slower as fast as it accelerates.

The other way, the clutch engagement is slowing down the engine which in turn has to slow down the car which is a lot harder for the engine to do. Weight of the car and slip of the clutch is added on the downshift, so it seems as if the downshift lurch abates as rotational weight is reduced.

Does that make any sense? I've experienced both with my car. I agree with HFM and FLyby that when I downshift the car seems to breathe easier and not reduce the speed of my car. But my throttle is more responsive in the on and off position.

 

One other interesting thing I noticed when on the freeway today. At 80 mph in 6th gear on level road, my engine speed used to be about 3,100 RPM. Today, I noticed after the installation, at 80 mph in 6th gear on level road, my engine speed is 2,900 RPM. It's almost like the UR pulley freed up 200 RPM.

 

guys i didn't read all the posts but the reason that his revs are jumping when presses the clutch is because the pregrammed throttle input for idle is too much for the lightened load, take you car to a dealer hand have them tune your idle back to where it was with the stock intake, if you do this your engine braking will be awsome. peac out and hope you read this.

 

Ooohhh. Hey, that makes sense. When you are engine braking, pressing the throttle pedal even a tiny, tiny bit will completely remove your engine braking. So what you're saying would completely explain what folks like HFM are experiencing. I would wonder, though, why Jason@Performance (and Raceboy from a while back, I believe) are seeing increased braking, not less. Maybe they adjusted their throttle settings?

 

Not possible. There is a direct mechanical connection from your engine to your rear wheel contact patches, so a given RPM in a given gear will always result in the same speed. Did you change rear wheels/tires?

With engine RPM, gear ratios, and tire size you can calculate speed.

 

Interesting. Well, it's the first day of freeway driving so I'll have to look closely again later. But, from recollection 80 mph, 6th equalled 3050 to 3100 rpm. I noticed it at 2900 rpm under the same conditions today after installation of the UR Pulley on Saturday.

But, I know you're mechanically/race inclined so your thoughts are appreciated. Let me know if you have any ideas on this. No I didn't changes the wheels/tires. I did change the springs a couple weekends ago. I don't know if that would have made any difference.

 

I don't want to hijack the discussion on the flywheel braking. But I want to add to Doh's rotating inertia comments on the "perceived" power gain with the lighter flywheels and pulleys. His explanation is right on. What that means is that you won't see this "perceived" gain on the dyno, at least at the peak power point. You may see it in the lower part of the curve if you accelerate up the rpm range fast enough. You will, however, definitely see it in your road driving accelerations.

 

I have to agree with the others on this that were confused about reduced "engine braking". D'oh explained it perfectly and I understand where the differing trains of thoughts are coming from, correct in their own right. I hadn't even contemplated method #1. jreiter's terming it "flywheel braking" certainly sounds most correct.

For those of you who regularly downshift w/o rev-match (method #1), have you experienced momentary loss of traction, especially in a turn when doing such a shift? I'd also be concerned for the added wear and tear if this is regularly done.

 

I've always rev-matched when I downshift so the only "engine braking" I've been thinking of is getting just off the gas. Could someone please tell me the reasons why not to rev-match other than for not using your brakes?

 

The only plausible explanation, since no one is actually downshifting without revmatching in this situation, is the one set forth by adanande. He has started a new thread for it and I am waiting on a response from him. Hopefully his two posts were not hit and runs....

 

hfm stated he does downshift this way:

 

Oh you're right. I thought he said the opposite. Oops. I still think the other theory is valid if the guy would come back and justify.

 

Dan,

Simple... let me know when you're around the west valley again, and we'll swap cars again and we'll see how they react.

You know I have the JWT with the Nismo clutch, we should easily be able confirm the engine braking affect.

 

Ok, let me interject here and mention what I notice with my setup...

I installed U/R Pulleys and noticed absolutely no difference in power whatsoever. They sure look pretty though!

The next thing I installed was the KINETIX Plenum and HEY!!! Where did all the engine braking go?? Between those 2 mods, I have almost no engine braking anymore. My RPMs will linger at whatever speed it's currently at when I upshift (i.e 2nd to 3rd) whereas before the pulleys or Plenum it would drop a bit. I normally rev-match when I decel and the engine braking is signifigantly less there too.

If I am driving on a long straight piece of road, for example, and I take my foot off the gas the car just keeps on going as if I still had my foot on the gas. The decelleration is barely noticible at times. I honestly don't know why the plenum has anything to do with it, but I didn't notice this until immediately after installing it.

-Chris

 

Take a look at adanande's post up above. That really sounds like a plausible explanation, and I can see how your plenum situation would apply, too. If anyone has an OBDII scan tool, I imagine this could be done yourself if you know what settings to change.

 

Here is the separate post Adanande made regarding the idle setting:

https://my350z.com/forum/showthread....threadid=66480

 

Engine braking has nothing to do with shifting. Get to a certain RPM and let off of the throttle. That is engine braking. A lighter flywheel will cause the engine to have increased engine braking because there is less mass to keep the engine spinning.

By adding shifting to the equation, you are now dealing with the drive by wire system and how quick it releases the throttle back to idle.

 

I have some physics people working on this.

I'll give you whatever I get.

 

Well... that's kinda what I was getting at in my previous post. If I am driving and just let off the accellerator pedal the car keeps going as if I still had a little pressure still applied to the pedal. It ever so slightly will decrease it's momentum over a looooooooong time. It doesn't feel like the engine is slowing down the car nearly as much as before swapping out the pulleys and plenum.

-Chris